Cardiotin localization in mitochondria of cardiomyocytes in vivo and in vitro and its down-regulation during dedifferentiation.
BACKGROUND
Cardiotin expression is observed in adult cardiac tissue. In the present study, we provide evidence for the specific localization of cardiotin in cardiac mitochondria and for its down-regulation during adaptive remodeling (dedifferentiation) of cardiomyocytes.


METHODS
Immunocytochemistry was used to study cardiotin localization in adult rabbit papillary muscle, in late-stage embryonic rabbit left ventricular tissue, and in left ventricle samples of rabbits suffering from pressure and volume overload. Western blot analysis of cardiotin was performed in purified pig heart mitochondrial fractions. Cardiotin expression was monitored in vitro in isolated adult rat and rabbit left ventricular cardiomyocytes.


RESULTS
Western blot analysis revealed the presence of cardiotin in the mitochondrial fractions of pig heart. Immunoelectron microscopy confirmed the presence of cardiotin in cardiac mitochondria of normal adult rabbits both in vivo and in vitro. Quantification of the localization of immunogold particles suggests an association of cardiotin with the mitochondrial inner membrane. Cardiotin expression is initiated in late-stage embryonic rabbit heart, whereas in adult ventricular tissue cardiotin clearly stained longitudinal arrays of mitochondria. Pressure- and volume-overloaded myocardium showed a reduction in cardiotin expression in dispersed local myocardial areas. Cell cultures of adult cardiomyocytes showed a gradual loss in cardiotin expression in parallel with a sarcomeric remodeling.


CONCLUSIONS
Our results demonstrate the specific localization of cardiotin in adult cardiomyocyte mitochondria and propose its use as an early marker for cardiomyocyte adaptive remodeling and dedifferentiation.
Driesen
Ronald B
RB
Department of Molecular Cell Biology, School for Cardiovascular Diseases (CARIM), University of Maastricht, Maastricht, The Netherlands. r.driesen@molcelb.unimaas.nl
Verheyen
Fons K
FK
Schaart
Gert
G
de Mazière
Ann
A
Viebahn
Christoph
C
Prinzen
Frits W
FW
Lenders
Marie-Hélène
MH
Debie
Wiel
W
Totzeck
Andreas
A
Borgers
Marcel
M
Ramaekers
Frans C S
FC
D000185:Actinin / Q000378:metabolism*; D000818:Animals; D001022:Aortic Valve Insufficiency / Q000378:metabolism* / Q000473:pathology; D054337:Cell Dedifferentiation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D015536:Down-Regulation; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006321:Heart / Q000196:embryology; D006352:Heart Ventricles / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D009928:Organ Specificity; D010210:Papillary Muscles / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D011817:Rabbits; D051381:Rats; D013552:Swine
C104594:cardiotin; D000185:Actinin