Preparation of Human Muscle Precursor Cells for the MyoGravity Project’s Study of Cell Cultures in Experiment Units for Space Flight Purposes

The MyoGravity project to study real microgravity effects on human muscle precursor cells and tissue

Microgravity (µG) experienced during space flights promotes adaptation in several astronauts' organs and tissues, with skeletal muscles being the most affected. In response to reduced gravitational loading, muscles (especially, lower limb and antigravity muscles) undergo progressive mass loss and alteration in metabolism, myofiber size, and composition. Skeletal muscle precursor cells (MPCs), also known as satellite cells, are responsible for the growth and maintenance of muscle mass in adult life as well as for muscle regeneration following damage and may have a major role in µG-induced muscle wasting. Despite the great relevance for astronaut health, very few data are available about the effects of real µG on human muscles. Based on the MyoGravity project, this study aimed to analyze: (i) the cellular and transcriptional alterations induced by real µG in human MPCs (huMPCs) and (ii) the response of human skeletal muscle to normal gravitational loading after prolonged exposure to µG. We evaluated the transcriptomic changes induced by µG on board the International Space Station (ISS) in differentiating huMPCs isolated from Vastus lateralis muscle biopsies of a pre-flight astronaut and an age- and sex-matched volunteer, in comparison with the same cells cultured on the ground in standard gravity (1×g) conditions. We found that huMPCs differentiated under real µG conditions showed: (i) upregulation of genes related to cell adhesion, plasma membrane components, and ion transport; (ii) strong downregulation of genes related to the muscle contraction machinery and sarcomere organization; and (iii) downregulation of muscle-specific microRNAs (myomiRs). Moreover, we had the unique opportunity to analyze huMPCs and skeletal muscle tissue of the same astronaut before and 30 h after a long-duration space flight on board the ISS. Prolonged exposure to real µG strongly affected the biology and functionality of the astronaut's satellite cells, which showed a dramatic reduction of responsiveness to activating stimuli and proliferation rate, morphological changes, and almost inability to fuse into myotubes. RNA-Seq analysis of post- vs. pre-flight muscle tissue showed that genes involved in muscle structure and remodeling are promptly activated after landing following a long-duration space mission. Conversely, genes involved in the myelination process or synapse and neuromuscular junction organization appeared downregulated. Although we have investigated only one astronaut, these results point to a prompt readaptation of the skeletal muscle mechanical components to the normal gravitational loading, but the inability to rapidly recover the physiological muscle myelination/innervation pattern after landing from a long-duration space flight. Together with the persistent functional deficit observed in the astronaut's satellite cells after prolonged exposure to real µG, these results lead us to hypothesize that a condition of inefficient regeneration is likely to occur in the muscles of post-flight astronauts following damage.

Report and Abstracts of the 20th Meeting of IIM, the Interuniversity Institute of Myology: Assisi, October 12-15, 2023

The 2023 represented a milestone for the Interuniversity Institute of Myology (IIM) since it marked twenty years of IIM activity joined with the 20th annual meeting organized by the association. The 20th IIM meeting took place in the fascinating town of Assisi, in the heart of central Italy, from 12 to 15 October. The commemorative 20th edition of the meeting represented a success in terms of participation and contributions as it brought together 160 myologists, clinicians, pharmaceutical companies, and patient organization representatives from Italy, several European countries (especially France), the United Kingdom, Brazil, and the USA. Four main scientific sessions hosted 36 oral communications and 54 always-on-display posters reporting original and unpublished results. Four main lectures from internationally renowned invited speakers and talks from delegates of the Societé Française de Myologie gave particular interest and emphasis to the scientific discussion. In line with the traditional policy of the IIM to encourage the participation of young researchers, about 50% of the attendees were under 35 years old. Moreover, the 20th IIM meeting was part of the high-training course in "Advanced Myology Update 2023", reserved to young trainees and managed by the University of Perugia (Italy) in collaboration with the IIM. In addition to the meeting scientific sessions, the 29 attendees to the course had a dedicated round table and dedicated lessons with the IIM invited speakers as teachers. Awards for the best talk, best poster blitz, and best poster have been conferred to young attendees, who became part of the IIM Young Committee, involved in the scientific organization of the IIM meetings. To celebrate the 20th IIM anniversary, a special free-access educational convention on "Causes and mechanisms of muscle atrophy. From terrestrial disuse to Space flights" has been organized, in which IIM experts in the field have illustrated the current knowledge about the muscle atrophy process in several atrophying conditions, and the former Italian astronaut, Paolo Nespoli shared his incredible experience in Space fascinating the large audience attending both in presence and online live stream. The meeting was characterized by a vibrant, friendly, and inclusive atmosphere, and stimulated discussion on emerging areas of muscle research, fostering international collaborations, and confirming the IIM meeting as an ideal venue to discuss around muscle development, function, and diseases pointing to the development of efficacious therapeutic strategies. Here, the abstracts of the meeting illustrate the most recent results on basic, translational, and clinical research in the myology field. Some abstracts are missing as per authors' decision due to the patentability of the results.

MicroRNA Expression in Subretinal Fluid in Eyes Affected by Rhegmatogenous Retinal Detachment

Proliferative vitreoretinopathy (PVR) is an abnormal intraocular scarring process that can complicate cases of rhegmatogenous retinal detachment (RRD). Although previous studies have examined the relevance of microRNAs (miRNAs) in ophthalmic diseases, only a few studies have evaluated the expression profiles of microRNAs in subretinal fluid. We hypothesized that the expression profiles of specific miRNAs may change in response to RRD, in the subretinal fluid that is directly in contact with photoreceptors and the retinal pigment epithelium (RPE). We looked for a potential correlation between the expression of specific miRNAs in eyes with RRD and known clinical risk factors of PVR. A total of 24 patients (59 ± 11 years) who underwent scleral buckling procedure were enrolled in this prospective study. Twenty-four undiluted subretinal fluid samples were collected, RNA was isolated and qRT-PCR was performed to analyze the expression of 12 miRNAs. We found the existence of a positive association between the expression of miR-21 (p = 0.017, r = 0.515) and miR-34 (p = 0.030, r = 0.624) and the duration of symptoms related to retinal detachment. Moreover, the expression of miR-146a tended to decrease in patients who developed PVR. Subretinal fluid constitutes an intriguing biological matrix to evaluate the role of miRNAs leading to the development of PVR.