In spite of the considerable achievements in the field of regenerative medicine in the past several decades, osteochondral defect regeneration remains a challenging issue among diseases in the musculoskeletal system because of the spatial complexity of osteochondral units in composition, structure and functions. In order to repair the hierarchical tissue involving different layers of articular cartilage, cartilage-bone interface and subchondral bone, traditional clinical treatments including palliative and reparative methods have showed certain improvement in pain relief and defect filling. It is the development of tissue engineering that has provided more promising results in regenerating neo-tissues with comparable compositional, structural and functional characteristics to the native osteochondral tissues. Here in this review, some basic knowledge of the osteochondral units including the anatomical structure and composition, the defect classification and clinical treatments will be first introduced. Then we will highlight the recent progress in osteochondral tissue engineering from perspectives of scaffold design, cell encapsulation and signaling factor incorporation including bioreactor application. Clinical products for osteochondral defect repair will be analyzed and summarized later. Moreover, we will discuss the current obstacles and future directions to regenerate the damaged osteochondral tissues.

Clinical work and research on diabetic wound repair remain challenging globally. Although various conventional wound dressings have been continuously developed, the efficacy is unsatisfactory. The effect of drug delivery is limited by the depth of penetration. The sustained release of biomolecules from biological wound dressings is a promising treatment approach to wound healing. An assortment of cell-derived exosomes (exos) have been proved to be instrumental in tissue regeneration, and researchers are dedicated to developing biomolecules carriers with unique properties. Herein, we reported a methacrylate gelatin (GelMA) microneedles (MNs) patch to achieve transdermal and controlled release of exos and tazarotene. Our MNs patch comprising GelMA/PEGDA hydrogel has distinctive biological features that maintain the biological activity of exos and drugs in vitro. Additionally, its unique physical structure prevents it from being tightly attached to the skin of the wound, it promotes cell migration, angiogenesis by slowly releasing exos and tazarotene in the deep layer of the skin. The full-thickness cutaneous wound on a diabetic mouse model was carried out to demonstrate the therapeutic effects of GelMA/PEGDA@T + exos MNs patch. As a result, our GelMA/PEGDA@T + exos MNs patch presents a potentially valuable method for repairing diabetic wound in clinical applications. Graphic Abstract