Abaloparatide promotes bone repair of vertebral defects in ovariectomized rats by increasing bone formation.

Osteoporotic vertebral fracture (OVF) is the most common type of osteoporotic fracture and is associated with immobility and mortality. Bone anabolic agents, such as abaloparatide (ABL), are usually administered to patients with OVF to prevent subsequent fractures. Although several studies have shown that bone anabolic agents promote healing of long bone fractures, there is little evidence of their healing effect on vertebral bone fractures. In the present study, we investigated the effect of ABL on vertebral bone defects using ovariectomized (OVX) rats with vertebral body drill-hole defects, an animal model of OVF. Eight-week-old female Sprague-Dawley rats were subjected to OVX, followed by the 32-36 days of bone depletion period, once-daily subcutaneous ABL was administered to OVX rats at a dose of 30 µg/kg for a maximum of 6 weeks from the day of the vertebral defect surgery. We found that ABL significantly increased bone mineral content and improved trabecular structural parameters at the vertebral defect site. Moreover, ABL significantly increased bone strength of the defected vertebrae. Bone histochemical analysis revealed formation of thick trabecular bone networks at the defect site after ABL administration, consistent with an improvement in trabecular structural parameters by ABL. ABL increased ALPase- and PHOSPHO1-positive osteoblastic cells and ALPase/PCNA double-positive cells, indicating enhanced preosteoblast proliferation as well as bone formation at the defect site. On the other hand, ABL did not affect the number of cathepsin K-positive osteoclasts per bone surface, suggesting that ABL did not promote excessive bone resorption. Our findings suggest that ABL is useful not only for preventing secondary vertebral fractures but also for promoting bone healing in OVF.

Frequent administration of abaloparatide shows greater gains in bone anabolic window and bone mineral density in mice: A comparison with teriparatide.

Abaloparatide (ABL) is a novel 34-amino acid peptide analog of parathyroid hormone-related protein. In clinical studies, although ABL showed a greater bone mineral density (BMD) increase than teriparatide (TPTD, human parathyroid hormone 1-34), the responses of ABL to bone formation and resorption markers were weaker, making it difficult to understand the relationship between the bone anabolic window (increase in bone formation versus resorption) and bone mass. In the present study, the effects of ABL and TPTD were compared in mice. Given that the rate of bone turnover is higher in rodents than in humans, the comparison was made with several administration regimens providing equivalent daily dosages: once daily (QD, 30 µg/kg every 24 h), twice daily (BID, 15 µg/kg every 12 h), or three times a day (TID, 10 µg/kg every 8 h). Frequent administration of ABL showed higher BMD with enhancement of trabecular and cortical bone mass and structures than that of TPTD, consistent with the clinical results seen with once daily administration. ABL increased bone formation marker levels more than TPTD with more frequent regimens, while bone resorption marker levels were not different between ABL and TPTD in all regimens. Analysis of bone histomorphometry and gene expression also suggested that ABL increased bone formation more than TPTD, while the effect on bone resorption was almost comparable between ABL and TPTD. The bone anabolic windows calculated from bone turnover markers indicated that ABL enhanced the anabolic windows more than TPTD, leading to a robust increase in BMD. The mechanism by which ABL showed a better balance of bone turnover was suggested to be partly due to the enhanced remodeling-based bone formation involved in Ephb4. Taken together, our findings would help elucidate the mechanism by which ABL shows excellent BMD gain and reduction of fractures in patients with osteoporosis.

Abaloparatide Exerts Bone Anabolic Effects with Less Stimulation of Bone Resorption-Related Factors: A Comparison with Teriparatide.

Abaloparatide (ABL) is a novel synthetic peptide analog of parathyroid hormone-related protein. In previous reports, intermittent ABL administration showed robust bone mineral density (BMD) increase and reduced the incidence of fractures in patients with osteoporosis, while its calcemic effect was reduced, as compared with teriparatide (TPTD), a parathyroid hormone N-terminal fragment. The present study aimed to elucidate the effects of ABL on bone anabolism and bone turnover as compared with TPTD. In ovariectomized (OVX) rats, ABL increased the bone strength and BMD of lumbar spine by intermittent administration similar to TPTD. Both ABL and TPTD increased the bone formation marker serum P1NP with little effect on the bone resorption maker urine DPD/Cr, suggesting anabolic effects on bone. In human osteoblastic cells, both peptides increased the expression of bone resorption-related factors such as RANKL/OPG and M-CSF, and the effects of ABL were significantly attenuated as compared with those of TPTD under transient 6-h treatment, although no significant differences were found under continuous treatment. In contrast, ABL and TPTD similarly promoted the expression of bone formation-related factors, IGF-1 and osteocalcin. In addition, there were no significant differences in the effects on WNT signaling inhibitors such as sclerostin and dickkopf-related protein 1 (DKK1) between the two peptides. These results demonstrate that ABL exerts bone anabolic effects in OVX rats. It is also indicated that ABL stimulates the expression of RANKL/OPG and M-CSF less than TPTD, while showing similar effects on bone formation-related factors and WNT signaling inhibitors in vitro. The profile of ABL indicates that it would be a suitable bone anabolic agent for osteoporosis.

