Name: whole-cell patch-clamp recordings of isolated primary epithelial cells from the epididymis
Uploaded: 2017-08-03T12:30:00
Description: Watch this Scientific Journal Video about Whole-cell Patch-clamp Recordings of Isolated Primary Epithelial Cells from the Epididymis at JoVE.com

We thank Dr. Christopher Antos for helpful comments on the text. This work was supported by start-up funding from ShanghaiTech University awarded to Winnie Shum and by the funding from the National Natural Science Foundation of China (NNSFC no. 31471370).

All animal experiments are carried out in accordance with the guidelines of the ShanghaiTech University Institutional Animal Care and Use Committee, which fulfill the local and international requirements.
1. Experimental Animals
<ol>
	<li>Use adult male Sprague-Dawley rats (~300-450 g) between 8-12 weeks old. At this age in the rats, the sperm have arrived in the cauda epididymides.</li>
</ol>
2. Isolation of Epithelial Cells from Rat Cauda Epididymides
<p class="jo...

<ol>
	<li>Shum, W. W. C., Ruan, Y. C., Da Silva, N., Breton, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+Cell-Cell+Cross+Talk+in+the+Epididymis:+Control+of+Luminal+Acidification.">Establishment of Cell-Cell Cross Talk in the Epididymis: Control of Luminal Acidification.</a> J Androl. 32 (6), 576-586 (2011).</li><li>Robaire, B., Hinton, B. T., Plant, T. M., Zeleznik, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Knobil and Neill's Physiology of Reproduction. , 691-771 (2015).</li><li>Da Silva, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dense+network+of+dendritic+cells+populates+the+murine+epididymis.">A dense network of dendritic cells populates the murine epididymis.</a> Reproduction. 141 (5), 653-663 (2011).</li><li>Kolb, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Special Issue on Ionic Channels II. , 51-91 (1990).</li><li>Clapham, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+Signaling.">Calcium Signaling.</a> Cell. 80 (2), 259-268 (1995).</li><li>Frizzell, R. A., Hanrahan, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiology+of+Epithelial+Chloride+and+Fluid+Secretion.">Physiology of Epithelial Chloride and Fluid Secretion.</a> Cold Spr Harb Pers Med. 2 (6), (2012).</li><li>Wong, P. Y. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CFTR+gene+and+male+fertility.">CFTR gene and male fertility.</a> Mol Hum Reprod. 4 (2), 107-110 (1998).</li><li>Shum, W. W. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transepithelial+Projections+from+Basal+Cells+Are+Luminal+Sensors+in+Pseudostratified+Epithelia.">Transepithelial Projections from Basal Cells Are Luminal Sensors in Pseudostratified Epithelia.</a> Cell. 135 (6), 1108-1117 (2008).</li><li>Gao, D. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coupling+of+TRPV6+and+TMEM16A+in+epithelial+principal+cells+of+the+rat+epididymis.">Coupling of TRPV6 and TMEM16A in epithelial principal cells of the rat epididymis.</a> J Gen Physiol. 148 (2), 161-182 (2016).</li><li>Huang, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophysiological+Studies+of+Anion+Secretion+in+Cultured+Human+Epididymal+Cells.">Electrophysiological Studies of Anion Secretion in Cultured Human Epididymal Cells.</a> J Physiol. 455, 455-469 (1992).</li><li>Chan, H. C., Fu, W. O., Chung, Y. W., Chan, P. S. F., Wong, P. Y. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Atp-Activated+Cation+Conductance+in+Human+Epididymal+Cells.">An Atp-Activated Cation Conductance in Human Epididymal Cells.</a> Biol Repro. 52 (3), 645-652 (1995).</li><li>Cheung, K. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-cell+interaction+underlies+formation+of+fluid+in+the+male+reproductive+tract+of+the+rat.">Cell-cell interaction underlies formation of fluid in the male reproductive tract of the rat.</a> J Gen Physiol. 125 (5), 443-454 (2005).</li><li>Pastor-Soler, N., Pietrement, C., Breton, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+acid/base+transporters+in+the+male+reproductive+tract+and+potential+consequences+of+their+malfunction.">Role of acid/base transporters in the male reproductive tract and potential consequences of their malfunction.</a> Physiol. 20, 417-428 (2005).</li><li>Evans, A. M., Osipenko, O. N., Haworth, S. G., Gurney, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resting+potentials+and+potassium+currents+during+development+of+pulmonary+artery+smooth+muscle+cells.">Resting potentials and potassium currents during development of pulmonary artery smooth muscle cells.</a> Ame J Physiol-Heart Circ Physiol. 275 (3), 887-899 (1998).</li><li>Golowasch, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+Capacitance+Measurements+Revisited:+Dependence+of+Capacitance+Value+on+Measurement+Method+in+Nonisopotential+Neurons.">Membrane Capacitance Measurements Revisited: Dependence of Capacitance Value on Measurement Method in Nonisopotential Neurons.</a> J Neurophysiol. 102 (4), 2161-2175 (2009).</li><li>Cole, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Membranes, Ions and Impulses. A Chapter of Classical Biophysics. , (1968).</li><li>Lo, C. M., Keese, C. R., Giaever, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impedance+analysis+of+MDCK+cells+measured+by+electric+cell-substrate+impedance+sensing.">Impedance analysis of MDCK cells measured by electric cell-substrate impedance sensing.</a> Biophys J. 69, 2800-2807 (1995).</li><li>Solsona, C., Innocenti, B., Fernandez, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+exocytotic+fusion+by+cell+inflation.">Regulation of exocytotic fusion by cell inflation.</a> Biophys J. 74 (2), 1061-1073 (1998).</li><li>Robinson, D. W., Cameron, W. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-dependent+changes+in+input+resistance+of+rat+hypoglossal+motoneurons+associated+with+whole-cell+recording.">Time-dependent changes in input resistance of rat hypoglossal motoneurons associated with whole-cell recording.</a> J Neurophysiol. 83 (5), 3160-3164 (2000).</li><li>Sontheimer, H., Boulton, A. A., Baker, G. B., Walz, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Neuro Methods: Patch-Clamp Applications and Protocols. , (1995).</li><li>Cheung, Y. M., Hwang, J. C., Wong, P. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epithelial+membrane+potentials+of+the+epididymis+in+rats+[proceedings].">Epithelial membrane potentials of the epididymis in rats [proceedings].</a> J Physiol. 263 (2), 280 (1976).</li><li>Lybaert, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=KATP+channel+subunits+are+expressed+in+the+epididymal+epithelium+in+several+mammalian+species.">KATP channel subunits are expressed in the epididymal epithelium in several mammalian species.</a> Biol Reprod. 79 (2), 253-261 (2008).</li></ol>

