Use of growth factors to improve muscle healing after strain injury

Tear Cytokines as Predictive Biomarkers of Success in Contact Lens Discomfort Management

PURPOSE

To analyze changes in tear levels of inflammatory mediators in symptomatic contact lens (CL) wearers after refitting with daily disposable CLs and to identify potential biomarkers of success in CL discomfort (CLD) management.

METHODS

Symptomatic CL wearers (CLDEQ-8 ≥ 12) were refitted (V1) with daily disposable CLs (Delefilcon A). After one month (V2), participants were classified into the post-fitting non-symptomatic (CLDEQ <12) and symptomatic (CLDEQ ≥12) groups. At each visit, the participants were clinically evaluated, tears were collected, and 20 inflammatory mediators and substance P (SP) were measured using multiplex immunobead analysis and ELISA, respectively. The detection rates and concentrations were compared between visits and groups, and logistic regression models were performed.

RESULTS

Forty-three subjects (32 women/11 men; mean age: 23.2 ± 4.9 years) were enrolled. The IL-1β and IL-9 detection rates were higher at V2 (p ≤ 0.044). The detection rates of IL-1β, IL-9, MIP-1α/CCL3, and MMP-9 at V1 (p ≤ 0.045) and IL-17A at V2 (p ≤ 0.014) were higher in the post-fitting symptomatic group. The tear IL-9 concentration was increased at V2 (p = 0.018). The tear concentrations of fractalkine/CX3CL1, IL-2, IL-6, IL-10, MCP-3/CCL7, MIP-1β, NGF, RANTES/CCL5, and TNF-α were higher in the post-fitting symptomatic group (p ≤ 0.044). Additionally, levels of fractalkine/CX3CL1, IL-2, IL-6, IL-10, RANTES/CCL5, and TNF-α at V1 were significantly associated with the post-fitting grouping (p ≤ 0.044).

CONCLUSIONS

Low tear concentrations of specific inflammatory mediators may be used as a predictive biomarker of success for refitting symptomatic CL wearers with daily disposable CLs. However, complementary treatments might be required for symptomatic CL wearers with higher levels of these inflammatory molecules.

Novel Bioresorbable Drug-Eluting Mesh Scaffold for Therapy of Muscle Injury

A novel bioresorbable drug-eluting polycaprolactone (PCL) mesh scaffold was developed, utilizing a solvent-cast additive manufacturing technique, to promote therapy of muscle injury. The degradation rate and mechanical properties strength of the PCL mesh were characterized after immersion in a buffer solution for different times. The in vitro release characteristics of vancomycin, ceftazidime, and lidocaine from the prepared mesh were evaluated using a high-performance liquid chromatography (HPLC) assay. In addition, the in vivo efficacy of PCL meshes for the repair of muscle injury was investigated on a rat model with histological examinations. It was found that the additively manufactured PCL meshes degraded by 13% after submission in buffered solution for four months. All PCL meshes with different pore sizes exhibited greater strength than rat muscle and survived through 10,000 cyclic loadings. Furthermore, the meshes could offer a sustained release of antibiotics and analgesics for more than 3 days in vitro. The results of this study suggest that drug-loaded PCL mesh exhibits superior ability to pure PCL mesh in terms of effectively promoting muscle repair in rat models. The histological assay also showed adequate biocompatibility of the resorbable meshes. The additively manufactured biodegradable drug-eluting meshes may be adopted in the future in humans for the therapy of muscle injuries.

The Role of Supporting Cell Populations in Satellite Cell Mediated Muscle Repair

Skeletal muscle has a high capacity to repair and remodel in response to damage, largely through the action of resident muscle stem cells, termed satellite cells. Satellite cells are required for the proper repair of skeletal muscle through a process known as myogenesis. Recent investigations have observed relationships between satellite cells and other cell types and structures within the muscle microenvironment. These findings suggest that the crosstalk between inflammatory cells, fibrogenic cells, bone-marrow-derived cells, satellite cells, and the vasculature is essential for the restoration of muscle homeostasis. This review will discuss the influence of the cells and structures within the muscle microenvironment on satellite cell function and muscle repair.

Feasibility of Growth Factor Agent Therapy in Repairing Motor Injury

Growth factors (GF), with the activity of stimulating cell growth, play a significant role in biology, medicine, and exercise physiology. In the process of exercise, human tissues are impacted, making cells suffer damage. Growth factor can accelerate the repair of damaged cells and regulate the synthesis of protein, so biological preparations of growth factors can be added to traditional therapies. A combination of growth factor biologics and conventional therapies may improve the efficiency of injury repair, but growth factor biologics may not produce any results. The feasibility of growth factor biologics in the treatment of motor injury was discussed. The research have shown that: 1) GF biological agent therapy is a very promising treatment for motor injury, which is based on the power of autologous growth factor (GFs) to accelerate tissue healing, promote muscle regeneration, increase angiogenesis, reduce fibrosis, and make the muscle injury rapid recovery. 2) There are various methods for delivering the higher dose of GF to the injured tissue, but most of them depend on the platelet release of GF. At the site of injury, there are several ways to deliver higher doses of GF to the injured tissue. 3) At present, the inhibition of GF is mainly through signal transduction inhibitors and inhibition of transcription factor production. 4) Pattern of GF during wound repair: GF directly regulates many key steps of normal wound repair, including inflammatory cell chemotaxis, division and proliferation of fibroblasts, keratinocytes and vascular endothelial cells, formation of new blood vessels, and synthesis and degradation of intercellular substances. 5) When GF promotes chronic wound healing, in most cases, certain GF can be used targeted only when in vivo regulation still cannot meet the need for repair.

Effectiveness of Hematoma Aspiration and Platelet-rich Plasma Muscle Injections for the Treatment of Hamstring Strains in Athletes

INTRODUCTION

The effect of platelet-rich plasma (PRP) treatment on recovery in acute hamstring injuries is controversial. Previous study results are inconsistent, and a standardized therapeutic approach has not been established yet.

PURPOSE

To assess the treatment effect using a combination of hematoma aspiration and muscle strain PRP injection in partial hamstring muscle tears (grade 2 strains) in athletes.

METHODS

Magnetic resonance imaging of athletes with grade 2 hamstring strains were reviewed from 2013 to 2018. From 2013 to 2015, athletes were treated conservatively, and from 2016 to 2018, with a combination of ultrasound-guided hematoma aspiration and PRP muscle strain injection. The outcome, including return-to-play (in days) and recurrence rate, was compared retrospectively between both groups (conservative vs aspiration/PRP) using ANOVA and Fisher's exact test. There was no significant difference in age, type of sport, and muscle involvement (including injury grade/location, hamstring muscle type, and length/cross-sectional area of the strain).

