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

Abstract

Background: Cartilage is an avascular tissue that has limited regenerative capacity. Stem cells, especially mesenchymal stem cells (MSCs), have been regarded as a promising cell source for cartilage repair due to their multi-lineage differentiation potential. Induction of mesenchymal stem cells into functional chondrocytes may resolve the above problems in the cartilage repair. However, the imperative is to develop effective strategies for chondrogenic differentiation. The aim of this study is to evaluate if the induction of adipose-derived mesenchymal stem cells (ADSCs) differentiation toward chondrocytes is possible with the 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 Immunohistochemical staining 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 tested cells showed the expression of CD90 and CD44, while more than 90% did not reveal the expression of CD34 and CD45. Results obtained in this study showed weak cytoplasmatic expression of aggrecan and alkaline phosphatase (TRA protein) and lack of CD151 expression. However, the majority of ADSCs expanded with CM expressed type II collagen indicating that the chondrocyte-secreted factors induced chondrogenic 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 clinical purposes it is very important to develop well-defined and efficient in vitro protocols. Our results indicate that CM may regulate and induce differentiation of ADSCs into the chondrocyte lineage and can serve also as an in vitro model for studying specific lineage commitment.