The effects of early mobilisation and immobilisation on the healing process following muscle injuries

Platelet-rich plasma enhances remodeling of combined gastrocnemius muscle and Achilles tendon injuries in rat model: Reducing fibrosis, modulating gene (MMP9, Bax, HMGB1, and IGF) expression, and restoring histopathological and ultrastructural changes

Muscle and tendon injuries are prevalent occurrences during sports activities. Platelet-rich plasma (PRP) is known for its rich content of factors essential for wound healing, inflammation reduction, and tissue repair. Despite its recognized benefits, limited information is available regarding PRP's effectiveness in addressing combined surgical injuries to the gastrocnemius muscle and Achilles tendon. The effects of PRP on muscle and tendon injury in rats were assessed through a set of biochemical markers, histopathological examinations, and immunohistochemistry analyses of muscular myogenin, desmin, and tendinous type I collagen. Additionally, mRNA expression levels of Matrix metalloproteinase-9 (MMP-9), Pro-apoptotic Bcl-2 Associated-X-protein (BAX), Insulin-like growth factor (IGF), and High mobility group box 1 protein (HMGB1) genes were evaluated. Induction of muscle and tendon injuries was associated with elevated levels of serum biomarkers such as C-reactive protein (CRP), Aspartate aminotransferase (AST), Lactate dehydrogenase A (LDH), and Creatine Kinase MB (CK-MB), delayed collagen fiber remodeling, and structural abnormalities in myofibrils. Furthermore, there was overexpression of MMP9, Bax, and HMGB1 genes, along with decreased expression of the IGF gene in this group. Treatment with PRP resulted in significant improvement of these reported findings, including enhanced collagen fiber remodeling, elevated levels of desmin and myogenin in muscle tissues, and increased expression of collagen type I in tendons. Additionally, PRP treatment led to reduced expression levels of MMP9, Bax, and HMGB1 genes, while the expression of the IGF gene increased. Overall, PRP treatment demonstrated substantial enhancement of the healing process in both muscle and tendon tissues in a surgical model of gastrocnemius skeletal muscle and Achilles tendon-induced injury. These findings suggest that PRP therapy may offer advantages in the treatment of physical-related injuries.

Impaired skeletal muscle regeneration in diabetes: From cellular and molecular mechanisms to novel treatments

Diabetes represents a major public health concern with a considerable impact on human life and healthcare expenditures. It is now well established that diabetes is characterized by a severe skeletal muscle pathology that limits functional capacity and quality of life. Increasing evidence indicates that diabetes is also one of the most prevalent disorders characterized by impaired skeletal muscle regeneration, yet underlying mechanisms and therapeutic treatments remain poorly established. In this review, we describe the cellular and molecular alterations currently known to occur during skeletal muscle regeneration in people with diabetes and animal models of diabetes, including its associated comorbidities, e.g., obesity, hyperinsulinemia, and insulin resistance. We describe the role of myogenic and non-myogenic cell types on muscle regeneration in conditions with or without diabetes. Therapies for skeletal muscle regeneration and gaps in our knowledge are also discussed, while proposing future directions for the field.

Accurate Spatio-Temporal Delivery of Nitric Oxide Facilitates the Programmable Repair of Avascular Dense Connective Tissues Injury

Avascular dense connective tissues (e.g., the annulus fibrosus (AF) rupture, the meniscus tear, and tendons and ligaments injury) repair remains a challenge due to the "biological barrier" that hinders traditional drug permeation and limits self-healing of the injured tissue. Here, accurate delivery of nitric oxide (NO) to penetrate the "AF biological barrier" is achieved thereby enabling programmable AF repair. NO-loaded BioMOFs are synthesized and mixed in a modified polyvinyl alcohol and PCL-composited electrospun fiber membrane with excellent reactive oxygen species-responsive capability (LN@PM). The results show that LN@PM could respond to the high oxidative stress environment at the injured tissue and realize continuous and substantial NO release. Based on low molecular weight and lipophilicity, NO could penetrate through the "biological barrier" for accurate AF drug delivery. Moreover, the dynamic characteristics of the LN@PM reaction can be matched with the pathological microenvironment to initiate programmable tissue repair including sequential remodeling microenvironment, reprogramming the immune environment, and finally promoting tissue regeneration. This tailored programmable treatment strategy that matches the pathological repair process significantly repairs AF, ultimately alleviating intervertebral disc degeneration. This study highlights a promising approach for avascular dense connective tissue treatment through intelligent NO release, effectively overcoming "AF biological barriers" and programmable treatment.

Is Postoperative Splinting Advantageous After Upper Extremity Fracture Surgery? Results From the Arm Splint Pain Improvement Research Experiment

OBJECTIVES

The authors report no conflict of interest.To determine if short-term immobilization with a rigid long arm plaster elbow splint after surgery of the arm, elbow, or forearm results in superior outcomes compared with a soft dressing with early motion.

METHODS

DESIGN

Prospective Randomized Control Trial.

SETTING

Academic Medical Center.

PATIENT SELECTION CRITERIA

Patients undergoing operative treatment for a mid-diaphysis or distal humerus, elbow, or forearm fracture were consented and randomized according to the study protocol for postoperative application of a rigid elbow splint (10-14 days in a plaster Sugar Tong Splint for forearm fracture or a Long Arm plaster Splint for 10-14 for all others) or soft dressing and allowing immediate free range of elbow and wrist motion (range of motion [ROM]).

OUTCOME MEASURES AND COMPARISONS

Self-reported pain (visual analog score or VAS), Healthscale (0-100, 100 denoting excellent health), and physical function (EuroQol 5 Dimension or EQ-5D) surveyed on postoperative days 1-5 and 14 were compared between groups. Patient-reported pain score (0-10, 10 denoting highest satisfaction) at week 6, time to fracture union, ultimate disabilities of the arm, shoulder, and hand score, and elbow ROM were also collected for analysis. Incidence of complications were assessed.

RESULTS

Hundred patients (38 men to 62 women with a mean age of 55.7 years) were included. Over the first 5 days and again at postop day 14, the splint cohort reported a higher "Healthscale" from 0 to 100 than the nonsplint group on all study days ( P = 0.041). There was no difference in reported pain between the 2 study groups over the same interval ( P = 0.161 and 0.338 for least and worst pain, respectively), and both groups reported similar rates of treatment satisfaction ( P = 0.30). Physical function ( P = 0.67) and rates of wound problems ( P = 0.27) were similar. Additionally, the mean time to fracture healing was similar for the splint and control groups (4.6 ± 2.8 vs. 4.0 ± 2.2 months, P = 0.34). Ultimate elbow ROM was similar between the study groups ( P = 0.48, P = 0.49, P = 0.61, and P = 0.51 for elbow extension, flexion, pronation, and supination, respectively).

CONCLUSIONS

Free range of elbow motion without splinting produced similar results compared with elbow immobilization after surgical intervention for a fracture to the humerus, elbow, and forearm. There was no difference in patient-reported pain outcomes, wound problems, or elbow ROM. Immobilized patients reported slightly higher "healthscale" ratings than nonsplinted patients and, however, reported similar rates of satisfaction. Both treatment strategies are acceptable after upper extremity fracture surgery.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

A Comprehensive Review of Muscle-Tendon Junction: Structure, Function, Injury and Repair

The muscle-tendon junction (MTJ) is a highly specific tissue interface where the muscle's fascia intersects with the extracellular matrix of the tendon. The MTJ functions as the particular structure facilitating the transmission of force from contractive muscle fibers to the skeletal system, enabling movement. Considering that the MTJ is continuously exposed to constant mechanical forces during physical activity, it is susceptible to injuries. Ruptures at the MTJ often accompany damage to both tendon and muscle tissues. In this review, we attempt to provide a precise definition of the MTJ, describe its subtle structure in detail, and introduce therapeutic approaches related to MTJ tissue engineering. We hope that our detailed illustration of the MTJ and summary of the representative research achievements will help researchers gain a deeper understanding of the MTJ and inspire fresh insights and breakthroughs for future research.