In this protocol, the enzymatic dispersion of the rat cauda epididymides consistently yielded healthy epithelial cells. The quality of the epididymal epithelial cells for the patch-clamp experiments is dependent on a few critical steps in the protocol. For instance, the centrifugation of the cell mixture at a low centrifugal force (30 x g) is important for removing the spermatozoa and the epididymal luminal content; the epididymal epithelial cells become unhealthy in the presence of the spermatozoa in the cell culture. I...

The epididymis in the male reproductive tract is an organ lined with a layer of mosaic epithelial cells. As in other epithelial tissues, the various cell types of the epididymal epithelium, including principal cells, clear cells, basal cells and cells from the immunological and lymphatic systems, work in a concerted manner to function as the barrier at the tubule frontline and as the supporting cells for sperm maturation and physiology1,2,3. Thus, these epithelial cells play an essential role in reproductive health.
Epithelial cells are generally regarded as non-excitable cells that are unable to generate all-or-none action potentials in response to depolarizing stimuli, due to a lack of voltage-gated Na+ or Ca2+ channels4,5. However, epithelial cells express unique sets of ion channels and transporters that regulate their specialized physiological roles, such as secretion and nutrient transportation6. Different epithelial cells therefore possess characteristic electrical properties. For example, the principal cells express the CFTR for fluid and chloride transportation and express the TRPV6 for calcium reabsorption, whereas the clear cells express the proton pump V-ATPase for luminal acidification1,7,8,9. Some transporters and ion channels that regulate the physiological features of the epididymal epithelial cells have been reported, but the functional properties of epididymal epithelial cells are largely not yet understood10,11,12,13.
Whole-cell patch-clamp recording is a well-established technique for examining the intrinsic properties of both excitable and non-excitable cells, and is particularly helpful for studying the functions of primarily dissociated cells in heterogeneous cell samples; the voltage-clamp is used for measuring the passive membrane properties and the ionic currents of single cells14,15. The passive membrane properties include input resistance and capacitance. The former parameter indicates the intrinsic membrane conductance, while the latter implies the surface area of the cell membrane (a phospholipid bilayer, where ion channels and transporters are located, that serves as a thin insulator separating extracellular and intracellular media). The membrane capacitance is directly proportional to the cell membrane&#39;s surface area. Together with the membrane resistance that is reflected by the input resistance, the membrane time constant, which indicates how fast the cell membrane potential responds to the flow of ion channel currents, can be determined. In this regard, by combining the current response characteristics from a series of voltage steps applied to the cells, the biophysical kinetics and properties of the cells are determined15,16,17,18.
In the present paper, we describe the procedures for isolating epithelial cells from the rat cauda epididymis and the steps for measuring the membrane properties of different cell types in the dissociated cell mixture using the whole-cell patch-clamp. We show that the epididymal principal cells exhibit distinct membrane electrophysiological properties and that the conductances can be readily identified from other cell types.

