Manisha Dixit

Enhanced Immunoprotective Effects by Anti‐IL‐17 Antibody Translates to Improved Skeletal Parameters Under Estrogen Deficiency Compared With Anti‐RANKL and Anti‐TNF‐α Antibodies

Activated T cell has a key role in the interaction between bone and immune system. T cells produce proinflammatory cytokines, including receptor activator of NF‐κB ligand (RANKL), tumor necrosis factor α (TNF‐α), and interleukin 17 (IL‐17), all of which augment osteoclastogenesis. RANKL and TNF‐α are targeted by inhibitors such as denosumab, a human monoclonal RANKL antibody, and infliximab, which neutralizes TNF‐α. IL‐17 is also an important mediator of bone loss, and an antibody against IL‐17 is undergoing phase II clinical trial for rheumatoid arthritis. Although there are a few studies showing suppression of Th17 cell differentiation and induction of regulatory T cells (Tregs) by infliximab, the effect of denosumab remains poorly understood. In this study, we investigated the effects of anti‐TNF‐α, anti‐RANKL, or anti‐IL‐17 antibody administration to estrogen‐deficient mice on CD4+ T‐cell proliferation, CD28 loss, Th17/Treg balance and B lymphopoesis, and finally, the translation of these immunomodulatory effects on skeletal parameters. Adult Balb/c mice were treated with anti‐RANKL/‐TNF‐α/‐IL‐17 subcutaneously, twice a week, postovariectomy (Ovx) for 4 weeks. Animals were then autopsied; bone marrow cells were collected for FACS and RNA analysis and serum collected for ELISA. Bones were dissected for static and dynamic histomorphometry studies. We observed that although anti‐RANKL and anti‐TNF‐α therapies had no effect on Ovx‐induced CD4+ T‐cell proliferation and B lymphopoesis, anti‐IL‐17 effectively suppressed both events with concomitant reversal of CD28 loss. Anti‐IL‐17 antibody reduced proinflammatory cytokine production and induced Tregs. All three antibodies restored trabecular microarchitecture with comparable efficacy; however, cortical bone parameters, bone biomechanical properties, and histomorphometry were best preserved by anti‐IL‐17 antibody, likely attributable to its inhibitory effect on osteoblast apoptosis and increased number of bone lining cells and Wnt10b expression. Based on the superior immunoprotective effects of anti‐IL‐17, which appears to translate to a better skeletal preservation, we propose beginning clinical trials using a humanized antibody against IL‐17 for treatment of postmenopausal osteoporosis.

IL-18BP is decreased in osteoporotic women: Prevents Inflammasome mediated IL-18 activation and reduces Th17 differentiation

IL-18BP is a natural antagonist of pro-inflammatory IL-18 cytokine linked to autoimmune disorders like rheumatoid arthritis. However, its role in post menopausal osteoporosis is still unknown. In this study, we investigated the role of IL-18BP on murine osteoblasts, its effect on osteoblasts-CD4+ T cells and osteoblasts-CD11b+ macrophage co-culture. mIL-18BPd enhances osteoblast differentiation and inhibits the activation of NLRP3 inflammasome and caspase-1 which process IL-18 to its active form. Using estrogen deficient mice, we also determined the effect of mIL-18BP on various immune and skeletal parameters. Ovariectomized mice treated with mIL-18BPd exhibited decrease in Th17/Treg ratio and pro-inflammatory cytokines. mIL-18BPd treatment restored trabecular microarchitecture, preserved cortical bone parameters likely attributed to an increased number of bone lining cells and reduced osteoclastogenesis. Importantly, these results were corroborated in female osteoporotic subjects where decreased serum IL-18BP levels and enhanced serum IL-18 levels were observed. Our study forms a strong basis for using humanized IL-18BP towards the treatment of postmenopausal osteoporosis.

Medicarpin, a Natural Pterocarpan, Heals Cortical Bone Defect by Activation of Notch and Wnt Canonical Signaling Pathways.

We evaluated the bone regeneration and healing effect of Medicarpin (med) in cortical bone defect model that heals by intramembranous ossification. For the study, female Sprague–Dawley rats were ovariectomized and rendered osteopenic. A drill hole injury was generated in mid femoral bones of all the animals. Med treatment was commenced the day after and continued for 15 days. PTH was taken as a reference standard. Fifteen days post-treatment, animals were sacrificed. Bones were collected for histomorphometry studies at the injury site by micro-computed tomography (μCT) and confocal microscopy. RNA and protein was harvested from newly generated bone. For immunohistochemistry, 5μm sections of decalcified femur bone adjoining the drill hole site were cut. By μCT analysis and calcein labeling of newly generated bone it was found that med promotes bone healing and new bone formation at the injury site and was comparable to PTH in many aspects. Med treatment led to increase in the Runx-2 and osteocalcin signals indicating expansion of osteoprogenitors at the injury site as evaluated by qPCR and immunohistochemical localization. It was observed that med promoted bone regeneration by activating canonical Wnt and notch signaling pathway. This was evident by increased transcript and protein levels of Wnt and notch signaling components in the defect region. Finally, we confirmed that med treatment leads to elevated bone healing in pre-osteoblasts by co localization of beta catenin with osteoblast marker alkaline phosphatase. In conclusion, med treatment promotes new bone regeneration and healing at the injury site by activating Wnt/canonical and notch signaling pathways. This study also forms a strong case for evaluation of med in delayed union and non-union fracture cases.

