TUFT1, a novel candidate gene for metatarsophalangeal osteoarthritis, plays a role in chondrogenesis on a calcium-related pathway

PIEZO1 variants that reduce open channel probability are associated with familial osteoarthritis

The synovial joints senses and responds to a multitude of physical forces to maintain joint homeostasis. Disruption of joint homeostasis results in development of osteoarthritis (OA), a disease characterized by loss of joint space, degeneration of articular cartilage, remodeling of bone and other joint tissues, low-grade inflammation, and pain. How changes in mechanosensing in the joint contribute to OA susceptibility remains elusive. PIEZO1 is a major mechanosensitive cation channel in the joint directly regulated by mechanical stimulus. To test whether altered PIEZO1 channel activity causes increased OA susceptibility, we determined whether variants affecting PIEZO1 are associated with dominant inheritance of age-associated familial OA. We identified four rare coding variants affecting PIEZO1 that are associated with familial hand OA. Single channel analyses demonstrated that all four PIEZO1 mutant channels act in a dominant-negative manner to reduce the open probability of the channel in response to pressure. Furthermore, we show that a GWAS mutation in PIEZO1 associated with reduced joint replacement results in increased channel activity when compared with WT and the mutants. Our data support the hypothesis that reduced PIEZO1 activity confers susceptibility to age-associated OA whereas increased PIEZO1 activity may be associated with reduced OA susceptibility.

Sirt5 regulates chondrocyte metabolism and osteoarthritis development through protein lysine malonylation

Objectives

Chondrocyte metabolic dysfunction plays an important role in osteoarthritis (OA) development during aging and obesity. Protein post-translational modifications (PTMs) have recently emerged as an important regulator of cellular metabolism. We aim to study one type of PTM, lysine malonylation (MaK) and its regulator Sirt5 in OA development.

Methods

Human and mouse cartilage tissues were used to measure SIRT5 and MaK levels. Both systemic and cartilage-specific conditional knockout mouse models were subject to high-fat diet (HFD) treatment to induce obesity and OA. Proteomics analysis was performed in Sirt5 -/- and WT chondrocytes. SIRT5 mutation was identified in the Utah Population Database (UPDB).

Results

We found that SIRT5 decreases while MAK increases in the cartilage during aging. A combination of Sirt5 deficiency and obesity exacerbates joint degeneration in a sex dependent manner in mice. We further delineate the malonylome in chondrocytes, pinpointing MaK's predominant impact on various metabolic pathways such as carbon metabolism and glycolysis. Lastly, we identified a rare coding mutation in SIRT5 that dominantly segregates in a family with OA. The mutation results in substitution of an evolutionally invariant phenylalanine (Phe-F) to leucine (Leu-L) (F101L) in the catalytic domain. The mutant protein results in higher MaK level and decreased expression of cartilage ECM genes and upregulation of inflammation associated genes.

Conclusions

We found that Sirt5 mediated MaK is an important regulator of chondrocyte cellular metabolism and dysregulation of Sirt5-MaK could be an important mechanism underlying aging and obesity associated OA development.

Disruption of TUFT1, a Desmosome-Associated Protein, Causes Skin Fragility, Woolly Hair, and Palmoplantar Keratoderma

Desmosomes are dynamic complex protein structures involved in cellular adhesion. Disruption of these structures by loss-of-function variants in desmosomal genes leads to a variety of skin- and heart-related phenotypes. In this study, we report TUFT1 as a desmosome-associated protein, implicated in epidermal integrity. In two siblings with mild skin fragility, woolly hair, and mild palmoplantar keratoderma but without a cardiac phenotype, we identified a homozygous splice-site variant in the TUFT1 gene, leading to aberrant mRNA splicing and loss of TUFT1 protein. Patients' skin and keratinocytes showed acantholysis, perinuclear retraction of intermediate filaments, and reduced mechanical stress resistance. Immunolabeling and transfection studies showed that TUFT1 is positioned within the desmosome and that its location is dependent on the presence of the desmoplakin carboxy-terminal tail. A Tuft1-knockout mouse model mimicked the patients' phenotypes. Altogether, this study reveals TUFT1 as a desmosome-associated protein, whose absence causes skin fragility, woolly hair, and palmoplantar keratoderma.

