The authors would like to thank Nora Lakes for proofreading. Research reported in this manuscript was supported by the National Heart, Lung, and Blood Institute, under Award Number R01 HL117952 (E.B.), part of the National Institutes of Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

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	<li>Dompmartin, A., Vikkula, M., Boon, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Venous+malformation:+update+on+aetiopathogenesis,+diagnosis+and+management.">Venous malformation: update on aetiopathogenesis, diagnosis and management.</a> Phlebology: The Journal of Venous Disease. 25 (5), 224-235 (2010).</li><li>Limaye, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Somatic+mutations+in+angiopoietin+receptor+gene+TEK+cause+solitary+and+multiple+sporadic+venous+malformations.">Somatic mutations in angiopoietin receptor gene TEK cause solitary and multiple sporadic venous malformations.</a> Nature Genetics. 41 (1), 118-124 (2009).</li><li>Castel, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Somatic+PIK3CA+mutations+as+a+driver+of+sporadic+venous+malformations.">Somatic PIK3CA mutations as a driver of sporadic venous malformations.</a> Science Translational Medicine. 8 (332), 42 (2016).</li><li>Limaye, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Somatic+Activating+PIK3CA+Mutations+Cause+Venous+Malformation.">Somatic Activating PIK3CA Mutations Cause Venous Malformation.</a> The American Journal of Human Genetics. 97 (6), 914-921 (2015).</li><li>Castillo, S. D., 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=Somatic+activating+mutations+in+Pik3ca+cause+sporadic+venous+malformations+in+mice+and+humans.">Somatic activating mutations in Pik3ca cause sporadic venous malformations in mice and humans.</a> Science Translational Medicine. 8 (332), 43 (2016).</li><li>Stratman, A. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+cell+lumen+and+vascular+guidance+tunnel+formation+requires+MT1-MMP-dependent+proteolysis+in+3-dimensional+collagen+matrices.">Endothelial cell lumen and vascular guidance tunnel formation requires MT1-MMP-dependent proteolysis in 3-dimensional collagen matrices.</a> Blood. 114 (2), 237-247 (2009).</li><li>Okada, S., Vaeteewoottacharn, K., Kariya, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+Highly+Immunocompromised+Mice+for+the+Establishment+of+Patient-Derived+Xenograft+(PDX)+Models.">Application of Highly Immunocompromised Mice for the Establishment of Patient-Derived Xenograft (PDX) Models.</a> Cells. 8 (8), 889 (2019).</li><li>Byrne, A. T., 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=Interrogating+open+issues+in+cancer+precision+medicine+with+patient-derived+xenografts.">Interrogating open issues in cancer precision medicine with patient-derived xenografts.</a> Nature Reviews Cancer. 17 (4), 254-268 (2017).</li><li>Allen, P., Melero-Martin, J., Bischoff, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Type+I+collagen,+fibrin+and+PuraMatrix+matrices+provide+permissive+environments+for+human+endothelial+and+mesenchymal+progenitor+cells+to+form+neovascular+networks.">Type I collagen, fibrin and PuraMatrix matrices provide permissive environments for human endothelial and mesenchymal progenitor cells to form neovascular networks.</a> Journal of Tissue Engineering and Regenerative Medicine. 5 (4), 74 (2011).</li><li>Allen, P., Kang, K. T., Bischoff, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+onset+of+perfused+blood+vessels+after+implantation+of+ECFCs+and+MPCs+in+collagen,+PuraMatrix+and+fibrin+provisional+matrices.">Rapid onset of perfused blood vessels after implantation of ECFCs and MPCs in collagen, PuraMatrix and fibrin provisional matrices.</a> Journal of Tissue Engineering and Regenerative. 9 (5), 632-636 (2015).</li><li>Nowak-Sliwinska, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consensus+guidelines+for+the+use+and+interpretation+of+angiogenesis+assays.">Consensus guidelines for the use and interpretation of angiogenesis assays.</a> Angiogenesis. 21 (3), 425 (2018).</li><li>Roh, Y. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+results+of+surgical+treatment+for+patients+with+venous+malformations.">The results of surgical treatment for patients with venous malformations.</a> Annals of Vascular Surgery. 26 (5), 665-673 (2012).</li><li>Marler, J. J., Mulliken, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+management+of+hemangiomas+and+vascular+malformations.">Current management of hemangiomas and vascular malformations.</a> Clinics in Plastic Surgery. 32 (1), 99-116 (2005).</li><li>Goines, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+xenograft+model+for+venous+malformation.">A xenograft model for venous malformation.</a> Angiogenesis. 21 (4), 725-735 (2018).</li><li>Li, X., 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=Ponatinib+Combined+With+Rapamycin+Causes+Regression+of+Murine+Venous+Malformation.">Ponatinib Combined With Rapamycin Causes Regression of Murine Venous Malformation.</a> Arteriosclerosis, thrombosis, and vascular biology. 39 (3), 496-512 (2019).</li><li>Le Cras, T. D., 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=Constitutively+active+PIK3CA+mutations+are+expressed+by+lymphatic+and+vascular+endothelial+cells+in+capillary+lymphatic+venous+malformation.">Constitutively active PIK3CA mutations are expressed by lymphatic and vascular endothelial cells in capillary lymphatic venous malformation.</a> Angiogenesis. , 1-18 (2020).</li><li>Boscolo, E., 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=Rapamycin+improves+TIE2-mutated+venous+malformation+in+murine+model+and+human+subjects.">Rapamycin improves TIE2-mutated venous malformation in murine model and human subjects.</a> Journal of Clinical Investigation. 125 (9), 3491-3504 (2015).</li></ol>

