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.

A novel nano-hydroxyapatite/synthetic polymer/bone morphogenetic protein-2 composite for efficient bone regeneration.

BACKGROUND: Efficient bone regeneration using recombinant human bone morphogenetic protein-2 (BMP-2) is needed to reduce side effects caused by high-dose BMP-2 use. The composite material of polylactic acid-polyethene glycol (PLA-PEG) for sustained release and an osteogenic nano-hydroxyapatite (nHAp) can contribute to efficient bone regeneration by BMP-2. STUDY DESIGN: An experimental in vitro and in vivo study. PURPOSE: The objective of this study is to investigate the effectiveness of a novel composite material of PLA-PEG and nHAp as a carrier for BMP-2. METHODS: The release kinetics of BMP-2 from the composites was investigated by ELISA. Thirty-six male Sprague-Dawley rats underwent posterolateral spinal fusion on L4-L5 with three different doses of BMP-2 (0 µg [control], 3 µg [low dose], and 10 µg [high dose]). Weekly µCT results and histology and a manual palpation test at 8 weeks postoperatively were used for assessment of the spinal fusion. RESULTS: ELISA demonstrated the sustained release of BMP-2 until day 21. µCT and manual palpation test demonstrated a solid fusion in 91.6% (11/12) of specimens in both the low- and high-dose groups. N mice in the control group attained bony fusion (0%, 0/9). nHAp was resorbed between 2 and 4 weeks postoperatively, and regenerated fusion mass at 8 weeks postoperatively consisted of only newly formed bone. CONCLUSIONS: The nHAp/PLA-PEG composite enabled efficient bone regeneration with low-dose BMP-2. The sustained release of BMP-2 by PLA-PEG and the osteogenic and biodegradable scaffold of nHAp might contribute to efficient bone regeneration. CLINICAL SIGNIFICANCE: This novel composite material has potential in clinical applications (spinal fusion, large bone defect and non-union) by enabling efficient bone formation by BMP-2.

Effect of Systemic Oxytocin Administration on New Bone Formation and Distraction Rate in Rabbit Mandible.

PURPOSE: The main disadvantage of distraction osteogenesis is the prolonged treatment protocol. Recently, oxytocin (OT) has been found to have anabolic effects on bone metabolism. In this experimental study, the effects of OT on the mandibular distraction gap in rabbits at 2 different distraction rates were evaluated. MATERIALS AND METHODS: This experimental study was conducted on 28 male New Zealand white rabbits. The animals were divided into 3 experimental groups and 1 control group. Group A (control group, n = 7) consisted of animals with distraction at a rate of 1 mm/day, and group B (n = 7) consisted of animals with a distraction rate of 2 mm/day; groups A and B received postoperative saline solution injection. Group C (n = 7) consisted of animals with distraction at a rate of 1 mm/day, and group D (n = 7) consisted of animals with a distraction rate of 2 mm/day; postoperative OT injection was performed in groups C and D. RESULTS: Both histomorphologic and micro-computed tomography evaluations showed increased bone healing in the OT-treated groups. CONCLUSIONS: On the basis of the evaluation of both the histomorphometric and micro-computed tomographic data, systemic OT administration was found to increase new bone formation and bone healing with distraction osteogenesis.