The authors acknowledge funding sources responsible for this work: 5K12HD055929 (HHR), 5R01NS080180-02 (DDF).

NOTE: All animal procedures in this protocol are conducted with the approval of University of Florida Institutional Animal Care and Use Committee (IACUC) and are in compliance with the &#39;Guide for the Care and Use of Laboratory Animals&#39;.
1. Basic Experimental Set up Before Intermittent Hypoxia Administration
<ol>
	<li>Expose pups12 to the different gas mixes using a whole-body mouse plethysmograph chambers in much the same manner as adult rodents for other experimental purposes5,13,14. The chambers have a 4 inch diameter (volume = 450 ml), which is of ample size to accommodate 3-4 mouse pups or 1-2 rat pups. Here, AIH protocols are delivered to neonates aged postnatal day 1-8 (P1-P8).</li>
	<li>Use compressed air gas tanks to deliver the 21% &#8220;baseline&#8221; gas, which maintains chamber oxygenation at 21%. To achieve &#8220;relative hypoxia&#8221;, use a 10% oxygen/90% nitrogen gas tank. 
	NOTE: Plastic tubing (3/16&#8221; diameter) connects the gas tanks to a flow meter. Thus, the input to the flow meter consists of one tube each for baseline and hypoxia airflow.</li>
	<li>Configure the gas tubing as follows.
	<ol>
		<li>Run plastic tubing (1/8&#8221; diameter) from the flow meter to a bias flow regulator, which enables flows of 1 L/min to each chamber (i.e., 4 L/min if 4 chambers are used).</li>
		<li>Run plastic tubing (1/8&#8221; diameter) from the bias flow regulator to the plethysmography chambers. Airflow at 1 L/min to each chamber is a predetermined flow rate at which gas exchange is deemed to be non-stress-inducing to the animals based on physiological and behavioral observations.</li>
	</ol>
	</li>
	<li>Seal all unused connections to and from the bias flow unit and all unused openings to the chambers with caps so that no gas flow escapes to other chambers not in use, or out of the plethysmography chambers during the protocol.</li>
	<li>Place the chamber(s) into an incubator prior to putting animals in the chamber to allow equilibration to 37 &#176;C, or body temperature.</li>
</ol>
2. Calibration of Cycle Times for Intermittent Hypoxia
<ol>
	<li>Inspect all tubing, between air tanks and flow meter, flow meter and bias flow unit, and bias flow unit and plethysmography chamber(s) for proper connections. The connections are set up as described in Step 1. Verify the connection by a step-wise check of all described lines and closures: e.g., checking unused lines out of the bias flow unit and any chamber openings not in use.</li>
	<li>Connect an ambient O2 sensor with a hand-held O2 meter and then attach the sensor to the plethysmography chamber lid.</li>
	<li>Open both gas tanks and attach one pair of surgical, long handled hemostats insulated with plastic tubing to clamp the off-cycle flow of gas. In this way, only one gas tank at a time is delivering the 1 L/min gas flow per chamber. Clamp the &#8220;baseline&#8221; gas mix while the &#8220;hypoxic&#8221; gas mix is delivered to the chamber, and vice versa.</li>
	<li>Record the time required for the chamber O2 to reach the target levels of 10% and return to 21%. Utilize the recorded times for subsequent protocol delivery.</li>
</ol>
3. Administration of Acute Intermittent Hypoxia
<ol>
	<li>Inspect all tubing and connections as described in Step 2.1.</li>
	<li>Place neonates in the plethysmography chamber(s) and house the plethysmography chamber lids into the chamber base. Confirm a proper seal to the O-ring seal is as well as closure of any unused chamber connections. These steps are critical to ensuring the appropriate delivery of gas mixes.</li>
	<li>Place the chambers holding the pups to be treated into the 37 &#176;C incubator and close the door. Allow chamber to equilibrate to 37 &#176;C prior to starting the protocol. Maintain control animals at 37 &#176;C in the incubator at room air oxygenation.</li>
	<li>Open both gas tanks and use one pair of surgical, long handled hemostats insulated with plastic tubing to clamp the off-cycle flow of gas. In this way, only one gas tank at a time is delivering the 1 L/min gas flow per chamber.</li>
	<li>Use a hand-held timer to precisely time cycles and to indicate the time to switch the hemostats between tubes, thus resulting in the alternation of gas flow to the chambers.</li>
	<li>Record the completion of each cycle using a treatment log such as the one provided in Figure 1 to mark off all steps in the 2-step, 20 cycle protocol.</li>
	<li>Monitor the incubator temperature at every cycle change to ensure animals are maintained at the designated range (33-35 &#176;C, which is the setting on the incubator that results in 37 &#176;C).</li>
	<li>Closely monitor pup activity throughout the protocol to ensure that animals tolerate cycles without visible distress such as vocalizations, altered level of limb activity or rolling.</li>
</ol>
4. Isolation and Culture of Stem/Progenitor Cells from the Subventricular Zone
NOTE: The change in neurosphere formation following AIH compared to controls is an example of an endpoint that demonstrates the efficacy of this protocol to elicit tissue- and cellular-level changes.
<ol>
	<li>To isolate neurospheres forming cells, remove mouse or rat pups from the chamber immediately after AIH is completed. Sacrifice the animals according to IACUC protocols within 30 min of protocol termination.</li>
	<li>Harvest the SVZ tissue, place into neurosphere culture and conduct standard passage and expansion of derivative neurospheres, as previously published in methods chapters15,16 and a separate video protocol8.</li>
</ol>

