mTOR mutation disrupts larval zebrafish tail fin regeneration via regulating proliferation of blastema cells and mitochondrial functions.

BACKGROUND: The larval zebrafish tail fin can completely regenerate in 3 days post amputation. mTOR, the main regulator of cell growth and metabolism, plays an essential role in regeneration. Lots of studies have documented the role of mTOR in regeneration. However, the mechanisms involved are still not fully elucidated. MATERIALS AND RESULTS: This study aimed to explore the role and mechanism of mTOR in the regeneration of larval zebrafish tail fins. Initially, the spatial and temporal expression of mTOR signaling in the larval fin was examined, revealing its activation following tail fin amputation. Subsequently, a mTOR knockout (mTOR-KO) zebrafish line was created using CRISPR/Cas9 gene editing technology. The investigation demonstrated that mTOR depletion diminished the proliferative capacity of epithelial and mesenchymal cells during fin regeneration, with no discernible impact on cell apoptosis. Insight from SMART-seq analysis uncovered alterations in the cell cycle, mitochondrial functions and metabolic pathways when mTOR signaling was suppressed during fin regeneration. Furthermore, mTOR was confirmed to enhance mitochondrial functions and Ca2 + activation following fin amputation. These findings suggest a potential role for mTOR in promoting mitochondrial fission to facilitate tail fin regeneration. CONCLUSION: In summary, our results demonstrated that mTOR played a key role in larval zebrafish tail fin regeneration, via promoting mitochondrial fission and proliferation of blastema cells.

Comparison Between Multisite Injection and Single Rotator Interval Injection of Corticosteroid in Primary Frozen Shoulder (Adhesive Capsulitis): A Randomized Controlled Trial.

BACKGROUND: Steroid injection is a commonly used conservative treatment for primary frozen shoulder (PFS), but the optimal injection site remains undetermined. OBJECTIVES: We conducted a prospective randomized controlled trial of multisite combined injection (MCI) vs single rotator interval injection (SRI). STUDY DESIGN: A randomized double-blinded controlled trial. SETTING: Center for Joint Surgery, Department of Orthopaedic Surgery, the Second Affiliated Hospital of Chongqing Medical University. METHODS: Sixty-four patients with PFS were randomly assigned to 2 groups. The experimental group received MCI in the rotator interval, intraarticular, and subacromial bursa; the control group received an SRI. Both groups were injected with one mL of 40 mg triamcinolone acetonide and 4 mL of 2% lidocaine. The injection process was completed under ultrasound guidance. Follow-up points were 4, 8, and 12 weeks postinjection. The outcome measures included the Visual Analog Scale (VAS) score, the American Shoulder and Elbow Surgeons (ASES) score, the Constant-Murley Shoulder (CMS) score, passive range of motion of the shoulder, and patient satisfaction rating. RESULTS: Thirty patients in the MCI group and 29 patients in the SRI group were included in the data analysis. All the outcomes in the 2 groups were significantly better postinjection than preinjection. The MCI group had a lower VAS score than the SRI group at 4 weeks (3.1 ± 1.2 vs 4.3 ± 1.6) and 8 weeks (2.2 ± 1.2 vs. 3.4 ± 1.2) (P < 0.05). Compared with the SRI group, the MCI group had a significant improvement in flexion and abduction (P < 0.01). Additionally, the ASES and CMS scores in the MCI group were better than those in the SRI group at 4, 8 and 12 weeks (P < 0.01). LIMITATIONS: Limitations include the sample size of this study is small and a that it was conducted at a single-center. CONCLUSIONS: Both MCI and SRI effectively alleviated pain and restored range of motion in patients with PFS. However, the MCI group had obviously lower early pain scores, better flexion and abduction, and better function scores than the SRI group; no additional adverse events were observed.

Dynamic Tensile Stress Promotes Regeneration of Achilles Tendon in a Panda Rope Bridge Technique Mice Model.