RESULTS

Fifty-five athletes (28 treated conservatively, 27 with hematoma aspiration/PRP injection) were included. Average return-to-play time (mean) was 32.4 d in the conservative group and 23.5 d in the aspiration/PRP group (P < 0.001). Recurrence rate of the hamstring strain was 28.6% (8/28) in the conservative treatment group and less than 4% (1/27) in the aspiration/PRP group (P = 0.025).

CONCLUSIONS

Athletes with grade 2 hamstring strains treated with a combination of hematoma aspiration and PRP injection had a significantly shorter return-to-play and a lower recurrence rate compared with athletes receiving conservative treatment.

Use of Platelet-Rich Plasma Plus Suramin, an Antifibrotic Agent, to Improve Muscle Healing After Injuries

BACKGROUND

The increasing use of platelet-rich plasma (PRP) to treat muscle injuries raises concerns because transforming growth factor-beta (TGF-β) in PRP may promote fibrosis in the injured muscle and thus impair muscle regeneration.

PURPOSE

To investigate whether suramin (a TGF-β inhibitor) can reduce muscle fibrosis to improve healing of the injured muscle after PRP treatment and identify the underlying molecular mechanism.

STUDY DESIGN

Controlled laboratory study.

METHODS

Myoblasts isolated from the gastrocnemius muscle of Sprague Dawley rats were treated with PRP or PRP plus suramin. MTT assays were performed to evaluate cell viability. The expression of fibrosis-associated proteins (such as type I collagen and fibronectin), Smad2, and phosphorylated Smad2 was determined using Western blot analysis and immunofluorescent staining. An anti-TGF-β antibody was employed to verify the role of TGF-β in fibronectin expression. Gastrocnemius muscles were injured through a partial transverse incision and then treated using PRP or PRP plus suramin. Hematoxylin and eosin staining was conducted to evaluate the healing process 7 days after the injury. Immunofluorescent staining was performed to evaluate fibronectin expression. Muscle contractile properties-fast-twitch and tetanic strength-were evaluated through electric stimulation.

RESULTS

PRP plus 25 μg/mL of suramin promoted myoblast proliferation. PRP induced fibronectin expression in myoblasts, but suramin reduced this upregulation. The anti-TGF-β antibody also reduced the upregulation of fibronectin expression in the presence of PRP. The upregulation of phosphorylated Smad2 by PRP was reduced by either the anti-TGF-β antibody or suramin. In the animal study, no significant difference was discovered in muscle healing between the PRP versus PRP plus suramin groups. However, the PRP plus suramin group had reduced fibronectin expression at the injury site. Fast-twitch strength and tetanic strength were significantly higher in the injured muscle treated using PRP or PRP plus suramin.

CONCLUSION

Simultaneous PRP and suramin use reduced fibrosis in the injured muscle and promoted healing without negatively affecting the muscle's contractile properties. The underlying molecular mechanism may be associated with the phosphorylated Smad2 pathway.

CLINICAL RELEVANCE

Simultaneous PRP and suramin use may reduce muscle fibrosis without compromising muscle contractile properties and thus improve muscle healing.

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.

Systemic Review: Is an Intradiscal Injection of Platelet-Rich Plasma for Lumbar Disc Degeneration Effective?

Current studies evaluating the outcomes of intradiscal platelet-rich plasma (PRP) injections in degenerative disc disease (DDD) are limited. The purpose of this review was to determine if an intradiscal injection of PRP for degenerative discs results in a statistically significant improvement in clinical outcomes. A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Level I-IV investigations of intradiscal PRP injections in DDD were sought in multiple databases. The Modified Coleman Methodology Score (MCMS) was used to analyze the methodological quality of the study. Only the outcome measurements used by more than 50% of the studies were included in the data analysis. The study heterogeneity and nature of evidence (mostly retrospective, non-comparative) precluded meta-analysis. Pre and post-injection pain visual analog scales (VAS) were compared using two sample Z-tests. Five articles (90 subjects, mean age 43.6 ± 7.7 years, mean follow-up 8.0 ± 3.6 months) were analyzed. Four articles were level IV evidence and one article was level II. Mean MCMS was 56.0 ± 10.3. There were 43 males and 37 females (10 unidentified). Pain VAS significantly improved following lumbar intradiscal PRP injection (69.7 mm to 43.3 mm; p<0.01). Two patients (2.2%) experienced lower extremity paresthesia after treatment. One patient (1.1%) underwent re-injection. No other complications were reported. In conclusion, intradiscal injection of PRP for degenerative discs resulted in statistically significant improvement in VAS with low re-injection and complication rates in this systematic review. It is unclear whether the improvements were clinically significant given the available evidence. The low level of evidence available (level IV) does not allow for valid conclusions regarding efficacy; however, the positive results suggest that further higher-quality studies might be of value.

Tear Inflammatory Molecules in Contact Lens Wearers: A Literature Review

Background:

Numerous studies have analysed the effect of using different Contact Lenses (CLs) or care solutions, and suffering discomfort or diseases associated with CL wear on the inflammatory mediator release into the tears.

Objective:

To summarize the published data on tear inflammatory molecules related to CL use.

Methods:

A PubMed-NCBI search has been conducted and those publications which carried out original investigations including the analysis of tear inflammatory mediators in CL wearers were selected.

Results:

Forty-three articles, from 1990 to 2019, have been included. Wearing hydrogel CLs, rigid gas permeable CLs, and special designs for irregular corneas in keratoconus patients (CLs with keratoconic design, hybrid CLs, piggyback fit, and scleral CLs) have been reported to alter the concentration of several molecules in tears. Moreover, there seems to be an effect of the wearing time and schedule, CL materials and designs, and care solutions used. Regarding CL discomfort, its relation with inflammatory mediators is not clear. However, some diseases associated to CL wear, such as giant papillary conjunctivitis, CL induced acute red eye, CL induced peripheral ulcer, and acanthamoeba keratitis have been related to the release of certain inflammatory mediators, which may serve as potential biomarkers.

Conclusion:

There is evidence suggesting that different aspects of CL wear alter the inflammatory mediator profile in tears, which may indicate an inflammatory state of the lacrimal functional unit. However, more studies need to be carried out to better understand how this inflammatory process works and its repercussion on the different aspects of CL wear.