<ol>
	<li>Studer, L., 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=Enhanced+proliferation,+survival,+and+dopaminergic+differentiation+of+CNS+precursors+in+lowered+oxygen.">Enhanced proliferation, survival, and dopaminergic differentiation of CNS precursors in lowered oxygen.</a> J Neurosci. 20 (19), 7377-7383 (2000).</li><li>Chen, H. L., 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=Oxygen+tension+regulates+survival+and+fate+of+mouse+central+nervous+system+precursors+at+multiple+levels.">Oxygen tension regulates survival and fate of mouse central nervous system precursors at multiple levels.</a> Stem Cells. 25 (9), 2291-2301 (2007).</li><li>Ling, L., 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=Chronic+intermittent+hypoxia+elicits+serotonin-dependent+plasticity+in+the+central+neural+control+of+breathing.">Chronic intermittent hypoxia elicits serotonin-dependent plasticity in the central neural control of breathing.</a> J Neurosci. 21 (14), 5381-5388 (2001).</li><li>Mitchell, G. 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=Invited+review:+Intermittent+hypoxia+and+respiratory+plasticity.">Invited review: Intermittent hypoxia and respiratory plasticity.</a> J Appl Physiol. 90 (6), 2466-2475 (2001).</li><li>Fuller, D. D., Zabka, A. G., Baker, T. L., Mitchell, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phrenic+long-term+facilitation+requires+5-HT+receptor+activation+during+but+not+following+episodic+hypoxia.">Phrenic long-term facilitation requires 5-HT receptor activation during but not following episodic hypoxia.</a> J Appl Physiol. 90 (5), 2001-2006 (2001).</li><li>Fuller, D. D., Johnson, S. M., Olson, E. B., Mitchell, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+pathways+to+phrenic+motoneurons+are+enhanced+by+chronic+intermittent+hypoxia+after+cervical+spinal+cord+injury.">Synaptic pathways to phrenic motoneurons are enhanced by chronic intermittent hypoxia after cervical spinal cord injury.</a> J Neurosci. 23 (7), 2993-3000 (2003).</li><li>Baker-Herman, T. L., 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=BDNF+is+necessary+and+sufficient+for+spinal+respiratory+plasticity+following+intermittent+hypoxia.">BDNF is necessary and sufficient for spinal respiratory plasticity following intermittent hypoxia.</a> Nat Neurosci. 7 (1), 48-55 (2004).</li><li>Zhu, L. 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The authors have nothing to disclose.

This work reports the development of a protocol to expose neonatal rodents to AIH. The parameters described here effectively alter in situ neural stem cell biology, which is observable over several rounds of cell passage. Specifically, AIH increases the number of non-adherent neurospheres, the expansion of cells within each neurosphere (refected by sphere diameter), the expansion of adherent NPC populations, and the presence of neuroblasts in both non-adherent and adherent populations. It should be emph...

