Cross-sectional studies of the causal link between asthma and osteoporosis: insights from Mendelian randomization and bioinformatics analysis.

The study, using data from Chongqing, China, and employing Mendelian randomization along with bioinformatics, establishes a causal link between asthma and osteoporosis, beyond glucocorticoid effects. Asthma may contribute to osteoporosis by accelerating bone turnover through inflammatory factors, disrupting the coupling between osteoblasts and osteoclasts, ultimately leading to osteoporosis. INTRODUCTION: Asthma and osteoporosis are prevalent health conditions with substantial public health implications. However, their potential interplay and the underlying mechanisms have not been fully elucidated. Previous research has primarily focused on the impact of glucocorticoids on osteoporosis, often overlooking the role of asthma itself. METHODS: We conducted a multi-stage stratified random sampling in Chongqing, China and excluded individuals with a history of glucocorticoid use. Participants underwent comprehensive health examinations, and their clinical data, including asthma status, were recorded. Logistic regression and Mendelian randomization were employed to investigate the causal link between asthma and osteoporosis. Furthermore, bioinformatics analyses and serum biomarker assessments were conducted to explore potential mechanistic pathways. RESULTS: We found a significant association between asthma and osteoporosis, suggesting a potential causal link. Mendelian Randomization analysis provided further support for this causal link. Bioinformatics analyses revealed that several molecular pathways might mediate the impact of asthma on bone health. Serum alkaline phosphatase levels were significantly elevated in the asthma group, suggesting potential involvement in bone turnover. CONCLUSION: Our study confirms a causal link between asthma and osteoporosis and highlights the importance of considering asthma in osteoporosis prediction models. It also suggests that asthma may accelerate osteoporosis by increasing bone turnover through inflammatory factors, disrupting the coupling between osteoblasts and osteoclasts, ultimately leading to bone loss.

TGF-ß/Alk5 signaling prevents osteoarthritis initiation via regulating the senescence of articular cartilage stem cells.

Osteoarthritis (OA) is the most common joint disease. The surface of joint cartilage is a defensive and first affected structure of articular cartilage (AC) during the pathogenesis of OA. Alk5 signaling is critical for maintaining AC homeostasis, however, the role and underlying mechanism for the involvement of Alk5 signaling in the phenotypes of articular cartilage stem cells (ACSCs) at the surface of AC is still unclear. The role of Alk5 in OA development was explored using an ACSCs-specific Alk5-deficient (cKO) mouse model. Alterations in cartilage structure were evaluated histologically. Senescence was detected by SA-ß-gal, while reactive oxygen species (ROS), MitoTracker, and LysoTracker staining were used to detect changes related to senescence. In addition, mice were injected intra-articularly with ganciclovir to limit the detrimental roles of senescent cells (SnCs). Alk5 cKO mice showed a decreased number of the slow-cell cycle cells and less lubricant secretion at the surface accompanied with drastically accelerated cartilage degeneration under ageing and surgically induced OA conditions. Further studies showed that Alk5 deficient ACSCs exhibited senescence-like manifestations including decreased proliferation and differentiation, more SA-ß-gal-positive cells and ROS production, as well as significantly swollen mitochondria and lysosome breakdown. We further found that local limitation of the detrimental roles of SnCs can attenuate the development of posttraumatic OA. Taken together, our findings suggest that Alk5 signaling acts as an important regulator of the SnCs in the superficial layer during AC maintenance and OA initiation.

FGFR3 deficiency enhances CXCL12-dependent chemotaxis of macrophages via upregulating CXCR7 and aggravates joint destruction in mice.