Traumatic muscle injury

Traumatic muscle injury represents a collection of skeletal muscle pathologies caused by trauma to the muscle tissue and is defined as damage to the muscle tissue that can result in a functional deficit. Traumatic muscle injury can affect people across the lifespan and can result from high stresses and strains to skeletal muscle tissue, often due to muscle activation while the muscle is lengthening, resulting in indirect and non-contact muscle injuries (strains or ruptures), or from external impact, resulting in direct muscle injuries (contusion or laceration). At a microscopic level, muscle fibres can repair focal damage but must be completely regenerated after full myofibre necrosis. The diagnosis of muscle injury is based on patient history and physical examination. Imaging may be indicated to eliminate differential diagnoses. The management of muscle injury has changed within the past 5 years from initial rest, immobilization and (over)protection to early activation and progressive loading using an active approach. One challenge of muscle injury management is that numerous medical treatment options, such as medications and injections, are often used or proposed to try to accelerate muscle recovery despite very limited efficacy evidence. Another challenge is the prevention of muscle injury owing to the multifactorial and complex nature of this injury.

Human adipose-derived mesenchymal stem cells laden in gellan gum spongy-like hydrogels for volumetric muscle loss treatment

BACKGROUND

volumetric muscle loss (VML) is a traumatic massive loss of muscular tissue which frequently leads to amputation, limb loss, or lifetime disability. The current medical intervention is limited to autologous tissue transfer, which usually leads to non-functional tissue recovery. Tissue engineering holds a huge promise for functional recovery.

METHODS

in this work, we evaluated the potential of human adipose-derived mesenchymal stem cells (hASCs) pre-cultured in gellan gum based spongy-like hydrogels (SLHs).

RESULTS

in vitro, hASCs were spreading, proliferating, and releasing growth factors and cytokines (i.e. fibroblast growth factor, hepatocyte growth factor, insulin-like growth factor 1, interleukin-6 (IL-6), IL-8, IL-10, vascular endothelial growth factor) important for muscular regeneration. After implantation into a volumetric muscle loss (VML) mouse model, implants were degrading overtime, entirely integrating into the host between 4 and 8 weeks. In both SLH and SLH + hASCs defects, infiltrated cells were observed inside constructs associated with matrix deposition. Also, minimal collagen deposition was marginally observed around the constructs along both time-points. Neovascularization (CD31+vessels) and neoinnervation (β-III tubulin+bundles) were significantly detected in the SLH + hASCs group, in relation to the SHAM (empty lesion). A higher density ofα-SA+and MYH7+cells were found in the injury site among all different experimental groups, at both time-points, in relation to the SHAM. The levels ofα-SA, MyoD1, and myosin heavy chain proteins were moderately increased in the SLH + hASCs group after 4 weeks, and in the hASCs group after 8 weeks, in relation to the SHAM.

CONCLUSIONS

taken together, defects treated with hASCs-laden SLH promoted angiogenesis, neoinnervation, and the expression of myogenic proteins.

Traditional Chinese Medicine for Topical Treatment of Skeletal Muscle Injury

Muscle injuries are common musculoskeletal problems, but the pharmaceutical agent for muscle repair and healing is insufficient. Traditional Chinese Medicine (TCM) frequently uses topical treatments to treat muscle injuries, although scientific evidence supporting their efficacy is scarce. In this study, an in vitro assay was used to test the cytotoxicity of a topical TCM formula containing Carthami Flos, Dipsaci Radix, and Rhei Rhizoma (CDR). Then, a muscle contusion rat model was developed to investigate the in vivo effect and basic mechanisms underlying CDR on muscle regeneration. The in vitro assay illustrated that CDR was non-cytotoxic to immortalized rat myoblast culture and increased cell viability. Histological results demonstrated that the CDR treatment facilitated muscle repair by increasing the number of new muscle fibers and promoting muscle integrity. The CDR treatment also upregulated the expression of Pax7, MyoD and myogenin, as evidenced by an immunohistochemical study. A gene expression analysis indicated that the CDR treatment accelerated the regeneration and remodeling phases during muscle repair. This study demonstrated that topical CDR treatment was effective at facilitating muscle injury repair.

Brush-Induced Orientation of Collagen Fibers in Layer-by-Layer Nanofilms: A Simple Method for the Development of Human Muscle Fibers

The engineering of skeletal muscle tissue, a highly organized structure of myotubes, is promising for the treatment of muscle injuries and muscle diseases, for replacement, or for pharmacology research. Muscle tissue development involves differentiation of myoblasts into myotubes with parallel orientation, to ultimately form aligned myofibers, which is challenging to achieve on flat surfaces. In this work, we designed hydrogen-bonded tannic acid/collagen layer-by-layer (TA/COL LbL) nanofilms using a simple brushing method to address this issue. In comparison to films obtained by dipping, brushed TA/COL films showed oriented COL fibers of 60 nm diameter along the brushing direction. Built at acidic pH due to COL solubility, TA/COL films released TA in physiological conditions with a minor loss of thickness. After characterization of COL fibers' orientation, human myoblasts (C25CL48) were seeded on the oriented TA/COL film, ended by COL. After 12 days in a differentiation medium without any other supplement, human myoblasts were able to align on brushed TA/COL films and to differentiate into long aligned myotubes (from hundreds of μm up to 1.7 mm length) thanks to two distinct properties: (i) the orientation of COL fibers guiding myoblasts' alignment and (ii) the TA release favoring the differentiation. This simple and potent brushing process allows the development of anisotropic tissues in vitro which can be used for studies of drug discovery and screening or the replacement of damaged tissue.

Mice from lines selectively bred for voluntary exercise are not more resistant to muscle injury caused by either contusion or wheel running

Muscle injury can be caused by strenuous exercise, repetitive tasks or external forces. Populations that have experienced selection for high locomotor activity may have evolutionary adaptations that resist exercise-induced injury and/or enhance the ability to cope with injury. We tested this hypothesis with an experiment in which mice are bred for high voluntary wheel running. Mice from four high runner lines run ~three times more daily distance than those from four non-selected control lines. To test recovery from injury by external forces, mice experienced contusion via weight drop on the calf. After injury, running distance and speed were reduced in high runner but not control lines, suggesting that the ability of control mice to run exceeds their motivation. To test effects of injury from exercise, mice were housed with/without wheels for six days, then trunk blood was collected and muscles evaluated for injury and regeneration. Both high runner and control mice with wheels had increased histological indicators of injury in the soleus, and increased indicators of regeneration in the plantaris. High runner mice had relatively more central nuclei (regeneration indicator) than control in the soleus, regardless of wheel access. The subset of high runner mice with the mini-muscle phenotype (characterized by greatly reduced muscle mass and type IIb fibers) had lower plasma creatine kinase (indicator of muscle injury), more markers of injury in the deep gastrocnemius, and more markers of regeneration in the deep and superficial gastrocnemius than normal-muscled individuals. Contrary to our expectations, high runner mice were not more resistant to either type of injury.

