Elucidating the molecular landscape of tendinitis: the role of inflammasome-related genes and immune interactions.

Tendinitis, characterized by the inflammation of tendons, poses significant challenges in both diagnosis and treatment due to its multifaceted etiology and complex pathophysiology. This study aimed to dissect the molecular mechanisms underlying tendinitis, with a particular focus on inflammasome-related genes and their interactions with the immune system. Through comprehensive gene expression analysis and bioinformatics approaches, we identified distinct expression profiles of inflammasome genes, such as NLRP6, NLRP1, and MEFV, which showed significant correlations with immune checkpoint molecules, indicating a pivotal role in the inflammatory cascade of tendinitis. Additionally, MYD88 and CD36 were found to be closely associated with HLA family molecules, underscoring their involvement in immune response modulation. Contrary to expectations, chemokines exhibited minimal correlation with inflammasome genes, suggesting an unconventional inflammatory pathway in tendinitis. Transcription factors like SP110 and CREB5 emerged as key regulators of inflammasome genes, providing insight into the transcriptional control mechanisms in tendinitis. Furthermore, potential therapeutic targets were identified through the DGidb database, highlighting drugs that could modulate the activity of inflammasome genes, offering new avenues for targeted tendinitis therapy. Our findings elucidate the complex molecular landscape of tendinitis, emphasizing the significant role of inflammasomes and immune interactions, and pave the way for the development of novel diagnostic and therapeutic strategies.

Association between Platelet-Derived Growth Factor Receptor Alpha Gene Polymorphisms and Platelet-Rich Plasma's Efficiency in Treating Lateral Elbow Tendinopathy-A Prospective Cohort Study.

Individual differences in the response to platelet-rich plasma (PRP) therapy can be observed among patients. The genetic background may be the cause of this variability. The current study focused on the impact of genetic variants on the effectiveness of PRP. The aim of the present study was to analyze the impact of single nucleotide polymorphisms (SNP) of the platelet-derived growth factor receptor alpha (PDGFRA) gene on the effectiveness of treating lateral elbow tendinopathy (LET) with PRP. The treatment's efficacy was analyzed over time (2, 4, 8, 12, 24, 52 and 104 weeks after the PRP injection) on 107 patients using patient-reported outcome measures (PROM) and achievement of a minimal clinically important difference (MCID). Four SNPs of the PDGFRA gene (rs7668190, rs6554164, rs869978 and rs1316926) were genotyped using the TaqMan assay method. Patients with the AA genotypes of the rs7668190 and the rs1316926 polymorphisms, as well as carriers of the T allele of rs6554164 showed greater effectiveness of PRP therapy than carriers of other genotypes. Moreover, the studied SNPs influenced the platelets' parameters both in whole blood and in PRP. These results showed that PDGFRA gene polymorphisms affect the effectiveness of PRP treatment. Genotyping the rs6554164 and the rs1316926 SNPs may be considered for use in individualized patient selection for PRP therapy.

MicroRNA-146a gene transfer ameliorates senescence and senescence-associated secretory phenotypes in tendinopathic tenocytes.

OBJECTIVE: Tendinopathy is influenced by multiple factors, including chronic inflammation and aging. Senescent cells exhibit characteristics such as the secretion of matrix-degrading enzymes and pro-inflammatory cytokines, collectively known as senescence-associated secretory phenotypes (SASPs). Many of these SASP cytokines and enzymes are implicated in the pathogenesis of tendinopathy. MicroRNA-146a (miR-146a) blocks senescence by targeting interleukin-1ß (IL-1ß) receptor-associated kinase 4 (IRAK-4) and TNF receptor-associated factor 6 (TRAF6), thus inhibiting NF-κB activity. The aims of this study were to (1) investigate miR-146a expression in tendinopathic tendons and (2) evaluate the role of miR-146a in countering senescence and SASPs in tendinopathic tenocytes. METHODS: MiR-146a expression was assessed in human long head biceps (LHB) and rat tendinopathic tendons by in situ hybridization. MiR-146a over-expression in rat primary tendinopathic tenocytes was achieved by lentiviral vector-mediated precursor miR-146a transfer (LVmiR-146a). Expression of various senescence-related markers was analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunoblotting and immunofluorescence. MiR-146a expression showed a negative correlation with the severity of tendinopathy in human and rat tendinopathic tendons (p<0.001). RESULTS: Tendinopathic tenocyte transfectants overexpressing miR-146a exhibited downregulation of various senescence and SASP markers, as well as the target molecules IRAK-4 and TRAF6, and the inflammatory mediator phospho-NF-κB. Additionally, these cells showed enhanced nuclear staining of high mobility group box 1 (HMGB1) compared to LVmiR-scramble-transduced controls in response to IL-1ß stimulation. CONCLUSIONS: We demonstrate that miR-146a expression is negatively correlated with the progression of tendinopathy. Moreover, its overexpression protects tendinopathic tenocytes from SASPs and senescence through the IRAK-4/TRAF6/NF-kB pathway.

