Organoid culture promotes dedifferentiation of mouse myoblasts into stem cells capable of complete muscle regeneration.

Experimental cell therapies for skeletal muscle conditions have shown little success, primarily because they use committed myogenic progenitors rather than true muscle stem cells, known as satellite cells. Here we present a method to generate in vitro-derived satellite cells (idSCs) from skeletal muscle tissue. When transplanted in small numbers into mouse muscle, mouse idSCs fuse into myofibers, repopulate the satellite cell niche, self-renew, support multiple rounds of muscle regeneration and improve force production on par with freshly isolated satellite cells in damaged skeletal muscle. We compared the epigenomic and transcriptional signatures between idSCs, myoblasts and satellite cells and used these signatures to identify core signaling pathways and genes that confer idSC functionality. Finally, from human muscle biopsies, we successfully generated satellite cell-like cells in vitro. After further development, idSCs may provide a scalable source of cells for the treatment of genetic muscle disorders, trauma-induced muscle damage and age-related muscle weakness.

Development of a Rat Model of Fasciotomy Treatment for Compartment Syndrome.

Skeletal muscle injuries are a major cause of disability for military and civilian populations. Compartment syndrome (CS) in skeletal muscle results from an edema-induced increase in intracompartmental pressure (ICP) after primary injury. Untreated ICP will occlude the tissue vasculature, tissue necrosis, and potential loss of limb. The current standard of care for CS is surgical fasciotomy, an incision through the muscle fascia to relieve ICP. Early fasciotomy will preserve the limb, but often leaves patients with long-term scarring and reduced muscle function. Our group previously developed and characterized a rat model of CS to explore the pathophysiology of CS and test new therapies. We present an expansion of this CS model, including the fasciotomy, to better simulate clinical treatment. CS was induced on the hind limb of adult male Lewis rats and fasciotomy was performed 24 h later. Less than 20% of the rats that underwent fasciotomy showed detectable force 4 days after injury, compared with the 75% of rats that underwent CS induction without fasciotomy. Muscles undergoing fasciotomy showed a significant increase in fibrosis and an increased number of macrophages, Pax7+ satellite cells, and α-smooth muscle actin+ myofibroblasts at 7 days postinjury. These data indicate that the use of fasciotomy in a rat model of CS resulted in injury sequelae that reflect the severity of human clinical disease presentation along with current standard of care. Impact Statement Current animal models of skeletal muscle injury struggle to accurately reflect the injury sequelae seen in humans, particularly in rats and mice. These animals also recover faster than humans do. More accurate recapitulation of the injury is needed to better study the injury progression, as well as screen for novel therapies. This research combines an existing model of compartment syndrome with its clinical standard of care (fasciotomy), creating a more accurate rat model of injury, and providing for a better treatment screening tool. These results show how our model leads to a sustained skeletal muscle deficit with increased inflammation.

From proposal to poster: course-based undergraduate research experience in a physiology laboratory course.

The laboratory course is an excellent venue to apply content, practice inquiry, improve critical thinking, practice key clinical skills, and work with data. The use of inquiry-based course projects allows for students to propose open ended questions, form a hypothesis, design an experiment, collect data, analyze data, draw conclusion, and present their findings. This comprehensive experience is ideal for a capstone (senior level) laboratory course that is the culmination of 4 yr of study in the degree. At Michigan State University, the capstone laboratory has incorporated a formal course-based research experience in human physiology. The rationale and logistics for running such an experience are described in this paper.

N-Acetyl-L-Cysteine Reduces Fibrosis and Improves Muscle Function After Acute Compartment Syndrome Injury.

