Name: real time in vivo tracking of thymocytes in the anterior chamber of the eye by laser scanning microscopy
Uploaded: 2018-10-02T13:30:00
Description: Watch this Scientific Journal Video about Real Time In Vivo Tracking of Thymocytes in the Anterior Chamber of the Eye by Laser Scanning Microscopy at JoVE.com

This work was supported by NIH grants R56DK084321 (AC), R01DK084321 (AC), R01DK111538 (AC), R01DK113093 (AC), and R21ES025673 (AC), and by the BEST/2015/043 grant (Conseller&#237;a de Educaci&#243;, cultura i esport, Generalitat valenciana, Valencia, Spain) (EO). Authors thank the SENT team at the Universidad Cat&#243;lica de Valencia San Vicente M&#225;rtir, Valencia, Spain and Alberto Hernandez at Centro de Investigaci&#243;n Pr&#237;ncipe Felipe, Valencia, Spain for their help with video filming and editing.

The Institutional Animal Care and Use Committee (IACUC) of the University of Miami approved all the experiments according to IACUC guidelines.
1. Isolation and Trimming of Newborn Thymi
<ol>
	<li>Prepare all reagents and instruments by autoclaving or other methods, ensuring sterile conditions.</li>
	<li>To minimize contaminations, perform all surgical procedures under a laminar flow hood.</li>
	<li>Prior to euthanizing donor mice, fill a 60 mm sterile dish with sterile prechilled 1x phosphat...

<ol>
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K., 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=The+impact+of+negative+selection+on+thymocyte+migration+in+the+medulla.">The impact of negative selection on thymocyte migration in the medulla.</a> Nature Immunology. 10, 823-830 (2009).</li><li>Sanos, S. L., Nowak, J., Fallet, M., Bajenoff, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stromal+cell+networks+regulate+thymocyte+migration+and+dendritic+cell+behavior+in+the+thymus.">Stromal cell networks regulate thymocyte migration and dendritic cell behavior in the thymus.</a> Journal of Immunology. 186, 2835-2841 (2011).</li><li>Witt, C. M., Raychaudhuri, S., Schaefer, B., Chakraborty, A. K., Robey, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+migration+of+positively+selected+thymocytes+visualized+in+real+time.">Directed migration of positively selected thymocytes visualized in real time.</a> PLoS Biology. 3 (6), e160 (2005).</li><li>Ramsdell, F., Z&#250;&#241;iga-Pfl&#252;cker, J. C., Takahama, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+systems+for+the+study+of+T+cell+development:+fetal+thymus+organ+culture+and+OP9-DL1+cell+coculture.">In vitro systems for the study of T cell development: fetal thymus organ culture and OP9-DL1 cell coculture.</a> Current Protocols in Immunology. , (2006).</li><li>White, A., Jenkinson, E., Anderson, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reaggregate+thymus+cultures.">Reaggregate thymus cultures.</a> Journal of Visualized Experiments. (18), e905 (2008).</li><li>Dunn, K. W., Sutton, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+studies+in+living+animals+using+multiphoton+microscopy.">Functional studies in living animals using multiphoton microscopy.</a> ILAR Journal. 49, 66-77 (2008).</li><li>Caetano, S. S., Teixeira, T., Tadokoro, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intravital+imaging+of+the+mouse+thymus+using+2-photon+Microscopy.">Intravital imaging of the mouse thymus using 2-photon Microscopy.</a> Journal of Visualized Experiments. (59), e3504 (2012).</li><li>Li, J., Iwanami, N., Hoa, V. Q., Furutani-Seiki, M., Takahama, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+intravital+imaging+of+thymocyte+dynamics+in+medaka.">Noninvasive intravital imaging of thymocyte dynamics in medaka.</a> Journal of Immunology. 179 (3), 1605-1615 (2007).</li><li>Adeghate, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host-graft+circulation+and+vascular+morphology+in+pancreatic+tissue+transplants+in+rats.">Host-graft circulation and vascular morphology in pancreatic tissue transplants in rats.</a> Anatomical Record. 251, 448-459 (1998).</li><li>Adeghate, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pancreatic+tissue+grafts+are+reinnervated+by+neuro-peptidergic+and+cholinergic+nerves+within+five+days+of+transplantation.">Pancreatic tissue grafts are reinnervated by neuro-peptidergic and cholinergic nerves within five days of transplantation.</a> Transplant Immunology. 10 (1), 73-80 (2002).</li><li>Speier, S., Nyqvist, D., K&#246;hler, M., Caicedo, A., Leibiger, I. B., Berggren, P. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+high-resolution+in+vivo+imaging+of+cell+biology+in+the+anterior+chamber+of+the+mouse+eye.">Noninvasive high-resolution in vivo imaging of cell biology in the anterior chamber of the mouse eye.</a> Nature Protocols. 3 (8), 1278-1286 (2008).</li><li>Speier, S., 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=Noninvasive+in+vivo+imaging+of+pancreatic+islet+cell+biology.">Noninvasive in vivo imaging of pancreatic islet cell biology.</a> Nature Medicine. 14 (5), 574-578 (2008).</li><li>Morillon, Y. M., Manzoor, F., Wang, B., Tisch, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+transplantation+of+different+aged+murine+thymic+grafts.">Isolation and transplantation of different aged murine thymic grafts.</a> Journal of Visualized Experiments. 99 (99), (2015).</li><li>Liu, L. L., Du, X. M., Wang, Z., Wu, B. J., Jin, M., Xin, B., 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+simplified+intrathymic+injection+technique+for+mice.">A simplified intrathymic injection technique for mice.</a> Biotechnic &amp; Histochemestry. 87 (2), 140-147 (2012).</li><li>Manna, S., Bhandoola, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrathymic+Injection.">Intrathymic Injection.</a> Methods in Molecular Biology. 1323, 203-209 (2016).</li><li>Abdulreda, M. 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Due to the importance of the T-cell maturation process for individual immune competency4 and the presumed impact of precursor cell dynamics on mature T-cells produced by the thymus2,3, extensive efforts have been invested to develop alternatives to the classical fixed tissue snapshot approach.
Although tissue slices and other explants are clearly superior in reproducing tissue architecture than monolayers or agg...

