Age-dependent expression of osteoblastic phenotypic markers in normal human osteoblasts cultured long term in the presence of dexamethasone

Abstract

We have previously shown that osteoblasts derived from trabecular bone explants and cultured long term in 10 nM dexamethasone ((HOB + DEX) cells) exhibited properties consistent with a more differentiated phenotype compared with those grown in the absence of dexamethasone ((HOB-DEX) cells). To characterize these two cell models further, we measured the steady-state mRNA levels of the phenotypic markers alkaline phosphatase (ALP), collagen type I (COLL) and osteocalcin (OC), OC production, and the activities of ALP and parathyroid hormone (PTH)-stimulated adenylate cyclase. These findings were then correlated with the age and sex of the bone donors. Long-term culture in dexamethasone significantly increased ALP and OC mRNA levels and the activities of ALP and PTH-stimulated adenylate cyclase but not OC production, in (HOB + DEX) compared with (HOB-DEX) cells (p < 0.05). When the data were examined with respect to the age of the bone donor, age-dependent differences in the expression and responses to dexamethasone were apparent. ALP and PTH-stimulated adenylate cyclase activities decreased with increasing age of the bone donor in (HOB-DEX) and (HOB + DEX) cells (p < 0.05). There were no significant correlations between phenotypic marker mRNA levels and bone donor age in (HOB-DEX) and ((HOB + DEX) cells. All age-dependent decreases in ALP and PTH-stimulated cyclase activities were enhanced in the (HOB + DEX) cells. However, when the data were examined according to the sex of the bone donor, there were no differences in mRNA levels, OC production, or ALP and cyclase activities between cells from male and female donors. These results indicate an age dependence in the expression of osteoblastic markers in human bone cells at different stages of differentiation: thus osteoblastic cultures derived from older donors are likely to contain fewer osteoprogenitor cells, lower levels of glucocorticoid receptors or represent more differentiated osteoblasts compared with those derived from younger donors.

In vitro osteoblast-like cell metabolism in spondylodesis-a tool that may predict fusion capacityA prospective study in 50 patients with a 1-year follow-up

“…An explanation may be the small size of the sample due to the limitations of experiment. Differences caused by age in the expression of AP activity were apparent, since AP declined with the age of the bone donors, an observation which accords with that of other studies (Pfeilschifter et al 1993, Sutherland et al 1995. Sutherland et al suggested a defect in the synthesis of AP mRNA in older donors, because they found an age-dependent decline in AP mRNA levels.…”

“…During the last two decades, the culture of osteoblast-like cells using primary cultures of untransformed cells derived from cancellous bone explants has become an important experimental model (Christensen et al 1999, Kudelska-Mazur et al 1999. These cultured osteoblasts provide a tissue-culture model for studying cellular and molecular mechanisms associated with bone biology (Termine et al 1990, Fedarko et al 1992, Pfeilschifter et al 1993, Sutherland et al 1995, Kassem et al 1997, DʼIppolito et al 1999, Katzburg et al 1999. We hypothesized that primary human osteoblast-like cell metabolism in cultures could provide an in vitro biological model for predicting the fusion capacity in the individual patient.…”

Fetal bone cells for tissue engineering

“…Adult bone cells showed the same pattern for ALP enzymatic activity, with an earlier induction for the full differentiation mix, compared with the group receiving only dexamethasone additionally to ascorbic acid and h-glycerophosphate (data not shown). For adult cells, ALP enzymatic activity was observed to vary according to the age of the donor as previously demonstrated [64].…”

Characterization of 11beta-hydroxysteroid dehydrogenase activity and corticosteroid receptor expression in human osteosarcoma cell lines

“…Several previous studies have demonstrated the expression of GR in OB and OB-like cells (Chen et al 1986, Masuyama et al 1992, Subramaniam et al 1992. A more recent report has suggested that the levels of this receptor may vary according to the differentiation status of OBs (Sutherland et al 1995). However, it is clear from studies in vitro and in vivo that an equally important influence on the positive and negative effects of glucocorticoids is the concentration of hormone which is available to the GR (Lukert & Raisz 1990, Scutt et al 1996.…”