Gene Ontology (GO)-Driven Inference of Candidate Proteomic Markers Associated with Muscle Atrophy Conditions

Skeletal muscle homeostasis is essential for the maintenance of a healthy and active lifestyle. Imbalance in muscle homeostasis has significant consequences such as atrophy, loss of muscle mass, and progressive loss of functions. Aging-related muscle wasting, sarcopenia, and atrophy as a consequence of disease, such as cachexia, reduce the quality of life, increase morbidity and result in an overall poor prognosis. Investigating the muscle proteome related to muscle atrophy diseases has a great potential for diagnostic medicine to identify (i) potential protein biomarkers, and (ii) biological processes and functions common or unique to muscle wasting, cachexia, sarcopenia, and aging alone. We conducted a meta-analysis using gene ontology (GO) analysis of 24 human proteomic studies using tissue samples (skeletal muscle and adipose biopsies) and/or biofluids (serum, plasma, urine). Whilst there were few similarities in protein directionality across studies, biological processes common to conditions were identified. Here we demonstrate that the GO analysis of published human proteomics data can identify processes not revealed by single studies. We recommend the integration of proteomics data from tissue samples and biofluids to yield a comprehensive overview of the human skeletal muscle proteome. This will facilitate the identification of biomarkers and potential pathways of muscle-wasting conditions for use in clinics.

Decoding the role of inflammation-related microRNAs in cancer cachexia: a study using HPV16-transgenic mice and in silico approaches

Cachexia is associated with poor prognosis in cancer patients, and inflammation is one of its main drive factors. MicroRNAs have recently emerged as important players in cancer cachexia and are involved in reciprocal regulation networks with pro-inflammatory signaling pathways. We hypothesize that inflammation-driven cancer cachexia is regulated by specific microRNAs. The aim of this study is to explore the expression and role of inflammation-related microRNAs in muscle wasting. HPV16-transgenic mice develop systemic inflammation and muscle wasting and are a model for cancer cachexia. We employed gastrocnemius muscle samples from these mice to study the expression of microRNAs. Bioinformatic tools were then used to explore their potential role in muscle wasting. Among the microRNAs studied, miR-223-3p (p = 0.004), let-7b-5p (p = 0.034), miR-21a-5p (p = 0.034), miR-150-5p (p = 0.027), and miR-155-5p (p = 0.011) were significantly upregulated in muscles from cachectic mice. In silico analysis showed that these microRNAs participate in several processes related to muscle wasting, including muscle structure development and regulation of the MAPK pathway. When analyzing protein-protein interactions (PPI)-networks, two major clusters and the top 10 hubs were obtained. From the top 10, Kras (p = 0.050) and Ccdn1 (p = 0.009) were downregulated in cachectic muscles, as well as Map2k3 (p = 0.007). These results show that miR-223-3p, let-7b-5p, miR-21a-5p, miR-150-5p, and miR-155-5p, play a role in muscle wasting in HPV16 transgenic mice, possible through regulating the MAPK cascades. Future experimental studies are required to validate our in silico analysis, and to explore the usefulness of these microRNAs and MAPK signaling as new potential biomarkers or therapy targets for cancer cachexia.

The role of the X chromosome in infectious diseases

Many infectious diseases in humans present with a sex bias. This bias arises from a combination of environmental factors, hormones and genetics. In this study, we review the contribution of the X chromosome to the genetic factor associated with infectious diseases. First, we give an overview of the X-linked genes that have been described in the context of infectious diseases and group them in four main pathways that seem to be dysregulated in infectious diseases: nuclear factor kappa-B, interleukin 2 and interferon γ cascade, toll-like receptors and programmed death ligand 1. Then, we review the infectious disease associations in existing genome-wide association studies (GWAS) from the GWAS Catalog and the Pan-UK Biobank, describing the main associations and their possible implications for the disease. Finally, we highlight the importance of including the X chromosome in GWAS analysis and the importance of sex-specific analysis.

