Tendon Extracellular Matrix Remodeling and Defective Cell Polarization in the Presence of Collagen VI Mutations

Abstract

Mutations in collagen VI genes cause two major clinical myopathies, Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD), and the rarer myosclerosis myopathy. In addition to congenital muscle weakness, patients affected by collagen VI-related myopathies show axial and proximal joint contractures, and distal joint hypermobility, which suggest the involvement of tendon function. To gain further insight into the role of collagen VI in human tendon structure and function, we performed ultrastructural, biochemical, and RT-PCR analysis on tendon biopsies and on cell cultures derived from two patients affected with BM and UCMD. In vitro studies revealed striking alterations in the collagen VI network, associated with disruption of the collagen VI-NG2 (Collagen VI-neural/glial antigen 2) axis and defects in cell polarization and migration. The organization of extracellular matrix (ECM) components, as regards collagens I and XII, was also affected, along with an increase in the active form of metalloproteinase 2 (MMP2). In agreement with the in vitro alterations, tendon biopsies from collagen VI-related myopathy patients displayed striking changes in collagen fibril morphology and cell death. These data point to a critical role of collagen VI in tendon matrix organization and cell behavior. The remodeling of the tendon matrix may contribute to the muscle dysfunction observed in BM and UCMD patients.

Interleukin‐6 neutralization ameliorates symptoms in prematurely aged mice

“…Adipocyte, osteoblast, tenocyte and myoblast cultures were established as previously described from mouse subcutaneous fat, rib bone and skeletal muscle (vastus lateralis), respectively, and differentiated according to established protocols (Antoniel et al, 2020; Avnet et al, 2011; Mattioli et al, 2011; Pellegrini et al, 2019).…”

Personalized in vitro Extracellular Matrix Models of Collagen VI-Related Muscular Dystrophies

“…Our results showed increased FN alignment in CDMs from patients with COL6-RDs, in agreement with the characteristics reported by Theocharidis et al on COL6-depleted CDMs, which presented aligned FN fibrils, more dispersed and thicker compared to controls ( Theocharidis et al, 2016 ). Similarly, Sabatelli et al and Antoniel et al showed in cultured patients’ fibroblasts that deficiency of COL6 leads to aligned FN fibrils ( Sabatelli et al, 2001 ), ( Antoniel et al, 2020 ). Of note, our experiments were conducted employing primary fibroblasts that reflect the genetic background of patients and the most common scenario in COL6-RD, which is partially reduced COL6 rather than completely absent.…”

“…We observed that its expression is significantly lower than in the CDMs of healthy donors, predominantly in intermediate and UCMD phenotypes. Especially in UCMD and intermediate COL6-RD fibroblasts cultures, mutations are reported to cause alterations to COL6 patterning, such as aggregates, reduced expression and secretion deficiency ( Lamandé and Bateman, 2018 ), ( Tagliavini et al, 2014 ), ( Antoniel et al, 2020 ). Using automatic fibrils reconstruction, we found that less fibrils were deposited in the CDMs from patients with COL6-RDs and that they appeared shorter in length, and less aligned than those secreted in control CDMs.…”

“…Using automatic fibrils reconstruction, we found that less fibrils were deposited in the CDMs from patients with COL6-RDs and that they appeared shorter in length, and less aligned than those secreted in control CDMs. Shorter single microfilaments of COL6 have been reported to accumulate in the ECMs of proliferating tendon fibroblasts from patients displaying UCMD and BM phenotypes ( Antoniel et al, 2020 ). COL6 interacts with several ECM proteins and it is implicated in collagens fibrillogenesis, fundamental for tissue assembly and function ( Cescon et al, 2015 ), ( Minamitani et al, 2004 ).…”

“…Investigating the interplay of different ECM structures as well as cell signaling underlying fibrils deposition may contribute to answer key biological questions that have implication in COL6-RD. It is still not clear which is the mechanism underlying the joint contractures - most invalidating trait of the disease - and other connective tissue features of COL6-RD, but the cause is likely to be related to the association of COL6 with other ECM components and with receptors on the cell surface in those tissues ( Paco et al, 2015 ), ( Antoniel et al, 2020 ). Fibrillins are major components of elastic fibers, which are relevant in the context of COL6-RD and other connective tissue diseases where tendons and ligaments are also affected.…”