Scientific Basis for Eccentric Quasi-Isometric Resistance Training: A Narrative Review

Oranchuk, DJ, Storey, AG, Nelson, AR, and Cronin, JB. The scientific basis for eccentric quasi-isometric resistance training: A narrative review. J Strength Cond Res 33(10): 2846-2859, 2019-Eccentric quasi-isometric (EQI) resistance training involves holding a submaximal, yielding isometric contraction until fatigue causes muscle lengthening and then maximally resisting through a range of motion. Practitioners contend that EQI contractions are a powerful tool for the development of several physical qualities important to health and sports performance. In addition, several sports involve regular quasi-isometric contractions for optimal performance. Therefore, the primary objective of this review was to synthesize and critically analyze relevant biological, physiological, and biomechanical research and develop a rationale for the value of EQI training. In addition, this review offers potential practical applications and highlights future areas of research. Although there is a paucity of research investigating EQIs, the literature on responses to traditional contraction types is vast. Based on the relevant literature, EQIs may provide a practical means of increasing total volume, metabolite build-up, and hormonal signaling factors while safely enduring large quantities of mechanical tension with low levels of peak torque. Conversely, EQI contractions likely hold little neuromuscular specificity to high velocity or power movements. Therefore, EQI training seems to be effective for improving musculotendinous morphological and performance variables with low injury risk. Although speculative due to the limited specific literature, available evidence suggests a case for future experimentation.

Development of Microfluidic Stretch System for Studying Recovery of Damaged Skeletal Muscle Cells

The skeletal muscle occupies about 40% mass of the human body and plays a significant role in the skeletal movement control. Skeletal muscle injury also occurs often and causes pain, discomfort, and functional impairment in daily living. Clinically, most studies observed the recovery phenomenon of muscle by massage or electrical stimulation, but there are limitations on quantitatively analyzing the effects on recovery. Although additional efforts have been made within in vitro biochemical research, some questions still remain for effects of the different cell microenvironment for recovery. To overcome these limitations, we have developed a microfluidic system to investigate appropriate conditions for repairing skeletal muscle injury. First, the muscle cells were cultured in the microfluidic chip and differentiated to muscle fibers. After differentiation, we treated hydrogen peroxide and 18% axial stretch to cause chemical and physical damage to the muscle fibers. Then the damaged muscle fibers were placed under the cyclic stretch condition to allow recovery. Finally, we analyzed the damage and recovery by quantifying morphological change as well as the intensity change of intracellular fluorescent signals and showed the skeletal muscle fibers recovered better in the cyclic stretched condition. In total, our in situ generation of muscle damage and induction recovery platform may be a key system for investigating muscle recovery and rehabilitation.

Platelet-Rich Plasma Releasate Promotes Regeneration and Decreases Inflammation and Apoptosis of Injured Skeletal Muscle

BACKGROUND

Platelet-rich plasma (PRP) contains various cytokines and growth factors that may be beneficial to the healing process of injured muscle. Based on the authors' previous study, PRP releasate can promote proliferation and migration of skeletal muscle cells in vitro, so animal studies are performed to support the use of PRP to treat muscle injury in vivo.

PURPOSE

To investigate the effect of PRP releasate on regeneration of injured muscle, as well as its effect on inflammatory reaction and cell apoptosis, in the early stages of the muscle-healing process.

STUDY DESIGN

Controlled laboratory study.

METHODS

The gastrocnemius muscles of Sprague-Dawley rats were injured by partial transverse incision and then treated with PRP releasate. Hematoxylin and eosin stain was used to evaluate the healing process of injured muscle at 2, 5, and 10 days after injury. TUNEL assay was used to evaluate the cell apoptosis of injured muscle after PRP releasate treatment. Immunohistochemistry was used to stain the CD68-positive cells during the healing process. Muscle contractile properties, including fast-twitch and tetanic strength, were evaluated by electric stimulation.

RESULTS

The results revealed that PRP releasate treatment could enhance the muscle-healing process and decrease CD68-positive cells and apoptotic cells. Furthermore, the tetanic strength was significantly higher in injured muscle treated with PRP releasate.

CONCLUSION

In conclusion, PRP releasate could enhance the healing process of injured muscle and decrease inflammatory cell infiltration as well as cell apoptosis.

CLINICAL RELEVANCE

PRP promotes skeletal muscle healing in association with decreasing inflammation and apoptosis of injured skeletal muscle. These findings provide in vivo evidence to support the use of PRP to treat muscle injury.

Inhibition of ADAM10 in satellite cells accelerates muscle regeneration following muscle injury

Muscle injury is one of the most common orthopedic and sports disorders. For severe cases, surgical repair may be indicated; however, other than immobilization and the administration of anti-inflammatory drugs there is currently no effective conservative treatment for this condition. Satellite cells (SCs) are muscle-specific stem cells and are indispensable for muscle regeneration after muscle injury. SCs are activated upon muscle injury to proliferate and differentiate into myoblasts, which subsequently fuse into myofibers and regenerate the damaged muscle. We have previously shown that ADAM10, a membrane-anchored proteolytic enzyme, is essential for the maintenance of SC quiescence by activating the Notch signaling pathway in SCs. Because suppression of ADAM10 activity in SCs can activate SC differentiation, we asked whether inactivation of ADAM10 in SCs after muscle injury could enhance muscle regeneration. Using Adam10 conditional knockout mice, in which ADAM10 activity can specifically be suppressed in SCs, we found that partial inactivation of ADAM10 accelerates muscle regeneration after muscle injury. Nearly identical results were obtained by the administration of GI254023X, a selective ADAM10 inhibitor. The findings of the present study thus indicate that transient enhancement of SC differentiation after muscle injury expedites muscle regeneration and that ADAM10 can be a potential molecular target in treating muscle injuries. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Does platelet-rich plasma decrease time to return to sports in acute muscle tear? A randomized controlled trial

PURPOSE

The aim of this study is to report the effects of autologous PRP injections on time to return to play and recurrence rate after acute grade 2 muscle injuries in recreational and competitive athletes.

METHODS

Seventy-five patients diagnosed with acute muscle injuries were randomly allocated to autologous PRP therapy combined with a rehabilitation programme or a rehabilitation programme only. The primary outcome of this study was time to return to play. In addition, changes in pain severity and recurrence rates were evaluated.

RESULTS

Patients in the PRP group achieved full recovery significantly earlier than controls (P = 0.001). The mean time to return to play was 21.1 ± 3.1 days and 25 ± 2.8 days for the PRP and control groups, respectively (P = 0.001). Significantly lower pain severity scores were observed in the PRP group throughout the study. The difference in the recurrence rate after 2-year-follow-up was not statistically significant between groups.

CONCLUSIONS

A single PRP injection combined with a rehabilitation programme significantly shortened time to return to sports compared to a rehabilitation programme only. Recurrence rate was not significantly different between groups.

LEVEL OF EVIDENCE

I.

