Hypoxia-mimicking scaffolds with controlled release of DMOG and PTHrP to promote cartilage regeneration via the HIF-1α/YAP signaling pathway

Efficiently driving chondrogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) while avoiding undesired hypertrophy remains a challenge in the field of cartilage tissue engineering. Here, we report the sequential combined application of dimethyloxalylglycine (DMOG) and parathyroid hormone-related protein (PTHrP) to facilitate chondrogenesis and prevent hypertrophy. To support their delivery, poly(lactic-co-glycolic acid) (PLGA) microspheres were fabricated using a double emulsion method. Subsequently, these microspheres were incorporated onto a poly(l-lactic acid) (PLLA) scaffold with a highly porous structure, high inter -connectivity and collagen-like nanofiber architecture to construct a microsphere-based scaffold delivery system. These functional constructs demonstrated that the spatiotemporally controlled release of DMOG and PTHrP effectively mimicked the hypoxic microenvironment to promote chondrogenic differentiation with phenotypic stability in a 3D culture system, which had a certain correlation with the interaction between hypoxia-inducible Factor 1 alpha (HIF-1 alpha) and yes-associated protein (YAP). Subcutaneous implantation in nude mice revealed that the constructs were able to maintain cartilage formation in vivo at 4 and 8 weeks. Overall, this study indicated that DMOG and PTHrP controlled-release PLGA microspheres incorporated with PLLA nanofibrous scaffolds provided an advantageous 3D hypoxic microenvironment for efficacious and clinically relevant cartilage regeneration and is a promising treatment for cartilage injury.

Automated summary

In this study, the sequential combined application of DMOG and PTHrP was used to efficiently drive chondrogenic differentiation of BMSCs and prevent hypertrophy. PLGA microspheres were fabricated to support the delivery of these compounds, and then incorporated onto a PLLA scaffold to create a microsphere-based scaffold delivery system. The controlled release of DMOG and PTHrP in a 3D culture system effectively mimicked the hypoxic microenvironment and promoted chondrogenic differentiation, which was confirmed by the interaction between HIF-1 alpha and YAP. The constructs were able to maintain cartilage formation in vivo and show promise for cartilage regeneration.