Treatment of necrotizing enterocolitis by conditioned medium derived from human amniotic fluid stem cells.

PURPOSE: Necrotizing enterocolitis (NEC) is one of the most distressing gastrointestinal emergencies affecting neonates. Amniotic fluid stem cells (AFSC) improve intestinal injury and survival in experimental NEC but are difficult to administer. In this study, we evaluated whether conditioned medium (CM) derived from human AFSC have protective effects. METHODS: Three groups of C57BL/6 mice were studied: (i) breast-fed mice as control; (ii) experimental NEC mice receiving PBS; and (iii) experimental NEC mice receiving CM. NEC was induced between post-natal days P5 through P9 via: (A) gavage feeding of hyperosmolar formula four-time a day; (B) 10 minutes hypoxia prior to feeds; and (C) lipopolysaccharide administration on P6 and P7. Intra-peritoneal injections of either PBS or CM were given on P6 and P7. All mice were sacrificed on P9 and terminal ileum were harvested for analyses. RESULTS: CM treatment increased survival and reduced intestinal damage, decreased mucosal inflammation (IL-6; TNF-α), neutrophil infiltration (MPO), and apoptosis (CC3), and also restored angiogenesis (VEGF) in the ileum. Additionally, CM treated mice had increased levels of epithelial proliferation (Ki67) and stem cell activity (Olfm4; Lgr5) compared to NEC+PBS mice, showing restored intestinal regeneration and recovery during NEC induction. CM proteomic analysis of CM content identified peptides that regulated immune and stem cell activity. CONCLUSIONS: CM derived from human AFSC administered in experimental NEC exhibited various benefits including reduced intestinal injury and inflammation, increased enterocyte proliferation, and restored intestinal stem cell activity. This study provides the scientific basis for the use of CM derived from AFSC in neonates with NEC.

Secretome of adipose-derived mesenchymal stem cells promotes skeletal muscle regeneration through synergistic action of extracellular vesicle cargo and soluble proteins.

BACKGROUND: The mechanisms underpinning the regenerative capabilities of mesenchymal stem cells (MSC) were originally thought to reside in their ability to recognise damaged tissue and to differentiate into specific cell types that would replace defective cells. However, recent work has shown that molecules produced by MSCs (secretome), particularly those packaged in extracellular vesicles (EVs), rather than the cells themselves are responsible for tissue repair. METHODS: Here we have produced a secretome from adipose-derived mesenchymal stem cells (ADSC) that is free of exogenous molecules by incubation within a saline solution. Various in vitro models were used to evaluate the effects of the secretome on cellular processes that promote tissue regeneration. A cardiotoxin-induced skeletal muscle injury model was used to test the regenerative effects of the whole secretome or isolated extracellular vesicle fraction in vivo. This was followed by bioinformatic analysis of the components of the protein and miRNA content of the secretome and finally compared to a secretome generated from a secondary stem cell source. RESULTS: Here we have demonstrated that the secretome from adipose-derived mesenchymal stem cells shows robust effects on cellular processes that promote tissue regeneration. Furthermore, we show that the whole ADSC secretome is capable of enhancing the rate of skeletal muscle regeneration following acute damage. We assessed the efficacy of the total secretome compared with the extracellular vesicle fraction on a number of assays that inform on tissue regeneration and demonstrate that both fractions affect different aspects of the process in vitro and in vivo. Our in vitro, in vivo, and bioinformatic results show that factors that promote regeneration are distributed both within extracellular vesicles and the soluble fraction of the secretome. CONCLUSIONS: Taken together, our study implies that extracellular vesicles and soluble molecules within ADSC secretome act in a synergistic manner to promote muscle generation.

Protein and Molecular Characterization of a Clinically Compliant Amniotic Fluid Stem Cell-Derived Extracellular Vesicle Fraction Capable of Accelerating Muscle Regeneration Through Enhancement of Angiogenesis.

The secretome of human amniotic fluid stem cells (AFSCs) has great potential as a therapeutic agent in regenerative medicine. However, it must be produced in a clinically compliant manner before it can be used in humans. In this study, we developed a means of producing a biologically active secretome from AFSCs that is free of all exogenous molecules. We demonstrate that the full secretome is capable of promoting stem cell proliferation, migration, and protection of cells against senescence. Furthermore, it has significant anti-inflammatory properties. Most importantly, we show that it promotes tissue regeneration in a model of muscle damage. We then demonstrate that the secretome contains extracellular vesicles (EVs) that harbor much, but not all, of the biological activity of the whole secretome. Proteomic characterization of the EV and free secretome fraction shows the presence of numerous molecules specific to each fraction that could be key regulators of tissue regeneration. Intriguingly, we show that the EVs only contain miRNA and not mRNA. This suggests that tissue regeneration in the host is mediated by the action of EVs modifying existing, rather than imposing new, signaling pathways. The EVs harbor significant anti-inflammatory activity as well as promote angiogenesis, the latter may be the mechanistic explanation for their ability to promote muscle regeneration after cardiotoxin injury.

