Search

Background: The optimal cell-matrix combination for robust and sustained myocardial restoration has not been identified. The present study utilizes embryonic stem cells as the substrate of bioartificial myocardial tissue and evaluates engraftment in, and functional recovery of, the recipient heart. Methods: Collagen type I was populated with undifferentiated green fluorescent protein (GFP)-positive mouse embryonic stem cells. An intramural left ventricular pouch was fashioned after ligation of the left anterior descending artery in an athymic nude rat heterotopic heart transplant model. The bioartificial mixture (0.125 ml) was implanted in the infarcted area within the pouch. Echocardiography was performed to assess fractional shortening in: Group I, infarcted rats that received cell-matrix implants; Group II, rats given matrix implant without cells; Group III, rats given no matrix or cells; and Group IV, rats receiving transplanted hearts without ligation (n = 5/group). Hearts were stained for GFP, cardiac markers (connexin-43, α-sarcomeric actin), hematoxylin-eosin (H&E) and trichrome. Results: Embryonic stem cells formed stable intramyocardial grafts that were incorporated into the surrounding area without distorting myocardial geometry, thereby preventing ventricular wall thinning (anterior wall thickness was: Group I, 1.4 ± 0.1 mm; Group II, 1.0 ± 0.1 mm, Group III, 0.9 ± 0.2 mm; and Group IV, 1.3 ± 0.2 mm). The inoculated cells expressed connexin-43 and α-sarcomeric actin in vivo. Fractional shortening was better in embryonic stem cell-treated animals (Group I, 21.5 ± 3.5%; Group II, 12.4 ± 2.8%; Group III, 8.2 ± 2.9%; Group IV, 23.2 ± 4.2%). Conclusions: Embryonic stem cells are an efficient alternative substrate for myocardial tissue engineering and can prevent myocardial wall thinning and improve contractility after implantation into injured myocardium in a 3-dimensional matrix. Copyright © 2005 by the International Society for Heart and Lung Transplantation.

ministered via tail vein injection immediately after clamp release and on postoperative days 2 and 4. Another group of rats underwent sham thoracotomies without vessel clamping. On postoperative day 5, animals were sacrificed and lung tissue specimens were analyzed with light and fluorescence microscopy for the presence of MSC-eGFP and SDF-1. Quantitative analysis of lung tissue and serum for SDF-1 was achieved with RT-PCR and ELISA techniques, respectively. MSC were examined for the presence of CXCR4, the receptor to SDF-1, using immunocytochemistry. Results: IRI lung tissue demonstrated greater levels of MSC-eGFP as examined by immunohistologic analysis with both light and fluorescence microscopy as compared with uninjured lung tissue. There was a 2.5-fold increase in the quantity of SDF-1 in the IRI lungs compared to the uninjured lungs (p 0.01) as determined by quantitative RT-PCR. Examination of serum SDF-1 levels using ELISA showed no difference between animals subjected to lung IRI and sham thoracotomy. However, lung tissue analysis for SDF-1 by quantitative RT-PCR demonstrated significantly higher levels in IRI lungs compared to control lungs. The presence of CXCR4 on MSC was confirmed with immunocytology. Conclusions: Circulating MSC can populate IRI lungs. SDF-1 is upregulated locally in IRI lungs and may serve to recruit CXCR4 expressing MSC to the injured lung tissue.

Purpose: Ischemia/reperfusion (IR) injury in lung transplantation is a major cause of acute graft dysfunction, and is characterized by the production of pro-inflammatory cytokines such as IL-1 , and apoptosis of donor respiratory epithelium. We tested the hypothesis that intratracheal administration of adenovirus, overexpressing the human anti-apoptotic protein Bcl-2, will inhibit IR injury to donor lung allografts. Procedures: PVG (RT1c) rats underwent in-vivo intratracheal administration of 1.0x10pfu of either AdvBcl-2 in PBS (n 7), AdvNull in PBS (n 6) or PBS alone (n 8). The left lungs were procured after 24hrs of in-vivo incubation. After 1hr (Group I) or 24hrs (Group II, AdvBcl-2 in PBS vs. AdvNull in PBS) of cold ischemia, donor lungs were orthotopically transplanted into ACI (RT1a) recipients and reperfused for 2hrs. Peak inspiratory pressures (PIPs) were measured, and grafts were excised and analyzed by ELISA, activated caspase-3 assay and histology. Donor pulmonary vein paO2 was measured in Group II. Results: Human Bcl-2 protein was overexpressed in AdvBcl-2 treated lungs compared to AdvNull and PBS alone treated lungs at the time of transplantation (p 0.05), and localized in the alveolar epithelium. The Bcl-2 overexpression in AdvBcl-2 lungs were identical in Groups I and II . In Group I, AdvBcl-2 treated lungs demonstrated reduced PIPs compared to AdvNull and PBS alone treated controls (p 0.01), decreased intragraft IL-1 cytokine (p 0.05), cytochrome c (p 0.01), caspase-3 activity (p 0.05), and ISOL TUNNEL positive nuclei (1.7% 0.7% vs. 4.7% 1.1%, and 6.1% 0.4%, p 0.05). In Group II animals, AdvBcl-2 lungs maintained significant decreases in IL-1 production, caspase-3 activity, and ISOL TUNNEL positive nuclei (3.6% 0.8% vs.19.3% 3.6%) and higher donor pulmonary vein paO2 (p 0.05) compared to AdvNull lungs. Conclusions: Intratracheal adenoviral overexpression of human Bcl-2 limits ischemia/reperfusion injury, improves post-transplant lung function and may serve as a valuable gene therapy regimen in human lung transplantation.