Isotonic and Isometric Exercise Interventions Improve the Hamstring Muscles’ Strength and Flexibility: A Narrative Review

Background: Hamstring weakness has been associated with an increased risk of hamstring strain, a common sports injury that occurs when athletes perform actions such as quick sprints. The hamstring complex comprises three distinct muscles: the long and short heads of the bicep femoris, the semimembranosus, and the semitendinosus. Methods: The researchers collected the data from different electronic databases: PubMed, Google Scholar, and the Web of Science. Results: Many studies have been conducted on the numerous benefits of hamstring strength, in terms of athletic performance and injury prevention. Isotonic and isometric exercises are commonly used to improve hamstring strength, with each exercise type having a unique effect on the hamstring muscles. Isotonic exercise improves the muscles’ strength, increasing their ability to resist any force, while isometric training increases strength and the muscles’ ability to produce power by changing the muscle length. Conclusions: These exercises, when performed at low intensity, but with high repetition, can be used by the healthy general population to prepare for training and daily exercise. This can improve hamstring muscle strength and flexibility, leading to enhanced performance and reduced injury risk.

Effects of assistive insole feedback training on immediate and multi-day partial weight bearing retention during walking: A pilot study

BACKGROUND

Adherence to partial weight bearing (PWB) plays a crucial role in early rehabilitation and motor control. Dynamic biofeedback insole systems provide a supportive function on immediate PWB adherence, while important long-term retention effects and potential advantages to a conventional static training remain unknown.

RESEARCH QUESTION

Is acoustic insole feedback training effective for the retention of prescribed PWB adherence and is there any advantage relative to static training using a conventional bathroom scale? Methods Twenty-four volunteers were randomized into two groups receiving biofeedback training (N = 12) via a mobile insole system (Loadsol®) or conventional training using a bathroom scale (N = 12). After initial PWB training (20 kg) of one randomized leg, the immediate and one-week retention effects were analysed using mean and maximum load (N) and overload rate (%). Statistical analysis was performed using a two-way repeated measures ANOVA with post-hoc pairwise comparisons (p < 0.05).

RESULTS

A significantly (p < 0.001) improved immediate and long-term PWB adherence was found for the insole feedback group during walking. A significant (p < 0.001) reduction of the overload rate by 86% was found for the insole feedback group when compared to the conventional training group after one week. Significant (p < 0.01) reductions by 51% and 46% was also found for the mean and maximum load in the insole feedback group when compared to the conventional training group.

SIGNIFICANCE

The use of insole feedback systems can serve as a viable tool to become familiar with PWB and to provide optimal retention of specified loads. Therefore, such systems serve as an advantageous training intervention to maintain a prescribed PWB during locomotion.

Lesão muscular: Fisiopatologia, diagnóstico e tratamento

O tecido muscular esquelético possui a maior massa do corpo humano, correspondendo a 45% do peso total. As lesões musculares podem ser causadas por contusões, estiramentos ou lacerações. A atual classificação separa as lesões entre leves, moderadas e graves. Os sinais e sintomas das lesões grau I são edema e desconforto; grau II, perda de função, gap e equimose eventual; grau III, rotura completa, dor intensa e hematoma extenso. O diagnóstico pode ser confirmado por ultrassom (dinâmico e barato, porém examinador-dependente); e ressonância magnética (RM) (maior definição anatômica). A fase inicial do tratamento se resume à proteção, ao repouso, ao uso otimizado do membro afetado e crioterapia. Anti-inflamatórios não hormonais (AINHs), ultrassom terapêutico, fortalecimento e alongamento após a fase inicial e amplitudes de movimento sem dor são utilizados no tratamento clínico. Já o cirúrgico possui indicações precisas: drenagem do hematoma, reinserção e reforço musculotendíneos.

Enhancement of myogenic potential of muscle progenitor cells and muscle healing during pregnancy

The decline of muscle regenerative potential with age has been attributed to a diminished responsiveness of muscle progenitor cells (MPCs). Heterochronic parabiosis has been used as a model to study the effects of aging on stem cells and their niches. These studies have demonstrated that, by exposing old mice to a young systemic environment, aged progenitor cells can be rejuvenated. One interesting idea is that pregnancy represents a unique biological model of a naturally shared circulatory system between developing and mature organisms. To test this hypothesis, we evaluated the muscle regeneration potential of pregnant mice using a cardiotoxin (CTX) injury mouse model. Our results indicate that the pregnant mice demonstrate accelerated muscle healing compared to nonpregnant control mice following muscle injury based on improved muscle histology, superior muscle regeneration, and a reduction in inflammation and necrosis. Additionally, we found that MPCs isolated from pregnant mice display a significant improvement of myogenic differentiation capacity in vitro and muscle regeneration in vivo when compared to the MPCs from nonpregnant mice. Furthermore, MPCs from nonpregnant mice display enhanced myogenic capacity when cultured in the presence of serum obtained from pregnant mice. Our proteomics data from these studies provides potential therapeutic targets to enhance the myogenic potential of progenitor cells and muscle repair.

Long non-coding RNA MFAT1 promotes skeletal muscle fibrosis by modulating the miR-135a-5p-Tgfbr2/Smad4 axis as a ceRNA

Fibrosis after skeletal muscle injury is common in sports and can cause irreversible damage to the biomechanical properties of skeletal muscle. Long non-coding RNAs (lncRNAs) have been validated to act as important modulators in the fibrosis of various organs. Here, we reported a novel lncRNA (the skeletal muscle fibrosis-associated transcript 1, lnc-MFAT1), which was highly expressed in skeletal muscle fibrosis. We demonstrate that lnc-MFAT1 knockdown can reduce TGFβ-induced fibrosis in vitro and attenuate skeletal muscle fibrosis after acute contusion in mice. Further study showed that lnc-MFAT1 acted as a competitive endogenous RNA of miR-135a-5p. Besides, the miR-135a-5p inhibition obviously promoted TGFβ-induced fibrosis in vitro via enhancing its target genes Tgfbr2/Smad4. Moreover, we discovered that lnc-MFAT1 regulates Tgfbr2/Smad4 expression by sponging miR-135a-5p to exert competing endogenous RNA function, resulting in TGFβ pathway activation. In conclusion, our study identified a crucial role of lnc-MFAT1-miR-135a-Tgfbr2/Smad4 axis in skeletal muscle fibrosis, providing a promising treatment option against skeletal muscle fibrosis.

Muscle Precursor Cells Enhance Functional Muscle Recovery and Show Synergistic Effects With Postinjury Treadmill Exercise in a Muscle Injury Model in Rats

BACKGROUND

Skeletal muscle injuries represent a major concern in sports medicine. Cell therapy has emerged as a promising therapeutic strategy for muscle injuries, although the preclinical data are still inconclusive and the potential clinical use of cell therapy has not yet been established.

PURPOSE

To evaluate the effects of muscle precursor cells (MPCs) on muscle healing in a small animal model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 27 rats were used in the study. MPCs were isolated from rat (n = 3) medial gastrocnemius muscles and expanded in primary culture. Skeletal muscle injury was induced in 24 rats, and the animals were assigned to 3 groups. At 36 hours after injury, animals received treatment based on a single ultrasound-guided MPC (10⁵ cells) injection (Cells group) or MPC injection in combination with 2 weeks of daily exercise training (Cells+Exercise group). Animals receiving intramuscular vehicle injection were used as controls (Vehicle group). Muscle force was determined 2 weeks after muscle injury, and muscles were collected for histological and immunofluorescence evaluation.

