Injectable Sema3a plasmid–delivery hydrogel attenuates hypoxia–cold stress–associated osteochondral degeneration

Introduction Osteoarthritis (OA) is sustained by reciprocal interactions among inflammatory immune cells, senescence-prone stromal cells, and the osteochondral unit. Environmental cold and hypobaric hypoxia can disrupt joint homeostasis, yet locally acting strategies capable of limiting the resulting immune–stromal and osteochondral changes remain limited. Methods An injectable dynamic hydrogel, termed ODCP, was engineered through reversible catechol–boronate ester crosslinking between dopamine-modified oxidized hyaluronic acid (OHA–DA) and phenylboronic acid-modified chondroitin sulfate (ChS–PBA). A pAAV-backbone plasmid encoding Sema3a was incorporated into ODCP to create a local gene-activated matrix (Sema3a@ODCP). Hydrogel properties were characterized in terms of gelation, injectability, and dynamic mechanical recovery. In vitro studies evaluated matrix preservation in IL-1β-stimulated primary rat articular chondrocytes, macrophage responses under hypoxic–cold stress (HCS), mitochondrial function, and stress-associated responses in bone marrow mesenchymal stromal cells (BMSCs) using a conditioned-medium model. In vivo, the effects of intra-articular Sema3a@ODCP administration were assessed in rats exposed to chronic HCS. Results ODCP exhibited rapid gelation, injectability, and dynamic mechanical recovery. In vitro, Sema3a@ODCP supported matrix preservation in IL-1β-stimulated primary rat articular chondrocytes, shifted HCS-exposed RAW 264.7 macrophages toward a CD206-enriched profile, improved mitochondrial membrane potential and ATP availability, and attenuated stress-associated responses in recipient BMSCs in a conditioned-medium model. In vivo, intra-articular Sema3a@ODCP preserved cartilage matrix and subchondral microarchitecture in rats exposed to chronic HCS. Discussion These findings support Sema3a@ODCP as a locally delivered gene-activated matrix with potential for osteochondral protection under environmental stress. The hydrogel provides a platform for coordinating immune modulation, mitochondrial functional improvement, and osteochondral preservation in the context of hypoxic–cold stress.