Inhibition of IKKß via a DNA-Based In Situ Delivery System Improves Achilles Tendinopathy Healing in a Rat Model.

BACKGROUND: The inhibition of IKKß by the inhibitor 2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-(4-piperidinyl)-3-pyridine carbonitrile (ACHP) is a promising strategy for the treatment of Achilles tendinopathy. However, the poor water solubility of ACHP severely hinders its in vivo application. Moreover, the effective local delivery of ACHP to the tendon and its therapeutic effects have not been reported. PURPOSE: To investigate the therapeutic effects of IKKß inhibition via injection of ACHP incorporated into a DNA supramolecular hydrogel in a collagenase-induced tendinopathy rat model. STUDY DESIGN: Controlled laboratory study. METHODS: Dendritic DNA, a Y-shaped monomer, and a crosslinking monomer were mixed with ACHP and self-assembled into an ACHP-DNA supramolecular hydrogel (ACHP-Gel). The effects of ACHP-Gel in tendon stem/progenitor cells were investigated via RNA sequencing and validated using quantitative reverse transcription polymerase chain reaction (qRT-PCR). A total of 120 collagenase-induced rats were randomly assigned to 5 groups: blank, phosphate-buffered saline (PBS), DNA-Gel, ACHP, and ACHP-Gel. Healing outcomes were evaluated using biomechanic and histologic evaluations at 4 and 8 weeks. RESULTS: ACHP-Gel enhanced the solubility of ACHP and sustained its release for ≥21 days in vivo, which significantly increased the retention time of ACHP and markedly reduced the frequency of administration. RNA sequencing and qRT-PCR showed that ACHP effectively downregulated genes related to inflammation and extracellular matrix remodeling and upregulated genes related to tenogenic differentiation. The cross-sectional area (P = .024), load to failure (P = .002), stiffness (P = .039), and elastic modulus (P = .048) significantly differed between the ACHP-Gel and PBS groups at 8 weeks. The ACHP-Gel group had better histologic scores than the ACHP group at 4 (P = .042) and 8 weeks (P = .009). Type I collagen expression (COL-I; P = .034) and the COL-I/collagen type III ratio (P = .015) increased while interleukin 6 expression decreased (P < .001) in the ACHP-Gel group compared with the ACHP group at 8 weeks. CONCLUSION: DNA supramolecular hydrogel significantly enhanced the aqueous solubility of ACHP and increased its release-retention time. Injection frequency was markedly reduced. ACHP-Gel suppressed inflammation in Achilles tendinopathy and promoted tendon healing in a rat model. CLINICAL RELEVANCE: ACHP-Gel injection is a promising strategy for the treatment of Achilles tendinopathy in clinical practice.

Computational Analysis of miR-140 and miR-135 as Potential Targets to Develop Combinatorial Therapeutics for Degenerative Tendinopathy.

