This project was supported by the Haihe Laboratory of Cell Ecosystem Innovation Fund (22HHXBSS00036, 22HHXBSS00019), the Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Sciences (2021-I2M-1-040&#65292;2022-I2M-JB-015), the Special Research Fund for Central Universities, Peking Union Medical College (3332022062), and the Science and Technology Support Program of Sichuan Province (NO. 2021YJ0480).

The Boston Children&#39;s Hospital and State Key Laboratory of Experimental Hematology (SKLEH) Animal Care and Use Committee approved and monitored all the procedures. Figure 1 depicts a flow chart of neutrophil culturing with CLON-G and the in vitro death assay.
1. Neutrophil lifespan extension with CLON-G
NOTE: All the mentioned operations and materials must be sterile. Ensure all the solutions are well mixed and distributed evenly.
<ol>
	<li>Preservation of the CLON-G components
	<ol>
		<li>Dissolve 50 mg of Q-VD-oph (see Table of Materials) to a final concentration of 100 mM by adding 973.7 &#181;L of dimethyl sulfoxide (DMSO), and pipette the liquid until the mixture becomes clear. Aliquot 50 &#181;L per tube, and preserve at &#8722;20 &#176;C. 
		CAUTION: DMSO is a harmful chemical liquid. Wear a lab coat, goggles, and a mask to avoid skin contact, eye contact, and inhalation.</li>
		<li>Thaw Hsp70 (see Table of Materials) at 4 &#176;C, and spin down the contents in the vial. Aliquot 1 &#181;L of Hsp70 per tube on ice, and preserve at &#8722;80 &#176;C. 
		NOTE: Hsp70 is a protein; ultra-cold storage is necessary to keep it stable. Avoid the freeze-thaw cycle.</li>
		<li>Dissolve 1 mg of DFO (see Table of Materials) with 7.61 mL RPMI 1640 to obtain a stock of 200 &#181;M. Aliquot 500 &#181;L per tube, and preserve at &#8722;20 &#176;C.</li>
		<li>Dissolve 0.1 g of NAC (see Table of Materials) with 2.5 mL of RPMI 1640 in a 15 mL centrifuge tube, and adjust the pH to 7-7.4 with NaOH. Add RPMI 1640 to a final volume of 3.06 mL to make a 200 mM NAC stock. Filter it with a 0.2 &#181;m filtering unit. Aliquot 500 &#181;L per tube, and preserve at &#8722;20 &#176;C. 
		NOTE: Dissolving NAC in this high concentration is not easy, and vortexing can help dissolve it. Phenol red in RPMI 1640 is a perfect indication of the pH; when the NAC is just dissolved, the color is yellowish; adjust it until it becomes pinkish. NAC stock solutions are stable for up to 1 month at &#8722;20 &#176;C.</li>
		<li>Dissolve 10 mg of Nec-1s (see Table of Materials) to 20 mM with 1.8 mL of DMSO, and pipette the mixture until it becomes clear. Aliquot 50 &#181;L per tube, and preserve at &#8722;20 &#176;C. Protect from light.</li>
		<li>Dissolve 250 &#181;g of G-CSF (see Table of Materials) to 200 &#181;g/mL with 1.25 mL of RPMI 1640. Aliquot 50 &#181;L per tube, and preserve at 4 &#176;C.</li>
	</ol>
	</li>
	<li>Preparation of 2x CLON-G culture medium
	<ol>
		<li>Prepare the basic medium. Add 39.5 mL of RPMI 1640, 10 mL of fetal bovine serum (FBS), and 0.5 mL pen-strep (antibiotics) to a 50 mL tube to make RPMI 1640 with 20% FBS and 1% PS as a basic medium. 
		NOTE: This high concentration of FBS is used to provide for the prolonged culture of neutrophils, which might be greater than 5 days. If the culturing time is 1-2 days, 10%-15% FBS is sufficient.</li>
		<li>Thaw all the stock solutions of the CLON-G components on ice.</li>
		<li>Dilute 1 &#181;L of Hsp70 to 20 &#181;M by adding 606 &#181;L of the basic medium. Dilute 1 &#181;L of 200 &#181;g/mL G-CSF to 20 &#181;g/mL by adding 9 &#181;L of the basic medium.</li>
		<li>Add 976 &#181;L of basic medium to a 15 mL centrifuge tube. Add 1 &#181;L of Q-VD-oph (100 mM), 10 &#181;L of DFO (200 &#181;M), 1 &#181;L of Hsp70 (20 &#181;M), 10 &#181;L of NAC (200 mM), 1 &#181;L of Nec-1s (20 mM), and 1 &#181;L of G-CSF (20 &#181;g / mL) to make 1 mL of 2x CLON-G medium. 
		NOTE: The 2x CLON-G medium should be used immediately after it is prepared. One may store the 2x CLON-G temporarily at 4 &#176;C. Leftover 20 &#181;M Hsp70 must be discarded.</li>
	</ol>
	</li>
	<li>Neutrophil culture
	<ol>
		<li>Isolate mouse neutrophils by gradient centrifugation following a previous report25. Resuspend the isolated mouse neutrophils in the basic medium (1 million cells/100 &#181;L). 
		NOTE: Avoid activating the neutrophils by handling them gently. Avoid foaming during the whole process.</li>
		<li>Add 500 &#181;L of 2x CLON-G medium, 400 &#181;L of the basic medium, and 100 &#181;L of the cell suspension to 24-well non-tissue cultured culture plates (see Table of Materials), and gently pipette three to four times. 