Biallelic TUFT1 variants cause woolly hair, superficial skin fragility and desmosomal defects

BACKGROUND

Desmosomes are complex cell junction structures that connect intermediate filaments providing strong cell-to-cell adhesion in tissues exposed to mechanical stress.

OBJECTIVES

To identify causal variants in individuals with woolly hair and skin fragility of unknown genetic cause.

METHODS

This research was conducted using whole-genome sequencing, whole-exome sequencing, clinical phenotyping, haplotype analysis, single-cell RNA sequencing data analysis, immunofluorescence microscopy and transmission electron microscopy.

RESULTS

We identified homozygous predicted loss-of-function tuftelin-1 (TUFT1) variants in nine individuals, from three families, with woolly hair and skin fragility. One donor splice-site variant, c.60+1G>A, was present in two families, while a frameshift variant, p.Gln189Asnfs*49, was found in the third family. Haplotype analysis showed the c.60+1G>A substitution to be a founder variant in the Irish population that likely arose approximately 20 generations ago. Human and mouse single-cell RNA sequencing data showed TUFT1 expression to be enriched in the hair dermal sheath and keratinocytes. TUFT1 expression was highly correlated with genes encoding desmosomal components implicated in diseases with phenotypes that overlap with the cohort presented here. Immunofluorescence showed tuftelin-1 to be mainly localized to the peripheral cell membranes of keratinocytes in normal skin. Skin samples from individuals with TUFT1 variants showed markedly reduced immunoreactivity for tuftelin-1, with a loss of the keratinocyte cell membrane labelling. Light microscopy revealed keratinocyte adhesion, mild hyperkeratosis and areas of superficial peeling. Transmission electron microscopy showed panepidermal acantholysis with widening of intercellular spaces throughout the epidermis and desmosomal detachment through the inner plaques.

CONCLUSIONS

Biallelic loss-of-function TUFT1 variants cause a new autosomal recessive skin/hair disorder characterized by woolly hair texture and early-onset skin fragility. Tuftelin-1 has a role in desmosomal integrity and function.

Summary Report of the Arthritis Foundation and the American Orthopaedic Foot & Ankle Society's Symposium on Targets for Osteoarthritis Research: Part 1: Epidemiology, Pathophysiology, and Current Imaging Approaches

This first of a 2-part series of articles recounts the key points presented in a collaborative symposium sponsored jointly by the Arthritis Foundation and the American Orthopaedic Foot & Ankle Society with the intent to survey the state of scientific knowledge related to incidence, diagnosis, pathologic mechanisms, and injection treatment options for osteoarthritis (OA) of the foot and ankle. A meeting was held virtually on December 3, 2021. A group of experts were invited to present brief synopses of the current state of knowledge and research in this area. Part 1 overviews areas of epidemiology and pathophysiology, current approaches in imaging, diagnostic and therapeutic injections, and genetics. Opportunities for future research are discussed. The OA scientific community, including funding agencies, academia, industry, and regulatory agencies, must recognize the needs of patients that suffer from arthritis of foot and ankle. The foot and ankle contain a myriad of interrelated joints and tissues that together provide a critical functionality. When this functionality is compromised by OA, significant disability results, yet the foot and ankle are generally understudied by the research community. Level of Evidence: Level V - Review Article/Expert Opinion.

Familial Clustering and Genetic Analysis of Severe Thumb Carpometacarpal Joint Osteoarthritis in a Large Statewide Cohort

PURPOSE

Our goals were to identify individuals who required surgery for thumb carpometacarpal (CMC) joint osteoarthritis (OA), determine if CMC joint OA clusters in families, define the magnitude of familial risk of CMC joint OA, identify risk factors associated with CMC joint OA, and identify rare genetic variants that segregate with familial CMC joint OA.

METHODS

We searched the Utah Population Database to identify a cohort of CMC joint OA patients who required surgery. Affected individuals were mapped to pedigrees to identify high-risk families with excess clustering of CMC joint OA. Cox regression models were used to calculate familial risk of CMC joint OA in related individuals. Risk factors were evaluated using logistic regression models. Whole exome sequencing was used to identify rare coding variants associated with familial CMC joint OA.