Background: Degenerative tendinopathy, a condition causing movement restriction due to high pain, highly impacts productivity and quality of life. The healing process is a complex phenomenon and involves a series of intra-cellular and inter-cellular processes. Proliferation and differentiation of the tenocyte is a major and essential process to heal degenerative tendinopathy. The recent development in microRNA (miRNA)-mediated reprogramming of the cellular function through specific pathways opened door for the development of new regenerative therapeutics. Based on information about gene expression and regulation of tendon injury and healing, we attempted to evaluate the combinatorial effect of selected miRNAs for better healing of degenerative tendinopathy. Methods: The present study was designed to evaluate the combinatorial effect of two miRNAs (has-miR-140 and has-miR-135) in the healing process of the tendon. Publicly available information/data were retrieved from appropriate platforms such as PubMed. Only molecular data, directly associated with tendinopathies, including genes/proteins and miRNAs, were used in this study. The miRNAs involved in tendinopathy were analyzed by a Bioinformatics tools (e.g., TargetScan, miRDB, and the RNA22v2). Interactive involvement of the miRNAs with key proteins involved in tendinopathy was predicted by the Insilco approach. Results: Based on information available in the public domain, tendon healing-associated miRNAs were predicted to explore their therapeutic potentials. Based on computation analysis, focusing on the potential regulatory effect on tendon healing, the miR-135 and miR-140 were selected for this study. These miRNAs were found as key players in tendon healing through Rho-associated coiled-coil containing protein kinase 1 (ROCK1), IGF-1/PI3K/Akt, PIN, and Wnt signaling pathways. It was also predicted that these miRNAs may reprogram the cells to induce proliferation and differentiation activity. Many miRNAs are likely to regulate genes important for the tendinopathy healing process, and the result of this study allows an approach for miRNA-mediated regeneration of the tenocyte for tendon healing. Based on computational analysis, the role of these miRNAs in different pathways was established, and the results provided insights into the combinatorial approach of miRNA-mediated cell reprogramming. Conclusions: In this study, the association between miRNAs and the disease was evaluated to correlate the tendinopathy genes and the relevant role of different miRNAs in their regulation. Through this study, it was established that the synergistic effect of more than one miRNA on directed reprogramming of the cell could be helpful in the regeneration of damaged tissue. It is anticipated that this study will be helpful for the design of miRNA cocktails for the orchestration of cellular reprogramming events.

Single-cell and spatial transcriptomics reveal changes in cell heterogeneity during progression of human tendinopathy.

BACKGROUND: Musculoskeletal tissue degeneration impairs the life quality and motor function of many people, especially seniors and athletes. Tendinopathy is one of the most common diseases associated with musculoskeletal tissue degeneration, representing a major global healthcare burden that affects both athletes and the general population, with the clinical presentation of long-term recurring chronic pain and decreased tolerance to activity. The cellular and molecular mechanisms at the basis of the disease process remain elusive. Here, we use a single-cell and spatial RNA sequencing approach to provide a further understanding of cellular heterogeneity and molecular mechanisms underlying tendinopathy progression. RESULTS: To explore the changes in tendon homeostasis during the tendinopathy process, we built a cell atlas of healthy and diseased human tendons using single-cell RNA sequencing of approximately 35,000 cells and explored the variations of cell subtypes' spatial distributions using spatial RNA sequencing. We identified and localized different tenocyte subpopulations in normal and lesioned tendons, found different differentiation trajectories of tendon stem/progenitor cells in normal/diseased tendons, and revealed the spatial location relationship between stromal cells and diseased tenocytes. We deciphered the progression of tendinopathy at a single-cell level, which is characterized by inflammatory infiltration, followed by chondrogenesis and finally endochondral ossification. We found diseased tissue-specific endothelial cell subsets and macrophages as potential therapeutic targets. CONCLUSIONS: This cell atlas provides the molecular foundation for investigating how tendon cell identities, biochemical functions, and interactions contributed to the tendinopathy process. The discoveries revealed the pathogenesis of tendinopathy at single-cell and spatial levels, which is characterized by inflammatory infiltration, followed by chondrogenesis, and finally endochondral ossification. Our results provide new insights into the control of tendinopathy and potential clues to developing novel diagnostic and therapeutic strategies.

Integrative single-cell RNA and ATAC sequencing reveals that the FOXO1-PRDX2-TNF axis regulates tendinopathy.

Introduction: Tendinopathy, the most common form of chronic tendon disorder, leads to persistent tendon pain and loss of function. Profiling the heterogeneous cellular composition in the tendon microenvironment helps to elucidate rational molecular mechanisms of tendinopathy. Methods and results: In this study, through a multi-modal analysis, a single-cell RNA- and ATAC-seq integrated tendinopathy landscape was generated for the first time. We found that a specific cell subpopulation with low PRDX2 expression exhibited a higher level of inflammation, lower proliferation and migration ability, which not only promoted tendon injury but also led to microenvironment deterioration. Mechanistically, a motif enrichment analysis of chromatin accessibility showed that FOXO1 was an upstream regulator of PRDX2 transcription, and we confirmed that functional blockade of FOXO1 activity induced PRDX2 silencing. The TNF signaling pathway was significantly activated in the PRDX2-low group, and TNF inhibition effectively restored diseased cell degradation. Discussion: We revealed an essential role of diseased cells in tendinopathy and proposed the FOXO1-PRDX2-TNF axis is a potential regulatory mechanism for the treatment of tendinopathy.

