Reduction in skeletal muscle fibrosis of spontaneously hypertensive rats after laceration by microRNA targeting angiotensin II receptor

l-Carnitine relieves cachexia-related skeletal muscle fibrosis by inducing deltex E3 ubiquitin ligase 3L to negatively regulate the Runx2/COL1A1 axis

BACKGROUND

Cancer cachexia-induced skeletal muscle fibrosis (SMF) impairs muscle regeneration, alters the muscle structure and function, reduces the efficacy of anticancer drugs, diminishes the patient's quality of life and shortens overall survival. RUNX family transcription factor 2 (Runx2), a transcription factor, and collagen type I alpha 1 chain (COL1A1), the principal constituent of SMF, have been linked previously, with Runx2 shown to directly modulate COL1A1 mRNA levels. l-Carnitine, a marker of cancer cachexia, can alleviate fibrosis in liver and kidney models; however, its role in cancer cachexia-associated fibrosis and the involvement of Runx2 in the process remain unexplored.

METHODS

Female C57 mice (48 weeks old) were inoculated subcutaneously with MC38 cells to establish a cancer cachexia model. A 5 mg/kg dose of l-carnitine or an equivalent volume of water was administered for 14 days via oral gavage, followed by assessments of muscle function (grip strength) and fibrosis. To elucidate the interplay between the deltex E3 ubiquitin ligase 3L(DTX3L)/Runx2/COL1A1 axis and fibrosis in transforming growth factor beta 1-stimulated NIH/3T3 cells, a suite of molecular techniques, including quantitative real-time PCR, western blot analysis, co-immunoprecipitation, molecular docking, immunofluorescence and Duolink assays, were used. The relevance of the DTX3L/Runx2/COL1A1 axis in the gastrocnemius was also explored in the in vivo model.

RESULTS

l-Carnitine supplementation reduced cancer cachexia-induced declines in grip strength (>88.2%, P < 0.05) and the collagen fibre area within the gastrocnemius (>57.9%, P < 0.05). At the 5 mg/kg dose, l-carnitine also suppressed COL1A1 and alpha-smooth muscle actin (α-SMA) protein expression, which are markers of SMF and myofibroblasts. Analyses of the TRRUST database indicated that Runx2 regulates both COL1A1 and COL1A2. In vitro, l-carnitine diminished Runx2 protein levels and promoted its ubiquitination. Overexpression of Runx2 abolished the effects of l-carnitine on COL1A1 and α-SMA. Co-immunoprecipitation, molecular docking, immunofluorescence and Duolink assays confirmed an interaction between DTX3L and Runx2, with l-carnitine enhancing this interaction to promote Runx2 ubiquitination. l-Carnitine supplementation restored DTX3L levels to those observed under non-cachectic conditions, both in vitro and in vivo. Knockdown of DTX3L abolished the effects of l-carnitine on Runx2, COL1A1 and α-SMA in vitro. The expression of DTX3L was negatively correlated with the levels of Runx2 and COL1A1 in untreated NIH/3T3 cells.

CONCLUSIONS

This study revealed a previously unrecognized link between Runx2 and DTX3L in SMF and demonstrated that l-carnitine exerted a significant therapeutic impact on cancer cachexia-associated SMF, potentially through the upregulation of DTX3L.

Disruptive 3D in vitro models for respiratory disease investigation: A state-of-the-art approach focused on SARS-CoV-2 infection

COVID-19, along with most respiratory diseases in the medical field, demonstrates significant ability to take its toll on global population. There is a particular difficulty in studying these conditions, which stems especially from the short supply of in vitro models for detailed investigation, the specific therapeutic knowledge required for disease scrutinization and the occasional need of BSL-3 [Biosafety Level 3] laboratories for research. Based on this, the process of drug development is hampered to a great extent. In the scenario of COVID-19, this difficulty is even more substantial on account of the current undefinition regarding the exact role of the ACE2 [Angiotensin-converting enzyme 2] receptor upon SARS-CoV-2 kinetics in human cells and the great level of demand in the investigation process of ACE2, which usually requires the laborious and ethically complicated usage of transgenic animal models overexpressing the receptor. Moreover, the rapid progression of the aforementioned diseases, especially COVID-19, poses a crucial necessity for adequate therapeutic solutions emergence. In this context, the work herein presented introduces a groundbreaking set of 3D models, namely spheroids and MatriWell cell culture inserts, whose remarkable ability to mimic the in vivo environment makes them highly suitable for respiratory diseases investigation, particularly SARS-CoV-2 infection. Using MatriWells, we developed an innovative platform for COVID-19 research: a pulmonary air-liquid interface [ALI] associated with endothelial (HUVEC) cells. Infection studies revealed that pulmonary (BEAS-2B) cells in the ALI reached peak viral load at 24h and endothelial cells, at 48h, demonstrating lung viral replication and subsequent hematogenous dissemination, which provides us with a unique and realistic framework for studying COVID-19. Simultaneously, the spheroids were used to address the understudied ACE2 receptor, aiming at a pronounced process of COVID-19 investigation. ACE2 expression not only increased spheroid diameter by 20% (p<0.001) and volume by 60% (p≤0.0001) but also led to a remarkable 640-fold increase in intracellular viral load (p≤0.01). The previously mentioned finding supports ACE2 as a potential target for COVID-19 treatment. Lastly, we observed a higher viral load in the MatriWells compared to spheroids (150-fold, p<0.0001), suggesting the MatriWells as a more appropriate approach for COVID-19 investigation. By establishing an advanced method for respiratory tract conditions research, this work paves the way toward an efficacious process of drug development, contributing to a change in the course of respiratory diseases such as COVID-19.