The authors have no conflicts-of-interests to disclose.

Here, we describe a method to generate a patient-derived xenograft model of VM. This murine model presents an excellent system that allows researchers to gain a deeper understanding of pathological lumen enlargement and will be instrumental in developing more effective and targeted therapies for the treatment of VM. This can be easily adapted to investigate other types of vascular anomalies such as capillary lymphatic venous malformation16. There are several steps that are crucial for the successf...

Defects in the development of the vasculature are the underlying cause of many diseases including venous malformation (VM). VM is a congenital disease characterized by abnormal morphogenesis and expansion of veins1. Important studies on VM tissue and endothelial cells (EC) have identified gain-of-function mutations in two genes: TEK, which encodes the tyrosine kinase receptor TIE2, and PIK3CA, which encodes the p110&#945; (catalytic subunit) isoform of PI3-kinase (PI3K)2,3,4,5. These somatic mutations result in ligand-independent hyper-activation of key angiogenic/growth signaling pathways, including PI3K/AKT, thereby resulting in dilated ectatic veins3. Despite these important genetic discoveries, the subsequent cellular and molecular mechanisms triggering abnormal angiogenesis and the formation of enlarged vascular channels are still not fully understood.
During normal and pathological angiogenesis, new vessels sprout from a pre-existing vascular network and EC undergo a sequence of important cellular processes including proliferation, migration, extracellular matrix (ECM) remodeling and lumen formation6. Two- and three- dimensional (2D/3D) in vitro cultures of EC are important tools to investigate each of these cellular properties individually. Nevertheless, there is a clear demand for a mouse model recapitulating pathological vessel enlargement within the host microenvironment while providing an efficient platform for preclinical evaluation of targeted drugs for translational research.
Up to date, a transgenic murine model of VM associated with TIE2 gain-of-function mutations has not been reported. Current transgenic VM mouse models rely on the ubiquitous or tissue-restricted expression of the activating mutation PIK3CA p.H1047R3,5. These transgenic animals provide significant insight into whole-body or tissue-specific effects of this hotspot PIK3CA mutation. The limitation of these models is the formation of a highly pathological vascular network resulting in early lethality. Thus, these mouse models do not fully reflect the sporadic occurrence of mutational events and localized nature of VM pathology.
On the contrary, patient-derived xenograft models are based on the transplantation or injection of pathological tissue or cells derived from patients into immunodeficient mice7. Xenograft models are a powerful tool to broaden knowledge about disease development and discovery of novel therapeutic agents8. In addition, using patient-derived cells allows scientists to recapitulate mutation heterogeneity to study the spectrum of patient phenotypes.
Here, we describe a protocol where patient-derived VM EC which express a mutant constitutively-active form of TIE2 and/or PIK3CA are injected subcutaneously in the back of athymic nude mice. Injected vascular cells are suspended in an ECM framework in order to promote angiogenesis as described in previous vascular xenograft models9,10,11. These VM EC undergo significant morphogenesis and generate enlarged, perfused pathological vessels in the absence of supporting cells. The described xenograft model of VM provides an efficient platform for preclinical evaluation of targeted drugs for their ability to inhibit uncontrolled lumen expansion.