OBJECTIVES: This study aims to investigate the role and mechanism of FGFR3 in macrophages and their biological effects on the pathology of arthritis. METHODS: Mice with conditional knockout of FGFR3 in myeloid cells (R3cKO) were generated. Gait behaviours of the mice were monitored at different ages. Spontaneous synovial joint destruction was evaluated by digital radiographic imaging and µCT analysis; changes of articular cartilage and synovitis were determined by histological analysis. The recruitment of macrophages in the synovium was examined by immunostaining and monocyte trafficking assay. RNA-seq analysis, Western blotting and chemotaxis experiment were performed on control and FGFR3-deficient macrophages. The peripheral blood from non-osteoarthritis (OA) donors and patients with OA were analysed. Mice were treated with neutralising antibody against CXCR7 to investigate the role of CXCR7 in arthritis. RESULTS: R3cKO mice but not control mice developed spontaneous cartilage destruction in multiple synovial joints at the age of 13 months. Moreover, the synovitis and macrophage accumulation were observed in the joints of 9-month-old R3cKO mice when the articular cartilage was not grossly destructed. FGFR3 deficiency in myeloid cells also aggravated joint destruction in DMM mouse model. Mechanically, FGFR3 deficiency promoted macrophage chemotaxis partly through activation of NF-κB/CXCR7 pathway. Inhibition of CXCR7 could significantly reverse FGFR3-deficiency-enhanced macrophage chemotaxis and the arthritic phenotype in R3cKO mice. CONCLUSIONS: Our study identifies the role of FGFR3 in synovial macrophage recruitment and synovitis, which provides a new insight into the pathological mechanisms of inflammation-related arthritis.

Loss of Fgfr1 in chondrocytes inhibits osteoarthritis by promoting autophagic activity in temporomandibular joint.

Temporomandibular joint osteoarthritis (TMJ OA) is a common degenerative disease with few effective disease-modifying treatments in the clinic. Fibroblast growth factor (FGF) signaling is implicated in articular cartilage homeostasis, but the functional roles of FGFR1 in TMJ OA remain largely unknown. In this study, we report that deletion of Fgfr1 in TMJ chondrocytes delayed TMJ OA progression in the age-associated spontaneous OA model and the abnormal dental occlusion OA model. Immunohistochemical staining revealed that Fgfr1 deficiency decreased the expressions of MMP13 (matrix metalloproteinase-13), ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5), and COL10A1 but increased aggrecan expression level in two TMJ OA models. Furthermore, our data show that inactivation of FGFR1 signaling may promote autophagic activity in TMJ. FGFR1 inhibitor decreased the expressions of Mmp13, Adamts5, and Runx2 in IL-1ß-stimulated condylar chondrocytes, whereas autophagy inhibitors abrogated the protective effects of the FGFR1 inhibitor. Thus, our study indicates inactivated FGFR1 signaling ameliorates TMJ OA progression partially by promoting autophagic activity. Manipulation of this signaling may be a potential therapeutic approach to modify TMJ OA.

FGFR3 Deficiency Causes Multiple Chondroma-like Lesions by Upregulating Hedgehog Signaling.

Most cartilaginous tumors are formed during skeletal development in locations adjacent to growth plates, suggesting that they arise from disordered endochondral bone growth. Fibroblast growth factor receptor (FGFR)3 signaling plays essential roles in this process; however, the role of FGFR3 in cartilaginous tumorigenesis is not known. In this study, we found that postnatal chondrocyte-specific Fgfr3 deletion induced multiple chondroma-like lesions, including enchondromas and osteochondromas, adjacent to disordered growth plates. The lesions showed decreased extracellular signal-regulated kinase (ERK) activity and increased Indian hedgehog (IHH) expression. The same was observed in Fgfr3-deficient primary chondrocytes, in which treatment with a mitogen-activated protein kinase (MEK) inhibitor increased Ihh expression. Importantly, treatment with an inhibitor of IHH signaling reduced the occurrence of chondroma-like lesions in Fgfr3-deficient mice. This is the first study reporting that the loss of Fgfr3 function leads to the formation of chondroma-like lesions via downregulation of MEK/ERK signaling and upregulation of IHH, suggesting that FGFR3 has a tumor suppressor-like function in chondrogenesis.

Anemonin attenuates osteoarthritis progression through inhibiting the activation of IL-1ß/NF-κB pathway.

The osteoarthritis (OA) progression is now considered to be related to inflammation. Anemonin (ANE) is a small natural molecule extracted from various kinds of Chinese traditional herbs and has been shown to inhibiting inflammation response. In this study, we examined whether ANE could attenuate the progression of OA via suppression of IL-1ß/NF-κB pathway activation. Destabilization of the medial meniscus (DMM) was performed in 10-week-old male C57BL/6J mice. ANE was then intra-articularly injected into joint capsule for 8 and 12 weeks. Human articular chondrocytes and cartilage explants challenged with interleukin-1ß (IL-1ß) were treated with ANE. We found that ANE delayed articular cartilage degeneration in vitro and in vivo. In particular, proteoglycan loss and chondrocyte hypertrophy were significantly decreased in ANE -treated mice compared with vehicle-treated mice. ANE decreased the expressions of matrix metalloproteinase-13 (MMP13), A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), collagen X (Col X) while increasing Aggrecan level in murine with DMM surgery. ANE treatment also attenuated proteoglycan loss in human cartilage explants treated with IL-1ß ex vivo. ANE is a potent protective molecule for OA; it delays OA progression by suppressing ECM loss and chondrocyte hypertrophy partially by suppressing IL-1ß/NF-κB pathway activation.

