Management of difficult osteoporosis

Nanosurface Texturing for Enhancing the Antibacterial Effect of Biodegradable Metal Zinc: Surface Modifications

Zinc (Zn) as a biodegradable metal has attracted research interest for bone reconstruction, with the aim of eliminating the need for a second removal surgery and minimizing the implant-to-bone transfer of stress-shielding to maintain bone regeneration. In addition, Zn has been shown to have antibacterial properties, particularly against Gram-negative bacteria, and is often used as a surface coating to inhibit bacterial growth and biofilm formation. However, the antibacterial property of Zn is still suboptimal in part due to low Zn ion release during degradation that has to be further improved in order to meet clinical requirements. This work aims to perform an innovative one-step surface modification using a nitric acid treatment to accelerate Zn ion release by increasing surface roughness, thereby endowing an effective antimicrobial property and biofilm formation inhibition. The antibacterial performance against Staphylococci aureus was evaluated by assessing biofilm formation and adhesion using quantitative assays. The surface roughness of acid-treated Zn (Ra ~ 30 nm) was significantly higher than polished Zn (Ra ~ 3 nm) and corresponded with the marked inhibition of bacterial biofilm, and this is likely due to the increased surface contact area and Zn ion accumulation. Overall, surface modification due to nitric acid etching appears to be an effective technique that can produce unique morphological surface structures and enhance the antibacterial properties of biodegradable Zn-based materials, thus increasing the translation potential toward multiple biomedical applications.

NMP4, an Arbiter of Bone Cell Secretory Capacity and Regulator of Skeletal Response to PTH Therapy

The skeleton is a secretory organ, and the goal of some osteoporosis therapies is to maximize bone matrix output. Nmp4 encodes a novel transcription factor that regulates bone cell secretion as part of its functional repertoire. Loss of Nmp4 enhances bone response to osteoanabolic therapy, in part, by increasing the production and delivery of bone matrix. Nmp4 shares traits with scaling factors, which are transcription factors that influence the expression of hundreds of genes to govern proteome allocation for establishing secretory cell infrastructure and capacity. Nmp4 is expressed in all tissues and while global loss of this gene leads to no overt baseline phenotype, deletion of Nmp4 has broad tissue effects in mice challenged with certain stressors. In addition to an enhanced response to osteoporosis therapies, Nmp4-deficient mice are less sensitive to high fat diet-induced weight gain and insulin resistance, exhibit a reduced disease severity in response to influenza A virus (IAV) infection, and resist the development of some forms of rheumatoid arthritis. In this review, we present the current understanding of the mechanisms underlying Nmp4 regulation of the skeletal response to osteoanabolics, and we discuss how this unique gene contributes to the diverse phenotypes among different tissues and stresses. An emerging theme is that Nmp4 is important for the infrastructure and capacity of secretory cells that are critical for health and disease.

Conditional Loss of Nmp4 in Mesenchymal Stem Progenitor Cells Enhances PTH-Induced Bone Formation

Activation of bone anabolic pathways is a fruitful approach for treating severe osteoporosis, yet FDA-approved osteoanabolics, eg, parathyroid hormone (PTH), have limited efficacy. Improving their potency is a promising strategy for maximizing bone anabolic output. Nmp4 (Nuclear Matrix Protein 4) global knockout mice exhibit enhanced PTH-induced increases in trabecular bone but display no overt baseline skeletal phenotype. Nmp4 is expressed in all tissues; therefore, to determine which cell type is responsible for driving the beneficial effects of Nmp4 inhibition, we conditionally removed this gene from cells at distinct stages of osteogenic differentiation. Nmp4-floxed (Nmp4fl/fl ) mice were crossed with mice bearing one of three Cre drivers including (i) Prx1Cre+  to remove Nmp4 from mesenchymal stem/progenitor cells (MSPCs) in long bones; (ii) BglapCre+  targeting mature osteoblasts, and (iii) Dmp1Cre+  to disable Nmp4 in osteocytes. Virgin female Cre+  and Cre- mice (10 weeks of age) were sorted into cohorts by weight and genotype. Mice were administered daily injections of either human PTH 1-34 at 30 μg/kg or vehicle for 4 weeks or 7 weeks. Skeletal response was assessed using dual-energy X-ray absorptiometry, micro-computed tomography, bone histomorphometry, and serum analysis for remodeling markers. Nmp4fl/fl ;Prx1Cre+  mice virtually phenocopied the global Nmp4-/- skeleton in the femur, ie, a mild baseline phenotype but significantly enhanced PTH-induced increase in femur trabecular bone volume/total volume (BV/TV) compared with their Nmp4fl/fl ;Prx1Cre- controls. This was not observed in the spine, where Prrx1 is not expressed. Heightened response to PTH was coincident with enhanced bone formation. Conditional loss of Nmp4 from the mature osteoblasts (Nmp4fl/fl ;BglapCre+ ) failed to increase BV/TV or enhance PTH response. However, conditional disabling of Nmp4 in osteocytes (Nmp4fl/fl ;Dmp1Cre+ ) increased BV/TV without boosting response to hormone under our experimental regimen. We conclude that Nmp4-/- Prx1-expressing MSPCs drive the improved response to PTH therapy and that this gene has stage-specific effects on osteoanabolism. © 2022 American Society for Bone and Mineral Research (ASBMR).