<table>
	<tbody>
		<tr>
			<td>Athymic nude mice, (Foxn1-nu); 5-6 weeks, males</td>
			<td>Envigo</td>
			<td>069(nu)/070(nu/+)</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>Biotinylated Ulex europeaus Agglutinin-I (UEA-I)</td>
			<td>Vector Laboratories</td>
			<td>B-1065</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Bottle top filter (500 ml; 0.2 &#181;M)</td>
			<td>Thermo Fisher</td>
			<td>974106</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td>BSA</td>
			<td>A7906-50MG</td>
			<td>Cell culture; Histological analysis</td>
		</tr>
		<tr>
			<td>Calcium cloride dihydrate (CaCl2.2H2O)</td>
			<td>Sigma</td>
			<td>C7902-500G</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Caliper</td>
			<td>Electron Microscopy Sciences</td>
			<td>50996491</td>
			<td>Lesion plug measurment</td>
		</tr>
		<tr>
			<td>CD31-conjugated magnetic beads (Dynabeads)</td>
			<td>Life Technologies</td>
			<td>11155D</td>
			<td>EC separation</td>
		</tr>
		<tr>
			<td>Cell strainer (100 &#956;M)</td>
			<td>Greiner</td>
			<td>542000</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Collagenase A</td>
			<td>Roche</td>
			<td>10103578001</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Conical Tube; polypropylene (15 mL)</td>
			<td>Greiner</td>
			<td>07 000 241</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Conical Tube; polypropylene (50 mL)</td>
			<td>Greiner</td>
			<td>07 000 239</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Coplin staining jar</td>
			<td>Ted Pella</td>
			<td>21029</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Coverglass (50 X 22 mm)</td>
			<td>Fisher Scientific</td>
			<td>12545E</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>DAB: 3,3&#39;Diaminobenzidine Reagent (ImmPACT DAB)</td>
			<td>Vector Laboratories</td>
			<td>SK-4105</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modification of Eagle&#39;s Medium (DMEM)</td>
			<td>Corning</td>
			<td>10-027-CV</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>DynaMag-2</td>
			<td>Life Technologies</td>
			<td>12321D</td>
			<td>EC separation</td>
		</tr>
		<tr>
			<td>Ear punch</td>
			<td>VWR</td>
			<td>10806-286</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>EDTA (0.5M, pH 8.0)</td>
			<td>Life Technologies</td>
			<td>15575-020</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Endothelial Cell Growth Medium-2 (EGM2) Bulletkit (basal medium and supplements)</td>
			<td>Lonza</td>
			<td>CC-3162</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Eosin Y (alcohol-based)</td>
			<td>Thermo Scientific</td>
			<td>71211</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Decon Labs</td>
			<td>2716</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS) , HyClone</td>
			<td>GE Healthcare</td>
			<td>SH30910.03</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Filter tip 1,250 &#956;L</td>
			<td>MidSci</td>
			<td>AV1250-H</td>
			<td>Multiple steps</td>
		</tr>
		<tr>
			<td>Filter tip 20 &#956;L</td>
			<td>VWR</td>
			<td>10017-064</td>
			<td>Multiple steps</td>
		</tr>
		<tr>
			<td>Filter tip 200 &#956;L</td>
			<td>VWR</td>
			<td>10017-068</td>
			<td>Multiple steps</td>
		</tr>
		<tr>
			<td>Formalin buffered solution (10%)</td>
			<td>Sigma</td>
			<td>F04586</td>
			<td>Lesion plug dissection</td>
		</tr>
		<tr>
			<td>Hemacytometer (INCYTO; Disposable)</td>
			<td>SKC FILMS</td>
			<td>DHCN015</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Hematoxylin</td>
			<td>Vector Hematoxylin</td>
			<td>H-3401</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Human plasma fibronectin purified protein (1mg/mL)</td>
			<td>Sigma</td>
			<td>FC010-10MG</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Hydrogen Peroxide solution (30% w/w)</td>