Intrathymic T-cell differentiation and T-cell subpopulation selection constitute key processes for the development and maintenance of cell-mediated immunity in vertebrates1. This process involves a complex sequence of tightly organized events including the recruitment of progenitors from bloodstream, cell proliferation and migration, differential expression of membrane proteins, and massive programmed cell death for subsets selection. The result is the release of mature T-cells reactive to an ample spectrum of foreign antigens while displaying minimized responses to self-peptides, which end-up colonizing the peripheral lymphoid organs of the individual2,3. Aberrant thymocyte selection of the &#945;&#946;TCR repertoire leads to autoimmune disease or immune imbalance4 that mainly derive from&#160;defects during the processes of negative or positive precursor selection, respectively.
Directional migration of thymocytes across the thymus is intrinsic to all stages of T-cell maturation and it is envisaged as a series of simultaneous, or sequential multiple stimuli, including chemokines, adhesive, and de-adhesive extracellular matrix (ECM) protein interactions3,5. The study of fixed tissues has rendered critical information regarding the patterns of expression for thymocyte migratory cues in defined thymic microenvironments5,6, while ex vivo studies has revealed two prevalent migratory behaviors of thymocytes in two histologically distinct areas of the organ: slow stochastic movements in the cortex and fast, confined motility in the medulla7,8,9,10,11,12,13. Increased migratory rates correlate with thymic positive selection13 and negative selection is associated with crawling behavior supporting the hypothesis that the kinetics of the journey through the thymus determines proper maturation of thymocytes. Despite their relevance, the topology of thymocyte-stromal cell interactions and the dynamics of thymocyte motility across organ microenvironments during T-cell maturation remain ill-defined.
Most ex vivo studies performed to date include fetal or reaggregate thymic organ cultures14,15, tissue slices or intact thymic lobe explants where thymocyte movements are visualized by two-photon laser scanning microscopy (TPLSM)8, an intravital imaging technique with a restricted maximum working distance and imaging depth of 1 mm in accordance with the tissue examined16. In contrast to the laborious thymic organ cultures which depend on extended incubation times to form 3D-structures, both, the thymic slice technique and the intact thymic lobe approach permit controlled introduction of particular subsets of pre-labeled thymocytes into a native tissue architecture environment. However, since blood flow is absent in these models, they are clearly limited for studying the recruitment process of thymus settling progenitors (TSPs) to the thymus parenchyma or the dynamics of thymic egression of mature T-cells.
In vivo models for the study of thymic T-cell maturation physiology in mice include the grafts of fragments or entire organ lobes placed either inside the kidney capsule17 or intradermally18. Although these options showed their utility to interrogate systemic functional engraftment of the tissue, the position of thymic grafts deep within the animal or covered by layers of opaque tissue restricts their use for in vivo examination of implants by TPLSM.
The anterior chamber of the eye provides an easily accessible space for direct monitoring of any grafted tissue by virtue of the transparency of corneal layers. Of advantage, the base of the chamber formed by the iris is rich in blood vessels and autonomic nerve endings, enabling rapid revascularization and reinnervation of the grafts19,20. Dr. Caicedo has successfully used this anatomical space for the maintenance and longitudinal study of pancreatic islets in the past21. Here, we show that this strategy not only constitutes a valid approach to study thymocytes&#39; dynamics within the native organ structure, but also uniquely permits to extend the in vivo longitudinal recordings to the study of progenitor recruitment and mature T-cell egression steps in mouse.

