Deletion of Glut1 in early postnatal cartilage reprograms chondrocytes toward enhanced glutamine oxidation

AUTHORS

Cuicui Wang, Jun Ying, Xiangfeng Niu, Xiaofei Li, Gary J. Patti, Jie Shen & Regis J. O’Keefe

ABSTRACT

Glucose metabolism is fundamental for the functions of all tissues, including cartilage. Despite the emerging evidence related to glucose metabolism in the regulation of prenatal cartilage development, little is known about the role of glucose metabolism and its biochemical basis in postnatal cartilage growth and homeostasis. We show here that genetic deletion of the glucose transporter Glut1 in postnatal cartilage impairs cell proliferation and matrix production in growth plate (GPs) but paradoxically increases cartilage remnants in the metaphysis, resulting in shortening of long bones. On the other hand, articular cartilage (AC) with Glut1 deficiency presents diminished cellularity and loss of proteoglycans, which ultimately progress to cartilage fibrosis. Moreover, predisposition to Glut1 deficiency severely exacerbates injury-induced osteoarthritis. Regardless of the disparities in glucose metabolism between GP and AC chondrocytes under normal conditions, both types of chondrocytes demonstrate metabolic plasticity to enhance glutamine utilization and oxidation in the absence of glucose availability. However, uncontrolled glutamine flux causes collagen overmodification, thus affecting extracellular matrix remodeling in both cartilage compartments. These results uncover the pivotal and distinct roles of Glut1-mediated glucose metabolism in two of the postnatal cartilage compartments and link some cartilage abnormalities to altered glucose/glutamine metabolism.

Morin attenuates osteoclast formation and function by suppressing the NF-κB, MAPK and calcium signalling pathways

AUTHORS

Yifeng Shi, Lin Ye, Shiwei Shen, Tianchen Qian, Youjin Pan, Yuhan Jiang, Jinghao Lin, Chen Liu, Yaosen Wu, Xiangyang Wang, Jiake Xu, Haiming Jin

ABSTRACT

Morin is a natural compound isolated from moraceae family members and has been reported to possess a range of pharmacological activities. However, the effects of morin on bone-associated disorders and the potential mechanism remain unknown. In this study, we investigated the anti-osteoclastogenic effect of morin in vitro and the potential therapeutic effects on ovariectomy (OVX)-induced osteoporosis in vivo. In vitro, by using a bone marrow macrophage-derived osteoclast culture system, we determined that morin attenuated receptor activator of nuclear factor (NF)-κB ligand (RANKL)-induced osteoclast formation via the inhibition of the mitogen-activated protein kinase (MAPK), NF-κB and calcium pathways. In addition, the subsequent expression of nuclear factor of activated T cells c1 (NFATc1) and c-fos was significantly suppressed by morin. In addition, NFATc1 downregulation led to the reduced expression of osteoclastogenesis-related marker genes, such as V-ATPase-d2 and Integrin β3. In vivo, results provided that morin could effectively attenuate OVX-induced bone loss in C57BL/6 mice. In conclusion, our results demonstrated that morin suppressed RANKL-induced osteoclastogenesis via the NF-κB, MAPK and calcium pathways, in addition, its function of preventing OVX-induced bone loss in vivo, which suggested that morin may be a potential therapeutic agent for postmenopausal osteoporosis treatment.

Gli1+ progenitors mediate bone anabolic function of teriparatide via Hh and Igf signaling

AUTHORS

Yu Shi, Xueyang Liao, James Y.Long, Lutian Yao, Jianquan Chen, Bei Yin, Feng Lou, Guangxu He, Ling Ye, Ling Qin, Fanxin Long

ABSTRACT

Teriparatide is the most widely prescribed bone anabolic drug in the world, but its cellular targets remain incompletely defined. The Gli1+ metaphyseal mesenchymal progenitors (MMPs) are a main source for osteoblasts in postnatal growing mice, but their potential response to teriparatide is unknown. Here, by lineage tracing, we show that teriparatide stimulates both proliferation and osteoblast differentiation of MMPs. Single-cell RNA sequencing reveals heterogeneity among MMPs, including an unexpected chondrocyte-like osteoprogenitor (COP). COP expresses the highest level of Hedgehog (Hh) target genes and the insulin-like growth factor 1 receptor (Igf1r) among all cell clusters. COP also expresses Pth1r and further upregulates Igf1r upon teriparatide treatment. Inhibition of Hh signaling or deletion of Igf1r from MMPs diminishes the proliferative and osteogenic effects of teriparatide. The study therefore identifies COP as a teriparatide target wherein Hh and insulin-like growth factor (Igf) signaling are critical for the osteoanabolic response in growing mice.