RESULTS

Red fluorescence-labeled MPCs were successfully transplanted in the site of the injury by ultrasound-guided injection and were localized in the injured area after 2 weeks. Transplanted MPCs participated in the formation of regenerating muscle fibers as corroborated by the co-localization of red fluorescence with developmental myosin heavy chain (dMHC)-positive myofibers by immunofluorescence analysis. A strong beneficial effect on muscle force recovery was detected in the Cells and Cells+Exercise groups (102.6% ± 4.0% and 101.5% ± 8.5% of maximum tetanus force of the injured vs healthy contralateral muscle, respectively) compared with the Vehicle group (78.2% ± 5.1%). Both Cells and Cells+Exercise treatments stimulated the growth of newly formed regenerating muscles fibers, as determined by the increase in myofiber cross-sectional area (612.3 ± 21.4 µm² and 686.0 ± 11.6 µm², respectively) compared with the Vehicle group (247.5 ± 10.7 µm²), which was accompanied by a significant reduction of intramuscular fibrosis in Cells and Cells+Exercise treated animals (24.2% ± 1.3% and 26.0% ± 1.9% of collagen type I deposition, respectively) with respect to control animals (40.9% ± 4.1% in the Vehicle group). MPC treatment induced a robust acceleration of the muscle healing process as demonstrated by the decreased number of dMHC-positive regenerating myofibers (enhanced replacement of developmental myosin isoform by mature myosin isoforms) (4.3% ± 2.6% and 4.1% ± 1.5% in the Cells and Cells+Exercise groups, respectively) compared with the Vehicle group (14.8% ± 13.9%).

CONCLUSION

Single intramuscular administration of MPCs improved histological outcome and force recovery of the injured skeletal muscle in a rat injury model that imitates sports-related muscle injuries. Cell therapy showed a synergistic effect when combined with an early active rehabilitation protocol in rats, which suggests that a combination of treatments can generate novel therapeutic strategies for the treatment of human skeletal muscle injuries.

CLINICAL RELEVANCE

Our study demonstrates the strong beneficial effect of MPC transplant and the synergistic effect when the cell therapy is combined with an early active rehabilitation protocol for muscle recovery in rats; this finding opens new avenues for the development of effective therapeutic strategies for muscle healing and clinical trials in athletes undergoing MPC transplant and rehabilitation protocols.

Skeletal muscle healing by M1-like macrophages produced by transient expression of exogenous GM-CSF

Background

After traumatic skeletal muscle injury, muscle healing is often incomplete and produces extensive fibrosis. The sequence of M1 and M2 macrophage accumulation and the duration of each subtype in the injured area may help to direct the relative extent of fibrogenesis and myogenesis during healing. We hypothesized that increasing the number of M1 macrophages early after traumatic muscle injury would produce more cellular and molecular substrates for myogenesis and fewer substrates for fibrosis, leading to better muscle healing.

Methods

To test this hypothesis, we transfected skeletal muscle with a plasmid vector to transiently express GM-CSF shortly after injury to drive the polarization of macrophages towards the M1 subset. C57BL/6 mouse tibialis anterior (TA) muscles were injured by contusion and electroporated with uP-mGM, which is a plasmid vector that transiently expresses GM-CSF. Myogenesis, angiogenesis, and fibrosis were evaluated by histology, immunohistochemistry, and RT-qPCR; subpopulations of macrophages by flow cytometry; and muscle functioning by the maximum running speed on the treadmill and the recovery of muscle mass.

Results

Muscle injury increased the number of local M1-like macrophages and decreased the number of M2-like macrophages on day 4, and uP-mGM treatment enhanced this variation. uP-mGM treatment decreased TGF-β1 protein expression on day 4, and the Sirius Red-positive area decreased from 35.93 ± 15.45% (no treatment) to 2.9% ± 6.5% (p < 0.01) on day 30. uP-mGM electroporation also increased Hgf, Hif1α, and Mtor gene expression; arteriole density; and muscle fiber number during regeneration. The improvement in the quality of the muscle tissue after treatment with uP-mGM affected the increase in the TA muscle mass and the maximum running speed on a treadmill.

Conclusion

Collectively, our data show that increasing the number of M1-like macrophages immediately after traumatic muscle injury promotes muscle recovery with less fibrosis, and this can be achieved by the transient expression of GM-CSF.

Effects of testosterone suppression, hindlimb immobilization, and recovery on [3H]ouabain binding site content and Na+, K+-ATPase isoforms in rat soleus muscle

We investigated the effects of testosterone suppression, hindlimb immobilization, and recovery on skeletal muscle Na⁺,K⁺-ATPase (NKA), measured via [³H]ouabain binding site content (OB) and NKA isoform abundances (α_1-3, β_1-2). Male rats underwent castration or sham surgery plus 7 days of rest, 10 days of unilateral immobilization (cast), and 14 days of recovery, with soleus muscles obtained at each time from cast and noncast legs. Testosterone reduction did not modify OB or NKA isoforms in nonimmobilized control muscles. With sham surgery, OB was lower after immobilization in the cast leg than in both the noncast leg (-26%, P = 0.023) and the nonimmobilized control (-34%, P = 0.001), but OB subsequently recovered. With castration, OB was lower after immobilization in the cast leg than in the nonimmobilized control (-34%, P = 0.001), and remained depressed at recovery (-34%, P = 0.001). NKA isoforms did not differ after immobilization or recovery in the sham group. After castration, α₂ in the cast leg was ~60% lower than in the noncast leg (P = 0.004) and nonimmobilized control (P = 0.004) and after recovery remained lower than the nonimmobilized control (-42%, P = 0.039). After immobilization, β₁ was lower in the cast than the noncast leg (-26%, P = 0.018), with β₂ lower in the cast leg than in the noncast leg (-71%, P = 0.004) and nonimmobilized control (-65%, P = 0.012). No differences existed for α₁ or α₃. Thus, both OB and α₂ decreased after immobilization and recovery in the castration group, with α₂, β₁, and β₂ isoform abundances decreased with immobilization compared with the sham group. Therefore, testosterone suppression in rats impaired restoration of immobilization-induced lowered number of functional NKA and α₂ isoforms in soleus muscle.NEW & NOTEWORTHY: The Na⁺,K⁺-ATPase (NKA) is vital in muscle excitability and function. In rats, immobilization depressed soleus muscle NKA, with declines in [³H]ouabain binding, which was restored after 14 days recovery. After testosterone suppression by castration, immobilization depressed [³H]ouabain binding, depressed α₂, β₁, and β₂ isoforms, and abolished subsequent recovery in [³H]ouabain binding and α₂ isoforms. This may have implications for functional recovery for inactive men with lowered testosterone levels, such as in prostate cancer or aging.

Rehabilitation of companion animals following orthopaedic surgery

Physical therapy and rehabilitation following orthopaedic surgery in companion animals have become more common and new advancements in this field have been made in recent years. Surgery alone may not return the animal to its previous physical activity or work-related tasks, whether due to concurrent soft tissue trauma, arthrogenic muscle inhibition or osteoarthritis. Rehabilitation therapies following surgery can restore function as well as strength, coordination and balance. Many simple techniques such as cryotherapy and passive range of motion exercises have been shown to improve outcomes following musculoskeletal procedures and may help restore function as well as reduce pain and facilitate healing. Some techniques are more useful during different stages in order to achieve optimum tissue healing and recovery of function. During the first 72 hours, rehabilitation should focus on reduction of inflammation and pain, maintaining joint nutrition and range of motion, and stimulating vascularisation and healing; and may include cryotherapy, passive range of motion exercises, massage and therapeutic exercises. Following the initial recovery period, the goals of rehabilitation also include restoring strength, balance and normal gait patterns, as well as recovery of function. During this period the focus of therapy may shift toward therapeutic exercises, aquatic therapy and increasing activity in the animal. Therapeutic modalities such as neuromuscular electrical stimulation, photobiomodulation (laser therapy), therapeutic ultrasound and extracorporeal shock wave therapy have been reported to reduce pain and inflammation, enhance healing and reduce recovery time in the early and late stages following orthopaedic surgery.

