Isolation of the chondrocyte and chondroprogenitor/stem cell from human articular cartilage, comparison of the chondrogenic capacity of these two cell lines

It has been reported that progenitor / stem cells might be present in human articular cartilage. In articular cartilage stem cell studies it is stated that cells with stem cell properties can be isolated with some techniques. Therefore, we aimed to isolate and culture the chondrocytes and progenitor/stem cells from adult human femoral distal articular cartilage, and investigate the expression of stem cell markers, differentiation capacities and ultrastructural features of these cells. In our study, chondrocytes were isolated from adult human articular cartilage biopsies with pronase/collagenase digestion. Full-depth chondrocytes were cultured in different culture plates and single cell suspension were seeded on the fibronectin coated petri dishes for isolation of colony cells. Following seeding of chondrocytes, colony cells were selected and seeded on a different culture dish. Briefly, the parameters of this study were; determining the expression of stem cell markers such as CD90, STRO-1, CD105, C166 with flow cytometry and immunofluorescence techniques, induction of chondrocytes and colony cell lines to chondrogenesis, adipogenesis and osteogenesis, investigation of ultrastructure of these two cell lines. Our findings can be summarized as; expression levels were similar between chondrocyte and colony culture cell lines. Our immunofluorescence studies showed that, expressions of all markers were observed in two cell lines, and expression intensity of colony culture cell line was higher than chondrocyte culture cell line after a long-term culture period. On cell differentiation assay results, while chondrocyte culture cell lines were more efficient in the process of chondrogenesis, colony cells were effective in the process of adipogenesis and osteogenesis. When we analyzed the ultrastructure of these two cell lines, we observed more expanded rough endoplasmic reticulum (RER) and ribosomes but less lysosomes in colony culture cell line cells than chondrocyte cell line. In conclusion, according to the results of this study we can say that, there are progenitor/stem cells within the adult articular cartilage which are capable of mesenchymal stem cells (MSC) properties. Moreover, following the long-term culture period, chondrocytes may gain similar features with colony cells.