Laminin-111 improves skeletal muscle stem cell quantity and function following eccentric exercise

Continuous protein-density gradients: A new approach to correlate physical cues with cell response

To assess cellular behavior within heterogeneous tissues, such as bone, skin, and nerves, scaffolds with biophysical gradients are required to adequately replicate the in vivo interaction between cells and their native microenvironment. In this study, we introduce a strategy for depositing ultrathin films comprised of laminin-111 with precisely controlled biophysical gradients onto planar substrates using the Langmuir-Blodgett (LB) technique. The gradient is created by controlled desynchronization of the barrier compression and substrate withdrawal speed during the LB deposition process. Characterization of the films was performed using techniques such as atomic force microscopy and confocal fluorescence microscopy, enabling the comprehensive analysis of biophysical parameters along the gradient direction. Furthermore, human adipose-derived stem cells were seeded onto the gradient films to investigate the influence of protein density on cell attachment, showing that the distribution of the cells can be modulated by the arrangement of the laminin at the air-water interface. The presented approach not only allowed us to gain insights into the intricate interplay between biophysical cues and cell behavior within complex tissue environments, but it is also suited as a screening approach to determine optimal protein concentrations to achieve a target cellular output.

Therapeutic applications of biological macromolecules and scaffolds for skeletal muscle regeneration: A review

Skeletal muscle (SM) mass and strength maintenance are important requirements for human well-being. SM regeneration to repair minor injuries depends upon the myogenic activities of muscle satellite (stem) cells. However, losses of regenerative properties following volumetric muscle loss or severe trauma or due to congenital muscular abnormalities are not self-restorable, and thus, these conditions have major healthcare implications and pose clinical challenges. In this context, tissue engineering based on different types of biomaterials and scaffolds provides an encouraging means of structural and functional SM reconstruction. In particular, biomimetic (able to transmit biological signals) and several porous scaffolds are rapidly evolving. Several biological macromolecules/biomaterials (collagen, gelatin, alginate, chitosan, and fibrin etc.) are being widely used for SM regeneration. However, available alternatives for SM regeneration must be redesigned to make them more user-friendly and economically feasible with longer shelf lives. This review aimed to explore the biological aspects of SM regeneration and the roles played by several biological macromolecules and scaffolds in SM regeneration in cases of volumetric muscle loss.

Exercise builds the scaffold of life: muscle extracellular matrix biomarker responses to physical activity, inactivity, and aging

Skeletal muscle extracellular matrix (ECM) is critical for muscle force production and the regulation of important physiological processes during growth, regeneration, and remodelling. ECM remodelling is a tightly orchestrated process, sensitive to multi-directional tensile and compressive stresses and damaging stimuli, and its assessment can convey important information on rehabilitation effectiveness, injury, and disease. Despite its profound importance, ECM biomarkers are underused in studies examining the effects of exercise, disuse, or aging on muscle function, growth, and structure. This review examines patterns of short- and long-term changes in the synthesis and concentrations of ECM markers in biofluids and tissues, which may be useful for describing the time course of ECM remodelling following physical activity and disuse. Forces imposed on the ECM during physical activity critically affect cell signalling while disuse causes non-optimal adaptations, including connective tissue proliferation. The goal of this review is to inform researchers, and rehabilitation, medical, and exercise practitioners better about the role of ECM biomarkers in research and clinical environments to accelerate the development of targeted physical activity treatments, improve ECM status assessment, and enhance function in aging, injury, and disease.

Laminin-111-Enriched Fibrin Hydrogels Enhance Functional Muscle Regeneration Following Trauma

Volumetric muscle loss (VML) is the surgical or traumatic loss of skeletal muscle, which can cause loss of limb function or permanent disability. VML injuries overwhelms the endogenous regenerative capacity of skeletal muscle and results in poor functional healing outcomes. Currently, there are no approved tissue engineering treatments for VML injuries. In this study, fibrin hydrogels enriched with laminin-111 (LM-111; 50-450 μg/mL) were used for the treatment of VML of the tibialis anterior in a rat model. Treatment with fibrin hydrogel containing 450 μg/mL of LM-111 (FBN450) improved muscle regeneration following VML injury. FBN450 hydrogel treatment increased the relative proportion of contractile to fibrotic tissue as indicated by the myosin: collagen ratio on day 28 post-VML injury. FBN450 hydrogels also enhanced myogenic protein expression and increased the quantity of small to medium size myofibers (500-2000 μm²) as well as innervated myofibers. Improved contractile tissue deposition due to FBN450 hydrogel treatment resulted in a significant improvement (∼60%) in torque production at day 28 postinjury. Taken together, these results suggest that the acellular FBN450 hydrogels provide a promising therapeutic strategy for VML that is worthy of further investigation.

