Mitochondrial Dysfunction as an Underlying Cause of Skeletal Muscle Disorders.

Mitochondria are an important energy source in skeletal muscle. A main function of mitochondria is the generation of ATP for energy through oxidative phosphorylation (OXPHOS). Mitochondrial defects or abnormalities can lead to muscle disease or multisystem disease. Mitochondrial dysfunction can be caused by defective mitochondrial OXPHOS, mtDNA mutations, Ca2+ imbalances, mitochondrial-related proteins, mitochondrial chaperone proteins, and ultrastructural defects. In addition, an imbalance between mitochondrial fusion and fission, lysosomal dysfunction due to insufficient biosynthesis, and/or defects in mitophagy can result in mitochondrial damage. In this review, we explore the association between impaired mitochondrial function and skeletal muscle disorders. Furthermore, we emphasize the need for more research to determine the specific clinical benefits of mitochondrial therapy in the treatment of skeletal muscle disorders.

Identification of distinct slow mode of reversible adaptation of pancreatic ductal adenocarcinoma to the prolonged acidic pH microenvironment.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic neoplasm with high metastatic potential and poor clinical outcome. Like other solid tumors, PDAC in the early stages is often asymptomatic, and grows very slowly under a distinct acidic pHe (extracellular pH) microenvironment. However, most previous studies have only reported the fate of cancerous cells upon cursory exposure to acidic pHe conditions. Little is known about how solid tumors-such as the lethal PDAC originating within the pancreatic duct-acinar system that secretes alkaline fluids-evolve to withstand and adapt to the prolonged acidotic microenvironmental stress. METHODS: Representative PDAC cells were exposed to various biologically relevant periods of extracellular acidity. The time effects of acidic pHe stress were determined with respect to tumor cell proliferation, phenotypic regulation, autophagic control, metabolic plasticity, mitochondrial network dynamics, and metastatic potentials. RESULTS: Unlike previous short-term analyses, we found that the acidosis-mediated autophagy occurred mainly as an early stress response but not for later adaptation to microenvironmental acidification. Rather, PDAC cells use a distinct and lengthy process of reversible adaptive plasticity centered on the early fast and later slow mitochondrial network dynamics and metabolic adjustment. This regulates their acute responses and chronic adaptations to the acidic pHe microenvironment. A more malignant state with increased migratory and invasive potentials in long-term acidosis-adapted PDAC cells was obtained with key regulatory molecules being closely related to overall patient survival. Finally, the identification of 34 acidic pHe-related genes could be potential targets for the development of diagnosis and treatment against PDAC. CONCLUSIONS: Our study offers a novel mechanism of early rapid response and late reversible adaptation of PDAC cells to the stress of extracellular acidosis. The presence of this distinctive yet slow mode of machinery fills an important knowledge gap in how solid tumor cells sense, respond, reprogram, and ultimately adapt to the persistent microenvironmental acidification.

Conditioned Media of Adipose-Derived Stem Cells Suppresses Sidestream Cigarette Smoke Extract Induced Cell Death and Epithelial-Mesenchymal Transition in Lung Epithelial Cells.

The role of the epithelial-mesenchymal transition (EMT) in lung epithelial cells is increasingly being recognized as a key stage in the development of COPD, fibrosis, and lung cancers, which are all highly associated with cigarette smoking and with exposure to second-hand smoke. Using the exposure of human lung cancer epithelial A549 cells and non-cancerous Beas-2B cells to sidestream cigarette smoke extract (CSE) as a model, we studied the protective effects of adipose-derived stem cell-conditioned medium (ADSC-CM) against CSE-induced cell death and EMT. CSE dose-dependently induced cell death, decreased epithelial markers, and increased the expression of mesenchymal markers. Upstream regulator analysis of differentially expressed genes after CSE exposure revealed similar pathways as those observed in typical EMT induced by TGF-ß1. CSE-induced cell death was clearly attenuated by ADSC-CM but not by other control media, such as a pass-through fraction of ADSC-CM or A549-CM. ADSC-CM effectively inhibited CSE-induced EMT and was able to reverse the gradual loss of epithelial marker expression associated with TGF-ß1 treatment. CSE or TGF-ß1 enhanced the speed of A549 migration by 2- to 3-fold, and ADSC-CM was effective in blocking the cell migration induced by either agent. Future work will build on the results of this in vitro study by defining the molecular mechanisms through which ADSC-CM protects lung epithelial cells from EMT induced by toxicants in second-hand smoke.

