Xenografted adult human mesenchymal stem cells provide a platform for sustained biological pacemaker function in canine heart.
BACKGROUND
Biological pacemaking has been performed with viral vectors, human embryonic stem cells, and adult human mesenchymal stem cells (hMSCs) as delivery systems. Only with human embryonic stem cells are data available regarding stability for >2 to 3 weeks, and here, immunosuppression has been used to facilitate survival of xenografts. The purpose of the present study was to determine whether hMSCs provide stable impulse initiation over 6 weeks without the use of immunosuppression, the "dose" of hMSCs that ensures function over this period, and the catecholamine responsiveness of hMSC-packaged pacemakers.


RESULTS
A full-length mHCN2 cDNA subcloned in a pIRES2-EGFP vector was electroporated into hMSCs. Transfection efficiency was estimated by GFP expression. I(HCN2) was measured with patch clamp, and cells were administered into the left ventricular anterior wall of adult dogs in complete heart block and with backup electronic pacemakers. Studies encompassed 6 weeks. I(HCN2) for all cells was 32.1+/-1.3 pA/pF (mean+/-SE) at -150 mV. Pacemaker function in intact dogs required 10 to 12 days to fully stabilize and persisted consistently through day 42 in dogs receiving > or =700,000 hMSCs (approximately 40% of which carried current). Rhythms were catecholamine responsive. Tissues from animals killed at 42 days manifested neither apoptosis nor humoral or cellular rejection.


CONCLUSIONS
hMSCs provide a means for administering catecholamine-responsive biological pacemakers that function stably for 6 weeks and manifest no cellular or humoral rejection at that time. Cell doses >700,000 are sufficient for pacemaking when administered to left ventricular myocardium.
Plotnikov
Alexei N
AN
Center for Molecular Therapeutics, Columbia University, New York, NY 10032, USA.
Shlapakova
Iryna
I
Szabolcs
Matthias J
MJ
Danilo
Peter
P
Lorell
Beverly H
BH
Potapova
Irina A
IA
Lu
Zhongju
Z
Rosen
Amy B
AB
Mathias
Richard T
RT
Brink
Peter R
PR
Robinson
Richard B
RB
Cohen
Ira S
IS
Rosen
Michael R
MR
D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D004553:Electric Conductivity; D004562:Electrocardiography; D004837:Epinephrine / Q000494:pharmacology; D006321:Heart / Q000502:physiology*; D006327:Heart Block / Q000503:physiopathology; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000235:genetics; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018408:Patch-Clamp Techniques; D015221:Potassium Channels; D014162:Transfection; D014183:Transplantation, Heterologous
C578710:HCN2 protein, human; C578711:Hcn2 protein, mouse; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels; D004837:Epinephrine