		NOTE: High concentrations of the components in the 2x CLON-G medium might damage the neutrophils; avoid adding them together without the basic medium. The non-tissue cultured culture plate is necessary to avoid neutrophil adhesion.</li>
		<li>Place the culture plate in a 37 &#176;C and 5 % CO2 incubator smoothly. 
		NOTE: It is unnecessary to exchange the cell medium within 7 days. The final concentrations of the CLON-G composition are 50 &#181;M Q-VD-Oph, 1 &#181;M DFO, 10 pM Hsp70, 1 mM NAC, 10 &#181;M Nec-1 s, and 10 ng/mL G-CSF.</li>
		<li>Stain the cultured neutrophils with Wright Giemsa compound stain (see Table of Materials), and analyze with a light microscope (Figure 2A-D). Alternatively, stain with APC-CD11b and PE-Cy7-Ly6G antibodies, and analyze with flow cytometry (Figure 2E-I) as described previously26.</li>
	</ol>
	</li>
</ol>
2. In vitro spontaneous death assay of neutrophils
<ol>
	<li>Flow cytometry analysis
	<ol>
		<li>Culture isolated neutrophils at a density of 1 million cells/mL in the basic medium at 37 &#176;C and 5% CO2. The 24-well culture plate is non-tissue cultured. Add 1 mL of cell medium per well.</li>
		<li>Dissolve 1 g of CaCl2 with 45 mL of saline to make 200 mM CaCl2. Filter it with a 0.2 &#181;m filtering unit. Preserve at 4 &#176;C.</li>
		<li>Prepare the staining mix. Add 7 &#181;L of saline per sample to a 1.5 mL tube, and add 0.4 mg/mL FITC-Annexin-V, 0.5 mg/mL propidium iodide (PI), and 200 mM CaCl2 solution at 1 &#181;L each per sample. Mix well. Use the solution immediately after preparation.</li>
		<li>Pipette the cell medium gently five to seven times to mix well, followed by transferring 100 &#181;L to a flow cytometry tube at the desired time points. 
		NOTE: Avoid foaming during the whole process.</li>
		<li>Vortex counting beads (see Table of Materials) to mix them well. Pipette 10 &#181;L of the well-mixed counting beads to the same flow cytometry tube as in step 2.1.4.</li>
		<li>Add 10 &#181;L the prepared staining mix (step 2.1.3) to the flow cytometry tube. Incubate at room temperature for 5 min away from light.</li>
		<li>Add 100 &#181;L of saline to the tube, and mix well to ensure the even distribution of the counting beads and cells.</li>
		<li>Perform flow cytometry analysis of the cell medium. Collect the cells at a low rate with ~400 events/s. Gate the APC-PE-Cy7- cells to FSC-A and SSC-A, and gate the intact cells with medium FSC-A and SSC-A positions to the FITC-Annexin-V and PE-PI; the Annexin-V&#8722;PI&#8722; population is classified as healthy cells. 
		NOTE: The following equations determine the total number of healthy cells per sample and the viability of the neutrophils: 
		Total number of healthy cells per sample27 = (1,000/number of counting beads) &#215; number of Annexin-V&#8722;PI&#8722; population &#215; 10 
		&#8203;Viability of neutrophils = total number of healthy cells at the indicated time/total number of healthy cells at time zero</li>
	</ol>
	</li>
	<li>Fluorescent image assay
	<ol>
		<li>Culture isolated neutrophils at a density of 1 million cells/mL in the basic medium at 37 &#176;C and 5% CO2 in a confocal plate with 2 mL of cell medium per plate. 
		NOTE: A confocal fluorescence microscope has the best image quality, but any fluorescence microscope that has 488/561/DIC channels is sufficient to support this experiment.</li>
		<li>Take the plate out gently at the indicated time point. Add 10 &#181;L each of 0.4 mg/mL FITC-Annexin-V, 0.5 mg/mL PI, and 200 mM CaCl2 to the plate evenly. Stain at room temperature for 5 min. 
		NOTE: Avoid shaking during the whole process. Add the staining agents evenly and gently.</li>
		<li>Capture fluorescence images at 488 (annexin-V)/561 (PI)/DIC channels using a confocal fluorescence microscope with a 20x objective lens (see Table of Materials). Set the exposure time of the 488 channel as 500 ms, the 561 channel as 200 ms, and the DIC channel as 100 ms. Select 5-10 random areas for each plate. The cell types are defined in our previously published report14.</li>
	</ol>
	</li>
</ol>

The authors declare that the research was conducted in the absence of any conflicts of interest.

Neutrophils play vital roles in innate and adaptive immunity, and their homeostasis is tightly regulated. Neutrophils are the most abundant leukocytes in human peripheral blood, and they have a robust and fast turnover. A healthy adult can release 1 x 109 neutrophils/kg daily from the bone marrow28. The death of neutrophils has hence become one of the puzzling enigmas of this field, and much effort has been dedicated to better understanding them. Caspase29,<...