RESULTS

We identified 550 pedigrees with excess clustering of severe CMC joint OA. The relative risk of CMC joint OA requiring surgical treatment was elevated significantly in first- and third-degree relatives of affected individuals, and significant associations with advanced age, female sex, obesity, and tobacco use were observed. We discovered candidate genes that dominantly segregate with severe CMC joint OA in 4 independent families, including a rare variant in Chondroitin Sulfate Synthase 3 (CHSY3).

CONCLUSIONS

Familial clustering of severe CMC joint OA was observed in a statewide population. Our data indicate that genetic and environmental factors contribute to the disease process, further highlighting the multifactorial nature of the disease. Genomic analyses suggest distinct biological processes are involved in CMC joint OA pathogenesis.

CLINICAL RELEVANCE

Awareness of associated comorbidities may guide the diagnosis of CMC joint OA in at-risk populations and help identify individuals who may not do well with nonoperative treatment. Further pursuit of the genes associated with severe CMC joint OA may lead to assays for detection of early stages of disease and have therapeutic potential.

NOD/RIPK2 signalling pathway contributes to osteoarthritis susceptibility

OBJECTIVES

How inflammatory signalling contributes to osteoarthritis (OA) susceptibility is undetermined. An allele encoding a hyperactive form of the Receptor Interacting Protein Kinase 2 (RIPK2) proinflammatory signalling intermediate has been associated with familial OA. To test whether altered nucleotide-binding oligomerisation domain (NOD)/RIPK2 pathway activity causes heightened OA susceptibility, we investigated whether variants affecting additional pathway components are associated with familial OA. To determine whether the Ripk2104Asp disease allele is sufficient to account for the familial phenotype, we determined the effect of the allele on mice.

METHODS

Genomic analysis of 150 independent families with dominant inheritance of OA affecting diverse joints was used to identify coding variants that segregated strictly with occurrence of OA. Genome editing was used to introduce the OA-associated RIPK2 (p.Asn104Asp) allele into the genome of inbred mice. The consequences of the Ripk2104Asp disease allele on physiology and OA susceptibility in mice were measured by histology, immunohistochemistry, serum cytokine levels and gene expression.

RESULTS

We identified six novel variants affecting components of the NOD/RIPK2 inflammatory signalling pathway that are associated with familial OA affecting the hand, shoulder or foot. The Ripk2104Asp allele acts dominantly to alter basal physiology and response to trauma in the mouse knee. Whereas the knees of uninjured Ripk2Asp104 mice appear normal histologically, the joints exhibit a set of marked gene expression changes reminiscent of overt OA. Although the Ripk2104Asp mice lack evidence of chronically elevated systemic inflammation, they do exhibit significantly increased susceptibility to post-traumatic OA (PTOA).

CONCLUSIONS

Two types of data support the hypothesis that altered NOD/RIPK2 signalling confers susceptibility to OA.

Roles of the calcified cartilage layer and its tissue engineering reconstruction in osteoarthritis treatment

Sandwiched between articular cartilage and subchondral bone, the calcified cartilage layer (CCL) takes on both biomechanical and biochemical functions in joint development and ordinary activities. The formation of CCL is not only unique in articular cartilage but can also be found in the chondro-osseous junction adjacent to the growth plate during adolescence. The formation of CCL is an active process under both cellular regulation and intercellular communication. Abnormal alterations of CCL can be indications of degenerative diseases including osteoarthritis. Owing to the limited self-repair capability of articular cartilage and core status of CCL in microenvironment maintenance, tissue engineering reconstruction of CCL in damaged cartilage can be of great significance. This review focuses on possible tissue engineering reconstruction methods targeting CCL for further OA treatment.

Understanding Musculoskeletal Disorders Through Next-Generation Sequencing

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An insight into musculoskeletal disorders through advancements in next-generation sequencing (NGS) promises to maximize benefits and improve outcomes through improved genetic diagnosis.

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The primary use of whole exome sequencing (WES) for musculoskeletal disorders is to identify functionally relevant variants.