Extracellular Matrix and the Production of Cultured Meat

Cultured meat production is an evolving method of producing animal meat using tissue engineering techniques. Cells, chemical factors, and suitable biomaterials that serve as scaffolds are all essential for the cultivation of muscle tissue. Scaffolding is essential for the development of organized meat products resembling steaks because it provides the mechanical stability needed by cells to attach, differentiate, and mature. In in vivo settings, extracellular matrix (ECM) ensures substrates and scaffolds are provided for cells. The ECM of skeletal muscle (SM) maintains tissue elasticity, creates adhesion points for cells, provides a three-dimensional (3D) environment, and regulates biological processes. Consequently, creating mimics of native ECM is a difficult task. Animal-derived polymers like collagen are often regarded as the gold standard for producing scaffolds with ECM-like properties. Animal-free scaffolds are being investigated as a potential source of stable, chemically defined, low-cost materials for cultured meat production. In this review, we explore the influence of ECM on myogenesis and its role as a scaffold and vital component to improve the efficacy of the culture media used to produce cultured meat.

Biomimetic sponges improve muscle structure and function following volumetric muscle loss

Skeletal muscle is inept in regenerating after traumatic injuries such as volumetric muscle loss (VML) due to significant loss of various cellular and acellular components. Currently, there are no approved therapies for the treatment of muscle tissue following trauma. In this study, biomimetic sponges composed of gelatin, collagen, laminin-111, and FK-506 were used for the treatment of VML in a rodent model. We observed that biomimetic sponge treatment improved muscle structure and function while modulating inflammation and limiting the extent of fibrotic tissue deposition. Specifically, sponge treatment increased the total number of myofibers, type 2B fiber cross-sectional area, myosin: collagen ratio, myofibers with central nuclei, and peak isometric torque compared to untreated VML injured muscles. As an acellular scaffold, biomimetic sponges may provide a promising clinical therapy for VML.

Co-delivery of fibrin-laminin hydrogel with mesenchymal stem cell spheroids supports skeletal muscle regeneration following trauma

Volumetric muscle loss (VML) is traumatic or surgical loss of skeletal muscle with resultant functional impairment. Skeletal muscle's innate capacity for regeneration is lost with VML due to a critical loss of stem cells, extracellular matrix, and neuromuscular junctions. Consequences of VML include permanent disability or delayed amputations of the affected limb. Currently, a successful clinical therapy has not been identified. Mesenchymal stem cells (MSCs) possess regenerative and immunomodulatory properties and their three-dimensional aggregation can further enhance therapeutic efficacy. In this study, MSC aggregation into spheroids was optimized in vitro based on cellular viability, spheroid size, and trophic factor secretion. The regenerative potential of the optimized MSC spheroid therapy was then investigated in a murine model of VML injury. Experimental groups included an untreated VML injury control, intramuscular injection of MSC spheroids, and MSC spheroids encapsulated in a fibrin-laminin hydrogel. Compared to the untreated VML group, the spheroid encapsulating hydrogel group enhanced myogenic marker (i.e., MyoD and myogenin) protein expression, improved muscle mass, increased presence of centrally nucleated myofibers as well as small fibers (<500 μm² ), modulated pro- and anti-inflammatory macrophage marker expression (i.e., iNOS and Arginase), and increased the presence of CD146⁺ pericytes and CD31⁺ endothelial cells in the VML injured muscles. Future studies will evaluate the extent of functional recovery with the spheroid encapsulating hydrogel therapy.