<table border="0" cellpadding="0" cellspacing="0" width="624">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Instrument of AXON system</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:149px;">Computer controlled amplifier</td>
			<td style="width:129px;">Molecular Devices - Axon</td>
			<td style="width:139px;">Multiclamp 700B patch-clamp amplifier</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Digital Acquisition system</td>
			<td style="width:129px;">Molecular Devices - Axon</td>
			<td style="width:139px;">Digidata 1550 converter</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Microscope</td>
			<td style="width:129px;">Olympus</td>
			<td style="width:139px;">BX-61WI</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Micromanipulator</td>
			<td style="width:129px;">Sutter Instruments</td>
			<td style="width:139px;">MPC-325</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Recording chamber and in-line Heater</td>
			<td style="width:129px;">Warner Instruments</td>
			<td style="width:139px;">TC-324C</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Instrument of HEKA system</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Patch Clamp amplifier</td>
			<td style="width:129px;">Harvard Bioscience - HEKA</td>
			<td style="width:139px;">EPC-10 USB double</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Microscope</td>
			<td style="width:129px;">Olympus</td>
			<td style="width:139px;">IX73</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Micromanipulator</td>
			<td style="width:129px;">Sutter Instruments</td>
			<td style="width:139px;">MPC-325</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Recording chamber and in-line Heater</td>
			<td style="width:129px;">Warner Instruments</td>
			<td style="width:139px;">TC-324C</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Other Instrument</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Micropipette Puller</td>
			<td style="width:129px;">Sutter Instrument&#160;</td>
			<td style="width:139px;">P-1000</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:149px;">Recording Chamber</td>
			<td style="width:129px;">Warner Instruments</td>
			<td style="width:139px;">RC-26G or homemade chamber</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:149px;">Borosilicate capillary glass with filament</td>
			<td style="width:129px;">Sutter Instrument / Harvard Apparatus</td>
			<td style="width:139px;">BF150-86-10</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Vibration isolation table</td>
			<td style="width:129px;">TMC&#160;</td>
			<td style="width:139px;">63544</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Digital Camare</td>
			<td style="width:129px;">HAMAMASTU</td>
			<td style="width:139px;">ORCA-Flash4.0 V2 C11440-22CU</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Reagents for isolation</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">RPMI 1640 medium</td>
			<td style="width:129px;">Gibco</td>
			<td style="width:139px;">22400089</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">Penicillin/Streptomycin</td>
			<td style="width:129px;">Gibca</td>
			<td style="width:139px;">15140112</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="21">
			<td height="43" style="height:43px;width:149px;">IMDM</td>
			<td style="width:129px;">ATCC&#160;</td>
			<td style="width:139px;">30-2005&#160;</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="43" style="height:43px;width:149px;">IMDM</td>
			<td height="22" style="height:22px;width:129px;">Gibco</td>
			<td style="width:139px;">C12440500BT</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Collagenase I</td>
			<td style="width:129px;">Sigma</td>
			<td style="width:139px;">C0130</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Collagenase II</td>
			<td style="width:129px;">Sigma</td>
			<td style="width:139px;">C6885</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:149px;">5-&#945;-dihydrotestosterone</td>
			<td style="width:129px;">Medchemexpress</td>
			<td style="width:139px;">HY-A0120</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Fetal bovine serum</td>
			<td style="width:129px;">capricorn</td>
			<td style="width:139px;">FBS-12A</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="106">
			<td height="106" style="height:106px;width:149px;">Micropipette internal solutions (K+-based solution) (pH 7.2, 280-295 mOsm)</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">KCl, 35mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900068</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:149px;">MgCl2 &#183; 6H2O, 2mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">M2393</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">EGTA, 0.1mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">E4378</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">HEPES, 10mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900477</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">K-gluconate, 100mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">P-1847</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Mg-ATP, 3mM</td>
			<td style="width:129px;">Sigma/Various</td>
			<td style="width:139px;">A9187</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="106">
			<td height="106" style="height:106px;width:149px;">The standard external recording physiological salt solution (PSS) (pH 7.4, 300-310 mOsm)</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">NaCl, 140mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900058</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">KCl, 4.7mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900068</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:149px;">CaCl2, 2.5mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900266</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:149px;">MgCl2 &#183; 6H2O, 1.2mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">M2393</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:149px;">NaH2PO4, 1.2mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900060</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">HEPES, 10mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900477</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">Glucose, 10mM</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900392</td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">For pH adjustment</td>
			<td style="width:129px;"></td>
			<td style="width:139px;"></td>
			<td style="width:207px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">NaOH</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">V900797</td>
			<td style="width:207px;">Purity &#62;=97%</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:149px;">KOH</td>
			<td style="width:129px;">Sigma/various</td>
			<td style="width:139px;">60371</td>
			<td style="width:207px;">Purity &#62;=99.99%</td>
		</tr>
	</tbody>
</table>

whole-cell patch-clamp recordings of isolated primary epithelial cells from the epididymis

