Ma José Montoya

RANKL/OPG in primary cultures of osteoblasts from post-menopausal women. Differences between osteoporotic hip fractures and osteoarthritis

The OPG/RANKL/RANK system is important in the balance between bone formation and resorption. We used primary human osteoblasts (hOBs) cells to examine the impact of 17-beta-estradiol (E2) or/and 1,25-dihydroxyvitamin D (1,25D) in OPG/RANKL system in 28 post-menopausal (PM) women; (a) with hip fracture (OP) or (b) with osteoarthritis (OA). The hOB from OP patients proliferated slower during the first stage, than the OA women (31.5+/-2.6 and 21.4+/-1.3 days, respectively, p<0.05). The OP group secreted significantly higher OPG protein levels than the OA women (10.1+/-2.6 and 4.4+/-0.8pmol/L, respectively, p<0.05). The 1,25D and 1,25D+E2 induce an increase in RANKL and RANKL/OPG mRNA expression in OP patients above 200% (p<0.05). HOBs from the osteoporotic hip initially proliferate slower but after reaching the first cellular confluence, the proliferation rate is equal in both groups. Furthermore, hOBs from hips with OP present a higher protein secretion of OPG, and higher RANKL and RANKL/OPG expression ratio in response to 1,25D and 1,25D+E2, than hOBs from OA women. All this could suggest that the greater bone loss that characterizes OP patients can be mediated due to differences in the secretion and expression of the RANKL/OPG system in response to different stimuli.

Alendronate and raloxifene affect the osteoprotegerin/RANKL system in human osteoblast primary cultures from patients with osteoporosis and osteoarthritis.

The osteoprotegerin/RANKL system modulates bone remodelling. Alendronate and raloxifene are anti-resorptive drugs effective in osteoporotic disease. They reduce fracture risk, the activity of bone remodelling and increase bone mineral density. It is not known if they can exert a direct effect in osteoblasts via the osteoprotegerin/RANKL system. Our objective was to assess the effects of alendronate and raloxifene among osteoprotegerin production (ELISA), as well as osteoprotegerin and RANKL expression (RT-PCR), in primary cultures of human osteoblasts (hOB). We compared 17 osteoporotic patients with 16 patients affected by osteoarthritis in basal conditions and after incubation with alendronate (10(-6) M), raloxifene (10(-7) M) or 17-β estradiol (10(-7) M) for 24 h. The statistical analysis was determined by ANOVA. Osteoprotegerin protein secretion in hOB cultures was higher in patients with osteoporosis than osteoarthritis. Osteoprotegerin secretion levels remained unchanged after each treatment. The osteoporotic group was more sensitive to treatment. Both raloxifene (34%) and estradiol (37%) increased osteoprotegerin mRNA expression, and alendronate (118%) and raloxifene (61%) increased the mRNA expression of RANKL. The RANKL/osteoprotegerin mRNA ratio was higher in osteoporotic than osteoarthritic patients. In the osteoporotic group, the RANKL/osteoprotegerin mRNA ratio was significantly increased after treatment with alendronate (112%) and after treatment with raloxifene (60%). These results indicate a direct action of alendronate and raloxifene on hOB cultures from osteoporotic patients, and the cited drugs are able to modulate the osteoprotegerin/RANKL system.

Calcitonin reserve in healthy women and patients with postmenopausal osteoporosis

SummaryA deficit of immunoreactive calcitonin (iCT) has been found in women with postmenopausal osteoporosis (PM-OP), however, recent studies assessing the monomeric fraction of calcitonin (exCT) do not seem to confirm these findings. We have measured serum levels of iCT by radioimmunoassay (RIA) and exCT (chromatography and RIA) at 0, 5, 10, and 20 minutes after the i.v. infusion of 2 mg calcium/kg body weight in four different groups of women: (1) 12 healthy premenopausal women (HPM), (2) 16 early postmenopausal women (EPM), (3) 16 postmenopausal women within more than 2 years of menopause (LPM), and (4) 24 women with PM-OP. In the HPM group, iCT levels increased significantly 5 and 10 minutes after finishing the calcium infusion (P<0.05); this did not occur in the other three groups. The exCT levels in the HPM and LPM groups showed a significantly greater increase than in the EPM and PM-OP groups at 5 minutes (P<0.05) and at 10 and 20 minutes (P<0.01) after infusion. The behavior of the PM-OP and EPM groups was similar throughout the study. We conclude that there is a calcitonin reserve deficiency in the first years after menopause, which recovers later. This hormone deficiency could explain the accelerated bone loss that takes place at this time of life. The patients with PM-OP also show this deficit, and this may play an ethiopathogenic role in the production of the disease.

