Host-derived circulating cells do not significantly contribute to cardiac regeneration in heterotopic rat heart transplants.
OBJECTIVE
The aim of this study was to investigate the contribution of host-derived circulating cells to cardiac repair after tissue damage using the model of heterotopic heart transplantation between transgenic recipient rats expressing green fluorescent protein (GFP) and wild-type donors.


METHODS
Unlabeled donor rat hearts, some of which underwent prolonged cold ischemia pretreatment, were transplanted into the abdominal cavity of GFP+ transgenic recipient rats and were analyzed 15 and 90 days after surgery. An additional experimental group underwent heart transplantation following administration of granulocyte-colony stimulatory factor (G-CSF) to mobilize bone marrow cells.


RESULTS
Most transplants contained GFP+ mature cardiomyocytes. However, systematic counting in the transplants showed that the proportion of GFP+ cardiomyocytes was only 0.0005% to 0.008% of all cardiomyocytes. These relative proportions did not change after G-CSF treatment, despite evidence for sustained marrow cell mobilization. Confocal image analysis showed that the majority of GFP+ cardiomyocytes contained a high number of nuclei, suggesting that these cells may derive from fusion events. Very rarely, small GFP+ undifferentiated cells, expressing GATA-4, were also identified. Occasionally, GFP+ endothelial cells, but not smooth muscle cells, were detected in blood vessels of some transplants.


CONCLUSIONS
Our results demonstrate that cardiomyocytes expressing a host transgenic marker are detectable in heterotopic heart transplants; however, they do not significantly contribute to repopulation of the damaged myocardium.
Ausoni
Simonetta
S
Department of Biomedical Sciences, University of Padua, Viale G. Colombo 3, 35121 Padua, Italy. ausoni@civ.bio.unipd.it
Zaglia
Tania
T
Dedja
Arben
A
Di Lisi
Raffaella
R
Seveso
Michela
M
Ancona
Ermanno
E
Thiene
Gaetano
G
Cozzi
Emanuele
E
Schiaffino
Stefano
S
D000818:Animals; D030801:Animals, Genetically Modified; D015415:Biomarkers / Q000032:analysis; D001854:Bone Marrow Cells / Q000166:cytology; D002452:Cell Count; D002459:Cell Fusion; D004247:DNA / Q000032:analysis; D042783:Endothelial Cells / Q000473:pathology; D005260:Female; D005434:Flow Cytometry; D050991:GATA4 Transcription Factor / Q000032:analysis; D016179:Granulocyte Colony-Stimulating Factor / Q000627:therapeutic use; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D016027:Heart Transplantation; D019650:Hematopoietic Stem Cell Mobilization; D007091:Image Processing, Computer-Assisted; D008297:Male; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration; D016042:Transplantation, Heterotopic / Q000473:pathology
D015415:Biomarkers; D050991:GATA4 Transcription Factor; D016179:Granulocyte Colony-Stimulating Factor; D049452:Green Fluorescent Proteins; D004247:DNA