Assessment of Polyethylene Glycol-Coated Gold Nanoparticle Toxicity and Inflammation In Vivo Using NF-κB Reporter Mice.

Polyethylene glycol (PEG) coating of gold nanoparticles (AuNPs) improves AuNP distribution via blood circulation. The use of PEG-coated AuNPs was shown to result in acute injuries to the liver, kidney, and spleen, but long-term toxicity has not been well studied. In this study, we investigated reporter induction for up to 90 days in NF-κB transgenic reporter mice following intravenous injection of PEG-coated AuNPs. The results of different doses (1 and 4 µg AuNPs per gram of body weight), particle sizes (13 nm and 30 nm), and PEG surfaces (methoxyl- or carboxymethyl-PEG 5 kDa) were compared. The data showed up to 7-fold NF-κB reporter induction in mouse liver from 3 h to 7 d post PEG-AuNP injection compared to saline-injected control mice, and gradual reduction to a level similar to control by 90 days. Agglomerates of PEG-AuNPs were detected in liver Kupffer cells, but neither gross pathological abnormality in liver sections nor increased activity of liver enzymes were found at 90 days. Injection of PEG-AuNPs led to an increase in collagen in liver sections and elevated total serum cholesterol, although still within the normal range, suggesting that inflammation resulted in mild fibrosis and affected hepatic function. Administrating PEG-AuNPs inevitably results in nanoparticles entrapped in the liver; thus, further investigation is required to fully assess the long-term impacts by PEG-AuNPs on liver health.

Enhancement of Neurite Outgrowth by Warming Biomaterial Ultrasound Treatment.

Ultrasound is a method for enhancing neurite outgrowth because of its thermal effect. In order to reach the working temperature to enhance neurite outgrowth, long-time treatment by ultrasound is necessary, while acknowledging that the treatment poses a high risk of damaging nerve cells. To overcome this problem, we developed a method that shortens the ultrasonic treatment time with a warming biomaterial. In this study, we used Fe3O4 nanoparticle-embedded polycaprolactone (PCL) as a sonosensitized biomaterial, which has an excellent heating rate due to its high acoustic attenuation. With this material, the ultrasonic treatment time for enhancing neurite outgrowth could be effectively shortened. Ultrasonic treatment could also increase neuronal function combined with the warming biomaterial, with more promoter neuronal function than only ultrasound. Moreover, the risk of overexposure can be avoided by the use of the warming biomaterial by reducing the ultrasonic treatment time, providing better effectiveness.

Cardiac fibrosis in mouse expressing DsRed tetramers involves chronic autophagy and proteasome degradation insufficiency.

Proteinopathy in the heart which often manifests excessive misfolded/aggregated proteins in cardiac myocytes can result in severe fibrosis and heart failure. Here we developed a mouse model, which transgenically express tetrameric DsRed, a red fluorescent protein (RFP), in an attempt to mimic the pathological mechanisms ofcardiac fibrosis. Whilst DsRed is expressed and forms aggregation in most mouse organs, certain pathological defects are specifically recapitulated in cardiac muscle cells including mitochondria damages, aggresome-like residual bodies, excessive ubiquitinated proteins, and the induction of autophagy. The proteinopathy and cellular injuries caused by DsRed aggregates may be due to impaired or overburdened ubiquitin-proteasome system and autophagy-lysosome systems. We further identified that DsRed can be ubiquitinated and associated with MuRF1, a muscle-specific E3 ligase. Concomitantly, an activation of NF-κB signaling and a strong TIMP1 induction were noted, suggesting that RFP-induced fibrosis was augmented by a skewed balance between TIMP1 and MMPs. Taken together, our study highlights the molecular consequences of uncontrolled protein aggregation leading to congestive heart failure, and provides novel insights into fibrosis formation that can be exploited for improved therapy.

