Bone biology
Abstract
Transient receptor potential channel 1 (TRPC1) is a widely expressed mechanosensitive ion channel located within the endoplasmic reticulum membrane, crucial for refilling depleted internal calcium stores during activation of calcium-dependent signaling pathways. Here, we demonstrate that TRPC1 activity is protective within cartilage homeostasis in the prevention of cellular senescence associated cartilage breakdown during mechanical and inflammatory challenge. We reveal that TRPC1 loss is associated with early stages of osteoarthritis (OA) and plays a non-redundant role in calcium signaling in chondrocytes. Trpc1-/- mice subjected to destabilization of the medial meniscus induced OA developed a more severe OA phenotype than wild type controls. During early OA development, Trpc1-/- mice displayed an increased chondrocyte survival rate, however remaining cells displayed features of senescence including p16INK4a expression and decreased Sox9. RNA sequencing identified differentially expressed genes related to cell number, apoptosis and extracellular matrix organization. Trpc1-/-chondrocytes exhibited accelerated dedifferentiation, while demonstrating an increased susceptibility to cellular senescence. Targeting the mechanism of Trpc1 activation may be a promising therapeutic strategy in osteoarthritis prevention.
Authors
Meike Sambale, Starlee Lively, Osvaldo Espin-Garcia, Pratibha Potla, Chiara Pastrello, Sarah Bödecker, Linda Wessendorf, Simon Kleimann, Peter Paruzel, Rojiar Asgarian, Alexandra Tosun, Johanna Intemann, Jessica Bertrand, Francesco Dell'Accio, Mohit Kapoor, Thomas Pap, Joanna Sherwood
Abstract
Regeneration of orofacial bone defects caused by inflammatory-related diseases or trauma remains an unmet challenge. Parathyroid hormone 1 receptor (PTH1R) signaling is a key mediator of bone remodeling whereas the regulatory mechanisms of PTH1R signaling in oral bone under homeostatic or inflammatory conditions have not been demonstrated by direct genetic evidence. Here we observed that deletion of PTH1R in Gli1+-progenitors led to increased osteogenesis and osteoclastogenesis. Single-cell and bulk RNA-seq analysis revealed that PTH1R suppresses the osteogenic potential of Gli1+-progenitors during inflammation. Moreover, we identified upregulated IGF1 expression upon PTH1R deletion. Dual deletion of IGF1 and PTH1R ameliorated the bone remodeling phenotypes in PTH1R-defienct mice. Furthermore, in vivo evidence revealed an inverse relationship between PTH1R and Hedgehog signaling, which was responsible for the upregulated IGF1 production. Our work underscored the negative feedback between PTH1R and IGF1 in craniofacial bone turnover, and revealed mechanisms modulating orofacial bone remodeling.
Authors
Yi Fan, Ping Lyu, Jiahe Wang, Yali Wei, Zucen Li, Shiwen Zhang, Takehito Ouchi, Junjun Jing, Quan Yuan, Clifford J. Rosen, Chenchen Zhou
Abstract
Glucocorticoid-induced osteoporosis (GIOP) lacks fully effective treatments. This study investigated the role of Piezo1, a mechanosensitive ion channel component 1, in GIOP. We found reduced Piezo1 expression in cortical bone osteocytes from patients with GIOP and a GIOP mouse model. Yoda1, a Piezo1 agonist, enhanced the mechanical stress response and bone mass and strength, which were diminished by dexamethasone (DEX) administration in GIOP mice. RNA-seq revealed that Yoda1 elevated Piezo1 expression by activating the key transcription factor Hes1, followed by enhanced CaM kinase II and Akt phosphorylation in osteocytes. This improved the lacuno-canalicular network and reduced sclerostin production and the receptor activator of NF-κB/osteoprotegerin ratio, which were mitigated by DEX. Comparative analysis of mouse models and human GIOP cortical bone revealed downregulation of mechanostimulated osteogenic factors, such as osteocrin, and cartilage differentiation markers in osteoprogenitor cells. In human periosteum-derived cells, DEX suppressed differentiation into osteoblasts, but Yoda1 rescued this effect. Our findings suggest that reduced Piezo1 expression and activity in osteocytes and periosteal cells contribute to GIOP, and Yoda1 may offer a novel therapeutic approach by restoring mechanosensitivity.
