Enhanced fibrocartilage regeneration at the tendon-bone interface injury through extracellular matrix hydrogel laden with bFGF-overexpressing human urine-derived stem cells

The tendon-bone interface (TBI) is crucial in the transfer of mechanical loads; however, it is susceptible to injuries that frequently result in healing via fibrous scar tissue formation. Consequently, regeneration of the fibrocartilaginous zone has become a pivotal area subject. At present, the use of stem cells represents a notably promising approach for TBI treatment. Especially, human urine-derived stem cells (hUSCs) present a practical option for cell-based therapies. Nevertheless, the chondrogenic differentiation potential of hUSCs is limited. To address this, basic fibroblast growth factor (bFGF) was transinfected into hUSCs to bolster their differentiation capacity and facilitate the formation of fibrocartilage in the target area. Additionally, the local immune microenvironment dramatically influences TBI healing, with macrophages playing a vital role. Effective healing relies on the phenotype transition of macrophages, with an imbalance often leading to insufficient regeneration and scar tissue formation. Innovations in biomaterials have provided new avenues for TBI repair, such as the porcine small intestinal submucosa (SIS) hydrogel developed in our prior research. In addition to serving as a carrier for stem cell delivery, the hydrogel's bioactive components support tissue repair and immune regulation. In the present study, SIS hydrogel loaded with hUSCs that overexpress bFGF was used for the treatment of TBI injury, which is expected to correct inflammatory response imbalances, and promote macrophage polarization towards healing phenotypes, creating a favorable immune microenvironment. The combined effects of bFGF and the optimized immune setting are anticipated to enhance hUSCs' chondrogenic potential, aiding in the functional restoration of TBI injuries.