Ação do paratormônio humano (1-34) no tecido ósseo de ratas osteopênicas. / Action of parathyroid hormone (1-34) on bone tissue in osteopenic rats.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Introduction: Bone remodeling depends upon a variety of systemic and local factors. Systemic factors that have a direct effect include the parathyroid hormone which together with other factors maintains bone homeostasis. Biosynthetic human parathyroid hormone (1-34) [hPTH(1-34)] has been used to stimulate bone formation in patients with osteoporosis. However, the effects of hPTH (1-34) on bone tissue are not well unknown. Aim: The aim of this study was investigate the effects of the short-term intermittent treatment with hPTH (1-34) in different doses on bone constituents of osteopenic rats. Methods: Forty 6-month-old ovariectomized osteopenic rats were divided into four groups GI group injected with saline solution (control); GII group injected with 0.3μg/kg/day; GIII group injected with 5μg/kg/day; GIV group injected with 0.25 μg/kg 3 times per week. After one month of treatment the animals were sacrificed and the length and thickness of the femurs/tibias were measured. Measurements for sulfated glycosaminoglycans (GAGs), hyaluronic acid (HA) and physical and biomechanical properties (3-point bending) were conducted in unfixed/ fresh tissue. Biomechanical and physical properties were assessed from the tibias. Distal femurs were fixed in 4% formaldehyde (derived from paraformaldehyde) buffered with 0.1M sodium phosphate at pH 7.2 for 4 days. After decalcification in 25% formic acid (pH 2,0), the samples were processed for histology, histomorphometric analyses, histochemistry (Alcian blue pH 2.5 and pH 0.5 and Picro-sirius polarization), immunohistochemistry for hyaluronic acid and TUNEL method. Results: There was an increase only on thickness tibia in GIII group. GIII revealed an increase in bone mineral density, bone density and organic material when compared to control group, but there was a decreased in water bone in GIII. The 3-point bending test showed no difference among the groups. Bone volume (BV/TV) was higher in GIII (6%). Cortical bone thickness (Ct.Wi) increased in GII and GIII. A decrease of sulfated GAGs was observed in GIII and GIV, as judged by the Alcian blue method and the sulfated GAGs assessment revealed a decrease of chondroitin sulfate only in the group that received the highest dose of hPTH (1-34). The ELISA method revealed a significant increase of HA in GIII, although a reduction as shown by immunohistochemistry in treated groups. An increase in the green birefringence (type I immature collagen) was observed on cortical and trabecular bone in all treated groups. The percentage of TUNEL positive osteocytes was significantly increased in the cortical and trabecular bone of GIV. Furthermore, we observed many TUNEL-positive cells in the periosteum of GIV group. Conclusion: Our results show that hPTH (1-34) administered intermittently in shortterm accelerates bone remodeling process by promoting bone formation and restoration of bone microarchitecture in osteopenic rats in a dose-dependent way.

ASSUNTO(S)

tecido ósseo paratormônio remodelação óssea matriz óssea morfologia osteoporose morfologia

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