The goal of this method is to reproducibly and effectively deliver intermittent bouts of systemic lowered ambient oxygen to neonatal rodents. The rationale for using intermittent hypoxia (IH) to manipulate stem cell biology originates from in vitro cell culture experiments in which O2 content of the growth media is altered. Specifically, when compared to &#8220;standard&#8221; conditions of 20% O2, extended culture of stem/progenitor cell populations cells in 3% O2 results in increased proliferation, decreased apoptosis and increased neuronal yield1,2.
This group has significant experience with the administration of systemic IH, and has conducted extensive studies on the role of IH in respiratory plasticity3-7. This work, and the recent finding that chronic IH increased neurogenesis in the rodent CNS8-10, forms the basis for the exploration of acute in vivo hypoxia as a preconditioning stimulus (i.e., prior to tissue harvest) on the subsequent culture of neural stem/progenitor cells (NPCs)11. Remarkably, when mouse pups were exposed to a brief (&#60;1 hr) period of acute intermittent hypoxia (AIH), cells that were harvested from the subventricular zone (SVZ) had significantly increased capacity for expansion as neurospheres or adherent monolayer cells. The AIH protocol was also associated with increased expression of a &#8220;neuronal fate&#8221; transcription factor (Pax6).
Accordingly, in vivo AIH protocols may provide a means to &#8220;prime&#8221; NPCs prior to culture. For example, applications for this approach could include expanding cell populations prior to transplantation into the injured central nervous system, or simply increasing the neuronal differentiation of cultured cells prior to in vitro experiments. Further, because this is a systemic delivery, any organ, tissue or cell is a candidate for similar study. Therefore, the protocol as written is potentially applicable to a wide range of studies on intermittent oxygen manipulation in small mammals.
There are certain advantages to this approach. In other published work, neonates were treated as a litter with the dam in hypobaric chambers, which allows for chronic dosing, less handling prior to treatment, and maintained maternal contact during treatment9. The current approach bypasses repeated treatments to a breeding female, or the use of a different dam for each experiment. This protocol also allows study of precise litter-matched and age-matched neonates. Representative data demonstrate another key strength of this protocol, namely the rapidity with which AIH, as delivered, elicits a powerful and consistent biological response in neural stem cell biology. This establishes a precedent for this protocol to elicit tissue- and cellular-level biological changes that alter cell biology.
This report will outline the detailed procedures used for exposing rodent pups to AIH as well as the population analysis of SVZ cells grown as neurospheres.

<table border="0" cellpadding="0" cellspacing="0" width="768">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Name of Material/ Equipment</td>
			<td style="width:147px;">Company</td>
			<td style="width:136px;">Catalog Number</td>
			<td style="width:243px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Mouse plethysmography chambers</td>
			<td style="width:147px;">Buxco</td>
			<td style="width:136px;">PLY4211</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Flow meter&#160;</td>
			<td style="width:147px;">Porter</td>
			<td style="width:136px;">F150</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Bias flow unit</td>
			<td style="width:147px;">AFPS</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Baseline Gas Mix</td>
			<td style="width:147px;">Airgas</td>
			<td style="width:136px;">AIZ300</td>
			<td>Compressed Air</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Hypoxic Gas Mix</td>
			<td style="width:147px;">Airgas</td>
			<td style="width:136px;">X03NI72C2000189</td>
			<td>10% Oxygen, balance nitrogen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Oxygen Meter</td>
			<td style="width:147px;">Teledyne</td>
			<td style="width:136px;">AX-300</td>
			<td></td>
		</tr>
	</tbody>
</table>

delivery of in vivo acute intermittent hypoxia in neonatal rodents to prime subventricular zone-derived neural progenitor cell cultures

