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Oct 23, 2009

Researchers Create iPSCs from Somatic Cells without Exogenous Transcription Factors

  • Scientists report that they have transformed somatic cells into induced pluripotent stem cells (iPSCs) without introducing foreign genetic materials. The research also showed that cells taken from a patient’s eye can be reprogrammed to replace or restore cells lost to degenerative diseases. 

    The study, led by Iqbal Ahmad, Ph.D., from the University of Nebraska Medical Center, is published in Stem Cells. The paper is titled “Non Cell-autonomous Reprogramming of Adult Ocular Progenitors: Generation of Pluripotent Stem Cells without Exogenous Transcription Factors.”

    It is the first proof of principle, according to the team, that somatic cells can be reprogrammed into iPSCs through the influence of the microenvironment in which the sampled cells are cultured. The team was able to recruit endogenous genes without the introduction of genetic materials or exogenous factors. They believe that this method could overcome the issue of using virus-mediated expression of exogenous transcription factors.

    The cornea is continuously regenerated, and the progenitors that sustain corneal regeneration and repair are harbored in the limbal epithelium, a circular epithelium between cornea and conjunctiva. These cells, when removed from their niche and cultured in the presence of the protein Noggin generate neural progenitors, which differentiate into functional neurons under the influence of extracellular cues.

    The team sampled progenitor eye cells from laboratory rats. The reprogramming involved two stages: initial induction of the expression of iPS cell genes Klf4, Sox2, and c-Myc under the influence of defined exogenous factors (FGF2 and Noggin) and the activation of Oct4 and Nanog under the influence of embryonic stem cell (ESCs) conditioned medium. The unidentified activities elaborated by ESCs effectively influenced the maintenance of the expression of all four iPS cell genes (Oct4, Klf4, Sox2, and c-Myc).

    “Our findings provide evidence for an emerging view that somatic cells may be reprogrammed safely and simply by defined chemicals and other factors, which may facilitate their clinical use,” says Dr. Ahmad. “The next step is to know how robust the reprogramming is and what existed within the microenvironment to cause it.”

    By reprogramming progenitor eye cells to resemble stem cells, they acquired the properties necessary to replace or restore neurons, cardiomyocytes, and hepatocytes.

    The limbal progenitors can be obtained from 2 mm limbal biopsy of a patient without affecting vision. “This research shows that it is possible to take cells from a patient's eye without affecting vision and reprogram them for use in autologous cell therapy to replace or rescue degenerating cells,” concludes Dr. Ahmad. “This would allow us to circumvent ethical issues and the problems caused by the immune system rejecting foreign cells.”

     



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