Neuromuscular junctions are stable in patients with cancer cachexia

Cancer cachexia is a major cause of patient morbidity and mortality, with no efficacious treatment or management strategy. Despite cachexia sharing pathophysiological features with a number of neuromuscular wasting conditions, including age-related sarcopenia, the mechanisms underlying cachexia remain poorly understood. Studies of related conditions suggest that pathological targeting of the neuromuscular junction (NMJ) may play a key role in cachexia, but this has yet to be investigated in human patients. Here, high-resolution morphological analyses were undertaken on NMJs of rectus abdominis obtained from patients undergoing upper GI cancer surgery compared with controls (N = 30; n = 1,165 NMJs). Cancer patients included those with cachexia and weight-stable disease. Despite the low skeletal muscle index and significant muscle fiber atrophy (P < 0.0001) in patients with cachexia, NMJ morphology was fully conserved. No significant differences were observed in any of the pre- and postsynaptic variables measured. We conclude that NMJs remain structurally intact in rectus abdominis in both cancer and cachexia, suggesting that denervation of skeletal muscle is not a major driver of pathogenesis. The absence of NMJ pathology is in stark contrast to what is found in related conditions, such as age-related sarcopenia, and supports the hypothesis that intrinsic changes within skeletal muscle, independent of any changes in motor neurons, represent the primary locus of neuromuscular pathology in cancer cachexia.

Cisplatin-Induced Skeletal Muscle Dysfunction: Mechanisms and Counteracting Therapeutic Strategies

Among the severe side effects induced by cisplatin chemotherapy, muscle wasting is the most relevant one. This effect is a major cause for a clinical decline of cancer patients, since it is a negative predictor of treatment outcome and associated to increased mortality. However, despite its toxicity even at low doses, cisplatin remains the first-line therapy for several types of solid tumors. Thus, effective pharmacological treatments counteracting or minimizing cisplatin-induced muscle wasting are urgently needed. The dissection of the molecular pathways responsible for cisplatin-induced muscle dysfunction gives the possibility to identify novel promising therapeutic targets. In this context, the use of animal model of cisplatin-induced cachexia is very useful. Here, we report an update of the most relevant researches on the mechanisms underlying cisplatin-induced muscle wasting and on the most promising potential therapeutic options to preserve muscle mass and function.

Ether-Oxygen Containing Electrospun Microfibrous and Sub-Microfibrous Scaffolds Based on Poly(butylene 1,4-cyclohexanedicarboxylate) for Skeletal Muscle Tissue Engineering

We report the study of novel biodegradable electrospun scaffolds from poly(butylene 1,4-cyclohexandicarboxylate-co-triethylene cyclohexanedicarboxylate) (P(BCE-co-TECE)) as support for in vitro and in vivo muscle tissue regeneration. We demonstrate that chemical composition, i.e., the amount of TECE co-units (constituted of polyethylene glycol-like moieties), and fibre morphology, i.e., aligned microfibrous or sub-microfibrous scaffolds, are crucial in determining the material biocompatibility. Indeed, the presence of ether linkages influences surface wettability, mechanical properties, hydrolytic degradation rate, and density of cell anchoring points of the studied materials. On the other hand, electrospun scaffolds improve cell adhesion, proliferation, and differentiation by favouring cell alignment along fibre direction (fibre morphology), also allowing for better cell infiltration and oxygen and nutrient diffusion (fibre size). Overall, C2C12 myogenic cells highly differentiated into mature myotubes when cultured on microfibres realised with the copolymer richest in TECE co-units (micro-P73 mat). Lastly, when transplanted in the tibialis anterior muscles of healthy, injured, or dystrophic mice, micro-P73 mat appeared highly vascularised, colonised by murine cells and perfectly integrated with host muscles, thus confirming the suitability of P(BCE-co-TECE) scaffolds as substrates for skeletal muscle tissue engineering.