The epididymis is an essential organ for sperm maturation and reproductive health. The epididymal epithelium consists of intricately connected cell types that are distinct not only in molecular and morphological features but also in physiological properties. These differences reflect their diverse functions, which together establish the necessary microenvironment for the post-testicular sperm development in the epididymal lumen. The understanding of the biophysical properties of the epididymal epithelial cells is critical for revealing their functions in sperm and reproductive health, under both physiological and pathophysiological conditions. While their functional properties have yet to be fully elucidated, the epididymal epithelial cells can be studied using the patch-clamp technique, a tool for measuring the cellular events and the membrane properties of single cells. Here, we describe the methods of cell isolation and whole-cell patch-clamp recording to measure the electrical properties of primary dissociated epithelial cells from the rat cauda epididymides.

The described enzymatic digestion procedure for the isolation of epithelial cells from the rat cauda epididymides is a modified protocol from our previous studies9,12. This method produces a mixture of single cells with over 90% viability and without surface blisters or swollen cell volume. The heterogeneous cell mixture consists mainly of principal cells, clear cells and basal cells, as we have described previously<sup class="xre...

Watch this Scientific Journal Video about Whole-cell Patch-clamp Recordings of Isolated Primary Epithelial Cells from the Epididymis at JoVE.com

Whole-cell Patch-clamp Recordings of Isolated Primary Epithelial Cells from the Epididymis

We present a protocol that combines cell isolation and whole-cell patch-clamp recording to measure the electrical properties of the primary dissociated epithelial cells from the rat cauda epididymides. This protocol allows for investigation of the functional properties of primary epididymal epithelial cells to further elucidate the physiological role of the epididymis.

The epididymis is an essential organ for sperm maturation and reproductive health. The epididymal epithelium consists of intricately connected cell types ...