The Role of Epigenomics in Mapping Potential Precursors for Foot and Ankle Tendinopathy: A Systematic Review.

Tendinopathy of the foot and ankle is a common clinical problem for which the exact etiology is poorly understood. The field of epigenetics has been a recent focus of this investigation. The purpose of this article was to review the genomic advances in foot and ankle tendinopathy that could potentially be used to stratify disease risk and create preventative or therapeutic agents. A multi-database search of PubMed, Cochrane, Google Scholar, and clinicaltrials.gov from January 1, 2000 to July 1, 2022 was performed. A total of 18 articles met inclusion and exclusion criteria for this review. The majority of such research utilized case-control candidate gene association to identify different genetic risk factors associated with chronic tendinopathy. Polymorphisms in collagen genes COL5A1, COL27A1, and COL1A1 were noted at a significantly higher frequency in Achilles tendinopathy versus control groups. Other allelic variations that were observed at an increased incidence in Achilles tendinopathy were TNC and CASP8. The extracellular matrix (ECM) demonstrated macroscopic changes in Achilles tendinopathy, including an increase in aggrecan and biglycan mRNA expression, and increased expression of multiple matrix metalloproteinases. Cytokine expression was also influenced in pathology and aberrantly demonstrated dynamic response to mechanical load. The pathologic accumulation of ECM proteins and cytokine expression alters the adaptive response normal tendon has to physiologic stress, further propagating the risk for tendinopathy. By identifying and understanding the epigenetic mediators that lead to tendinopathy, therapeutic agents can be developed to target the exact underlying etiology and minimize side effects.Level of Evidence: Level IV: Systematic Review of Level II-IV Studies.

Pro-inflammatory activity of long noncoding RNA FOXD2-AS1 in Achilles tendinopathy.

Achilles tendinopathy is a prevalent clinical problem that plagues athletes and general populations. Achilles tendon healing is a complex process, and so far, there is no successful long-term solution to Achilles tendinopathy in the field of microsurgery due to its poor natural regeneration ability. Limitations in understanding the pathogenesis of Achilles tendon development and Achilles tendon injury hinder clinical treatment developments. There is an increasing demand for innovative conservative treatments that can improve Achilles tendon injury. In this study, a Sprague-Dawley rat model of Achilles tendinopathy was established. Lentiviral vectors that interfere with the expression of FOXD2-AS1, miR-21-3p, or PTEN were injected every 3 days. Rats were euthanized after 3 weeks, and the effect of FOXD2-AS1, miR-21-3p, or PTEN on Achilles tendon healing was analyzed by histological observation, biomechanical test, and examinations of inflammatory factors and tendon markers. As measured, downregulating FOXD2-AS1 or upregulating miR-21-3p improved histological structure, suppressed inflammation, promoted the expression of tendon markers, and optimized the biomechanical properties of Achilles tendon. Upregulating PTEN was capable of reversing the promoting effect of inhibition of FOXD2-AS1 on Achilles tendon healing. As concluded, deficiency of FOXD2-AS1 accelerates the healing of Achilles tendon injury and improves tendon degeneration by regulating the miR-21-3p/PTEN axis and promoting the activation of the PI3K/AKT signaling pathway.

Multi-Proteomic Analysis Reveals the Effect of Protein Lactylation on Matrix and Cholesterol Metabolism in Tendinopathy.

Tendinopathy is a disease with surging prevalence. Lacking understanding of molecular mechanisms impedes the development of therapeutic approaches and agents. Lysine lactylation (Kla) is a newly discovered post-translational modification related to glycolysis. It has long been noted that manipulation of glycolysis metabolism could affect tendon cell function, tendon homeostasis, and healing process of tendon. However, protein lactylation sites in tendinopathy remain unexplored. Here, we conducted the first proteome-wide Kla analysis in tendon samples harvested from patients with rotator cuff tendinopathy (RCT), which identified 872 Kla sites across 284 proteins. Compared with normal counterparts, 136 Kla sites on 77 proteins were identified as upregulated in the pathological tendon, while 56 sites on 32 proteins were downregulated. Function enrichment analysis demonstrated that the majority of proteins with upregulated Kla levels functioned in organization of the tendon matrix and cholesterol metabolism, accompanied by lower expression levels which meant impaired cholesterol metabolism and degeneration of the tendon matrix, indicating potential cross-talk between protein lactylation and expression levels. At last, by western blotting and immunofluorescence, we verified the correlation between high lactylation and the downregulation of matrix and cholesterol-related proteins including BGN, MYL3, TPM3, and APOC3. ProteomeXchange: PXD033146.