			<td>Sigma</td>
			<td>H1009</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>ImageJ Software</td>
			<td></td>
			<td></td>
			<td>Analysis</td>
		</tr>
		<tr>
			<td>Isoflurane, USP</td>
			<td>Akorn Animal Health</td>
			<td>59399-106-01</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>magnesium sulfate heptahydrate (MgSO4.7H2O)</td>
			<td>Sigma</td>
			<td>M1880-500G</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Basement Membrane Matrix (Phenol Red-Free; LDEV-free)</td>
			<td>Corning</td>
			<td>356237</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>Microcentrifuge tube (1.5 mL)</td>
			<td>VWR</td>
			<td>87003-294</td>
			<td>EC separation</td>
		</tr>
		<tr>
			<td>Microscope Slide Superfrost (75mm X 25mm)</td>
			<td>Fisher Scientific</td>
			<td>1255015-CS</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Needles, 26G x 5/8 inch Sub-Q sterile needles</td>
			<td>Becton Dickinson (BD)</td>
			<td>BD305115</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>Normal horse serum</td>
			<td>Vector Laboratories</td>
			<td>S-2000</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin-L-Glutamine (100X)</td>
			<td>Corning</td>
			<td>30-009-CI</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Permanent mounting medium (VectaMount)</td>
			<td>Vector Laboratories</td>
			<td>H-5000</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Pestle Size C, Plain</td>
			<td>Thomas Scientific</td>
			<td>3431F55</td>
			<td>EC isolation</td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS)</td>
			<td>Fisher Scientific</td>
			<td>BP3994</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Scale</td>
			<td>VWR</td>
			<td>65500-202</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>Serological pipettes (10 ml)</td>
			<td>VWR</td>
			<td>89130-898</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Serological pipettes (5ml)</td>
			<td>VWR</td>
			<td>89130-896</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Sodium carbonate (Na2CO3)</td>
			<td>Sigma</td>
			<td>223530</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Streptavidin, Horseradish Peroxidase, Concentrate, for IHC</td>
			<td>Vector Laboratories</td>
			<td>SA-5004</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Syringe (60ml)</td>
			<td>BD Biosciences</td>
			<td>309653</td>
			<td>Cel culture</td>
		</tr>
		<tr>
			<td>SYRINGE FILTER (0.2 &#181;M)</td>
			<td>Corning</td>
			<td>431219</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Syringes (1 mL with Luer Lock)</td>
			<td>Becton Dickinson (BD)</td>
			<td>BD-309628</td>
			<td>Subcutaneous injection</td>
		</tr>
		<tr>
			<td>Tissue culture-treated plate (100 X 20 mm)</td>
			<td>Greiner</td>
			<td>664160</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Tissue culture-treated plate (145X20 mm)</td>
			<td>Greiner</td>
			<td>639160</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Tissue culture-treated plates (60 X 15) mm</td>
			<td>Eppendorf</td>
			<td>30701119</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Tris-base (Trizma base)</td>
			<td>Sigma</td>
			<td>T6066</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Trypan Blue Solution (0.4 %)</td>
			<td>Life Technologies</td>
			<td>15250061</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Trypsin EDTA, 1X (0.05% Trypsin/0.53mM EDTA)</td>
			<td>Corning</td>
			<td>25-052-Cl</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Biorad</td>
			<td>170-6531</td>
			<td>Histological anlaysis</td>
		</tr>
		<tr>
			<td>Wheaton bottle</td>
			<td>VWR</td>
			<td>16159-798</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Xylenes</td>
			<td>Fisher Scientific</td>
			<td>X3P-1GAL</td>
			<td>Histological anlaysis</td>
		</tr>
	</tbody>
</table>

