The role of sensory and sympathetic nerves in craniofacial bone regeneration

Sensory Nerve Regulation via H3K27 Demethylation Revealed in Akermanite Composite Microspheres Repairing Maxillofacial Bone Defect

Maxillofacial bone defects exhibit intricate anatomy and irregular morphology, presenting challenges for effective treatment. This study aimed to address these challenges by developing an injectable bioactive composite microsphere, termed D-P-Ak (polydopamine-PLGA-akermanite), designed to fit within the defect site while minimizing injury. The D-P-Ak microspheres biodegraded gradually, releasing calcium, magnesium, and silicon ions, which, notably, not only directly stimulated the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) but also activated sensory nerve cells to secrete calcitonin gene-related peptide (CGRP), a key factor in bone repair. Moreover, the released CGRP enhanced the osteogenic differentiation of BMSCs through epigenetic methylation modification. Specifically, inhibition of EZH2 and enhancement of KDM6A reduced the trimethylation level of histone 3 at lysine 27 (H3K27), thereby activating the transcription of osteogenic genes such as Runx2 and Osx. The efficacy of the bioactive microspheres in bone repair is validated in a rat mandibular defect model, demonstrating that peripheral nerve response facilitates bone regeneration through epigenetic modification. These findings illuminated a novel strategy for constructing neuroactive osteo-inductive biomaterials with potential for further clinical applications.

Neuro-bone tissue engineering: emerging mechanisms, potential strategies, and current challenges

The skeleton is a highly innervated organ in which nerve fibers interact with various skeletal cells. Peripheral nerve endings release neurogenic factors and sense skeletal signals, which mediate bone metabolism and skeletal pain. In recent years, bone tissue engineering has increasingly focused on the effects of the nervous system on bone regeneration. Simultaneous regeneration of bone and nerves through the use of materials or by the enhancement of endogenous neurogenic repair signals has been proven to promote functional bone regeneration. Additionally, emerging information on the mechanisms of skeletal interoception and the central nervous system regulation of bone homeostasis provide an opportunity for advancing biomaterials. However, comprehensive reviews of this topic are lacking. Therefore, this review provides an overview of the relationship between nerves and bone regeneration, focusing on tissue engineering applications. We discuss novel regulatory mechanisms and explore innovative approaches based on nerve-bone interactions for bone regeneration. Finally, the challenges and future prospects of this field are briefly discussed.

Messages from the Mineral: How Bone Cells Communicate with Other Tissues

Bone is a highly dynamic tissue, and the constant actions of bone-forming and bone-resorbing cells are responsible for attaining peak bone mass, maintaining bone mass in the adults, and the subsequent bone loss with aging and menopause, as well as skeletal complications of diseases and drug side-effects. It is now accepted that the generation and activity of bone-forming osteoblasts and bone-resorbing osteoclasts is modulated by osteocytes, osteoblast-derived cells embedded in the bone matrix. The interaction among bone cells occurs through direct contact and via secreted molecules. In addition to the regulation of bone cell function, molecules released by these cells are also able to reach the circulation and have effects in other tissues and organs in healthy individuals. Moreover, bone cell products have also been associated with the establishment or progression of diseases, including cancer and muscle weakness. In this review, we will discuss the role of bone as an endocrine organ, and the effect of selected, osteoblast-, osteocyte-, and osteoclast-secreted molecules on other tissues.