David Guede

Effects of Nrf2 Deficiency on Bone Microarchitecture in an Experimental Model of Osteoporosis

Objective. Redox imbalance contributes to bone fragility. We have evaluated the in vivo role of nuclear factor erythroid derived 2-related factor-2 (Nrf2), an important regulator of cellular responses to oxidative stress, in bone metabolism using a model of postmenopausal osteoporosis. Methods. Ovariectomy was performed in both wild-type and mice deficient in Nrf2 (Nrf2−/−). Bone microarchitecture was analyzed by μCT. Serum markers of bone metabolism were also measured. Reactive oxygen species production was determined using dihydrorhodamine 123. Results. Sham-operated or ovariectomized Nrf2−/− mice exhibit a loss in trabecular bone mineral density in femur, accompanied by a reduction in cortical area in vertebrae. Nrf2 deficiency tended to increase osteoblastic markers and significantly enhanced osteoclastic markers in sham-operated animals indicating an increased bone turnover with a main effect on bone resorption. We have also shown an increased production of oxidative stress in bone marrow-derived cells from sham-operated or ovariectomized Nrf2−/− mice and a higher responsiveness of bone marrow-derived cells to osteoclastogenic stimuli in vitro. Conclusion. We have demonstrated in vivo a key role of Nrf2 in the maintenance of bone microarchitecture.

Effects of PTH (1-84) on bone quality in a validated model of osteoporosis due to androgenic deprivation.

Abstract Aim: The purpose of this study was to evaluate the effect of parathyroid hormone (PTH) (1–84) in a model of male osteoporosis induced by orchidectomy in rats. Methods: Six-month-old Wistar rats were used as follows: SHAM (simulated orchidectomy), orchidectomized (ORX), ORX + PTH1 (ORX and treated with 10 µg/Kg/d of PTH 1–84) and ORX + PTH2 (ORX and treated with 50 µg/Kg/d of PTH 1–84) over 3 months, with treatment beginning three months after orchidectomy. Results: Orchidectomy resulted in a decreased of femoral and lumbar bone mineral density (BMD), a worsening of trabecular and cortical microarchitecture and a decrease in biomechanical properties. Both doses of PTH (1–84) partially (low dose) or totally (high dose) restored the ORX-induced changes. Serum C-telopeptide of type I collagen/5b isoenzyme of tartrate-resistant acid phosphatase (CTX/TRAP) resorption index increased after orchidectomy. Osteocalcin (bone Gla protein; BGP) levels were not affected by orchidectomy. PTH (1–84) treatment did not produce any changes in the levels of CTX/TRAP with respect to the ORX group. BGP levels increased with PTH treatment. Conclusion: PTH (1–84) is able to restore the adverse effects of orchidectomy on bone as measured by BMD, microstructural and biomechanical properties and bone remodeling markers.

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.

Impact of estrogens on atherosclerosis and bone in the apolipoprotein E-deficient mouse model.

ObjectiveThe common inflammatory pathophysiology has nourished the hypothesis of a relationship between osteoporosis and cardiovascular disease. Estrogens are key agents in the modulation of both processes. We investigated whether induction of atherosclerosis affects bone and whether estrogens modulate both processes. MethodsFemale apolipoprotein E–deficient mice (a well-established model of atherogenesis) were ovariectomized or falsely operated and fed either standard diet or high-fat diet (HFD). Six animals were included in each of the four groups. To clarify mechanisms, we treated preosteoblastic MC3T3-E1 cells with mouse serum. ResultsPhysiological levels of estrogens in falsely operated mice limited atherosclerotic burden in the thoracic aorta, but not in the aortic arch. Bone resorption, as assessed by C-telopeptides, was increased by ovariectomy in animals fed standard diet, but not in animals fed HFD. Bone microstructural properties at the distal femur showed deteriorated trabecular architecture in bone volumetric fraction and trabecular number after ovariectomy, but trabecular pattern factor, trabecular thickness, trabecular spacing, or the structural model index remained unchanged. Changes in cortical parameters were not significant. Volumetric bone mineral density was reduced in trabecular bone, but not in cortical bone, in ovariectomized mice fed standard diet. Preosteoblastic MC3T3-E1 cells exhibited increased cellular proliferation and viability and alkaline phosphatase activity after treatment with sera from animals fed HFD. ConclusionsEndogenous estrogens partially reduce atherogenic burden in female apolipoprotein E–deficient mice. Ovariectomy increases bone resorption, but not under exacerbated proatherogenic conditions induced by HFD. The absence of apolipoprotein E might have an influence on the asymmetric responses of atherogenesis and bone resorption.

