The use of transformed Escherichia coli for experimental angiogenesis induced by regulated in situ production of vascular endothelial growth factor--an alternative gene therapy.
Defects in angiogenesis (blood vessel formation) are responsible for two most important causes of death in developed countries (ischemic heart disease and cancer). Vascular endothelial growth factor (VEGF) plays a pivotal role in physiological and pathological regulation of angiogenesis. In the last years several studies have indicated the possibilities of VEGF in the therapy of ischemic heart disease. However, especially VEGF gene therapy (naked DNA, plasmids and adenovirus mediated) is associated with adverse side effects regarding the expression regulation. To prepare bacterial strains producing VEGF using plasmids containing the VEGF cDNA for the use in experimental angiogenesis. Escherichia coli strain BL21(DE3) was transformed with Bluescript vector containing the inserts with cDNA sequences coding VEGF-A isoforms (VEGF121, VEGF164, VEGF189). Selection of recombinants was achieved by cultivating E. coli cells on ampicillin-added medium. The expression of target genes in the T7 expression system was induced by isopropyl-beta-D-thiogalactoside (IPTG). Polyacrylamide gel electrophoresis of the cell lysates showed the presence of polypeptides of molecular weight corresponding with known values of VEGF isoforms. Blood vessel formation induced by bacterial VEGF production was proved in vivo in mice seven days after intraperitoneal injection of transformed bacteria by light microscopy. CONCLUSION AND HYPOTHESIS: In summary, E. coli strain expressing VEGF was prepared and its biological effect confirmed. Bacteria, which produce angiogenic factors, provide a new modality for experimental angiogenesis and may be also suitable for clinical use. The in situ production of therapeutic proteins using optimalized prokaryotic expression systems can represent a useful tool for treatment based on molecular biomedicine. The main advantage of the described approach lies in the enhanced regulation control--bacterial expression can be regulated positively (induction by exogenous low molecular weight agents) and negatively (application of antibiotics). The hypothesis of alternative gene therapy should be proved in further studies.