Identification of osteoporosis based on gene biomarkers using support vector machine

Osteoporosis is a major health concern worldwide. The present study aimed to identify effective biomarkers for osteoporosis detection. In osteoporosis, 559 differentially expressed genes (DEGs) were enriched in PI3K-Akt signaling pathway and Foxo signaling pathway. Weighted gene co-expression network analysis showed that green, pink, and tan modules were clinically significant modules, and that six genes (VEGFA, DDX5, SOD2, HNRNPD, EIF5B, and HSP90B1) were identified as “real” hub genes in the protein–protein interaction network, co-expression network, and 559 DEGs. The sensitivity and specificity of the support vector machine (SVM) for identifying patients with osteoporosis was 100%, with an area under curve of 1 in both training and validation datasets. Our results indicated that the current system using the SVM method could identify patients with osteoporosis.

LOXG473A induces the formation of osteoclasts in RAW264.7 cells via IL-6/JAK2/STAT3 signaling

Formation of osteoclasts is known to be closely associated with osteoporosis progression. LOX is a key enzyme that catalyzes the synthesis of collagen, which is the new mediator in osteoclast formation. However, the effect of LOXG473A on of osteoclast formation needs to be explored. Thereby, we sought to explore the effect of LOX_G473A on formation of osteoclasts and its underlying mechanism. To investigate the function of LOX_G473A in osteoclast formation, Raw264.7 cells were stably transfected with LOX-WT or LOX-MUT (LOX_G473A). Real-time PCR and western blotting were used to detect the relative levels of osteoclast formation related genes and proteins. TRAP staining and immunofluorescence staining were used to test the ability of Raw264.7 cells to form osteoclasts and the ability of cells to form rings, respectively. Bone erosion assay was used to test bone resorptive activity. The data indicated that LOX_G473A significantly enhanced the ability of osteoclasts forming, ring-forming and bone resorpting in Raw264.7 cells. Mechanically, LOX_G473A upregulated the expressions of NFATC1, ACP5, CTSK, IL-6, and the proportion of p-JAK2/JAK2 and p-STAT3/STAT3, thereby promoting the formation of osteoclasts. In conclusion, we have verified that LOX_G473A induces the proliferation of osteoclasts in Raw264.7 cells via IL-6/JAK2/STAT3 signaling, suggesting a novel strategy for studying osteoporosis.

Zn0.8Li0.1Sr-a biodegradable metal with high mechanical strength comparable to pure Ti for the treatment of osteoporotic bone fractures: In vitro and in vivo studies

The first in vivo investigation of Zn-based biodegradable metal aiming to treat osteoporotic bone fractures, a soaring threat to human health, is reported in this paper. Among the newly developed biodegradable metal system (ZnLiSr), Zn0.8Li0.1Sr exhibits excellent comprehensive mechanical properties, with an ultimate tensile strength (524.33 ± 18.01 MPa) comparable to pure Ti (the gold standard for orthopaedic implants), and a strength-ductility balance over 10 GPa%. The in vitro degradation tests using simulated body fluid (SBF) shows that Zn0.8Li0.1Sr manifests a uniform degradation morphology and smaller corrosion pits, with a degradation rate of 10.13 ± 1.52 μm year^-1. Real-time PCR and western blotting illustrated that Zn0.8Li0.1Sr successfully stimulated the expression of critical osteogenesis-related genes (ALP, COL-1, OCN and Runx-2) and proteins. Twenty-four weeks' in vivo implantations within ovariectomized (OVX) rats were conducted to evaluate the osteoporotic-bone-fracture-treating effects of Zn0.8Li0.1Sr, with pure Ti as control group. Micro-CT, histological and immunohistochemical evaluations all revealed that Zn0.8Li0.1Sr possesses a similar biosafety level to, while significantly superior osteogenesis-inducing and osteoporotic-bone-fracture-treating effects than pure Ti. ZnLiSr biodegradable alloys manifest excellent comprehensive mechanical properties, good biosafety and osteoporotic-bone-fracture-treating effects, which would provide preferable choices for future medical applications, especially in load-bearing positions.

Tyloxapol inhibits RANKL-stimulated osteoclastogenesis and ovariectomized-induced bone loss by restraining NF-κB and MAPK activation

Objective

Tyloxapol is a non-ionic surfactant with diverse pharmacological effects including anti-inflammatory, anti-malignant tumor and antioxidant activities. However, the effect of tyloxapol on osteoclastogenesis has not been elucidated. In this study, we intended to clarify the effect of tyloxapol on RANKL-stimulated osteoclastogenesis and the molecular mechanism both ex vivo and in vivo.

