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| Effects of strain
on gene transfer |
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Gene
therapy is an important advancement with the potential to
revolutionize clinical medicine. However, current technologies
to deliver
genes are not sufficient to make this a reality in patients
under even optimum conditions, let alone under stresses associated
with many disease states. Prolonged and even short-term exposure
to mechanical ventilation can cause profound changes in the
alveolar epithelium. We are trying to develop non-viral gene
therapy approaches to treat the acutely injured lung. As
such, we must understand the mechanisms of gene transfer
in alveolar
epithelial cells under conditions that mimic those found
during lung injury and its management (i.e., ventilation).
Mechanical
stretch induces numerous biological responses in cells, including
alterations
in the cytoskeleton, activation of cell signaling pathways,
and upregulation of transcription factors. Intriguingly,
these responses are directly related to the process of gene
delivery
to cells and tissues: (click
image for larger view)
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Exogenous DNA, either viral or non-viral, must cross the plasma
membrane into the cell, travel through the cytooplasm and the cytoskeletal
networks, enter the nucleus, and be transcribed in order for gene
therapy to be successful. Plasmids most likely utilize the cytoskeletal
network for movement through the cytoplasm, and form complexes
with transcription factors for their nuclear entry. |
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Because mechanical
stress alters both the cytoskeleton and the levels and subcellular
localization of many transcription factors, it is likely
that mechanical strain could play a large role in gene delivery.
Indeed, in preliminary
studies we have observed
that cyclic stretch greatly enhances gene delivery and expression
in alveolar epithelial cells.
Click image for larger view
We hypothesize that the cytoskeletal reorganization and
transcription factor activation induced by mechanical stretch
stimulates the ability of exogenous DNA, once inside the
cell, to travel through the cytoplasm and into the nucleus
for gene expression. Although not a "physiologically" normal
process, the interactions of exogenous DNA |
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vital to methods scientists use everyday and form the basis
for the next
paradigm of disease treatment: gene therapy. Because cyclic
stretch of alveolar epithelial
cells mimics the mechanical force induced by ventilators on
the lung, we may ultimately extend our findings on stretch-induced
increases in gene transfer to the lung in vivo to develop improved
approaches for gene delivery. |
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