Fig. 1

Isolation, expansion, and immunophenotyping of mCPCs from paired grade 1–2 and grade 3–4 OA cartilage. a Representative MRI image of late-stage idiopathic KOA shows Outerbridge grade 3–4 cartilage lesions in the medial tibial plateau and grade 1–2 cartilage lesions on the lateral side. b Osteoarthritic cartilage specimen of the tibial plateau obtained from the same patient. The cartilages from marked areas were harvested. The cartilaginous tissues were separated from the subchondral bone, minced into pieces, mildly digested, and incubated in culture medium. c mCPCs migrated from paired OA cartilage pieces after 15 days of cultivation. The cartilage pieces were retained and maintained until passage 3 (arrowhead). d Immunophenotype markers (CD29, CD31, CD44, CD45, CD73, CD90, CD105, CD166, and CD271) of mCPCs from paired grade 1–2 and grade 3–4 cartilage. Red lines indicate isotype controls. e The expression of CD271 in mCPCs from grade 1–2 cartilage was significantly lower compared with those from grade 3–4 cartilage (n = 6 donors, with each repeated in replicates, p = 0.034). Scale bars in d represent 200 μm. mCPCs, migratory chondrogenic progenitor cells; KOA, knee osteoarthritis