Aromatase deficiency in transplanted bone marrow cells improves vertebral trabecular bone quantity...

Aromatase deficiency in transplanted bone marrow cells improves vertebral trabecular bone quantity, connectivity, and mineralization and decreases cortical porosity in murine bone marrow transplant recipients

AUTHORS

Katie Rubitschung, Amber Sherwood, Rasesh Kapadia, Yin Xi, Asghar Hajibeigi, Katya B. Rubinow, Joseph E. Zerwekh, Orhan K. Öz

ABSTRACT

Estradiol is an important regulator of bone accumulation and maintenance. Circulating estrogens are primarily produced by the gonads. Aromatase, the enzyme responsible for the conversion of androgens to estrogen, is expressed by bone marrow cells (BMCs) of both hematopoietic and nonhematopoietic origin. While the significance of gonad-derived estradiol to bone health has been investigated, there is limited understanding regarding the relative contribution of BMC derived estrogens to bone metabolism. To elucidate the role of BMC derived estrogens in male bone, irradiated wild-type C57BL/6J mice received bone marrow cells transplanted from either WT (WT(WT)) or aromatase-deficient (WT(ArKO)) mice. MicroCT was acquired on lumbar vertebra to assess bone quantity and quality. WT(ArKO) animals had greater trabecular bone volume (BV/TV p = 0.002), with a higher trabecular number (p = 0.008), connectivity density (p = 0.017), and bone mineral content (p = 0.004). In cortical bone, WT(ArKO) animals exhibited smaller cortical pores and lower cortical porosity (p = 0.02). Static histomorphometry revealed fewer osteoclasts per bone surface (Oc.S/BS%), osteoclasts on the erosion surface (ES(Oc+)/BS, p = 0.04) and low number of osteoclasts per bone perimeter (N.Oc/B.Pm, p = 0.01) in WT(ArKO). Osteoblast-associated parameters in WT(ArKO) were lower but not statistically different from WT(WT). Dynamic histomorphometry suggested similar bone formation indices’ patterns with lower mean values in mineral apposition rate, label separation, and BFR/BS in WT(ArKO) animals. Ex vivo bone cell differentiation assays demonstrated relative decreased osteoblast differentiation and ability to form mineralized nodules. This study demonstrates a role of local 17β-estradiol production by BMCs for regulating the quantity and quality of bone in male mice. Underlying in vivo cellular and molecular mechanisms require further study.

Anemoside B4 attenuates RANKL-induced osteoclastogenesis by upregulating Nrf2 and dampens ovariectomy-induced bone loss

AUTHORS

Zhen Cao, Xuben Niu, Maihuan Wang, Siwang Yu, Mingkun Wang, Silong Mu, Chuan Liu, Yaxi Wang

ABSTRACT

Increased numbers and functional overactivity of osteoclasts are the pathological basis for bone loss diseases such as osteoporosis, which are characterized by cortical bone thinning, decreased trabecular bone quantity, and reduced bone mineral density. Effective inhibition of osteoclast formation and bone resorption are important means of treating such skeletal diseases. Anemoside B4 (AB4), the main active component of Pulsatilla chinensis, possesses a wide range of anti-inflammatory and immunoregulatory effects. However, its effect and mechanism in osteoclast differentiation remain unclear. In this study, we found through tartrate-resistant acidic phosphatase (TRAcP) staining and immunofluorescence staining that AB4 inhibited the differentiation, fusion, and bone-resorption functions of osteoclasts induced by receptor activator of nuclear factor κB ligand (RANKL) in vitro. Additionally, real time PCR (RT-qPCR) and western blot analysis showed AB4 downregulated the expression of osteoclast marker genes, including Nfatc1, Fos, and Ctsk, while upregulating Nrf2 expression. AB4 (5 mg/kg) alleviated bone loss in ovariectomized mice by inhibiting osteoclast formation. Furthermore, the knockout of Nrf2 weakened the inhibitory effects of AB4 on osteoclast formation and related gene expression. In summary, the results suggest AB4 can inhibit osteoclast differentiation and function by activating Nrf2 and indicate AB4 may be a candidate drug for osteoporosis.

Klotho regulates the myogenic response of muscle to mechanical loading and exercise

AUTHORS

Eisuke Ochi, Alice Barrington, Michelle Wehling-Henricks, Marcus Avila, Makoto Kuro-o, James G. Tidball