Effect of lysophosphatidic acid receptor inhibition on bone changes in ovariectomized mice

Pharmacological inhibition of signaling through lysophosphatidic acid (LPA) receptors reduces bone erosions in an experimental model of arthritis by mechanisms involving reduced osteoclast differentiation and bone resorption and increased differentiation of osteoblasts and bone mineralization. These results led us to hypothesize that LPA receptor inhibition would be beneficial in osteoporosis. Our aim was to test this hypothesis with the LPA receptor antagonist, Ki16425, in ovariectomized mice, a model of postmenopausal osteoporosis. Ovariectomized mice treated with Ki16425 showed bone loss similar to that observed in the controls. Osteoblast markers, Alpl,Bglap and Col1a1, were increased at the mRNA level but no changes were detected in serum. No additional difference was observed in the Ki16425-treated mice relative to the ovariectomized controls with regard to osteoclast function markers or assays of matrix mineralization or osteoclast differentiation. Thus, pharmacological inhibition of LPA receptor was not beneficial for preventing bone loss in ovariectomized mice, indicating that its favorable effect on bone remodeling is less general than hypothesized.

Effects of Kalsis, A Dietary Supplement, on Bone Metabolism in the Ovariectomized Rats

We studied the ability of Kalsis, a food supplement that contains selenium, citric acid, and vitamin E, to prevent the effects of ovariectomy on bone loss. Six-month-old, Wistar female rats were studied. Groups (n = 12): SHAM: sham-operated rats; OVX: ovariectomized rats, treated with vehicle; OVX + Kalsis: ovariectomized rats treated with Kalsis (25 mg/kg/day) for 3 months. Bone mineral density (BMD) was determined by DXA in lumbar spine and femur. Computerized microtomography (μCT) in femur and serum osteocalcin (BGP), aminoterminal propeptide of procollagen I (PINP), β-isomer of carboxyterminal telopeptide of collagen I (CTX), and 5b isoenzyme of tartrate-resistant acid phosphatase (TRAP) were performed. Treatment with Kalsis prevented BMD loss in OVX group. μCT showed a decrease in BV/TV, and trabecular number, and an increase in trabecular separation in OVX rats. Kalsis administration attenuated partially bone loss observed by μCT due to ovariectomy. BGP, PINP, and the resorption index (CTX/TRAP) were increased in OVX group. Treatment with Kalsis maintained this increase. The mechanism of action of this supplement is not through a decrease in bone remodelling rate. The antioxidant action of this food supplement, due to the synergism of all its components, as a cause of its beneficial effect is suggested.

Up-Regulation of the Inflammatory Response by Ovariectomy in Collagen-Induced Arthritis. Effects of Tin Protoporphyrin IX

We have studied the influence of ovariectomy on the inflammatory response and bone metabolism on CIA as a model of postmenopausal arthritis as well as the effects of tin protoporphyrin IX (SnPP), a heme oxygenase inhibitor. Ovariectomy in non-arthritic mice produced increased serum PGD2 levels and up-regulated the expression of COX-2, h-PGDS, l-PGDS, and HO-1 in the joints. In CIA, ovariectomy potentiated the inflammatory response with higher levels of serum IL-6 and MMP-3, local PGD2 and MMP-3 as well as trabecular bone erosion. In OVX-CIA, SnPP decreased the serum levels of IL-6, MMP-3, and PGD2; down-regulated TNFα, COX-2, hPGDS, PGD2, PGE2, and MMP-3 in joint tissues; and also decreased focal bone loss in the inflamed joint. Ovariectomy up-regulates inflammatory mediators in non-arthritic and in arthritic animals. In the OVX-CIA model, SnPP exerts anti-inflammatory effects which are not associated with the prevention of systemic bone loss.

