PORTLAND -- A study at Oregon Health & Science University has resulted in the first successful birth of chimeric monkeys, developed from the stem cells of two separate embryos, researchers said.

The study pointed out major differences in stem cell types and it will impact future understanding of their regenerative capabilities, according to Dr. Shoukhrat Mitalipov at OHSU's Oregon National Primate Research Center.

The research was conducted to provide insight into the differences between natural stem cells and cultured stem cells, Mitalipov said. The findings also showed a difference between primate stem cells and rodent stem cells.

The natural stem cells residing in early embryonic stages of the rhesus macaque--called totipotent cells --were able to divide and produce all the cells of the organism's body and placenta, Mitalipov said. However, the stem cells derived from embryos in the later stages were unable to reproduce the placenta.

Earlier studies had shown that, in mice, either type of cell could produce an embryo that later becomes a chimeric animal. That was not the case in the OHSU macaque study.

The research demonstrated that for reasons yet unknown, chimeric animals can only develop from totipotent cells in a higher animal model, Mitalipov said. OHSU showed this to be the case by successfully producing the world's first primate chimeric offspring, three baby rhesus macaques named Roku, Hex and Chimero.

Stem cell therapies hold great promise for replacing damaged nerve cells in those who have been paralyzed due to a spinal cord injury or for example, in replacing dopamine-producing cells in Parkinson's patients who lose these brain cells resulting in disease, he explained. As we move stem cell therapies from the lab to clinics and from the mouse to humans, we need to understand what these cells do and what they can't do and also how cell function can differ in species.

The research was funded by OHSU and the National Institutes of Health.

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