Platelet rich plasma releasate promotes proliferation of skeletal muscle cells in association with upregulation of PCNA, cyclins and cyclin dependent kinases

Platelet rich plasma (PRP) contains various cytokines and growth factors which may be beneficial to the healing process of injured muscle. The purpose of this study is to investigate the effect and molecular mechanism of PRP releasate on proliferation of skeletal muscle cells. Skeletal muscle cells intrinsic to Sprague-Dawley rats were treated with PRP releasate. Cell proliferation was evaluated by 3-[4,5-Dimethylthiazol- 2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and immunocytochemistry with Ki-67 stain. Flow cytometric analysis was used to evaluate the cell cycle progression. Western blot analysis was used to evaluate the protein expressions of PCNA, cyclin E1, cyclin A2, cyclin B1, cyclin dependent kinase (cdk)1 and cdk2. The results revealed that PRP releasate enhanced proliferation of skeletal muscle cells by shifting cells from G1 phase to S phase and G2/M phases. Ki-67 stain revealed the increase of proliferative capability after PRP releasate treatment. Protein expressions including cyclin A2, cyclin B1, cdk1, cdk2 and PCNA were up-regulated by PRP releasate in a dose-dependent manner. It was concluded that PRP releasate promoted proliferation of skeletal muscle cells in association with the up-regulated protein expressions of PCNA, cyclin A2, cyclin B1, cdk1 and cdk2.

Circulating biomarkers in acute myofascial pain: A case-control study

The aims of the present study were to compare levels of circulating inflammatory biomarkers and growth factors between patients with myofascial pain syndrome (MPS) and healthy control participants, and to assess the relationship among inflammatory markers and growth factors in the two groups.Biomarkers levels were assessed in patients (n = 37) with myofascial pain complaints recruited from the hospital emergency department and non-MPS controls (n = 21), recruited via advertisements in the hospital and community.Blood levels of the cytokines, namely, interleukin-6 (IL-6), tumor necrosis factor (TNF), and interleukin-12 (IL-12), and the chemokine, namely, monocyte chemoattractant protein-1 (MCP-1), macrophage-derived chemokine (MDC), eotaxin, granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-8 (IL-8), and macrophage inflammatory proteins-1β (MIP-1β) were significantly higher in patients with MPS than controls. The results of the growth factor analyses revealed significantly higher levels of fibroblast growth factor-2 (FGF-2), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) in MPS patients versus controls. The pattern of correlation coefficients between cytokines and growth factors differed considerably for MPS patients and controls with far fewer significant positive coefficients observed in the controls. Serum inflammatory and growth factor biomarkers were elevated in MPS patients.Inflammatory biomarkers and growth factor levels may play an important role in the onset and maintenance of MPS and therefore may be useful in the diagnosis and treatment of MPS. Understanding the mechanisms of inflammation in MPS necessitates future research.

Muscle injuries and strategies for improving their repair

Satellite cells are tissue resident muscle stem cells required for postnatal skeletal muscle growth and repair through replacement of damaged myofibers. Muscle regeneration is coordinated through different mechanisms, which imply cell-cell and cell-matrix interactions as well as extracellular secreted factors. Cellular dynamics during muscle regeneration are highly complex. Immune, fibrotic, vascular and myogenic cells appear with distinct temporal and spatial kinetics after muscle injury. Three main phases have been identified in the process of muscle regeneration; a destruction phase with the initial inflammatory response, a regeneration phase with activation and proliferation of satellite cells and a remodeling phase with maturation of the regenerated myofibers. Whereas relatively minor muscle injuries, such as strains, heal spontaneously, severe muscle injuries form fibrotic tissue that impairs muscle function and lead to muscle contracture and chronic pain. Current therapeutic approaches have limited effectiveness and optimal strategies for such lesions are not known yet. Various strategies, including growth factors injections, transplantation of muscle stem cells in combination or not with biological scaffolds, anti-fibrotic therapies and mechanical stimulation, may become therapeutic alternatives to improve functional muscle recovery.

Intra-Articular Injections of Platelet-Rich Plasma versus Hyaluronic Acid in the Treatment of Osteoarthritic Knee Pain: A Randomized Clinical Trial in the Context of the Spanish National Health Care System

Intra-articular injection of platelet-rich plasma (PRP) has been established as a suitable treatment for knee osteoarthritis. Here, we present a double-blind randomized controlled clinical trial, conducted in a public Hospital of the Spanish National Health Care System, to evaluate the efficacy of injecting autologous PRP versus hyaluronic acid (HA) in knee osteoarthritis. PRP was manufactured in Malaga’s Regional Blood Center (Spain). Patients that met the eligibility criteria were randomized into a PRP group or a HA group. Pain and functional improvements were assessed pre- and post-treatment (three and six months follow-up) using the Visual Analogue Scale (VAS); the Knee and Osteoarthritis Outcome System (KOOS) scale and the European Quality of Life scale (EUROQOL). Both groups presented pain reduction at six months. The VAS scores for the PRP group improved by at least 50% from their initial value, particularly at three months following the final infiltration, with results resembling those of the HA group at six months. PRP was more effective in patients with lower osteoarthritis grades. Both treatments improved pain in knee osteoarthritis patients without statistically significant differences between them. However, PRP injection was proved to improve pain three months after the final infiltration and to be more effective in lower osteoarthritis grades.

Platelet-rich plasma in the treatment of acute hamstring injuries in professional football players

PURPOSE

muscle injuries have a high incidence in professional football and are responsible for the largest number of days lost from competition. Several in vitro studies have confirmed the positive role of platelet-rich plasma (PRP) in accelerating recovery and in promoting muscle regeneration, and not fibrosis, in the healing process. This study examines the results of intralesional administration of PRP in the treatment of primary hamstring injuries sustained by players belonging to a major league football club.

METHODS

twenty-five hamstring injuries (grade 2 according to MRI classification) sustained by professional football players during a 31-months observation period were treated with PRP and analyzed. Sport participation absence (SPA), in days, was considered to correspond to the healing time, and we also considered the re-injury rate, and tissue healing on MRI. The mean follow-up was 36.6 months (range 22-42).

RESULTS

there were no adverse events. The mean SPA for the treated muscle injuries was 36.76±19.02 days. The re-injury rate was 12%. Tissue healing, evaluated on MRI, was characterized by the presence of excellent repair tissue and a small scar.

CONCLUSIONS

this study confirmed the safety of PRP in treating hamstring lesions in a large series of professional football players. PRP-treated lesions did not heal more quickly than untreated lesions described in the literature, but they showed a smaller scar and excellent repair tissue.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Role of Growth Factors in Modulation of the Microvasculature in Adult Skeletal Muscle

Post-natal skeletal muscle is a highly plastic tissue that has the capacity to regenerate rapidly following injury, and to undergo significant modification in tissue mass (i.e. atrophy/hypertrophy) in response to global metabolic changes. These processes are reliant largely on soluble factors that directly modulate muscle regeneration and mass. However, skeletal muscle function also depends on an adequate blood supply. Thus muscle regeneration and changes in muscle mass, particularly hypertrophy, also demand rapid changes in the microvasculature. Recent evidence clearly demonstrates a critical role for soluble growth factors in the tight regulation of angiogenic expansion of the muscle microvasculature. Furthermore, exogenous modulation of these factors has the capacity to impact directly on angiogenesis and thus, indirectly, on muscle regeneration, growth and performance. This chapter reviews recent developments in understanding the role of growth factors in modulating the skeletal muscle microvasculature, and the potential therapeutic applications of exogenous angiogenic and anti-angiogenic mediators in promoting effective growth and regeneration, and ameliorating certain diseases, of skeletal muscle.