a patient-derived xenograft model for venous malformation

Venous malformation (VM) is a vascular anomaly that arises from impaired development of the venous network resulting in dilated and often dysfunctional veins. The purpose of this article is to carefully describe the establishment of a murine xenograft model that mimics human VM and is able to reflect patient heterogeneity. Hyper-activating non-inherited (somatic) TEK (TIE2) and PIK3CA mutations in endothelial cells (EC) have been identified as the main drivers of pathological vessel enlargement in VM. The following protocol describes the isolation, purification and expansion of patient-derived EC expressing mutant TIE2 and/or PIK3CA. These EC are injected subcutaneously into the back of immunodeficient athymic mice to generate ectatic vascular channels. Lesions generated with TIE2 or PIK3CA-mutant EC are visibly vascularized within 7&#8210;9 days of injection and recapitulate histopathological features of VM patient tissue. This VM xenograft model provides a reliable platform to investigate the cellular and molecular mechanisms driving VM formation and expansion. In addition, this model will be instrumental for translational studies testing the efficacy of novel drug candidates in preventing the abnormal vessel enlargement seen in human VM.

This protocol describes the process of generating a murine xenograft model of VM based on the subcutaneous injection of patient-derived EC into the back of immunodeficient nude mice. Endothelial cell colonies can be harvested within 4 weeks after initial cell isolation from VM tissue or lesional blood (Figure 1A,B). The day after injection, the xenograft lesion plug covers a surface area of approximately 80&#8210;100 mm2. In our hands, lesion plugs with TIE2/PIK3CA-mutant EC are visibly vascul...

Watch this Scientific Journal Video about A Patient-Derived Xenograft Model for Venous Malformation at JoVE.com

A Patient-Derived Xenograft Model for Venous Malformation

We present a detailed protocol to generate a murine xenograft model of venous malformation. This model is based on the subcutaneous injection of patient-derived endothelial cells containing hyper-activating TIE2 and/or PIK3CA gene mutations. Xenograft lesions closely recapitulate the histopathological features of VM patient tissue.

Venous malformation (VM) is a vascular anomaly that arises from impaired development of the venous network resulting in dilated and often dysfunctional ...

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Developmental Biology

5.2K Views.  Cincinnati Children's Hospital Medical Center. We present a detailed protocol to generate a murine xenograft model of venous malformation. This model is based on the subcutaneous injection of patient-derived endothelial cells containing hyper-activating TIE2 and/or PIK3CA gene mutations. Xenograft lesions closely recapitulate the histopathological features of VM patient tissue.

Video: A Patient-Derived Xenograft Model for Venous Malformation

Establishment of a Clinically Relevant Ex Vivo Mock Cataract Surgery Model for Investigating Epithelial Wound Repair in a Native Microenvironment

The major impediment to understanding how an epithelial tissue executes wound repair is the limited availability of models in which it is possible to follow and manipulate the wound response ex vivo in an environment that closely mimics that of epithelial tissue injury in vivo. This issue was addressed by creating a clinically relevant epithelial ex vivo injury-repair model based on cataract surgery. In this culture model, the response of the lens epithelium to wounding can be followed live in the cells&#8217; native microenvironment, and the molecular mediators of wound repair easily manipulated during the repair process. To prepare the cultures, lenses are removed from the eye and a small incision is made in the anterior of the lens from which the inner mass of lens fiber cells is removed. This procedure creates a circular wound on the posterior lens capsule, the thick basement membrane that surrounds the lens. This wound area where the fiber cells were attached is located just adjacent to a continuous monolayer of lens epithelial cells that remains linked to the lens capsule during the surgical procedure. The wounded epithelium, the cell type from which fiber cells are derived during development, responds to the injury of fiber cell removal by moving collectively across the wound area, led by a population of vimentin-rich repair cells whose mesenchymal progenitors are endogenous to the lens1. These properties are typical of a normal epithelial wound healing response. In this model, as in vivo, wound repair is dependent on signals supplied by the endogenous environment that is uniquely maintained in this ex vivo culture system, providing an ideal opportunity for discovery of the mechanisms that regulate repair of an epithelium following wounding.

Establishment of a Clinically Relevant Ex Vivo Mock Cataract Surgery Model for Investigating Epithelial Wound Repair in a Native Microenvironment

Described here is the establishment of a clinically relevant ex vivo mock cataract surgery model that can be used to investigate mechanisms of the injury response of epithelial tissues within their native microenvironment.

The major impediment to understanding how an epithelial tissue executes wound repair is the limited availability of models in which it is possible to ...

