However, cartilage does become invaded with blood vessels and can undergoendochondral ossification in early stages of limb development or when itsintegrity is disrupted as seen in osteoarthritis (OA).14,15Most works studying the progression OA have found prevalent pro-angiogenicfactors, most notably one of the best-known factors driving angiogenesis,vascular endothelial growth factor (VEGFa).16 Interestingly, VEGFa is not only expressed in OA cartilage but alsoin mature healthy cartilage and chondrocyte-derived tissue-engineeredconstructs17, -19 that will not beinvaded by blood vessels. The gene discussed is VEGFA; the disease is osteoarthritis.