Platelet-rich plasma, especially when combined with a TGF-β inhibitor promotes proliferation, viability and myogenic differentiation of myoblasts in vitro

Regeneration of skeletal muscle after injury is limited by scar formation, slow healing time and a high recurrence rate. A therapy based on platelet-rich plasma (PRP) has become a promising lead for tendon and ligament injuries in recent years, however concerns have been raised that PRP-derived TGF-β could contribute to fibrotic remodelling in skeletal muscle after injury. Due to the lack of scientific grounds for a PRP -based muscle regeneration therapy, we have designed a study using human myogenic progenitors and evaluated the potential of PRP alone and in combination with decorin (a TGF-β inhibitor), to alter myoblast proliferation, metabolic activity, cytokine profile and expression of myogenic regulatory factors (MRFs). Advanced imaging multicolor single-cell analysis enabled us to create a valuable picture on the ratio of quiescent, activated and terminally committed myoblasts in treated versus control cell populations. Finally high-resolution confocal microscopy validated the potential of PRP and decorin to stimulate the formation of polynucleated myotubules. PRP was shown to down-regulate fibrotic cytokines, increase cell viability and proliferation, enhance the expression of MRFs, and contribute to a significant myogenic shift during differentiation. When combined with decorin further synergistc effects were identified. These results suggest that PRP could not only prevent fibrosis but could also stimulate muscle commitment, especially when combined with a TGF-β inhibitor.

Gene Expression Profiling of Grass Carp (Ctenopharyngodon idellus) and Crisp Grass Carp

Grass carp (Ctenopharyngodon idellus) is one of the most important freshwater fish that is native to China, and crisp grass carp is a kind of high value-added fishes which have higher muscle firmness. To investigate biological functions and possible signal transduction pathways that address muscle firmness increase of crisp grass carp, microarray analysis of 14,900 transcripts was performed. Compared with grass carp, 127 genes were upregulated and 114 genes were downregulated in crisp grass carp. Gene ontology (GO) analysis revealed 30 GOs of differentially expressed genes in crisp grass carp. And strong correlation with muscle firmness increase of crisp grass carp was found for these genes from differentiation of muscle fibers and deposition of ECM, and also glycolysis/gluconeogenesis pathway and calcium metabolism may contribute to muscle firmness increase. In addition, a number of genes with unknown functions may be related to muscle firmness, and these genes are still further explored. Overall, these results had been demonstrated to play important roles in clarifying the molecular mechanism of muscle firmness increase in crisp grass carp.

Comparison between two different platelet-rich plasma preparations and control applied during anterior cruciate ligament reconstruction. Is there any evidence to support their use?

INTRODUCTION

To compare the clinical, analytical and graft maturation effects of two different platelet-rich plasma (PRP) preparations applied during anterior cruciate ligament (ACL) reconstruction.

MATERIALS AND METHODS

A total of 150 patients with ACL disruption were included in the study. Arthroscopic ACL reconstruction with patellar tendon allograft was conducted on all knees using the same protocol. One hundred patients were prospectively randomised to either a group to receive double-spinning platelet-enriched gel (PRP) with leukocytes (n=50) or to a non-gel group (n=50). Finally, we included 50 patients treated with a platelet-rich preparation from a single-spinning procedure (PRGF Endoret(®) Technology) without leukocytes. Inflammatory parameters, including C-reactive protein (CRP) and knee perimeters (PER), were measured 24 hours and 10 days after surgery. Postoperative pain score (visual analogue score [VAS]) was recorded the day after surgery. Follow-up visits occurred postoperatively at 3, 6, and 12 months. The International Knee Documentation Committee scale (IKDC) was included to compare functional state, and MRI was conducted 6 months after surgery.

RESULTS

The PRGF group showed a statistically significant improvement in swelling and inflammatory parameters compared with the other two groups at 24 hours after surgery (p<0.05). The results did not show any significant differences between groups for MRI and clinical scores.

CONCLUSIONS

PRGF used in ACL allograft reconstruction was associated with reduced swelling; however, the intensity and uniformity of the graft on MRI were similar in the three groups, and there was no clinical or pain improvement compared with the control group.

LEVEL OF EVIDENCE

II.

Enhancement of muscle repair using human mesenchymal stem cells with a magnetic targeting system in a subchronic muscle injury model

BACKGROUND

A magnetic cell targeting system was previously developed to promote the accumulation of transplanted cells in sites of injury in order to effectively treat injured tissues. However, the optimum time of exposure to the magnetic field and the strength of the magnetic force have not yet been clarified. In this study, we investigated the optimum conditions of the magnetic force required to retain iron-labeled human mesenchymal stem cells (hMSCs) at the site of transplantation for muscle repair in a subchronic skeletal muscle injury nude rat model.

METHODS

First, the optimum strength and time of exposure to the magnetic force for cell retention at the transplantation site were investigated 2 days after cell transplantation (1 × 10(5) cells). Second, the degree of enhancement of muscle repair was investigated at 3 weeks after cell transplantation in the group treated without a magnetic force and two typical magnetic condition groups that exhibited different levels of cell integration in first part of the study.

RESULTS

On the basis of the results of the first investigation, it was concluded that a magnetic strength of 1.5 T and 10 min of exposure to the magnetic force were efficient conditions to induce the retention of transplanted cells at the site of transplantation. In the second study, the groups exposed to a 1.5-T magnetic field for 10 min demonstrated significant enhancement of muscle repair, both histologically and electromechanically.

CONCLUSIONS

This study identified the optimal conditions required to retain transplanted hMSCs at the site of transplantation using a magnetic targeting system. This study also showed that the restoration of subchronic muscle injuries can be enhanced by magnetically labeled hMSCs following the application of a magnetic force.

