Human umbilical cord blood cells transfected with VEGF and L1CAM do not differentiate into neurons but transform into vascular endothelial cells and secrete neuro-trophic factors to support neuro-genesis—a novel approach in stem cell therapy

Genetically modified mono-nuclear cell fraction from human umbilical cord blood (HUCB) expressing human vascular endothelial growth factor (VEGF) and mouse neural L1 cell adhesion molecule (L1CAM) were used for gene-stem cell therapy of transgenic G93A mice adopted as an animal amyotrophic lateral sclerosis (ALS) model. We generated non-viral plasmid constructs, expressing human VEGF165 (pcDNA-VEGF) and mouse neural L1 cell adhesion molecule (pcDNA-mL1CAM). Mono-nuclear fraction of HUCB cells were transiently transfected by electro-poration with a mixture of expression plasmids (pcDNA-VEGF + pcDNA-mL1CAM). Sixteen transgenic female and male mice were randomly assigned to three groups: (1) transplantation of genetically modified HUCB cells expressing L1 and VEGF (n = 6), (2) transplantation of un-transfected HUCB cells (n = 5), and (3) control group (n = 5). In first two experimental groups 1 × 106 cells were injected retro-orbitally in pre-symptomatic 22–25-week-old G93A mice. Our results demonstrate that HUCB cells successfully grafted into nervous tissue of ALS mice and survived for over 3 months. Therefore, genetically modified HUCB cells migrate in the spinal cord parenchyma, proliferate, but instead of transforming into nerve cells, they differentiate into endothelial cells forming new blood vessels. We propose that: (A) expression of mouse neural L1CAM is responsible for increased homing and subsequent proliferation of transplanted cells at the site of neuro-degeneration, (B) expression of human VEGF directs HUCB cell differentiation into endothelial cells, and (C) neuro-protective effect may stem from the delivery of various neuro-trophic factors from newly formed blood vessels.