Electric pulses augment reporter gene expression in the beating heart

Enhanced capacity for CaMKII signaling mitigates calcium release related contractile fatigue with high intensity exercise

BACKGROUND

We tested whether enhancing the capacity for calcium/calmodulin-dependent protein kinase type II (CaMKII) signaling would delay fatigue of excitation-induced calcium release and improve contractile characteristics of skeletal muscle during fatiguing exercise.

METHODS

Fast and slow type muscle, gastrocnemius medialis (GM) and soleus (SOL), of rats and mouse interosseus (IO) muscle fibers, were transfected with pcDNA3-based plasmids for rat α and β CaMKII or empty controls. Levels of CaMKII, its T287-phosphorylation (pT287-CaMKII), and phosphorylation of components of calcium release and re-uptake, ryanodine receptor 1 (pS2843-RyR1) and phospholamban (pT17-PLN), were quantified biochemically. Sarcoplasmic calcium in transfected muscle fibers was monitored microscopically during trains of electrical excitation based on Fluo-4 FF fluorescence (n = 5-7). Effects of low- (n = 6) and high- (n = 8) intensity exercise on pT287-CaMKII and contractile characteristics were studied in situ.

RESULTS

Co-transfection with αCaMKII-pcDNA3/βCaMKII-pcDNA3 increased α and βCaMKII levels in SOL (+45.8 %, +250.5 %) and GM (+40.4 %, +89.9 %) muscle fibers compared to control transfection. High-intensity exercise increased pT287-βCaMKII and pS2843-RyR1 levels in SOL (+269 %, +151 %) and GM (+354 %, +119 %), but decreased pT287-αCaMKII and p17-PLN levels in GM compared to SOL (-76 % vs. +166 %; 0 % vs. +128 %). α/β CaMKII overexpression attenuated the decline of calcium release in muscle fibers with repeated excitation, and mitigated exercise-induced deterioration of rates in force production, and passive force, in a muscle-dependent manner, in correlation with pS2843-RyR1 and pT17-PLN levels (|r| > 0.7).

CONCLUSION

Enhanced capacity for α/β CaMKII signaling improves fatigue-resistance of active and passive contractile muscle properties in association with RyR1- and PLN-related improvements in sarcoplasmic calcium release.

Transplant of Autologous Mesenchymal Stem Cells Halts Fatty Atrophy of Detached Rotator Cuff Muscle After Tendon Repair: Molecular, Microscopic, and Macroscopic Results From an Ovine Model

BACKGROUND

The injection of mesenchymal stem cells (MSCs) mitigates fat accumulation in released rotator cuff muscle after tendon repair in rodents.

PURPOSE

To investigate whether the injection of autologous MSCs halts muscle-to-fat conversion after tendon repair in a large animal model for rotator cuff tendon release via regional effects on extracellular fat tissue and muscle fiber regeneration.

STUDY DESIGN

Controlled laboratory study.

METHODS

Infraspinatus (ISP) muscles of the right shoulder of Swiss Alpine sheep (n = 14) were released by osteotomy and reattached 16 weeks later without (group T; n = 6) or with (group T-MSC; n = 8) electropulse-assisted injection of 0.9 Mio fluorescently labeled MSCs as microtissues with media in demarcated regions; animals were allowed 6 weeks of recovery. ISP volume and composition were documented with computed tomography and magnetic resonance imaging. Area percentages of muscle fiber types, fat, extracellular ground substance, and fluorescence-positive tissue; mean cross-sectional area (MCSA) of muscle fibers; and expression of myogenic (myogenin), regeneration (tenascin-C), and adipogenic markers (peroxisome proliferator-activated receptor gamma [PPARG2]) were quantified in injected and noninjected regions after recovery.

RESULTS

At 16 weeks after tendon release, the ISP volume was reduced and the fat fraction of ISP muscle was increased in group T (137 vs 185 mL; 49% vs 7%) and group T-MSC (130 vs 166 mL; 53% vs 10%). In group T-MSC versus group T, changes during recovery after tendon reattachment were abrogated for fat-free mass (-5% vs -29%, respectively; P = .018) and fat fraction (+1% vs +24%, respectively; P = .009%). The area percentage of fat was lower (9% vs 20%; P = .018) and the percentage of the extracellular ground substance was higher (26% vs 20%; P = .007) in the noninjected ISP region for group T-MSC versus group T, respectively. Regionally, MCS injection increased tenascin-C levels (+59%) and the water fraction, maintaining the reduced PPARG2 levels but not the 29% increased fiber MCSA, with media injection.

CONCLUSION

In a sheep model, injection of autologous MSCs in degenerated rotator cuff muscle halted muscle-to-fat conversion during recovery from tendon repair by preserving fat-free mass in association with extracellular reactions and stopping adjuvant-induced muscle fiber hypertrophy.

CLINICAL RELEVANCE

A relatively small dose of MSCs is therapeutically effective to halt fatty atrophy in a large animal model.