A novel FGFR3-binding peptide inhibits FGFR3 signaling and reverses the lethal phenotype of mice mimicking human thanatophoric dysplasia.

Gain-of-function mutations in fibroblast growth factor receptor-3 (FGFR3) lead to several types of human skeletal dysplasia syndromes including achondroplasia, hypochondroplasia and thanatophoric dysplasia (TD). Currently, there are no effective treatments for these skeletal dysplasia diseases. In this study, we screened, using FGFR3 as a bait, a random 12-peptide phage library and obtained 23 positive clones that share identical amino acid sequences (VSPPLTLGQLLS), named as peptide P3. This peptide had high binding specificity to the extracellular domain of FGFR3. P3 inhibited tyrosine kinase activity of FGFR3 and its typical downstream molecules, extracellular signal-regulated kinase/mitogen-activated protein kinase. P3 also promoted proliferation and chondrogenic differentiation of cultured ATDC5 chondrogenic cells. In addition, P3 alleviated the bone growth retardation in bone rudiments from mice mimicking human thanatophoric dysplasia type II (TDII). Finally, P3 reversed the neonatal lethality of TDII mice. Thus, this study identifies a novel inhibitory peptide for FGFR3 signaling, which may serve as a potential therapeutic agent for the treatment of FGFR3-related skeletal dysplasia.

Intermittent PTH (1-34) injection rescues the retarded skeletal development and postnatal lethality of mice mimicking human achondroplasia and thanatophoric dysplasia.

Achondroplasia (ACH) and thanatophoric dysplasia (TD) are caused by gain-of-function mutations of fibroblast growth factor receptor 3 (FGFR3) and they are the most common forms of dwarfism and lethal dwarfism, respectively. Currently, there are few effective treatments for ACH. For the neonatal lethality of TD patients, no practical effective therapies are available. We here showed that systemic intermittent PTH (1-34) injection can rescue the lethal phenotype of TD type II (TDII) mice and significantly alleviate the retarded skeleton development of ACH mice. PTH-treated ACH mice had longer naso-anal length than ACH control mice, and the bone lengths of humeri and tibiae were rescued to be comparable with those of wild-type control mice. Our study also found that the premature fusion of cranial synchondroses in ACH mice was partially corrected after the PTH (1-34) treatment, suggesting that the PTH treatment may rescue the progressive narrowing of neurocentral synchondroses that cannot be readily corrected by surgery. In addition, we found that the PTH treatment can improve the osteopenia and bone structure of ACH mice. The increased expression of PTHrP and down-regulated FGFR3 level may be responsible for the positive effects of PTH on bone phenotype of ACH and TDII mice.

An Hsp70 promoter-based mouse for heat shock-induced gene modulation.

Physical therapy is extensively employed in clinical settings. Nevertheless, the absence of suitable animal models has resulted in an incomplete understanding of the in vivo mechanisms and cellular distribution that respond to physical stimuli. The objective of this research was to create a mouse model capable of indicating the cells affected by physical stimuli. In this study, we successfully established a mouse line based on the heat shock protein 70 (Hsp70) promoter, wherein the expression of CreERT2 can be induced by physical stimuli. Following stimulation of the mouse tail, ear, or cultured calvarias with heat shock (generated by heating, ultrasound, or laser), a distinct Cre-mediated excision was observed in cells stimulated by these physical factors with minimal occurrence of leaky reporter expression. The application of heat shock to Hsp70-CreERT2; FGFR2-P253R double transgenic mice or Hsp70-CreERT2 mice infected with AAV-BMP4 at calvarias induced the activation of Cre-dependent mutant FGFR2-P253R or BMP4 respectively, thereby facilitating the premature closure of cranial sutures or the repair of calvarial defects. This novel mouse line holds significant potential for investigating the underlying mechanisms of physical therapy, tissue repair and regeneration, lineage tracing, and targeted modulation of gene expression of cells in local tissue stimulated by physical factor at the interested time points. KEY MESSAGES: In the study, an Hsp70-CreERT2 transgenic mouse was generated for heat shock-induced gene modulation. Heat shock, ultrasound, and laser stimulation effectively activated Cre expression in Hsp70-CreERT2; reporter mice, which leads to deletion of floxed DNA sequence in the tail, ear, and cultured calvaria tissues of mice. Local laser stimuli on cultured calvarias effectively induce Fgfr2-P253R expression in Hsp70-mTmG-Fgfr2-P253R mice and result in accelerated premature closure of cranial suture. Heat shock activated AAV9-FLEX-BMP4 expression and subsequently promoted the repair of calvarial defect of Hsp70-CreERT2; Rosa26-mTmG mice.

