The vast majority of bone-marrow-derived cells integrated into mdx muscle fibers are silent despite long-term engraftment.
Bone-marrow-derived cells can contribute nuclei to skeletal muscle fibers. However, serial sectioning of muscle in mdx mice implanted with GFP-labeled bone marrow reveals that only 20% of the donor nuclei chronically incorporated in muscle fibers show dystrophin (or GFP) expression, which is still higher than the expected frequency of "revertant" fibers, but there is no overall increase above controls over time. Obviously, the vast majority of incorporated nuclei either never or only temporarily turn on myogenic genes; also, incorporated nuclei eventually loose the activation of the beta-actin::GFP transgene. Consequently, we attempted to enhance the expression of dystrophin. In vivo application of the chromatin-modifying agents 5-azadeoxycytidine and phenylbutyrate as well as local damage by cardiotoxin injections caused a small increase in dystrophin-positive fibers without abolishing the appearance of "silent" nuclei. The results thus confirm that endogenous repair processes and epigenetic modifications on a small-scale lead to dystrophin expression from donor nuclei. Both effects, however, remain below functionally significant levels.
Wernig
Gerlinde
G
Department of Physiology, University of Bonn, Wilhelmstrasse 31, D-53111 Bonn, Germany.
Janzen
Viktor
V
Schäfer
Ralf
R
Zweyer
Margit
M
Knauf
Ulrich
U
Hoegemeier
Oliver
O
Mundegar
Rustam R
RR
Garbe
Stefan
S
Stier
Sebastian
S
Franz
Thomas
T
Wernig
Marius
M
Wernig
Anton
A
D000199:Actins / Q000378:metabolism; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology* / Q000378:metabolism*; D016026:Bone Marrow Transplantation; D002454:Cell Differentiation; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D004179:Cobra Cardiotoxin Proteins / Q000494:pharmacology; D016189:Dystrophin / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D017930:Genes, Reporter / Q000235:genetics; D008297:Male; D051379:Mice; D018101:Mice, Inbred mdx; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000378:metabolism* / Q000473:pathology; D053652:Nuclear Transfer Techniques; D013997:Time Factors; D019076:Transgenes / Q000235:genetics
D000199:Actins; D002843:Chromatin; D004179:Cobra Cardiotoxin Proteins; D016189:Dystrophin