Fusion of bone marrow-derived stem cells with cardiomyocytes in a heterologous in vitro model.
OBJECTIVE
Recent studies have demonstrated that transplanted bone marrow-derived stem cells (BMCs) possess a broad differentiation potential and are able to form new cardiomyocytes. However, the identity of BMCs as true cardiomyocytes is still ambiguous. Therefore, we investigated the fate of transplanted fluorescence labeled BMCs and cardiomyocytes in co-culture.


METHODS
For cell tracking we used two different fluorescent probes, Vybrant/DiO and Vybrant/DiI. BMCs were taken from human sternal marrow, purified using a Ficoll-gradient-centrifugation, treated with 5-azacytidine and stained with Vybrant/DiO. Furthermore, isolated spontaneous beating cardiomyocytes of neonatal rats (CM) were labeled with Vybrant/DiI. Thereafter, the BMCs were transplanted into CM-cultures and investigated on day 1, 4, 7, 14 and 28 using two-color fluorescence phenotyping by laser-scanning-cytometry (LSC). Two-color positive cells were harvested by patch-clamp technique and beta-MHC mRNA expression was analyzed by single-cell PCR.


RESULTS
Two different morphological phenotypes were observed by LSC. First, isolated DiO labeled BMCs without contact or with direct cell contact to DiI labeled CMs. Second, some BMCs and CMs were double positive for DiO/DiI spontaneously forming hybrids. This population increased by 18% from day 1 to 4 and decreased only slightly until day 28. Additionally, few two-color positive cell formations expressed both human and rat specific beta-MHC mRNA as well as only human beta-MHC mRNA indicating that cell-fusion and transdifferentiation has occurred.


CONCLUSIONS
These observations provide in vitro evidence for spontaneous cell fusion and transdifferentiation of BMCs in co-culture, raising the possibility that the observed phenomenons may contribute to development or maintenance of these cell types.
Garbade
Jens
J
Department of Cardiac Surgery, Heart Center, University of Leipzig, Struempellstr. 39, 04289 Leipzig, Germany. jgmed93@hotmail.com
Schubert
Andreas
A
Rastan
Ardawan Julian
AJ
Lenz
Dominik
D
Walther
Thomas
T
Gummert
Jan Fritz
JF
Dhein
Stefan
S
Mohr
Friedrich-Wilhelm
FW
D000818:Animals; D000831:Animals, Newborn; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002459:Cell Fusion; D018920:Coculture Techniques; D015870:Gene Expression; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D047569:Laser Scanning Cytometry / Q000379:methods; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D024723:Ventricular Myosins / Q000096:biosynthesis / Q000235:genetics
D024723:Ventricular Myosins