New work suggests that a common, inexpensive and safe chemical could slow the aging of human skin. The researchers found evidence that the chemical--an antioxidant called methylene blue--could slow or reverse several well-known signs of aging when tested in cultured human skin cells and simulated skin tissue. The study was published online in the journal Scientific Reports.

"Our work suggests that methylene blue could be a powerful antioxidant for use in skin care products," said senior author on the study. "The effects we are seeing are not temporary. Methylene blue appears to make fundamental, long-term changes to skin cells."

The researchers tested methylene blue for four weeks in skin cells from healthy middle-aged donors, as well as those diagnosed with progeria--a rare genetic disease that mimics the normal aging process at an accelerated rate. In addition to methylene blue, the researchers also tested three other known antioxidants: N-Acetyl-L-Cysteine (NAC), MitoQ and MitoTEMPO (mTEM).

In these experiments, methylene blue outperformed the other three antioxidants, improving several age-related symptoms in cells from both healthy donors and progeria patients. The skin cells (fibroblasts, the cells that produce the structural protein collagen) experienced a decrease in damaging molecules known as reactive oxygen species, a reduced rate of cell death and an increase in the rate of cell division throughout the four-week treatment.

Next, researchers tested methylene blue in fibroblasts from older donors (>80 years old) again for a period of four weeks. At the end of the treatment, the cells from older donors had experienced a range of improvements, including decreased expression of two genes commonly used as indicators of cellular aging: senescence-associated beta-galactosidase and p16.

"I was encouraged and excited to see skin fibroblasts, derived from individuals more than 80 years old, grow much better in methylene blue-containing medium with reduced cellular senescence markers," said lead author of the study. "Methylene blue demonstrates a great potential to delay skin aging for all ages."

The researchers then used simulated human skin to perform several more experiments. This simulated skin--a three-dimensional model made of living skin cells--includes all the major layers and structures of skin tissue, with the exception of hair follicles and sweat glands. The model skin could also be used in skin irritation tests required by the Food and Drug Administration for the approval of new cosmetic products, senior author said.

"This system allowed us to test a range of aging symptoms that we can't replicate in cultured cells alone," senior author said. "Most surprisingly, we saw that model skin treated with methylene blue retained more water and increased in thickness--both of which are features typical of younger skin."

The researchers also used the model skin to test the safety of cosmetic creams with methylene blue added. The results suggest that methylene blue causes little to no irritation, even at high concentrations.

https://www.nature.com/articles/s41598-017-02419-3