Neutrophils are known to comprise an arsenal of abundant cytoplasmic granules, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, antimicrobial enzymes, and various organelles that defend against invading microbes; additionally, they are highly motile and are the first cells recruited to the inflammation site, meaning neutrophils are the first line of defense of the innate immune system1,2. Granulocyte transfusion therapy has hence become a promising clinical treatment for neutropenia-related infections to transiently boost neutrophil immunity3,4,5. Recent discoveries have clearly shown that neutrophils also function as multifaced effectors in many physiopathological scenarios6. The average lifespan of a neutrophil is less than 24 h, and, thus, basic research on neutrophils and the application of neutrophil studies are tremendously difficult due to the limitations related to stable genetic manipulation and long-term storage7,8,9,10,11. There are some cell lines that can partially showcase some neutrophil functions, such as HL-60, PLB-985, NB4, Kasumi-1, and induced pluripotent stem cells12. These cell lines can achieve effective gene editing and cryopreservation; however, they still differ quite immensely from primary neutrophils and, thus, cannot faithfully recapitulate neutrophil functions13. Thus, most of the research in this field still relies on freshly isolated primary neutrophils. The field still relies on generating expensive and time-consuming conditional knock-out mice to investigate specific gene functions in neutrophils, but no human models currently exist.
Having put our effort into exploring the heterogeneous processes involved in neutrophil death and the multiple pathways that regulate these processes14,15, a new treatment termed CLON-G (caspases-lysosomal membrane permeabilization-oxidant-necroptosis inhibition plus granulocyte colony-stimulating factor) was recently reported16. CLON-G consists of Q-VD-oph (quinolyl-valyl-O-methylaspartyl-[-2,6-difluorophenoxy]-methyl ketone), Hsp70 (heat shock protein 70), DFO (deferoxamine), NAC (N-acetylcysteine), Nec-1s (necrostatin-1s), and G-CSF (granulocyte colony-stimulating factor). Neutrophil spontaneous death is mediated by multiple pathways, including apoptosis, necroptosis, and pyroptosis. Q-VD-oph inhibits the apoptosis of neutrophils as a pan-caspase inhibitor by targeting caspase 1, caspase 3, caspase 8, and caspase 917. Neutrophil necroptosis is dependent on a signaling pathway involving receptor-interacting protein kinase-1 (RIPK1) and mixed lineage kinase domain-like protein (MLKL)18. As an RIPK1 inhibitor, Nec-1s inhibit the necroptosis of neutrophils. Hsp70 and DFO can inhibit lysosomal membrane permeabilization (LMP), which could induce neutrophil apoptosis19 and pyroptosis20. Reactive oxygen species (ROS) play vital roles in neutrophil death by mediating LMP19 and apoptosis21 and by inhibiting survival signals22. As an antioxidant that can reduce ROS accumulation, NAC delays neutrophil death. As a growth factor, G-CSF activates neutrophil survival signals and inhibits calpain-induced apoptosis23,24. By simultaneously targeting multiple neutrophil spontaneous death pathways, the neutrophil lifespan can be effectively extended to greater than 5 days without compromising their function. CLON-G treatment expands the possibilities of neutrophil preservation, transportation, and gene manipulation, which can accelerate research in the neutrophil community. Meanwhile, based on the knowledge of neutrophil death, the currently approved protocols for cell death assays can cause unexpected damage to neutrophils14, so these protocols have been refined to be more appropriate for neutrophil studies. This report provides detailed protocols for neutrophil culturing with CLON-G and an in vitro cell death assay of mouse neutrophils using flow cytometry and fluorescence imaging. CLON-G is effective on both mouse and human neutrophils; however, the mouse samples are demonstrated here to simplify this protocol. The concentration of NAC is 1 mM for mouse neutrophils and 10 &#181;M for human neutrophils. Hsp70 is species-specific and, thus, should be utilized according to the source of the neutrophil. For this protocol, it does not matter whether neutrophils are isolated from peripheral blood or bone marrow and how they are isolated.
