Effect of mechanical strain on the collagen VI pericellular matrix in anterior cruciate ligament fibroblasts

Collagen VI in the Musculoskeletal System

Collagen VI exerts several functions in the tissues in which it is expressed, including mechanical roles, cytoprotective functions with the inhibition of apoptosis and oxidative damage, and the promotion of tumor growth and progression by the regulation of cell differentiation and autophagic mechanisms. Mutations in the genes encoding collagen VI main chains, COL6A1, COL6A2 and COL6A3, are responsible for a spectrum of congenital muscular disorders, namely Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM) and myosclerosis myopathy (MM), which show a variable combination of muscle wasting and weakness, joint contractures, distal laxity, and respiratory compromise. No effective therapeutic strategy is available so far for these diseases; moreover, the effects of collagen VI mutations on other tissues is poorly investigated. The aim of this review is to outline the role of collagen VI in the musculoskeletal system and to give an update about the tissue-specific functions revealed by studies on animal models and from patients' derived samples in order to fill the knowledge gap between scientists and the clinicians who daily manage patients affected by collagen VI-related myopathies.

Peptide location fingerprinting identifies species- and tissue-conserved structural remodelling of proteins as a consequence of ageing and disease

Extracellular matrices (ECMs) in the intervertebral disc (IVD), lung and artery are thought to undergo age-dependant accumulation of damage by chronic exposure to mechanisms such as reactive oxygen species, proteases and glycation. It is unknown whether this damage accumulation is species-dependant (via differing lifespans and hence cumulative exposures) or whether it can influence the progression of age-related diseases such as atherosclerosis. Peptide location fingerprinting (PLF) is a new proteomic analysis method, capable of the non-targeted identification of structure-associated changes within proteins. Here we applied PLF to publicly available ageing human IVD (outer annulus fibrosus), ageing mouse lung and human arterial atherosclerosis datasets and bioinformatically identified novel target proteins alongside common age-associated differences within protein structures which were conserved between three ECM-rich organs, two species, three IVD tissue regions, sexes and in an age-related disease. We identify peptide yield differences across protein structures which coincide with biological regions, potentially reflecting the functional consequences of ageing or atherosclerosis for macromolecular assemblies (collagen VI), enzyme/inhibitor activity (alpha-2 macroglobulin), activation states (complement C3) and interaction states (laminins, perlecan, fibronectin, filamin-A, collagen XIV and apolipoprotein-B). Furthermore, we show that alpha-2 macroglobulin and collagen XIV exhibit possible shared structural consequences in IVD ageing and arterial atherosclerosis, providing novel links between an age-related disease and intrinsic ageing. Crucially, we also demonstrate that fibronectin, laminin beta chains and filamin-A all exhibit conserved age-associated structural differences between mouse lung and human IVD, providing evidence that ECM, and their associating proteins, may be subjected to potentially similar mechanisms or consequences of ageing across both species, irrespective of differences in lifespan and tissue function.

Mechano growth factor pretreatment yield mechanical stimuli induced cell stress responses in ligament fibroblasts of osteoarthritis via activating ATF-2

OBJECTIVE

The purpose of this study is to investigate whether mechanical growth factor (MGF) promotes mechanical response to ligament fibroblasts in osteoarthritis knee cavity via activating transcription factor 2 (ATF-2).

RESULTS

Osteoarthritis ligament fibroblasts (OA-LFs) were suffered from 12% static mechanical stretch to mimic mechanical force mediated ligament injury. Meanwhile, OA-LFs were treated with MGF before and during mechanical stretch. We observed that OA delayed LFs response to mechanical injury, while MGF pretreatment promoted cells timely feedback the mechanically stimuli by inducing cellular stress. Additionally, MGF accelerated the ligament injury repair by promoting cell migration, decreasing the MMP-2 activity, and remitting the cell deformation via ATF-2 activating in cells.