Rectus femoris myotendinous lesion treated with PRP: a case report

BACKGROUND AND AIM OF WORK

Musculoskeletal injuries are the most common cause of severe, chronic pain and physical disability for the majority of all sport-related injuries. Platelet-rich plasma is being used more frequently to promote healing of muscle injuries. We report a case of 39 years old non professional soccer player who came to our attention for a quadriceps muscle pain onset after kicking the ball during a match.

METHODS

Clinical and instrumental evaluation revealed a myotendinous junction rupture of the rectus femoris with retraction of 1.5 cm from the anterior inferior iliac spine. We decided to treat the patient with PRP ultrasound guided injections and a specific rehabilitation protocol.

RESULTS

Clinical evaluation 45 days following the end of the treatment showed the resolution of the pain and the full recovery of strength and range of motion. Muscle healing was documented by magnetic resonance imaging.

CONCLUSIONS

Even if the role of PRP in muscle injury is not still clear, the result observed confirms that it could be used in the treatment of muscle lesions.

Treatment of Acute Thigh Muscle Injury with or without Hematoma Puncture in Athletes

Objectives

To correlate the mean time of return of athletes to sport after acute injury of the thigh muscle with hematoma that was punctured or not.

Methods

Study based on clinical intervention, controlled and non-randomized with 20 amateur and professional athletes, divided into moderate and total or subtotal thighs lesions, according with the Munich Consensus Statement. Nine athletes were included in the intervention group and 11 athletes in the control group. In the intervention group, the athletes were submitted to a puncture of the hematoma, associated to physical therapy; the control group did only physical therapy. The variable mean time of return to sport was analyzed using the Mann-Whitney test and a significance level of 5% ( p  < 0.05; 95% confidence interval [CI]) was established.

Results

The mean group was composed mostly of men, eight of them were amateur athletes. There were three women, two of whom were amateur athletes. The average age of participants was 34.70 ± 12.79 years. There were 13 patients with posterior thigh lesions, 5 with anterior lesions and two with adductor lesions. Considering all injuries, the mean time of return to sport was of 48.50 ± 27.50 days in the intervention group. In the control group, this period was of 102.09 ± 52.02 days, showing a statistically significant difference between them ( p  = 0.022).

Conclusion

In the present study, hematoma drainage in athletes with moderate and total or subtotal muscle injuries associated with hematomas decreased their return time to sport.

Cell therapy to improve regeneration of skeletal muscle injuries

Diseases that jeopardize the musculoskeletal system and cause chronic impairment are prevalent throughout the Western world. In Germany alone, ~1.8 million patients suffer from these diseases annually, and medical expenses have been reported to reach 34.2bn Euros. Although musculoskeletal disorders are seldom fatal, they compromise quality of life and diminish functional capacity. For example, musculoskeletal disorders incur an annual loss of over 0.8 million workforce years to the German economy. Among these diseases, traumatic skeletal muscle injuries are especially problematic because they can occur owing to a variety of causes and are very challenging to treat. In contrast to chronic muscle diseases such as dystrophy, sarcopenia, or cachexia, traumatic muscle injuries inflict damage to localized muscle groups. Although minor muscle trauma heals without severe consequences, no reliable clinical strategy exists to prevent excessive fibrosis or fatty degeneration, both of which occur after severe traumatic injury and contribute to muscle degeneration and dysfunction. Of the many proposed strategies, cell-based approaches have shown the most promising results in numerous pre-clinical studies and have demonstrated success in the handful of clinical trials performed so far. A number of myogenic and non-myogenic cell types benefit muscle healing, either by directly participating in new tissue formation or by stimulating the endogenous processes of muscle repair. These cell types operate via distinct modes of action, and they demonstrate varying levels of feasibility for muscle regeneration depending, to an extent, on the muscle injury model used. While in some models the injury naturally resolves over time, other models have been developed to recapitulate the peculiarities of real-life injuries and therefore mimic the structural and functional impairment observed in humans. Existing limitations of cell therapy approaches include issues related to autologous harvesting, expansion and sorting protocols, optimal dosage, and viability after transplantation. Several clinical trials have been performed to treat skeletal muscle injuries using myogenic progenitor cells or multipotent stromal cells, with promising outcomes. Recent improvements in our understanding of cell behaviour and the mechanistic basis for their modes of action have led to a new paradigm in cell therapies where physical, chemical, and signalling cues presented through biomaterials can instruct cells and enhance their regenerative capacity. Altogether, these studies and experiences provide a positive outlook on future opportunities towards innovative cell-based solutions for treating traumatic muscle injuries-a so far unmet clinical need.

A Comparison of Barbed Suture Versus Traditional Techniques for Muscle Belly Repair

BACKGROUND

The use of barbed sutures in wound closure and tendon repair has been previously been studied with improved results over traditional suture material. We examine the use of barbed suture in muscle belly repair in a custom configuration, comparing it with traditional configurations and a control.

METHODS

Twenty-five matched porcine psoas muscles were assigned to 5 different test groups: Mason-Allen with #1 Ethibond, Figure of Eight Allen with #1 Ethibond, Modified Kessler with #1 Ethibond, Custom Configuration with #2 Barbed PDS, Custom Configuration with #1 Ethibond. Repair was performed on the cut edge of muscle, with the free end of the suture anchored to a fixed base, forming a single-sided repair. An Instron 8874 tensiometer was used to linearly distract the repair to failure at 1 mm/s after 1 N preload. Five samples of each group were run, comparing load to failure and distraction at 10 N.

RESULTS

Repair with barbed suture in custom configuration had statistically significantly greater load to failure than all other methods. It also showed statistically significant less displacement at 10 N of force than all other methods of repair except the Mason-Allen repair with #1 Ethibond. Mode of failure for traditional techniques was suture pull-through with tissue loss. Failure with barbed suture was through suture pullout without tissue loss.

CONCLUSIONS

Custom configuration with a barbed suture increases the load to failure and decreases displacement of the repair site at 10 N of force. In addition, when the suture does pull out, it does so with minimal tissue loss.

Electroactive biomaterial surface engineering effects on muscle cells differentiation

Even though skeletal muscle cells can naturally regenerate as a response to insignificant tissue damages, more severe injuries can cause irreversible loss of muscle cells mass and/or function. Until now, cell therapies are not a good approach to treat those injuries. Biomaterials such as poly(vinylidene fluoride), PVDF, can improve muscle regeneration by presenting physical cues to muscle cells that mimic the natural regeneration environment. In this way, the ferroelectric and piezoelectric properties of PVDF offer new opportunities for skeletal muscle tissue engineering once the piezoelectricity is an electromechanical effect that can be used to provide electrical signals to the cells, upon mechanical solicitations, similar to the ones found in several body tissues. Thus, previous to dynamic experiments, it is important to determine how the surface properties of the material, both in terms of the poling state (positive or negative net surface charge) and of the morphology (films or fibers) influence myoblast differentiation. It was observed that PVDF promotes myogenic differentiation of C2C12 cells as evidenced by quantitative analysis of myotube fusion, maturation index, length, diameter and number. Charged surfaces improve the fusion of muscle cells into differentiated myotubes, as demonstrated by fusion and maturation index values higher than the control samples. Finally, the use of random and oriented β-PVDF electrospun fibers scaffolds has revealed differences in cell morphology. Contrary to the randomly oriented fibers, oriented PVDF electrospun fibers have promoted the alignment of the cells. It is thus demonstrated that the use of this electroactive polymer represents a suitable approach for the development of electroactive microenvironments for effective muscle tissue engineering.