Laminin-111 Improves the Anabolic Response to Mechanical Load in Aged Skeletal Muscle

Anabolic resistance to a mechanical stimulus may contribute to the loss of skeletal muscle mass observed with age. In this study, young and aged mice were injected with saline or human LM-111 (1 mg/kg). One week later, the myotendinous junction of the gastrocnemius muscle was removed via myotenectomy (MTE), thus placing a chronic mechanical stimulus on the remaining plantaris muscle for 2 weeks. LM-111 increased α7B integrin protein expression and clustering of the α7B integrin near DAPI+ nuclei in aged muscle in response to MTE. LM-111 reduced CD11b+ immune cells, enhanced repair, and improved the growth response to loading in aged plantaris muscle. These results suggest that LM-111 may represent a novel therapeutic approach to prevent and/or treat sarcopenia.

Extracellular matrix: an important regulator of cell functions and skeletal muscle development

Extracellular matrix (ECM) is a kind of connective tissue in the cell microenvironment, which is of great significance to tissue development. ECM in muscle fiber niche consists of three layers: the epimysium, the perimysium, and the endomysium (basal lamina). These three layers of connective tissue structure can not only maintain the morphology of skeletal muscle, but also play an important role in the physiological functions of muscle cells, such as the transmission of mechanical force, the regeneration of muscle fiber, and the formation of neuromuscular junction. In this paper, detailed discussions are made for the structure and key components of ECM in skeletal muscle tissue, the role of ECM in skeletal muscle development, and the application of ECM in biomedical engineering. This review will provide the reader with a comprehensive overview of ECM, as well as a comprehensive understanding of the structure, physiological function, and application of ECM in skeletal muscle tissue.

Laminin-111 protein therapy enhances muscle regeneration and repair in the GRMD dog model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a devastating X-linked disease affecting ~1 in 5000 males. DMD patients exhibit progressive muscle degeneration and weakness, leading to loss of ambulation and premature death from cardiopulmonary failure. We previously reported that mouse Laminin-111 (msLam-111) protein could reduce muscle pathology and improve muscle function in the mdx mouse model for DMD. In this study, we examined the ability of msLam-111 to prevent muscle disease progression in the golden retriever muscular dystrophy (GRMD) dog model of DMD. The msLam-111 protein was injected into the cranial tibial muscle compartment of GRMD dogs and muscle strength and pathology were assessed. The results showed that msLam-111 treatment increased muscle fiber regeneration and repair with improved muscle strength and reduced muscle fibrosis in the GRMD model. Together, these findings support the idea that Laminin-111 could serve as a novel protein therapy for the treatment of DMD.

Skeletal muscles induce recruitment of Ly6C+ macrophage subtypes and release inflammatory cytokines 3 days after downhill exercise

Macrophages are one of the most versatile cells of the immune system that can express distinct subtypes and functions depending on the physiological challenge. After skeletal muscle damage, inflammatory macrophage subtypes aid muscles to regenerate and are implicated in physical training adaption. Based on this information, this study aimed to evaluate two classic mice macrophage subtypes and determine whether some inflammatory cytokines might be involved in the muscle adaption process after exercise. For this purpose, mice were exposed to an intermittent experimental protocol of downhill exercise (18 bouts of running, each bout 5 min with a 2-min rest interval, slope -16°) and were euthanized before [control (CTRL)] and 1, 2 (D2), and 3 (D3) days after exercise. After euthanasia, the triceps brachii was harvested and submitted to protein extraction, immunostaining, and mononuclear digestion procedures. The muscle size, macrophage accumulation, and cytokines were determined. We observed an increase in the Ly6C⁺ macrophage subtype (P ≤ 0.05) in D2 and D3 compared with CTRL, as well as a significant inverse correlation coefficient (-0.52; P ≤ 0.05) between Ly6C⁺ and Ly6C^- macrophage subtypes. Moreover, we also observed elevation in several cytokines (IL-1β, IFN-γ, TNF-α, IL-6, and IL-13) at D3, although not IL-4, which tended to decrease at this time point (P = 0.06). Downhill exercises preferentially recruited Ly6C⁺ macrophages with important proinflammatory cytokine elevation at D3. Moreover, despite the elevation of several cytokines involved with myogenesis, an increase in IL-6 and IL-13, which potentially involve muscle adaption training after acute exercise, was also observed.