CONCLUSIONS

Our study shows that MGF pretreatment of OA-LFs can respond quickly to mechanical damage and repair ligament tissue by activating ATF-2. Therefore, MGF has potential as a therapeutic for OA patients.

High Prevalence of Connective Tissue Gene Variants in Professional Ballet

BACKGROUND

There is a high prevalence of hypermobility spectrum disorder (HSD) in dancers. While there is no known genetic variant for HSD, hypermobile Ehlers-Danlos syndrome is a genetic disorder that exists within HSD. There are many connective tissue disorders (CTDs) with known (and unknown) genes associated with hypermobility. Hypermobility has distinct advantages for participation in flexibility sports, including ballet.

PURPOSE

To determine the prevalence of gene variants associated with hypermobility in a large professional ballet company.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In this cross-sectional investigation, 51 professional male and female dancers from a large metropolitan ballet company were eligible and offered participation after an oral and written informed consent process. Whole blood was obtained from peripheral venipuncture, and DNA was isolated. Isolated DNA was subsequently enriched for the coding exons of 60 genes associated with CTD that included hypermobility as a phenotype, including Ehlers-Danlos syndromes, osteogenesis imperfecta, Marfan syndrome, and others. Genes were targeted with hybrid capture technology. Prepared DNA libraries were then sequenced with next-generation sequencing technology. Genetic database search tools (Human Gene Mutation Database and e!Ensembl, http://useast.ensembl.org/ ) were used to query specific variants. Descriptive statistics were calculated.

RESULTS

Of 51 dancers, 32 (63%) agreed to participate in DNA analysis (mean ± SD age, 24.3 ± 4.4 years; 18 men, 14 women). Twenty-eight dancers had at least 1 variant in the 60 genes tested, for an 88% prevalence. A total of 80 variants were found. A variant in 26 of the 60 genes was found in at least 1 dancer. Among the 28 dancers with variants, 16 were found in the TTN gene; 10 in ZNF469; 5 in RYR1; 4 in COL12A1; 3 in ABCC6 and COL6A2; 2 in ADAMTS2, CBS, COL1A2, COL6A3, SLC2A10, TNC, and TNXB; and 1 in ATP6V0A2, B4GALT7, BMP1, COL11A1, COL5A2, COL6A1, DSE, FBN1, FBN2, NOTCH1, PRDM5, SMAD3, and TGFBR1. Nine variants found in this population have never been reported. No identified variant was identical to any other variant. No identified variant was known to be disease causing. In the general population, the prevalence of each variant ranges from never reported to 0.33%. In the study population, the prevalence of each variant was 3.13%. There was no association between hypermobility scores and genetic variants.

CONCLUSION

Genetic variants in CTD-associated genes are highly prevalent (88%) in professional ballet dancers. This may significantly account for the high degree of motion in this population.

Neuron/Glial Antigen 2-Type VI Collagen Interactions During Murine Temporomandibular Joint Osteoarthritis

The degeneration of articular cartilage underscores the clinical pathology of temporomandibular joint osteoarthritis (TMJ-OA) and is promoted through dysfunctional biochemical or biophysical signaling. Transduction of these signals has a multifaceted regulation that includes important cell-matrix derived interactions. The matrix encapsulating the cells of the mandibular condylar cartilage (MCC) is rich in type VI collagen. Neuron/glia antigen 2 (NG2) is a type I transmembrane proteoglycan that binds with type VI collagen. This study defines the temporospatial dynamics of NG2-type VI collagen interactions during the progression of TMJ-OA. Membrane-bound NG2 is found to colocalize with pericellular type VI collagen in superficial layer cells in the MCC perichondrium but is present at high levels in the cytosol of chondroblastic and hypertrophic cells. When TMJ -OA is induced using a surgical instability model, localized disruptions of pericellular type VI collagen are observed on the central and medial MCC and are associated with significantly higher levels of cytosolic NG2. NG2 localized within the cytosol is found to be transported through clathrin and dynamin mediated endocytic pathways. These findings are consistent with NG2 behavior in other injury models and underscore the potential of NG2 as an entirely novel molecular mechanism of chondrocyte function contextually linked with TMJ-OA.