Extended culture of neural stem/progenitor cells facilitates in vitro analyses to understand their biology while enabling expansion of cell populations to adequate numbers prior to transplantation. Identifying approaches to refine this process, to augment the production of all CNS cell types (i.e., neurons), and to possibly contribute to therapeutic cell therapy protocols is a high research priority. This report describes an easily applied in vivo &#8220;pre-conditioning&#8221; stimulus which can be delivered to awake, non-anesthetized animals. Thus, it is a non-invasive and non-stressful procedure. Specifically described are the procedures for exposing mouse or rat pups (aged postnatal day 1-8) to a brief (40-80 min) period of intermittent hypoxia (AIH). The procedures included in this video protocol include calibration of the whole-body plethysmography chamber in which pups are placed during AIH and the technical details of AIH exposure. The efficacy of this approach to elicit tissue-level changes in the awake animal is demonstrated through the enhancement of subsequent in vitro expansion and neuronal differentiation in cells harvested from the subventricular zone (SVZ). These results support the notion that tissue level changes across multiple systems could be observed following AIH, and support the continued optimization and establishment of AIH as a priming or conditioning modality for therapeutic cell populations.

The initial experiments, based on historical data, were conducted using 1 min cycle lengths. Based on the subsequent calibrations performed in Step 2 above, it was determined that the O2 level in the chamber was 13% at 1 min post-hypoxia flushing and, that it took a similar time to return to the 21% baseline. However, a 2 min&#160;cycle was sufficient to both achieve 10% oxygen and a return to 21% during the &#8220;baseline&#8221; cycle. Subsequently, 2 min cycle lengths have been used. The protocol duration c...

Watch this Scientific Journal Video about Delivery of In Vivo Acute Intermittent Hypoxia in Neonatal Rodents to Prime Subventricular Zone-derived Neural Progenitor Cell Cultures at JoVE.com

Delivery of In Vivo Acute Intermittent Hypoxia in Neonatal Rodents to Prime Subventricular Zone-derived Neural Progenitor Cell Cultures

This article describes the methodology for administering short periods of intermittent hypoxia to postnatal day 1-8 mouse or rat pups. This approach effectively elicits a robust tissue level &#8220;priming effect&#8221; on cultured neural progenitor cells that are harvested within 30 min of hypoxia exposure.

Delivery of In Vivo Acute Intermittent Hypoxia in Neonatal Rodents to Prime Subventricular Zone-derived Neural Progenitor Cell Cultures

Extended culture of neural stem/progenitor cells facilitates in vitro analyses to understand their biology while enabling expansion of cell populations to ...

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7.2K Views.  University of Florida. This article describes the methodology for administering short periods of intermittent hypoxia to postnatal day 1-8 mouse or rat pups. This approach effectively elicits a robust tissue level “priming effect” on cultured neural progenitor cells that are harvested within 30 min of hypoxia exposure.

Video: Delivery of In Vivo Acute Intermittent Hypoxia in Neonatal Rodents to Prime Subventricular Zone-derived Neural Progenitor Cell Cultures

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

Understanding the genetic programs underlying neural development is an important goal of developmental and stem cell biology. In the amphibian blastula, cells from the roof of the blastocoel are pluripotent. These cells can be isolated, and programmed to generate various tissues through manipulation of genes expression or induction by morphogens. In this manuscript protocols are described for the use of Xenopus laevis blastocoel roof explants as an assay system to investigate key in vivo and in vitro features of early neural development. These protocols allow the investigation of fate acquisition, cell migration behaviors, and cell autonomous and non-autonomous properties. The blastocoel roof explants can be cultured in a serum-free defined medium and grafted into host embryos. This transplantation into an embryo allows the investigation of the long-term lineage commitment, the inductive properties, and the behavior of transplanted cells in vivo. These assays can be exploited to investigate molecular mechanisms, cellular processes and gene regulatory networks underlying neural development. In the context of regenerative medicine, these assays provide a means to generate neural-derived cell types in vitro that could be used in drug screening.

Stem cell-like Xenopus Embryonic Explants to Study Early Neural Developmental Features In Vitro and In Vivo

In Xenopus embryos, cells from the roof of the blastocoel are pluripotent and can be programmed to generate various tissues. Here, we describe protocols to use amphibian blastocoel roof explants as an assay system to investigate key in vivo and in vitro features of early neural development.

Understanding the genetic programs underlying neural development is an important goal of developmental and stem cell biology. In the amphibian blastula, ...