Regulation of Myogenic Activity by Substrate and Electrical Stimulation In Vitro

Skeletal muscle has a remarkable regenerative capacity in response to mild injury. However, when muscle is severely injured, muscle regeneration is impaired due to the loss of muscle-resident stem cells, known as satellite cells. Fibrotic tissue, primarily comprising collagen I (COL), is deposited with this critical loss of muscle. In recent studies, supplementation of laminin (LM)-111 has been shown to improve skeletal muscle regeneration in several models of disease and injury. Additionally, electrical stimulation (E-stim) has been investigated as a possible rehabilitation therapy to improve muscle's functional recovery. This study investigated the role of E-stim and substrate in regulating myogenic response. C2C12 myoblasts were allowed to differentiate into myotubes on COL- and LM-coated polydimethylsiloxane molds. The myotubes were subjected to E-stim and compared with nonstimulated controls. While E-stim resulted in increased myogenic activity, irrespective of substrate, LM supported increased proliferation and uniform distribution of C2C12 myoblasts. In addition, C2C12 myoblasts cultured on LM showed higher Sirtuin 1, mammalian target of rapamycin, desmin, nitric oxide, and vascular endothelial growth factor expression. Taken together, these results suggest that an LM substrate is more conducive to myoblast growth and differentiation in response to E-stim in vitro.

The Effect of Laminin-111 Hydrogels on Muscle Regeneration in a Murine Model of Injury

IMPACT STATEMENT

Extremity injuries make up the most common survivable injuries in vehicular accidents and modern military conflicts. A majority of these injuries involve volumetric muscle loss (VML). The potential for donor site morbidity may limit the clinical use of autologous muscle grafts for VML injuries. Treatments that can improve the regeneration of functional muscle tissue are critically needed to improve limb salvage and reduce the rate of delayed amputations. The development of a laminin-111-enriched fibrin hydrogel will offer a potentially transformative and "off-the-shelf" clinically relevant therapy for functional skeletal muscle regeneration.

Aligned nanofibers of decellularized muscle ECM support myogenic activity in primary satellite cells in vitro

Volumetric muscle loss (VML) is a loss of over ∼10% of muscle mass that results in functional impairment. Although skeletal muscle possesses the ability to repair and regenerate itself following minor injuries, VML injuries are irrecoverable. Currently, there are no successful clinical therapies for the treatment of VML. Previous studies have treated VML defects with decellularized extracellular matrix (D-ECM) scaffolds derived from either pig urinary bladder or small intestinal submucosa. These therapies were unsuccessful due to the poor mechanical stability of D-ECM leading to quick degradation in vivo. To circumvent these issues, in this manuscript aligned nanofibers of D-ECM were created using electrospinning that mimicked native muscle architecture and provided topographical cues to primary satellite cells. Additionally, combining D-ECM with polycaprolactone (PCL) improved the tensile mechanical properties of the electrospun scaffold. In vitro testing shows that the electrospun scaffold with aligned nanofibers of PCL and D-ECM supports satellite cell growth, myogenic protein expression, and myokine production.

Biomimetic sponges for regeneration of skeletal muscle following trauma

Skeletal muscle is inept in regenerating after traumatic injuries due to significant loss of basal lamina and the resident satellite cells. To improve regeneration of skeletal muscle, we have developed biomimetic sponges composed of collagen, gelatin, and laminin (LM)-111 that were crosslinked with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC). Collagen and LM-111 are crucial components of the muscle extracellular matrix and were chosen to impart bioactivity whereas gelatin and EDC were used to provide mechanical strength to the scaffold. Morphological and mechanical evaluation of the sponges showed porous structure, water-retention capacity and a compressive modulus of 590-808 kPa. The biomimetic sponges supported the infiltration and viability of C₂ C₁₂ myoblasts over 5 days of culture. The myoblasts produced higher levels of myokines such as VEGF, IL-6, and IGF-1 and showed higher expression of myogenic markers such as MyoD and myogenin on the biomimetic sponges. Biomimetic sponges implanted in a mouse model of volumetric muscle loss (VML) supported satellite, endothelial, and inflammatory cell infiltration but resulted in limited myofiber regeneration at 2 weeks post-injury. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 92-103, 2019.