Application of an in silico approach identifies a genetic locus within ITGB2, and its interactions with HSPG2 and FGF9, to be associated with anterior cruciate ligament rupture risk.

We developed a Biomedical Knowledge Graph model that is phenotype and biological function-aware through integrating knowledge from multiple domains in a Neo4j, graph database. All known human genes were assessed through the model to identify potential new risk genes for anterior cruciate ligament (ACL) ruptures and Achilles tendinopathy (AT). Genes were prioritised and explored in a case-control study comparing participants with ACL ruptures (ACL-R), including a sub-group with non-contact mechanism injuries (ACL-NON), to uninjured control individuals (CON). After gene filtering, 3376 genes, including 411 genes identified through previous whole exome sequencing, were found to be potentially linked to AT and ACL ruptures. Four variants were prioritised: HSPG2:rs2291826A/G, HSPG2:rs2291827G/A, ITGB2:rs2230528C/T and FGF9:rs2274296C/T. The rs2230528 CC genotype was over-represented in the CON group compared to ACL-R (p < 0.001) and ACL-NON (p < 0.001) and the TT genotype and T allele were over-represented in the ACL-R group and ACL-NON compared to CON (p < 0.001) group. Several significant differences in distributions were noted for the gene-gene interactions: (HSPG2:rs2291826, rs2291827 and ITGB2:rs2230528) and (ITGB2:rs2230528 and FGF9:rs2297429). This study substantiates the efficiency of using a prior knowledge-driven in silico approach to identify candidate genes linked to tendon and ACL injuries. Our biomedical knowledge graph identified and, with further testing, highlighted novel associations of the ITGB2 gene which has not been explored in a genetic case control association study, with ACL rupture risk. We thus recommend a multistep approach including bioinformatics in conjunction with next generation sequencing technology to improve the discovery potential of genomics technologies in musculoskeletal soft tissue injuries.HighlightsA biomedical knowledge graph was modelled for musculoskeletal soft tissue injuries to efficiently identify candidate genes for genetic susceptibility analyses.The biomedical knowledge graph and sequencing data identified potential biologically relevant variants to explore susceptibility to common tendon and ligament injuries. Specifically genetic variants within the ITGB2 and FGF9 genes were associated with ACL risk.Novel allele combinations (HSPG2-ITGB2 and ITGB2-FGF9) showcase the potential effect of ITGB2 in influencing risk of ACL rupture.

Association Between COL5a1, COL11a1, and COL11a2 Gene Variations and Rotator Cuff Tendinopathy in Young Athletes.

OBJECTIVE: Tendinopathy is a prevalent condition in young athletes and in older nonathletic people. Recent tendinopathy research has shown a growing interest in the role played by genetic factors, basically genes involved in collagen synthesis and regulation, in view of collagen disorganization typically present in tendon pathologies. DESIGN: A case-control, genotype-phenotype association study. SETTING: La Ribera Hospital, Valencia, Spain. PARTICIPANTS: A group of 137 young athletes (49 with rotator cuff tendon pathology and 88 healthy counterparts) who played upper-limb-loading sports were clinically and ultrasound (US) assessed for rotator cuff tendinopathy were included. INTERVENTION: Genetic analysis was performed to determine whether there was a relationship between rotator cuff pathology and the genotype. MAIN OUTCOME MEASURES: We hypothesized that the following single nucleotide polymorphisms: COL5a1 rs12722, COL11a1 rs3753841, COL11a1 rs1676486, and COL11a2 rs1799907 would be associated with rotator cuff tendinopathy. RESULTS: A direct relationship between CC genotype and bilateral US pathological images was statistically significant (χ 2 = 0.0051) and confirmed by the Fisher test, with a correlation coefficient of 0.345 and a Cramer's v of 0.26. CONCLUSION: A significant association was found between COL5a1 rs12722 genotype and rotator cuff pathology, with the CC genotype conferring increased risk of tendon abnormalities and being associated with rotator cuff pathology.