Methods

In vitro osteoclastogenesis assay was performed in BMMs and Raw 264.7 cells. The mature osteoclasts were visualized by TRAP staining. The osteoblsats were visualized by alkaline phosphatase (ALP) staining and Von Kossa staining. To assess whether tyloxapol inhibited the function of mature osteoclasts, F-actin belts and pit formation assays were carried out in BMMs. To evaluate the effect of tyloxapol on post-menopausal osteoporosis, the OVX mouse model were utilized. The bone tissue TRAP staining was used to evaluate the osteoclast activity in vivo. The von kossa staining and micro computed tomography were used to evaluate the histomorphometric parameters. The Goldner's staining was used to evaluate the osteoblast activity. The expression of osteoclastogenesis-associated markers were evaluated by Real-time PCR. The NF-κB and NFATc1 transcriptional activities were illustrated utilizing the assay of luciferase reporter. The effect of tyloxapol pretreatment on IκBa degradation and p65 phosphorylation was evaluated using Western bloting assay. The effect of tyloxapol pretreatment on p65 nuclear translocation was evaluated utilizing immunofluorescence. The effect of tyloxapol pretreatment on the phosphorylatio of ERK, p38 and JNK was examined utilizing Western bloting assay.

Results

In our research, we found that tyloxapol suppresses RANKL-stimulated osteoclastogenesis in a dose dependent manner and in the initial stage of osteoclastogenesis. Through F-actin belts and pit formation assays, we found that tyloxapol had the ability to inhibit the function of mature osteoclasts in vitro. The results of animal experiments demonstrated that tyloxapol inhibits OVX-induced bone mass loss by inhibiting the activity of osteoclasts but had a limited effect on osteoblastic differentiation and mineralization. Molecularly, we found that tyloxapol suppresses RANKL-stimulated NF-κB activation through suppressing degradation of IκBα, phosphorylation and nuclear translocation of p65. At last, MAPK signaling pathway was also suppressed by tyloxapol in dose and time-dependent manners.

Conclusion

Our research illustrated that tyloxapol was able to suppress osteoclastogenesis in vitro and ovariectomized-induced bone loss in vivo by restraining NF-κB and MAPK activation. This is pioneer research could pave the way for the development of tyloxapol as a potential therapeutic treatment for osteoporosis.

The translational potential of this article

This study explores that tyloxapol, also known as Triton WR-1339, may be a drug candidate for osteoclastogenic sicknesses like osteoporosis. Our study may also extend the clinical therapeutic spectrum of tyloxapol.

Biovalorization of soybean residue (okara) via fermentation with Ganoderma lucidum and Lentinus edodes to attain products with high anti-osteoporotic effects

Okara, despite being a soybean processing by-product, still holds many nutrients. Thus, considerable attention has been recently paid to its reuse. In this study, solid-state fermentation was performed using Ganoderma lucidum and Lentinus edodes. Antioxidant activity and bioactive compound levels in G. lucidum-fermented okara (GLFO) and L. edodes-fermented okara (LEFO) were assayed. Antiosteoporosis bioactivity was evaluated using an animal model. The results demonstrated that solid-state fermentation significantly improved the antioxidant activity and bioactive compound levels. Furthermore, GLFO and LEFO increased trabecular bone volume, although only the GLFO-treated group exhibited significantly improved trabecular separation compared with the bilateral ovariectomy-treated control group. GLFO-related outcomes were superior to those of LEFO. The results demonstrate that okara products are effective for treating postmenopausal osteoporosis in humans.

The Antiosteoporosis Effects of Yishen Bugu Ye Based on Its Regulation on the Differentiation of Osteoblast and Osteoclast

Yishen Bugu Ye (YSBGY), a traditional Chinese medicine comprising 12 types of medicinal herbs, is often prescribed in China to increase bone strength. In this study, the antiosteoporotic effects of YSBGY were investigated in C57BL/6 mice afflicted with dexamethasone- (Dex-) induced osteoporosis (OP). The results showed that YSBGY reduced the interstitial edema in the liver and kidney of mice with Dex-induced OP. It also increased the number of trabecular bone elements and chondrocytes in the femur, promoted cortical bone thickness and trabecular bone density, and modulated the OP-related indexes in the femur and tibia of OP mice. It also increased the serum concentrations of type I collagen, osteocalcin, osteopontin, bone morphogenetic protein-2, bone morphogenetic protein receptor type 2, C-terminal telopeptide of type I collagen, and runt-related transcription factor-2 and reduced those of tartrate-resistant acid phosphatase 5 and nuclear factor of activated T cells in these mice, suggesting that it improved osteoblast differentiation and suppressed osteoclast differentiation. The anti-inflammatory effect of YSBGY was confirmed by the increase in the serum concentrations of interleukin- (IL-) 33 and the decrease in concentrations of IL-1, IL-7, and tumor necrosis factor-α in OP mice. Furthermore, YSBGY enhanced the serum concentrations of superoxide dismutase and catalase in these mice, indicating that it also exerted antioxidative effects. This is the first study to confirm the antiosteoporotic effects of YSBGY in mice with Dex-induced OP, and it showed that these effects may be related to the YSBGY-induced modulation of the osteoblast/osteoclast balance and serum concentrations of inflammatory factors. These results provide experimental evidence supporting the use of YSBGY for supporting bone formation in the clinical setting.