A Novel Cargo Delivery System-AnCar-ExoLaIMTS Ameliorates Arthritis via Specifically Targeting Pro-Inflammatory Macrophages.

Macrophages are heterogenic phagocytic cells that play distinct roles in physiological and pathological processes. Targeting different types of macrophages has shown potent therapeutic effects in many diseases. Although many approaches are developed to target anti-inflammatory macrophages, there are few researches on targeting pro-inflammatory macrophages, which is partially attributed to their non-s pecificity phagocytosis of extracellular substances. In this study, a novel recombinant protein is constructed that can be anchored on an exosome membrane with the purpose of targeting pro-inflammatory macrophages via antigen recognition, which is named AnCar-ExoLaIMTS . The data indicate that the phagocytosis efficiencies of pro-inflammatory macrophages for different AnCar-ExoLaIMTS show obvious differences. The AnCar-ExoLaIMTS3 has the best targeting ability for pro-inflammatory macrophages in vitro and in vivo. Mechanically, AnCar-ExoLaIMTS3 can specifically recognize the leucine-rich repeat domain of the TLR4 receptor, and then enter into pro-inflammatory macrophages via the TLR4-mediated receptor endocytosis pathway. Moreover, AnCar-ExoLaIMTS3 can efficiently deliver therapeutic cargo to pro-inflammatory macrophages and inhibit the synovial inflammatory response via downregulation of HIF-1α level, thus ameliorating the severity of arthritis in vivo. Collectively, the work established a novel gene/drug delivery system that can specifically target pro-inflammatory macrophages, which may be beneficial for the treatments of arthritis and other inflammatory diseases.

Genetic inhibition of fibroblast growth factor receptor 1 in knee cartilage attenuates the degeneration of articular cartilage in adult mice.

OBJECTIVE: Fibroblast growth factor (FGF) family members are involved in the regulation of articular cartilage homeostasis. The aim of this study was to investigate the function of FGF receptor 1 (FGFR-1) in the development of osteoarthritis (OA) and its underlying mechanisms. METHODS: FGFR-1 was deleted from the articular chondrocytes of adult mice in a cartilage-specific and tamoxifen-inducible manner. Two OA models (aging-associated spontaneous OA, and destabilization-induced OA), as well as an antigen-induced arthritis (AIA) model, were established and tested in Fgfr1-deficient and wild-type (WT) mice. Alterations in cartilage structure and the loss of proteoglycan were assessed in the knee joints of mice of either genotype, using these 3 arthritis models. Primary chondrocytes were isolated and the expression of key regulatory molecules was assessed quantitatively. In addition, the effect of an FGFR-1 inhibitor on human articular chondrocytes was examined. RESULTS: The gross morphologic features of Fgfr1-deficient mice were comparable with those of WT mice at both the postnatal and adult stages. The articular cartilage of 12-month-old Fgfr1-deficient mice displayed greater aggrecan staining compared to 12-month-old WT mice. Fgfr1 deficiency conferred resistance to the proteoglycan loss induced by AIA and attenuated the development of cartilage destruction after surgically induced destabilization of the knee joint. The chondroprotective effect of FGFR-1 inhibition was largely associated with decreased expression of matrix metalloproteinase 13 (MMP-13) and up-regulation of FGFR-3 in mouse and human articular chondrocytes. CONCLUSION: Disruption of FGFR-1 in adult mouse articular chondrocytes inhibits the progression of cartilage degeneration. Down-regulation of MMP-13 expression and up-regulation of FGFR-3 levels may contribute to the phenotypic changes observed in Fgfr1-deficient mice.

IRE1α protects against osteoarthritis by regulating progranulin-dependent XBP1 splicing and collagen homeostasis.