Neonatal Death and Heart Failure in Mouse with Transgenic HSP60 Expression.

Mitochondrial heat shock proteins, such as HSP60, are chaperones responsible for the folding, transport, and quality control of mitochondrial matrix proteins and are essential for maintaining life. Both prosurvival and proapoptotic roles have been proposed for HSP60, and HSP60 is reportedly involved in the initiation of autoimmune, metabolic, and cardiovascular diseases. The role of HSP60 in pathogenesis of these diseases remains unclear, partly because of the lack of mouse models expressing HSP60. In this study we generated HSP60 conditional transgenic mice suitable for investigating in vivo outcomes by expressing HSP60 at the targeted organ in disease models. Ubiquitous HSP60 induction in the embryonic stage caused neonatal death in mice at postnatal day 1. A high incidence of atrial septal defects was observed in HSP60-expressing mice, with increased apoptosis and myocyte degeneration that possibly contributed to massive hemorrhage and sponge-like cardiac muscles. Our results showed that neonatal heart failure through HSP60 induction likely involves developmental defects and excessive apoptosis. The conditional HSP60 mouse model is useful for studying crucial biological questions concerning HSP60.

Notch signaling prevents mucous metaplasia in mouse conducting airways during postnatal development.

Goblet cell metaplasia and mucus overproduction contribute to the pathogenesis of chronic lung diseases, including asthma and chronic obstructive pulmonary disease (COPD). Notch signaling regulates cell fate decisions and is crucial in controlling goblet cell differentiation in the gut epithelium. Little is known, however, about how endogenous Notch signaling influences the goblet cell differentiation program that takes place in the postnatal lung. Using a combination of genetic and in vitro approaches here we provide evidence of a novel role for Notch in restricting goblet cell differentiation in the airway epithelium during the postnatal period. Conditional inactivation of the essential Notch pathway component Pofut1 (protein O-fucosyltransferase1) in Tgfb3-Cre-expressing mice resulted in an aberrant postnatal airway phenotype characterized by marked goblet cell metaplasia, decreased Clara cell number and increase in ciliated cells. The presence of the same phenotype in mice in which the Notch transcriptional effector Rbpjk was deleted indicated the involvement of the canonical Notch pathway. Lineage study in vivo suggested that goblet cells originated from a subpopulation of Clara cells largely present in proximal airways in which Notch was disrupted. The phenotype was confirmed by a panel of goblet cell markers, showed no changes in cell proliferation or altered expression of proinflammatory cytokines and was associated with significant downregulation of the bHLH transcriptional repressor Hes5. Luciferase reporter analysis suggested that Notch directly repressed MUC5AC transcription in lung epithelial cells. The data suggested that during postnatal life Notch is required to prevent Clara cells from differentiating into goblet cells.

A single-monomer derived linear-like PEI-co-PEG for siRNA delivery and silencing.

Polyethylenimines (PEIs) are commonly used as a vehicle to deliver and protect siRNA, but the strong interaction still remains to be modulated for efficient siRNA release and silencing. Herein, a single-monomer derived linear-like PEI-co-PEG (LPEI-co-PEG, P(2)) was synthesized to substantially enhance the siRNA release, but not affect the efficiency of protection. The linear-like copolymer (P(2)) was only synthesized from a single-monomer by intensive synchrotron X-ray irradiation within 5 min, randomly producing both PEI and PEG segments. The counterpart vehicle, LPEI (P(1)), was also synthesized for comparison. We found that the P(1) and P(2) were able to prevent siRNA against enzymatic degradation. Most importantly, efficient siRNA release (52%) was only observed in the siRNA/P(2) complexes and not in the siRNA/P(1) complexes (<5%), suggesting that the PEG segment may modulate the interaction between siRNA and P(2) segment. Specifically, P(2) as well as P(1) can emit photoluminescence; cancer cells exhibited a detectable photoluminescence after treatment with P(1) and P(2), indicative of their excellent transfection efficiency. Subsequently, the siGFP/P(2) complexes knocked down GFP with excellent efficiency (75%) above the siGFP/P(1) complexes (19%) and siGFP/Lipofectamine complexes (20%). Importantly, the siRNA with anti-VEGF function being associated with P(2) have been demonstrated an excellent efficiency in the suppression of tumor growth.