Laminin-111 functionalized polyethylene glycol hydrogels support myogenic activity in vitro

Skeletal muscle has a remarkable regenerative capability following mild physical or chemical insult. However, following a critical loss of muscle tissue, the regeneration process is impaired due to the inadequate myogenic activity of muscle resident stem cells (i.e., satellite cells). Laminin (LM) is a heterotrimeric structural protein in the satellite cell niche that is crucial for maintaining its function. In this study, we created hydrogels composed of poly (ethylene glycol) (PEG) and LM-111 to provide an elastic substrate for satellite cell proliferation at the site of injury. The PEG-LM111 conjugates were mixed with 5% and 10% (w/v) pure PEG-diacrylate (PEGDA) and photopolymerized to form 5% and 10% PEGLM gels. Pure 5% and 10% PEGDA gels were used as controls. The modulus of both hydrogels containing 10% (w/v) PEGDA was significantly higher than the hydrogels containing 5% (w/v) PEGDA. The 5% PEGLM hydrogels showed significantly higher swelling in aqueous medium suggesting a more porous structure. C₂C₁₂ myoblasts cultured on the softer 5% PEGLM hydrogels showed a flat and spread-out morphology when compared to the rounded, multicell clusters formed on the 5% PEGDA, 10% PEGDA, and 10% PEGLM hydrogels. The 5% PEGLM hydrogels also promoted a significant increase in both vascular endothelial growth factor and interleukin-6 (IL-6) production from the myoblasts. Additionally, the expression of MyoD was significantly higher while that of myogenin and α-actinin trended higher on the 5% PEGLM hydrogels compared to 5% PEGDA on day 5. Our data suggests that the introduction of LM-111 into compliant PEG hydrogels promoted myoblast adhesion, survival, pro-regenerative growth factor production, and myogenic activity.

Co-delivery of a laminin-111 supplemented hyaluronic acid based hydrogel with minced muscle graft in the treatment of volumetric muscle loss injury

Minced muscle autografting mediates de novo myofiber regeneration and promotes partial recovery of neuromuscular strength after volumetric muscle loss injury (VML). A major limitation of this approach is the availability of sufficient donor tissue for the treatment of relatively large VMLs without inducing donor site morbidity. This study evaluated a laminin-111 supplemented hyaluronic acid based hydrogel (HA+LMN) as a putative myoconductive scaffolding to be co-delivered with minced muscle grafts. In a rat tibialis anterior muscle VML model, delivery of a reduced dose of minced muscle graft (50% of VML defect) within HA+LMN resulted in a 42% improvement of peak tetanic torque production over unrepaired VML affected limbs. However, the improvement in strength was not improved compared to a 50% minced graft-only control group. Moreover, histological analysis revealed that the improvement in in vivo functional capacity mediated by minced grafts in HA+LMN was not accompanied by a particularly robust graft mediated regenerative response as determined through donor cell tracking of the GFP+ grafting material. Characterization of the spatial distribution and density of macrophage and satellite cell populations indicated that the combination therapy damps the heightened macrophage response while re-establishing satellite content 14 days after VML to a level consistent with an endogenously healing ischemia-reperfusion induced muscle injury. Moreover, regional analysis revealed that the combination therapy increased satellite cell density mostly in the remaining musculature, as opposed to the defect area. Based on the results, the following salient conclusions were drawn: 1) functional recovery mediated by the combination therapy is likely due to a superposition of de novo muscle fiber regeneration and augmented repair of muscle fibers within the remaining musculature, and 2) The capacity for VML therapies to augment regeneration and repair within the remaining musculature may have significant clinical impact and warrants further exploration.

Recapitulation of Extracellular LAMININ Environment Maintains Stemness of Satellite Cells In Vitro

Satellite cells function as precursor cells in mature skeletal muscle homeostasis and regeneration. In healthy tissue, these cells are maintained in a state of quiescence by a microenvironment formed by myofibers and basement membrane in which LAMININs (LMs) form a major component. In the present study, we evaluated the satellite cell microenvironment in vivo and found that these cells are encapsulated by LMα2–5. We sought to recapitulate this satellite cell niche in vitro by culturing satellite cells in the presence of recombinant LM-E8 fragments. We show that treatment with LM-E8 promotes proliferation of satellite cells in an undifferentiated state, through reduced phosphorylation of JNK and p38. On transplantation into injured muscle tissue, satellite cells cultured with LM-E8 promoted the regeneration of skeletal muscle. These findings represent an efficient method of culturing satellite cells for use in transplantation through the recapitulation of the satellite cell niche using recombinant LM-E8 fragments.