Osteoarthritis (OA) is a full-joint, multifactorial, degenerative and inflammatory disease that seriously affects the quality of life of patients due to its disabling and pain-causing properties. ER stress has been reported to be closely related to the progression of OA. The inositol-requiring enzyme 1α/X-box-binding protein-1 spliced (IRE1α/XBP1s) pathway, which is highly expressed in the chondrocytes of OA patients, promotes the degradation and refolding of abnormal proteins during ER stress and maintains the stability of the ER environment of chondrocytes, but its function and the underlying mechanisms of how it contributes to the progression of OA remain unclear. This study investigates the role of IRE1α/ERN1 in OA. Specific deficiency of ERN1 in chondrocytes spontaneously resulted in OA-like cartilage destruction and accelerated OA progression in a surgically induced arthritis model. Local delivery of AdERN1 relieved degradation of the cartilage matrix and prevented OA development in an ACLT-mediated model. Mechanistically, progranulin (PGRN), an intracellular chaperone, binds to IRE1α, promoting its phosphorylation and splicing of XBP1u to generate XBP1s. XBP1s protects articular cartilage through TNF-α/ERK1/2 signaling and further maintains collagen homeostasis by regulating type II collagen expression. The chondroprotective effect of IRE1α/ERN1 is dependent on PGRN and XBP1s splicing. ERN1 deficiency accelerated cartilage degeneration in OA by reducing PGRN expression and XBP1s splicing, subsequently decreasing collagen II expression and triggering collagen structural abnormalities and an imbalance in collagen homeostasis. This study provides new insights into OA pathogenesis and the UPR and suggests that IRE1α/ERN1 may serve as a potential target for the treatment of joint degenerative diseases, including OA.

Localized all-cell knock-out (LACKO) strategy is needed for studying adult stage diseases.

Knock-out (KO) mouse models have been increasingly used to dissect the roles of genes in development, diseases, and injuries. The conventional KO approach allows study of the role of the targeted genes in all cells, but it sometimes results in embryonic lethality. Using the classical conditional KO approach, reseachers can avoid embryonic lethality, but they cannot modulate genes in a temporally controllable way. The inducible KO technique, which has been used to study the role of a gene in life processes at the adult stage, avoids the potential interfering role of changed structures and functions of the tissues/organs resulting from the early KO of the gene in the non-inducible conditional knock-out approach. However, it is difficult to develop clinically applicable therapies for some diseases or injuries based on the results obtained from inducible KO studies since the total summed role of the genes of interest in those diseases or injuries cannot be determined and, therefore, the potential therapeutic effects of the applied modulators of the activity of the targeted genes cannot be predicted. To solve this problem of the classical conditional and inducible KO approaches, researchers need to simultaneously knock out a gene in all cells locally-a process called the localized all-cell KO (LACKO) strategy. We describe the concept of this new strategy in detail in this article.

Expansion of FGFR3-positive nucleus pulposus cells plays important roles in postnatal nucleus pulposus growth and regeneration.

BACKGROUND: Intervertebral disc degeneration (IVDD) can cause low back pain, a major public health concern. IVDD is characterized with loss of cells especially those in nucleus pulposus (NP), due to the limited proliferative potential and regenerative ability. Few studies, however, have been carried out to investigate the in vivo proliferation events of NP cells and the cellular contribution of a specific subpopulation of NP during postnatal growth or regeneration. METHODS: We generated FGFR3-3*Flag-IRES-GFP mice and crossed FGFR3-CreERT2 mice with Rosa26-mTmG, Rosa26-DTA and Rosa26-Confetti mice, respectively, to perform inducible genetic tracing studies. RESULTS: Expression of FGFR3 was found in the outer region of NP with co-localized expressions of proliferating markers. By fate mapping studies, FGFR3-positive (FGFR3+) NP cells were found proliferate from outer region to inner region of NP during postnatal growth. Clonal lineage tracing by Confetti mice and ablation of FGFR3·+ NP cells by DTA mice further revealed that the expansion of the FGFR3+ cells was required for the morphogenesis and homeostasis of postnatal NP. Moreover, in degeneration and regeneration model of mouse intervertebral disc, FGFR3+ NP cells underwent extensive expansion during the recovery stage. CONCLUSION: Our present work demonstrates that FGFR3+ NP cells are novel subpopulation of postnatal NP with long-existing proliferative capacity shaping the adult NP structure and participating in the homeostasis maintenance and intrinsic repair of NP. These findings may facilitate the development of new therapeutic approaches for IVD regeneration.

