Collagen VI Muscle Disorders: Mutation Types, Pathogenic Mechanisms and Approaches to Therapy

Endotrophin, a Key Marker and Driver for Fibroinflammatory Disease

Our overview covers several key areas related to recent results obtained for collagen type VI and endotrophin (ETP). (1) An introduction to the history of ETP, including how it was identified, how it is released, and its function and potential receptors. (2) An introduction to the collagen family, with a focus on what differentiates collagen type VI from an evolutionary standpoint. (3) An overview of collagen type VI, the 6 individual chains (COL6A1, A2, A3, A4, A5, and A6), their differences and similarities, as well as their expression profiles and function. (4) A detailed analysis of COL6A3, including the cleaved product endotrophin, and what separates it from the other 5 collagen 6 molecules, including its suggested function based on insights gained from knockout and gain of function mouse models. (5) The pathology of ETP. What leads to its presence and release and what are the consequences thereof? (6) Functional implications of circulating ETP. Here we review the data with the functional roles of ETP in mind. (7) We propose that ETP is a mediator for fibrotic (or fibroinflammatory) disorders. Based on what we know about ETP, we have to consider it as a target for the treatment of fibrotic (or fibroinflammatory) disorders. What segment(s) of the patient population would most dramatically respond to an ETP-targeted intervention? How can we find the population that would profit most from an intervention? We aim to present a broad overview over the ETP field at large, providing an assessment of where the future research efforts need to be placed to tap into the vast potential of ETP, both as a marker and as a target in different diseases.

Anästhesie bei einer thoraxchirurgischen Patientin mit kongenitaler Muskeldystrophie Typ Ullrich

Die kongenitale Muskeldystrophie Typ Ullrich (UCMD) ist eine seltene Erkrankung. Weltweit wurden bislang 50 Fälle genetisch gesichert. Autosomal-dominante und rezessive Mutationen des COL6A1/COL6A2 im Chromosom 21q22.3 oder des COL6A3 im Chromosom 2q37.3 führen zu einem Mangel an Kollagen VI. Typische Merkmale der UCMD sind Muskelschwäche von Körperstamm und Extremitäten, Hyperflexibilität der distalen und Kontrakturen der proximalen Gelenke, Rollstuhlpflichtigkeit im Alter von 9 bis 11 Jahren, Versteifung und Skoliose der Wirbelsäule und eine progrediente restriktive Ventilationsstörung. Etwa 50 % der Kinder benötigen im Alter von 11 bis 12 Jahren eine nichtinvasive Ventilation (NIV), wozu auch eine gestörte Funktion des Diaphragmas beiträgt. Es wird über die Narkose bei einer 21-jährigen Patientin mit einer UCMD berichtet, die seit dem 6. Lebensjahr rollstuhlpflichtig war und bei der seit 2018 eine lebenserhaltene NIV erfolgte. Wegen einer subpleuralen Einblutung in den linken Lungenunterlappen nach Entlastung eines Pneumothorax wurde eine videoassistierte thorakoskopische Chirurgie (VATS) vorgenommen. Die spezifischen Anforderungen durch die UCMD, das Atemwegsmanagement für die Einlungenventilation sowie Aspekte zur Auswahl der Anästhetika werden diskutiert. Nach erfolgreicher VATS konnte die Patientin am 7. postoperativen Tag in die Häuslichkeit entlassen werden.

Oxidative Stress, Inflammation and Connexin Hemichannels in Muscular Dystrophies

Muscular dystrophies (MDs) are a heterogeneous group of congenital neuromuscular disorders whose clinical signs include myalgia, skeletal muscle weakness, hypotonia, and atrophy that leads to progressive muscle disability and loss of ambulation. MDs can also affect cardiac and respiratory muscles, impairing life-expectancy. MDs in clude Duchenne muscular dystrophy, Emery-Dreifuss muscular dystrophy, facioscapulohumeral muscular dystrophy and limb-girdle muscular dystrophy. These and other MDs are caused by mutations in genes that encode proteins responsible for the structure and function of skeletal muscles, such as components of the dystrophin-glycoprotein-complex that connect the sarcomeric-actin with the extracellular matrix, allowing contractile force transmission and providing stability during muscle contraction. Consequently, in dystrophic conditions in which such proteins are affected, muscle integrity is disrupted, leading to local inflammatory responses, oxidative stress, Ca²⁺-dyshomeostasis and muscle degeneration. In this scenario, dysregulation of connexin hemichannels seem to be an early disruptor of the homeostasis that further plays a relevant role in these processes. The interaction between all these elements constitutes a positive feedback loop that contributes to the worsening of the diseases. Thus, we discuss here the interplay between inflammation, oxidative stress and connexin hemichannels in the progression of MDs and their potential as therapeutic targets.