Increased BMP-Smad signaling does not affect net bone mass in long bones

Frontiers in Physiology

Physiology

Tejaswi Koneru¹  Yishan Lyu¹  Ai Haraguchi¹  Maiko Omi¹  Yuji Mishina¹  Nobuhiro Kamiya² 

[1]Department of Biologic and Materials Sciences and Prosthodontics, University of Michigan School of Dentistry, Ann Arbor, MI, United States

[2]Department of Budo and Sport Studies, Faculty of Budo and Sport Studies, Tenri University, Nara, Japan

关键词: bone morphogenetic protein;    BMPR1A;    osteoblast lineage cells;    bone formation;    bone resorption;   

DOI  :  10.3389/fphys.2023.1145763

 received in 2023-01-16, accepted in 2023-03-21,  发布年份 2023

来源: Frontiers

【 摘 要 】

Bone morphogenetic proteins (BMPs) have been used for orthopedic and dental application due to their osteoinductive properties; however, substantial numbers of adverse reactions such as heterotopic bone formation, increased bone resorption and greater cancer risk have been reported. Since bone morphogenetic proteins signaling exerts pleiotropic effects on various tissues, it is crucial to understand tissue-specific and context-dependent functions of bone morphogenetic proteins. We previously reported that loss-of-function of bone morphogenetic proteins receptor type IA (BMPR1A) in osteoblasts leads to more bone mass in mice partly due to inhibition of bone resorption, indicating that bone morphogenetic protein signaling in osteoblasts promotes osteoclast function. On the other hand, hemizygous constitutively active (ca) mutations for BMPR1A (caBmpr1awt/+) in osteoblasts result in higher bone morphogenetic protein signaling activity and no overt skeletal changes in adult mice. Here, we further bred mice for heterozygous null for Bmpr1a (Bmpr1a+/−) and homozygous mutations of caBmpr1a (caBmpr1a+/+) crossed with Osterix-Cre transgenic mice to understand how differences in the levels of bone morphogenetic protein signaling activity specifically in osteoblasts contribute to bone phenotype. We found that Bmpr1a+/−, caBmpr1awt/+ and caBmpr1a+/+ mice at 3 months of age showed no overt bone phenotypes in tibiae compared to controls by micro-CT and histological analysis although BMP-Smad signaling is increased in both caBmpr1awt/+ and caBmpr1a+/+ tibiae and decreased in the Bmpr1a+/− mice compared to controls. Gene expression analysis demonstrated that slightly higher levels of bone formation markers and resorption markers along with levels of bone morphogenetic protein-Smad signaling, however, there was no significant changes in TRAP positive cells in tibiae. These findings suggest that changes in bone morphogenetic protein signaling activity within differentiating osteoblasts does not affect net bone mass in the adult stage, providing insights into the concerns in the clinical setting such as high-dose and unexpected side effects of bone morphogenetic protein application.

【 授权许可】

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Copyright © 2023 Omi, Koneru, Lyu, Haraguchi, Kamiya and Mishina.