Involvement of hyaluronan in regulation of fibroblast phenotype

This study aimed to understand the role of the matrix polysaccharide, hyaluronan ( HA), in influencing the scarring process by assessing its impact on regulating fibroblast behavior. Donor-matched human oral and dermal fibroblasts were used as models of nonscarring and scarring fibroblast phenotypes, respectively. Phenotypic differences in these two fibroblast populations were assessed and related to differences in HA synthesis and assembly. The two fibroblast populations showed intrinsic differences in their response to the profibrotic cytokine, transforming growth factor- beta 1 (TGF beta 1), in that oral fibroblasts were resistant to TGF beta (1)-driven myofibroblastic differentiation. In dermal fibroblasts, differentiation was associated with an induction of HA synthase (HAS1 and HAS2) transcription and assembly of pericellular HA coats. In comparison, resistance to differentiation in oral fibroblasts was associated with failure of induction of HAS1 and HAS2 transcription and failure of pericellular coat assembly. Furthermore, inhibition of HA synthesis in dermal fibroblasts significantly attenuated TGF beta (1)-mediated differentiation. Interleukin-1 beta stimulation resulted in induction of HAS1 and HAS2 transcription but did not induce phenotypic differentiation or induce HA coat assembly. In addition, neither overexpression nor down-regulation of HAS1 ( the isoform uniquely deficient in nonscarring oral fibroblasts) influenced phenotypic differentiation. In conclusion, inhibiting HA synthesis modulates TGF beta (1)-dependent responses in these cells preventing fibroblast to myofibro-blast differentiation. Moreover, HA pericellular coat assembly, rather than HAS isoform expression, appears to be associated with phenotypic differentiation.