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Satellite cells are encapsulated by LMα2–5

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LM-E8 promotes proliferation of satellite cells in an undifferentiated state

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Satellite cells cultured with LM-E8 enhanced the regeneration of skeletal muscle

Human Placenta Laminin-111 as a Multifunctional Protein for Tissue Engineering and Regenerative Medicine

Laminins are major components of all basement membranes surrounding nerve or vascular tissues. In particular laminin-111, the prototype of the family, facilitates a large spectrum of fundamental cellular responses in all eukaryotic cells. Laminin-111 is a biomaterial frequently used in research, however it is primarily isolated from non-human origin or produced with time-intensive recombinant techniques at low yield.Here, we describe an effective method for isolating laminin-111 from human placenta, a clinical waste material, for various tissue engineering applications. By extraction with Tris-NaCl buffer combined with non-protein-denaturation ammonium sulfate precipitation and rapid tangential flow filtration steps, we could effectively isolate native laminin-111 within only 4 days. The resulting material was biochemically characterized using a combination of dot blot, SDS-PAGE, Western blot and HPLC-based amino acid analysis. Cytocompatibility studies demonstrated that the isolated laminin-111 promotes rapid and efficient adhesion of primary Schwann cells. In addition, the bioactivity of the isolated laminin-111 was demonstrated by (a) using the material as a substrate for outgrowth of NG 108-15 neuronal cell lines and (b) promoting the formation of interconnected vascular networks by GFP-expressing human umbilical vein endothelial cells.In summary, the isolation procedure of laminin-111 as described here from human placenta tissue, fulfills many demands for various tissue engineering and regenerative medicine approaches and therefore may represent a human alternative to various classically used xenogenic standard materials.

Laminin-111 enriched fibrin hydrogels for skeletal muscle regeneration

Laminin (LM)-111 supplementation has improved muscle regeneration in several models of disease and injury. This study investigated a novel hydrogel composed of fibrinogen and LM-111. Increasing LM-111 concentration (50-450 μg/mL) in fibrin hydrogels resulted in highly fibrous scaffolds with progressively thinner interlaced fibers. Rheological testing showed that all hydrogels had viscoelastic behavior and the Young's modulus ranged from 2-6KPa. C₂C₁₂ myobalsts showed a significant increase in VEGF production and decrease in IL-6 production on LM-111 enriched fibrin hydrogels as compared to pure fibrin hydrogels on day 4. Western blotting results showed a significant increase in MyoD and desmin protein quantity but a significant decrease in myogenin protein quantity in myoblasts cultured on the LM-111 (450 μg/mL) enriched fibrin hydrogel. Combined application of electromechanical stimulation significantly enhanced the production of VEGF and IGF-1 from myoblast seeded fibrin-LM-111 hydrogels. Taken together, these observations offer an important first step toward optimizing a tissue engineered constructs for skeletal muscle regeneration.

Unexpected evolutionarily conserved rapid effects of viral infection on oxytocin receptor and TGF-β/pSmad3

Background

shRNA lentiviral vectors are extensively used for gene knockdowns in mammalian cells, and non-target shRNAs typically are considered the proper experimental control for general changes caused by RNAi. However, the effects of non-target lentivirus controls on the modulation of cell signaling pathways remain largely unknown. In this study, we evaluated the effect of control lentiviral transduction on oxytocin receptor (OXTR) expression through the ERK/MAPK pathway in mouse and human skeletal muscle cells, on myogenic activity, and in vivo on mouse muscle regeneration. Furthermore, we mined published data for the influence of viral infections on OXTR levels in human populations and found that unrelated viral pathologies have a common consequence: diminished levels of OXTR.

Methods

We examined the change in OXTR mRNA expression upon transduction with control and Smad3-targeting viral vectors through real time RT-PCR and Western blotting, and confirmed with immunofluorescence. Changes in Smad3 and OXTR expression were examined both in vitro with mouse and human myoblasts and in vivo in mouse satellite cells. The general effects of viral infections on OXTR downregulation in humans were also examined by analyzing published Gene Expression Omnibus (GEO) datasets. The change in myoblast myogenic activity caused by the viral transduction (the percent of Pax7 + Ki67+ cells) was examined by immunofluorescence.

