Leroy C. Stevens, Ph.D., 1920-2015

Bar Harbor, Maine – Leroy C. Stevens, Ph.D., a retired Jackson Laboratory scientist acknowledged as the pioneer of embryonic stem cell (ES cell) research, died on March 28.

Stevens was born in Kenmore, N.Y., in 1920. He received his B.S. from Cornell University in 1942 and his Ph.D. in embryology from the University of Rochester in 1952, joining The Jackson Laboratory as a postdoctoral Laboratory Fellow that year.

In 1958, while examining a large testicular tumor on a mouse from the strain known as 129, Stevens noticed that it was composed of many kinds of tissue, including muscle, skin, bone and hair. In later studies, Stevens observed that the tumors, known as teratocarcinomas, produced not only the various kinds of tissues as expected, but also groups of undifferentiated cells with the capacity to grow into a wide range of tissue types. He dubbed the latter cells "pluripotent embryonic stem cells."

n 1981, Dr. Gail Martin of the University of California was the first to isolate mouse embryonic stem cells from normal embryos, a feat repeated shortly thereafter by Drs. Martin Evans and Matthew Kaufman in England. By the late 1990s, the first human ES cells were isolated. In 2004, on the occasion of The Jackson Laboratory’s 75th anniversary, Martin commented, "Stevens’ contributions to stem cell biology built the road that led to current knowledge about the properties and potential of human ES cells."

Today ES cells are hailed by researchers and patient groups alike as a future font of new treatments for human diseases. Theoretically, human ES cells can be isolated and, given proper conditions, their development steered to create specific kinds of cells, tissues and potentially even replacement organs for patients with deadly diseases. Researchers at The Jackson Laboratory and other institutions are also working on the promising avenue of induced pluripotent stem cells: reprogramming adult cells to a stem-cell-like state to generate healthy new tissue.

Profiling Stevens in 2000 in The Scientist, Dr. Ricki Lewis noted, "Leroy Stevens is truly the unsung hero of stem cell research."

Stevens’ later studies focused on developing mouse models for the testing of chemotherapeutic drugs. In 1967 he rose to the position of senior staff scientist—a position now designated as professor—and retired from the Laboratory in 1989.

The Jackson Laboratory extends sincere condolences to Stevens’ family, including his son-in-law and longtime Jackson Laboratory employee Hook Wheeler, friends and colleagues.


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