Regeneration of ruptured Achilles tendon remains a clinical challenge owing to its limited regenerative capacity. Dynamic tensile stress plays a positive role in the regeneration of tendon, although the specific underlying mechanisms remain unclear. In this study, the Achilles tendon defect-regeneration model was created in male C57BL/6 mice aged 8 weeks. The animals were randomly assigned to four groups-repair, non-repair, repair with fixation, and non-repair with fixation. The repair group and repair with fixation group adopted the panda rope bridge technique (PRBT) repair method. Our results demonstrated the presence of more densely aligned and mature collagen fibers, as well as more tendon-related makers, in the repair group at both 2- and 4-week post-surgery. Furthermore, the biomechanical strength of the regenerated tendon in the repair group was highly improved. Most importantly, the expressions of integrin αv and its downstream and the phosphorylation levels of FAK and ERK were remarkably higher in the repair group than in the other groups. Furthermore, blocking FAK or ERK with selective inhibitors PF573228 and U0126 resulted in obvious adverse effects on the histological structure of the regenerated Achilles tendon. In summary, this study demonstrated that dynamic tensile stress based on the PRBT could effectively promote the regeneration of the Achilles tendon, suggesting that dynamic tensile stress enhances the cell proliferation and tenogenic differentiation via the activation of the integrin/FAK/ERK signaling pathway.

Autophagy and apoptosis: regulatory factors of chondrocyte phenotype transition in osteoarthritis.

Osteoarthritis (OA) is the main pathogenic factor in diseases that cause joint deformities. As the main manifestation of the progress of OA, cartilage degradation has been closely associated with the degeneration of chondrocytes, which is induced by inflammatory factors and other trauma factors. Autophagy and apoptosis are the main mechanisms for cells to maintain homeostasis and play crucial roles in OA. Under the influence of external environmental factors (such as aging and injury), the metabolism of cells can be altered, which may affect the extent of autophagy and apoptosis. With the progression of OA, these changes can alter the cell phenotypes, and the cells of different phenotypes display distinct differences in morphology and function. In this review, we have summarized the alteration in cell metabolism, autophagy, and the extent of apoptosis during OA progression and its effects on the cell phenotypes to provide new ideas for further research on the mechanisms of phenotypic transition and therapeutic strategies so as to reverse the cell phenotypes.

Deletion of DYRK1A Accelerates Osteoarthritis Progression Through Suppression of EGFR-ERK Signaling.

Dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) signaling is involved in the dynamic balance of catabolism and anabolism in articular chondrocytes. This study aimed to investigate the roles and mechanism of DYRK1A in the pathogenesis of osteoarthritis (OA). The expressions of DYRK1A and its downstream signal epidermal growth factor receptor (EGFR) were detected in the cartilage of adult wild-type mice with destabilized medial meniscus (DMM) and articular cartilage of patients with OA. We measured the progression of osteoarthritis in chondrocyte-specific knockout DYRK1A(DYRK1A-cKO) mice after DMM surgery. Knee cartilage was histologically scored and assessed the effects of DYRK1A deletion on chondrocyte catabolism and anabolism. The effect of inhibiting EGFR signaling in chondrocytes from DYRK1A-cKO mice was analyzed. Trauma-induced OA mice and OA patients showed downregulation of DYRK1A and EGFR signaling pathways. Conditional DYRK1A deletion aggravates DMM-induced cartilage degeneration, reduces the thickness of the superficial cartilage, and increases the number of hypertrophic chondrocytes. The expression of collagen type II, p-ERK, and aggrecan was also downregulated, and the expression of collagen type X was upregulated in the articular cartilage of these mice. Our findings suggest that DYRK1A delays the progression of knee osteoarthritis in mice, at least in part, by maintaining EGFR-ERK signaling in articular chondrocytes.

Comparison of Outcomes of Two Different Corticosteroid Injection Approaches for Primary Frozen Shoulder: A Randomized Controlled Study.