A Novel Culture Model for Human Pluripotent Stem Cell Propagation on Gelatin in Placenta-conditioned Media

The propagation of human pluripotent stem cells (hPSCs) in conditioned medium derived from human cells in feeder-free culture conditions has been of interest. Nevertheless, an ideal humanized ex vivo feeder-free propagation method for hPSCs has not been developed; currently, additional exogenous substrates including basic fibroblast growth factor (bFGF), a master hPSC-sustaining factor, is added to all of culture media and synthetic substrata such as Matrigel or laminin are used in all feeder-free cultures. Recently, our group developed a simple and efficient protocol for the propagation of hPSCs using only conditioned media derived from the human placenta on a gelatin-coated dish without additional exogenous supplementation or synthetic substrata specific to hPSCs. This protocol has not been reported previously and might enable researchers to propagate hPSCs efficiently in humanized culture conditions. Additionally, this model obviates hPSC contamination risks by animal products such as viruses or unknown proteins. Furthermore, this system facilitates easy mass production of hPSCs using the gelatin coating, which is simple to handle, dramatically decreases the overall costs of ex vivo hPSC maintenance.

This protocol provides a simple and efficient way to propagate human pluripotent stem cells (hPSCs) using only conditioned media derived from the human placenta in a gelatin-coated dish without additional exogenous supplementation or hPSC-specific synthetic substrata.

The propagation of human pluripotent stem cells (hPSCs) in conditioned medium derived from human cells in feeder-free culture conditions has been of ...

Culture of Murine Embryonic Metatarsals: A Physiological Model of Endochondral Ossification

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or longitudinal bone growth. As such, it is imperative that we further our understanding of the underpinning molecular mechanisms involved in such disorders so as to provide advances towards human and animal patient benefit. The mouse metatarsal organ explant culture is a highly physiological ex vivo model for studying endochondral ossification and bone growth as the growth rate of the bones in culture mimic that observed in vivo. Uniquely, the metatarsal organ culture allows the examination of chondrocytes in different phases of chondrogenesis and maintains cell-cell and cell-matrix interactions, therefore providing conditions closer to the in vivo situation than cells in monolayer or 3D culture. This protocol describes in detail the intricate dissection of embryonic metatarsals from the hind limb of E15 murine embryos and the subsequent analyses that can be performed in order to examine endochondral ossification and longitudinal bone growth.

We present a protocol to dissect and culture embryonic day 15 (E15) murine metatarsal bones. This highly physiological ex vivo model of endochondral ossification provides conditions closer to the in vivo situation than cells in monolayer or 3D culture and is a vital tool for investigating bone growth and development.

The fundamental process of endochondral ossification is under tight regulation in the healthy individual so as to prevent disturbed development and/or ...

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka and zebrafish larvae are widely used to analyze the behavior of bone cells during bone formation, degeneration, and repair. Their optical clarity allows the visualization of fluorescently labeled bone cells and fluorescent dyes bound to the mineralized skeletal matrix. Our lab has generated transgenic medaka fish that express the osteoclast-inducing factor Receptor Activator of Nuclear-factor &#954;B Ligand (RANKL) under the control of a heat&#160;shock-inducible promoter. Ectopic expression of RANKL results in the excess formation of activated osteoclasts, which can be visualized in reporter lines with nlGFP expression under the control of the cathepsin K (ctsk) promoter. RANKL induction and ectopic osteoclast formation leads to severe osteoporosis-like phenotypes. Compound transgenic medaka lines that express ctsk:nlGFP in osteoclasts, as well as mCherry under the control of the osterix (osx) promoter in premature osteoblasts, can be used to study the interaction of both cell types. This facilitates the in vivo observation of cellular behavior under conditions of bone degeneration and repair. Here, we describe the use of this system to test a drug commonly used in human osteoporosis therapy and describe a protocol for live imaging. The medaka model complements studies in cell culture and mice, and offers a novel system for the in vivo analysis of drug action in the skeletal system.

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Small laboratory fish have become popular models for bone research on the mechanisms underlying human bone disorders and for the screening of bone-modulating drugs. In this report, we describe a protocol to assess the effect of alendronate on bone cells in medaka larvae with osteoporotic lesions.

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka ...

Rapid Isolation of BMPR-IB+ Adipose-Derived Stromal Cells for Use in a Calvarial Defect Healing Model

Invasive cancers, major injuries, and infection can cause bone defects that are too large to be reconstructed with preexisting bone from the patient's own body. The ability to grow bone de novo using a patient's own cells would allow bony defects to be filled with adequate tissue without the morbidity of harvesting native bone. There is interest in the use of adipose-derived stromal cells (ASCs) as a source for tissue engineering because these are obtained from an abundant source: the patient's own adipose tissue. However, ASCs are a heterogeneous population and some subpopulations may be more effective in this application than others. Isolation of the most osteogenic population of ASCs could improve the efficiency and effectiveness of a bone engineering process. In this protocol, ASCs are obtained from subcutaneous fat tissue from a human donor. The subpopulation of ASCs expressing the marker BMPR-IB is isolated using FACS. These cells are then applied to an in vivo calvarial defect healing assay and are found to have improved osteogenic regenerative potential compared with unsorted cells.

