Growth Factor Expression in Atherosclerosis and Gene Transfer for Therapeutic Angiogenesis

Atherosclerosis and its ischemic symptoms are the leading causes of illness and deaths in Western countries. Patients with cardiovascular diseases are increasingly older and have multiple other comorbidities which limit the use of conventional treatments. Therapeutic gene transfer with proangiogenic factors may offer new treatment opportunities for these patients. In this study, therapeutic potency of vascular endothelial growth factors (VEGFs) and closely related platelet derived growth factors (PDGFs) were studied. In the first study, we found that PDGF-C was strongly expressed in the endothelium and lesion macrophages while PDGF-D expression was more diffuse in the vessel wall in human atherosclerotic lesions. Next, therapeutic angiogenesis was studied in rabbit hindlimb ischemia model and in mouse myocardium using adenoviral (Ad) gene delivery for short-term and adeno-associated virus (AAV) for long-term gene expression, respectively. We observed that the combination gene transfer of AdVEGF-A and AdPDGF-B enhanced the proliferation of pericytes but that did not lead to the stabilization of newly formed blood vessels. However, the combination gene transfer prolonged the angiogenic effect. Thirdly, AAV-VEGF-A was found to induce a 10-fold perfusion increase compared to AAV-LacZ in rabbit hindlimb. Perfusion was followed for up to one year using a high resolution ultrasound method. In comparison, AdVEGF-A gene transfer increased muscle perfusion by 20-fold but that returned back to baseline in two weeks. As a side effect of long-term VEGF-A expression, we observed remarkable histological disorganization of AAV-VEGF-A transduced skeletal muscle. Finally, as a potential novel proangiogenic gene therapy, the effects of two hypoxia inducible transcription factors (HIFs), HIF-1α and -2α, on angiogenesis and tissue energy metabolism were studied in ischemic rabbit hindlimb. Gene transfer of AdHIF-1α and AdHIF-2α were found to increase skeletal muscle perfusion by 4-fold compared to AdLacZ control. In addition, we observed that HIF gene transfer enhanced the recovery of ischemic skeletal muscle from the energy loss induced by exercise evaluated using magnetic resonance spectroscopy (MRS). In summary, the potential of vascular growth factors, transcription factors and different viral gene delivery vectors in proangiogenic gene therapy were studied. Enhancing angiogenesis together with improved exercise tolerance by gene therapy is a promising new treatment strategy for the patients suffering from impaired vascular function. The expression time and intensity can be controlled by choosing optimal therapeutic genes and viral vectors for a certain treatment application. National Library of Medicine Classification: QU 107, QY 60.L3, QY 60.R6, QZ 52, WG 550, WN 185, WN 208 Medical Subject Headings: Atherosclerosis/therapy; Gene Therapy; Gene Transfer Techniques; Gene Expression; Adenoviridae; Dependovirus; Blood Vessels; Disease Models, Animal; Rabbits; Mice; Endothelium, Vascular; Hindlimb; Myocardium; Transcription Factors; Hypoxia-Inducible Factor 1; Ischemia; Platelet-Derived Growth Factor/therapeutic use; Vascular Endothelial Growth Factors/therapeutic use; Magnetic Resonance Spectroscopy; Ultrasonography