Perfusability and immunogenicity of implantable pre-vascularized tissues recapitulating features of native capillary network

Vascularization is a key pre-requisite to engineered anatomical scale three dimensional(3-D)constructs to ensure their nutrient and oxygen supply upon implantation.Presently,engineered pre-vascularized 3-D tissues are limited to only micro-scale hydrogels,which meet neither the anatomical scale needs nor the complexity of natural extracellular matrix(ECM)environments.Anatomical scale perfusable constructs are critically needed for translational applications.To overcome this challenge,we previously developed pre-vascularized ECM sheets with long and oriented dense microvascular networks.The present study further evaluated the patency,perfusability and innate immune response toward these pre-vascularized constructs.Macrophage-co-cultured prevascularized constructs were evaluated in vitro to confirm micro-vessel patency and perturbations in macrophage metabolism.Subcutaneously implanted pre-vascularized constructs remained viable and formed a functional anastomosis with host vasculature within 3 days of implantation.This completely biological pre-vascularized construct holds great potential as a building block to engineer perfusable anatomical scale tissues.

Novel pre-vascularized tissue-engineered dermis based on stem cell sheet technique used for dermis-defect healing

Insufficient donor dermis and the shortage of three-dimensional vascular networks are the main limitations in the tissue-engineered dermis(TED).To solve these problems,we initially constructed pre-vascularized bone marrow mesenchymal stem cell sheet(PBMCS)and pre-vascularized fibroblasts cell sheet(PFCS)by cell sheet technology,and then superimposed or folded them together to construct a pre-vascularized TED(PTED),aiming to mimic the real dermis structure.The constructed PTED was implanted in nude mice dorsal dermis-defect wound and the wound-healing effect was quantified at Days 1,7 and 14 via the methods of histochemistry and immunohistochemistry.The results showed that PTED could rapidly promote the wound closure,especially at Day 14,and the wound-healing rate of three-layer PTED could reach 97.2%(P<0.01),which was faster than the blank control group(89.1%),PBMCS(92.4%),PFCS(93.8%)and six-layer PTED(92.3%).In addition,the vessel density in the PTED group was higher than the other groups on the 14th day.Taken together,it is proved that the PTED,especially three-layer PTED,is more conducive to the fullthickness dermis-defect repair and the construction of the three-dimensional vascular networks,indicating its potential application in dermis-defect repair.

Chemically induced hypoxia by dimethyloxalylglycine(DMOG)-loaded nanoporous silica nanoparticles supports endothelial tube formation by sustained VEGF release from adipose tissue-derived stem cells

Inadequate vascularization leading to insufficient oxygen and nutrient supply in deeper layers of bioartificial tissues remains a limitation in current tissue engineering approaches to which prevascularization offers a promising solution.Hypoxia triggering pre-vascularization by enhanced vascular endothelial growth factor(VEGF)expression can be induced chemically by dimethyloxalylglycine(DMOG).Nanoporous silica nanoparticles(NPSNPs,or mesoporous silica nanoparticles,MSNs)enable sustained delivery of molecules and potentially release DMOG allowing a durable capillarization of a construct.Here we evaluated the effects of soluble DMOG and DMOG-loaded NPSNPs on VEGF secretion of adipose tissue-derived stem cells(ASC)and on tube formation by human umbilical vein endothelial cells(HUVEC)-ASC co-cultures.Repeated doses of 100 mM and 500 mM soluble DMOG on ASC resulted in 3-to 7-fold increased VEGF levels on day 9(P<0.0001).Same doses of DMOG-NPSNPs enhanced VEGF secretion 7.7-fold(P<0.0001)which could be maintained until day 12 with 500 mM DMOG-NPSNPs.In fibrin-based tube formation assays,100 mM DMOG-NPSNPs had inhibitory effects whereas 50 mM significantly increased tube length,area and number of junctions transiently for 4 days.Thus,DMOG-NPSNPs supported endothelial tube formation by upregulated VEGF secretion from ASC and thus display a promising tool for prevascularization of tissue-engineered constructs.Further studies will evaluate their effect in hydrogels under perfusion.