New Shunosaurus (Dinosauria: Sauropoda) material from the middle Jurassic lower Shaximiao Formation of Yunyang, Chongqing, China

AUTHORS

Qingyu Ma, Hui Dai,Chao Tan, Ning Li, Ping Wang, Xinxin Ren, Li Meng, Qi Zhao, Guangbiao Wei & Xing Xu

ABSTRACT

Shunosaurus is a small eusauropod from China. It is characterised by solid cervical and dorsal vertebral centra without complicated pneumatic structures, platycoelous or amphicoelous middle and posterior vertebrae and a lack of pubic foramen in adult individuals. Although many Shunosaurus individuals have been discovered, the ontogenetic characteristics of its long bones and bone tissues are not very clear and the existing description of the postcranial skeleton is relatively rudimentary. The new well-preserved and the smallest Shunosaurus specimen discovered in Yunyang, Chongqing, China, provides good material for solving these problems. The radial distal breadth is more than twice the minimum midshaft breadth, and the fibular distal end is twice as wide as the midshaft, while these ratios are all smaller in adult specimens. The lateral trochanter is undeveloped. This individual does show a pubic foramen. The degree of vascularisation of the bone tissue in the juvenile bone tissue is higher for adults. There are no arrested growth lines and peripheral rest lines in the compact bone, indicating that body size still increases slowly after maturity. The discovery of this new material expands the distribution range of Shunosaurus in China.

Injectable sericin based nanocomposite hydrogel for multi-modal imaging-guided immunomodulatory bone regeneration

AUTHORS

Li-Bo Jiang, Sheng-Long Ding, Wang Ding, Di-Han Su, Fang-Xue Zhang, Tai-Wei Zhang, Xiao-Fan Yin, Lan Xiao, Yu-Lin Li, Feng-Lai Yuan, Jian Dong

ABSTRACT

Irregular bone defects, where the inflammation and immune microenvironment confronted with implanted biomaterials, remain a prominent challenge for bone regeneration. In this study, we fabricated an injectable alginate/sericin/graphene oxide (Alg/Ser/GO) hydrogel based on the Alg–Tyramine framework with HRP/H2O2 enzymatic crosslinking. This hydrogel exhibited bioimaging property and controlled degradation behavior upon releasing sericin and GO. Importantly, synergistic effects on bone regeneration between sericin and GO were demonstrated. GO significantly enhanced the spreading, osteogenic differentiation, and mineralization of encapsulated rat BMSCs, whereas the released sericin promoted M2 polarization and migration via the NF-κB and MAPK pathways. The M2 polarization of macrophages induced osteogenic differentiation of BMSCs via several secreted cytokines. Both in vivo and in vitro experiments showed that the Alg/Ser/GO hydrogel induced macrophage infiltration into the surrounding tissues and inhibited inflammation and fibrous capsule thickening. Last, the injected Alg/Ser/GO hydrogels with BMSCs promptly repaired established distal femoral defects in rats. Therefore, the fabricated Alg/Ser/GO hydrogel, along with macrophages and BMSCs, is a promising biomaterial for bone healing, especially the irregular bone defects.

Development of bioinks for 3D printing microporous, sintered calcium phosphate scaffolds

AUTHORS

Sergio A. Montelongo, Gennifer Chiou, Joo L. Ong, Rena Bizios & Teja Guda

ABSTRACT

Beta-tricalcium phosphate (β-TCP)-based bioinks were developed to support direct-ink 3D printing-based manufacturing of macroporous scaffolds. Binding of the gelatin:β-TCP ink compositions was optimized by adding carboxymethylcellulose (CMC) to maximize the β-TCP content while maintaining printability. Post-sintering, the gelatin:β-TCP:CMC inks resulted in uniform grain size, uniform shrinkage of the printed structure, and included microporosity within the ceramic. The mechanical properties of the inks improved with increasing β-TCP content. The gelatin:β-TCP:CMC ink (25:75 gelatin:β-TCP and 3% CMC) optimized for mechanical strength was used to 3D print several architectures of macroporous scaffolds by varying the print nozzle tip diameter and pore spacing during the 3D printing process (compressive strength of 13.1 ± 2.51 MPa and elastic modulus of 696 ± 108 MPa was achieved). The sintered, macroporous β-TCP scaffolds demonstrated both high porosity and pore size but retained mechanical strength and stiffness compared to macroporous, calcium phosphate ceramic scaffolds manufactured using alternative methods. The high interconnected porosity (45–60%) and fluid conductance (between 1.04 ×10−9 and 2.27 × 10−9 m4s/kg) of the β-TCP scaffolds tested, and the ability to finely tune the architecture using 3D printing, resulted in the development of novel bioink formulations and made available a versatile manufacturing process with broad applicability in producing substrates suitable for biomedical applications.