Adipose-derived stromal cells may be useful for engineering new tissue from a patient's own cells. We present a protocol for the isolation of a subpopulation of human adipose-derived stromal cells (ASCs) with increased osteogenic potential, followed by application of the cells in an in vivo calvarial healing assay.

Invasive cancers, major injuries, and infection can cause bone defects that are too large to be reconstructed with preexisting bone from the patient's own ...

A Seminiferous Tubule Squash Technique for the Cytological Analysis of Spermatogenesis Using the Mouse Model

Meiotic progression in males is a process that requires the concerted action of a number of highly regulated cellular events. Errors occurring during meiosis can lead to infertility, pregnancy loss or genetic defects. Commencing at the onset of puberty and continuing throughout adulthood, continuous semi-synchronous waves of spermatocytes undergo spermatogenesis and ultimately form haploid sperm. The first wave of mouse spermatocytes undergoing meiotic initiation appear at day 10 post-partum (10 dpp) and are released into the lumen of seminiferous tubules as mature sperm at 35 dpp. Therefore, it is advantageous to utilize mice within this developmental time-window in order to obtain highly enriched populations of interest. Analysis of rare cell stages is more difficult in older mice due to the contribution of successive spermatogenic waves, which increase the diversity of the cellular populations within the tubules. The method described here is an easily implemented technique for the cytological evaluation of the cells found within the seminiferous tubules of mice, including spermatogonia, spermatocytes, and spermatids. The tubule squash technique maintains the integrity of isolated male germ cells and allows examination of cellular structures that are not easily visualized with other techniques. To demonstrate the possible applications of this tubule squash technique, spindle assembly was monitored in spermatocytes progressing through the prophase to metaphase I transition (G2/MI transition). In addition, centrosome duplication, meiotic sex chromosome inactivation (MSCI), and chromosome bouquet formation were assessed as examples of the cytological structures that can be observed using this tubule squash method. This technique can be used to pinpoint specific defects during spermatogenesis that are caused by mutation or exogenous perturbation, and thus, contributes to our molecular understanding of spermatogenesis.

The goal of this tubule squash technique is to rapidly assess cytological features of developing mouse spermatocytes while preserving cellular integrity. This method allows for the study of all stages of spermatogenesis, and can be easily implemented alongside other biochemical and molecular biological approaches for the study of mouse meiosis.

Meiotic progression in males is a process that requires the concerted action of a number of highly regulated cellular events. Errors occurring during ...

Partial Lobular Hepatectomy: A Surgical Model for Morphologic Liver Regeneration

Morphological organ regeneration following acute tissue loss is common among lower vertebrates, but is rarely observed in mammalian postnatal life. Adult liver regeneration after 70% partial hepatectomy results in hepatocyte hypertrophy with some replication in remaining lobes with restoration of metabolic activity, but with permanent loss of the injured lobe&#39;s morphology and architecture. Here, we detail a new surgical method in the neonate that leaves a physiologic environment conducive to regeneration. This model involves amputation of the left lobe apex and a subsequent conservative management regimen, and lacks the necessity for ligation of major liver vessels or chemical injury, leaving a physiologic environment where regeneration may occur. We extend this protocol to amputations on juvenile (P7-14) mice, during which the injured liver transitions from organ regeneration to compensatory growth by hypertrophy. The presented, brief 30 min protocol provides a framework to study the mechanisms of regeneration, its age-associated decline in mammals, and the characterization of putative hepatic stem or progenitors.

Here, we present a new method for partial resection of the left hepatic lobe in neonatal (day 0) mice. This new protocol is suitable for studying acute liver injury and injury response in the neonatal setting.

Morphological organ regeneration following acute tissue loss is common among lower vertebrates, but is rarely observed in mammalian postnatal life. Adult ...

