Hyaluronan influence on the onset of chondrogenic differentiation of mesenchymal stem cells
OBJECTIVES: Hyaluronan (HA) is an abundant component of chondrogenic tissue hence it is often used as a fundamental Constituent in cartilage tissue substitutes. However, effects of different molecular weight HA on chondrogenic differentiation are not clear. The aim was to evaluate modulation of mesenchymal stem cell (MSC) early chondrogenesis by HA of molecular weights 100, 600 and 1500 kDa. METHODS: HA was applied on MSCs cultured in a pellet system for one, two and three weeks. Chondrogenesis was evaluated by determinations of gene expression of transcription factor Sox-9 and extracellular matrix proteins collagen type II and XI, aggrecan, and COMP by Real-Time PCR and completed with histological analysis. RESULTS: Upon chondrogenic induction, the respective pellets revealed active transcription of the chondrogenic genes together with proceeding accumulation of glycosaminoglycan (GAG) rich extracellular matrix. Sox-9 was also expressed in non-chondrogenic MSC controls. HA treated pellets were not significantly influenced on day 7 of culture. However, on day 14, lowered expression in some of the extracellular matrix proteins appeared together with a moderately smaller amount of GAG content in pellet sections. Nevertheless, the analysis on day 21 has demonstrated that HA did not affect the outcome of the differentiation by the end of the culture. Any difference regarding the molecular weight of the HA was not found. CONCLUSIONS: It could be speculated that HA induced a time shift in the phase of the dominant matrix protein onset which was in full compensated by the end of the evaluated time period. Thus, data suggest that HA of any tested molecular weight does not significantly modulate chondrogenesis of MSCs in pellet system.