Tendon Extracellular Matrix Alterations in Ullrich Congenital Muscular Dystrophy

Collagen VI (COLVI) is a non-fibrillar collagen expressed in skeletal muscle and most connective tissues. Mutations in COLVI genes cause two major clinical forms, Bethlem myopathy and Ullrich congenital muscular dystrophy (UCMD). In addition to congenital muscle weakness, patients affected by COLVI myopathies show axial and proximal joint contractures and distal joint hypermobility, which suggest the involvement of the tendon function. We examined a peroneal tendon biopsy and tenocyte culture of a 15-year-old patient affected by UCMD with compound heterozygous COL6A2 mutations. In patient’s tendon biopsy, we found striking morphological alterations of tendon fibrils, consisting in irregular profiles and reduced mean diameter. The organization of the pericellular matrix of tenocytes, the primary site of collagen fibril assembly, was severely affected, as determined by immunoelectron microscopy, which showed an abnormal accumulation of COLVI and altered distribution of collagen I (COLI) and fibronectin (FBN). In patient’s tenocyte culture, COLVI web formation and cell surface association were severely impaired; large aggregates of COLVI, which matched with COLI labeling, were frequently detected in the extracellular matrix. In addition, metalloproteinase MMP-2, an extracellular matrix-regulating enzyme, was increased in the conditioned medium of patient’s tenocytes, as determined by gelatin zymography and western blot. Altogether, these data indicate that COLVI deficiency may influence the organization of UCMD tendon matrix, resulting in dysfunctional fibrillogenesis. The alterations of tendon matrix may contribute to the complex pathogenesis of COLVI related myopathies.

Differentiating zones at periodontal ligament-bone and periodontal ligament-cementum entheses

BACKGROUND AND OBJECTIVE

The structural and functional integrity of bone-periodontal ligament (PDL)-cementum complex stems from the load-bearing attachment sites (entheses) between soft (PDL) and hard (bone, cementum) tissues. These attachment sites are responsible for the maintenance of a bone-PDL-cementum complex biomechanical function. The objective was to investigate changes in spatiotemporal expression of key biomolecules in developing and functionally active entheses.

MATERIAL AND METHODS

Multilabeling technique was performed on hemimandibles of 3 wk and 3 mo-old scleraxis-GFP transgenic mice for CD146, CD31, NG2, osterix and bone sialoprotein. Regions of dominant stretch within the PDL were evaluated by identifying directionality of collagen fibrils, PDL fibroblasts and PDL cell cytoskeleton.

RESULTS

CD146+ cells adjacent to CD31+ vasculature were identified at PDL-bone enthesis. NG2+ cells were located at coronal bone-PDL and apical cementum-PDL entheses in the 3-wk-old group, but at 3 mo, NG2 was positive at the entheses of the apical region and alveolar crest. NG2 and osterix were colocalized at the osteoid and cementoid regions of the PDL-bone and PDL-cementum entheses. Bone sialoprotein was prominent at the apical region of 3-wk-old mice. The directionality of collagen fibers, fibroblasts and their cytoskeleton overlapped, except in the apical region of 3 wk.

CONCLUSION

Colocalization of biomolecules at zones of the PDL adjacent to attachment sites may be essential for the formation of precementum and osteoid interfaces at a load-bearing bone-PDL-tooth fibrous joint. Biophysical cues resulting from development and function can regulate recruitment and differentiation of stem cells potentially from a vascular origin toward osteo- and cemento-blastic lineages at the PDL-bone and PDL-cementum entheses. Investigating the coupled effect of biophysical and biochemical stimuli leading to cell differentiation at the functional attachment sites is critical for developing regeneration strategies to enable functional reconstruction of the periodontal complex.