Neuropeptide Y, substance P, and human bone morphogenetic protein 2 stimulate human osteoblast osteogenic activity by enhancing gap junction intercellular communication

Abstract

Bone homeostasis seems to be controlled by delicate and subtle “cross talk” between the nervous system and “osteo-neuromediators” that control bone remodeling. The purpose of this study was to evaluate the effect of interactions between neuropeptides and human bone morphogenetic protein 2 (hBMP2) on human osteoblasts. We also investigated the effects of neuropeptides and hBMP2 on gap junction intercellular communication (GJIC). Osteoblasts were treated with neuropeptide Y (NPY), substance P (SP), or hBMP2 at three concentrations. At various intervals after treatment, cell viability was measured by the MTT assay. In addition, cellular alkaline phosphatase (ALP) activity and osteocalcin were determined by colorimetric assay and radioimmunoassay, respectively. The effects of NPY, SP and hBMP on GJIC were determined by laser scanning confocal microscopy. The viability of cells treated with neuropeptides and hBMP2 increased significantly in a time-dependent manner, but was inversely associated with the concentration of the treatments. ALP activity and osteocalcin were both reduced in osteoblasts exposed to the combination of neuropeptides and hBMP2. The GJIC of osteoblasts was significantly increased by the neuropeptides and hBMP2. These results suggest that osteoblast activity is increased by neuropeptides and hBMP2 through increased GJIC. Identification of the GJIC-mediated signal transduction capable of modulating the cellular activities of bone cells represents a novel approach to studying the biology of skeletal innervation.

Short Anabolic Peptides for Bone Growth

“…At concentrations higher than 10 −5 mM, SP stimulates OB differentiation and bone matrix mineralization, but lower concentrations of SP blocks osteogenic differentiation and induces proliferation of rat bone marrow MSCs and general protein synthesis . Recent studies showed that SP (10 −5 mM) increased ALP and osteocalcin activity in human OB proliferation and mineralization through increased GJIC between OBs . GJIC has important roles in conveying the anabolic effects of hormones and growth factors and regulating transcription of osteogenic markers…”

“…This effect was mediated by cyclic AMP and VPAC2 receptor. At 3 × 10 −5 mM, VIP enhanced human OB proliferation and mineralization through increased gap junction intercellular communication (GJIC) between OBs, an effect that was greater than that seen with substance P …”

“…208 This effect was mediated by cyclic AMP and VPAC2 receptor. At 3 × 10 −5 mM, VIP enhanced human OB proliferation and mineralization through increased gap junction intercellular communication (GJIC) between OBs, an effect that was greater than that seen with substance P. 209,210 Several results confirm the essential function of PACAP/VIP system in the differentiation or activation of OCs, providing a role in bone resorption. 211 Addition of VIP was shown to enhance the osteoclastogenic properties of mice calvarial OBs.…”

“…221,222 Recent studies showed that SP (10 −5 mM) increased ALP and osteocalcin activity in human OB proliferation and mineralization through increased GJIC between OBs. 209,210 GJIC has important roles in conveying the anabolic effects of hormones and growth factors and regulating transcription of osteogenic markers. 223 A recent study demonstrated SP (6.7 μg/kg) increased collagen deposition, bone volume, and density in trabecular bone anastomosis of rat femurs when administered intravenously in rats three times a week for 66 weeks.…”

Effects of early life stress on bone homeostasis in mice and humans

“…This response pattern is suggestive for a higher rate of bone turnover and lower bone healing capacities as a consequence of early life stress, suggesting a concurrent joint downregulation, reduced bone remodeling and long-term destabilization. The neurotrophin NGF is important for the expression of cholinergic and sensory neuronal factors and hence for the development and the repair of bone, as demonstrated by reduced bone length when absent[14][15][16][17][18][19][20][21][22][23][24][25][26].The neuropeptide NPY promotes osteoblast differentiation and balances the effects of stress-induced bone-loss through beta-adrenergic stimulation, both with consequences for bone remodeling during healing[10,53,[56][57][58][59][60][61][62][63]. The neuropeptide VIPR1, finally, promotes bone mineralization[64][65][66][67][68] while TACR1 regulates osteoblasts, osteoclasts and mesenchymal stem cell functionality associated with protection from osteoporosis [2, 62, 69-85].…”