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The current evidence has shown the superiority of NGS over conventional genotyping for identifying novel and rare genetic variants in patients with musculoskeletal disorders, due to its high throughput and low cost.

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Genes identified in patients with scoliosis, osteoporosis, osteoarthritis, and osteogenesis imperfecta using NGS technologies are listed for further reference.

Description of Joint Alterations Observed in a Family Carrying p.Asn453Ser COMP Variant: Clinical Phenotypes, In Silico Prediction of Functional Impact on COMP Protein and Stability, and Review of the Literature

The role of genetics in the development of osteoarthritis is well established but the molecular bases are not fully understood. Here, we describe a family carrying a germline mutation in COMP (Cartilage Oligomeric Matrix Protein) associated with three distinct phenotypes. The index case was enrolled for a familial form of idiopathic early-onset osteoarthritis. By screening potential causal genes for osteoarthritis, we identified a heterozygous missense mutation of COMP (c.1358C>T, p.Asn453Ser), absent from genome databases, located on a highly conserved residue and predicted to be deleterious. Molecular dynamics simulation suggests that the mutation destabilizes the overall COMP protein structure and consequently the calcium releases from neighboring calcium binding sites. This mutation was once reported in the literature as causal for severe multiple epiphyseal dysplasia (MED). However, no sign of dysplasia was present in the index case. The mutation was also identified in one of her brothers diagnosed with MED and secondary osteoarthritis, and in her sister affected by an atypical syndrome including peripheral inflammatory arthritis of unknown cause, without osteoarthritis nor dysplasia. This article suggests that this mutation of COMP is not only causal for idiopathic early-onset osteoarthritis or severe MED, but can also be associated to a broad phenotypic variability with always joint alterations.

Tuftelin 1 (TUFT1) Promotes the Proliferation and Migration of Renal Cell Carcinoma via PI3K/AKT Signaling Pathway

Tuftelin 1 (TUFT1), a protein functioning distinctively in different tissues, is reported to be elevated in several types of cancers and the elevation of TUFT1 is correlated with unfavorable clinicopathologic characteristics and poor survival. However, the involvement of TUFT1 in renal cell carcinoma (RCC) remains unknown. In the current study, we investigated the role of TUFT1 in RCC and potential underlying mechanisms. RT-PCR and Western blot analysis showed that both the mRNA and protein levels of TUFT1 were increased in primary RCC tissue and RCC cell lines. TUFT1 overexpression in RCC cells resulted in enhanced cell proliferation and migration while knockdown of TUFT1 by contrast decreased the growth and migration of the RCC cells, indicating TUFT1 expression is involved in RCC cell growth and migration. The involvement of TUFT1 in the epithelial-mesenchymal transition (EMT) of RCC cells was also determined by measuring the expression of EMT-related markers. Our data showed that TUFT1 overexpression promoted RCC cell EMT progression while knockdown of TUFT1 suppressed such process. Further signaling pathway inhibition assay revealed that TUFT1-induced RCC cell growth, migration and EMT was significantly suppressed by PI3K inhibitor, but not JNK or MEK inhibitors. In addition, TUFT1 overexpression enhanced the AKT phosphorylation, a key member of the PI3K signaling pathway, while PI3K inhibitor suppressed such process. Taken together, our study showed that TUFT1 expression was elevated in RCC and such elevation promoted the proliferation, migration and EMT of RCC cells in vitro, through PI3K/AKT signaling pathway. The findings of our current study imply that TUFT1 is involved in RCC tumorigenesis, and it may serve as a biomarker for RCC diagnosis and a potential target for RCC treatment.

Familial Clustering of Erosive Hand Osteoarthritis in a Large Statewide Cohort

OBJECTIVE

Erosive hand osteoarthritis (OA) is a severe and rapidly progressing subset of hand OA. Its etiology remains largely unknown, which has hindered development of successful treatments. This study was undertaken to test the hypothesis that erosive hand OA demonstrates familial clustering in a large statewide population linked to genealogical records, and to determine the association of potential risk factors with erosive hand OA.

