Hyaluronan (HA) plays a predominant role in tissue morphogenesis, cell migration, proliferation, and cell differentiation. The aims of the present study were to investigate whether (i) prolonged presence of high concentration (4.0 mg/mL) 800 KDa HA and (ii) pretreatment with HA can modify osteogenic differentiation of pig bone marrow stromal cells (pBMSC). Cell proliferation and mineralization were measured. Expression of differentiation-related genes was evaluated by means of real-time reverse transcription polymerase chain reaction (RT-PCR). HA increased cell proliferation on day 7. HA decreased the basal level of bone-related gene expression and increased the basal level of sox9 marginally during 7-day pretreatment with HA. HA increased calcium deposit on day 21. cbfa1, ALP, and type 1 alpha collagen (Col1) expression was increased when pBMSC were cultivated in osteogenic medium, whereas their expression was decreased in the presence of HA on day 7. On day 14, the addition of HA upregulated cbfa1 and ALP expression compared to osteogenic medium group; there was no significant difference in Col1 expression. At day 21, osteocalcin (OC) expression showed 2.5-fold upregulation over osteogenic medium. These results suggest that exogenous HA stimulates endogenous HA, which together may play a synergetic role in osteogenic differentiation under osteoinducing conditions although gene expression was inhibited at the early stage.
(c) 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.