A pilot study: Nano-hydroxyapatite-PEG/PLA containing low dose rhBMP2 stimulates proliferation and osteogenic differentiation of human bone marrow derived mesenchymal stem cells.

Background: Bone morphogenetic protein 2 (BMP2) can enhance posterolateral spinal fusion (PLSF). The minimum effective dose that may stimulate mesenchymal stem cells however remains unknown. Nano-hydroxyapatite (nHAp) polyethylene glycol (PEG)/polylactic acid (PLA) was combined with recombinant human BMP2 (rhBMP2). We in vitro evaluated proliferation, differentiation, and osteogenic genes of human bone marrow mesenchymal stem cells with 0.5, 1.0, and 3.0 μg/mL rhBMP2 doses in this study.

Methods: In vitro experimental study was designed to proliferation by a real-time quantitative cell analysis system and the osteogenic differentiation by alkaline phosphatase (ALP) activity and osteogenic marker (Runx2, OPN, and OCN) gene expressions of human derived bone marrow mesenchymal stem cells (hBMMSCs). nHAp was produced by wet chemical process and characterized by Fourier transform infrared spectrophotometer, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. PEG/PLA polymer was produced at a 51:49 molar ratio. 0.5, 1.0, and 3.0 μg/mL rhBMP2 and nHAp was combined with the polymers. hBMMSCs were characterized by multipotency assays and surface markers were assessed by flow cytometer. The hBMMSC-rhBMP2 containing nHAp-PEG/PLA composite interaction was evaluated by transmission electron microscopy. Proliferative effect was evaluated by real-time proliferation analysis, and osteogenic capacity was evaluated by ALP activity assay and qPCR.

Results: hBMMSC proliferation in the 0.5 μg/mL rhBMP2 + nHAp-PEG/PLA and the 1.0 μg/mL rhBMP2 + nHAp-PEG/PLA groups were higher compared to control. 1.0 μg/mL rhBMP2 + nHAp-PEG/PLA and 3.0 μg/mL rhBMP2 + nHAp-PEG/PLA containing composites induced ALP activity on days 3 and 10. 0.5 μg/mL rhBMP2 + nHAp-PEG/PLA application stimulated Runx2 and OPN gene expressions.

Conclusion: rhBMP2 + nHAp-PEG/PLA composites stimulate hBMMSC proliferation and differentiation. The nHAp-PEG/PLA composite with low dose of rhBMP2 may enhance bone formation in future clinical PLSF applications.