M-cadherin-mediated intercellular interactions activate satellite cell division.

Adult muscle stem cells and their committed myogenic precursors, commonly referred to as the satellite cell population, are involved in both muscle growth after birth and regeneration after damage. It has been previously proposed that, under these circumstances, satellite cells first become activated, divide and differentiate, and only later fuse to the existing myofiber through M-cadherin-mediated intercellular interactions. Our data show that satellite cells fuse with the myofiber concomitantly to cell division, and only when the nuclei of the daughter cells are inside the myofiber, do they complete the process of differentiation. Here we demonstrate that M-cadherin plays an important role in cell-to-cell recognition and fusion, and is crucial for cell division activation. Treatment of satellite cells with M-cadherin in vitro stimulates cell division, whereas addition of anti-M-cadherin antibodies reduces the cell division rate. Our results suggest an alternative model for the contribution of satellite cells to muscle development, which might be useful in understanding muscle regeneration, as well as muscle-related dystrophies.

The local microenvironment limits the regenerative potential of the mouse neonatal heart.

Neonatal mice have been shown to regenerate their hearts during a transient window of time of approximately 1 week after birth. However, experimental evidence for this phenomenon is not undisputed, because several laboratories have been unable to detect neonatal heart regeneration. We first confirmed that 1-day-old neonatal mice are indeed able to mount a robust regenerative response after heart amputation. We then found that this regenerative ability sharply declines within 48 hours, with hearts of 2-day-old mice responding to amputation with fibrosis, rather than regeneration. By comparing the global transcriptomes of 1- and 2-day-old mouse hearts, we found that most differentially expressed transcripts encode extracellular matrix components and structural constituents of the cytoskeleton. These results suggest that the stiffness of the local microenvironment, rather than cardiac cell-autonomous mechanisms, crucially determines the ability or inability of the heart to regenerate. Testing this hypothesis by pharmacologically decreasing the stiffness of the extracellular matrix in 3-day-old mice, we found that decreased matrix stiffness rescued the ability of mice to regenerate heart tissue after apical resection. Together, our results identify an unexpectedly restricted time window of regenerative competence in the mouse neonatal heart and open new avenues for promoting cardiac regeneration by local modification of the extracellular matrix stiffness.

[Predictive factors related to success of non invasive ventilation and mortality in the treatment of acute cardiogenic pulmonary edema]. / Factores de predicción del éxito de la ventilación no invasiva en el tratamiento del edema agudo de pulmón cardiogénico.

BACKGROUND AND OBJECTIVE: Recent studies support the use of non invasive ventilation (NIV) in patients with acute cardiogenic pulmonary edema (ACPE). We aimed to evaluate the factors related to the success of the technique in patients admitted to an intensive care unit (ICU) with ACPE. PATIENTS AND METHOD: An observational prospective study was performed in ICU.199 consecutive patients were enrolled with ACPE at admission who received treatment with NIV and standardized pharmacological treatment. The success of the NIV was achieved when endotracheal intubation was avoided and patients were alive without dyspnea within and 24 hours after discharge from the ICU. Clinical, physiological and gasometric parameters were analyzed at admission and one hour after starting NIV. RESULTS: Patient's age was 74 years. 43% were male. The SAPS II was 45. 74.4% of the patients were successfully treated with NIV. 12.6% required endotracheal intubation. In a multivariate analysis, the success of the technique (values expressed as odds ratio [95% confidence interval]) was related to: SAPS II (0.95 [0.91-0.99]); the place of admission (6.78 [1.85-24.79]); value of PCO2 at admission (1.05 [1.01-1.09]); PO2/FiO2 index (1.03 [1.01-1.06]) and respiratory frequency (0.91 [0.84-0.99]) within the first hour; SOFA (acute failure organics score) (0.62 [0.49-0.78]); concomittant acute myocardial infarction (AMI) (0.05 [0.01-0.22]) and number of complications (0.17 [0.47-0.65]). The hospital mortality rate was 32.7%. The non intubation order (0.12 [0.04-0.32]) and the success of the technique (100.03 [28.71-348.47]) were related to the hospital mortality. CONCLUSIONS: The success of NIV in the treatment of ACPE is related to a lower SAPS II, admission at the emergency department, elevated PCO2 at admission, improvement of the PO2/FiO2 index and the respiratory rate within the first hour. The non intubation order and the success of the technique were related to the hospital mortality.

Characterization of pluripotent stem cells.

Characterization of pluripotent stem cells is required for the registration of stem cell lines and allows for an impartial and objective comparison of the results obtained when generating multiple lines. It is therefore crucial to establish specific, fast and reliable protocols to detect the hallmarks of pluripotency. Such protocols should include immunocytochemistry (takes 2 d), identification of the three germ layers in in vitro-derived embryoid bodies by immunocytochemistry (immunodetection takes 3 d) and detection of differentiation markers in in vivo-generated teratomas by immunohistochemistry (differentiation marker detection takes 4 d). Standardization of the immunodetection protocols used ensures minimum variations owing to the source, the animal species, the endogenous fluorescence or the inability to collect large amounts of cells, thereby yielding results as fast as possible without loss of quality. This protocol provides a description of all the immunodetection procedures necessary to characterize mouse and human stem cell lines in different circumstances.