Gene therapy for heart transplantation-associated coronary arteriosclerosis

Control of cell proliferation in atherosclerosis: insights from animal models and human studies

Excessive hyperplastic cell growth within occlusive vascular lesions has been recognized as a key component of the inflammatory response associated with atherosclerosis, restenosis post-angioplasty, and graft atherosclerosis after coronary artery bypass. Understanding the molecular mechanisms that regulate arterial cell proliferation is therefore essential for the development of new tools for the treatment of these diseases. Mammalian cell proliferation is controlled by a large number of proteins that modulate the mitotic cell cycle, including cyclin-dependent kinases, cyclins, and tumour suppressors. The purpose of this review is to summarize current knowledge about the role of these cell cycle regulators in the development of native and graft atherosclerosis that has arisen from animal studies, histological examination of specimens from human patients, and genetic studies.

Reduction of ICAM-1 and LFA-1-positive leukocytes in the perivascular space of arteries under mycophenolate mofetil therapy reduces rat heart transplant vasculopathy

BACKGROUND

The interaction of lymphocyte function-associated antigen-1 (LFA-1)-positive host leukocytes with intercellular adhesion molecule-1 (ICAM-1) on graft endothelium may play a key role in allograft recognition, triggering the development of transplant vasculopathy (TVP). We investigated the correlation between TVP and ICAM-1 expression and accumulation of LFA-1-positive leukocytes in the perivascular space (PVS) of arteries under different immunosuppressive drugs.

METHODS

After cardiac transplantation (Lewis to Fisher) animals were randomized 4 groups: cyclosporine (CsA), 3 mg/kg/day (n=74); mycophenolate mofetil (MMF), 40 mg/kg/day (n=96); FK 506, 0.3 mg/kg/day (n=96); and control, no therapy (n=74). Three or 4 animals from each group were harvested at intervals of 1 to 4 days within the study period of 60 days. Using immunohistochemistry, LFA-1-positive leukocytes were analyzed in intra- and epicardial arteries. ICAM-1 expression was scored histologically. TVP was assessed by digitizing morphometry and expressed as mean vascular occlusion.

RESULTS

Accumulation of LFA-1-positive leukocytes in the PVS of arteries and the myocardium correlated with expression of ICAM-1 on graft endothelium. The severity of TVP in arteries correlated with the accumulation of LFA-1-positive leukocytes in PVS. All immunosuppressive drugs significantly reduced ICAM-1 expression, LFA-1 accumulation and extent of TVP, compared with controls. In MMF-treated animals, we also found a significant reduction of ICAM-1 expression, LFA-1 accumulation and extent of TVP compared with the groups treated with CsA and FK 506 (p <0.005).

CONCLUSION

These data support an essential role of LFA-1/ICAM-1 interaction in the genesis of TVP that may be abrogated, especially by the use of MMF.

Origin and course of the coronary arteries in normal mice and in iv/iv mice

This paper reports on the origin and distribution of the coronary arteries in normal mice and in mice of the iv/iv strain, which show situs inversus and heterotaxia. The coronary arteries were studied by direct observation of the aortic sinuses with the scanning electron microscope, and by examination of vascular corrosion casts. In the normal mouse, the left and right coronaries (LC, RC) arise from the respective Valsalva sinus and course along the ventricular borders to reach the heart apex. Along this course the coronary arteries give off small branches at perpendicular or acute angles to supply the ventricles. The ventricular septum is supplied by the septal artery, which arises as a main branch from the right coronary. Conus arteries arise from the main coronary trunks, from the septal artery and/or directly from the Valsalva sinus. The vascular casts demonstrate the presence of intercoronary anastomoses. The origin of the coronary arteries was found to be abnormal in 84% of the iv/iv mice. These anomalies included double origin, high take-off, slit-like openings and the presence of a single coronary orifice. These anomalies occurred singly or in any combination, and were independent of heart situs. The septal artery originated from RC in most cases of situs solitus but originated predominantly from LC in situs inversus hearts. Except for this anomalous origin no statistical correlation was found between the coronary anomalies and heart situs or a particular mode of heterotaxia. The coronary anomalies observed in the iv/iv mice are similar to those found in human hearts. Most coronary anomalies appear to be due to defective connections between the aortic root and the developing coronaries. iv/iv mice may therefore constitute a good model to study the development of similar anomalies in the human heart.

Recent developments in gene therapy for cardiac disease

Cardiovascular[TRACE;del] disease is the leading cause of death in the US and world-wide. Advances in molecular biology and the human genome project have revealed opportunities for novel strategies for cardiac gene therapy. This review discusses general and specific aspects of gene transfer strategies in cardiac tissues. These include 1) the selection and/or optimization of the vector for gene transfer; 2) the identification of the target gene(s); 3) the use of cardiac-specific promoters; and 4) the use of an appropriate delivery system for administration. Currently, several vectors (e.g., viral and nonviral vectors) have been developed and many target genes have been identified (e.g., VEGF, FGF, beta-AR, etc.). Many investigations have provided experimental models for gene delivery systems but the most efficient cardiac gene transfer was obtained from intramyocardial injection or perfusion of explanted myocardium. The data available thus far have suggested favorable immediate effects following gene transfer, but long-term value of cardiac gene therapy has not been proven. Further refinements in appropriate vectors that provide cell or tissue selectivity and long-lasting effects are necessary as well as the development of minimally invasive procedures for gene transfer.