OBJECTIVE: Corticosteroid injection is a common treatment for primary frozen shoulder, but controversy remains regarding whether different injection approaches to the glenohumeral joint have similar clinical benefits. DESIGN: Randomized controlled clinical trial. PATIENTS: A total of 60 patients with primary frozen shoulder were divided randomly into either anterior or posterior approach groups. METHODS: Both groups received a 5-mL drug injection, including 1 mL 40 mg/mL triamcinolone acetonide and 4 mL 2% lidocaine. Follow-up time-points were 4, 8 and 12 weeks post-injection. Outcome measures included visual analogue scale score, Constant-Murley score, and passive range of motion of the shoulder joint. RESULTS: All outcome measures improved over the follow-up period compared with those of previous follow-up time-points within the groups. The primary finding was that the visual analogue scale score in the anterior group was better than that in the posterior group at each follow-up time-point (all p < 0.05). In addition, improvement in function score and external rotation was faster and significant in the anterior group in the early stages (p = 0.02). CONCLUSION: The anterior approach achieves more satisfactory results in pain control and offers better recovery of functional activity than posterior approach in the early period for primary frozen shoulder.

Outcomes of early versus late functional weight-bearing after the acute Achilles tendon rupture repair with minimally invasive surgery: a randomized controlled trial.

INTRODUCTION: Optimal postoperative rehabilitation regimen for acute Achilles tendon rupture (AATR) remains unclear. It is important to evaluate whether early functional weight-bearing rehabilitation program after minimally invasive repair results in an earlier return to pre-injury activity but increases the risk of re-rupture. MATERIALS AND METHODS: This was a prospective randomized controlled trial involving 68 AATR patients undergoing minimally invasive surgery. 34 patients were enrolled in early weight­bearing mobilization accelerated rehabilitation group (AR group); 34 patients were enrolled in the traditional rehabilitation (TR) group. Outcomes measures included American Orthopaedic Foot and Ankle Society Score (AOFAS) score and Achilles Tendon Total Rupture Score (ATRS) score before surgery and 3, 6, and 12 months after surgery, incidence rate of Achilles tendon re-rupture and total complications, length of hospital stay, time return to work and sports. RESULTS: There was no significant difference in preoperative basic data between the two groups. However, AOFAS score and ATRS score were better in AR group than TR group at 3 months postoperatively (92.4 ± 3.5 vs 88.3 ± 4.5, P < 0.01; 91.1 ± 4.4 vs 88.9 ± 3.4, P = 0.03, respectively), the mean length of hospital stay (4.7 ± 1.5 vs 7.6 ± 2.0 days, P < 0.01) and time return to work (4.5 ± 1.0 vs 7.5 ± 1.6 weeks, P < 0.01) were shorter in AR group than in TR group. No statistical significance was calculated in patient-reported outcomes during the rest of the follow-up time and complications. CONCLUSION: Early accelerated rehabilitation with weight-bearing in patients with AATR after minimally invasive surgery results in better early functional outcomes and shows similar security and feasibility. REGISTRATION NO: ChiCTR2100043398.

m6A regulator-mediated methylation modification patterns and immune microenvironment infiltration characterization in osteoarthritis.

Osteoarthritis (OA) is a common disease in orthopedics. RNA N6-methyladenosine (m6A) exerts an essential effect in a variety of biological processes in the eukaryotes. In this study, we determined the effect of m6A regulators in the OA along with performing the subtype classification. Differential analysis of OA and normal samples in the database of Gene Expression Omnibus identified 9 significantly differentially expressed m6A regulators. These regulators were monitored by a random forest algorithm so as to evaluate the risk of developing OA disease. On the basis of these 9 moderators, a nomogram was established. The results of decision curve analysis suggested that the patients could benefit from a nomogram model. The OA sample was classified as 2 m6A models through a consensus clustering algorithm in accordance with these 9 regulators. These 2 m6A patterns were then assessed with principal component analysis. We also determined the m6A scores for the 2 m6A patterns and their correlation with immune infiltration. The results indicated that type A had a higher m6A score than type B. Thus, we suggest that the m6A pattern may provide a new approach for diagnose and provide novel ideas for molecular targeted therapy of OA.