The Role of Pelvic Floor Muscle Training in the Conservative and Surgical Management of Female Stress Urinary Incontinence: Does the Strength of the Pelvic Floor Muscles Matter?

The purpose of this review is to provide an in-depth overview of the role of pelvic floor muscle (PFM) training in the management of stress urinary incontinence (SUI). The definition, epidemiology, and pathogenesis of SUI are described. We review the anatomy of the PFM and the importance of PFM strength in maintaining urinary continence and establishing normal voiding function. A brief description of the surgical options currently available for SUI and the existing data regarding the role of perioperative PFM training for SUI are included. Critical research questions to better evaluate and assess PFM training during the perioperative period are proposed. Promising novel approaches in the treatment of SUI are also presented. This review is useful for physiatrists, urogynecologists, female urologists, and nurse practitioners who specialize in the management and treatment of women with SUI. LEVEL OF EVIDENCE: IV.

Considerations in the Diagnosis and Accelerated Return to Sport of a Professional Basketball Player With a Triceps Surae Injury: A Case Report

Study Design Case report. Background Acute injuries of the triceps surae and Achilles tendon are common in sports. Rupture of the plantaris tendon can be challenging to diagnose. There is limited evidence detailing the diagnosis, rehabilitation, and accelerated return to sport of elite professional basketball players who have sustained calf injuries. Case Description A 25-year-old male professional basketball player sustained an injury to his calf during a professional basketball game. This case report details the presumptive diagnosis, graduated progression of intervention, and return to play of a professional athlete with a likely isolated plantaris tendon tear. Outcomes The patient returned to postseason competition 10 days post injury. Objective measures were tracked throughout rehabilitation and compared to baseline assessments. Before returning to play, the athlete showed improvements beyond the minimal clinically important difference for calf girth (2 cm) and numeric pain-rating scale score (4 points, 0-10 scale). Functional testing was conducted that included the Y Balance Test lower quarter and the Functional Movement Screen, with results that exceeded or returned the athlete to preseason levels. Discussion This report details the case of a professional basketball player who returned to competitive play in an accelerated time frame following injury to his calf. Diagnosing a plantaris tendon rupture can be challenging, and anatomical variations of this muscle should be considered. It was demonstrated in this case that physical therapy rehabilitation was helpful in making a treatment-based clinical diagnosis when imaging was unclear. Level of Evidence Therapy, level 5. J Orthop Sports Phys Ther 2018;48(5):388-397. Epub 6 Apr 2018. doi:10.2519/jospt.2018.7192.

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

Regeneration of injured skeletal muscles is affected by fibrosis, which can be improved by the administration of angiotensin II (AngII) receptor (ATR) blockers in normotensive animals. However, the role of ATR in skeletal muscle fibrosis in hypertensive organisms has not been investigated yet. The tibialis anterior (TA) muscle of spontaneously hypertensive (SHR) and Wistar rats (WR) were lacerated and a lentivector encoding a microRNA targeting AngII receptor type 1 (At1) (Lv-mirAT1a) or control (Lv-mirCTL) was injected. The TA muscles were collected after 30 days to evaluate fibrosis by histology and gene expression by real-time quantitative PCR (RT-qPCR) and Western blot. SHR's myoblasts were analyzed by RT-qPCR, 48 h after transduction. In the SHR's TA, AT1 protein expression was 23.5-fold higher than in WR without injury, but no difference was observed in the angiotensin II receptor type 2 (AT2) protein expression. TA laceration followed by suture (LS) produced fibrosis in the SHR (23.3±8.5%) and WR (7.9±1.5%). Lv-mirAT1 treatment decreased At1 gene expression in 50% and reduced fibrosis to 7% 30 days after. RT-qPCR showed that reduction in At1 expression is due to downregulation of the At1a but not of the At1b. RT-qPCR of myoblasts from SHR transduced with Lv-mirAT1a showed downregulation of the Tgf-b1, Tgf-b2, Smad3, Col1a1, and Col3a1 genes by mirAT1a. In vivo and in vitro studies indicate that hypertension overproduces skeletal muscle fibrosis, and AngII-AT1a signaling is the main pathway of fibrosis in SHR. Moreover, muscle fibrosis can be treated specifically by in loco injection of Lv-mirAT1a without affecting other organs.

Effects of photobiomodulation therapy and topical non-steroidal anti-inflammatory drug on skeletal muscle injury induced by contusion in rats-part 2: biochemical aspects

Muscle injuries trigger an inflammatory process, releasing important biochemical markers for tissue regeneration. The use of non-steroidal anti-inflammatory drugs (NSAIDs) is the treatment of choice to promote pain relief due to muscle injury. NSAIDs exhibit several adverse effects and their efficacy is questionable. Photobiomodulation therapy (PBMT) has been demonstrated to effectively modulate inflammation induced from musculoskeletal disorders and may be used as an alternative to NSAIDs. Here, we assessed and compared the effects of different doses of PBMT and topical NSAIDs on biochemical parameters during an acute inflammatory process triggered by a controlled model of contusion-induced musculoskeletal injury in rats. Muscle injury was induced by trauma to the anterior tibial muscle of rats. After 1 h, rats were treated with PBMT (830 nm, continuous mode, 100 mW of power, 35.71 W/cm²; 1, 3, and 9 J; 10, 30, and 90 s) or diclofenac sodium (1 g). Our results demonstrated that PBMT, 1 J (35.7 J/cm²), 3 J (107.1 J/cm²), and 9 J (321.4 J/cm²) reduced the expression of tumor necrosis factor alpha (TNF-α) and cyclooxygenase-2 (COX-2) genes at all assessed times as compared to the injury and diclofenac groups (p < 0.05). The diclofenac group showed reduced levels of COX-2 only in relation to the injury group (p < 0.05). COX-2 protein expression remained unchanged with all therapies except with PBMT at a 3-J dose at 12 h (p < 0.05 compared to the injury group). In addition, PBMT (1, 3, and 9 J) effectively reduced levels of cytokines TNF-α, interleukin (IL)-1β, and IL-6 at all assessed times as compared to the injury and diclofenac groups (p < 0.05). Thus, PBMT at a 3-J dose was more effective than other doses of PBMT and topical NSAIDs in the modulation of the inflammatory process caused by muscle contusion injuries.

Circadian rhythms accelerate wound healing in female Siberian hamsters

Circadian rhythms (CRs) provide temporal regulation and coordination of numerous physiological traits, including immune function. CRs in multiple aspects of immune function are impaired in rodents that have been rendered circadian-arrhythmic through various methods. In Siberian hamsters, circadian arrhythmia can be induced by disruptive light treatments (DPS). Here we examined CRs in wound healing, and the effects of circadian disruption on wound healing in DPS-arrhythmic hamsters. Circadian entrained/rhythmic (RHYTH) and behaviorally-arrhythmic (ARR) female hamsters were administered a cutaneous wound either 3h after light onset (ZT03) or 2h after dark onset (ZT18); wound size was quantified daily using image analyses. Among RHYTH hamsters, ZT03 wounds healed faster than ZT18 wounds, whereas in ARR hamsters, circadian phase did not affect wound healing. In addition, wounds healed slower in ARR hamsters. The results document a clear CR in wound healing, and indicate that the mere presence of organismal circadian organization enhances this aspect of immune function. Faster wound healing in CR-competent hamsters may be mediated by CR-driven coordination of the temporal order of mechanisms (inflammation, leukocyte trafficking, tissue remodeling) underlying cutaneous wound healing.