For the present study, neutrophils were isolated from mouse bone marrow to achieve enough neutrophils for the experiments, as about 1 x 107-1.5 x 107 neutrophils can be obtained from the bone marrow, while only 1 x 106 neutrophils can be isolated from the peripheral blood of a single 8-12 week old C57BL/6 mouse (of either sex). Gradient centrifugation was conducted to avoid possible damage and activation from the mechanical stimulation of FACS sorting or MACS sorting.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.2 &#181;m syringe filter</td>
			<td>Pall Corporation</td>
			<td>4612</td>
			<td>Filtrate prepared CLON-G components.</td>
		</tr>
		<tr>
			<td>1.5 mL micro centrifuge tube</td>
			<td>LABSELECT</td>
			<td>MCT-001-150</td>
			<td>Lab consumable.</td>
		</tr>
		<tr>
			<td>15 mL Centrifuge Tubes</td>
			<td>LABSELECT</td>
			<td>CT-002-15</td>
			<td>Lab consumable.</td>
		</tr>
		<tr>
			<td>24 well cell culture plate</td>
			<td>Falcon</td>
			<td>351147</td>
			<td>Neutrophil culture plate.</td>
		</tr>
		<tr>
			<td>50 mL Centrifuge Tubes</td>
			<td>LABSELECT</td>
			<td>CT-002-50</td>
			<td>Lab consumable.</td>
		</tr>
		<tr>
			<td>BD LSRII</td>
			<td>BD</td>
			<td></td>
			<td>Instrument for flow cytometry analysis of neutrophil death.</td>
		</tr>
		<tr>
			<td>Calcium chloride (CaCl2)</td>
			<td>Sigma Aldrich</td>
			<td>C4901</td>
			<td>Assitant of Annexin-V binding&#160; to phosphatidylserine.</td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Perkinelmer</td>
			<td>UltraVIEW VOX</td>
			<td>Instrument for fluorescent analysis of neutrophil death.</td>
		</tr>
		<tr>
			<td>Confocal plate</td>
			<td>NEST</td>
			<td>801001-20mm</td>
			<td>Lab consumable for fluorescent image assay.</td>
		</tr>
		<tr>
			<td>Counting beads</td>
			<td>Thermo Fisher</td>
			<td>C36950</td>
			<td>Quantification in flow cytometry analysis of neutrophil death.</td>
		</tr>
		<tr>
			<td>DFO</td>
			<td>Sigma Aldrich</td>
			<td>D9533</td>
			<td>Component of CLON-G. LMP inhibitor.</td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide ( DMSO)</td>
			<td>Sigma Aldrich</td>
			<td>D2650</td>
			<td>Solvent for Q-VD-oph and Nec-1s.</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Gibco</td>
			<td>10099141C</td>
			<td>Component of neutrophil culture basic medium. Nutrition supply.</td>
		</tr>
		<tr>
			<td>FITC-Annexin-V</td>
			<td>BD</td>
			<td>51-65874X</td>
			<td>Annexin-V can bind to phosphatidylserine of aged cells.This is at FITC channel.</td>
		</tr>
		<tr>
			<td>Hsp70</td>
			<td>Abcam</td>
			<td>ab113187</td>
			<td>Component of CLON-G. LMP inhibitor.</td>
		</tr>
		<tr>
			<td>NAC</td>
			<td>Sigma Aldrich</td>
			<td>A9165</td>
			<td>Component of CLON-G. Antioxidant.</td>
		</tr>
		<tr>
			<td>Nec-1s</td>
			<td>EMD Millipore</td>
			<td>852391-15-2</td>
			<td>Component of CLON-G. Necroptosis inhibitor.</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin Solution (PS)</td>
			<td>Gibco</td>
			<td>15070063</td>
			<td>Component of neutrophil culture basic medium. Antibiotics to protect cells from bacteria comtamination.</td>
		</tr>
		<tr>
			<td>Propidium Iodide (PI)</td>
			<td>BioLegend</td>
			<td>421301</td>
			<td>For neutrophil death assay. A small fluorescent molecule that binds to DNA&#160; but cannot passively traverse into cells that possess an intact plasma membrane.</td>
		</tr>
		<tr>
			<td>Q-VD-oph</td>
			<td>Selleck chem</td>
			<td>S7311</td>
			<td>Component of CLON-G. Pan-caspase inhibitor.</td>
		</tr>
		<tr>
			<td>Recombinant Human Granulocyte Colony-stimulating Factor for Injection (CHO cell)(G-CSF)</td>
			<td>Chugai Pharma China</td>
			<td>GRANOCYTE</td>
			<td>Component of CLON-G.&#160; Promote neutrophil survival through Akt pathway.</td>
		</tr>
		<tr>
			<td>Round-Bottom Polystyrene Tubes</td>
			<td>Falcon</td>
			<td>100-0102</td>
			<td>Lab consumable for flow cytometry analysis.</td>
		</tr>
		<tr>
			<td>RPMI1640</td>
			<td>Gibco</td>
			<td>C11875500BT</td>
			<td>Component of neutrophil culture basic medium.</td>
		</tr>
		<tr>
			<td>Saline</td>
			<td>LEAGENE</td>
			<td>R00641</td>
			<td>Solution for flow cytometry analysis of neutrophil death.</td>
		</tr>
		<tr>
			<td>Sodium hydroxide (NaOH)</td>
			<td>FENG CHUAN</td>
			<td>13-011-00029</td>
			<td>pH adjustion for NAC.</td>
		</tr>
		<tr>
			<td>Wright-Giemsa Stain Solution</td>
			<td>Solarbio</td>
			<td>G1020</td>
			<td>Neutrophil cytospin staining.</td>
		</tr>
	</tbody>
</table>