Ethanolic extract of Coelogyne cristata Lindley (Orchidaceae) and its compound coelogin promote osteoprotective activity in ovariectomized estrogen deficient mice

Coelogyne cristata Lindley (CC) family Orchidaceae is an Indian medicinal plant used for the treatment of fractured bones in folk-tradition of Kumaon region, Uttarakhand, India. In continuation of our drug discovery program, feeding of ethanolic extract to ovariectomized estrogen deficient mice led to significant restoration of trabecular micro architecture in both femoral and tibial bones, better bone quality and also devoid of any uterine estrogenicity. Subsequently, coelogin, a pure compound was isolated from ethyl acetate fraction of C. cristata and evaluated in in vitro osteoblast cell cultures. Treatment of coelogin to osteoblasts led to enhanced ALP activity (a marker of osteoblast differentiation), mineral nodule formation and mRNA levels of osteogenic markers like BMP-2, Type 1 Collagen and RUNX-2. Based on these results, we propose that ethanolic extract of C. cristata and its pure compound coelogin have potential in the management of post menopausal osteoporosis.

Formononetin, a methoxy isoflavone, enhances bone regeneration in a mouse model of cortical bone defect.

The bone regeneration and healing effect of formononetin was evaluated in a cortical bone defect model that predominantly heals by intramembranous ossification. For this study, female Balb/c mice were ovariectomised (OVx) and a drill-hole injury was generated in the midfemoral bones of all animals. Treatment with formononetin commenced the day after and continued for 21 d. Parathyroid hormone (PTH1-34) was used as a reference standard. Animals were killed at days 10 and 21. Femur bones were collected at the injury site for histomorphometry studies using microcomputed tomography (μCT) and confocal microscopy. RNA and protein were harvested from the region surrounding the drill-hole injury. For immunohistochemistry, 5 µm sections of decalcified femur bone adjoining the drill-hole site were cut. μCT analysis showed that formononetin promoted bone healing at days 10 and 21 and the healing effect observed was significantly better than in Ovx mice and equal to PTH treatment in many aspects. Formononetin also significantly enhanced bone regeneration as assessed by calcein-labelling studies. In addition, formononetin enhanced the expression of osteogenic markers at the injury site in a manner similar to PTH. Formononetin treatment also led to predominant runt-related transcription factor 2 and osteocalcin localisation at the injury site. These results support the potential of formononetin to be a bone-healing agent and are suggestive of its promising role in the fracture-repair process.

Osteogenic activity of natural diterpenoids isolated from Cupressus sempervirens fruits in calvarial derived osteoblast cells via differentiation and mineralization

The aim of the present study was to investigate the antiosteoporotic activity of four structurally related diterpenoids: sugiol (1), trans-communic acid (2), 15-acetoxy imbricatolic acid (3) and imbricatolic acid (4). Their osteogenic effect was evaluated by using validated models including alkaline phosphatase (ALP) assay, mineralization assay and expression of osteogenic genes-bone morphogenetic protein-2 (BMP-2) and osteoblast transcription factor (RUNX2) - in primary calvarial cultures harvested from neonatal mice. Among them, compound 1 at a dose of 1.0 mg/kg body weight exhibited significant osteoprotective effects and did not show uterine estrogenicity at the same dose. Additionally, compound 1 treatment led to improved biomechanical properties as exhibited by increased power, energy and stiffness in femoral bones compared to untreated Ovx animals. Since osteoporotic compression fracture correlates with the mechanical characteristics of trabecular bone, so that it could effectively reduce the risk of this type of fracture by improving trabecular micro architecture in postmenopausal women. Therefore, our findings proposed that diterpenoids may be useful new chemical agents in the treatment of diseases associated with bone loss.

Potential osteogenic activity of ethanolic extract and oxoflavidin isolated from Pholidota articulata Lindley.

ETHNOPHARMACOLOGICAL RELEVANCE Pholidota articulata Lindley (PA) locally known as Hadjojen (bone jointer) belongs to family Orchidaceae is used for healing fractures in folklore tradition of Kumaon region of Uttarakhand, Himalaya, India. Bone is a dynamic organ and is constantly being remodeled in order to facilitate growth and repair. This process requires the involvement of bone forming osteoblast and bone resorbing osteoclast cells, which function in generating and mineralizing bone, giving strength and rigidity to the skeletal system. Present study was aimed to determine the therapeutic potential of ethanolic extract of PA and its isolated compound oxoflavidin, by characterizing their fracture healing properties. MATERIALS AND METHODS Ovariectomized (Ovx) estrogen deficient adult female Balb/c mice were used for in vivo evaluation of osteogenic or bone healing potential of ethanolic extract of PA. Further, its isolated compounds were tested for their osteogenic efficacy using alkaline phosphatase assay and mineralization assay in vitro in mice calvarial osteoblasts. RESULTS The ethanolic extract of PA exhibited significant restoration of trabecular micro-architecture in both femoral and tibial bones. Additionally, treatment with PA extract led to better bone quality and devoid of any uterine estrogenicity in ovariectomized estrogen deficient mice. One of the isolated compound, oxoflavidin enhanced ALP activity (a marker of osteoblast differentiation), mineral nodule formation and mRNA levels of osteogenic markers like BMP-2, Type 1 Collagen, RUNX-2 and osteocalcin. CONCLUSION These results warrant that ethanolic extract of PA and its pure compound oxoflavidin have fracture healing properties. The extract and oxoflavidin exhibit a strong threapeutical potential for the treatment and management of postmenopausal osteoporosis.