<table>
	<tbody>
		<tr>
			<td>Isofluorane vaporizer w/isofluorane</td>
			<td>Kent Scientific Corp</td>
			<td>VetFlo-1215</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting scope w/light source</td>
			<td>Zeiss</td>
			<td>Stemi 305</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine dissection forceps</td>
			<td>WPI</td>
			<td>500455</td>
			<td></td>
		</tr>
		<tr>
			<td>Medium dissection forceps</td>
			<td>WPI</td>
			<td>501252</td>
			<td></td>
		</tr>
		<tr>
			<td>Curved tip fine dissection forceps</td>
			<td>WPI</td>
			<td>15917</td>
			<td></td>
		</tr>
		<tr>
			<td>Vannas scissors</td>
			<td>WPI</td>
			<td>503371</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting scissors</td>
			<td>WPI</td>
			<td>503243</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>WPI</td>
			<td>500353</td>
			<td></td>
		</tr>
		<tr>
			<td>40 mm 18G needles</td>
			<td>BD</td>
			<td>304622</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable transfer pipette</td>
			<td>Thermofisher</td>
			<td>201C</td>
			<td></td>
		</tr>
		<tr>
			<td>Heat pad and heat lamp</td>
			<td>Kent Scientific Corp</td>
			<td>Infrarred</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 70%</td>
			<td>VWR</td>
			<td>83,813,360</td>
			<td></td>
		</tr>
		<tr>
			<td>60 mm sterile dish</td>
			<td>SIGMA</td>
			<td>CLS430166</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 1x PBS pH(7,4)</td>
			<td>Thermofisher</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile wipes</td>
			<td>Kimberly-Clark</td>
			<td>LD004</td>
			<td></td>
		</tr>
		<tr>
			<td>Drugs for pain management</td>
			<td>Sigma-Aldrich</td>
			<td>A3035-1VL</td>
			<td></td>
		</tr>
		<tr>
			<td>Saline solution or Viscotears</td>
			<td>Novartis</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Leica</td>
			<td>MZ FLIII</td>
			<td></td>
		</tr>
		<tr>
			<td>Head-holding adapter</td>
			<td>Narishige</td>
			<td>SG-4N-S</td>
			<td></td>
		</tr>
		<tr>
			<td>Gas mask</td>
			<td>Narishige</td>
			<td>GM-4_S</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Leica</td>
			<td>TCS SP5 II</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminar flow hood</td>
			<td>Telstar</td>
			<td>BIO IIA</td>
			<td></td>
		</tr>
	</tbody>
</table>

real time in vivo tracking of thymocytes in the anterior chamber of the eye by laser scanning microscopy