The overall goal of this procedure is to isolate epithelial cells from the rat epididymis and to measure the electrical properties on these primarily dissociated cells using whole-cell patch-clamp method. This method can help answer key questions in the reproductive biology field, such as the function of epididymis, which is important for sperm maturation and inheritance of paternal traits. This technique allows the user to cauterize the electrical properties of isolated epididymal epithelial cells so that unknown physiological function of these cells can then be illustrated.Demonstrating the procedure will be Bao Li Zhang, a grad student from my laboratory. To begin the procedure, disinfect the dissection tools by immersion in 70%ethanol. Then, let them air-dry.Next, prepare the full IMDM. Afterward, create 50 ml aliquots in aseptic conditions, seal with Parafilm, and store at four degrees celsius. Following that, prepare a collagenous enzyme digestion solution by dissolving collagenase type I and collagenase type II in RPMI, resulting in one milligram per milliliter of each collagenase in the solution.Filter the solution through a 0.22 micrometer membrane. Then, mark it as collagenase solution, and keep the solution at room temperature until use. Next, adjust the volume of the enzyme solution based on the weight of the enzyme.The minimal volume required for both cauda epididymides from a single rat is two milliliters. To dissect the rat cauda epididymides, sacrifice the animal by either using sodium pentobarbital via IP injection or using an isoflurane chamber until the animal does not respond to tail pinching stimulation, followed by cervical dislocation. Afterward, disinfect the lower abdomen by wiping it with 70%ethanol.Gently push the two testes down to the lower abdomen and then open the lower abdomen near the scrotum. Subsequently, remove the epididymal fat and dissect out all the reproductive organs. Afterward, transfer them to the dish with RPMI.In a clean, airflow controlled working station, dissect out the cauda epididymides from the connective and fatty tissues and the epididymal capsule. Place one epididymis with 0.2 milliliters of collagenase solution in a 1.5 milliliter tube. To dissociate single cells from the cauda epididymides, cut the epididymides in the collagenase solution using fine scissors until the tissue becomes a paste-like fluid.Then, rinse the scissors gently with the rest of the enzyme solution in the tube. Following that, place the tube on a metal thermo-mixer for 30 minutes at 37 degrees celsius with a shaking speed of 1, 000 rpm. Then, centrifuge the enzyme tissue mixture at room temperature for three minutes.After that, decant the sticky supernatant that contains mostly the sperm. Next, resuspend the pellet in one milliliter of full IMDM to quench all the enzymatic activity. Subsequently, transfer the cell suspension to a 50 milliliter tube containing 49 milliliters of RPMI.Centrifuge the cell mixture and decant the supernatant. Resuspend the pellet in one milliliter of full IMDM with gentle trituration for at least five minutes to dissociate single cells from the enzymatic treated epididymal tissue mixture. Separate the epithelial cells from other cells under aseptic conditions, and culture the cell suspension on a 10 centimeter Petri dish containing full IMDM for at least eight hours or overnight in an incubator at 32 degrees celsius.The next morning, prepare the sterile cover slips by immersion in 100%alcohol. Air-dry and then dip them in a small amount of culture medium. Then, place the cover slips in six-centimeter culture dishes or in single wells of a 24-well plate.Now, harvest the dissociated epithelial cells by gently collecting the cell suspension from the Petri dish which consists mostly of epithelial cells. Centrifuge the cell suspension at 30 times G in room temperature for five minutes, and then decant the supernatant. Following that, resuspend the cell pellet in two milliliters of full IMDM.Seed 0.2 milliliters of the harvested cell suspension onto the center of each sterile cover slip. Let the cell suspension settle in the liquid droplet for at least 10 minutes to allow the cells to loosely adhere to the glass cover slips. Then, carefully add one milliliter of full IMDM at the edge of a six-centimeter dish or 0.3 milliliters of full IMDM to each well of a 24-well plate, without disturbing the cells.Keep the isolated single cells on cover slips in the incubator at 32 degrees celsius until the patch-clamp experiments. On the day of the patch-clamp experiment, thaw one aliquot of intracellular solution on ice and keep it chilled during the patch-clamp experiment to prevent degradation. Next, transfer the culturing epithelial cells on the glass cover slip to the recording chamber filled with standard PSS at room temperature.Carefully change the bathing PSS at least two times using a pipette before any patch-clamp experiments. To establish the whole-cell configuration, immerse the pipette into the bath solution at the highest speed of the micromanipulator. Find the pipette tip on the screen connected to the digital camera.Then, slow down the micromanipulator speed to the medium-high mode. Quickly check the micropipette resistance using the data acquisition interface command by applying a voltage step generated from the computer controlled amplifier. Change to a new micropipette if the resistance is significantly out of this range.And set the liquid junction potential between the pipette and bath solution to zero using the pipette offset command in the commander interface of the software. Monitor the resistance with the membrane test. If the resistance is larger than 500 megaohms, but smaller than one gigaohm, apply a negative potential to help form the gigaseal.In the meantime, compensate the transient capacitive current of the micropipette. At this moment, apply a 10 millivolt hyperpolarizing step from a holding potential of zero millivolts for the seal resistance determination. Immediately after achieving a successful whole-cell configuration, apply a 10 millivolts hyperpolarizing step from a holding potential of negative 60 millivolts.Switch the voltage mode to the zero current mode and perform a 10 second gap-free recording to measure the resting membrane potential of the cell. Afterward, quickly switch back to, and remain in, the voltage mode. Apply the voltage protocols according to the planned experiments and measure the current responses.Here are the examples of the epithelial cells isolated from the rat cauda epididymides before and after reharvest of overnight culture on the dish prior to the patch-clamp experiments. This figure shows the typical whole-cell currents recorded from single epididymal epithelial cells using a pulse-eliciting protocol. The dotted line indicated the zero current levels.Here is the current voltage relationship of the current responses measured at the indicated time points. These are the representative tracings of the resting membrane potential of the principal cells dialyzed with a pipette solution, either with ATP or without ATP. And this bar graph shows no significant difference between the initial resting membrane potential of plus ATP and minus ATP.The numbers in brackets within the bars indicate the number of tested cells from at least three animals. And here are the correlation analyses of the seal resistance and the input resistance of all the cells, or the principal cells only versus the resting potentials measured at the zero current clamp shortly after the whole-cell establishment and the current magnitudes measured at the hyperpolarizing step to negative 100 millivolts from holding potential. Once mastered, this technique can be done in nine hours if it is performed properly.While attempting this procedure, it's important to remember to stop the enzymatic digestion immediately during cell isolation steps. Otherwise, overdigestion may occur which may lead to difficult formation of gigaohm seal and failure of patch-clamp experiments. To maintain the health of the culture, it's important to spin down the enzymatically dissociated cell mixture in the low speed of 30 G for two to three minutes, and then decant the sticky supernatant which contains mostly sperm cells.Following these procedures, other methods such as live cell imaging and a one-cell culture techniques can be performed in order to answer additional questions, such as the resting membrane potential in naive epithelial cells might regulate the extracellular behavior under controlled conditions. This technique paves the way for researchers in the field of reproductive biology to explore the electrophysiological properties of epithelial cells of epididymis for the regulation of sperm maturation and paternal acquired traits inheritance. After watching this video, you should have good understanding on how to isolate epithelial cells from rat epididymis and how to measure the electrical properties on these cells using whole-cell patch-clamp method.

whole-cell-patch-clamp-recordings-isolated-primary-epithelial-cells

Research

JoVE Journal

Developmental Biology

Using Isolated Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High throughput Microplate Respiratory Measurements

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of mitochondrial function in this tissue has become more prevalent. Although many technologies and assays exist that measure mitochondrial respiratory pathways in a variety of cells, tissue and species, there is currently a void in the literature in regards to the compilation of these assays using isolated mitochondria from mouse skeletal muscle for use in microplate based technologies. Importantly, the use of microplate based respirometric assays is growing among mitochondrial biologists as it allows for high throughput measurements using minimal quantities of isolated mitochondria. Therefore, a collection of microplate based respirometric assays were developed that are able to assess mechanistic changes/adaptations in oxygen consumption in a commonly used animal model. The methods presented herein provide step-by-step instructions to perform these assays with an optimal amount of mitochondrial protein and reagents, and high precision as evidenced by the minimal variance across the dynamic range of each assay.