Authors
Nagahiro Ochiai, Yuki Etani, Takaaki Noguchi, Taihei Miura, Takuya Kurihara, Yuji Fukuda, Hidetoshi Hamada, Keisuke Uemura, Kazuma Takashima, Masashi Tamaki, Teruya Ishibashi, Shohei Ito, Satoshi Yamakawa, Takashi Kanamoto, Seiji Okada, Ken Nakata, Kosuke Ebina
Abstract
Mechanical loading, essential for bone health, promotes bone formation and remodeling. However, the positive response diminishes in cases of disuse and aging, leading to bone loss and an increased fracture risk. This study demonstrates that activating hemichannels (HCs) using a connexin 43 (Cx43) antibody, Cx43(M2), in bone osteocytes revitalizes aging and disused bones. Using a hindlimb suspension (HLS) disuse model and a tibial mechanical loading model, we found that Cx43(M2) inhibited bone loss and osteocyte apoptosis induced by unloading in 16-week-old adult mice. Additionally, it enhanced bone mass in response to tibial loading in 22-month-old aged mice. The HC opening released bone anabolic factor prostaglandin E2 (PGE2) and suppressed catabolic factor sclerostin (SOST). This suppressed the increase of cortical bone formation and reduction of bone resorption during unloading and promoted trabecular and cortical bone formation during loading. Cx43(M2)-induced HC opening, coupled with PGE2 release, effectively rescued unloading-induced bone loss and restored the diminished anabolic response of aged bones to mechanical loading. Activating HCs with the Cx43 antibody holds promise as a de novo therapeutic approach, as it can overcome the limitations of existing treatment regimens for treating bone loss and osteoporosis associated with aging and disuse.
Authors
Dezhi Zhao, Chao Tu, Lidan Zhang, Teja Guda, Sumin Gu, Jean X. Jiang
Abstract
Soft tissue trauma can cause immune system disturbance and neuropathological invasion, resulting in heterotopic ossification (HO) due to aberrant chondrogenic differentiation of mesenchymal stem cells (MSCs). However, the molecular mechanisms behind the interaction between the immune and nervous systems in promoting HO pathogenesis are unclear. In this study, we found that mast cell-specific deletion attenuated localized tissue inflammation, with marked inhibition of HO endochondral osteogenesis. Likewise, blockage of nerve growth factor (NGF) receptor, known as tropomyosin receptor kinase A (TrkA), led to similar attenuations in tissue inflammation and HO. Moreover, while NGF-TrkA signaling did not directly affect MSCs chondrogenic differentiation, it modulated mast cell activation in traumatic soft tissue. Mechanistically, lipid A in lipopolysaccharide binding to TrkA enhanced NGF-induced TrkA phosphorylation, synergistically stimulating mast cells to release neurotrophin-3 (NT3), thereby promoting MSCs chondrogenic differentiation in situ. Finally, analysis of single-cell datasets and human pathological specimens confirmed the important role of mast cell-mediated neuroinflammation in HO pathogenesis. In conclusion, NGF regulates mast cells in soft tissue trauma, and drives HO progression via paracrine NT3. Targeted early inhibition of mast cells holds substantial promise for treating traumatic HO.
Authors
Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang
Abstract
Osteoclasts are the sole bone-resorbing cells and are formed by the fusion of osteoclast precursor cells (OCPs) derived from myeloid lineage cells. Animal studies reveal that circulating OCPs (cOCPs) in blood travel to bone and fuse with bone-resident osteoclasts. However, the characteristics of human cOCPs and their association with bone diseases remain elusive. We have identified and characterized human cOCPs and found a positive association between cOCPs and osteoclast activity. Sorted cOCPs have a higher osteoclastogenic potential than other myeloid cells and effectively differentiate into osteoclasts. cOCPs exhibit distinct morphology and transcriptomic signatures. The frequency of cOCPs in the blood varies among treatment-naive postmenopausal women and has an inverse correlation with lumbar spine bone density and a positive correlation with serum CTX, a bone resorption marker. The increased cOCPs in treatment-naive patients with osteoporosis were significantly diminished by denosumab, a widely used antiresorptive therapy. Our study reveals the distinctive identity of human cOCPs and the potential link between the dynamic regulation of cOCPs and osteoporosis and its treatment. Taken together, our study enhances our understanding of human cOCPs and highlights a potential opportunity to measure cOCPs through a simple blood test, which could potentially identify high-risk individuals.
Authors
Kaichi Kaneko, Jefferson Tsai, Deniece Meñez, Brian Oh, Andrew Junwoo Suh, Seyeon Bae, Masataka Mizuno, Akio Umemoto, Eugenia Giannopoulou, Takayuki Fujii, Yaxia Zhang, Emily M. Stein, Richard S. Bockman, Kyung-Hyun Park-Min
Abstract
Human periosteal skeletal stem cells (P-SSCs) are critical for cortical bone maintenance and repair. However, their in vivo identity, molecular characteristics, and specific markers remain unknown. Here, single-cell sequencing revealed human periosteum contains SSC clusters expressing known SSC markers, PDPN and PDGFRA. Notably, human P-SSCs, but not bone marrow SSCs (BM-SSCs), selectively expressed newly identified markers, LRP1 and CD13. These LRP1+CD13+ human P-SSCs were perivascular cells with high osteochondrogenic but minimal adipogenic potential. Upon transplantation into bone injuries in mice, they preserved self-renewal capability in vivo. Single-cell analysis of mouse periosteum further supported the preferential expression of LRP1 and CD13 in Prx1+ P-SSCs. When Lrp1 was conditionally deleted in Prx1-lineage cells, it led to severe bone deformity, short statue, and periosteal defects. By contrast, local treatment with a LRP1 agonist at the injury sites induced early P-SSC proliferation and bone healing. Thus, human and mouse periosteum contains unique osteochondrogenic stem cell subsets, and these P-SSCs express specific markers, LRP1 and CD13, with regulatory mechanism through LRP1 that enhances P-SSC function and bone repair.