The purpose of the method being presented is to show, for the first time, the transplant of newborn thymi into the anterior eye chamber of isogenic adult mice for in vivo longitudinal real-time monitoring of thymocytes&#180; dynamics within a vascularized thymus segment. Following the transplantation, laser scanning microscopy (LSM) through the cornea allows in vivo noninvasive repeated imaging at cellular resolution level. Importantly, the approach adds to previous intravital T-cell maturation imaging models the possibility for continuous progenitor cell recruitment and mature T-cell egress recordings in the same animal. Additional advantages of the system are the transparency of the grafted area, permitting macroscopic rapid monitoring of the implanted tissue, and the accessibility to the implant allowing for localized in addition to systemic treatments. The main limitation being the volume of the tissue that fits in the reduced space of the eye chamber which demands for lobe trimming. Organ integrity is maximized by dissecting thymus lobes in patterns previously shown to be functional for mature T-cell production. The technique is potentially suited to interrogate a milieu of medically relevant questions related to thymus function that include autoimmunity, immunodeficiency and central tolerance; processes which remain mechanistically poorly defined. The fine dissection of mechanisms guiding thymocyte migration, differentiation and selection should lead to novel therapeutic strategies targeting developing T cells.

Thymus from newborn mice were isolated from B6.Cg-Tg(CAG-DsRed*MST)1Nagy/Jas mice as described in this protocol (Steps 1.1-1.9). In these transgenic mice, the chicken beta actin promoter directs the expression of the red fluorescent protein variant DsRed. MST under the influence of the cytomegalovirus (CMV) immediate early enhancer facilitating the tracking of implants.
To prevent tissue rejection, isogenic individuals ...

Watch this Scientific Journal Video about Real Time In Vivo Tracking of Thymocytes in the Anterior Chamber of the Eye by Laser Scanning Microscopy at JoVE.com

Real Time In Vivo Tracking of Thymocytes in the Anterior Chamber of the Eye by Laser Scanning Microscopy

The goal of the protocol is to show longitudinal intravital real-time tracking of thymocytes by laser scanning microscopy in thymic implants in the anterior chamber of the mouse eye. The transparency of the cornea and vascularization of the graft allows for continuously recording progenitor cell recruitment and mature T-cell egress.

Real Time In Vivo Tracking of Thymocytes in the Anterior Chamber of the Eye by Laser Scanning Microscopy

The purpose of the method being presented is to show, for the first time, the transplant of newborn thymi into the anterior eye chamber of isogenic adult ...

