Effects of ageing on proliferative ability, and the expressions of secreted protein, acidic and rich in cysteine (SPARC) and osteoprotegerin (osteoclastogenesis inhibitory factor) in cultures of human periodontal ligament cells

Secreted protein, acidic and rich in cysteine (SPARC) has been suggested to play an important role in wound repair and mineralization. Osteoprotegerin /osteoclastogenesis inhibitory factor (OPG/OCIF) is a secreted protein that inhibits the maturation, activity and survival of osteoclasts. An examinat ion of the changes in expression of these proteins as well as their prolife rative ability according to ageing in cultured cells may elucidate characte ristic changes in periodontal tissues induced by ageing. In the present stu dy, proliferative ability and the expression of SPARC and OPG/OCIF were com pared between cultures of human periodontal ligament (HPL) cells obtained f rom young and senior donors (in vivo cellular ageing) as well as in culture s of HPL cells at early and late passages (in vitro cellular ageing). Cumul ative population doubling levels and cell population doubling time of HPL c ells from young donors were greater and shorter, respectively, than those o f HPL cells from senior donors. Levels of SPARC mRNA in HPL cells increased with cellular ageing in vivo. No change in the levels of OPG/OCIF mRNA in HPL cells with cellular ageing in vivo was observed. The changes in prolife rative ability and the mRNA levels of SPARC and OPG/OCIF with cellular agei ng in vitro were similar to those with ageing in vivo. This study demonstra ted for the first time a relationship between in vivo and in vitro cellular ageing in the functional changes in HPL cells. These findings suggest that the impairment of periodontal ligament repair with ageing is due to the de crease in proliferative ability in HPL cells with ageing. Furthermore, the increase in SPARC with ageing may be related to changes in metabolism of pe riodontal ligament that occur with ageing. (C) 2000 Elsevier Science Irelan d Ltd. All rights reserved.