Symmorphosis through dietary regulation: a combinatorial role for proteolysis, autophagy and protein synthesis in normalising muscle metabolism and function of hypertrophic mice after acute starvation.

Animals are imbued with adaptive mechanisms spanning from the tissue/organ to the cellular scale which insure that processes of homeostasis are preserved in the landscape of size change. However we and others have postulated that the degree of adaptation is limited and that once outside the normal levels of size fluctuations, cells and tissues function in an aberant manner. In this study we examine the function of muscle in the myostatin null mouse which is an excellent model for hypertrophy beyond levels of normal growth and consequeces of acute starvation to restore mass. We show that muscle growth is sustained through protein synthesis driven by Serum/Glucocorticoid Kinase 1 (SGK1) rather than Akt1. Furthermore our metabonomic profiling of hypertrophic muscle shows that carbon from nutrient sources is being channelled for the production of biomass rather than ATP production. However the muscle displays elevated levels of autophagy and decreased levels of muscle tension. We demonstrate the myostatin null muscle is acutely sensitive to changes in diet and activates both the proteolytic and autophagy programmes and shutting down protein synthesis more extensively than is the case for wild-types. Poignantly we show that acute starvation which is detrimental to wild-type animals is beneficial in terms of metabolism and muscle function in the myostatin null mice by normalising tension production.

Do intraoperative variables have an effect on the timing of tracheal extubation after coronary artery bypass graft surgery?

OBJECTIVE: The purpose of this study was to investigate whether any intraoperative variable had a significant effect on extubation time after coronary artery bypass graft surgery. DESIGN: Study design was a retrospective study. SETTING: Study took place in 1 cardiac center in the United Kingdom that had 1000 cases per year. SUBJECTS: Eighty-nine patients had coronary artery bypass graft surgery in the first 6 months of 1998 performed by one consultant cardiac surgeon. OUTCOME MEASURES: Study measures included intraoperative variables (number of vessels grafted, time on cardiopulmonary bypass [CPB], length of the operation, use of internal mammary artery) and extubation time. RESULTS: Mean extubation time was 4.97 hours. On analysis via linear regression no intraoperative variables were found to be statistically significant (P = .05) to extubation time. CONCLUSION: This study identified that early extubation can be achieved safely. Although no variable was found to have a significant effect on extubation time, the relationship between CPB and extubation may have been attributed to the low mean CPB time within the study (49.1 minutes). The relationship between cardiac status, ischemia, and the timing of extubation does warrant additional exploration.

Propeptide-mediated inhibition of myostatin increases muscle mass through inhibiting proteolytic pathways in aged mice.

Mammalian aging is accompanied by a progressive loss of skeletal muscle, a process called sarcopenia. Myostatin, a secreted member of the transforming growth factor-ß family of signaling molecules, has been shown to be a potent inhibitor of muscle growth. Here, we examined whether muscle growth could be promoted in aged animals by antagonizing the activity of myostatin through the neutralizing activity of the myostatin propeptide. We show that a single injection of an AAV8 virus expressing the myostatin propeptide induced an increase in whole body weights and all muscles examined within 7 weeks of treatment. Our cellular studies demonstrate that muscle enlargement was due to selective fiber type hypertrophy, which was accompanied by a shift toward a glycolytic phenotype. Our molecular investigations elucidate the mechanism underpinning muscle hypertrophy by showing a decrease in the expression of key genes that control ubiquitin-mediated protein breakdown. Most importantly, we show that the hypertrophic muscle that develops as a consequence of myostatin propeptide in aged mice has normal contractile properties. We suggest that attenuating myostatin signaling could be a very attractive strategy to halt and possibly reverse age-related muscle loss.

Efficient myogenic reprogramming of adult white fat stem cells and bone marrow stem cells by freshly isolated skeletal muscle fibers.

Stem cells that can be directed to differentiate into specific cell types offer the prospect of a renewable source of replacement cells to treat diseases. This study evaluates the reprogramming of 2 readily available stem cell populations into skeletal muscle. We show for the first time that freshly isolated muscle fibers reprogram bone marrow or white fat stem cells far more efficiently than muscle cell lines. In addition, we show that the ability of muscle fibers to reprogram stem cells can be almost doubled through the use of chromatin remodeling reagents such as trichostatin A. This novel approach permits the generation of myogenic cells that could be used to treat a range of muscle-wasting diseases.