This method can help answer key questions in immunology field about the mechanisms of autoimmunity, immunodeficiency, central tolerance, and thymus involution. The main advantage of this technique is that it permits in vivo longitudinal recording of progenitor recruitment and mature T-cell egression within vascularized and grafted mouse thymus segments. Though this method can provide insight into the development and function of the thymus, can also be applied to other tissues such as pancreatic islets or kidney glomeruli.To isolate the thymus, place the mouse on sterile absorbent paper towels in the dorsal upright position in a laminar flow hood and spray and wipe the mouse abdomen with 70%ethanol. Make a superficial V-shaped incision in the lower abdomen to expose the thoracic cavity and use a pair of straight 10-centimeter dissecting scissors to make a 0.5 to one-centimeter incision in the chest along the ventral midline. Fold the skin over each side of the chest to expose the thoracic cavity and make two additional deeper 0.5 to one-centimeter lateral incisions through the diaphragm and rib cage to access the superior mediastinum in the anterior thoracic cavity.The thymus should appear as two pale lobes right above the heart. Place curved forcep-tips under the thymus and pull vertically to extract the complete organ, preventing the fold-back of the ribcage with a pair of straight forceps. Then submerge the isolated thymus in a sterile 60-milliliter dish containing cold sterile PBS on ice and use a scalpel to cut the connective isthmus to separate the thymic lobes.Before transplantation, tag and weigh each recipient mouse and place the first animal in a side lateral recumbent position with one eye directly exposed to the lens of a dissecting microscope. Using Vannas scissors, excise one of the isolated thymic lobes up to one millimeter in width following a zigzag pattern to ensure that each segment contains some thymic cortex and medulla tissue. It is critical to trim the thymus right before the implantation as large pieces may not engraft properly.Next, starting at the base of the cornea of the surgical area, use the tip of a 40-millimeter 18-gauge needle to make a small incision into external cornea layers so that the tip of a pair of dissecting scissors can be introduced. Use the scissors to make a five to 10-millimeter flank incision directly around the base of the cornea while using flat-ended forceps to firmly hold the cornea open to prevent resealing. Grasping the cut corneal epithelium with the flat-ended forceps, maintain the opening in the cornea while inserting a thymic segment through the opening.It is important to insert the thymus piece quickly through the corneal opening to prevent spontaneous resealing before the tissue's introduced. Be careful to preserve tissue integrity at this step. Press softly on the eye surface to slide the introduced tissue segment to a lateral position with respect to the pupil to preserve the function of the eye.And use flat forceps to press both sides of the corneal opening firmly against each other for three to five seconds to promote self-sealing. If the transplant is to be performed on both eyes, turn the mouse onto the opposite lateral side for a second implantation as just demonstrated. When the surgery is complete, return the mouse to an empty cage pre-warmed with a heat lamp with monitoring until full recumbency.At the appropriate experimental time point, place an anesthetized recipient mouse on a fixed-stage microscope platform in a side lateral recumbent position on a heat pad with one eye facing up. And insert the head of the mouse into a stereotaxic head holder. Adjust the knob to restrain the mouse head in the lateral side position to allow direct access of the microscope objective to the eye holding the thymus graft and pull back the eyelids while holding the eye at the corneal margin with a pair of tweezer-tips covered by a polyethylene tube attached to a UST-2 solid universal joint.Add a few drops of sterile saline or artificial tears between the cornea and the lens before placing the 5X microscope objective on the mouse eye and locate the thymus in the microscope field. Then switch to a higher resolution water immersion dipping objective with a long working distance and select the acquisition mode in the microscope software. Start the resonance scanner mode and select the XYZT imaging mode.Turn the argon laser on and adjust the power to 30%for fluorescence excitation. Select an appropriate excitation laser line and set the acousto-optical beam splitter control for the appropriate emission wavelengths using reflection detection simultaneously to detect backscatter and to delineate tissue structure. Collect the emission at the selected wavelength and set a 512-by-512 pixel resolution.Then click live to start the imaging, adjusting the gain levels as necessary. Focus on the top of the thymic implant and select begin to define the beginning of the Z stack. Then focus on the last plane in the implanted thymus that can be visualized and select end to define the end of the Z stack using a Z-step size of five micrometers.Set the time interval for the acquisition of each Z stack for 1.5 to two seconds and select the acquire-until-stopped option for continuous imaging. Then click start to initialize the recording. Here, bright-field and fluorescence images of the same area of the thymus implant that may serve for a double macroscopic followup of tissue growth and involution and continuation studies are shown.The bright-field image also facilitates visualization of the vascularization of the implanted tissue, allowing the unique study of the dependence of thymus physiology on blood supply over time. This model allows the visualization of cell transmigration from the blood torrent into the implanted thymus, the tracking of the contacts between GFP-positive progenitor cells entering the thymic implant with RFP-labeled resident thymic epithelial and stromal cells during differentiation and selection processes, as well as the monitoring of the egressive immune cells from the thymus into peripheral blood vessels. While attempting this procedure, it's important to remember to minimize tissue exposure for optimal engraftment and also to limit incision size in the eye to permit unharmed fragment excision through the cornea while reducing fibrosis during healing.Following this procedure, other methods like localized control treatments and incision of other tissues into the contralateral eye can be performed so as to answer additional questions about immune dysfunctions linked to infections, involution determinants, and transplantation tolerance mechanisms. After its development, this technique paved the way for researchers in the field of immunology to explore T-cell development, including progenitor recruitment, thymus-eye dynamics, and mature T-cell egression steps in vivo.

real-time-vivo-tracking-thymocytes-anterior-chamber-eye-laser

Research

JoVE Journal

Biology

In vivo Micro-circulation Measurement in Skeletal Muscle by Intra-vital Microscopy