neutrophil lifespan extension with clon-g and an in vitro spontaneous death assay

The average lifespan of a neutrophil is less than 24 h, which limits basic research on neutrophils and the application of neutrophil studies. Our previous research indicated that multiple pathways could mediate the spontaneous death of neutrophils. A cocktail was developed by simultaneously targeting these pathways, caspases-lysosomal membrane permeabilization-oxidant-necroptosis inhibition plus granulocyte colony-stimulating factor (CLON-G), which prolonged the neutrophil lifespan to greater than 5 days without significantly compromising the neutrophil function. Concurrently, a reliable and stable protocol for assessing and evaluating neutrophil death was also developed. In this work, we show that CLON-G can prolong the neutrophil lifespan in vitro to more than 5 days, and we exhibit the lengthening of the neutrophil lifespan with FACS and confocal fluorescence microscopy. This report introduces procedures for the preparation of CLON-G and showcases an in vitro spontaneous death assay of neutrophils, which can be used for the study of neutrophils and for subsequently interrogating neutrophil death, thus providing a reliable resource for the neutrophil community.

The Wright-Giemsa-stained morphology (Figure 2A-D) and FACS phenotypes (Figure 2E-J) of the CLON-G treated neutrophils were not affected. The viability of the CLON-G treated neutrophils at 24 h was about 90%+ based on flow cytometry analysis (Figure 3) and the fluorescent image assays (Figure 4). Lower viability could result from improp...

Watch this Scientific Journal Video about Neutrophil Lifespan Extension with CLON-G and an In Vitro Spontaneous Death Assay at JoVE.com

Neutrophil Lifespan Extension with CLON-G and an In Vitro Spontaneous Death Assay

This protocol details the preparation of CLON-G to extend the neutrophil lifespan to greater than 5 days and provides a reliable procedure for evaluating neutrophil death with flow cytometry and confocal fluorescence microscopy.

Neutrophil Lifespan Extension with CLON-G and an In Vitro Spontaneous Death Assay

The average lifespan of a neutrophil is less than 24 h, which limits basic research on neutrophils and the application of neutrophil studies. Our previous ...

neutrophil-lifespan-extension-with-clon-g-an-vitro-spontaneous-death

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1.1K Views.  Chinese Academy of Medical Sciences & Peking Union Medical College. This protocol details the preparation of CLON-G to extend the neutrophil lifespan to greater than 5 days and provides a reliable procedure for evaluating neutrophil death with flow cytometry and confocal fluorescence microscopy. 

Video: Neutrophil Lifespan Extension with CLON-G and an In Vitro Spontaneous Death Assay

Proboscis Extension Response (PER) Assay in Drosophila

Proboscis extension response (PER) is a taste behavior assay that has been used in flies as well as in honeybees.
On the surface of the fly's mouth (labellum), there are hair-like structures called sensilla which houses taste neurons. When an attractive substance makes contact to the labellum, the fly extends its proboscis to consume the material. Proboscis Extension Response (PER) assay measures this taste behavior response, and it is a useful method to learn about food preferences in a single fly. Solutions of various sugars, such as sucrose, glucose and fructose, are very attractive to the fly. The effect of aversive substances can also be tested as reduction of PER when mixed in a sweet solution.Despite the simplicity of the basic procedure, there are many things that can prevent it from working. One of the factors that requires attention is the fly's responsive state. The required starvation time to bring the fly to the proper responsive state varies drastically from 36 to 72 hours. We established a series of controls to evaluate the fly's state and which allows screening out of non-responsive or hyper-responsive individual animals. Another important factor is the impact level and the position of the contact to the labellum, which would be difficult to describe by words. This video presentation demonstrates all these together with several other improvements that would increase the reproducibility of this method.

Proboscis Extension Response PER Assay in Drosophila

Proboscis extension response or PER is a taste behavior assay that has been used in flies as well as in honeybees. When the proboscis makes contact with an attractive substance, the fly extends its proboscis to consume the substance. Solutions of various sugars are very attractive to the fly.

Proboscis extension response (PER) is a taste behavior assay that has been used in flies as well as in honeybees.
On the surface of the fly's mouth ...

An In vitro FluoroBlok Tumor Invasion Assay

The hallmark of metastatic cells is their ability to invade through the basement membrane and migrate to other parts of the body. Cells must be able to both secrete proteases that break down the basement membrane as well as migrate in order to be invasive. BD BioCoat Tumor Invasion System provides cells with conditions that allow assessment of their invasive property in vitro1,2. It consists of a BD Falcon FluoroBlok 24-Multiwell Insert Plate with an 8.0 micron pore size PET membrane that has been uniformly coated with BD Matrigel Matrix. This uniform layer of BD Matrigel Matrix serves as a reconstituted basement membrane in vitro providing a true barrier to non-invasive cells while presenting an appropriate protein structure to study invasion. The coating process occludes the pores of the membrane, blocking non-invasive cells from migrating through the membrane. In contrast, invasive cells are able to detach themselves from and migrate through the coated membrane. Quantitation of cell invasion can be achieved by either pre- or post-cell invasion labeling with a fluorescent dye such as DiIC12(3) or calcein AM, respectively, and measuring the fluorescence of invading cells. Since the BD FluoroBlok membrane effectively blocks the passage of light from 490-700 nm at &gt;99% efficiency, fluorescently-labeled cells that have not invaded are not detected by a bottom-reading fluorescence plate reader. However, cells that have invaded to the underside of the membrane are no longer shielded from the light source and are detected with the respective plate reader. This video demonstrates an endpoint cell invasion assay, using calcein AM to detect invaded cells.