Pharmacological profiles of high-concentration (20 microg/g) tacalcitol ointment: effects on cutaneous inflammation, epidermal proliferation, and differentiation in mice.

This study focused on the effects of tacalcitol (1,24 (R) (OH)2D3, TV-02) ointment (20 micro g/g) on cutaneous inflammation, epidermal proliferation, and differentiation and compared them with tacalcitol ointment (2 micro g/g) and other anti-psoriatic ointments using hairless mice. Tacalcitol ointment (0, 2 and 20 micro g/g) significantly inhibited 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced cutaneous inflammation, histopathologically. The effect of tacalcitol ointment (20 micro g/g) on cutaneous inflammation was much stronger than that of tacalcitol ointment (0, 2 micro g/g), and as effective as calcipotriol ointment (50 micro g/g) or betamethasone valerate ointment (1.2 mg/g). Tacalcitol ointment (20 micro g/g) also significantly inhibited TPA-induced myeloperoxidase (MPO) activity, as effectively as calcipotriol ointment (50 micro g/g) or betamethasone valerate ointment (1.2 mg/g). The effect of tacalcitol ointment on epidermal proliferation [ornithine decarboxylase (ODC) activity] and differentiation [transglutaminase (TGase) activity] was dose-dependent from 0 micro g/g to 20 micro g/g. The effect of tacalcitol ointments on epidermal proliferation was significant at the doses of 2 micro g/g and 20 micro g/g, and that on epidermal differentiation was significant at the doses of 0.2 micro g/g or more. The effect of tacalcitol ointment (20 micro g/g) on epidermal differentiation was significantly stronger than tacalcitol ointment (2 micro g/g). In this study, tacalcitol ointment (20 micro g/g) was found to have a marked effect on cutaneous inflammation and improved effect on epidermal differentiation, although tacalcitol ointment (2 micro g/g) also had significant effects on epidermal proliferation and differentiation. These findings support the clinical effectiveness of tacalcitol ointment (20 micro g/g) against psoriasis.

Insulin receptor substrate-2 maintains predominance of anabolic function over catabolic function of osteoblasts.

Insulin receptor substrates (IRS-1 and IRS-2) are essential for intracellular signaling by insulin and insulin-like growth factor-I (IGF-I), anabolic regulators of bone metabolism. Although mice lacking the IRS-2 gene (IRS-2-/- mice) developed normally, they exhibited osteopenia with decreased bone formation and increased bone resorption. Cultured IRS-2-/- osteoblasts showed reduced differentiation and matrix synthesis compared with wild-type osteoblasts. However, they showed increased receptor activator of nuclear factor kappaB ligand (RANKL) expression and osteoclastogenesis in the coculture with bone marrow cells, which were restored by reintroduction of IRS-2 using an adenovirus vector. Although IRS-2 was expressed and phosphorylated by insulin and IGF-I in both osteoblasts and osteoclastic cells, cultures in the absence of osteoblasts revealed that intrinsic IRS-2 signaling in osteoclastic cells was not important for their differentiation, function, or survival. It is concluded that IRS-2 deficiency in osteoblasts causes osteopenia through impaired anabolic function and enhanced supporting ability of osteoclastogenesis. We propose that IRS-2 is needed to maintain the predominance of bone formation over bone resorption, whereas IRS-1 maintains bone turnover, as we previously reported; the integration of these two signalings causes a potent bone anabolic action by insulin and IGF-I.

Curative effect of combined treatment with alendronate and 1 alpha-hydroxyvitamin D3 on bone loss by ovariectomy in aged rats.

We investigated the combined effects of alendronate and 1alpha-hydroxyvitamin D3 (1alpha(OH)D3) on the bone mass and strength in aged ovariectomized rats and compared them with those of single treatments. Forty-week-old female rats underwent ovariectomy or sham operation, and after 15 weeks, ovariectomized rats were daily administered vehicle alone, alendronate (0.2 or 1.0 mg/kg,p.o.), 1alpha(OH)D3 (0.02 microg/kg, p.o.), or the combinations of 0.2 or 1.0 mg/kg of alendronate and 1alpha(OH)D3. After 12 weeks, the groups receiving combined treatments had significantly increased bone density and mechanical strength of the 4th lumbar vertebral body and the midfemur compared to the vehicle-treated group, and the effects were almost equal to or slightly less than the addition of those of the respective single treatments. The increase in mechanical strength was proportional to that in bone mineral density, suggesting that the stimulatory effects of these treatments on bone strength are ascribable primarily to those on bone mass. Analyses of histology, computed tomography, and biochemical markers confirmed the strong effect of the combined treatment on trabecular bone in particular, which was associated with increased trabecular number and decreased bone turnover. We propose that the combination of daily alendronate and 1alpha(OH)D3 is clinically promising as a curative treatment of established postmenopausal osteoporosis.