Results

Results shown in this work establish that lentiviral control vectors significantly downregulate OXTR expression at mRNA and protein levels and diminish key downstream effectors of OXTR, ERK signaling, reducing the myogenic proliferation of infected cells. This effect is evolutionarily conserved between mouse and human myogenic cells, and it manifests in satellite cells after control lentiviral transduction of mice in vivo. Furthermore, an examination of published datasets uncovered similar OXTR downregulation in humans that are afflicted with different viral infections. Additionally, cells transduced with Smad3-targeting shRNA downregulate OXTR even more than cells transduced with control viruses.

Conclusions

Our work suggests that experimental cohorts transduced with control viruses may not behave the same as un-transduced cells and animals, specifically that control viral vectors significantly change the intensity of key cell-signaling pathways, such as OXTR/ERK. Our results further demonstrate that lentiviral transduction significantly decreases myogenic proliferation and suggest that viral infections in general may play a role in decreasing muscle health and regeneration, a decline in metabolic health, and a lower sense of well-being, as these rely on effective OXTR signaling. Additionally, our data suggest pathway crosstalk between TGF-β/pSmad3 and OXTR, implying that sustained attenuation of the TGF-β/pSmad3 pathway will reduce pro-regenerative OXTR/pERK signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s13395-017-0125-y) contains supplementary material, which is available to authorized users.

Sexual dimorphism in laryngeal muscle fibers and ultrasonic vocalizations in the adult rat

OBJECTIVE

The human voice is sexually dimorphic in obvious ways, such as differences in fundamental frequency and gross laryngeal anatomy, but also in less apparent ways, such as in the prevalence and types of voice disorders and the manifestation of voice changes in advanced age. Differences between males and females are rarely explored, however, in mechanistic animal studies. The goal of this study was to explore sexual dimorphism in laryngeal function and structure in adult rats by examining ultrasonic vocalization acoustics and muscle fiber size and type in the thyroarytenoid muscle.

STUDY DESIGN

Animal group comparison.

METHODS

Spontaneous ultrasonic vocalizations from 10 male adult rats and 10 female adult rats were recorded, classified, and acoustically analyzed. Cross-sections of the thyroarytenoid muscle were stained and imaged for analysis of muscle fiber size and type. Acoustic and muscle parameters were statistically compared between sexes.

RESULTS

Male rats had a lower mean frequency of short ultrasonic vocalizations. Male rats also had a larger mean fiber size in the external division of the thyroarytenoid and larger overall muscle area in both the vocalis and external divisions of the thyroarytenoid. However, muscle fiber type compositions were similar between sexes in both the vocalis and external division of the thyroarytenoid muscles.

CONCLUSION

Functional and structural laryngeal differences exist between adult male and female rats; therefore, the rat model can be used to further study sexual dimorphism of the voice.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E270-E276, 2017.

Increased Expression of Laminin Subunit Alpha 1 Chain by dCas9-VP160

Laminin-111 protein complex links the extracellular matrix to integrin α7β1 in sarcolemma, thus replacing in dystrophic muscles links normally insured by the dystrophin complex. Laminin-111 injection in mdx mouse stabilized sarcolemma, restored serum creatine kinase to wild-type levels, and protected muscles from exercised-induced damages. These results suggested that increased laminin-111 is a potential therapy for DMD. Laminin subunit beta 1 and laminin subunit gamma 1 are expressed in adult human muscle, but laminin subunit alpha 1 (LAMA1) gene is expressed only during embryogenesis. We thus developed an alternative method to laminin-111 protein repeated administration by inducing expression of the endogenous mouse Lama1 gene. This was done with the CRSPR/Cas9 system, i.e., by targeting the Lama1 promoter with one or several gRNAs and a dCas9 coupled with the VP160 transcription activation domain. Lama1 mRNA (qRT-PCR) and proteins (immunohistochemistry and western blot) were not detected in the control C2C12 myoblasts and in control muscles. However, significant expression was observed in cells transfected and in mouse muscles electroporated with plasmids coding for dCas9-VP160 and a gRNA. Larger synergic increases were observed by using two or three gRNAs. The increased Lama1 expression did not modify the expression of the α7 and β1 integrins. Increased expression of Lama1 by the CRISPR/Cas9 system will have to be further investigated by systemic delivery of the CRISPR/Cas9 components to verify whether this could be a treatment for several myopathies.