BACKGROUND: Regulatory factors and detailed physiology of in vivo microcirculation have remained not fully clarified after many different modalities of imaging had invented. While many macroscopic parameters of blood flow reflect flow velocity, changes in blood flow velocity and red blood cell (RBC) flux does not hold linear relationship in the microscopic observations. There are reports of discrepancy between RBC velocity and RBC flux, RBC flux and plasma flow volume, and of spatial and temporal heterogeneity of flow regulation in the peripheral tissues in microscopic observations, a scientific basis for the requirement of more detailed studies in microcirculatory regulation using intravital microscopy. METHODS: We modified Jeff Lichtman's method of in vivo microscopic observation of mouse sternomastoid muscles. Mice are anesthetized,
ventilated, and injected with PKH26L-fluorescently labeled RBCs for microscopic observation.RESULT &amp; CONCLUSIONS: Fluorescently labeled RBCs are detected and distinguished well by a wide-field microscope. Muscle contraction evoked by electrical stimulation induced increase in RBC flux. Quantification of other parameters including RBC velocity and capillary density were feasible. Mice tolerated well the surgery, injection of stained RBCs, microscopic observation, and electrical stimulation. No muscle or blood vessel damage was observed, suggesting that our method is relatively less invasive and suited for long-term observations.

A new versatile method for observation of microcirculation is presented. It is considered suitable for long-term observation, and for combination with pharmacophysiological or molecular biological interventions.

BACKGROUND: Regulatory factors and detailed physiology of in vivo microcirculation have remained not fully clarified after many different modalities of ...

Time-lapse Microscopy of Early Embryogenesis in Caenorhabditis elegans

Caenorhabditis elegans has often been used as a model system in studies of early developmental processes. The transparency of the 
embryos, the genetic resources, and the relative ease of transformation are qualities that make C. elegans an excellent model for early embryogenesis. Laser-based 
confocal microscopy and fluorescently labeled tags allow researchers to follow specific cellular structures and proteins in the developing embryo. For example, 
one can follow specific organelles, such as lysosomes or mitochondria, using fluorescently labeled dyes. These dyes can be delivered to the early embryo by means 
of microinjection into the adult gonad. Also, the localization of specific proteins can be followed using fluorescent protein tags. Examples are presented here 
demonstrating the use of a fluorescent lysosomal dye as well as fluorescently tagged histone and ubiquitin proteins. The labeled histone is used to visualize 
the DNA and thus identify the stage of the cell cycle. GFP-tagged ubiquitin reveals the dynamics of ubiquitinated vesicles in the early embryo. Observations 
of labeled lysosomes and GFP:: ubiquitin can be used to determine if there is colocalization between ubiquitinated vesicles and lysosomes. A technique for 
the microinjection of the lysosomal dye is presented. Techniques for generating transgenenic strains are presented elsewhere (1, 2). For imaging, embryos 
are cut out of adult hermaphrodite nematodes and mounted onto 2% agarose pads followed by time-lapse microscopy on a standard laser scanning confocal 
microscope or a spinning disk confocal microscope. This methodology provides for the high resolution visualization of early embryogenesis.

Time-lapse Microscopy of Early Embryogenesis in Caenorhabditis elegans

This article describes a technique for the visualization of the early events of embryogenesis in the nematode Caenorhabditis elegans.

Caenorhabditis elegans has often been used as a model system in studies of early developmental processes.  The transparency of the 
embryos, the genetic ...

FRET Microscopy for Real-time Monitoring of Signaling Events in Live Cells Using Unimolecular Biosensors

F&ouml;rster resonance energy transfer (FRET) microscopy continues to gain increasing interest as a technique for real-time monitoring of biochemical and signaling events in live cells and tissues. Compared to classical biochemical methods, this novel technology is characterized by high temporal and spatial resolution. FRET experiments use various genetically-encoded biosensors which can be expressed and imaged over time in situ or in vivo1-2. Typical biosensors can either report protein-protein interactions by measuring FRET between a fluorophore-tagged pair of proteins or conformational changes in a single protein which harbors donor and acceptor fluorophores interconnected with a binding moiety for a molecule of interest3-4. Bimolecular biosensors for protein-protein interactions include, for example, constructs designed to monitor G-protein activation in cells5, while the unimolecular sensors measuring conformational changes are widely used to image second messengers such as calcium6, cAMP7-8, inositol phosphates9 and cGMP10-11. Here we describe how to build a customized epifluorescence FRET imaging system from single commercially available components and how to control the whole setup using the Micro-Manager freeware. This simple but powerful instrument is designed for routine or more sophisticated FRET measurements in live cells. Acquired images are processed using self-written plug-ins to visualize changes in FRET ratio in real-time during any experiments before being stored in a graphics format compatible with the build-in ImageJ freeware used for subsequent data analysis. This low-cost system is characterized by high flexibility and can be successfully used to monitor various biochemical events and signaling molecules by a plethora of available FRET biosensors in live cells and tissues. As an example, we demonstrate how to use this imaging system to perform real-time monitoring of cAMP in live 293A cells upon stimulation with a &beta;-adrenergic receptor agonist and blocker.