Risk Factors and Corresponding Management for Suture Anchor Pullout during Arthroscopic Rotator Cuff Repair.

INTRODUCTION: Due to the aging of the population, the incidence of rotator cuff tears is growing. For rotator cuff repair, arthroscopic suture-anchor repair has gradually replaced open transosseous repair, so suture anchors are now considered increasingly important in rotator cuff tear reconstruction. There are some but limited studies of suture anchor pullout after arthroscopic rotator cuff repair. However, there is no body of knowledge in this area, which makes it difficult for clinicians to predict the risk of anchor pullout comprehensively and manage it accordingly. METHODS: The literature search included rotator cuff repair as well as anchor pullout strength. A review of the literature was performed including all articles published in PubMed until September 2021. Articles of all in vitro biomechanical and clinical trial levels in English were included. After assessing all abstracts (n = 275), the full text and the bibliographies of the relevant articles were analyzed for the questions posed (n = 80). Articles including outcomes without the area of interest were excluded (n = 22). The final literature research revealed 58 relevant articles. Narrative synthesis was undertaken to bring together the findings from studies included in this review. RESULT: Based on the presented studies, the overall incidence of anchor pullout is not low, and the incidence of intraoperative anchor pullout is slightly higher than in the early postoperative period. The risk factors for anchor pullout are mainly related to bone quality, insertion depth, insertion angle, size of rotator cuff tear, preoperative corticosteroid injections, anchor design, the materials used to produce anchors, etc. In response to the above issues, we have introduced and evaluated management techniques. They include changing the implant site of anchors, cement augmentation for suture anchors, increasing the number of suture limbs, using all-suture anchors, using an arthroscopic transosseous knotless anchor, the Buddy anchor technique, Steinmann pin anchoring, and transosseous suture repair technology. DISCUSSION: However, not many of the management techniques have been widely used in clinical practice. Most of them come from in vitro biomechanical studies, so in vivo randomized controlled trials with larger sample sizes are needed to see if they can help patients in the long run.

Panda rope bridge technique versus open repair of acute Achilles tendon rupture: A comparative clinical study.

PURPOSE: The treatment options of acute Achilles tendon rupture (AATR) remain controversial. This article aims to compare the efficacy of a new surgical procedure, the panda rope bridge technique (PRBT) with open surgery of AATR. METHODS: Ninety-eight patients with AATR were recruited, 53 underwent the PBRT, and 45 underwent open surgery. The operation time, postoperative American Orthopaedic Foot and Ankle Score, Achilles Tendon Rupture Score, complications and time to return to work and restore exercise were documented. RESULTS: The average operation time, intraoperative blood loss and complication rate were 35.1 min, 18.2 ml and 3.8%, respectively, in the PRBT group, which were significantly lower than those of the open surgery group (P<0.001). The post-operative American Orthopaedic Foot and Ankle Score of 99.6 and the Achilles Tendon Rupture Score of 97.5 in the PRBT group were significantly higher than that of the open surgery group (P<0.001). The time to return to work and return to exercise were shorter in the PRBT group (P<0.001). CONCLUSION: Compared to open surgery, PRBT is a better approach to the management of AATR. PRBT offers accelerated recovery, lower occurrence of post-operative complications and improved recovery of ankle joint function.

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.

Association rules analysis on patterns of multimorbidity in adults: based on the National Health and Nutrition Examination Surveys database.

