Endothelial progenitors enhanced the osteogenic capacities of mesenchymal stem cells in vitro and in a rat alveolar bone defect model.

OBJECTIVE: Transplantation of mesenchymal stem cells (MSCs) may promote bone healing. Endothelial progenitor cells (EPCs) may enhance the osteogenic properties of MSCs by improving their microenvironment. We aimed to investigate whether EPCs can enhance the osteogenic properties of MSCs in vitro, and whether transplantation of EPC-MSC cell sheets could promote bone regeneration in a rat model of alveolar bone defect. DESIGN: MSCs and EPCs were obtained from 2-week-old Sprague-Dawley rats. Cell sheets were prepared using MSCs and MSCs co-cultured with EPCs. Morphological characteristics of cell sheets were observed by H&E staining. Osteogenic differentiation capacities of the cell sheets were assessed by alkaline phosphatase (ALP) staining, Alizarin Red S staining and qRT-PCR. Cell sheets were transplanted into alveolar bone defects in 8-week-old rats. Six weeks later, bone formation was assessed by micro-CT. RESULTS: EPC-MSC sheets exhibited faster osteogenesis than MSC sheets. Six weeks after implantation, alveolar bone defects transplanted with EPC-MSC sheets exhibited a better bone reconstruction. MSC sheets generated new bone that partially covered the defect areas, while EPC-MSC sheets exhibited more robust osteogenic activity, with continuous new bone that almost covered the entire defect area. CONCLUSIONS: Transplantation of cell sheets containing EPCs and MSCs promoted bone regeneration.

Carbon nanotubes as VEGF carriers to improve the early vascularization of porcine small intestinal submucosa in abdominal wall defect repair.

Insufficient early vascularization in biological meshes, resulting in limited host tissue incorporation, is thought to be the primary cause for the failure of abdominal wall defect repair after implantation. The sustained release of exogenous angiogenic factors from a biocompatible nanomaterial might be a way to overcome this limitation. In the study reported here, multiwalled carbon nanotubes (MWNT) were functionalized by plasma polymerization to deliver vascular endothelial growth factor165 (VEGF165). The novel VEGF165-controlled released system was incorporated into porcine small intestinal submucosa (PSIS) to construct a composite scaffold. Scaffolds incorporating varying amounts of VEGF165-loaded functionalized MWNT were characterized in vitro. At 5 weight percent MWNT, the scaffolds exhibited optimal properties and were implanted in rats to repair abdominal wall defects. PSIS scaffolds incorporating VEGF165-loaded MWNT (VEGF-MWNT-PSIS) contributed to early vascularization from 2-12 weeks postimplantation and obtained more effective collagen deposition and exhibited improved tensile strength at 24 weeks postimplantation compared to PSIS or PSIS scaffolds, incorporating MWNT without VEGF165 loading (MWNT-PSIS).