The methods presented provide step-by-step instructions for the performance of a collection of microplate based respirometric assays using isolated mitochondria from minimal quantities of mouse skeletal muscle. These assays are able to measure mechanistic changes/adaptations in mitochondrial oxygen consumption in a commonly used animal model.

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of ...

Primary Endodermal Epithelial Cell Culture from the Yolk Sac Membrane of Japanese Quail Embryos

We established an endodermal epithelial cell culture model (EEC) for studying the function of certain enzymes and proteins in mediating nutrient utilization by avian embryos during development. Fertilized Japanese quail eggs were incubated at 37 &#176;C for 5 days and then yolk sac membranes (YSM) were collected to establish the EEC culture system. We isolated the embryonic endoderm layer from YSM, and sliced the membrane into 2 - 3 mm pieces and partially digested with collagenase before seeding in 24-well culture plates. The EECs proliferate out of the tissue and are ready for cell culture studies. We found that the EECs had typical characteristics of YSM in vivo, for example, accumulation of lipid droplets, expression of sterol O-acyltransferase and lipoprotein lipase. The partial digestion treatment significantly increased the successful rate of EEC culture. Utilizing the EECs, we demonstrated that the expression of SOAT1 was regulated by the cAMP dependent protein kinase A related pathway. This primary Japanese quail EEC culture system is a useful tool to study embryonic lipid transportation and to clarify the role of genes involved in mediating nutrient utilization in YSM during avian embryonic development.

To study the mechanism of lipid utilization in yolk sac membranes during the late stages of avian embryonic development, we established a primary Japanese quail embryonic endodermal epithelial cell culture system.

We established an endodermal epithelial cell culture model (EEC) for studying the function of certain enzymes and proteins in mediating nutrient ...

Cultivate Primary Nasal Epithelial Cells from Children and Reprogram into Induced Pluripotent Stem Cells

Nasal epithelial cells (NECs) are the part of the airways that respond to air pollutants and are the first cells infected with respiratory viruses. They are also involved in many airway diseases through their innate immune response and interaction with immune and airway stromal cells. NECs are of particular interest for studies in children due to their accessibility during clinical visits. Human induced pluripotent stem cells (iPSCs) have been generated from multiple cell types and are a powerful tool for modeling human development and disease, as well as for their potential applications in regenerative medicine. This is the first protocol to lay out methods for successful generation of iPSCs from NECs derived from pediatric participants for research purposes. It describes how to obtain nasal epithelial cells from children, how to generate primary NEC cultures from these samples, and how to reprogram primary NECs into well-characterized iPSCs. Nasal mucosa samples are useful in epidemiological studies related to the effects of air pollution in children, and provide an important tool for studying airway disease. Primary nasal cells and iPSCs derived from them can be a tool for providing unlimited material for patient-specific research in diverse areas of airway epithelial biology, including asthma and COPD research.

This publication demonstrates methods for successful sampling and culture of nasal epithelial mucosa from children, and reprogramming these cells to induced Pluripotent Stem Cells (iPSCs).

Nasal epithelial cells (NECs) are the part of the airways that respond to air pollutants and are the first cells infected with respiratory viruses. They ...

In Vitro Colony Assays for Characterizing Tri-potent Progenitor Cells Isolated from the Adult Murine Pancreas

Stem and progenitor cells from the adult pancreas could be a potential source of therapeutic beta-like cells for treating patients with type 1 diabetes. However, it is still unknown whether stem and progenitor cells exist in the adult pancreas. Research strategies using cre-lox lineage-tracing in adult mice have yielded results that either support or refute the idea that beta cells can be generated from the ducts, the presumed location where adult pancreatic progenitors may reside. These in vivo cre-lox lineage-tracing methods, however, cannot answer the questions of self-renewal and multi-lineage differentiation-two criteria necessary to define a stem cell. To begin addressing this technical gap, we devised 3-dimensional colony assays for pancreatic progenitors. Soon after our initial publication, other laboratories independently developed a similar, but not identical, method called the organoid assay. Compared to the organoid assay, our method employs methylcellulose, which forms viscous solutions that allow the inclusion of extracellular matrix proteins at low concentrations. The methylcellulose-containing assays permit easier detection and analyses of progenitor cells at the single-cell level, which are critical when progenitors constitute a small sub-population, as is the case for many adult organ stem cells. Together, results from several laboratories demonstrate in vitro self-renewal and multi-lineage differentiation of pancreatic progenitor-like cells from mice. The current protocols describe two methylcellulose-based colony assays to characterize mouse pancreatic progenitors; one contains a commercial preparation of murine extracellular matrix proteins and the other an artificial extracellular matrix protein known as a laminin hydrogel. The techniques shown here are 1) dissociation of the pancreas and sorting of CD133+Sox9/EGFP+ ductal cells from adult mice, 2) single cell manipulation of the sorted cells, 3) single colony analyses using microfluidic qRT-PCR and whole-mount immunostaining, and 4) dissociation of primary colonies into single-cell suspensions and re-plating into secondary colony assays to assess self-renewal or differentiation.