METHODS

Patients diagnosed as having erosive hand OA were identified by searching 4,741,840 unique medical records from a comprehensive statewide database, the Utah Population Database (UPDB). Affected individuals were mapped to pedigrees to identify high-risk families with excess clustering of erosive hand OA as defined by a familial standardized incidence ratio (FSIR) of ≥2.0. The magnitude of familial risk of erosive hand OA in related individuals was calculated using Cox regression models. Association of potential erosive hand OA risk factors was analyzed using multivariate conditional logistic regression and logistic regression models.

RESULTS

We identified 703 affected individuals linked to 240 unrelated high-risk pedigrees with excess clustering of erosive hand OA (FSIR ≥2.0, P < 0.05). The relative risk of developing erosive hand OA was significantly elevated in first-degree relatives (P < 0.001). There were significant associations between a diagnosis of erosive hand OA and age, sex, diabetes, and obesity (all P < 0.05).

CONCLUSION

Familial clustering of erosive hand OA observed in a statewide database indicates a potential genetic contribution to the etiology of the disease. Age, sex, diabetes, and obesity are risk factors for erosive hand OA. Identification of causal gene variants in these high-risk families may provide insight into the genes and pathways that contribute to erosive hand OA onset and progression.

Identification of key genes in osteoarthritis using bioinformatics, principal component analysis and meta-analysis

The present study aimed to identify key genes involved in osteoarthritis (OA). Based on a bioinformatics analysis of five gene expression profiling datasets (GSE55457, GSE55235, GSE82107, GSE12021 and GSE1919), differentially expressed genes (DEGs) in OA were identified. Subsequently, a protein-protein interaction (PPI) network was constructed and its topological structure was analyzed. In addition, key genes in OA were identified following a principal component analysis (PCA) based on the DEGs in the PPI network. Finally, the functions and pathways enriched by these key genes were also analyzed. The PPI network consisted of 241 nodes and 576 interactives, including a total of 171 upregulated DEGs [e.g., aspartylglucosaminidase (AGA), CD58 and CD86] and a total of 70 downregulated DEGs (e.g., acetyl-CoA carboxylase β and dihydropyrimidine dehydrogenase). The PPI network complied with an attribute of scale-free small-world network. After PCA, 47 key genes were identified, including β-1,4-galactosyltransferase-1 (B4GALT1), AGA, CD58, CD86, ezrin, and eukaryotic translation initiation factor 4 γ 1 (EIF4G1). Subsequently, the 47 key genes were identified to be enriched in 13 Gene Ontology (GO) terms and 2 Kyoto Encyclopedia of Genes and Genomes pathways, with the GO terms involving B4GALT1 including positive regulation of developmental processes, protein amino acid terminal glycosylation and protein amino acid terminal N-glycosylation. In addition, B4GALT1 and EIF4G1 were confirmed to be downregulated in OA samples compared with healthy controls, but only EIF4G1 was determined to be significantly downregulated in OA samples, as determined via a meta-analysis of the 5 abovementioned datasets. In conclusion, B4GALT1 and EIF4G1 were indicated to have significant roles in OA, and B4GALT1 may be involved in positive regulation of developmental processes, protein amino acid terminal glycosylation and protein amino acid terminal N-glycosylation. The present study may enhance the current understanding of the molecular mechanisms of OA and provide novel therapeutic targets.

Clinical and Molecular Spectrum of Nonsyndromic Early-Onset Osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is the most common joint disease worldwide. The etiology of OA is varied, ranging from multifactorial to environmental to monogenic. In a condition called early-onset OA, OA occurs at an earlier age than is typical in the general population. To our knowledge, there have been no large-scale genetic studies of individuals with early-onset OA. The present study was undertaken to investigate causes of monogenic OA in individuals with nonsyndromic early-onset OA.

METHODS

The study probands were 45 patients with nonsyndromic early-onset OA who were referred to our skeletal disease center by skeletal dysplasia experts between 2013 and 2019. Criteria for early-onset OA included radiographic evidence, body mass index ≤30 kg/m² , age at onset ≤50 years, and involvement of ≥1 joint site. Molecular analysis was performed with a next-generation sequencing panel.

