Does the conditioned medium trigger the adipose-derived mesenchymal stem cells differentiation into Chondrocytes?

Background: Cartilage is an avascular tissue that has limited regenerative capacity. Stem cells, especiallymesenchymal stem cells (MSCs), have been regarded as a promising cell source for cartilage repair dueto their multi-lineage differentiation potential. Induction of mesenchymal stem cells into functional chondrocytesmay resolve the above problems in the cartilage repair. However, the imperative is to developeffective strategies for chondrogenic differentiation. The aim of this study is to evaluate if the induction ofadipose-derived mesenchymal stem cells (ADSCs) differentiation toward chondrocytes is possible withthe use of conditioned medium derived from chondrocytes culture. Material and methods: Conditioned medium (CM) from Normal chondrocyte cell line CRL 2648 was used to culture ADSCs, at the same time ADSCs with standard growth medium were used as a control. During this experiment, the phenotype was assessed using flow cytometry (CD90, CD44, CD45 and CD45), and Immunohistochemicalstaining was used to determine differentiation (anti-aggrecan, anti-CD15, anti-collagen II, anti-TRA-2-49). Results: ADSCs propagated rapidly in vitro and formed a homogenous fibroblast-like morphology. 0% of testedcells showed the expression of CD90 and CD44, while more than 90% did not reveal the expression ofCD34 and CD45. Results obtained in this study showed weak cytoplasmatic expression of aggrecanand alkaline phosphatase (TRA protein) and lack of CD151 expression. However, the majority of ADSCsexpanded with CM expressed type II collagen indicating that the chondrocyte-secreted factors inducedchondrogenic commitment during expansion. Conclusions: In the natural environment of living organisms, the chondrogenic differentiation of stem cells involve multiple signalling pathways. We can, to an extent mimic these signals in vitro however, for the clinicalpurposes it is very important to develop well-defined and efficient in vitro protocols. Our results indicatethat CM may regulate and induce differentiation of ADSCs into the chondrocyte lineage and can servealso as an in vitro model for studying specific lineage commitment