LncRNA AC108925 promotes osteoblast differentiation of tendon-derived stem cells by targeting miR-146a-3p.

It has been reported that tendon-derived stem cells(TDSCs) conduce to the ostosis in tendon diseases, and the molecular mechanism needs to be discussed. To investigate the function and mechanism of LncRNA in tendinopathy. Tendon of tendinopathy patients and health controls were obtained, and sequencing analysis have been performed to detect the significantly expressed genes and non-coding RNAs. Moreover, to further discuss LncRNA AC108925 in tendinopathy, tendinopathy animal models have been established, and the expression of LncRNA AC108925 expression was examined by RT-qPCR methods. Furthermore, hTDSCs have been treated by osteogenic medium, and the modulating function of LncRNA AC108925 on the osteoblast differentiation of hTDSCs have been examined. Sequencing analysis showed that AC108925 a dramatically elevated LncRNA, and results of animal and cells studies confirmed the finding. Knockdown AC108925 inhibited the osteogenic differentiation of osteogenic medium treated TDSCs by decreasing the expression of osteogenic markers. Furthermore, miR-146a-3p is a target of AC108925 in TDSCs, and miR-146a-3p is a negative modulator of osteogenic differentiation of hTDSCs by inhibiting the effects of AC108925 shRNA on osteogenic differentiation of hTDSCs. AC108925 can regulate the osteogenic differentiation of hTDSCs via regulating the miR-146a-3p. Targeting the AC108925/miR-146a-3p axis might be a latent way to treat tendinopathy.

Causal Associations of Obesity With Achilles Tendinopathy: A Two-Sample Mendelian Randomization Study.

Background: Achilles tendinopathy (AT) is associated with severe pain and is the cause of dysfunction and disability that are associated with significant reduction in social and economic benefits. Several potential risk factors have been proposed to be responsible for AT development; however, the results of observational epidemiological studies remain controversial, presumably because the designs of these studies are subject to residual confounding and reverse causality. Mendelian randomization (MR) can infer the causality between exposure and disease outcomes using genetic variants as instrumental variables, and identification of the causal risk factors for AT is beneficial for early intervention. Thus, we employed the MR strategy to evaluate the causal associations between previously reported risk factors (anthropometric parameters, lifestyle factors, blood biomarkers, and systemic diseases) and the risk of AT. Methods: Univariable MR was performed to screen for potential causal associations between the putative risk factors and AT. Bidirectional MR was used to infer reverse causality. Multivariable MR was conducted to investigate the body mass index (BMI)-independent causal effect of other obesity-related traits, such as the waist-hip ratio, on AT. Results: Univariable MR analyses with the inverse-variance weighted method indicated that the genetically predicted BMI was significantly associated with the risk of AT (P=2.0×10-3), and the odds ratios (95% confidence intervals) is 1.44 (1.14-1.81) per 1-SD increase in BMI. For the other tested risk factors, no causality with AT was identified using any of the MR methods. Bidirectional MR suggested that AT was not causally associated with BMI, and multivariable MR indicated that other anthropometric parameters included in this study were not likely to causally associate with the risk of AT after adjusting for BMI. Conclusions: The causal association between BMI and AT risk suggests that weight control is a promising strategy for preventing AT and alleviating the corresponding disease burden.

Analysis of the lncRNA-Associated Competing Endogenous RNA (ceRNA) Network for Tendinopathy.

