Premature Aging of Stem Cell Telomeres, Not Inflammation, Linked to Emphysema

Source: John Hopkins Medicine

(BALTIMORE, Maryland) – Lung diseases like emphysema and pulmonary fibrosis are common among people with malfunctioning telomeres, the “caps” or ends of chromosomes. Now, researchers from Johns Hopkins say they have discovered what goes wrong and why.

Mary Armanios, MD, an associate professor of oncology at the Johns Hopkins University School of Medicine., and her colleagues report that some stem cells vital to lung cell oxygenation undergo premature aging — and stop dividing and proliferating — when their telomeres are defective. The stem cells are those in the alveoli, the tiny air exchange sacs where blood takes up oxygen.

In studies of these isolated stem cells and in mice, Armanios’ team discovered that dormant or senescent stem cells send out signals that recruit immune molecules to the lungs and cause the severe inflammation that is also a hallmark of emphysema and related lung diseases.

Until now, Armanios says, researchers and clinicians have thought that “inflammation alone is what drives these lung diseases and have based therapy on anti-inflammatory drugs for the last 30 years.”

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By |March 31st, 2015|Uncategorized|0 Comments

Researchers Discover New Way To Promote Regeneration of Heart Tissue

Source: Medical Express. Image: Adult cardiomyocyte that has re-entered the cell cycle after expression of miR302-367. Credit: Lab of Ed Morrisey, PhD, Perelman School of Medicine, University of Pennsylvania

(PHILADELPHIA, Penn.) — The heart tissue of mammals has limited capacity to regenerate after an injury such as a heart attack, in part due to the inability to reactivate a cardiac muscle cell and proliferation program. Recent studies have indicated a low level of cardiac muscle cell (cardiomyocytes) proliferation in adult mammals, but it is insufficient to repair damaged hearts.

A team led by Ed Morrisey, PhD, a professor of Medicine and Cell and Developmental Biology and the scientific director of the Institute for Regenerative Medicine in the Perelman School of Medicine at the University of Pennsylvania, has now shown that a subset of RNA molecules, called microRNAs, is important for cardiomyocyte cell proliferation during development and is sufficient to induce proliferation in cardiomyocytes in the adult heart. MicroRNAs, which do not generate proteins, repress gene expression by binding messenger RNAs, which do generate proteins, and promote their degradation. The findings appear this week in Science Translational Medicine.

The team found that the loss of the microRNA cluster miR302-367 in mice led to decreased cardiomyocyte cell proliferation during development. In contrast, increased expression of the microRNA cluster in adult hearts led to a reactivation of proliferation in the normally non-reproducing adult cardiomyocytes.

This reactivation occurred, in part, through repression of a pathway called Hippo that governs cell proliferation and organ size.

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By |March 18th, 2015|Uncategorized|0 Comments