Intravenous Injection of Sodium Hyaluronate Diminishes Basal Inflammatory Gene Expression in Equine Skeletal Muscle.

Following strenuous exercise, skeletal muscle experiences an acute inflammatory state that initiates the repair process. Systemic hyaluronic acid (HA) is injected to horses routinely as a joint anti-inflammatory. To gain insight into the effects of HA on skeletal muscle, adult Thoroughbred geldings (n = 6) were injected with a commercial HA product weekly for 3 weeks prior to performing a submaximal exercise test. Gluteal muscle (GM) biopsies were obtained before and 1 h after exercise for gene expression analysis and HA localization. The results from RNA sequencing demonstrate differences in gene expression between non-injected controls (CON; n = 6) and HA horses. Prior to exercise, HA horses contained fewer (p < 0.05) transcripts associated with leukocyte activity and cytokine production than CON. The performance of exercise resulted in the upregulation (p < 0.05) of several cytokine genes and their signaling intermediates, indicating that HA does not suppress the normal inflammatory response to exercise. The transcript abundance for marker genes of neutrophils (NCF2) and macrophages (CD163) was greater (p < 0.05) post-exercise and was unaffected by HA injection. The anti-inflammatory effects of HA on muscle are indirect as no differences (p > 0.05) in the relative amount of the macromolecule was observed between the CON and HA fiber extracellular matrix (ECM). However, exercise tended (p = 0.10) to cause an increase in ECM size suggestive of muscle damage and remodeling. The finding was supported by the increased (p < 0.05) expression of CTGF, TGFß1, MMP9, TIMP4 and Col4A1. Collectively, the results validate HA as an anti-inflammatory aid that does not disrupt the normal post-exercise muscle repair process.

A Carnitine-Containing Product Improves Aspects of Post-Exercise Recovery in Adult Horses.

Strenuous exercise can cause tissue damage, leading to an extended recovery period. To counteract delayed post-exercise recovery, a commercial product containing L-carnitine (AID) was tested in adult horses performing consecutive exercise tests to exhaustion. Fit Thoroughbreds were administered an oral bolus of placebo (CON) or AID prior to performing an exercise test to exhaustion (D1). The heart rate (HR) and fetlock kinematics were captured throughout the exercise test. Blood was collected before, 10 min and 1, 4 and 6 h relative to exercise for the quantification of cytokine (IL1ß, IL8, IL10, TNFa) gene expression and lactate concentration. Horses performed a second exercise test 48 h later (D2), with all biochemical and physiological measures repeated. The results demonstrate that the horses receiving AID retained a greater (p < 0.05) amount of flexion in the front fetlock on D2 than the horses given CON. The horses presented a reduced (p < 0.05) rate of HR decline on D2 compared to that on D1. The expression of IL1ß, IL8 and IL10 increased at 1 h post-exercise on D1 and returned to baseline by 6 h; the cytokine expression pattern was not duplicated on D2. These results provide evidence of disrupted cytokine expression, HR recovery and joint mobility in response to consecutive bouts of exhaustive exercise. Importantly, AID may accelerate recovery through an undetermined mechanism.

The initial delay to mitotic activity in primary cultures of equine satellite cells is reduced by combinations of growth factors.

Satellite cell (SC) activation is defined as the time frame during which the stem cell becomes poised to reenter G1 of the cell cycle. The growth factors and events leading to full mitotic activation in equine SCs remain largely unknown. Insulin-like growth factor I (IGF-I), hepatocyte growth factor (HGF), and fibroblast growth factor 2 (FGF2) are sequentially transcribed during the muscle repair and recovery period following strenuous exercise in adult horses. Expression of IGF-I occurs within 24 h of the postexercise recovery period suggesting it may affect early SC actions. As a first step, gluteus medius muscle cryosections from adult horses (n = 9) were examined for the presence of central nuclei (CN), a marker of SC addition to the fiber. Results demonstrate few CN fibers prior to exercise with a 3-fold increase (P = 0.05) 24 h postexercise. Cultures of SC (n = 4 isolates) were treated with 100 ng/mL IGF-I for varying times prior to measurement of myogenic events. Results demonstrate that IGF-I does not affect the initial lag period, proliferation, or subsequent differentiation of equine SC in vitro (P > 0.05). However, media containing a combination of IGF-I and 10 ng/mL FGF2 and 25 ng/mL HGF hastens (P < 0.05) the time to S-phase entry in fresh isolates of SCs. Media supplementation with optimal concentrations of FGF2, HGF, or a combination of HGF and FGF2 suppresses (P < 0.05) the percentage of myogenin immunopositive SCs to levels below that found in control- or IGF-I-treated SCs. These results provide new insight into the combinatorial roles growth factors play during equine SC myogenesis.

Satellite cells are the resident stem cells found within skeletal muscle. Following strenuous exercise, the cells become mitotically active to supply progenitors for muscle repair. The signals responsible for their exit from the dormant state are largely unknown. Hepatocyte growth factor (HGF), fibroblast growth factor 2 (FGF2), and insulin-like growth factor I (IGF-I) are located within the local environment postexercise suggesting their involvement in mitotic activation. Treatment of satellite cells in vitro with optimal concentrations of HGF, FGF2, or IGF-I did not affect transition into the cell cycle. By contrast, inclusion of all three growth factors in the media caused an increase in the numbers of activated satellite cells. The combination of factors suppressed expression of myogenin, the requisite transcriptional mediator of differentiation. Although IGF-I stimulates myogenin expression in other muscle cell types, a similar response was not observed in equine satellite cells. These results support a role for HGF, FGF2, and IGF-I during the initial postexercise repair period in horses.

Adapting a Bacterial Unknowns Project to Online Learning: Using Microsoft PowerPoint To Create an Unknowns Identification Simulation.

The COVID-19 pandemic forced institutions to move to online learning abruptly during the spring 2020 semester. As a result of this swift change, many microbiology laboratory courses chose to switch all in-class learning activities to simulations. To provide students with a remote bacterial unknowns identification project, we developed an unknowns simulation using Microsoft PowerPoint. This simulation provides students with an assignment that allows them to utilize their knowledge in a cumulative project while attending classes remotely. Because this simulation does not require an internet connection and can be performed on any device that is capable of running Microsoft PowerPoint, it provides an accessible and equitable option for students in different learning environments. In addition, the simulation format is flexible enough to be easily customized for any course or assessment style. We provide here details and examples of how to create an unknowns simulation using Microsoft PowerPoint. In addition, a full template and an example simulation are available for download on GitHub at https://github.com/drhodes-berry-college/BacterialUnknowsSimulation.