Parallel binding of autologous BMP-2 and VEGF envisioning a vascularized bone tissue engineering approach

Objectives

Reconstruction of large bone defects still remaining a major clinical orthopedic challenge, since the repair of bone defect comprises not only the process of new bone formation, but also the formation of new blood vessels - angiogenesis¹. Bone morphogenetic proteins (BMPs) and vascular endothelial growth factor (VEGF) are involved in cell differentiation and bone vascularization to develop viable osseous tissue^2,3. Accordingly, herein it is hypothesized that the synergistic effect of autologous BMP-2 and VEGF, parallel bound over a single nanofibrous substrate, can lead to a successful osteogenic and angiogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs).

Methods

Specific antibodies for BMP-2 and VEGF were immobilized over an electrospun nanofibrous mesh, in a parallel pattern design. The BMP-2 and VEGF derived from platelet lysate (PL) were captured to the biofunctional nanofibrous substrate. The unbound protein solution was quantified by ELISA. The osteogenic and angiogenic potential of this engineered biofunctionalized system was assessed by culturing hBM-MSCs during 21 days, without exogenous induction.

Results

The antibodies against BMP-2 and VEGF were immobilized parallel in at the maximum concentration of 4 µg/mL each, over the same nanofibrous substrate. Biochemical performance of hBM-MSCs cultured on the engineered biofunctional system confirms the biological activity of bound BMP-2 and VEGF. The quantification of angiogenic and osteogenic transcripts revealed that hBM-MSCs respond according to the growth factor bound to the engineered biofunctional system. The immunolocalization of osteocalcin and CD31 confirmed the osteogenic and angiogenic phenotype of the differentiated hBM-MSCs.

Discussion

The biofunctional nanofibrous substrate is capable of efficiently capture BMP-2 and VEGF from PL. The proposed system containing BMP-2 is able to promote the osteogenesis of hBM-MSCs, as well as the bound VEGF is able to stimulate angiogenesis. The synergistic effect of bound growth factors enables the development of a vascularized bone tissue engineering approach.