Midkine-deficient mice delayed degeneration and regeneration after skeletal muscle injury

Midkine (MK), a heparin-binding growth factor, was previously found to be expressed in the rat myotube-forming stage. We investigated MK gene-deficient (Mdk(-/-)) mice in terms of skeletal muscle degeneration and regeneration after injury by bupivacaine injection into the tibialis anterior muscle. Injured muscles showed intense inflammatory cell infiltration. Myotubes, myofibers with centrally located nuclei in their cytoplasm, were significantly smaller in Mdk(-/-) mice than in wild type (Mdk(+/+)) mice 7 days after injury (p=0.02). The distribution of myotube sizes showed quantitative differences between the two groups at 5 and 7 days, but not at 14 days. Many small myotubes were found in the regenerative area of Mdk(-/-) mice compared with that of Mdk(+/+)mice 5 and 7 days after injury. The expression of Iba1, a macrophage marker, was significantly lower in Mdk(-/-) mice 3 days after injury (p=0.01). The number of desmin-positive cells like myoblasts in Mdk(-/-) mice was significantly fewer than that in Mdk(+/+) mice 3 days after injury. Our results suggested that deletion of MK results in a delay in regeneration, preceded by decelerated migration of macrophages to the damaged area, and that MK has a role in cell differentiation and maturation after skeletal muscle injury.

Detecting the developmental toxicity of bFGF in the embryonic stem cell test using differential gene expression of differentiation-related genes

Basic fibroblast growth factor (bFGF) is a mitogenic cytokine that can stimulate mesoderm-and neuroectoderm-originated cell proliferation. This study was performed to investigate the effects of bFGF on cell differentiation and the expression of specific markers at different embryonic developmental stages. We firstly evaluated the embryotoxic potential of bFGF in vitro using a modified EST protocol. Sequentially, we further investigated how bFGF impact the different tissue-special genes and proteins expressions during the differentiation of murine ES cells in vitro and attempt to reveal the effects of bFGF on differentiation processes. This analysis was focused on key tissue- and stage-specific genes involved in ectodermal, mesodermal, and endodermal differentiation, including ectodermal-specific gene Nestin, Oligo2 and Syn, mesodermal-specific gene MHC and MyoD, and endodermal-specific gene GATA6, TTR and ALB, as well as undifferentiated gene Sox-2 and Oct-4. The results demonstrate that bFGF could promote expression of ectodermal-specific genes and protein, but suppress the expressions of endoderm-specific and some mesoderm-specific gene and protein. A conclusion can be drawn that bFGF exhibits weak embryotoxicity and mainly promotes ES cell differentiation towards the ectodermal lineages but suppress differentiation into endoderm lineages. These opposing effects of bFGF on the embryonic development of the three germ layers may be related to its weak embryotoxic potential. More specifically, inhibition of expression of the endodermal-specific markers transthyretin (TTR), and albumin (ALB) by bFGF may be of more value in detecting the embryotoxic potential of bFGF.

Intramuscular administration of PEGylated IGF-I improves skeletal muscle regeneration after myotoxic injury

OBJECTIVE

Musculoskeletal injuries represent a major public health problem and drugs that can improve muscle repair and restore function are needed for patients with these conditions and other related muscular pathologies. Increasing insulin-like growth factor-I (IGF-I) levels in skeletal muscle improves regeneration after myotoxic injury and while administration of IGF-I has a potential for accelerating healing after trauma, optimizing its method of delivery and obviating potential side-effects currently associated with recombinant human (rh) IGF-I, remain a hurdle.

DESIGN

We compared the treatment efficacy of rhIGF-I with a polyethylene glycol modified IGF-I (PEG-IGF-I) analog to improve functional repair of mouse tibialis anterior muscles after myotoxic injury, testing the hypothesis that PEG-IGF-I would exert greater beneficial effects on regenerating skeletal muscles than rhIGF-I due to improved pharmacokinetic properties. We also examined the relative efficacy of systemic versus local delivery of these IGF-I variants for improving functional muscle regeneration.

RESULTS

Local delivery of PEG-IGF-I, but not rhIGF-I, at 4 days post-injury significantly improved early functional recovery as evident by a 27% increase in normalized force compared with saline control (P<0.05), whereas systemic application of either IGF-I variant was not effective. The improved function with intramuscular PEG-IGF-I administration was attributed to a greater and prolonged residence within the regenerating muscles, resulting in increased Akt activation and a 13% larger fiber cross-sectional area compared with rhIGF-I (P<0.05).

CONCLUSIONS

These data support the hypothesis that PEG-IGF-I is more efficacious than rhIGF-I in hastening early fiber regeneration and improving muscle function after injury, highlighting its therapeutic potential for muscular pathologies.

Platelet-Rich Plasma in Addition to Rehabilitation for Acute Hamstring Injuries in NFL Players: Clinical Effects and Time to Return to Play

BACKGROUND

Platelet-rich plasma (PRP) injections have been proposed to hasten soft tissue healing. There is a lack of evidence in the current literature to support their efficacy in elite athletes.

PURPOSE

To investigate the effects of the addition of PRP to rehabilitation in the treatment of acute hamstring injuries in professional National Football League (NFL) players and to report the time to return to play.

STUDY DESIGN

Case control study.

METHODS

Ten NFL players with similar hamstring injury patterns were retrospectively divided into 2 groups. The treatment group (PRP; n = 5) was injected with PRP and the control group (non-PRP; n = 5) was not injected; both groups completed a rehabilitation program. The PRP injections were administered under ultrasound guidance with precise localization of the injury site, within 24 to 48 hours of injury. Age, muscle involved, extent of injury, grading, and time to return to play were noted. Descriptive statistics and the exact Wilcoxon rank-sum test were used for data analysis.

RESULTS

The mean age was 23 years (range, 22-27 years) for the PRP group and 26 years (range, 22-28 years) for the non-PRP group (P = .42). The median longitudinal extent of the injury was 14 cm (range, 9-18 cm) in the PRP group and 15 cm (range, 9-16 cm) in the non-PRP group (P = .77). The average transverse extent of the injury in the PRP and non-PRP groups was 4 cm (range, 1.6-6 cm) and 3.5 cm (range, 2-5 cm), respectively, and the respective average anteroposterior extent was 4 cm (range, 1.9-5 cm) and 2.9 cm (range, 1.5-4 cm). The long head of biceps femoris was most commonly involved (4 in each group), with a single tear of the semimembranosus in each group. The median injury classification was grade 2 in both groups. The median time to return to play was 20 days (range,16-30 days) in the PRP group and 17 days (range, 8-81 days) in the non-PRP group (P = .73).

CONCLUSION

There were no significant differences in recovery from hamstring injury between treatment with PRP and routine rehabilitation. A larger, randomized controlled trial is warranted.

Experimental model for the study of the effects of platelet-rich plasma on the early phases of muscle healing

BACKGROUND

There is abundant evidence suggesting that growth factors may play a key role in the healing process, especially in the early stages of inflammation. Despite the reported clinical successes with the use of growth factors there is still a lack of knowledge on the biological mechanism underlying the activity of platelet-rich plasma during the process of muscle healing. The aim of this study was to analyse the early effects of platelet- rich plasma in an easily reproducible animal model.