Background: We aimed to construct the lncRNA-associated competing endogenous RNA (ceRNA) network and distinguish feature lncRNAs associated with tendinopathy. Methods: We downloaded the gene profile of GSE26051 from the Gene Expression Omnibus (GEO), including 23 normal samples and 23 diseased tendons. Differentially expressed mRNAs (DEmRNAs) and differentially expressed lncRNAs (DElncRNAs) were identified, and functional and pathway enrichment analyses were performed. Protein-protein interaction (PPI) network was constructed and further analyzed by module mining. Moreover, a ceRNA regulatory network was constructed based on the identified lncRNA-mRNA coexpression relationship pairs and miRNA-mRNA regulation pairs. Results: We identified 1117 DEmRNAs and 57 DElncRNAs from the GEO data. The downregulated DEmRNAs were particularly associated with muscle contraction and muscle filament, while the upregulated ones were linked to extracellular matrix organization and cell adhesion. From the PPI network, 11 modules were extracted. Genes in MCODE 2 (such as TPM4) were significantly involved in cardiomyopathy, and genes in MCODE 4 (such as COL4A3 and COL4A4) were involved in focal adhesion, ECM-receptor interaction, and PI3K-Akt signaling pathway. The ceRNA network contained 7 lncRNAs (MIR133A1HG, LINC01405, PRKCQ-AS1, C10orf71-AS1, MBNL1-AS1, HOTAIRM1, and DNM3OS), 63 mRNAs, and 41 miRNAs. Downregulated lncRNA MIR133A1HG could competitively bind with hsa-miR-659-3p and hsa-miR-218-1-3p to regulate the TPM3. Meanwhile, MIR133A1HG could competitively bind with hsa-miR-1179 to regulate the COL4A3. Downregulated C10orf71-AS1 could competitively bind with hsa-miR-130a-5p to regulate the COL4A4. Conclusions: Seven important lncRNAs, particularly MIR133A1HG and C10orf71-AS1, were found associated with tendinopathy according to the lncRNA-associated ceRNA network.

LncRNA MALAT1 promotes tenogenic differentiation of tendon-derived stem cells via regulating the miR-378a-3p/MAPK1 axis.

Tendinopathy is a type of chronic injury caused by repeated pulling. Previous studies have reported that long non-coding RNA MALAT1 (MALAT1) regulates a variety of genes affecting bone metabolism. This study aimed to explore the role of the MALAT1 in tendon injury in vivo and in vitro. Human tendon-derived stem cells (TDSCs) were treated with TGF ß1. Eighteen Sprague-Dawley rats were used to establish the tendinopathy animal model. Sirius Red staining and colorimetric assays were conducted to analyze the collagen content. RT-qPCR was performed to measure the mRNA levels. Western blotting was performed to measure the MAPK1 protein levels. Additionally, hematoxylin and eosin (HE) and immunohistochemical staining were used to analyze the cell number and the content of collagen type 1 and Thbs, respectively. MALAT1 expression was upregulated in TGF ß1 treated TDSCs, and MALAT1 knockdown downregulated Scleraxis, Mohawk homeobox, Collagen 1A1, Fibromodulin, Matrix metallopeptidase 3, and Thrombospondin 4 in TGF ß1 treated TDSCs. Bioinformatics analysis showed that miR-378a-3p was the target of MALAT1 and MAPK1, and dual-luciferase reporter assay indicated that both MALAT1 and MAPK1 could bind to miR-378a-3p. Furthermore, miR-378a-3p knockdown reversed the effect of si-MALAT1, whereas overexpression of MAPK1 reversed the effect of the miR-378a-3p mimic. Finally, MALAT1 expression was downregulated in tendinopathy rats, and MALAT1 overexpression healed tendon injury in them. MALAT1 regulated the tenogenic differentiation of TDSCs by regulating the miR-378a-3p/MAPK1 axis. Our results therefore indicate that targeting the MALAT1/miR-378a-3p/MAPK1 axis may be a promising avenue for the treatment of tendinopathy.

Scleraxis and collagen I expression increase following pilot isometric loading experiments in a rodent model of patellar tendinopathy.

The effect of mechanical load on tendinopathic tissue is usually studied in the context of identifying mechanisms responsible for tendon degradation. However, loading is also one of the most common treatments for tendinopathy. It is therefore possible that different loads result in different cellular responses within a tendon. To test this hypothesis, we first established a rodent model of tendinopathy that has a transcriptional signature similar to human tendinopathy. Tendinopathy was modeled in the rat by producing a lesion in the central core of the patellar tendon using a biopsy punch, followed by two weeks to allow scar formation. We performed 3' Tag RNA-Seq to identify genes that were differentially expressed between the native and scarred rat patellar tendon. Genes involved in extracellular matrix (ECM) structure and turnover were increased, mitochondrial genes were decreased, and there was no inflammatory signature in the tendinopathic tissue. These transcriptional changes phenocopy previously published whole transcriptome analysis in human tendinopathy. After validating the model, the initial response to injury and loading was determined. Two weeks after creation of the patellar tendon lesion, the tendon was loaded using either 4 × 30s isometric or a time-under-tension matched (360 × 0.33s) dynamic protocol. Injured +/- loading and contralateral control tendons were collected eighteen hours after loading, RNA was extracted, and gene expression was quantified using qRT-PCR of the scar with or without loading. The expression of scleraxis and type I collagen increased following isometric loading relative to those loaded dynamically. By contrast, the expression of type II collagen increased in the dynamic samples relative to those loaded isometrically. These data suggest that dynamic loading of a central core tendon injury increases fibrocartilage markers, whereas long isometric loads stimulate markers of tendon regeneration.

