Sunlight continues to damage skin in the dark

Much of the damage that ultraviolet radiation (UV) does to skin occurs hours after sun exposure, a team of Yale-led researchers concluded in a study that was published online by the journal Science.Exposure to UV light from the sun or from tanning beds can damage the DNA in melanocytes, the cells that make the melanin that gives skin its color. This damage is a major cause of skin cancer, the most common form of cancer in the United States. In the past, experts believed that melanin protected the skin by blocking harmful UV light. But there was also evidence from studies suggesting that melanin was associated with skin cell damage.In the current study, Douglas E. Brash, clinical professor of therapeutic radiology and dermatology at Yale School of Medical, and his co-authors first exposed mouse and human melanocyte cells to radiation from a UV lamp. The radiation caused a type of DNA damage known as a cyclobutane dimer (CPD), in which two DNA “letters” attach and bend the DNA, preventing the information it contains from being read correctly. To the researchers’ surprise, the melanocytes not only generated CPDs immediately but continued to do so hours after UV exposure ended. Cells without melanin generated CPDs only during the UV exposure.

Read the rest of the article at  http://www.medicalnewstoday.com/releases/289728.php.

Human stem cells repair damage caused by radiation therapy for brain cancer in rats

For patients with brain cancer, radiation is a powerful and potentially life-saving treatment, but it can also cause considerable and even permanent injury to the brain. Now, through preclinical experiments conducted in rats, Memorial Sloan Kettering Cancer Center researchers have developed a method to turn human stem cells into cells that are instructed to repair damage in the brain. Rats treated with the human cells regained cognitive and motor functions that were lost after brain irradiation. The findings are reported in the February 5 issue of the journal Cell Stem Cell.During radiation therapy for brain cancer, progenitor cells that later mature to produce the protective myelin coating around neurons are lost or significantly depleted, and there is no treatment available to restore them. These myelinating cells–called oligodendrocytes–are critical for shielding and repairing the brain’s neurons throughout life.A team led by neurosurgeon Viviane Tabar, MD, and research associate Jinghua Piao, PhD, of the Memorial Sloan Kettering Cancer Center in New York City, wondered whether stem cells could be coaxed to replace these lost oligodendrocyte progenitor cells. They found that this could be achieved by growing stem cells–either human embryonic stem cells or induced pluripotent stem cells derived from skin biopsies–in the presence of certain growth factors and other molecules.

Read the rest of the article at  http://www.medicalnewstoday.com/releases/289083.php.