MATERIALS AND METHODS

Wistar male adult rats (n=102) were used in this study. The muscle lesion was created with a scalpel in the flexor sublimis muscles. Platelet-rich plasma was applied immediately after surgery. Treated, untreated and contralateral muscles were analysed by morphological evaluation and western blot assay.

RESULTS

Leucocyte infiltration was significantly greater in muscles treated with platelet-rich plasma than in both untreated and contralateral muscles. The latter showed greater leucocyte infiltration when compared to the untreated muscles. Platelet-rich plasma treatment also modified the cellular composition of the leucocyte infiltration leading to increased expression of CD3, CD8, CD19 and CD68 and to decreased CD4 antigen expression in both platelet-rich plasma treated and contralateral muscles. Blood vessel density and blood vessel diameters were not statistically significantly different between the three groups analysed.

DISCUSSION

The results of this study showed that treatment with platelet-rich plasma magnified the physiological early inflammatory response following a muscle injury, modifying the pattern of cellular recruitment. Local platelet-rich plasma treatment may exert a direct or, more plausibly, indirect systemic effect on healing processes, at least in the earliest inflammatory phase.

[Current treatment concepts for muscular injuries]

Muscular lesions represent the most common form of sports injury. The four large muscle groups hamstrings, adductors, gastrocnemius and knee extensor muscles are most often affected. Most injuries occur during excentric tension impact. Diagnostics begin with an exact medical history and detailed clinical investigations. Imaging with ultrasound and magnetic resonance imaging (MRI) are important to differentiate between structural lesions and functional disorders and to determine the extent of the injury. Most frequently treatment remains conservative and is oriented to the three phases of the healing process. In most cases (leisure sports) the rest, ice, compression and elevation (RICE) concept with subsequent pain-adapted load increase suffices for a return to sport activities. Infiltration therapy including platelet-rich plasma (PRP) is an additional therapy option but should not be used to accelerate the healing process. Surgical treatment only rarely becomes necessary for treatment of muscular injuries.

Promotion of muscle regeneration by myoblast transplantation combined with the controlled and sustained release of bFGFcpr

Although myoblast transplantation is an attractive method for muscle regeneration, its efficiency remains limited. The efficacy of myoblast transplantation in combination with the controlled and sustained delivery of basic fibroblast growth factor (bFGF) was investigated. Defects of thigh muscle in Sprague-Dawley (SD) rats were created, and GFP-positive myoblasts were subsequently transplanted. The rats were divided into three groups. In control group 1 (C1) only myoblasts were transplanted, while in control group 2 (C2) myoblasts were introduced along with empty gelatin hydrogel microspheres. In the experimental group (Ex), myoblasts were transplanted along with bFGF incorporated into gelatin hydrogel microspheres. Four weeks after transplantation, GFP-positive myoblasts were found to be integrated into the recipient muscle and to contribute to muscle fibre regeneration in all groups. A significantly higher expression level of GFP in the Ex group demonstrated that the survival rate of transplanted myoblasts in Ex was remarkably improved compared with that in C1 and C2. Furthermore, myofibre regeneration, characterized by centralization of the nuclei, was markedly accelerated in Ex. The expression level of CD31 in Ex was higher than that in both C1 and C2, but the differences were not statistically significant. A significantly higher expression level of Myogenin and a lower expression level of MyoD1 were both observed in Ex after 4 weeks, suggesting the promotion of differentiation to myotubes. Our findings suggest that the controlled and sustained release of bFGF from gelatin hydrogel microspheres improves the survival rate of transplanted myoblasts and promotes muscle regeneration by facilitating myogenesis rather than angiogenesis.

Chronic nerve growth factor exposure increases apoptosis in a model of in vitro induced conjunctival myofibroblasts

In the conjunctiva, repeated or prolonged exposure to injury leads to tissue remodeling and fibrosis associated with dryness, lost of corneal transparency and defect of ocular function. At the site of injury, fibroblasts (FB) migrate and differentiate into myofibroblasts (myoFB), contributing to the healing process together with other cell types, cytokines and growth factors. While the physiological deletion of MyoFB is necessary to successfully end the healing process, myoFB prolonged survival characterizes the pathological process of fibrosis. The reason for myoFB persistence is poorly understood. Nerve Growth Factor (NGF), often increased in inflamed stromal conjunctiva, may represent an important molecule both in many inflammatory processes characterized by tissue remodeling and in promoting wound-healing and well-balanced repair in humans. NGF effects are mediated by the specific expression of the NGF neurotrophic tyrosine kinase receptor type 1 (trkA(NGFR)) and/or the pan-neurotrophin glycoprotein receptor (p75(NTR)). Therefore, a conjunctival myoFB model (TGFβ1-induced myoFB) was developed and characterized for cell viability/proliferation as well as αSMA, p75(NTR) and trkA(NGFR) expression. MyoFB were exposed to acute and chronic NGF treatment and examined for their p75(NTR)/trkA(NGFR), αSMA/TGFβ1 expression, and apoptosis. Both NGF treatments significantly increased the expression of p75(NTR), associated with a deregulation of both αSMA/TGFβ1 genes. Acute and chronic NGF exposures induced apoptosis in p75(NTR) expressing myoFB, an effect counteracted by the specific trkA(NGFR) and/or p75(NTR) inhibitors. Focused single p75(NTR) and double trkA(NGFR)/p75(NTR) knocking-down experiments highlighted the role of p75(NTR) in NGF-induced apoptosis. Our current data indicate that NGF is able to trigger in vitro myoFB apoptosis, mainly via p75(NTR). The trkA(NGFR)/p75(NTR) ratio in favor of p75(NTR) characterizes this process. Due to the lack of effective pharmacological agents for balanced tissue repairs, these new findings suggest that NGF might be a suitable therapeutic tool in conditions with impaired tissue healing.

Matrigel, but not collagen I, maintains the differentiation capacity of muscle derived cells in vitro

Satellite cells are key cells for post-natal muscle growth and regeneration and they play a central role in the search for therapies to treat muscle injuries. In this study the proliferation and differentiation capacity of muscle progenitor cells was studied in 2D and 3D cultures with collagen type I and Matrigel, which contain the niche factors laminin and collagen type IV. Muscle progenitor cells were cultured to induce proliferation and differentiation in collagen- or Matrigel-coated surfaces (2D) or in gels (3D). In the 2D cultures, muscle progenitor cells proliferated faster in Matrigel than in collagen. The numbers of Pax7(+) and MyoD(+) cells were also significantly higher in Matrigel than in collagen. During differentiation, muscle progenitor cells formed more and larger MyoD(+) and myogenin(+) myotubes in Matrigel. In the 3D cultures, muscle progenitor cells in Matrigel expressed higher mRNA levels of MyoD and myogenin, and formed elongated myotubes expressing myogenin and myosin. In collagen gels, the myotubes were short and rounded. In conclusion, muscle progenitor cells, both in 2D and 3D, lose their differentiation capacity in collagen but not in Matrigel. Although Matrigel contains growth factors, our results indicate that the kind of biomaterial steers the maintenance of the myogenic potential and their proper differentiation to achieve optimal skeletal muscle restoration.