In Vitro Colony Assays for Characterizing Tri-potent Progenitor Cells Isolated from the Adult Murine Pancreas

In vitro colony assays to detect self-renewal and differentiation of progenitor cells isolated from adult murine pancreas are devised. In these assays, pancreatic progenitors give rise to cell colonies in 3-dimensional space in methylcellulose-containing semi-solid medium. Protocols for handling single cells and characterization of individual colonies are described.

Stem and progenitor cells from the adult pancreas could be a potential source of therapeutic beta-like cells for treating patients with type 1 diabetes. ...

Generation of Induced-pluripotent Stem Cells Using Fibroblast-like Synoviocytes Isolated from Joints of Rheumatoid Arthritis Patients

Mature somatic cells can be reversed into a pluripotent stem cell-like state using a defined set of reprogramming factors. Numerous studies have generated induced-Pluripotent Stem Cells (iPSCs) from various somatic cell types by transducing four Yamanaka transcription factors: Oct4, Sox2, Klf4 and c-Myc. The study of iPSCs remains at the cutting edge of biological and clinical research. In particular, patient-specific iPSCs can be used as a pioneering tool for the study of disease pathobiology, since iPSCs can be induced from the tissue of any individual. Rheumatoid arthritis (RA) is a chronic inflammatory disease, classified by the destruction of cartilage and bone structure in the joint. Synovial hyperplasia is one of the major reasons or symptoms that lead to these results in RA. Fibroblast-like Synoviocytes (FLSs) are the main component cells in the hyperplastic synovium. FLSs in the joint limitlessly proliferate, eventually invading the adjacent cartilage and bone. Currently, the hyperplastic synovium can be removed only by a surgical procedure. The removed synovium is used for RA research as a material that reflects the inflammatory condition of the joint. As a major player in the pathogenesis of RA, FLSs can be used as a material to generate and investigate the iPSCs of RA patients. In this study, we used the FLSs of a RA patient to generate iPSCs. Using a lentiviral system, we discovered that FLSs can generate RA patient-specific iPSC. The iPSCs generated from FLSs can be further used as a tool to study the pathophysiology of RA in the future.

Here we describe a protocol for generating human induced-pluripotent stem cells from patient-derived fibroblast-like synoviocytes, using a lentiviral system without feeder cells.

Mature somatic cells can be reversed into a pluripotent stem cell-like state using a defined set of reprogramming factors. Numerous studies have generated ...

Induction of Mesenchymal-Epithelial Transitions in Sarcoma Cells

Phenotypic plasticity refers to a phenomenon in which cells transiently gain traits of another lineage. During carcinoma progression, phenotypic plasticity drives invasion, dissemination and metastasis. Indeed, while most of the studies of phenotypic plasticity have been in the context of epithelial-derived carcinomas, it turns out sarcomas, which are mesenchymal in origin, also exhibit phenotypic plasticity, with a subset of sarcomas undergoing a phenomenon that resembles a mesenchymal-epithelial transition (MET). Here, we developed a method comprising the miR-200 family and grainyhead-like 2 (GRHL2) to mimic this MET-like phenomenon observed in sarcoma patient samples.We sequentially express GRHL2 and the miR-200 family using cell transduction and transfection, respectively, to better understand the molecular underpinnings of these phenotypic transitions in sarcoma cells. Sarcoma cells expressing miR-200s and GRHL2 demonstrated enhanced epithelial characteristics in cell morphology and alteration of epithelial and mesenchymal biomarkers. Future studies using these methods can be used to better understand the phenotypic consequences of MET-like processes on sarcoma cells, such as migration, invasion, metastatic propensity, and therapy resistance.

We present here a cell culture method for inducing mesenchymal-epithelial transitions (MET) in sarcoma cells based on combined ectopic expression of microRNA-200 family members and grainyhead-like 2 (GRHL2). This method is suitable for better understanding the biological impact of phenotypic plasticity on cancer aggressiveness and treatments.

Phenotypic plasticity refers to a phenomenon in which cells transiently gain traits of another lineage. During carcinoma progression, phenotypic ...

