Age-related differences in the expression of receptors for TGF-β in human osteoblast-like cells in vitro

Abstract

The cell surface expression of receptors for TGF-beta was studied in human osteoblasts derived from femoral trabecular bone of a total of 19 patients aged 2-83 years. All cell populations investigated showed a similar profile of expression of TGF-beta receptors (TbetaR) I, II and III (betaglycan). There were no significant differences in cell differentiation or proliferative behaviour between the age groups. The TGF-beta receptor number per cell significantly increased with age, while the receptor affinity tended to decrease. IGF-I did not influence TbetaR expression in vitro. The results indicate an age-dependent and IGF-I independent increase of osteoblastic TGF-beta receptors in human osteoblast-like cells in vitro.

The aging of Wolff's ?law?: Ontogeny and responses to mechanical loading in cortical bone

“…Bä tge et al (2000) studied the senescence of receptors I, II, and III for TGF-␤ in osteoblasts from samples of human femoral cortex in 19 patients between 2-83 years of age. The patients' osteoblasts showed no significant change in the ability of the cells to differentiate or proliferate with age, but the number of TGF-␤ receptors per cell increased significantly with age (Bä tge et al, 2000). The increase in TGF-␤ receptors in older cells appeared to be independent of IGF-I concentrations (Bä tge et al, 2000).…”

“…Cell senescence accounts for part of the changes in the way that the skeleton responds to mechanical stimuli. Populations of osteoprogenitor cells undergo a marked senescence in adulthood, with a large decline in cell numbers and decreased responsiveness of the remaining cells to mechanical stimuli, estrogen, IGF-I, and TGF-␤ (Nishida et al, 1999;Muschler et al, 2001;Turner et al, 1995c;Tanaka and Liang, 1996;Ankrom et al, 1998;Bä tge et al, 2000). Although the mechanisms responsible for bone modeling and remodeling are not yet completely understood, the pattern of responses across the life span is fairly clear.…”

“…Studies of living people show that activities during childhood and particularily during the adolescent growth spurt can play an important role in establishing adult morphology K. Khan et al, 2000;Bass et al, 2002;MacKelvie et al, 2002), which subsequently becomes increasingly difficult for the body to change (K. Khan et al, 1998;Kontulainen et al, 1999Kontulainen et al, , 2001, especially as its oseoprogenitor cells senesce (Nishida et al, 1999;Bä tge et al, 2000;Muschler et al, 2001;Turner et al, 1995c). The existence of this "window of opportunity" for the body to grow strong, thick (robust) bones has important implications for attempts to interpret skeletal morphology.…”

“…The patients' osteoblasts showed no significant change in the ability of the cells to differentiate or proliferate with age, but the number of TGF-␤ receptors per cell increased significantly with age (Bä tge et al, 2000). The increase in TGF-␤ receptors in older cells appeared to be independent of IGF-I concentrations (Bä tge et al, 2000). Similarly, Ankrom et al (1998) reported that the number of estrogen receptor-␣ molecules per osteoblast doubled between their sample of younger and older (Ͼ50 years) women.…”

Transforming growth factor‐beta 1 (TGF‐β1) prevents the age‐dependent decrease in bone formation in human osteoblast/implant cultures

“…The TGF‐β Type II receptor complex then binds to the Type I receptor, thus causing phosphorylation and activation of the Type I receptor serine/threonine kinase activity and initiation of the post receptor signaling cascade 45. The cell surface expression of TGF‐β receptors was studied in human osteoblasts derived from femoral trabecular bone in 19 patients aged 2–83 years old 56. With the increasing donor age, primary human osteoblasts had significantly higher number of TGF‐β receptors per cell, whereas the receptor affinity tended to decrease.…”