Initiating Differentiation in Immortalized Multipotent Otic Progenitor Cells

Use of human induced pluripotent stem cells (iPSC) or embryonic stem cells (ESC) for cell replacement therapies holds great promise. Several limitations including low yields and heterogeneous populations of differentiated cells hinder the progress of stem cell therapies. A fate restricted immortalized multipotent otic progenitor (iMOP) cell line was generated to facilitate efficient differentiation of large numbers of functional hair cells and spiral ganglion neurons (SGN) for inner ear cell replacement therapies. Starting from dissociated cultures of single iMOP cells, protocols that promote cell cycle exit and differentiation by basic fibroblast growth factor (bFGF) withdrawal were described. A significant decrease in proliferating cells after bFGF withdrawal was confirmed using an EdU cell proliferation assay. Concomitant with a decrease in proliferation, successful differentiation resulted in expression of molecular markers and morphological changes. Immunostaining of Cdkn1b (p27KIP) and Cdh1 (E-cadherin) in iMOP-derived otospheres was used as an indicator for differentiation into inner ear sensory epithelia while immunostaining of Cdkn1b and Tubb3 (neuronal &#946;-tubulin) was used to identify iMOP-derived neurons. Use of iMOP cells provides an important tool for understanding cell fate decisions made by inner ear neurosensory progenitors and will help develop protocols for generating large numbers of iPSC or ESC-derived hair cells and SGNs. These methods will accelerate efforts for generating otic cells for replacement therapies.

The current protocols to maintain immortalized multipotent otic progenitor (iMOP) cells and otic differentiation are described. Culture conditions and molecular markers that indicate differentiation into sensory epithelia and spiral ganglion neurons (SGN) are highlighted.

Use of human induced pluripotent stem cells (iPSC) or embryonic stem cells (ESC) for cell replacement therapies holds great promise. Several limitations ...

Technique to Target Microinjection to the Developing Xenopus Kidney

The embryonic kidney of Xenopus&#160;laevis (frog), the pronephros, consists of a single nephron, and can be used as a model for kidney disease. Xenopus embryos are large, develop externally, and can be easily manipulated by microinjection or surgical procedures. In addition, fate maps have been established for early Xenopus embryos. Targeted microinjection into the individual blastomere that will eventually give rise to an organ or tissue of interest can be used to selectively overexpress or knock down gene expression within this restricted region, decreasing secondary effects in the rest of the developing embryo. In this protocol, we describe how to utilize established Xenopus fate maps to target the developing Xenopus kidney (the pronephros), through microinjection into specific blastomere of 4- and 8-cell embryos. Injection of lineage tracers allows verification of the specific targeting of the injection. After embryos have developed to stage 38 - 40, whole-mount immunostaining is used to visualize pronephric development, and the contribution by targeted cells to the pronephros can be assessed. The same technique can be adapted to target other tissue types in addition to the pronephros.

Technique to Target Microinjection to the Developing Xenopus Kidney

Here, we present a protocol to use fate maps and lineage tracers to target injections into individual blastomeres that give rise to the kidney of Xenopus laevis embryos.

The embryonic kidney of Xenopus&#160;laevis (frog), the pronephros, consists of a single nephron, and can be used as a model for kidney disease. Xenopus ...