The Combined Use of Losartan and Muscle-Derived Stem Cells Significantly Improves the Functional Recovery of Muscle in a Young Mouse Model of Contusion Injuries

BACKGROUND

Although muscle injuries tend to heal uneventfully in most cases, incomplete functional recovery commonly occurs as a result of scar tissue formation at the site of injury, even after treatment with muscle-derived stem cells (MDSCs).

HYPOTHESIS

The transplantation of MDSCs in the presence of a transforming growth factor β1 (TGF-β1) antagonist (losartan) would result in decreased scar tissue formation and enhance muscle regeneration after contusion injuries in a mouse model.

STUDY DESIGN

Controlled laboratory study.

METHODS

An animal model of muscle contusion was developed using the tibialis anterior muscle in 48 healthy mice at 8 to 10 weeks of age. After sustaining muscle contusion injuries, the mice were divided into 4 groups: (1) saline injection group (control group; n = 15), (2) MDSC transplantation group (MDSC group; n = 15), (3) MDSC transplantation plus oral losartan group (MDSC/losartan group; n = 15), and (4) healthy uninjured group (healthy group; n = 3). Losartan was administrated systemically beginning 3 days after injury and continued until the designated endpoint (1, 2, or 4 weeks after injury). MDSCs were transplanted 4 days after injury. Muscle regeneration and fibrotic scar formation were evaluated by histology, and the expression of follistatin, MyoD, Smad7, and Smad2/3 were analyzed by immunohistochemistry and reverse transcription polymerase chain reaction analysis. Functional recovery was measured via electrical stimulation of the peroneal nerve.

RESULTS

When compared with MDSC transplantation alone, MDSC/losartan treatment resulted in significantly decreased scar formation, an increase in the number of regenerating myofibers, and improved functional recovery after muscle contusions. In support of these findings, the expression levels of Smad7 and MyoD were significantly increased in the group treated with both MDSCs and losartan.

CONCLUSION

When compared with MDSCs alone, the simultaneous treatment of muscle contusions with MDSCs and losartan significantly reduced scar formation, increased the number of regenerating myofibers, and improved the functional recovery of muscle; these effects were caused, at least in part, by the losartan-mediated upregulation of Smad7 and MyoD. Increased levels of Smad7 and MyoD together reduced the deposition of scar tissue (via the inhibition of TGF-β1 by Smad7) and committed the transplanted MDSCs toward a myogenic lineage (via Smad7-regulated MyoD expression).

CLINICAL RELEVANCE

The study findings contribute to the development of biological treatments to accelerate and improve the quality of muscle healing after injury.

Clinical Practice Patterns and Beliefs in the Management of Hamstrings Strain Injuries

CONTEXT

Hamstrings strain injuries (HSIs) are among the most commonly occurring injuries in sport and are top causes of missed playing time. Lingering symptoms, prolonged recovery, and a high reinjury rate (12%-34%) make HSI management a frustrating and challenging process for the athletic trainer (AT). The clinical practice patterns and opinions of ATs regarding HSI treatment and rehabilitation are unknown.

OBJECTIVE

To examine the frequency of method use and opinions about current HSI management among ATs.

DESIGN

Cross-sectional study.

SETTING

Survey administered to registrants at the 2013 National Athletic Trainers' Association Clinical Symposia and AT Expo.

PATIENTS OR OTHER PARTICIPANTS

A total of 1356 certified ATs (691 men, 665 women; age = 35.4 ± 10.5 years, time certified = 11.92 ± 9.75 years).

DATA COLLECTION AND ANALYSIS

A survey was distributed electronically to 7272 registrants and on paper to another 700 attendees. Validity and reliability were established before distribution. Participants reported demographic information and rated their frequency of treatment and rehabilitation method use and agreement with questions assessing confidence, satisfaction, and desire for better clinical practice guidelines. Exploratory factor analysis and principal axis factor analysis were used. We also calculated descriptive statistics and χ(2) tests to assess practice patterns.

RESULTS

The response rate was 17% (n = 1356). A 2-factor solution was accepted for factor analysis (r = 0.76, r = 0.70), indicating that ATs follow either a contemporary or traditional management style. Various practice patterns were evident across employment settings and years of clinical experience. Satisfaction with the current HSI management plan was high (73.6%), whereas confidence in returning an athlete to play was lower (62.0%). Rates of use were associated with belief in effectiveness for all methods assessed (P < .001). Higher confidence levels were associated with high use of several methods; we observed increased satisfaction (χ(2)2 = 22.5, P = .002) but not increased confidence levels in more experienced ATs.

CONCLUSIONS

Our study demonstrated the lack of consensus in HSI treatment and rehabilitation and the ATs' desire for better clinical practice guidelines. Future research in which multimodal strategies, including both traditional and contemporary methods, are studied is warranted for effective management of HSI.

MUSCLE INJURY - PHYSIOPATHOLOGY, DIAGNOSIS, TREATMENT AND CLINICAL PRESENTATION

Skeletal muscle tissue has the largest mass in the human body, accounting for 45% of the total weight. Muscle injuries can be caused by bruising, stretching or laceration. The current classification divides such injuries into mild, moderate and severe. The signs and symptoms of grade I lesions are edema and discomfort; grade II, loss of function, gaps and possible ecchymosis; and grade III, complete rupture, severe pain and extensive hematoma. The diagnosis can be confirmed by: ultrasound, which is dynamic and cheap, but examiner dependent; and tomography or magnetic resonance, which gives better anatomical definition, but is static. Initial phase of the treatment can be summarized as the “PRICE” protocol. NSAIDs, ultrasound therapy, strengthening and stretching after the initial phase and range of motion without pain are used in clinical treatment. On the other hand, surgery has precise indications: hematoma drainage and muscle-tendon reinsertion and reinforcement.

Muscle Regeneration with Intermuscular Adipose Tissue (IMAT) Accumulation Is Modulated by Mechanical Constraints

Sports trauma are able to induce muscle injury with fibrosis and accumulation of intermuscular adipose tissue (IMAT), which affect muscle function. This study was designed to investigate whether hypoactivity would influence IMAT accumulation in regenerating mouse skeletal muscle using the glycerol model of muscle regeneration. The animals were immediately hindlimb unloaded for 21 days after glycerol injection into the tibialis anterior (TA) muscle. Muscle fiber and adipocyte cross-sectional area (CSA) and IMAT accumulation were determined by histomorphometric analysis. Adipogenesis during regenerative processes was examined using RT-qPCR and Western blot quantification. Twenty-one days of hindlimb unloading resulted in decreases of 38% and 50.6% in the muscle weight/body weight ratio and CSA, respectively, in soleus muscle. Glycerol injection into TA induced IMAT accumulation, reaching 3% of control normal-loading muscle area. This IMAT accumulation was largely inhibited in unloading conditions (0.09%) and concomitant with a marked reduction in perilipin and FABP4 protein content, two key markers of mature adipocytes. Induction of PPARγ and C/EBPα mRNA, two markers of adipogenesis, was also decreased. Furthermore, the protein expression of PDGFRα, a cell surface marker of fibro/adipogenic progenitors, was much lower in regenerating TA from the unloaded group. Exposure of regenerating muscle to hypoactivity severely reduces IMAT development and accumulation. These results provide new insight into the mechanisms regulating IMAT development in skeletal muscle and highlight the importance of taking into account the level of mechanical constraint imposed on skeletal muscle during the regeneration processes.