RESULTS

We identified a genetic variant in 13 probands (29%); the affected gene was COL2A1 in 11, ACAN in 1, and SLC26A2 in 1. After familial segregation analysis, 20 additional individuals were identified. The mean ± SD age at onset of joint pain was 19.5 ± 3.9 years (95% confidence interval 3-47). Eighteen of 33 subjects (55%) with nonsyndromic early-onset OA and a genetic variant had had at least 1 joint replacement (mean ± SD age at first joint replacement 41 ± 4.2 years; mean number of joint replacements 2.6 per individual), and 21 (45%) of the joint replacement surgeries were performed when the patient was <45 years old. Of the 20 patients age >40 years, 17 (85%) had had at least 1 joint replacement.

CONCLUSION

We confirmed that COL2A1 is the main monogenic cause of nonsyndromic early-onset OA. However, on the basis of genetic heterogeneity of early-onset OA, we recommend next-generation sequencing for all individuals who undergo joint replacement prior to the age of 45 years. Lifestyle recommendations for prevention should be implemented.

Tuftelin and HIFs expression in osteogenesis

Tuftelin was originally discovered and mostly studied in the tooth, but later found also in other organs. Despite its wide distribution among tissues, tuftelin's function has so far been specified only in the formation of enamel crystals. Nevertheless, in many cases, tuftelin was suggested to be associated with cellular adaptation to hypoxia and recently even with cell differentiation. Therefore, we aimed to investigate tuftelin expression along with hypoxia-inducible factors (HIFs) during the early development of the mandibular/alveolar (m/a) bone, when osteoblasts started to differentiate in vivo and to compare their expression levels in undifferentiated versus differentiated osteoblastic cells in vitro. Immunohistochemistry demonstrated the presence of tuftelin already in osteoblastic precursors which were also HIF1-positive, but HIF2-negative. Nevertheless, HIF2 protein appeared when osteoblasts differentiated, one day later. This is in agreement with observations made with MC3T3-E1 cells, where there was no significant difference in tuftelin and Hif1 expression in undifferentiated vs. differentiated cells, although Hif2 increased upon differentiation induction. In differentiated osteoblasts of the m/a bone, all three proteins accumulated, first, prenatally, in the cytoplasm and later, particularly at postnatal stages, they displayed also peri/nuclear localization. Such a dynamic time-space pattern of tuftelin expression has recently been reported in neurons, which, as the m/a bone, differentiate under less hypoxic conditions as indicated also by a prevalent cytoplasmic expression of HIF1 in osteoblasts. However, unlike what was shown in cultured neurons, tuftelin does not seem to participate in final osteoblastic differentiation and its functions, thus, appears to be tissue specific.

A hyperactivating proinflammatory RIPK2 allele associated with early-onset osteoarthritis

Osteoarthritis (OA) is a common debilitating disease characterized by abnormal remodeling of the cartilage and bone of the articular joint. Ameliorating therapeutics are lacking due to limited understanding of the molecular pathways affecting disease initiation and progression. Notably, although a link between inflammation and overt OA is well established, the role of inflammation as a driver of disease occurrence is highly disputed. We analyzed a family with dominant inheritance of early-onset OA and found that affected individuals harbored a rare variant allele encoding a significant amino acid change (p.Asn104Asp) in the kinase domain of receptor interacting protein kinase 2 (RIPK2), which transduces signals from activated bacterial peptidoglycan sensors through the NF-κB pathway to generate a proinflammatory immune response. Functional analyses of RIPK2 activity in zebrafish embryos indicated that the variant RIPK2104Asp protein is hyperactive in its signaling capacity, with augmented ability to activate the innate immune response and the NF-κB pathway and to promote upregulation of OA-associated genes. Further we show a second allele of RIPK2 linked to an inflammatory disease associated with arthritis also has enhanced activity stimulating the NF-κB pathway. Our studies reveal for the first time the inflammatory response can function as a gatekeeper risk factor for OA.