Rapid, Directed Differentiation of Retinal Pigment Epithelial Cells from Human Embryonic or Induced Pluripotent Stem Cells

We describe a robust method to direct the differentiation of pluripotent stem cells into retinal pigment epithelial cells (RPE). The purpose of providing a detailed and thorough protocol is to clearly demonstrate each step and to make this readily available to researchers in the field. This protocol results in a homogenous layer of RPE with minimal or no manual dissection needed. The method presented here has been shown to be effective for induced pluripotent stem cells (iPSC) and human embryonic stem cells. Additionally, we describe methods for cryopreservation of intermediate cell banks that allow long-term storage. RPE generated using this protocol might be useful for iPSC disease-in-a-dish modeling or clinical application.

This protocol describes how to produce retinal pigment epithelial cells (RPE) from pluripotent stem cells. The method uses a combination of growth factors and small molecules to direct the differentiation of stem cells into immature RPE in fourteen days and mature, functional RPE after three months.

We describe a robust method to direct the differentiation of pluripotent stem cells into retinal pigment epithelial cells (RPE). The purpose of providing ...

The Isolation and Culture of Primary Epicardial Cells Derived from Human Adult and Fetal Heart Specimens

The epicardium, an epithelial cell layer covering the myocardium, has an essential role during cardiac development, as well as in the repair response of the heart after ischemic injury. When activated, epicardial cells undergo a process known as epithelial to mesenchymal transition (EMT) to provide cells to the regenerating myocardium. Furthermore, the epicardium contributes via secretion of essential paracrine factors. To fully appreciate the regenerative potential of the epicardium, a human cell model is required. Here we outline a novel cell culture model to derive primary epicardial derived cells (EPDCs) from human adult and fetal cardiac tissue. To isolate EPDCs, the epicardium is dissected from the outside of the heart specimen and processed into a single cell suspension. Next, EPDCs are plated and cultured in EPDC medium containing the ALK 5-kinase inhibitor SB431542 to maintain their epithelial phenotype. EMT is induced by stimulation with TGF&#946;. This method enables, for the first time, the study of the process of human epicardial EMT in a controlled setting, and facilitates gaining more insight in the secretome of EPDCs that may aid heart regeneration. Furthermore, this uniform approach allows for direct comparison of human adult and fetal epicardial behavior.

The epicardium plays a crucial role in the development and repair of the heart by providing cells and growth factors to the myocardial wall. Here, we describe a method to culture human primary epicardial cells that enables the study and comparison of their developmental and adult characteristics.

The epicardium, an epithelial cell layer covering the myocardium, has an essential role during cardiac development, as well as in the repair response of ...

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and chromosome dynamics. While the germline is an excellent model, the analysis is often two dimensional due to the time and labor required for three-dimensional analysis. Major readouts in such studies are the number/position of nuclei and protein distribution within the germline. Here, we present a method to perform automated analysis of the germline using confocal microscopy and computational approaches to determine the number and position of nuclei in each region of the germline. Our method also analyzes germline protein distribution that enables the three-dimensional examination of protein expression in different genetic backgrounds. Further, our study shows variations in cytoskeletal architecture in distinct regions of the germline that may accommodate specific spatial developmental requirements. Finally, our method enables automated counting of the sperm in the spermatheca of each germline. Taken together, our method enables rapid and reproducible phenotypic analysis of the C. elegans germline.

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

We present an automated method for three-dimensional reconstruction of the Caenorhabditis elegans germline. Our method determines the number and position of each nucleus within the germline and analyses germline protein distribution and cytoskeletal structure.

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and ...

Induction and Validation of Cellular Senescence in Primary Human Cells

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a hallmark of various pathophysiological conditions including tumor suppression, tissue remodeling and aging. The inducers of cellular senescence in vivo are still poorly characterized. However, a number of stimuli can be used to promote cellular senescence ex vivo. Among them, most common senescence-inducers are replicative exhaustion, ionizing and non-ionizing radiation, genotoxic drugs, oxidative stress, and demethylating and acetylating agents. Here, we will provide detailed instructions on how to use these stimuli to induce fibroblasts into senescence. This protocol can easily be adapted for different types of primary cells and cell lines, including cancer cells. We also describe different methods for the validation of senescence induction. In particular, we focus on measuring the activity of the lysosomal enzyme Senescence-Associated &#946;-galactosidase (SA-&#946;-gal), the rate of DNA synthesis using 5-ethynyl-2&#39;-deoxyuridine (EdU) incorporation assay, the levels of expression of the cell cycle inhibitors p16 and p21, and the expression and secretion of members of the Senescence-Associated Secretory Phenotype (SASP). Finally, we provide example results and discuss further applications of these protocols.

Here, we discuss a series of protocols for induction and validation of cellular senescence in cultured cells. We focus on different senescence-inducing stimuli and describe the quantification of common senescence-associated markers. We provide technical details using fibroblasts as a model, but the protocols can be adapted to various cellular models.

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a ...