Rehabilitation Considerations in Regenerative Medicine

Rehabilitation and regenerative medicine therapies has shown improved outcomes for tissue regeneration. Regenerative rehabilitation guides protocols regarding when to start therapy, types of stimuli administered, and graded exercise programs, taking into account biological factors and technologies designed to optimize healing potential. Although there are currently no evidence-based guidelines for rehabilitation, fundamental physical therapy principles likely apply. Immobilization tends to have deleterious effects on musculoskeletal tissues; mechanical loading promotes tissue healing and regeneration. Common physical therapy interventions may provide beneficial effects after the application of regenerative therapies. Research is needed to determine optimal rehabilitation protocols to enhance tissue healing and regeneration.

Influence of exercise and aging on extracellular matrix composition in the skeletal muscle stem cell niche

Skeletal muscle is endowed with a remarkable capacity for regeneration, primarily due to the reserve pool of muscle resident satellite cells. The satellite cell is the physiologically quiescent muscle stem cell that resides beneath the basal lamina and adjacent to the sarcolemma. The anatomic location of satellite cells is in close proximity to vasculature where they interact with other muscle resident stem/stromal cells (e.g., mesenchymal stem cells and pericytes) through paracrine mechanisms. This mini-review describes the components of the muscle stem cell niche, as well as the influence of exercise and aging on the muscle stem cell niche. Although exercise promotes ECM reorganization and stem cell accumulation, aging is associated with dense ECM deposition and loss of stem cell function resulting in reduced regenerative capacity and strength. An improved understanding of the niche elements will be valuable to inform the development of therapeutic interventions aimed at improving skeletal muscle regeneration and adaptation over the life span.

In vivo evaluation of adipose- and muscle-derived stem cells as a treatment for nonhealing diabetic wounds using multimodal microscopy

Impaired skin wound healing is a significant comorbid condition of diabetes, which often results in nonhealing diabetic ulcers due to poor peripheral microcirculation, among other factors. The effectiveness of the regeneration of adipose-derived stem cells (ADSCs) and muscle-derived stem cells (MDSCs) was assessed using an integrated multimodal microscopy system equipped with two-photon fluorescence and second-harmonic generation imaging. These imaging modalities, integrated in a single platform for spatial and temporal coregistration, allowed us to monitor in vivo changes in the collagen network and cell dynamics in a skin wound. Fluorescently labeled ADSCs and MDSCs were applied topically to the wound bed of wild-type and diabetic (db/db) mice following punch biopsy. Longitudinal imaging demonstrated that ADSCs and MDSCs provided remarkable capacity for improved diabetic wound healing, and integrated microscopy revealed a more organized collagen remodeling in the wound bed of treated mice. The results from this study verify the regenerative capacity of stem cells toward healing and, with multimodal microscopy, provide insight regarding their impact on the skin microenvironment. The optical method outlined in this study, which has the potential for in vivo human use, may optimize the care and treatment of diabetic nonhealing wounds.

Engineered matrices for skeletal muscle satellite cell engraftment and function

Regeneration of traumatically injured skeletal muscles is severely limited. Moreover, the regenerative capacity of skeletal muscle declines with aging, further exacerbating the problem. Recent evidence supports that delivery of muscle satellite cells to the injured muscles enhances muscle regeneration and reverses features of aging, including reduction in muscle mass and regenerative capacity. However, direct delivery of satellite cells presents a challenge at a translational level due to inflammation and donor cell death, motivating the need to develop engineered matrices for muscle satellite cell delivery. This review will highlight important aspects of satellite cell and their niche biology in the context of muscle regeneration, and examine recent progresses in the development of engineered cell delivery matrices designed for skeletal muscle regeneration. Understanding the interactions of muscle satellite cells and their niche in both native and engineered systems is crucial to developing muscle pathology-specific cell- and biomaterial-based therapies.