Effect of recombinant human bone morphogenetic protein-2 on bisphosphonate-treated osteoblasts

Sub-clinical dose of bone morphogenetic protein-2 does not precipitate rampant, sustained inflammatory response in bone wound healing

Large bone injuries, defects, and chronic wounds present a major problem for medicine. Several therapeutic strategies are used clinically to precipitate bone including a combination therapy delivering osteoinductive bone morphogenetic protein 2 (rhBMP-2) via an osteoconductive scaffold (absorbable collagen sponge [ACS], i.e., INFUSE). Adverse side effects reportedly associated with rhBMP2 administration include rampant inflammation and clinical failures. Although acute inflammation is necessary for proper healing in bone, inflammatory cascade dysregulation can result in sustained tissue damage and poor healing. We hypothesized that a subclinical dose of rhBMP2 modeled in the murine calvarial defect would not precipitate alterations to inflammatory markers during acute phases of bone wound healing. We utilized the 5 mm critical size calvarial defect in C57BL6 wild-type mice which were subsequently treated with ACS and a subclinical dose of rhBMP2 shown to be optimal for healing. Three and 7-day postoperative time points were used to assess the role that rhBMP-2 plays in modulating inflammation vs. ACS alone by cytokine array and histological interrogation. Data revealed that rhBMP-2 delivery resulted in substantial modulation of several markers associated with inflammation, most of which decreased to levels similar to control by the 7-day time point. Additionally, while rhBMP-2 administration increased macrophage response, this peptide had a little noticeable effect on traditional markers of macrophage polarization (M1-iNOS, M2-Arg1). These results suggest that rhBMP-2 delivered at a lower dose does not precipitate rampant inflammation. Thus, an assessment of dosing for rhBMP-2 therapies may lead to better healing outcomes and less surgical failure.

Combined effect of recombinant human bone morphogenetic protein-2 and low level laser irradiation on bisphosphonate-treated osteoblasts

Objectives

The purpose of this study was to evaluate the synergic effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) and low-level laser therapy (LLLT) on bisphosphonate-treated osteoblasts.

Materials and Methods

Human fetal osteoblast cells (hFOB 1.19) were cultured with 100 µM alendronate. Low-level Ga-Al-As laser alone or with 100 ng/mL rhBMP-2 was then applied. Cell viability was measured with MTT assay. The expression levels of receptor activator of nuclear factor kappa-B ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and osteoprotegerin (OPG) were analyzed for osteoblastic activity inducing osteoclastic activity. Collagen type and transforming growth factor beta-1 were also evaluated for bone matrix formation.

Results

The results showed that rhBMP-2 and LLLT had a synergic effect on alendronate-treated osteoblasts for enhancing osteoblastic activity and bone matrix formation. Between rhBMP-2 and LLLT, rhBMP-2 exhibited a greater effect, but did not show a significant difference.

Conclusion

rhBMP-2 and LLLT have synergic effects on bisphosphonate-treated osteoblasts through enhancement of osteoblastic activity and bone formation activity.