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TOKYO - Japanese scientists have successfully regenerated hair on a bald mouse, bringing hope to more than 50 million Americans suffering from hair loss.

In a breakthrough study, researchers at the Tokyo University of Science extracted stem cells from hair follicles in normal mice, and implanted them into the skin of the bald animal. Most of the hair grew back within two to five weeks, and underwent normal growth cycles, meaning the strands grew back even after they were pulled out. They established connections to muscles and nerves underneath the skin, just like natural hair.

The study was published in online journal Nature Communications.

The successful test could lead to a possible cure for hair loss in humans, lead scientist Takashi Tsuji said.

"If there is still hair on the back of the head, then it's possible to use the cells from that, bio-engineer it, and regenerate new hair," Tsuji said. "We're moving our research forward [with that in mind]."

In addition to stem cells in mice, Tsuji implanted cells taken from human follicles, to grow fur on the bald mouse.

He combined a number of stem cells to adjust the density and color of the hair, raising the possibility of a cure to graying strands.

Tokyo researchers are the latest scientists to tackle hair loss, using mice. Researchers at the University of California-Los Angeles last year tumbled upon a chemical compound that blocked the effects of stress, considered a factor in hair loss. Three months after treating bald mice with the compound, the creatures grew full heads and backs of hair.

A team at the Kennedy Krieger Institute in Baltimore and Johns Hopkins University corrected a gene mutation to re-grow fur in bald mice in 2005.

None of the studies have led to cures for hair loss in humans.

It will take about a decade, Tsuji said, before he can apply the treatment to patients.