Differences in osteogenic and apoptotic genes between osteoporotic and osteoarthritic patients

BackgroundOsteoporosis is a metabolic disorder characterized by a reduction in bone mass and deterioration in the microarchitectural structure of the bone, leading to a higher risk for spontaneous and fragility fractures.The main aim was to study the differences between human bone from osteoporotic and osteoarthritic patients about gene expression (osteogenesis and apoptosis), bone mineral density, microstructural and biomechanic parameters.MethodsWe analyzed data from 12 subjects: 6 with osteoporotic hip fracture (OP) and 6 with hip osteoarthritis (OA), as the control group. All subjects underwent medical history, analytical determinations, densitometry, histomorphometric and biochemical study. The expression of 86 genes of osteogenesis and 86 genes of apoptosis was studied in pool of bone samples from patients with OP and OA by PCR array.ResultsWe observed that most of the genes of apoptosis and osteogenesis show a decrease in gene expression in the osteoporotic group in comparison with the osteoarthritic group. The histomorphometric study shows a lower bone quality in the group of patients with hip fractures compared to the osteoarthritic group.ConclusionsThe bone tissue of osteoporotic fracture patients is more fragile than the bone of OA patients. Our results showed an osteoporotic bone with a lower capacities for differentiation and osteoblastic activity as well as a lower rate of apoptosis than osteoarthritic bone. These results are related with structural and biochemical parameters.

Modifying RANKL/OPG mRNA expression in differentiating and growing human primary osteoblasts.

The OPG/RANKL system in primary cultures of human osteoblasts has been studied by different authors. However, very few studies have been performed on gene expression of RANKL and OPG at different stages of maturation on human osteoblast cultures. The effect of 17- beta-estradiol and 1,25dihydroxyvitamin D3 on the OPG/RANKL system is not known during the different states of cellular maturation. In this work we quantified OPG and RANKL protein levels (ELISA) and the mRNA of OPG, RANKL, collagen type I, alkaline phosphatase, and osteocalcin (semi-quantitative RT-PCR) in human osteoblasts. We analyzed these in basal conditions and after incubation with 17- beta-estradiol and 1,25dihydroxyvitamin D3 in the first and second phases. We found that OPG secretion and expression levels increased throughout cellular growth. RANKL proteins were detected only in the first stage, and the expression increased throughout the first phase. Thus, the RANKL/OPG ratio was higher in immature osteoblasts than in mature osteoblasts. The evolution of RANKL gene expression was related to collagen I and alkaline phosphatase, while OPG was related to osteocalcin. We observed no modifications after estradiol and 1,25dihydroxyvitamin D3 treatment. Our results suggest that the OB is a positive stimulator at precocious stages of differentiation on osteoclastogenic modulates.

Microstructural trabecular bone from patients with osteoporotic hip fracture or osteoarthritis: its relationship with bone mineral density and bone remodelling markers.

Osteoporosis (OP) and osteoarthritis (OA) are the most prevalent musculoskeletal disorders in the elderly but the relationship between them is unclear. The purposes of this study are to analyze the bone turnover markers (BTM), bone mineral density (BMD) and the structural and mechanical properties of trabecular bone in patients with OP and OA, and to explore the relationship between these two diseases. We studied 12 OP patients and 13 OA patients. We analyzed BTM (β-CrossLaps and PINP), BMD and microstructural and biomechanical parameters (micro-CT). Our results were: OP group has higher levels of β-CrossLaps and lower BMD at the femoral neck. Also, OP patients have a decreased volume of trabecular bone and less trabecular number, with architecture showing prevalence of rod-like trabeculae and worse connectivity than OA patients. The biomechanical parameters were worse in OP patients. BMD was correlated with almost all the structural and biomechanical parameters. Moreover, β-CrossLaps was negatively correlated with hip BMD and with bone surface density and positively with trabecular separation. BTM, BMD and bone microstructural changes in osteoporosis are opposite to those of OA. These findings justify a less resistant bone with higher risk of fragility fractures in OP patients. These histomorphometric and biomechanical changes may be suspected by measuring of BMD and β-CrossLaps levels.