Sirolimus and tacrolimus rather than cyclosporine A cause bone loss in healthy adult male rats

The aim of this work was to study the effects of cyclosporine (CsA), tacrolimus (FK-506), and rapamycin (RAPA) on bone mass, femoral microstructure, femoral biomechanical properties, and bone remodeling in healthy adult male rats. Forty-eight 5-month-old male Wistar rats were used. CsA (2 mg/kg/day), FK-506 (3 mg/kg/day), RAPA (1.25 mg/kg/day), or water (0.5 ml/rat/day, control group) were administered orally for 3 months. After sacrifice, mean values of immunosuppressants in blood were: CsA (670.4 ng/ml), FK-506 (19.2 ng/ml), and RAPA (4.8 ng/ml). Levels of biochemical parameters were normal in all groups. Femoral BMD was decreased in FK-506 and RAPA groups and lumbar BMD in FK-506 group. Trabecular volume fraction (BV/TV) decreased only in FK-506 group. RAPA and CsA affected femoral cortical structure, but FK-506 did not. FK-506 produced an increase in bone remodeling, and CsA a decrease. FK-506 group showed a decrease in biomechanical parameters relative to all groups. RAPA group showed a decrease in ultimate stress vs control group, and CsA group presented an increase in biomechanical parameters versus control group. We found that administration of both RAPA and FK-506 as monotherapy for healthy rats produced osteopenia. CsA treatment only produces slight damages in the cortical zone of the femur.

Cortical bone thickening in Type A posterior atlas arch defects: experimental report

BACKGROUND CONTEXT To date, no information about the cortical bone microstructural properties in atlas vertebrae with posterior arch defects has been reported. PURPOSE To test if there is an increased cortical bone thickening in atlases with Type A posterior atlas arch defects in an experimental model. STUDY DESIGN Micro-computed tomography (CT) study on cadaveric atlas vertebrae. METHODS We analyzed the cortical bone thickness, the cortical volume, and the medullary volume (SkyScan 1172 Bruker micro-CT NV, Kontich, Belgium) in cadaveric dry vertebrae with a Type A atlas arch defect and normal control vertebrae. RESULTS The micro-CT study revealed significant differences in cortical bone thickness (p=.005), cortical volume (p=.003), and medullary volume (p=.009) values between the normal and the Type A vertebrae. CONCLUSIONS Type A congenital atlas arch defects present a cortical bone thickening that may play a protective role against atlas fractures.

Comparative study of the effects of osteoprotegerin and testosterone on bone quality in male orchidectomised rats

Abstract Aim: The aim of this work is to compare the effects of osteoprotegerin (OPG) and testosterone on bone quality in a model of orchidectomised (ORX) rats. Methods: Three-month-old ORX or SHAM operated groups (n = 15 each group) were used. The SHAM and ORX groups received saline. There were two ORX groups, receiving OPG–Fc (10 mg/kg twice weekly) (ORX + OPG–Fc) or testosterone cypionate (1.7 mg/kg/weekly) for 8 weeks. After sacrifice, bone analysis by femoral and lumbar dual-energy X-ray absorptiometry and micro-computed tomography in femora were performed. Histological sections of vertebrae were dyed with hematoxylin–eosin or safranin. Serum osteocalcin (BGP), total alkaline phosphatase (ALP), and C-terminal telopeptide of type I collagen (CTX) were analyzed. Results: ORX resulted in femoral and vertebral bone loss and in microarchitectural deterioration. Treatment with OPG–Fc and testosterone recovered lumbar (L) and femoral (F) bone mineral densitometry bone mineral density (BMD) to SHAM levels. Femoral BMD was significantly higher after treatment with OPG–Fc than after testosterone treatment due to the presence of osteopetrotic changes in the metaphyseal region of long bones. Serum levels of ALP and CTX increased, while OPG levels were unchanged in ORX rats. Treatment with OPG–Fc decreased the levels of BGP, ALP, and CTX. Treatment with testosterone maintained biochemical markers of bone turnover at levels similar to or higher than those of ORX rats.