Sca-1+ stem cell survival and engraftment in the infarcted heart: dual role for preconditioning-induced connexin-43.
BACKGROUND
We report that elevated connexin-43 (Cx-43) in stem cells preconditioned with insulin-like growth factor-1 (IGF-1) is cytoprotective and reprograms the cells for cardiomyogenic differentiation.


RESULTS
Sca-1+ cells were preconditioned with 100 nmol/L IGF-1 for 30 minutes followed by 8 hours of oxygen glucose deprivation to assess the cytoprotective effects of preconditioning. LDH release assay, cytochrome c release, and mitochondrial membrane potential assay showed improved survival of preconditioned Sca-1+ cells under oxygen glucose deprivation compared with nonpreconditioned Sca-1+ cells via PI3K/Akt-dependent caspase-3 downregulation. We observed PI3K/Akt-dependent upregulation of cardiac-specific markers including MEF-2c (2.5-fold), GATA4 (3.1-fold), and Cx-43 (3.5-fold). Cx-43 inhibition with specific RNA interference reduced cell survival under oxygen glucose deprivation and after transplantation. In vivo studies were performed in a female rat model of acute myocardial infarction (n=78). Animals were grouped to receive intramyocardially 70 microL Dulbecco modified Eagles medium without cells (group 1) or containing male 1 x 10(6) nonpreconditioned Sca-1+ cells (group 2) or preconditioned Sca-1+ (group 3) cells labeled with PKH26. Survival of the preconditioned Sca-1+ cells was 5.5-fold higher in group 3 compared with group 2 at 7 days after transplantation. Confocal imaging after actinin and Cx-43 specific immunostaining showed extensive engraftment and myogenic differentiation of preconditioned Sca-1+ cells. Compared with group 2, group 3 showed increased blood vessel density (22.3+/-1.7 per microscopic field; P<0.0001) and attenuated infarction size (23.3+/-3.6%; P=0.002). Heart function indices including ejection fraction (56.2+/-3.5; P=0.029) and fractional shortening (24.3+/-2.1; P=0.03) were improved in group 3 compared with group 2.


CONCLUSIONS
Preconditioning with IGF-1 reprograms Sca-1+ for prosurvival signaling and cardiomyogenic differentiation with an important role for Cx-43 in this process.
Department of Pathology and Laboratory Medicine, 231 Albert Sabin Way, University of Cincinnati, Cincinnati, OH 45267-0529, USA.
Gang
G
Lu
Husnain K
HK
Haider
Shujia
S
Jiang
Muhammad
M
Ashraf
D000818:Animals; D000950:Antigens, Ly / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000637:transplantation; D018031:Connexin 43 / Q000235:genetics / Q000502:physiology*; D005260:Female; D005947:Glucose / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D008565:Membrane Proteins / Q000032:analysis; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D039902:Multipotent Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000637:transplantation; D009203:Myocardial Infarction / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
D000950:Antigens, Ly; D018031:Connexin 43; D005947:Glucose; D007334:Insulin-Like Growth Factor I; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C074650:Ly6a protein, mouse; C514862:Akt1 protein, mouse