In vivo optical bioluminescence imaging of collagen-supported cardiac cell grafts

Histology-based survival assessment of cell grafts does not allow for in vivo follow-up. In this study we introduce two new experimental models for longitudinal in vivo survival studies of cardiac cell grafts using optical bioluminescence imaging.

H9c2 cardiomyoblasts expressing both firefly luciferase (fluc) and green fluorescent protein (GFP) reporter genes were implanted into Lewis rats. In Model 1, H9c2-fluc-IRES-GFP cells (0.5 x 10(6)) were implanted into a cryoinjured abdominal wall muscle. Cells were injected using either liquid collagen (Matrigel [MG]) or phosphate-buffered saline (PBS) suspension. Cell survival was evaluated in vivo using bioluminescence imaging on days 1, 5 and 10 post-operatively. In model 2, rats underwent ligation of the left anterior descending (LAD) artery. The donor hearts were harvested, and the infarcted region was restored ex situ using 1 x 10(6) H9c2-fluc-IRES-GFP cells seeded in collagen matrix (Gelfoam [GF]) or suspended in PBS (n = 8/group). Hearts were then transplanted into the abdomen of syngeneic recipients. Optical bioluminescence imaging was performed on Days 1, 5, 8 and 14 post-operatively. After 4 weeks, immunohistologic studies were performed.

For model 1, at day 5, bioluminescence signals were markedly higher for the H9c2/MG group (449 +/- 129 photons/second x 10(3)) compared with the H9c2/PBS group (137 +/- 82 photons/second x 10(3)) (p < 0.05). For model 2, bioluminescence signals were significantly (p < 0.04) higher in the H9c2/GF group compared with plain cell injection on days 5 (534 +/- 115 vs 219 +/- 34) and 8 (274 +/- 34 vs 180 +/- 23). Data were in accordance with GFP immunohistology.

Optical bioluminescence is a powerful method for assessment of cardiac cell graft survival in vivo. Collagen matrices support early survival of cardiomyoblasts after transplantation into injured musculature.