INTRODUCTION: Upon injury, skeletal muscle undergoes a multiphase process beginning with degeneration of the damaged tissue, which is accompanied by inflammation and finally regeneration. One consequence of an injured microenvironment is excessive production of reactive oxygen species, which results in attenuated regeneration and recovery of function ultimately leading to fibrosis and disability. The objective of this research was to test the potential of the antioxidant, N-Acetyl-L-Cysteine (NAC), as a mediator of reactive oxygen species damage that results from traumatic muscle injury in order to support repair and regeneration of wounded muscle tissue and improve function recovery. MATERIALS AND METHODS: Adult female Lewis rats were subjected to compartment syndrome injury as previously published by our group. Rats received intramuscular injections of NAC or vehicle at 24, 48, and 72 hours postinjury. Muscle function, tissue fibrosis, and the expression of myogenic and angiogenic markers were measured. RESULTS: Muscle function was significantly improved, and tissue fibrosis was significantly decreased in NAC-treated muscles. CONCLUSIONS: These results suggest that NAC treatment of skeletal muscle after injury may be a viable option for the prevention of long-term fibrosis and scar formation, facilitating recovery of muscle function.

Organizing a large-scale Physiology Understanding (PhUn) Week event at a science center.

For the past 6 yr, the Department of Physiology at Michigan State University (MSU) has partnered with Impression 5 Science Center in Lansing, MI. Together, we host a day-long community engagement event on a Saturday each year in early November coinciding with the American Physiological Society's Physiology Understanding Week. The purpose was to provide a fun and memorable hands-on experience for children and families. This paper describes the detailed planning and logistics. The event takes place in the main exhibit space at the science center, generally has 15-17 physiology activities stations set up as booths run by volunteers, and the event runs as an open-house format. Three to five trained volunteers were needed per station for the full day. Since this was primarily based on undergraduate student volunteer involvement (a population already limited for time), morning, afternoon, and/or full-day shifts were offered to accommodate a variety of schedules. Additional set-up, clean-up, and general help was also recruited. Overall, ~100-150 MSU students, faculty, and staff members served as volunteers, alongside Impression 5 staff. Hosting the event at the science center generated a larger audience, aided in advertisement, and allowed for access to a large facility capable of handling the 600-1,000 attendees. The partnership facilitated the sharing of equipment and supplies for physiology demonstrations, allowed for activities on site in the chemistry laboratory space, and facilitated the growth of new community partnerships with local schools and groups who attended the event.

Physiology undergraduate degree requirements in the U.S.

Course-level learning objectives and core concepts for undergraduate physiology teaching exist. The next step is to consider how these resources fit into generalizable program-level guidelines for Bachelor of Science (BS) degrees in Physiology. In the absence of program-level guidelines for Physiology degree programs, we compiled a selective internal report to review degree requirements from 18 peer BS programs entitled "Physiology" in the United States (U.S.). There was a range of zero to three required semesters of math, physics, physics laboratory, general biology, biology laboratory, general chemistry, chemistry laboratory, organic chemistry, organic chemistry laboratory, biochemistry, biochemistry laboratory, anatomy, anatomy laboratory, core systems physiology, and physiology laboratory. Required upper division credits ranged from 11 to 31 and included system-specific, exercise and environmental, clinically relevant, pathology/disease-related, and basic science options. We hope that this information will be useful for all programs that consider themselves to be physiology, regardless of name. Reports such as this can serve as a starting point for collaboration among BS programs to improve physiology undergraduate education and best serve our students.

* The Impact of Age on Skeletal Muscle Progenitor Cell Survival and Fate After Injury.

Sarcopenia is defined as the loss of skeletal muscle mass and function due to age, and represents a major cause of disability in the elderly population. The contributing factors to the onset of sarcopenia are not well defined, but appear to involve age-dependent changes in both the tissue microenvironment and muscle progenitor cell (MPC) population. MPC transplantation has the potential to be a novel therapy for treatment of muscle dysfunction due to aging or injury, but has not shown significant clinical efficacy to date. The goal of this research was to use a rat model of skeletal muscle injury to examine the differential effects of age on MPC survival, differentiation, and tissue regeneration after transplantation. Fluorescently labeled MPCs, derived from young (YMPCs) and adult (AMPCs) donor rats, were transplanted in the injured tibialis anterior (TA) muscles of young, adult, and aged rats. Our results demonstrated that integration and maturation of YMPCs into mature myofibers were dependent on the age of the host microenvironment; whereas, the integration and maturation of AMPCs were less dependent on age and more dependent on intrinsic cellular changes. These data suggest that the age of both the host microenvironment and cells for transplantation must be considered when designing cell therapy regimens.