Authors
Youngjae Jeong, Lorenzo R. Deveza, Laura Ortinau, Kevin Lei, John R. Dawson, Dongsu Park
Abstract
Despite their beneficial actions as immunosuppressants, glucocorticoids (GC) have devastating effects on the musculoskeletal and cardiac systems, as long-term treated patients exhibit high incidence of falls, bone fractures, and cardiovascular events. Herein, we show that GC upregulate simultaneously in bone, skeletal muscle, and the heart, the expression of E3 ubiquitin ligases (atrogenes), known to stimulate the proteasomal degradation of proteins. Activation of Vitamin D receptor (VDR) signaling with the VDR ligands 1,25D3 (calcitriol, 1,25-dihydroxyvitamin D3) or ED (eldecalcitol, 2β-(3-hydroxypropyloxy)-1,25-dihydroxyvitamin D3) prevented GC-induced atrogene upregulation in vivo and ex vivo in bone/muscle organ cultures and preserved tissue structure/mass and function of three tissues in vivo. Direct pharmacologic inhibition of the proteasome with carfilzomib also conferred musculoskeletal protection. Genetic loss of the atrogene MuRF1-mediated protein ubiquitination in ∆RING mice afforded temporary or sustained protection from GC excess in bone, or skeletal and heart muscle, respectively. We conclude that the atrogene pathway downstream of MuRF1 underlies GC action in bone, muscle, and the heart, and it can be pharmacologically or genetically targeted to confer protection against the damaging actions of GC simultaneously in the three tissues.
Authors
Amy Y. Sato, Meloney Cregor, Kevin McAndrews, Charles A. Schurman, Eric Schaible, Jennifer Shutter, Punit Vyas, Bhawana Adhikari, Monte S. Willis, Marjan Boerma, Tamara Alliston, Teresita Bellido
Abstract
Bone contains multiple pools of skeletal stem/progenitor cells (SSPCs), and SSPCs in periosteal compartments are known to exhibit higher regenerative potential than those in BM and endosteal compartments. However, the in vivo identity and hierarchical relationships of periosteal SSPCs (P-SSPCs) remain unclear due to a lack of reliable markers to distinguish BM SSPCs and P-SSPCs. Here, we found that periosteal mesenchymal progenitor cells (P-MPs) in periosteum can be identified based on Postn-CreERT2 expression. Postn-expressing periosteal subpopulation produces osteolineage descendants that fuel bones to maintain homeostasis and support regeneration. Notably, Postn+ P-MPs are likely derived from Gli1+ skeletal stem cells (SSCs). Ablation of Postn+ cells results in impairments in homeostatic cortical bone architecture and defects in fracture repair. Genetic deletion of Igf1r in Postn+ cells dampens bone fracture healing. In summary, our study provides a mechanistic understanding of bone regeneration through the regulation of region-specific Postn+ P-MPs.
Authors
Bei Yin, Fangyuan Shen, Qingge Ma, Yongcheng Liu, Xianglong Han, Xuyu Cai, Yu Shi, Ling Ye
Abstract
Mechanistically, S1P deficiency impeded COP II-mediated transport vesicles formation, which leads to proteins retention in the endoplasmic reticulum (ER) and subsequently ER distension. ER distension increased the contact between the ER and mitochondria, disrupting ER-to-mitochondria calcium flow, resulting in mitochondrial dysfunction and energy metabolism disturbance. Finally, using 2-APB to inhibit calcium ion channels and the senolytic drug dasatinib and quercetin (D + Q) partially rescued the aging and degenerative phenotypes caused by S1P deficiency. In conclusion, our findings suggest that S1P is a critical factor in causing IVDD in the process of aging and highlight the potential of targeting S1P as a therapeutic approach for age-related IVDD.
Authors
Bingjie Zheng, Xuyang Zhang, Xiangxi Kong, Jie Li, Bao Huang, Hui Li, Zhongyin Ji, Xiaoan Wei, Siyue Tao, Zhi Shan, Zemin Ling, Junhui Liu, Jian Chen, Fengdong Zhao
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