Kinin receptors regulate skeletal muscle regeneration: differential effects for B1 and B2 receptors

OBJECTIVE AND DESIGN

After traumatic skeletal muscle injury, muscle healing is often incomplete and produces extensive fibrosis. Bradykinin (BK) reduces fibrosis in renal and cardiac damage models through the B2 receptor. The B1 receptor expression is induced by damage, and blocking of the kallikrein-kinin system seems to affect the progression of muscular dystrophy. We hypothesized that both kinin B1 and B2 receptors could play a differential role after traumatic muscle injury, and the lack of the B1 receptor could produce more cellular and molecular substrates for myogenesis and fewer substrates for fibrosis, leading to better muscle healing.

MATERIAL AND METHODS

To test this hypothesis, tibialis anterior muscles of kinin receptor knockout animals were subjected to traumatic injury. Myogenesis, angiogenesis, fibrosis, and muscle functioning were evaluated.

RESULTS

Injured B1KO mice showed a faster healing progression of the injured area with a larger amount of central nucleated fiber post-injury when compared to control mice. In addition, they exhibited higher neovasculogenic capacity, maintaining optimal tissue perfusion for the post-injury phase; had higher amounts of myogenic markers with less inflammatory infiltrate and tissue destruction. This was followed by higher amounts of SMAD7 and lower amounts of p-SMAD2/3, which resulted in less fibrosis. In contrast, B2KO and B1B2KO mice showed more severe tissue destruction and excessive fibrosis. B1KO animals had better results in post-injury functional tests compared to control animals.

CONCLUSIONS

We demonstrate that injured skeletal muscle tissues have a better repair capacity with less fibrosis in the presence of B2 receptor and absence of B1 receptor, including better performances in functional tests.

Firearms-related skeletal muscle trauma: pathophysiology and novel approaches for regeneration

One major cause of traumatic injury is firearm-related wounds (i.e., ballistic trauma), common in both civilian and military populations, which is increasing in prevalence and has serious long-term health and socioeconomic consequences worldwide. Common primary injuries of ballistic trauma include soft-tissue damage and loss, haemorrhage, bone fracture, and pain. The majority of injuries are of musculoskeletal origin and located in the extremities, such that skeletal muscle offers a major therapeutic target to aid recovery and return to normal daily activities. However, the underlying pathophysiology of skeletal muscle ballistic trauma remains poorly understood, with limited evidence-based treatment options. As such, this review will address the topic of firearm-related skeletal muscle injury and regeneration. We first introduce trauma ballistics and the immediate injury of skeletal muscle, followed by detailed coverage of the underlying biological mechanisms involved in regulating skeletal muscle dysfunction following injury, with a specific focus on the processes of muscle regeneration, muscle wasting and vascular impairments. Finally, we evaluate novel approaches for minimising muscle damage and enhancing muscle regeneration after ballistic trauma, which may have important relevance for primary care in victims of violence.

Adiponectin promotes muscle regeneration through binding to T-cadherin

Skeletal muscle has remarkable regenerative potential and its decline with aging is suggested to be one of the important causes of loss of muscle mass and quality of life in elderly adults. Metabolic abnormalities such as obesity were linked with decline of muscle regeneration. On the other hand, plasma levels of adiponectin are decreased in such metabolic conditions. However, plasma levels of adiponectin have been shown to inversely correlate with muscle mass and strength in elderly people especially with chronic heart failure (CHF). Here we have addressed whether adiponectin has some impact on muscle regeneration after cardiotoxin-induced muscle injury in mice. Muscle regeneration was delayed by angiotensin II infusion, mimicking aging and CHF as reported. Adiponectin overexpression in vivo decreased necrotic region and increased regenerating myofibers. Such enhanced regeneration by excess adiponectin was also observed in adiponectin null mice, but not in T-cadherin null mice. Mechanistically, adiponectin accumulated on plasma membrane of myofibers both in mice and human, and intracellularly colocalized with endosomes positive for a multivesicular bodies/exosomes marker CD63 in regenerating myofibers. Purified high-molecular multimeric adiponectin similarly accumulated intracellularly and colocalized with CD63-positive endosomes and enhanced exosome secretion in differentiating C2C12 myotubes but not in undifferentiated myoblasts. Knockdown of T-cadherin in differentiating C2C12 myotubes attenuated both adiponectin-accumulation and adiponectin-mediated exosome production. Collectively, our studies have firstly demonstrated that adiponectin stimulates muscle regeneration through T-cadherin, where intracellular accumulation and exosome-mediated process of adiponectin may have some roles.