ABSTRACT

Muscle growth is influenced by changes in the mechanical environment that affect the expression of genes that regulate myogenesis. We tested whether the hormone Klotho could influence the response of muscle to mechanical loading. Applying mechanical loads to myoblasts in vitro increased RNA encoding transcription factors that are expressed in activated myoblasts (Myod) and in myogenic cells that have initiated terminal differentiation (Myog). However, application of Klotho to myoblasts prevented the loading-induced activation of Myog without affecting loading-induced activation of Myod. This indicates that elevated Klotho inhibits mechanically-induced differentiation of myogenic cells. Elevated Klotho also reduced the transcription of genes encoding proteins involved in the canonical Wnt pathway or their target genes (Wnt9a, Wnt10a, Ccnd1). Because the canonical Wnt pathway promotes differentiation of myogenic cells, these findings indicate that Klotho inhibits the differentiation of myogenic cells experiencing mechanical loading. We then tested whether these effects of Klotho occurred in muscles of mice experiencing high-intensity interval training (HIIT) by comparing wild-type mice and klotho transgenic mice. The expression of a klotho transgene combined with HIIT synergized to tremendously elevate numbers of Pax7+ satellite cells and activated MyoD+ cells. However, transgene expression prevented the increase in myogenin+ cells caused by HIIT in wild-type mice. Furthermore, transgene expression diminished the HIIT-induced activation of the canonical Wnt pathway in Pax7+ satellite cells. Collectively, these findings show that Klotho inhibits loading- or exercise-induced activation of muscle differentiation and indicate a new mechanism through which the responses of muscle to the mechanical environment are regulated.

Effect of fiber surface treatment on mechanical, interfacial, and moisture absorption properties of cattail fiber-reinforced composites

AUTHORS

Md Shadhin, Raghavan Jayaraman, Mashiur Rahman, Danny Mann

ABSTRACT

Surface treatment of cattail, a lignocellulosic renewable fiber, was investigated to determine the conditions that would reduce moisture absorption while maximizing the properties of cattail fiber-reinforced unsaturated polyester composites. Surface modification of cattail fiber was studied by treating them with 2.5, 5, and 10% of 1,6-diisocyanatohexane (DIH) and 2-hydroxyethyl acrylate (HEA) for three different immersion times (10, 20, and 30 min). DIH-HEA treated fibers were preformed into a non-woven mat and impregnated with unsaturated polyester resin to manufacture composite. The existence of covalent bonds on the treated fibers via NH and CN groups was confirmed by FTIR spectroscopy. The 10% DIH-HEA resulted in the best results; while the mean diameter of the treated fiber decreased by ~37%, the modulus and the strength of it increased by ~267 and ~151%, respectively. Equilibrium moisture regain of the treated fibers and their composites decreased by ~43% and ~40%, respectively. The tensile modulus of the composites increased by ~171%. Enhancement in tensile strength is observed but could not be quantified due to the difference in Vf and scatter in the data. SEM examination confirmed the enhancement in fiber–matrix bonding due to surface treatment.

FKBP5 drives bone marrow stem cells senescence and suppresses osteogenic differentiation via canonical WNT/β-catenin signaling pathway

AUTHORS

Bin Zhu, Bowen Cai, Kaixiao Xue, Guoyong Yin, Shumin Zhou, Jiahu Fang

ABSTRACT

Senile osteoporosis and associated fractures significantly increase the morbidity and mortality of older people, thus increasing the cost of public health. Further investigations are required to explore the molecular causes of senile osteoporosis. In this study, FKBP5 expression in bone marrow mesenchymal stem cells (BMSCs) increased with age, and the degree of expression was inversely related to the patient's bone mineral density or CT values. Functional studies have validated the regulatory function of FKBP5 in BMSCs osteogenesis differentiation through the canonical WNT/β-catenin signaling pathway by binding to β-catenin and promoting its ubiquitination and degradation. Administration of SAFit2, a selective inhibitor of FKBP5, enhanced bone density in an animal model of senile osteoporosis. These findings suggest that FKBP5 may be a novel target and offer a new perspective on osteoporosis treatment.

The synergistic treatment of cyclolinopeptide J and calcium carbonate nanoparticles for osteoporosis via BMP/Wnt signaling: In vivo and in vitro

AUTHORS

Jiazi Chen, Wen Li, Yee-Ying Lee, Zizhe Cai, Jing Chen, Yong Wang

ABSTRACT

This research focuses on the investigation of cyclolinopeptide J (CLJ), a bioactive peptide naturally present in flaxseed, which loaded in porous calcium carbonate (CA) nanoparticles (JCA) to augment the effectiveness of CLJ on osteogenesis. The JCA was successfully synthesized with a high loading capacity (47.8 %) and encapsulation efficiency (95.6 %). Results showed that CLJ exerted an excellent osteogenic effect at 10 µM in MC3T3-E1 cells. CLJ and CA have been shown to activate osteogenic factors by modulating the Wnt/β-catenin and BMP/Smad signaling pathways. Furthermore, JCA treatment exhibited a remarkable ability to restore the intricate trabecular characteristics of bone in OVX-induced mice. The trabecular bone architecture observed in JCA-treated mice closely resembled that of healthy controls, indicating a substantial amelioration of osteoporotic bone loss. Our findings highlight the synergistic treatment of CLJ and CA in restoring bone integrity and structure and provide compelling evidence for the effectiveness of this novel functional supplement.