A Mouse Distraction Osteogenesis Model

Distraction osteogenesis (DO) is a surgical procedure that involves skeletal tissue regeneration without cell transplantation. A DO model consists of the following three phases: the latency phase after osteotomy and placement of the external distractor; the distraction phase, wherein the separated bone ends are gradually and continuously distracted; and the consolidation phase. This custom-made distractor used for DO is comprised of two incomplete acrylic resin rings and an expansion screw. The process was initiated by making a mold with silicone impression material and then creating the custom-made distractor. Dental resin was poured into the formwork made of silicone impression material, and it was allowed to polymerize to create the incomplete resin rings required for the custom-made distractor. These rings were fixed with an expansion screw using transparent resin. The custom-made distractor created via this approach was attached to the tibia of mice. The tibia was fixed to the device using one pair of 25 G needles proximally, one pair of 27 G needles distally, and acrylic resin. After a latency period of 5 days, distraction was initiated at a rate of 0.2 mm/12 h. The lengthening was continued for 8 days, resulting in a total gap of 3.2 mm. The mice were sacrificed 4 weeks after distraction. Bone formation in the distraction gap was confirmed using both radiography and histology.

We present a mouse tibial distraction osteogenesis model developed using a custom-made distractor. The use of a mouse as an analysis target is advantageous for advancing research.

Distraction osteogenesis (DO) is a surgical procedure that involves skeletal tissue regeneration without cell transplantation. A DO model consists of the ...

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart disease. When using prosthetic materials however, these grafts are susceptible to bacterial infections and various host responses.
Identification of bacterial and host factors that play a vital role in endovascular adherence of microorganisms is of importance to better understand the pathophysiology of the onset of infections such as infective endocarditis (IE) and to develop preventive strategies. Therefore, the development of competent models to investigate bacterial adhesion under physiological shear conditions is necessary. Here, we describe the use of a newly designed in vitro perfusion chamber based on parallel plates that allows the study of bacterial adherence to different components of graft tissues such as exposed extracellular matrix, endothelial cells and inert areas. This method combined with colony-forming unit (CFU) counting is adequate to evaluate the propensity of graft materials towards bacterial adhesion under flow. Further on, the flow chamber system might be used to investigate the role of blood components in bacterial adhesion under shear conditions. We demonstrated that the source of tissue, their surface morphology and bacterial species specificity are not the major determining factors in bacterial adherence to graft tissues by using our in-house designed in vitro perfusion model.

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

We describe an in-house designed in vitro flow chamber model, which allows the investigation of bacterial adherence to graft tissues.

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart ...

Adult Mouse Digit Amputation and Regeneration: A Simple Model to Investigate Mammalian Blastema Formation and Intramembranous Ossification

Here, we present a protocol of adult mouse distal terminal phalanx (P3) amputation, a procedurally simple and reproducible mammalian model of epimorphic regeneration, which involves blastema formation and intramembranous ossification analyzed by fluorescence immunohistochemistry and sequential in-vivo microcomputed tomography (&#956;CT). Mammalian regeneration is restricted to amputations transecting the distal region of the terminal phalanx (P3); digits amputated at more proximal levels fail to regenerate and undergo fibrotic healing and scar formation. The regeneration response is mediated by the formation of a proliferative blastema, followed by bone regeneration via intramembranous ossification to restore the amputated skeletal length. P3 amputation is a preclinical model to investigate epimorphic regeneration in mammals, and is a powerful tool for the design of therapeutic strategies to replace fibrotic healing with a successful regenerative response. Our protocol uses fluorescence immunohistochemistry to 1) identify early-and-late blastema cell populations, 2) study revascularization in the context of regeneration, and 3) investigate intramembranous ossification without the need for complex bone stabilization devices. We also demonstrate the use of sequential in vivo &#956;CT to create high resolution images to examine morphological changes after amputation, as well as quantify volume and length changes in the same digit over the course of regeneration. We believe this protocol offers tremendous utility to investigate both epimorphic and tissue regenerative responses in mammals.

Here, we present a protocol of adult mouse terminal phalanx amputation to investigate mammalian blastema formation and intramembranous ossification, analyzed by fluorescent immunohistochemistry and sequential in-vivo microcomputed tomography.

Here, we present a protocol of adult mouse distal terminal phalanx (P3) amputation, a procedurally simple and reproducible mammalian model of epimorphic ...