Interaction Between Bmpr1a-mediated Signaling and Mechanical Signaling in Osteoblasts and Osteocytes

Objectives: Bone remodeling is affected by several factors, particularly mechanical loading and growth factor signaling. Osteocytes are believed to be the mechanosensor cells of the bone, transmit the mechanical response to osteoblasts and osteoclasts. Mechanical loading and suppression of BMP signaling was found to synergistically increase trabecular bone volume and improve trabecular modulus in the conditional knockout (cKO) mouse in which bone morphogenetic protein (Bmp) receptor type 1a (Bmpr1a) is specifically ablated in osteoblasts.In this study we investigated how bone cells response to mechanical stimulation and enhance bone mass.
Methods: In this study we investigated how bone cells response to mechanical stimulation and enhance bone mass with BMPR1A deficiency using the osteoblast-specific Bmpr1a conditional knockout (cKO) mouse model. Male mice with disruption of Bmpr1a induced at 3 weeks of age, exercised 30 min per days on a motor-driven treadmill from 9 to 12 weeks of age.
Results: The number of BrdU positive osteoblasts and osteocytes was increased in cKO mice. Moreover, Sost and RANKL expression was decreased in exercised cKO mice. Trabecular bone volume in cKO mice was further increased by exercise while bone volume in the control mice was not affected by exercise.
Conclusions: Taken together, reduction in BMPR1A signaling may sensitize osteoblasts and osteocytes for mechanical loading to increase bone mass and enhance osteoblasts and osteocytes ability to proliferate.