F&#246;rster resonance energy transfer (FRET) microscopy is a powerful technique for real-time monitoring of signaling events in live cells using various biosensors as reporters. Here we describe how to build a customized epifluorescence FRET imaging system from commercially available components and how to use it for FRET experiments.

F&ouml;rster resonance energy transfer (FRET) microscopy  continues to gain increasing interest as a technique for real-time monitoring  of biochemical ...

Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein

Vitamin A is essential for vision and the growth/differentiation of almost all human organs. Plasma retinol binding protein (RBP) is the principle and specific carrier of vitamin A in the blood. Here we describe an optimized technique to produce and purify holo-RBP and two real-time monitoring techniques to study the transport of vitamin A by the high-affinity RBP receptor STRA6. The first technique makes it possible to produce a large quantity of high quality holo-RBP (100%-loaded with retinol) for vitamin A transport assays. High quality RBP is essential for functional assays because misfolded RBP releases vitamin A readily and bacterial contamination in RBP preparation can cause artifacts. Real-time monitoring techniques like electrophysiology have made critical contributions to the studies of membrane transport. The RBP receptor-mediated retinol transport has not been analyzed in real time until recently. The second technique described here is the real-time analysis of STRA6-catalyzed retinol release or loading. The third technique is real-time analysis of STRA6-catalyzed retinol transport from holo-RBP to cellular retinol binding protein I (CRBP-I). These techniques provide high sensitivity and resolution in revealing RBP receptor's vitamin A uptake mechanism.

Here we describe an optimized technique to produce high-quality vitamin A/RBP complex and two real-time monitoring techniques to study vitamin A transport by STRA6, the RBP receptor.

Vitamin A is essential for vision and the growth/differentiation of almost all human organs.  Plasma retinol binding protein (RBP) is the principle and ...

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and temporal resolution to study in vivo hematopoiesis using the murine bone marrow transplant experimental model. Genetic combinatorial marking using lentiviral vectors encoding fluorescent proteins (FPs) enabled cell fate mapping through advanced microscopy imaging. Vectors encoding five different FPs: Cerulean, EGFP, Venus, tdTomato, and mCherry were used to concurrently transduce HSPCs, creating a diverse palette of color marked cells. Imaging using confocal/two-photon hybrid microscopy enables simultaneous high resolution assessment of uniquely marked cells and their progeny in conjunction with structural components of the tissues. Volumetric analyses over large areas reveal that spectrally coded HSPC-derived cells can be detected non-invasively in various intact tissues, including the bone marrow (BM), for extensive periods of time following transplantation. Live studies combining video-rate multiphoton and confocal time-lapse imaging in 4D demonstrate the possibility of dynamic cellular and clonal tracking in a quantitative manner.

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

Combinatorial 5 fluorescent proteins marking of hematopoietic stem and progenitor cells allows in vivo clonal tracking via confocal and two-photon microscopy, providing insights into bone marrow hematopoietic architecture during regeneration. This method allows non-invasive fate mapping of spectrally-coded HSPCs-derived cells in intact tissues for extensive periods of time following transplantation.

