The effects of low molecular weight hyaluronan on the cementogenic, ligamentogenic and osteogenic differentiation of human mesenchymal stem cells (hMSCs) and periodontal ligament cells (PDL-hTERTs)

Periodontitis is a highly prevalent chronic inflammatory oral disease. Hyaluronan (HA) is a non-sulfated glycosaminoglycan which helps anti-inflammatory and tissue repair. The aim of this study was to delineate the effects of various sized HA molecules on periodontal cells. Oligosaccharide nano HA and 150 kDA HA were used to stimulate human mesenchymal stem cells (hMSCs) and human periodontal ligament cells with human telomerase reverse transcriptase (PDLhTERTs), for 3, 7 and 21 days. HA receptors, CD44, receptor of hyaluronic acid mediated motility (CD168) and the Toll-like receptor (TLR)-4, have been substantially expressed in both cell types. In hMSCs CD44 and CD168 expression remained roughly unchanged during the entire observation period; in PDLhTERTs nano and/or the 150 kDa HA fragment significantly attenuated the expression of the CD44 and CD168 receptors. TLR4 expression was inhibited by nano and/or 150kDa HA in both cell types at day 21. The presence of HA reduced the transcription of the cementogenic markers, cementum-derived attachment protein (CAP) and cementum protein 1 (CEMP1), in both cell types, especially nano HA. Scleraxis (SCX), a ligamentogenic marker, remained almost unchanged irrespective of the specific stimulation condition. Early stage osteogenic marker alkaline phosphatase (ALP) was induced by the various stimulation conditions in both hMSCs and PDLhTERTs and stronger in the presence of nano and 150 kDa HA. Bone sialoprotein (BSP) remained roughly unchanged under stimulation. Osteogenic markers collagen type I alpha 1 (COL1A1) in both cell types and osteocalcin (OCN) in hMSCs were also enhanced by the HA fragments. However in PDLhTERTs OCN was inhibited by 150k HA. The osteogenic stimulation alone and together with HA lead to the highest calcium deposition. Taken together the current study revealed that small HA fragments cause differential effects on hMSCs and PDLhTERTs. Nano HA seemed to have more positive effects in osteogenic differentiation than 150kDa HA. These fragments seem to enhance the earlier steps of osteogenic differentiation in both types of stem cells but impair the expression of cementogenic differentiation markers and the mineralization of the ECM during osteogenesis within 21 days. Since the expression of scleraxis was unaffected HA seems to have no influence on the ligamentogenesis.