Article

Elevated p21 mRNA level in skeletal muscle of DMD patients and mdx mice indicates either an exhausted satellite cell pool or a higher p21 expression in dystrophin-deficient cells per se.

Technische Fachhochschule Berlin, University of Applied Science, Department of Biotechnology, Germany.
Journal of Molecular Medicine (impact factor: 4.67). 02/2000; 78(10):569-74. pp.569-74
Source: PubMed

ABSTRACT Abnormalities in proliferation and differentiation of the dystrophin-deficient muscle are a controversial aspect of the pathogenesis of Duchenne muscular dystrophy (DMD). Analyses of molecules involved in cell cycle modulation do not exist in this context. Cells withdrawn from the cell cycle permanently express p21. The fact that p2 1, in contrast to other cell cycle proteins, is not diminished when myotubes are reexposed to growth media, allocates this cyclin-dependent kinase inhibitor a special function. Here we report for the first time statistically increased p21 mRNA levels in dystrophin-deficient muscle tissue. Only 42% of conventional RT-PCRs from six muscle samples of human controls yielded positive results but almost all skeletal muscle biopsy samples (87%) from DMD patients (n=5). For p21 mRNA quantification in murine muscle samples we were able to use the exact real-time TaqMan PCR method due to generally higher p21 mRNA levels than in human muscles. In addition, contamination with fibroblasts can be excluded for the murine samples because they do not demonstrate fibrosis at the age of 350 days but start to lose their regenerative capacity. In accord with the results in humans, we observed p21 mRNA levels in mdx mice that were approx. four times as high as those in control mice. Elevated p21 mRNA level may indicate a shift in cell composition towards differentiated p21 expressing cells as a result of an exhausted pool of undifferentiated, non-p21-expressing satellite cells due to previous cycles of de- and regeneration. Alternatively, dystrophin-deficient cells per se may express higher p21 levels for unknown reasons. Although we cannot distinguish between these possibilities, the eventual transfec tion of a patient's own satellite cells with p21 antisense oligonucleotides may enable the dystrophic process to be influenced.

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Keywords

cell cycle
 
cell cycle modulation
 
cell cycle proteins
 
control mice
 
controversial aspect
 
cyclin-dependent kinase inhibitor
 
differentiated p21
 
dystrophic process
 
dystrophin-deficient cells
 
dystrophin-deficient muscle
 
dystrophin-deficient muscle tissue
 
Elevated p21 mRNA level
 
growth media
 
higher p21 levels
 
mdx mice
 
non-p21-expressing satellite cells
 
p21 antisense oligonucleotides
 
patient's own satellite cells
 
regenerative capacity
 
special function