OBJECTIVE: To explore the prevalence and patterns of multimorbidity in population with different genders and age ranges. DESIGN: A cross-sectional study. SETTING: National Health and Nutrition Examination Surveys database. PARTICIPANTS: 12 576 patients. PRIMARY AND SECONDARY OUTCOME MEASURES: The prevalence and patterns of multimorbidity. RESULTS: High cholesterol had the highest prevalence in all population (33.4 (95% CI: 32.0 to 34.9)) and males. In females <65 years, the most prevalent disease was sleep disorder (32.1 (95% CI: 29.6 to 34.5)) while in females ≥65 years, hypertension was the most prevalent disease (63.9 (95% CI: 59.9 to 67.9)). Hypertension and high cholesterol were associated with the highest support (occur together most frequently) in all population regardless of genders. Hypertension displayed the highest betweenness centrality (mediating role in the network) followed by high cholesterol and arthritis in all population. For males aged <65 years, hypertension and high cholesterol presented the highest betweenness centrality. In males ≥65 years, hypertension, high cholesterol and arthritis were the top three diseases of degree centrality (direct association with other conditions). As for females ≥65 years, hypertension showed the highest betweenness centrality followed by high cholesterol and arthritis. The associations of hypertension, arthritis and one other item with high cholesterol presented the highest support in all population. In males, the associations of depression, hypertension with sleep disorders had the highest lift (the chance of co-occurrence of the conditions and significant association). Among females, the associations of depression, arthritis with sleep disorders had the highest lift. CONCLUSION: Hypertension and high cholesterol were prevalent in all population, regardless of females and males. Hypertension and high cholesterol, arthritis and hypertension, and diabetes and hypertension were more likely to coexist. The findings of this study might help make plans for the management and primary care of people with one or more diseases.

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.

A Systematic Review and Meta-Analysis of Combined Antibiotic Spacer with Ilizarov Methods in the Treatment of Infected Nonunion of Tibia.

BACKGROUND: The objective of this systematic review was to evaluate current studies available reporting the antibiotic spacer combined with Ilizarov methods in the treatment of infected nonunion of tibia and to perform meta-analysis of bone results and infection recurrence to assess the efficacy of an antibiotic spacer combined with Ilizarov methods. METHODS: The MEDLINE, Embase, Cochrane Library, CNKI, and CBM (Chinese Biological Medicine) databases were searched for articles published between January 2000 and July 2020. Assessment of study quality was performed using a modified version of the Newcastle-Ottawa scale. Effect size and 95% confidence intervals were calculated for the main outcome. Heterogeneity was assessed. Fixed-effect modeling and Stata version 15.1 were used to analyze the data. Sensitivity analyses were conducted with the evidence of heterogeneity. RESULTS: 11 studies involving 210 patients with infected nonunion of tibia were finally included in our meta-analysis. Bone results and infection recurrence were analyzed based on the single-arm meta-analysis. The average of external fixation index (EFI) was 46.88 days/cm in all studies included. The excellent rate in bone results and the rate of infection recurrence was 65% (95% CI: [0.22, 0.97], I 2 = 0.0%, P = 0.932) and 6.99% (95% CI: [0.052, 0.325], I 2 = 0.0%, P = 1.000) in patients with infected nonunion of tibia treated with an antibiotic spacer combined with Ilizarov methods. CONCLUSIONS: Our meta-analysis revealed that the patients with infected nonunion of tibia treated with an antibiotic spacer combined with Ilizarov methods had a high rate of excellent bone results and a low rate of infection recurrence. Therefore, combining the antibiotic spacer with Ilizarov methods may be an applicable choice for repairing and reconstructing infected nonunion of tibia.

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.

Dstyk mutation leads to congenital scoliosis-like vertebral malformations in zebrafish via dysregulated mTORC1/TFEB pathway.

