In vitro and in vivo effects of rat kidney vascular endothelial cells on osteogenesis of rat bone marrow mesenchymal stem cells growing on polylactide-glycoli acid (PLGA) scaffolds

Hongchen Sun,Bai Yang,Ying Guo,Guangxiang Zang,Zhe Qu

doi:10.1186/1475-925x-6-41

Abstract

It is well established that vascularization is critical for osteogenesis. However, adequate vascularization also remains one of the major challenges in tissue engineering of bone. This problem is further accentuated in regeneration of large volume of tissue. Although a complex process, vascularization involves reciprocal regulation and functional interaction between endothelial and osteoblast-like cells during osteogenesis. This prompted us to investigate the possibility of producing bone tissue both in vitro and ectopically in vivo using vascular endothelial cells because we hypothesized that the direct contact or interaction between vascular endothelial cells and bone marrow mesenchymal stem cells are of benefit to osteogenesis in vitro and in vivo. For that purpose we co-cultured rat bone marrow mesenchymal stem cells (MSC) and kidney vascular endothelial cells (VEC) with polylactide-glycolic acid scaffolds. In vitro experiments using alkaline phosphatase and osteocalcin assays demonstrated the proliferation and differentiation of MSC into osteoblast-like cells, especially the direct contact between VEC and MSC. In addition, histochemical analysis with CD31 and von-Willebrand factor staining showed that VEC retained their endothelial characteristics. In vivo implantation of MSC and VEC co-cultures into rat's muscle resulted in pre-vascular network-like structure established by the VEC in the PLGA. These structures developed into vascularized tissue, and increased the amount and size of the new bone compared to the control group (p < 0.05). These results suggest that the vascular endothelial cells could efficiently stimulate the in vitro proliferation and differentiation of osteoblast-like cells and promote osteogenesis in vivo by the direct contact or interaction with the MSC. This technique for optimal regeneration of bone should be further investigated.

Highlights

Bone deficiency following trauma, resection of tumour, periodontal disease or congenital malformation can be associated with functional and aesthetic problems
Bone marrow mesenchymal stem cells were sterilely harvested from the femur and grown in 199 medium supplemented with 10-6 M desacortone, 50 μg/ml ascorbic acid (Invitrogen), 1% L-glutamine, 10% fetal bovine serum (Invitrogen), 100 U/ml penicillin G (Invitrogen), 100 μg/ml streptomycin (Invitrogene, Carlsbad, CA, USA)
These results indicate that mesenchymal stem cells (MSC) posses osteoblast-like characteristics

Summary

Introduction

Resection of tumour, periodontal disease or congenital malformation can be associated with functional and aesthetic problems. Since diffusion of oxygen in the active tissue is limited about 150 μm from capillary (mean of intercapillary distance (ICD) was 304 ± 30 μm.)[8], vascularization becomes crucial in larger volume of tissue-engineered construct. Growth factors, such as vascular endothelial growth factor (VEGF), collagen type II, myometrial prostaglandin E2, epithelial growth factor and basic fibroblast growth factor (bFGF), have been widely used to accelerate neovascularization in order to regenerate damaged tissues [9,10]. In vitro construction of vascular stroma could serve as a scaffold for soft or hard-tissue transplant

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Conclusion