An In vitro FluoroBlok Tumor Invasion Assay

This video demonstrates how to measure cell invasion through cell culture inserts using a fluorescence-based methodology.

The hallmark of metastatic cells is their ability to invade through the basement membrane and migrate to other parts of the body. Cells must be able to ...

A &#946;-glucuronidase (GUS) Based Cell Death Assay

We have developed a novel transient plant expression system that simultaneously expresses the reporter gene, &beta;-glucuronidase (GUS), with putative positive or negative regulators of cell death. In this system, N. benthamiana leaves are co-infiltrated with a 35S driven expression cassette containing the gene to be analyzed, and the GUS vector pCAMBIA 2301 using Agrobacterium strain LBA4404 as a vehicle. Because live cells are required for GUS expression to occur, loss of GUS activity is expected when this marker gene is co-expressed with positive regulators of cell death. Equally, increased GUS activity is observed when anti-apoptotic genes are used compared to the vector control. As shown below, we have successfully used this system in our lab to analyze both pro- and anti-death players. These include the plant anti-apoptotic Bcl-2 Associated athanoGene (BAG) family, as well as, known mammalian inducers of cell death, such as BAX. Additionally, we have used this system to analyze the death function of specific truncations within proteins, which could provide clues on the possible post-translational modification/activation of these proteins. Here, we present a rapid and sensitive plant based method, as an initial step in investigating the death function of specific genes.

A &amp;#946;-glucuronidase GUS Based Cell Death Assay

Programmed cell death assays commonly used in mammalian systems such as DNA laddering or TUNEL assays, are often difficult to reproduce in plants. In combination with a GUS reporter system, we propose a rapid, plant based transient assay to analyze the potential death properties of specific genes.

We have developed a novel transient plant expression system that simultaneously expresses the reporter gene, &beta;-glucuronidase (GUS), with putative ...

Measurement of Lifespan in Drosophila melanogaster

Aging is a phenomenon that results in steady physiological deterioration in nearly all organisms in which it has been examined, leading to reduced physical performance and increased risk of disease. Individual aging is manifest at the population level as an increase in age-dependent mortality, which is often measured in the laboratory by observing lifespan in large cohorts of age-matched individuals. Experiments that seek to quantify the extent to which genetic or environmental manipulations impact lifespan in simple model organisms have been remarkably successful for understanding the aspects of aging that are conserved across taxa and for inspiring new strategies for extending lifespan and preventing age-associated disease in mammals.
The vinegar fly, Drosophila melanogaster, is an attractive model organism for studying the mechanisms of aging due to its relatively short lifespan, convenient husbandry, and facile genetics. However, demographic measures of aging, including age-specific survival and mortality, are extraordinarily susceptible to even minor variations in experimental design and environment, and the maintenance of strict laboratory practices for the duration of aging experiments is required. These considerations, together with the need to practice careful control of genetic background, are essential for generating robust measurements. Indeed, there are many notable controversies surrounding inference from longevity experiments in yeast, worms, flies and mice that have been traced to environmental or genetic artifacts1-4. In this protocol, we describe a set of procedures that have been optimized over many years of measuring longevity in Drosophila using laboratory vials. We also describe the use of the dLife software, which was developed by our laboratory and is available for download (<a href="http://sitemaker.umich.edu/pletcherlab/software">http://sitemaker.umich.edu/pletcherlab/software</a>). dLife accelerates throughput and promotes good practices by incorporating optimal experimental design, simplifying fly handling and data collection, and standardizing data analysis. We will also discuss the many potential pitfalls in the design, collection, and interpretation of lifespan data, and we provide steps to avoid these dangers.

Measurement of Lifespan in Drosophila melanogaster

Drosophila melanogaster is a powerful model organism for exploring the molecular basis of longevity regulation. This protocol will discuss the steps involved in generating a reproducible, population-based measurement of longevity as well as potential pitfalls and how to avoid them.

Aging is a phenomenon that results in steady physiological deterioration in nearly all organisms in which it has been examined, leading to reduced ...

Isolation of Native Soil Microorganisms with Potential for Breaking Down Biodegradable Plastic Mulch Films Used in Agriculture

Fungi native to agricultural soils that colonized commercially available biodegradable mulch (BDM) films were isolated and assessed for potential to degrade plastics. Typically, when formulations of plastics are known and a source of the feedstock is available, powdered plastic can be suspended in agar-based media and degradation determined by visualization of clearing zones. However, this approach poorly mimics in situ degradation of BDMs. First, BDMs are not dispersed as small particles throughout the soil matrix. Secondly, BDMs are not sold commercially as pure polymers, but rather as films containing additives (e.g. fillers, plasticizers and dyes) that may affect microbial growth. The procedures described herein were used for isolates acquired from soil-buried mulch films. Fungal isolates acquired from excavated BDMs were tested individually for growth on pieces of new, disinfested BDMs laid atop defined medium containing no carbon source except agar. Isolates that grew on BDMs were further tested in liquid medium where BDMs were the sole added carbon source. After approximately ten weeks, fungal colonization and BDM degradation were assessed by scanning electron microscopy. Isolates were identified via analysis of ribosomal RNA gene sequences. This report describes methods for fungal isolation, but bacteria also were isolated using these methods by substituting media appropriate for bacteria. Our methodology should prove useful for studies investigating breakdown of intact plastic films or products for which plastic feedstocks are either unknown or not available. However our approach does not provide a quantitative method for comparing rates of BDM degradation.