Screening of key biomarkers of tendinopathy based on bioinformatics and machine learning algorithms.

Tendinopathy is a complex multifaceted tendinopathy often associated with overuse and with its high prevalence resulting in significant health care costs. At present, the pathogenesis and effective treatment of tendinopathy are still not sufficiently elucidated. The purpose of this research is to intensely explore the genes, functional pathways, and immune infiltration characteristics of the occurrence and development of tendinopathy. The gene expression profile of GSE106292, GSE26051 and GSE167226 are downloaded from GEO (NCBI comprehensive gene expression database) and analyzed by WGCNA software bag using R software, GSE26051, GSE167226 data set is combined to screen the differential gene analysis. We subsequently performed gene enrichment analysis of Gene Ontology (GO) and "Kyoto Encyclopedia of Genes and Genomes" (KEGG), and immune cell infiltration analysis. By constructing the LASSO regression model, Support vector machine (SVM-REF) and Gaussian mixture model (GMMs) algorithms are used to screen, to identify early diagnostic genes. We have obtained a total of 171 DEGs through WGCNA analysis and differentially expressed genes (DEGs) screening. By GO and KEGG enrichment analysis, it is found that these dysregulated genes were related to mTOR, HIF-1, MAPK, NF-κB and VEGF signaling pathways. Immune infiltration analysis showed that M1 macrophages, activated mast cells and activated NK cells had infiltration significance. After analysis of THE LASSO SVM-REF and GMMs algorithms, we found that the gene MACROD1 may be a gene for early diagnosis. We identified the potential of tendon disease early diagnosis way and immune gene regulation MACROD1 key infiltration characteristics based on comprehensive bioinformatics analysis. These hub genes and functional pathways may as early biomarkers of tendon injuries and molecular therapy level target is used to guide drug and basic research.

Single-cell transcriptomic profiling reveals distinct mechanical responses between normal and diseased tendon progenitor cells.

Regenerative medicine approaches utilizing stem cells offer a promising strategy to address tendinopathy, a class of common tendon disorders associated with pain and impaired function. Tendon progenitor cells (TPCs) are important in healing and maintaining tendon tissues. Here we provide a comprehensive single cell transcriptomic profiling of TPCs from three normal and three clinically classified tendinopathy samples in response to mechanical stimuli. Analysis reveals seven distinct TPC subpopulations including subsets that are responsive to the mechanical stress, highly clonogenic, and specialized in cytokine or growth factor expression. The single cell transcriptomic profiling of TPCs and their subsets serves as a foundation for further investigation into the pathology and molecular hallmarks of tendinopathy in mechanical stimulation conditions.

Association of COA1 with Patellar Tendonitis: A Genome-wide Association Analysis.

PURPOSE: It is unknown why some athletes develop patellar tendinopathy and others do not, even when accounting for similar workloads between individuals. Genetic differences between these two populations may be a contributing factor. The purpose of this work was to screen the entire genome for genetic markers associated with patellar tendinopathy. METHODS: Genome-wide association (GWA) analyses were performed utilizing data from the Kaiser Permanente Research Board (KPRB) and the UK Biobank. Patellar tendinopathy cases were identified based on electronic health records from KPRB and UK Biobank. GWA analyses from both cohorts were tested for patellar tendinopathy using a logistic regression model adjusting for sex, height, weight, age, and race/ethnicity using allele counts for single nucleotide polymorphisms. The data from the two GWA studies (KPRB and UK Biobank) were combined in a meta-analysis. RESULTS: There were a total of 1670 cases of patellar tendinopathy and 293,866 controls within the two cohorts. Two single nucleotide polymorphisms located in the intron of the cytochrome c oxidase assembly factor 1 (COA1) gene showed a genome-wide significant association in the meta-analysis. CONCLUSIONS: Genetic markers in COA1 seem to be associated with patellar tendinopathy and are potential risk factors for patellar tendinopathy that deserve further validation regarding molecular mechanisms.