GelMA/HA-NB hydrogel encapsulating adipose-derived chondrogenic exosomes enhances enthesis regeneration in chronic rotator cuff tears

Chronic rotator cuff tears (RCTs) often lead to poor surgical outcomes, requiring innovative therapies. This study explores the potential of exosomes from chondrogenic stem/progenitor cells (CSPCs), encapsulated in a GelMA/HA-NB hydrogel, to improve rotator cuff healing. Adipose-derived stem cells (ASCs) were isolated and sorted to obtain CSPCs, from which exosomes (sub-Exos) were extracted and characterized. Unsorted ASCs exosomes (un-Exos) were also isolated for comparison. The hydrogel-exosome system was evaluated for biocompatibility, chondrogenic differentiation, and sustained release in vitro and in a chronic RCT rat model. 112 rats were divided into four groups: control, hydrogel alone, un-Exos with hydrogel, and sub-Exos with hydrogel. Healing was assessed at 4 and 8 weeks using micro-CT, histology, and biomechanical testing. In vitro, sub-Exos with hydrogel demonstrated excellent biocompatibility and enhanced chondrogenic potential. In vivo, sub-Exos were retained at the injury site for up to 14 days, significantly improving histological scores, bone mineral density, bone volume/total volume, and trabecular thickness. Biomechanical tests revealed superior failure load and stiffness in the sub-Exos group. These findings demonstrate that localized delivery of GelMA/HA-NB hydrogel-encapsulated sub-Exos significantly enhances enthesis healing, offering a promising cell-free therapeutic strategy for chronic RCTs.