Plastic films labeled "biodegradable" are commercially available for agricultural use as mulches. Tillage represents an attractive disposal method, but degradation under field conditions is poorly understood. The purpose of this study was to develop methods for isolating native soil fungi and bacteria that colonize plastic mulch films after field burial.

Fungi native to agricultural soils that colonized commercially available biodegradable mulch (BDM) films were isolated and assessed for potential to ...

Optimized Scratch Assay for In Vitro Testing of Cell Migration with an Automated Optical Camera

Cell migration is an important process that influences many aspects of health, such as wound healing and cancer, and it is, therefore, crucial for developing methods to study the migration. The scratch assay has long been the most common in vitro method to test compounds with anti- and pro-migration properties because of its low cost and simple procedure. However, an often-reported problem of the assay is the accumulation of cells across the edge of the scratch. Furthermore, to obtain data from the assay, images of different exposures must be taken over a period of time at the exact same spot to compare the movements of the migration. Different analysis programs can be used to describe the scratch closure, but they are labor intensive, inaccurate, and forces cycles of temperature changes. In this study, we demonstrate an optimized method for testing the migration effect, e.g. with the naturally occurring proteins Human- and Bovine-Lactoferrin and their N-terminal peptide Lactoferricin on the epithelial cell line HaCaT. A crucial optimization is to wash and scratch in PBS, which eliminates the aforementioned accumulation of cells along the edge. This could be explained by the removal of cations, which have been shown to have an effect on keratinocyte cell-cell connection. To ensure true detection of migration, pre-treating with mitomycin C, a DNA synthesis inhibitor, was added to the protocol. Finally, we demonstrate the automated optical camera, which eliminates excessive temperature cycles, manual labor with scratch closure analysis, while improving on reproducibility and ensuring analysis of identical sections of the scratch over time.

Optimized Scratch Assay for In Vitro Testing of Cell Migration with an Automated Optical Camera

Here we describe a procedure to test the cell migration in vitro with an automated optical camera microscope. The scratch assay has been widely used where the closure of the scratch is followed for a set period. The optical microscope enables dependable and cheap detection of cell migration.

Cell migration is an important process that influences many aspects of health, such as wound healing and cancer, and it is, therefore, crucial for ...

Imaging Molecular Adhesion in Cell Rolling by Adhesion Footprint Assay

Rolling adhesion, facilitated by selectin-mediated interactions, is a highly dynamic, passive motility in recruiting leukocytes to the site of inflammation. This phenomenon occurs in postcapillary venules, where blood flow pushes leukocytes in a rolling motion on the endothelial cells. Stable rolling requires a delicate balance between adhesion bond formation and their mechanically-driven dissociation, allowing the cell to remain attached to the surface while rolling in the direction of flow. Unlike other adhesion processes occurring in relatively static environments, rolling adhesion is highly dynamic as the rolling cells travel over thousands of microns at tens of microns per second. Consequently, conventional mechanobiology methods such as traction force microscopy are unsuitable for measuring the individual adhesion events and the associated molecular forces due to the short timescale and high sensitivity required. Here, we describe our latest implementation of the adhesion footprint assay to image the P-selectin: PSGL-1 interactions in rolling adhesion at the molecular level. This method utilizes irreversible DNA-based tension gauge tethers to produce a permanent history of molecular adhesion events in the form of fluorescence tracks. These tracks can be imaged in two ways: (1) stitching together thousands of diffraction-limited images to produce a large field of view, enabling the extraction of adhesion footprint of each rolling cell over thousands of microns in length, (2) performing DNA-PAINT to reconstruct super-resolution images of the fluorescence tracks within a small field of view. In this study, the adhesion footprint assay was used to study HL-60 cells rolling at different shear stresses. In doing so, we were able to image the spatial distribution of the P-selectin: PSGL-1 interaction and gain insight into their molecular forces through fluorescence intensity. Thus, this method provides the groundwork for the quantitative investigation of the various cell-surface interactions involved in rolling adhesion at the molecular level.

This protocol presents the experimental procedures to perform the adhesion footprint assay to image the adhesion events during fast cell rolling adhesion.

Rolling adhesion, facilitated by selectin-mediated interactions, is a highly dynamic, passive motility in recruiting leukocytes to the site of ...