Tuft1 promotes thyroid carcinoma cell invasion and proliferation and suppresses apoptosis through the Akt-mTOR/GSK3β signaling pathway

In this study, we aimed to investigate the biological functions of Tuftelin 1 (Tuft1) in thyroid carcinoma (TC) and determine its underlying molecular mechanism. We found that the expression of Tuft1 was significantly upregulated in TC tissues. Using TC tissue microarrays (n = 154), we found that Tuft1 expression was closely related with the overall survival (OS) and disease-free survival (DFS) of TC patients. Knockdown of Tuft1 in TPC-1 and SW579 cells suppressed the invasion and proliferation of TC cells and increased the apoptosis of TC cells. In vivo, knockdown of Tuft1 attenuated tumor growth and suppressed the phosphorylation of Akt, mTOR, and GSK3β signaling. Addition of recombinant Tuft1 protein (rTuft1) to TC cells increased the phosphorylation of Akt, mTOR, and GSK3β signaling. An mTOR inhibitor (Dactolisib) abrogated rTuft1 protein-induced TC cell invasion, proliferation, and apoptosis inhibition, whereas a GSK3β inhibitor (CHIR-98014) only abrogated rTuft1 protein-induced proliferation and apoptosis inhibition. These results suggest that Tuft1 promotes TC cell invasion and proliferation, and suppresses apoptosis through the Akt-mTOR or Akt-GSK3β signaling pathway. In the future, Tuft1 may serve as a potential therapeutic target for TC.

TUFT1 Promotes Osteosarcoma Cell Proliferation and Predicts Poor Prognosis in Osteosarcoma Patients

Objective

This study is aimed at exploring the role of TUFT1 in osteosarcomas.

Methods

We investigated the expression of TUFT1 in osteosarcoma cell lines and explored the correlation between TUFT1 expression and prognosis in osteosarcoma patients based on the expression data downloaded from Gene Expression Omnibus (GEO) website. The effects of TUFT1 on osteosarcoma cell proliferation, migration and invasion were investigated by silencing TUFT1 in osteosarcoma MG63 cell line. Finally, western blot was performed to determine the expression changes of MAPK signaling pathway related proteins after silencing TUFT1.

Results

We found that the expression of TUFT1 was significantly up-regulated in osteosarcoma cell lines compared with the normal control. Using Kaplan-Meier analysis, we identified that high TUFT1 expression was positively correlated with poor prognosis in osteosarcoma patients. Furthermore, knockdown of TUFT1 remarkably inhibited MG63 cell proliferation, migration and invasion. Using western blot analysis, we found that the phosphorylation levels of MEK and ERK were reduced obviously in MG63 cells after silencing TUFT1 (p<0.01).

Conclusions

Our results demonstrated that TUFT1 plays a promoting role in MG63 cell proliferation and metastasis and has the potential to be a predictor as well as a therapeutic target for osteosarcoma patients.

Hypoxia-induced TUFT1 promotes the growth and metastasis of hepatocellular carcinoma by activating the Ca2+/PI3K/AKT pathway

Tuftelin1 (TUFT1), an acidic protein constituent of developing and mineralizing tooth tissues, is regulated by hypoxia and the Hedgehog signaling pathway. We investigated the role of TUFT1 in hepatocellular carcinoma (HCC). qRT-PCR, immunohistochemistry and western blot were employed to evaluate TUFT1 level in HCC. MTT, BrdU, 3D culture and Transwell assays were used to assess cell viability, proliferation, in vitro growth, migration, and invasion. Subcutaneous and tail vein injection models were established to investigate in vivo growth and metastasis. Chromatin immunoprecipitation was performed to assess binding of hypoxia-inducible factor 1α (HIF-1α) to TUFT1 promoter. A microRNA array was used to identify hypoxia-related microRNAs. TUFT1 was elevated in HCC, and correlated with unfavorable clinicopathologic characteristics and poor survival. TUFT1 promoted HCC cell growth, metastasis and epithelial-mesenchymal transition in vitro and in vivo via activation of Ca²⁺/PI3K/AKT pathway. Hypoxia induced TUFT1 expression in an HIF-1α dependent manner, and TUFT1 expression was positively correlated with HIF-1α level in HCC tissues. Hypoxiaenhanced TUFT1 expression by downregulating miR-671-5p rather than by directly promoting the binding of HIF-1α to TUFT1 promoter. MiR-671-5p interacted with the 3'-UTR of TUFT1 mRNA and subsequently inhibited TUFT1 expression. Consequently, knockdown of TUFT1 blocked the effects of hypoxia in promoting HCC progression. TUFT1 promoted the growth, metastasis and EMT of HCC cells through activating Ca²⁺/PI3K/AKT pathway. The hypoxic microenvironment increased the expression of TUFT1 via downregulation of miR-671-5p. TUFT1 may function as a potential therapeutic target for the intervention and treatment of HCC.