Inhibition of aberrant Hif1α activation delays intervertebral disc degeneration in adult mice.

The intervertebral disc (IVD) is the largest avascular tissue. Hypoxia-inducible factors (HIFs) play essential roles in regulating cellular adaptation in the IVD under physiological conditions. Disc degeneration disease (DDD) is one of the leading causes of disability, and current therapies are ineffective. This study sought to explore the role of HIFs in DDD pathogenesis in mice. The findings of this study showed that among HIF family members, Hif1α was significantly upregulated in cartilaginous endplate (EP) and annulus fibrosus (AF) tissues from human DDD patients and two mouse models of DDD compared with controls. Conditional deletion of the E3 ubiquitin ligase Vhl in EP and AF tissues of adult mice resulted in upregulated Hif1α expression and age-dependent IVD degeneration. Aberrant Hif1α activation enhanced glycolytic metabolism and suppressed mitochondrial function. On the other hand, genetic ablation of the Hif1α gene delayed DDD pathogenesis in Vhl-deficient mice. Administration of 2-methoxyestradiol (2ME2), a selective Hif1α inhibitor, attenuated experimental IVD degeneration in mice. The findings of this study show that aberrant Hif1α activation in EP and AF tissues induces pathological changes in DDD, implying that inhibition of aberrant Hif1α activity is a potential therapeutic strategy for DDD.

Treating Autoimmune Inflammatory Diseases with an siERN1-Nanoprodrug That Mediates Macrophage Polarization and Blocks Toll-like Receptor Signaling.

The clinical application of small interfering RNA (siRNA) drugs provides promising opportunities to develop treatment strategies for autoimmune inflammatory diseases. In this study, siRNAs targeting the endoplasmic reticulum to nucleus signaling 1 (ERN1) gene (siERN1) were screened. Two cationic polymers, polyethylenimine (PEI) and poly(ß-amino amine) (PBAA), which can improve the efficiency of the siRNA transfection, were used as siERN1 delivery carriers. They were implemented to construct a nanodrug delivery system with macrophage-targeting ability and dual responsiveness for the treatment of autoimmune inflammatory diseases. In terms of the mechanism, siERN1 can regulate the intracellular calcium ion concentration by interfering with the function of inositol 1,4,5-trisphosphate receptor 1/3 (IP3R1/3) and thus inducing M2 polarization of macrophages. Furthermore, siERN1-nanoprodrug [FA (folic acid)-PEG-R(RKKRRQRRR)-NPs(ss-PBAA-PEI)@siERN1] acts as a conductor of macrophage polarization by controlling the calcium ion concentration and is an inhibitor of MyD88-dependent Toll-like receptor signaling. The results revealed that the FA-PEG-R-NPs@siERN1 has universal biocompatibility, long-term drug release responsiveness, superior targeting properties, and therapeutic effects in mouse collagen-induced arthritis and inflammatory bowel disease models. In conclusion, this study reveals a potential strategy to treat autoimmune inflammatory disorders.

Long term usage of dexamethasone accelerating accelerates the initiation of osteoarthritis via enhancing chondrocyte apoptosis and the extracellular matrix calcification and apoptosis of chondrocytes.

Systemic application of glucocorticoids is an essential anti-inflammatory and immune-modulating therapy for severe inflammatory or autoimmunity conditions. However, its long-term effects on articular cartilage of patients' health need to be further investigated. In this study, we studied the effects of dexamethasone (Dex) on the homeostasis of articular cartilage and the progress of destabilization of medial meniscus (DMM)-induced osteoarthritis (OA) in adult mice. Long-term administration of Dex aggravates the proteoglycan loss of articular cartilage and drastically accelerates cartilage degeneration under surgically induced OA conditions. In addition, Dex increases calcium content in calcified cartilage layer of mice and the samples from OA patients with a history of long-term Dex treatment. Moreover, long term usage of Dex results in decrease subchondral bone mass and bone density. Further studies showed that Dex leads to calcification of extracellular matrix of chondrocytes partially through activation of AKT, as well as promotes apoptosis of chondrocytes in calcified cartilage layer. Besides, Dex weakens the stress-response autophagy with the passage of time. Taken together, our data indicate that long-term application of Dex may predispose patients to OA and or even accelerate the OA disease progression development of OA patients.