Treatment of skeletal muscle injury: a review

Skeletal muscle injuries are the most common sports-related injuries and present a challenge in primary care and sports medicine. Most types of muscle injuries would follow three stages: the acute inflammatory and degenerative phase, the repair phase and the remodeling phase. Present conservative treatment includes RICE (rest, ice, compression, elevation), nonsteroidal anti-inflammatory drugs (NSAIDs) and physical therapy. However, if use improper, NSAIDs may suppress an essential inflammatory phase in the healing of injured skeletal muscle. Furthermore, it remains controversial whether or not they have adverse effects on the healing process or on the tensile strength. However, several growth factors might promote the regeneration of injured skeletal muscle, many novel treatments have involved on enhancing complete functional recovery. Exogenous growth factors have been shown to regulate satellite cell proliferation, differentiation and fusion in myotubes in vivo and in vitro, TGF-β1 antagonists behave as inhibitors of TGF-β1. They prevent collagen deposition and block formation of muscle fibrosis, so that a complete functional recovery can be achieved.

BIOLOGICAL INTERVENTION BASED ON CELL AND GENE THERAPY TO IMPROVE MUSCLE HEALING AFTER LACERATION

Muscle laceration is a challenging problem in traumatology and is common in sports injuries, with functional recovery remaining slow and incomplete. Even though muscles retain their ability to regenerate after injury, muscles' healing process after such injuries has been found to be very slow and often leads to incomplete muscle recovery. Growth factors may have a role in enhancing recovery. Our previous study showed that IGF-1, β-FGF and NGF can improve myoblast proliferation and differentiation in vitro. We then investigated whether the delivery of IGF-1 would improve muscle healing after injuries. We observed that muscle regeneration was enhanced in lacerated muscles treated with IGF-1 protein, which consequently led to an improvement in muscle healing. However, the rapid clearance and short biological half-lives of these proteins may have limited the success of this approach. We then investigated the efficiency of gene therapy based on adenovirus to deliver a stable expression of the growth factor IGF-1. Although a slight improvement in the healing process occurred in the muscle injected with adenovirus (AIGF), the combination of myoblast transplantation and gene therapy with the ex vivo approach further improved the healing process. The injection of normal myoblasts into the injured muscle led to the best improvement of muscle healing at two weeks post-injection. Implantation of normal minced muscle into mdx mice was also capable of improving muscle healing at 2–4 weeks post-implantation. These studies will further our understanding of muscle healing post-injury and help in the development of strategies to promote efficient muscle healing and complete functional recovery after common muscle injuries.

Tissue engineered strategies for skeletal muscle injury

Skeletal muscle injuries are common in athletes, occurring with direct and indirect mechanisms and marked residual effects, such as severe long-term pain and physical disability. Current therapy consists of conservative management including RICE protocol (rest, ice, compression and elevation), nonsteroidal anti-inflammatory drugs, and intramuscular corticosteroids. However, current management of muscle injuries often does not provide optimal restoration to preinjury status. New biological therapies, such as injection of platelet-rich plasma and stem-cell-based therapy, are appealing. Although some studies support PRP application in muscle-injury management, reasons for concern persist, and further research is required for a standardized and safe use of PRP in clinical practice. The role of stem cells needs to be confirmed, as studies are still limited and inconsistent. Further research is needed to identify mechanisms involved in muscle regeneration and in survival, proliferation, and differentiation of stem cells.

The effect of steroid-abuse on anatomic reinsertion of ruptured distal biceps brachii tendon

INTRODUCTION

There is an increase in the number of anabolic-steroid (AS)-abusing trainees, who suffer from sports injuries, needing reconstruction surgery. Rupture of the distal biceps brachii tendon is a common injury in this group.

PURPOSE

The study aimed to investigate the effect of AS abuse in the anatomic reconstruction of the ruptured distal biceps brachii tendon along with an immediate range-of-motion postoperative protocol.

METHODS

We conducted an observation study of 17 male athletes suffering from distal biceps tendon ruptures. Six of them reported that they abused AS (group A), whereas the non-users comprised group B (n=11). Both groups were treated with the modified single-incision technique with two suture anchors and an immediate active range-of-motion protocol postoperatively. Follow-up was at 4, 16 and 52 weeks postoperatively, with a final follow-up at 24 months.

RESULTS

Follow-up at 4, 16 and 52 weeks postoperatively showed a statistical significance in favour of group A for therapeutic outcomes concerning flexion, supination, pronation, Disabilities of the Arm, Shoulder and Hand (DASH) Disability Symptom Scores, Mayo Elbow Performance Elbow Scores and isometric muscle strength tests for both flexion and supination. Twenty-four months postoperatively, statistical significance in favour of group A was recorded in isometric muscle strength tests for both flexion and supination and also in DASH Disability Symptom Score.

DISCUSSION

The results of our study suggest that there is a correlation between the effect of AS and the quicker and better recuperation and rehabilitation observed in group A. Nonetheless, these results must be interpreted with caution, and further in vivo research is needed to confirm these findings.

Platelet-rich plasma (PRP) to treat sports injuries: evidence to support its use

Tissue repair in musculoskeletal lesions is often a slow and sometimes incomplete process. In sports patients or professional athletes, the impact of musculoskeletal lesions on life and work is great, and the fast recovery of full efficiency and return to competition is of primary importance. The clinical improvement offered by available treatments is not always sufficient for highly demanding patients to return to their previous level of activity. The search for a minimally invasive solution to improve the status of the chondral surface of the injured joint is therefore highly desirable, especially in these patients. Platelet-rich plasma (PRP) is a procedure that allows to obtain a natural concentration of autologous growth factors. The attractive possibility to use the patients' own growth factors to enhance reparative process in tissues with low healing potential, the promising preliminary clinical findings and the safety of these methods, explain the wide application of this biological approach. The aim of this review is to analyse the existing published studies to look for scientific evidence in preclinical studies or in the results obtained through PRP application in humans that supports the efficacy of PRP and its use for the treatment of tendinous, ligamentous, cartilaginous and muscular injuries. The analysis of the literature shows promising preclinical results but contradictory clinical findings for the treatment of sport injuries. High-quality studies are required to confirm these preliminary results and provide scientific evidence to support its use.