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Chimeric Primates and Embryonic Stem Cell Inequalities Print E-mail
SciMed - Biology
TS-Si News Service   
Wednesday, 11 January 2012 16:00
Roku and Hex. Image courtesy of Oregon Health & Science University.Portland, OR, USA. Scientists have discovered a key distinction between species and between different kinds of stem cells that improves our understanding of their future potential in regenerative medicine.

Research at the Oregon National Primate Research Center (ONPRC) resulted in the first successful birth of chimeric monkeys — developed from stem cells taken from two separate embryos.


The findings, which appear in the journal Cell, are the outcome of research conducted to gain a better understanding of the differences between natural stem cells residing in early embryos and their cultured counterparts (embryonic stem cells). This study also determined that stem cell functions and abilities are different between primates and rodents, and provides significant new information about how early embryonic stem cells develop and take part in formation of the primate species.



Video courtesy of Dr. Shoukhrat Mitalipov and the Oregon National Primate Research Center (ONPRC).
Time: 00:03:04.


Shoukhrat Mitalipov, PhD, is an associate scientist in the ONPRC Division of Reproductive and Developmental Sciences at the Oregon Health & Science University (OHSU).
The research was conducted to gain a better understanding of the differences between natural stem cells residing in early embryos and their cultured counterparts called embryonic stem cells. This study also determined that stem cell functions and abilities are different between primates and rodents.
  • The first cell type was that of totipotent cells, those from the early embryo that have the ability to divide and produce all of the differentiated cells in the placenta and the body of organism.

  • These were compared with pluripotent cells, those derived from the later stage embryo that have only the ability to become the body but not placenta.

In mice, either totipotent or pluripotent cells from two different animals can be combined to transform into an embryo that later becomes a chimeric animal. However, the current research demonstrated that for reasons yet unknown, chimeric animals can only develop from totipotent cells in a higher animal model: the rhesus macaque.

OHSU researchers 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.

"This is an important development — not because anyone would develop human chimeras — but because it points out a key distinction between species and between different kind of stem cells that will impact our understanding of stem cells and their future potential in regenerative medicine," explained Shoukhrat Mitalipov, Ph.D., an associate scientist in the ONPRC Division of Reproductive and Developmental Sciences.

"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. 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."

CitationGeneration of Chimeric Rhesus Monkeys. Masahito Tachibana, Michelle Sparman, Cathy Ramsey, Hong Ma, Hyo-Sang Lee, Maria Cecilia T. Penedo, Shoukhrat Mitalipov. Cell 2012. doi:10.1016/j.cell.2011.12.007

Highlights

●  Primate ESCs injected into host embryos did not contribute to chimeras
●  Transplanted ICMs did not incorporate into host ICMs but formed separate fetuses
●  Aggregation of 3–6 cleaving embryos formed a single chimeric infant
●  Cleaving embryos cannot serve as a host for testing ESC pluripotency

Abstract

Graphical Abstract.Totipotent cells in early embryos are progenitors of all stem cells and are capable of developing into a whole organism, including extraembryonic tissues such as placenta.

Pluripotent cells in the inner cell mass (ICM) are the descendants of totipotent cells and can differentiate into any cell type of a body except extraembryonic tissues. The ability to contribute to chimeric animals upon reintroduction into host embryos is the key feature of murine totipotent and pluripotent cells.

Here, we demonstrate that rhesus monkey embryonic stem cells (ESCs) and isolated ICMs fail to incorporate into host embryos and develop into chimeras. However, chimeric offspring were produced following aggregation of totipotent cells of the four-cell embryos.

These results provide insights into the species-specific nature of primate embryos and suggest that a chimera assay using pluripotent cells may not be feasible.

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Last Updated on Wednesday, 11 January 2012 15:43