Targeting local lymphatics to ameliorate heterotopic ossification via FGFR3-BMPR1a pathway.

Acquired heterotopic ossification (HO) is the extraskeletal bone formation after trauma. Various mesenchymal progenitors are reported to participate in ectopic bone formation. Here we induce acquired HO in mice by Achilles tenotomy and observe that conditional knockout (cKO) of fibroblast growth factor receptor 3 (FGFR3) in Col2+ cells promote acquired HO development. Lineage tracing studies reveal that Col2+ cells adopt fate of lymphatic endothelial cells (LECs) instead of chondrocytes or osteoblasts during HO development. FGFR3 cKO in Prox1+ LECs causes even more aggravated HO formation. We further demonstrate that FGFR3 deficiency in LECs leads to decreased local lymphatic formation in a BMPR1a-pSmad1/5-dependent manner, which exacerbates inflammatory levels in the repaired tendon. Local administration of FGF9 in Matrigel inhibits heterotopic bone formation, which is dependent on FGFR3 expression in LECs. Here we uncover Col2+ lineage cells as an origin of lymphatic endothelium, which regulates local inflammatory microenvironment after trauma and thus influences HO development via FGFR3-BMPR1a pathway. Activation of FGFR3 in LECs may be a therapeutic strategy to inhibit acquired HO formation via increasing local lymphangiogenesis.

FGF/FGFR signaling in health and disease.

Growing evidences suggest that the fibroblast growth factor/FGF receptor (FGF/FGFR) signaling has crucial roles in a multitude of processes during embryonic development and adult homeostasis by regulating cellular lineage commitment, differentiation, proliferation, and apoptosis of various types of cells. In this review, we provide a comprehensive overview of the current understanding of FGF signaling and its roles in organ development, injury repair, and the pathophysiology of spectrum of diseases, which is a consequence of FGF signaling dysregulation, including cancers and chronic kidney disease (CKD). In this context, the agonists and antagonists for FGF-FGFRs might have therapeutic benefits in multiple systems.

Fgfr3 mutation disrupts chondrogenesis and bone ossification in zebrafish model mimicking CATSHL syndrome partially via enhanced Wnt/ß-catenin signaling.

CATSHL syndrome, characterized by camptodactyly, tall stature and hearing loss, is caused by loss-of-function mutations of fibroblast growth factor receptors 3 (FGFR3) gene. Most manifestations of patients with CATSHL syndrome start to develop in the embryonic stage, such as skeletal overgrowth, craniofacial abnormalities, however, the pathogenesis of these phenotypes especially the early maldevelopment remains incompletely understood. Furthermore, there are no effective therapeutic targets for this skeleton dysplasia. Methods: We generated fgfr3 knockout zebrafish by CRISPR/Cas9 technology to study the developmental mechanisms and therapeutic targets of CATSHL syndrome. Several zebrafish transgenic lines labeling osteoblasts and chondrocytes, and live Alizarin red staining were used to analyze the dynamical skeleton development in fgfr3 mutants. Western blotting, whole mount in situ hybridization, Edu labeling based cell proliferation assay and Wnt/ß-catenin signaling antagonist were used to explore the potential mechanisms and therapeutic targets. Results: We found that fgfr3 mutant zebrafish, staring from early development stage, showed craniofacial bone malformation with microcephaly and delayed closure of cranial sutures, chondroma-like lesion and abnormal development of auditory sensory organs, partially resembling the clinical manifestations of patients with CATSHL syndrome. Further studies showed that fgfr3 regulates the patterning and shaping of pharyngeal arches and the timely ossification of craniofacial skeleton. The abnormal development of pharyngeal arch cartilage is related to the augmented hypertrophy and disordered arrangement of chondrocytes, while decreased proliferation, differentiation and mineralization of osteoblasts may be involved in the delayed maturation of skull bones. Furthermore, we revealed that deficiency of fgfr3 leads to enhanced IHH signaling and up-regulated canonical Wnt/ß-catenin signaling, and pharmacological inhibition of Wnt/ß-catenin could partially alleviate the phenotypes of fgfr3 mutants. Conclusions: Our study further reveals some novel phenotypes and underlying developmental mechanism of CATSHL syndrome, which deepens our understanding of the pathogenesis of CATSHL and the role of fgfr3 in skeleton development. Our findings provide evidence that modulation of Wnt/ß-catenin activity could be a potential therapy for CATSHL syndrome and related skeleton diseases.