MICRO-CT EVALUATION OF MSC/HUVEC/HSC-MEDIATED ANGIOGENESIS IN LARGE PCL-ßTCP CONSTRUCTS IMPLANTED IN NUDE MICE

Abstract

Stable vascular networks are prerequisite for scaffold-guided reconstruction of large voluminous bony defects. However, induction of angiogenesis remains a major challenge for bone-tissue engineering. The present in vivo study evaluates human umbilical cord derived vascular endothelial cells (HUVEC) or hematopoietic stem cells(HSCs)-mediated formation of microvascular networks in a biocompatible PCL-ßTCP hybrid scaffold in an immuno-compromised nude mouse. The PCL-ßTCP scaffold (30% PCL: 70% ßTCP; 70% porosity) with interconnected open pores was fabricated in 6x6x6mm cubes. They were seeded with human mesenchymal stem cells (MSCs) plus HUVECs or HSCs. Groups (N=12) consisted of scaffold samples seeded with MSCs alone, MSCs and HUVECs, MSCs and HSCs, and no cells. Cell suspension containing thrombin was evenly seeded into the micro porous constructs, sealed with fibrinogen, and implanted into immunodeficient mice for 8 weeks. At the end of the 8th week, mouse blood vessels were perfused with radiopaque microfil. The scaffolds were harvested, demineralized and analyzed for neovasculature by microcomputed tomography (micro- CT). The formation of microvasculature was significantly higher in the MSC-HUVEC and MSC-HSC constructs than those seeded with MSC alone or cell-free constructs. Volumetric analysis showed that MSC-HUVEC constructs contained 250% more microvasculature than cell-free construct and 180% more microvasculature than MSC or MSC-HSC constructs. Furthermore, neovascularization in the cell free construct was limited to the surface of the construct. The development of neovascularization from noninvasive sources constitutes an important step in the development of clinical strategies for tissue vascularization of large craniofacial defects.