Interaction between HSP 70 and iNOS in skeletal muscle injury and repair

Muscle injuries are frequently occurred in various sports. The biological process and mechanism of muscle repair after injury are well known through the many studies. This study aimed at presenting heat shock protein and nitric oxide synthase are to respond to muscle damage and repair. This section discusses the results obtained through many articles. Heat shock proteins (HSPs) are considered to play an essential role in protecting cells from damage, preparing them to survive on new environmental challenges. In addition, exercise-induced changes such as heat shock, oxidative, metabolic, muscular, and cytokine stress seem to be responsible for the HSP response to exercise. Also, inducible nitric oxide synthase (iNOS) generates nitric oxide (NO) for prolonged period and causes pathophysiological effects. Furthermore, iNOS is involved in processes such as cell injury, wound repair, embryogenesis, tissue differentiation, and suppression of tumorigenesis. In conclusion, the inhibition of HSP 70 on caspase-3 and apoptosis is associated with its inhibition on iNOS that leads to less NO production.

Activity attenuates skeletal muscle fiber damage after ischemia and reperfusion

INTRODUCTION

In this investigation we aimed to determine whether: (1) physical activity protects rat skeletal muscle from ischemia/reperfusion (I/R) injury; and (2) continued activity after I/R improves the rate of healing.

METHODS

Rats were divided into sedentary or active (voluntary wheel running) groups. Active rats ran for 4 weeks before I/R or 4 weeks before plus 4 weeks after I/R.

RESULTS

Activity before I/R resulted in 73.2% less muscle damage (Evans blue dye inclusion). Sedentary and active rats had a similar decline in neural-evoked (∼ 99%) and directly stimulated (∼ 70%) in vivo muscle torque, and a similar reduction in junctophilin 1. Active rats produced 19% and 15% greater neural-evoked torque compared with sedentary rats at 14 and 28 days postinjury, respectively, although the rate of recovery appeared similar.

CONCLUSIONS

Activity protects against long-term muscle damage, but not short-term neural injury or excitation-contraction uncoupling. Continued activity neither accelerates nor hinders the rate of functional recovery.

Gene and cell therapy for muscle regeneration

Skeletal muscle injury and healing are multifactorial processes, involving three steps of healing: (1) degeneration and inflammation, (2) regeneration, and (3) fibrosis. Fibrous tissue hinders the muscle's complete recovery and current therapies fail in achieving total muscle recovery. Gene and cell therapy (or both) are potential future treatments for severe muscular injuries. Stem cells' properties associated with growth factors or/and cytokines can improve muscle healing and permit long-term recovery.

Therapeutic strategies for preventing skeletal muscle fibrosis after injury

Skeletal muscle repair after injury includes a complex and well-coordinated regenerative response. However, fibrosis often manifests, leading to aberrant regeneration and incomplete functional recovery. Research efforts have focused on the use of anti-fibrotic agents aimed at reducing the fibrotic response and improving functional recovery. While there are a number of mediators involved in the development of post-injury fibrosis, TGF-β1 is the primary pro-fibrogenic growth factor and several agents that inactivate TGF-β1 signaling cascade have emerged as promising anti-fibrotic therapies. A number of these agents are FDA approved for other conditions, clearing the way for rapid translation into clinical treatment. In this article, we provide an overview of muscle's host response to injury with special emphasis on the cellular and non-cellular mediators involved in the development of fibrosis. This article also reviews the findings of several pre-clinical studies that have utilized anti-fibrotic agents to improve muscle healing following most common forms of muscle injuries. Although some studies have shown positive results with anti-fibrotic treatment, others have indicated adverse outcomes. Some concerns and questions regarding the clinical potential of these anti-fibrotic agents have also been presented.

Biomaterials based strategies for skeletal muscle tissue engineering: existing technologies and future trends

Skeletal muscles have a robust capacity to regenerate, but under compromised conditions, such as severe trauma, the loss of muscle functionality is inevitable. Research carried out in the field of skeletal muscle tissue engineering has elucidated multiple intrinsic mechanisms of skeletal muscle repair, and has thus sought to identify various types of cells and bioactive factors which play an important role during regeneration. In order to maximize the potential therapeutic effects of cells and growth factors, several biomaterial based strategies have been developed and successfully implemented in animal muscle injury models. A suitable biomaterial can be utilized as a template to guide tissue reorganization, as a matrix that provides optimum micro-environmental conditions to cells, as a delivery vehicle to carry bioactive factors which can be released in a controlled manner, and as local niches to orchestrate in situ tissue regeneration. A myriad of biomaterials, varying in geometrical structure, physical form, chemical properties, and biofunctionality have been investigated for skeletal muscle tissue engineering applications. In the current review, we present a detailed summary of studies where the use of biomaterials favorably influenced muscle repair. Biomaterials in the form of porous three-dimensional scaffolds, hydrogels, fibrous meshes, and patterned substrates with defined topographies, have each displayed unique benefits, and are discussed herein. Additionally, several biomaterial based approaches aimed specifically at stimulating vascularization, innervation, and inducing contractility in regenerating muscle tissues are also discussed. Finally, we outline promising future trends in the field of muscle regeneration involving a deeper understanding of the endogenous healing cascades and utilization of this knowledge for the development of multifunctional, hybrid, biomaterials which support and enable muscle regeneration under compromised conditions.

Chronic Prosopis glandulosa treatment blunts neutrophil infiltration and enhances muscle repair after contusion injury

The current treatment options for soft tissue injuries remain suboptimal and often result in delayed/incomplete recovery of damaged muscle. The current study aimed to evaluate the effects of oral Prosopis glandulosa treatment on inflammation and regeneration in skeletal muscle after contusion injury, in comparison to a conventional treatment. The gastrocnemius muscle of rats was subjected to mass-drop injury and muscle samples collected after 1-, 3 h, 1- and 7 days post-injury. Rats were treated with P. glandulosa (100 mg/kg/day) either for 8 weeks prior to injury (up until day 7 post-injury), only post-injury, or with topically applied diclofenac post-injury (0.57 mg/kg). Neutrophil (His48-positive) and macrophage (F4/80-positive) infiltration was assessed by means of immunohistochemistry. Indicators of muscle satellite cell proliferation (ADAM₁₂) and regeneration (desmin) were used to evaluate muscle repair. Chronic P. glandulosa and diclofenac treatment (p < 0.0001) was associated with suppression of the neutrophil response to contusion injury, however only chronic P. glandulosa treatment facilitated more effective muscle recovery (increased ADAM₁₂ (p < 0.05) and desmin (p < 0.001) expression), while diclofenac treatment had inhibitory effects on repair, despite effective inhibition of neutrophil response. Data indicates that P. glandulosa treatment results in more effective muscle repair after contusion.

Acute effects of gastrocnemius muscle stretching after contusion in rats

The aim of this study was to evaluate the acute effects of stretching after gastrocnemius contusion in rats. Thirty-three male Wistar rats were selected (8 weeks, 219±35 g) and divided into 4 groups: Control (CG, n=3) - intact; Lesion (LG, n=10); Stretching (SG, n=10): Lesion and Stretching (LSG, n=10). The right gastrocnemius (RG) was submitted to contusion. Stretching on RG was performed manually, with 4 repetitions of 30 seconds each day, for 5 consecutive days, beginning 72 hour after contusion. One week later, rats were weighed and both paws were removed for investigation of muscle length, serial sarcomere number and sarcomere length. The final body weight increased in all groups. The muscle weight and length, as well as the serial sarcomere number (SSN) of LG, were higher than SG. However, the SSN of LSG was higher than SG. The sarcomere length of SG was the highest among all groups. It was concluded that the contusion and stretching did not affect body weight gain. The stretching induced sarcomerogenesis in injured muscle, but did not modify the healthy muscle.