Using Primary Neurosphere Cultures to Study Primary Cilia

The primary cilium is fundamentally important for the proliferation of neural stem/progenitor cells and for neuronal differentiation during embryonic, postnatal, and adult life. In addition, most differentiated neurons possess primary cilia that house signaling receptors, such as G-protein-coupled receptors, and signaling molecules, such as adenylyl cyclases. The primary cilium determines the activity of multiple developmental pathways, including the sonic hedgehog pathway during embryonic neuronal development, and also functions in promoting compartmentalized subcellular signaling during adult neuronal function. Unsurprisingly, defects in primary cilium biogenesis and function have been linked to developmental anomalies of the brain, central obesity, and learning and memory deficits. Thus, it is imperative to study primary cilium biogenesis and ciliary trafficking in the context of neural stem/progenitor cells and differentiated neurons. However, culturing methods for primary neurons require considerable expertise and are not amenable to freeze-thaw cycles. In this protocol, we discuss culturing methods for mixed populations of neural stem/progenitor cells using primary neurospheres. The neurosphere-based culturing methods provide the combined benefits of studying primary neural stem/progenitor cells: amenability to multiple passages and freeze-thaw cycles, differentiation potential into neurons/glia, and transfectability. Importantly, we determined that neurosphere-derived neural stem/progenitor cells and differentiated neurons are ciliated in culture and localize signaling molecules relevant to ciliary function in these compartments. Utilizing these cultures, we further describe methods to study ciliogenesis and ciliary trafficking in neural stem/progenitor cells and differentiated neurons. These neurosphere-based methods allow us to study cilia-regulated cellular pathways, including G-protein-coupled receptor and sonic hedgehog signaling, in the context of neural stem/progenitor cells and differentiated neurons.

The primary cilium is fundamentally important in neural progenitor cell proliferation, neuronal differentiation, and adult neuronal function. Here, we describe a method to study ciliogenesis and the trafficking of signaling proteins to cilia in neural stem/progenitor cells and differentiated neurons using primary neurosphere cultures.

The primary cilium is fundamentally important for the proliferation of neural stem/progenitor cells and for neuronal differentiation during embryonic, ...

Induction of Hypoxia in Living Frog and Zebrafish Embryos

Here, we introduce a novel system for hypoxia induction, which we developed to study the effects of hypoxia in aquatic organisms such as frog and zebrafish embryos. Our system comprises a chamber featuring a simple setup that is nevertheless robust to induce and maintain a specific oxygen concentration and temperature in any experimental solution of choice. The presented system is very cost-effective but highly functional, it allows induction and sustainment of hypoxia for direct experiments in vivo and for various time periods up to 48 h.
To monitor and study the effects of hypoxia, we have employed two methods - measurement of levels of hypoxia-inducible factor 1alpha (HIF-1&#945;) in whole embryos or specific tissues and determination of retinal stem cell proliferation by 5-ethynyl-2&#8242;-deoxyuridine (EdU) incorporation into the DNA. HIF-1&#945; levels can serve as a general hypoxia marker in the whole embryo or tissue of choice, here embryonic retina. EdU incorporation into the proliferating cells of embryonic retina is a specific output of hypoxia induction. Thus, we have shown that hypoxic embryonic retinal progenitors decrease proliferation within 1 h of incubation under 5% oxygen of both frog and zebrafish embryos.
Once mastered, our setup can be employed for use with small aquatic model organisms, for direct in vivo experiments, any given time period and under normal, hypoxic or hyperoxic oxygen concentration or under any other given gas mixture.

We introduce a novel hypoxic chamber system for use with aquatic organisms such as frog and zebrafish embryos. Our system is simple, robust, cost-effective and allows the induction and sustainment of hypoxia in vivo and for up to 48 h. We present 2 reproducible methods to monitor the effectiveness of hypoxia.

Here, we introduce a novel system for hypoxia induction, which we developed to study the effects of hypoxia in aquatic organisms such as frog and ...

A Novel Mammary Fat Pad Transplantation Technique to Visualize the Vessel Generation of Vascular Endothelial Stem Cells

Endothelial cells (ECs) are the fundamental building blocks of the vascular architecture and mediate vascular growth and remodeling to ensure proper vessel development and homeostasis. However, studies on endothelial lineage hierarchy remain elusive due to the lack of tools to gain access as well as to directly evaluate their behavior in vivo. To address this shortcoming, a new tissue model to study angiogenesis using the mammary fat pad has been developed. The mammary gland develops mostly in the postnatal stages, including puberty and pregnancy, during which robust epithelium proliferation is accompanied by extensive vascular remodeling. Mammary fat pads provide space, matrix, and rich angiogenic stimuli from the growing mammary epithelium. Furthermore, mammary fat pads are located outside the peritoneal cavity, making them an easily accessible grafting site for assessing the angiogenic potential of exogenous cells. This work also describes an efficient tracing approach using fluorescent reporter mice to specifically label the targeted population of vascular endothelial stem cells (VESCs) in vivo. This lineage tracing method, coupled with subsequent tissue whole-mount microscopy, enable the direct visualization of targeted cells and their descendants, through which the proliferation capability can be quantified and the differentiation commitment can be fate-mapped. Using these methods, a population of bipotent protein C receptor (Procr) expressing VESCs has recently been identified in multiple vascular systems. Procr+ VESCs, giving rise to both new ECs and pericytes, actively contribute to angiogenesis during development, homeostasis, and injury repair. Overall, this manuscript describes a new mammary fat pad transplantation and in vivo lineage tracing techniques that can be used to evaluate the stem cell properties of VESCs.

