Recent studies have shed light on the cellular and molecular mechanisms that link subchondral bone remodelling and angiogenesis in knee osteoarthritis (OA). Type H vessels are a newly identified bone blood vessel characterized by high expression of CD31 and endomucin that are coupled with osteogenesis. Factors including mechanical loading, TGF-β1, platelet-derived growth factor type BB, the osteoprotegerin-RANK ligand-RANK system, osteopontin, mechanistic target of rapamycin, VEGF, stromal cell-derived factor l and prostaglandin E2 participate in the formation of type H vessels in osteoarthritic subchondral bone. In this review, we summarize the current understanding of type H vessels in knee OA, as well as the signalling pathways involved and potential therapeutic medicines. In future, the pathogenesis of knee OA could be further clarified by connecting type H vessels and the design of new disease-modifying osteoarthritis drugs. However, further experiments are needed to determine the upstream signals regulating type H vessel formation in osteoarthritic subchondral bone.
Keywords: PDGF-BB; TGF-β; knee osteoarthritis; subchondral bone; type H vessels.
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