Congenital scoliosis (CS) is a complex genetic disorder characterized by vertebral malformations. The precise etiology of CS is not fully defined. Here, we identify that mutation in dual serine/threonine and tyrosine protein kinase (dstyk) lead to CS-like vertebral malformations in zebrafish. We demonstrate that the scoliosis in dstyk mutants is related to the wavy and malformed notochord sheath formation and abnormal axial skeleton segmentation due to dysregulated biogenesis of notochord vacuoles and notochord function. Further studies show that DSTYK is located in late endosomal/lysosomal compartments and is involved in the lysosome biogenesis in mammalian cells. Dstyk knockdown inhibits notochord vacuole and lysosome biogenesis through mTORC1-dependent repression of TFEB nuclear translocation. Inhibition of mTORC1 activity can rescue the defect in notochord vacuole biogenesis and scoliosis in dstyk mutants. Together, our findings reveal a key role of DSTYK in notochord vacuole biogenesis, notochord morphogenesis and spine development through mTORC1/TFEB pathway.

Imbalanced development of anterior and posterior thorax is a causative factor triggering scoliosis.

OBJECTIVE: Scoliosis is a common disease characterized by spinal curvature with variable severities. There is no generally accepted theory about the physical origin of the spinal deformation of scoliosis. The aim of this study was to explore a new hypothesis suggesting that the curvatures in scoliosis may be associated with the imbalance growth between thoracic vertebral column and sternum. METHODS: We undertook a comparative computed tomography (CT) based morphology study of thoracic vertebrae and sternum of patients with adolescent idiopathic scoliosis (AIS) and age-gender matched normal subjects. We further measured the ratios between the lengths of the sternum and thoracic vertebra of mice with deficiency of fibroblast growth factor receptor 3 (FGFR3), which exhibit scoliosis. Three-week-old C57BL/6J mice were used to generate bipedal and sternal growth plate injury model. Radiographs and histological images were obtained to observe the presence of sternal and spinal deformity. RESULTS: There was a significant correlation between the severities of scoliosis and the ratios of the sternum to thoracic vertebral lengths. We also found that FGFR3 deficient mice showed smaller ratio of the sternum to thoracic vertebra lengths than that of the wild-type mice, which were similar with that of the AIS patients. Surgery-induced injuries of sternal growth plates can accelerate and aggravate the scoliosis in bipedal mice and imbalanced development of anterior and posterior thoracic occurred before the appearance of scoliosis. CONCLUSIONS: Our findings suggest that the imbalanced growth between the thoracic vertebral column and the sternum is an important causative factor for the pathogenesis of scoliosis including AIS. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: Imbalanced growth between the thoracic vertebral column and the sternum is associated with scoliosis. Surgical or rehabilitation intervention for scoliosis should focus on all components involved in the pathogenesis of curvature to obtain better outcome.

Rmrp Mutation Disrupts Chondrogenesis and Bone Ossification in Zebrafish Model of Cartilage-Hair Hypoplasia via Enhanced Wnt/ß-Catenin Signaling.

Cartilage-hair hypoplasia (CHH) is an autosomal recessive metaphyseal chondrodysplasia characterized by bone dysplasia and many other highly variable features. The gene responsible for CHH is the RNA component of the mitochondrial RNA-processing endoribonuclease (RMRP) gene. Currently, the pathogenesis of osteochondrodysplasia and extraskeletal manifestations in CHH patients remains incompletely understood; in addition, there are no viable animal models for CHH. We generated an rmrp KO zebrafish model to study the developmental mechanisms of CHH. We found that rmrp is required for the patterning and shaping of pharyngeal arches. Rmrp mutation inhibits the intramembranous ossification of skull bones and promotes vertebrae ossification. The abnormalities of endochondral bone ossification are variable, depending on the degree of dysregulated chondrogenesis. Moreover, rmrp mutation inhibits cell proliferation and promotes apoptosis through dysregulating the expressions of cell-cycle- and apoptosis-related genes. We also demonstrate that rmrp mutation upregulates canonical Wnt/ß-catenin signaling; the pharmacological inhibition of Wnt/ß-catenin could partially alleviate the chondrodysplasia and increased vertebrae mineralization in rmrp mutants. Our study, by establishing a novel zebrafish model for CHH, partially reveals the underlying mechanism of CHH, hence deepening our understanding of the role of rmrp in skeleton development.