This work demonstrates a novel approach to assess the proliferation, differentiation, and vessel-forming potential of vascular endothelial stem cells (VESCs) through mammary fat pad transplantation followed by whole-mount tissue preparation for microscopic observation. A lineage tracing strategy to investigate the behavior of VESCs in vivo is also presented.

Endothelial cells (ECs) are the fundamental building blocks of the vascular architecture and mediate vascular growth and remodeling to ensure proper ...

Quantitative Whole-mount Immunofluorescence Analysis of Cardiac Progenitor Populations in Mouse Embryos

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development and organogenesis are two areas of research that have benefitted greatly from these advances, due to the high quality of data that can be obtained directly from imaging pre-implantation embryos or ex vivo organs. While pre-implantation embryos have yielded data with especially high spatial resolution, later stages have been less amenable to three-dimensional reconstruction. Obtaining high-quality 3D or volumetric data for known embryonic structures in combination with fate mapping or genetic lineage tracing will allow for a more comprehensive analysis of the morphogenetic events taking place during embryogenesis.
This protocol describes a whole-mount immunofluorescence approach that allows for the labeling, visualization, and quantification of progenitor cell populations within the developing cardiac crescent, a key structure formed during heart development. The approach is designed in such a way that both cell- and tissue-level information can be obtained. Using confocal microscopy and image processing, this protocol allows for three-dimensional spatial reconstruction of the cardiac crescent, thereby providing the ability to analyze the localization and organization of specific progenitor populations during this critical phase of heart development. Importantly, the use of reference antibodies allows for successive masking of the cardiac crescent and subsequent quantitative measurements of areas within the crescent. This protocol will not only enable a detailed examination of early heart development, but with adaptations should be applicable to most organ systems in the gastrula to early somite stage mouse embryo.

Here, we describe a protocol for whole mount immunofluorescence and image-based quantitative volumetric analysis of early stage mouse embryos. We present this technique as a powerful approach to qualitatively and quantitatively assess cardiac structures during development, and propose that it may be widely adaptable to other organ systems.

The use of ever-advancing imaging techniques has contributed broadly to our increased understanding of embryonic development. Pre-implantation development ...

Cell Aggregation Assays to Evaluate the Binding of the Drosophila Notch with Trans-Ligands and its Inhibition by Cis-Ligands

Notch signaling is an evolutionarily conserved cell-cell communication system used broadly in animal development and adult maintenance. Interaction of the Notch receptor with ligands from neighboring cells induces activation of the signaling pathway (trans-activation), while interaction with ligands from the same cell inhibits signaling (cis-inhibition). Proper balance between trans-activation and cis-inhibition helps establish optimal levels of Notch signaling in some contexts during animal development. Because of the overlapping expression domains of Notch and its ligands in many cell types and the existence of feedback mechanisms, studying the effects of a given post-translational modification on trans- versus cis-interactions of Notch and its ligands in vivo is difficult. Here, we describe a protocol for using Drosophila S2 cells in cell-aggregation assays to assess the effects of knocking down a Notch pathway modifier on the binding of Notch to each ligand in trans and in cis. S2 cells stably or transiently transfected with a Notch-expressing vector are mixed with cells expressing each Notch ligand (S2-Delta or S2-Serrate). Trans-binding between the receptor and ligands results in the formation of heterotypic cell aggregates and is measured in terms of the number of aggregates per mL composed of &#62;6 cells. To examine the inhibitory effect of cis-ligands, S2 cells co-expressing Notch and each ligand are mixed with S2-Delta or S2-Serrate cells and the number of aggregates is quantified as described above. The relative decrease in the number of aggregates due to the presence of cis-ligands provides a measure of cis-ligand-mediated inhibition of trans-binding. These straightforward assays can provide semi-quantitative data on the effects of genetic or pharmacological manipulations on the binding of Notch to its ligands, and can help deciphering the molecular mechanisms underlying the in vivo effects of such manipulations on Notch signaling.