Notch signaling regulates late-stage epidermal differentiation and maintains postnatal hair cycle homeostasis.

BACKGROUND: Notch signaling involves ligand-receptor interactions through direct cell-cell contact. Multiple Notch receptors and ligands are expressed in the epidermis and hair follicles during embryonic development and the adult stage. Although Notch signaling plays an important role in regulating differentiation of the epidermis and hair follicles, it remains unclear how Notch signaling participates in late-stage epidermal differentiation and postnatal hair cycle homeostasis. METHODOLOGY AND PRINCIPAL FINDINGS: We applied Cre/loxP system to generate conditional gene targeted mice that allow inactivation of critical components of Notch signaling pathway in the skin. Rbpj, the core component of all four Notch receptors, and Pofut1, an essential factor for ligand-receptor interactions, were inactivated in hair follicle lineages and suprabasal layer of the epidermis using the Tgfb3-Cre mouse line. Rbpj conditional inactivation resulted in granular parakeratosis and reactive epidermal hyperplasia. Pofut1 conditional inactivation led to ultrastructural abnormalities in the granular layer and altered filaggrin processing in the epidermis, suggesting a perturbation of the granular layer differentiation. Disruption of Pofut1 in hair follicle lineages resulted in aberrant telogen morphology, a decrease of bulge stem cell markers, and a concomitant increase of K14-positive keratinocytes in the isthmus of mutant hair follicles. Pofut1-deficent hair follicles displayed a delay in anagen re-entry and dysregulation of proliferation and apoptosis during the hair cycle transition. Moreover, increased DNA double stand breaks were detected in Pofut1-deficent hair follicles, and real time PCR analyses on bulge keratinocytes isolated by FACS revealed an induction of DNA damage response and a paucity of DNA repair machinery in mutant bulge keratinocytes. SIGNIFICANCE: our data reveal a role for Notch signaling in regulating late-stage epidermal differentiation. Notch signaling is required for postnatal hair cycle homeostasis by maintaining proper proliferation and differentiation of hair follicle stem cells.

Mechanical stretching induces osteoprotegerin in differentiating C2C12 precursor cells through noncanonical Wnt pathways.

Mechanical loading is known to be important for maintaining the formation and resorption rates of bone. To study the mechanisms by which mechanical loading regulates osteogenesis, we investigated the role of the Wnt pathway in C2C12 cells committed to osteogenic differentiation in response to cyclic mechanical stretching. Osteoprotegerin (OPG) acts as a decoy receptor for RANKL to inhibit osteoclastogenesis and resorption of bone. Our results demonstrate that stretching leads to a sustained increase in OPG expression in C2C12 cells. The expression of osteogenic marker genes, such as osteocalcin and alkaline phosphatase, was transiently decreased by stretching at 24 hours and returned to control levels at 48 hours. The addition of inhibitors of the canonical Wnt/beta-catenin pathways, such as the secreted FZD-related peptide sRFP2, as well as siRNA-mediated knockdown, did not inhibit the effect of stretching on OPG expression. In contrast, treatment with inhibitors of noncanonical Wnt signaling, including KN93, and siRNA for Nemo-like kinase (NLK) blocked most of the mechanical inductive effect on OPG. Furthermore, stretching-induced OPG production in the culture medium was able to inhibit the osteoclast formation of bone marrow macrophages. These results suggest that mechanical stretching may play an important role in bone remodeling through the upregulation of OPG and that the mechanical signaling leading to OPG induction involves the noncanonical Wnt pathway.