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Real-time Imaging of Plant Cell Surface Dynamics with Variable-angle Epifluorescence Microscopy

A plant&#8217;s cell surface is its interface for perceiving environmental cues; it responds with cell biological changes such as membrane trafficking and cytoskeletal rearrangement. Real-time and high-resolution image analysis of such intracellular events will increase the understanding of plant cell biology at the molecular level. Variable angle epifluorescence microscopy (VAEM) is an emerging technique that provides high-quality, time-lapse images of fluorescently-labeled proteins on the plant cell surface. In this article, practical procedures are described for VAEM specimen preparation, adjustment of the VAEM optical system, movie capturing and image analysis. As an example of VAEM observation, representative results are presented on the dynamics of PATROL1. This is a protein essential for stomatal movement, thought to be involved in proton pump delivery to plasma membranes in the stomatal complex of Arabidopsis thaliana. VAEM real-time observation of guard cells and subsidiary cells in A. thaliana cotyledons showed that fluorescently-tagged PATROL1 appeared as dot-like structures on plasma membranes for several seconds and then disappeared. Kymograph analysis of VAEM movie data determined the time distribution of the presence (termed &#8216;residence time&#8217;) of the dot-like structures. The use of VAEM is discussed in the context of this example.

The goal of this protocol is to demonstrate how to monitor fluorescently-tagged protein dynamics on plant cell surfaces with variable-angle epifluorescence microscopy, showing blinking dots of GFP-tagged PATROL1, a membrane trafficking protein, in the cell cortex of the stomatal complex in Arabidopsis thaliana.

A plant&#8217;s cell surface is its interface for perceiving environmental cues; it responds with cell biological changes such as membrane trafficking and ...

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

We present detailed protocols for isolation of aortas from mouse and measurement of their elastic modulus using atomic force microscopy.

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a ...

Scanning Electron Microscopy (SEM) Protocols for Problematic Plant, Oomycete, and Fungal Samples

Common problems in the processing of biological samples for observations with the scanning electron microscope (SEM) include cell collapse, treatment of samples from wet microenvironments and cell destruction. Using young floral tissues, oomycete cysts, and fungi spores (Agaricales) as examples, specific protocols to process delicate samples are described here that overcome some of the main challenges in sample treatment for image capture under the SEM.
Floral meristems fixed with FAA (Formalin-Acetic-Alcohol) and processed with the Critical Point Dryer (CPD) did not display collapsed cellular walls or distorted organs. These results are crucial for the reconstruction of floral development. A similar CPD-based treatment of samples from wet microenvironments, such as the glutaraldehyde-fixed oomycete cysts, is optimal to test the differential growth of diagnostic characteristics (e.g., the cyst spines) on different types of substrates. Destruction of nurse cells attached to fungi spores was avoided after rehydration, dehydration, and the CPD treatment, an important step for further functional studies of these cells.
The protocols detailed here represent low-cost and rapid alternatives for the acquisition of good-quality images to reconstruct growth processes and to study diagnostic characteristics.

Scanning Electron Microscopy SEM Protocols for Problematic Plant, Oomycete, and Fungal Samples

Problems in the processing of biological samples for scanning electron microscopy observation include cell collapse, treatment of samples from wet microenvironments and cell destruction. Low-cost and relatively rapid protocols suited for preparing challenging samples such as floral meristems, oomycete cysts, and fungi (Agaricales) are compiled and detailed here.

Common problems in the processing of biological samples for observations with the scanning electron microscope (SEM) include cell collapse, treatment of ...

Confocal Laser Scanning Microscopy of Calcium Dynamics in Acute Mouse Pancreatic Tissue Slices

The acute mouse pancreatic tissue slice is a unique in situ preparation with preserved intercellular communication and tissue architecture that entails significantly fewer preparation-induced changes than isolated islets, acini, ducts, or dispersed cells described in typical in vitro studies. By combining the acute pancreatic tissue slice with live-cell calcium imaging in confocal laser scanning microscopy (CLSM), calcium signals can be studied in a large number of endocrine and exocrine cells simultaneously, with a single-cell or even subcellular resolution. The sensitivity permits the detection of changes and enables the study of intercellular waves and functional connectivity as well as the study of the dependence of physiological responses of cells on their localization within the islet and paracrine relationship with other cells. Finally, from the perspective of animal welfare, recording signals from a large number of cells at a time lowers the number of animals required in experiments, contributing to the 3R-replacement, reduction, and refinement-principle.

We present the preparation of acute pancreatic tissue slices and their use in confocal laser scanning microscopy to study calcium dynamics simultaneously in a large number of live cells, over long time periods, and with high spatiotemporal resolution.

The acute mouse pancreatic tissue slice is a unique in situ preparation with preserved intercellular communication and tissue architecture that entails ...