Cell Aggregation Assays to Evaluate the Binding of the Drosophila Notch with Trans-Ligands and its Inhibition by Cis-Ligands

Complexity of in vivo systems makes it difficult to distinguish between the activation and inhibition of Notch receptor by trans- and cis-ligands, respectively. Here, we present a protocol based on in vitro cell-aggregation assays for qualitative and semi-quantitative evaluation of the binding of Drosophila Notch to trans-ligands vs cis-ligands.

Notch signaling is an evolutionarily conserved cell-cell communication system used broadly in animal development and adult maintenance. Interaction of the ...

Real-time Live-cell Flow Cytometry to Investigate Calcium Influx, Pore Formation, and Phagocytosis by P2X7 Receptors in Adult Neural Progenitor Cells

Live-cell flow cytometry is increasingly used among cell biologists to quantify biological processes in a living cell culture. This protocol describes a method whereby live-cell flow cytometry is extended upon to analyze the multiple functions of P2X7 receptor activation in real-time. Using a time module installed on a flow cytometer, live-cell functionality can be assessed and plotted over a given time period to explore the kinetics of calcium influx, transmembrane pore formation, and phagocytosis. This simple method is advantageous as all three canonical functions of the P2X7 receptor can be assessed using one machine, and the gathered data plotted over time provides information on the entire live-cell population rather than single-cell recordings often obtained using technically challenging patch-clamp methods. Calcium influx experiments use a calcium indicator dye, while P2X7 pore formation assays rely on ethidium bromide being allowed to pass through the transmembrane pore formed upon high agonist concentrations. Yellow-green (YG) latex beads are utilized to measure phagocytosis. Specific agonists and antagonists are applied to investigate the effects of P2X7 receptor activity. Individually, these methods can be modified to provide quantitative data on any number of calcium channels and purinergic and scavenger receptors. Taken together, they highlight how the use of real-time live-cell flow cytometry is a rapid, cost-effective, reproducible, and quantifiable method to investigate P2X7 receptor function.

Providing single-cell sensitivity, real-time flow cytometry is uniquely suited to quantify multimodal receptor functions of live cultures. Using adult neural progenitor cells, the P2X7 receptor function was assessed via calcium influx detected by calcium indicator dye, transmembrane pore formation by ethidium bromide uptake, and phagocytosis using fluorescent latex beads.

Live-cell flow cytometry is increasingly used among cell biologists to quantify biological processes in a living cell culture. This protocol describes a ...

Controlled Cortical Impact Model of Mouse Brain Injury with Therapeutic Transplantation of Human Induced Pluripotent Stem Cell-Derived Neural Cells

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Disease pathology due to TBI progresses from the primary mechanical insult to secondary injury processes, including apoptosis and inflammation. Animal modeling has been valuable in the search to unravel injury mechanisms and evaluate potential neuroprotective therapies. This protocol describes the controlled cortical impact (CCI) model of focal, open-head TBI. Specifically, parameters for producing a mild unilateral cortical injury are described. Behavioral consequences of CCI are analyzed using the adhesive tape removal test of bilateral sensorimotor integration. Regarding experimental therapy for TBI pathology, this protocol also illustrates a process for transplanting cultured cells into the brain. Neural cell cultures derived from human induced pluripotent stem cells (hiPSCs) were chosen for their potential to show superior functional restoration in human TBI patients. Chronic survival of hiPSCs in the host mouse brain tissue is detected using a modified DAB immunohistochemical process.

This protocol demonstrates methodologies for a mouse model of open-skull traumatic brain injury and transplantation of cultured human induced pluripotent stem cell-derived cells into the injury site. Behavioral and histologic tests of outcomes from these procedures are also described in brief.

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Disease pathology due to TBI progresses from the primary mechanical ...