Real-Time Detection of Reactive Oxygen Species Production in Immune Response in Rice with a Chemiluminescence Assay

Reactive oxygen species (ROS) play vital roles in a variety of biological processes, including the sensing of abiotic and biotic stresses. Upon pathogen infection or challenge with pathogen-associated chemicals (pathogen-associated molecular patterns [PAMPs]), an array of immune responses, including a ROS burst, are quickly induced in plants, which is called PAMP-triggered immunity (PTI). A ROS burst is a hallmark PTI response, which is catalyzed by a group of plasma membrane-localized NADPH oxidases-the RBOH family proteins. The vast majority of ROS comprise hydrogen peroxide (H2O2), which can be easily and steadily detected by a luminol-based chemiluminescence method. Chemiluminescence is a photon-producing reaction in which luminol, or its derivative (such as L-012), undergoes a redox reaction with ROS under the action of a catalyst. This paper describes an optimized L-012-based chemiluminescence method to detect apoplast ROS production in real-time upon PAMP elicitation in rice tissues. The method is easy, steady, standardized, and highly reproducible under firmly controlled conditions.

Here, we describe a method for the real-time detection of apoplastic reactive oxygen species (ROS) production in rice tissues in pathogen-associated molecular pattern-triggered immune response. This method is simple, standardized, and generates highly reproducible results under controlled conditions.

Reactive oxygen species (ROS) play vital roles in a variety of biological processes, including the sensing of abiotic and biotic stresses. Upon pathogen ...

Investigating Zinc Transport Mechanism in Mammalian Cells with FluoZin-3 Assay

Characterizing Mammalian Zinc Transporters Using an In Vitro Zinc Transport Assay

Transition metals such as Zn2+ ions must be tightly regulated due to their cellular toxicity. Previously, the activity of Zn2+ transporters was measured indirectly by determining the expression level of the transporter under different concentrations of Zn2+. This was done by utilizing immunohistochemistry, measuring mRNA in the tissue, or determining the cellular Zn2+ levels. With the development of intracellular Zn2+ sensors, the activities of zinc transporters are currently primarily determined by correlating changes in intracellular Zn2+, detected using fluorescent probes, with the expression of the Zn2+ transporters. However, even today, only a few labs monitor dynamic changes in intracellular Zn2+ and use it to measure the activity of zinc transporters directly. Part of the problem is that out of the 10 zinc transporters of the ZnT family, except for ZnT10 (transports manganese), only zinc transporter 1 (ZnT1) is localized at the plasma membrane. Therefore, linking the transport activity to changes in the intracellular Zn2+ concentration is hard. This article describes a direct way to determine the zinc transport kinetics using an assay based on a zinc-specific fluorescent dye, FluoZin-3. This dye is loaded into mammalian cells in its ester form and then trapped in the cytosol due to cellular di-esterase activity. The cells are loaded with Zn2+ by utilizing the Zn2+ ionophore pyrithione. The ZnT1 activity is assessed from the linear part of the reduction in fluorescence following the cell washout. The fluorescence measured at an excitation of 470 nm and emission of 520 nm is proportional to the free intracellular Zn2+. Selecting the cells expressing ZnT1 tagged with the mCherry fluorophore allows for monitoring only the cells expressing the transporter. This assay is used to investigate the contribution of different domains of ZnT1 protein to the transport mechanism of human ZnT1, a eukaryotic transmembrane protein that extrudes excess zinc from the cell.

Author Spotlight: Exploring Cellular Zinc Regulation Through ZnT1 Functionality 

Zinc transport has proven challenging to measure due to the weak causal links to protein function and the low temporal resolution. This protocol describes a method for monitoring, with high temporal resolution, Zn2+ extrusion from living cells by utilizing a Zn2+ sensitive fluorescent dye, thus providing a direct measure of Zn2+ efflux.

Transition metals such as Zn2+ ions must be tightly regulated due to their cellular toxicity. Previously, the activity of Zn2+ transporters was measured ...

Unveiling Aging Mysteries: Lifespan Machine for High-Throughput Insights

High-Throughput Behavioral Aging and Lifespan Assays Using the Lifespan Machine

Genetically identical animals kept in a constant environment display a wide distribution of lifespans, reflecting a large non-genetic, stochastic aspect to aging conserved across all organisms studied. This stochastic component means that in order to understand aging and identify successful interventions that extend the lifespan or improve health, researchers must monitor large populations of experimental animals simultaneously. Traditional manual death scoring limits the throughput and scale required for large-scale hypothesis testing, leading to the development of automated methods for high-throughput lifespan assays. The Lifespan Machine (LSM) is a high-throughput imaging platform that combines modified flatbed scanners with custom image processing and data validation software for the life-long tracking of nematodes. The platform constitutes a major technical advance by generating highly temporally resolved lifespan data from large populations of animals at an unprecedented scale and at a statistical precision and accuracy equal to manual assays performed by experienced researchers. Recently, the LSM has been further developed to quantify the behavioral and morphological changes observed during aging and relate them to lifespan. Here, we describe how to plan, run, and analyze an automated lifespan experiment using the LSM. We further highlight the critical steps required for the successful collection of behavioral data and high-quality survival curves.

Author Spotlight: Automated Lifespan Monitoring &#8211; Discovering Aging Dynamics with the Lifespan Machine 

The imaging platform "The Lifespan Machine" automates the lifelong observation of large populations. We show the steps required to perform lifespan, stress resistance, pathogenesis, and behavioral aging assays. The quality and scope of the data allow researchers to study interventions in aging despite the presence of biological and environmental variation.

Genetically identical animals kept in a constant environment display a wide distribution of lifespans, reflecting a large non-genetic, stochastic aspect ...