A novel role in skeletal segment regeneration of extracellular vesicles released from periodontal-ligament stem cells

Purpose

The combination of oral derived stem cells and 3-D scaffolds is considered advantageous in bone repair. In particular, collagen membranes possess ideal biological properties and can support infiltration and proliferation of osteoblasts, promoting bone regeneration. Our study aimed to develop a new biocompatible osteogenic construct composed of a commercially available collagen membrane (Evolution [Evo]), human periodontal-ligament stem cells (hPDLSCs) enriched with extracellular vesicles (EVs), or polyethylenimine (PEI)-engineered EVs (PEI-EVs).

Methods

Osteogenic ability and expression of osteogenic genes were evaluated in vitro in hPDLSCs cultured with or without Evo, with Evo and EVs, or PEI-EVs. In addition, the bone-regeneration capacity of Evo, Evo enriched with hPDLSCs, Evo enriched with hPDLSCs and EVs/PEI-EVs was investigated in rats subjected to calvarial defects.

Results

Our results showed that Evo enriched with EVs and PEI-EVs showed high biocompatibility and osteogenic properties in vitro and in vivo. In addition, quantitative reverse-transcription polymerase chain reaction demonstrated the upregulation of osteogenic genes, such as TGFB1, MMP8, TUFT1, TFIP11, BMP2, and BMP4, in the presence of PEI-EVs. Upregulation of BMP2/4 was confirmed for Evo enriched with PEI-EVs and hPDLSCs both in vitro by Western blot and in vivo by immunofluorescence.

Conclusion

Our results indicated that Evo enriched with hPDLSCs and PEI-EVs is able to promote a bone-regeneration process for the treatment of calvarium and ossification defects caused by accidental or surgery trauma. In particular, PEI-EVs had a significant role in activation of the osteogenic process.

Effects of oral glucosamine hydrochloride and mucopolysaccharide protein in a rabbit model of osteoarthritis

AIM

The aim was to study whether oral glucosamine hydrochloride (GlcN.HCl) or mucopolysaccharide protein (MucoP) has a structure-modifying effect on an anterior cruciate ligament transection (ACLT) rabbit model of osteoarthritis (OA).

METHODS

OA was surgically induced in the right knees of rabbits by transection of the ACLT. The left knees served as a sham-operated control. The animals were divided into four groups (n = 6 each): negative control (phosphate buffered saline, orally), positive control (oral celecoxib 10 mg/kg body weight/day), GlcN.HCl (oral 100 mg/kg/day) and MucoP (oral 100 mg/kg/day). Experimental animals were sacrificed after 8 weeks of treatment and the distal femur was removed for macroscopic examination, histological assessment, and terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assay of the OA rabbits.

RESULTS

On gross morphology, severe lesions were observed in articular cartilage in the negative control group. In the GlcN.HCl and MucoP treatment groups, fibrillations and cartilaginous lesions were significantly (P < 0.05) decreased compared to the negative control group. In particular, degenerative changes in cartilage and chondrocyte cellularity were significantly reduced (P < 0.05) in the positive control (celecoxib) group, GlcN.HCl treatment group and MucoP treatment group compared with the negative control group. TUNEL assay showed that apoptotic chondrocytes were significantly suppressed in the celecoxib group. Similar significant (P < 0.05) results were seen in the GlcN.HCl group and MucoP group but apoptosis of chondrocytes were high in the negative control group.

CONCLUSION

These data suggest that the protective effects of GlcN.HCl and MucoP may play a useful role in the clinical treatment of OA.