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发帖数: 19049 | 1 ScienceDaily (July 9, 2011) — For the past decade, researchers have tried
to reprogram the identity of all kinds of cell types. Heart cells are one of
the most sought-after cells in regenerative medicine because researchers
anticipate that they may help to repair injured hearts by replacing lost
tissue. Now, researchers at the Perelman School of Medicine at the
University of Pennsylvania are the first to demonstrate the direct
conversion of a non-heart cell type into a heart cell by RNA transfer.
Working on the idea that the signature of a cell is defined by molecules
called messenger RNAs (mRNAs), which contain the chemical blueprint for how
to make a protein, the investigators changed two different cell types, an
astrocyte (a star-shaped brain cell) and a fibroblast (a skin cell), into a
heart cell, using mRNAs.
James Eberwine, PhD, the Elmer Holmes Bobst Professor of Pharmacology, Tae
Kyung Kim, PhD, post-doctoral fellow, and colleagues report their findings
online in the Proceedings of the National Academy of Sciences. This approach
offers the possibility for cell-based therapy for cardiovascular diseases.
"What's new about this approach for heart-cell generation is that we
directly converted one cell type to another using RNA, without an
intermediate step," explains Eberwine. The scientists put an excess of heart
cell mRNAs into either astrocytes or fibroblasts using lipid-mediated
transfection, and the host cell does the rest. These RNA populations (
through translation or by modulation of the expression of other RNAs) direct
DNA in the host nucleus to change the cell's RNA populations to that of the
destination cell type (heart cell, or tCardiomyocyte), which in turn
changes the phenotype of the host cell into the destination cell.
The method the group used, called Transcriptome Induced Phenotype Remodeling
, or TIPeR, is distinct from the induced pluripotent stem cell (iPS)
approach used by many labs in that host cells do not have to be
dedifferentiated to a pluripotent state and then redifferentiated with
growth factors to the destination cell type. TIPeR is more similar to prior
nuclear transfer work in which the nucleus of one cell is transferred into
another cell where upon the transferred nucleus then directs the cell to
change its phenotype based upon the RNAs that are made. The tCardiomyocyte
work follows directly from earlier work from the Eberwine lab, where neurons
were converted into tAstrocytes using the TIPeR process.
The team first extracted mRNA from a heart cell, then put it into host cells
. Because there are now so many more heart-cell mRNAs versus astrocyte or
fibroblast mRNAs, they take over the indigenous RNA population. The heart-
cell mRNAs are translated into heart-cell proteins in the cell cytoplasm.
These heart-cell proteins then influence gene expression in the host nucleus
so that heart-cell genes are turned on and heart-cell-enriched proteins are
made.
To track the change from an astrocyte to heart cell, the team looked at the
new cells' RNA profile using single cell microarray analysis; cell shape;
and immunological and electrical properties. While TIPeR-generated
tCardiomyocytes are of significant use in fundamental science it is easy to
envision their potential use to screen for heart cell therapeutics, say the
study authors. What's more, creation of tCardiomyoctes from patients would
permit personalized screening for efficacy of drug treatments; screening of
new drugs; and potentially as a cellular therapeutic.
These studies were enabled through the collaboration of a number of
investigators spanning multiple disciplines including Vickas Patel, MD and
Nataliya Peternko from the Division of Cardiovascular Medicine, Miler Lee,
PhD and Junhyong Kim, PhD from the Department of Biology and Jai-Yoon Sul,
PhD and Jae Hee Lee, PhD also from the Department of Pharmacology, all from
Penn. This work was funded by grants from the W. M. Keck Foundation, the
National Institutes of Health Director's Office, and the Commonwealth of
Pennsylvania. |
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