Focal adhesion kinase coordinates costamere-related JNK signaling with muscle fiber transformation after Achilles tenotomy and tendon reconstruction

Achilles tendon rupture necessitates rapid tendon reattachment to reinstate plantar flexion before affected muscles deteriorate through muscle fiber atrophy and transformation. The implicated process may involve alterations in sarcolemmal sites of myofibril attachment (costameres), which control myofibrillogenesis via a mechano-regulated mechanism through integrin-associated focal adhesion kinase (FAK). We assessed the contribution of FAK to alterations in fiber type composition and expression of costamere-associated structural proteins, the phosphorylation status of Y397-FAK and downstream mTOR/JNK-P70S6K hypertrophy signaling in rat soleus muscle after Achilles tenotomy and tendon repair. Achilles tenotomy induced a profound deterioration of muscle composition 14 days, but not 4 days, following tendon release, comprising specifically increased area percentages of fast type fibers, fibers with internal nuclei, and connective tissue. Concomitantly, expression of costameric proteins FAK and meta-vinculin, and phosphorylation of T421/S424-P70S6K and T183/Y185-JNK was elevated, all of which was mitigated by tendon reattachment immediately after release. Overexpression of FAK in soleus muscle fibers and reattachment corrected the expression of meta- and gamma-vinculin isoforms to the lower levels in mock controls while further enhancing T183/Y185-JNK phosphorylation and levels of FAK C-terminus-related inhibitory proteins. Co-overexpression of the FAK inhibitor, FRNK, lowered FAK-overexpression driven Y397-FAK phosphorylation and T183/Y185-JNK phosphorylation. FAK levels correlated to molecular and cellular hallmarks of fiber degeneration. The findings demarcate the window between 4 and 14 days after tenotomy as costamere-dependent muscle transformation process, and expose that FAK overexpression prevents molecular aspects of the pathology which within the study limitations does not result in the mitigation of muscle fiber degeneration.250 words.

Protective effect of focal adhesion kinase against skeletal muscle reperfusion injury after acute limb ischemia

OBJECTIVES

In cardiac muscle, ischemia reperfusion (IR) injury is attenuated by mitochondrial function, which may be upregulated by focal adhesion kinase (FAK). The aim of this study was to determine whether increased FAK levels reduced rhabdomyolysis in skeletal muscle too.

MATERIAL AND METHODS

In a translational in vivo experiment, rat lower limbs were subjected to 4 hours of ischemia followed by 24 or 72 hours of reperfusion. FAK expression was stimulated 7 days before (via somatic transfection with pCMV-driven FAK expression plasmid) and outcomes were measured against non-transfected and empty transfected controls. Slow oxidative (i.e., mitochondria-rich) and fast glycolytic (i.e., mitochondria-poor) type muscles were analyzed separately regarding rhabdomyolysis, apoptosis, and inflammation. Severity of IR injury was assessed using paired non-ischemic controls.

RESULTS

After 24 hours of reperfusion, marked rhabdomyolysis was found in non-transfected and empty plasmid-transfected fast-type glycolytic muscle, tibialis anterior. Prior transfection enhanced FAK concentration significantly (p = 0.01). Concomitantly, levels of BAX, promoting mitochondrial transition pores, were reduced sixfold (p = 0.02) together with a blunted inflammation (p = 0.01) and reduced rhabdomyolysis (p = 0.003). Slow oxidative muscle, m. soleus, reacted differently: although apoptosis was detectable after IR, rhabdomyolysis did not appear before 72 hours of reperfusion; and FAK levels were not enhanced in ischemic muscle despite transfection (p = 0.66).

CONCLUSIONS

IR-induced skeletal muscle rhabdomyolysis is a fiber type-specific phenomenon that appears to be modulated by mitochondria reserves. Stimulation of FAK may exploit these reserves constituting a potential therapeutic approach to reduce tissue loss following acute limb IR in fast-type muscle.

In vivo electroporation-mediated gene delivery to the beating heart

Gene therapy may represent a promising alternative strategy for cardiac muscle regeneration. In vivo electroporation, a physical method of gene transfer, has recently evolved as an efficient method for gene transfer. Here, we describe two protocols involving in vivo electroporation for gene transfer to the beating heart.

PhiC31 integrase-mediated genomic integration and stable gene expression in the mouse mammary gland after gene electrotransfer

BACKGROUND

PhiC31 integrase is capable of conferring long-term transgene expression in various transfected tissues in vivo. In the present study, we investigated the activity of phiC31 integrase in mouse mammary glands.

METHODS

The normal mouse mammary epithelial cell line HC11 was transfected with FuGENE® HD Transfection Reagent (Roche Diagnostics, Shanghai, China). Transfection of the mouse mammary gland in vivo was performed by electrotransfer. Transgene expression was detected by western blotting and an enzyme-linked immunosorbent assay. Genomic integration and integration at mpsL1 was confirmed by a nested polymerase chain reaction.

RESULTS

An optimal electrotransfer protocol for the lactating mouse mammary gland was attained through investigation of different voltages and pulse durations. PhiC31 integrase mediated site-specific transgene integration in HC11 cells and the mouse mammary gland. In addition, the site-specific integration occurred efficiently at the ‘hot spot’ mpsL1. Co-delivery of PhiC31 integrase enhanced and prolonged transgene expression in the mouse mammary gland.

CONCLUSIONS

The results obtained in the present study show that the use of phiC31 integrase is a feasible and efficient method for high and stable transgene expression in the mouse mammary gland.

Myocardial gene transfer: routes and devices for regulation of transgene expression by modulation of cellular permeability

Heart diseases are major causes of morbidity and mortality in Western society. Gene therapy approaches are becoming promising therapeutic modalities to improve underlying molecular processes affecting failing cardiomyocytes. Numerous cardiac clinical gene therapy trials have yet to demonstrate strong positive results and advantages over current pharmacotherapy. The success of gene therapy depends largely on the creation of a reliable and efficient delivery method. The establishment of such a system is determined by its ability to overcome the existing biological barriers, including cellular uptake and intracellular trafficking as well as modulation of cellular permeability. In this article, we describe a variety of physical and mechanical methods, based on the transient disruption of the cell membrane, which are applied in nonviral gene transfer. In addition, we focus on the use of different physiological techniques and devices and pharmacological agents to enhance endothelial permeability. Development of these methods will undoubtedly help solve major problems facing gene therapy.