Detection of experimentally induced pulmonary granuloma inflammation in monocyte chemoattractant protein-1 reporter mice.

PURPOSE: Among different chemokines, monocyte chemoattractant protein-1 (MCP-1) plays an important role in inflammatory disorders of lung. In response to stimuli, MCP-1 increases its transcription as an immediate early gene. In this paper, we describe the MCP-1-enhanced green fluorescent protein(EGFP) transgenic mouse in which EGFP expression is driven by human MCP-1 promoter and mimics the MCP-1 expression in situ. Thus, the MCP-1 reporter mouse model is designed to facilitate a better understanding of its role in various diseases. We employed this mouse model in a pulmonary granulomatous inflammation model using intratracheal instillation of Sephadex (SDX) beads and compared the EGFP reporter expression to endogenous MCP-1 expression through the course of inflammation. PROCEDURES: We analyzed the temporal pattern of SDX-induced infiltration of inflammatory cells in lung and in bronchoalveolar lavage fluid (BALF). The changes in tissue fluorescence, gene, and protein expressions for both MCP-1 and EGFP were analyzed. RESULTS: SDX instillation caused massive infiltration of inflammatory cells in BALF and lung tissue at the end of day 3. There was an increase of fluorescence in SDX-treated lung and BALF cells. By using lipopolysaccharide-induced systemic inflammation model, increase of fluorescence was found in bone marrow Gr-1(+) cells with high Mac-1 expression. MCP-1 and EGFP gene expression and MCP-1 protein level were increased after day 1, peaked at day 3, and declined toward basal levels at day 5. In contrast, EGFP protein level peaked after day 3 and remained elevated after day 5. Immunohistochemical staining revealed the MCP-1 and EGFP expression primarily at alveolar macrophages, macrophages infiltrating the granulomatous lesions and in bronchiolar epithelial cells. CONCLUSIONS: By using a pulmonary granuloma model, we showed that EGFP transgene reporter expression in MCP-1-EGFP mouse was correlated to the endogenous MCP-1 induction. The establishment of this mouse model will provide a valuable tool for monitoring the activation of monocytes/macrophages and facilitate the studies on the roles of MCP-1 gene in various inflammatory diseases.

Angiogenic evaluation of ginsenoside Rg 1 from Panax ginseng in fluorescent transgenic mice.

BACKGROUND: Evaluation of angiogenesis-inducing compounds is essential in tissue engineering to develop biological substitutes for the repair or regeneration of tissue function. In this report, we evaluated the angiogenic ability of ginsenoside Rg 1 from Panax ginseng, in Matrigel implanted on fluorescent transgenic mice. METHODS: The in vitro proliferation ability of each test agent was estimated by MTS assay. The Matrigel loaded with basic fibroblast growth factor (bFGF) or Rg 1 and Matrigel alone were implanted on fluorescent transgenic mice and were retrieved at 1, 4, 6 and 8 weeks after implantation to measure various conventional markers for angiogenesis including neo-vascular density and hemoglobin content. Additionally, the functional neo-vasculature in the implanted Matrigel was visualized using confocal laser scanning microscopy (CLSM). RESULTS: The in vitro results indicated that the stimulating effect of Rg 1 on HUVECs proliferation remained unchanged after dissolved for 30 days in culture medium at 37 degrees C when compared with the effect of bFGF. One week after implantation in transgenic mice, bFGF or Rg 1 mixed in Matrigel plug significantly enhanced angiogenesis; however, at 6 weeks a significant decrease in angiogenic effect was observed in Matrigel with bFGF, but not in Matrigel with Rg 1. The neo-vessels structure was visualized in three dimensions (3D) by CLSM and the results were in agreement with other conventional measurements for angiogenesis. CONCLUSION: These findings confirm that Rg 1 could be used in tissue tissue-engineering applications and that the fluorescent transgenic mice can be a useful experimental model for studying angiogenesis.