Biostimulatory Micro-Fragmented Nanofiber-Hydrogel Composite Improves Mesenchymal Stem Cell Delivery and Soft Tissue Remodeling.

Functional microgels are preferred stem cell carriers due to the ease of delivery through minimally invasive injection and seamless integration with the surrounding host tissue. A biostimulatory nanofiber-hydrogel composite (NHC) has been previously developed through covalently crosslinking a hyaluronic acid hydrogel network with surface-functionalized poly (ε-caprolactone) nanofiber fragments. The NHC mimics the microarchitecture of native soft tissue matrix, showing enhanced cell infiltration, immunomodulation, and proangiogenic properties. Here, injectability of the pre-formed NHC is improved by mechanical fragmentation, making it into micro-fragmented NHC (mfNHC) in a granular gel form as a stem cell carrier to deliver mesenchymal stem cells (MSCs) for soft tissue remodeling. The mfNHC shows a similar storage modulus but a significantly reduced injection force, as compared with the corresponding bulk NHC. When injected subcutaneously in a rat model, mfNHC-MSC constructs initiate an elevated level of host macrophage infiltration, more pro-regenerative polarization, and subsequently, improved angiogenesis and adipogenesis response when compared to mfNHC alone. A similar trend of host cell infiltration and pro-angiogenic response is detected in a swine model with a larger volume injection. These results suggest a strong potential for use of the mfNHC as an injectable carrier for cell delivery and soft tissue remodeling.