Mimicking the native bone regenerative microenvironment for in situ repair of large physiological and pathological bone defects

Bone is a complex biological tissue with a complicated hierarchical nanocomposite structure.The native microen-vironment of the bone tissue may be significantly disrupted by large physiological and pathological bone defects.Bone defects are often treated via complex surgical procedures that involve the application of autografts or al-lografts.While these grafting procedures often suffer from insufficient natural bone stock and immunorejection.Moreover,these traditional treatment methods fail to simulate a regenerative microenvironment,which plays a significant role in regeneration of bone tissue and repair of large bone defects.To this end,various biomimetic scaffolds have been devised to mimic the native microenvironment of bone and thereby to simultaneously re-pair bone defects and promote bone regeneration.We propose here a novel concept,in vivo bone regenerative microenvironment(BRM),which enables repair of large bone defects and enhances new bone tissue formation with external regulation.In this review,we mainly focus on materials and methods for fabrication of biomimetic scaffolds,as well as their therapeutic efficacy in modulating the BRM of large physiological and pathological bone defects.