178. Early Treatment for Growth Hormone Deficiency Based on Naked DNA Administration in Dwarf Mice Allows Efficient Catch-Up Growth

Growth hormone deficiency (GHD) is the major disease of the pituitary gland and is characterized by significant changes in body composition, bone density, lipid metabolism amongst others. Current treatment consists of daily administration of recombinant human growth hormone. As an alternative, our group investigates a gene therapy strategy for GHD based on the administration of a plasmid encoding the human growth hormone gene (hGH) under the control of ubiquitin C promoter, followed by electrotransfer. In order to get the maximize phenotype correction and to compare treatment of pubertal relative to adult mice, a bioassay was performed using 40 or 80 days old lit/scid mice, respectively. The mice were injected with 50mg of plasmid DNA in each side of non-exposed tibialis cranialis muscle, followed by electrotransfer at high and low voltage pulses.At day 30, the treated groups showed a significant body weight variation of 3.64g/mice/day for pubertal mice, 2.07g/mice/day for the adult mice, and -0.01g/mice/day for the control group. View Large Image | Download PowerPoint SlideAfter 40 days, a second round of DNA administration was carried out, and as no significant body weight gain in the following days was observed, the assay was terminated at day 60. Remarkably, the parameters directly related to linear growth (table 1table 1), like increases in nose-to-tail, tail and femur lengths, were 1.2 – 2.0 fold higher for pubertal mice as compared to the adult group, and treatment of pubertal mice resulted in a striking catch-up growth of 36 to 77%.Table 1Parameters directly related to longitudinal growth after 60 days of hGH-DNA administration in 40 days or 80 days old mice lit/scid micenIncrease %Catch-up (%)Nose-to-tail length (cm)saline – 40 days411.6hGH-DNA – 40 days322.235.6untreated scid – 40 days49.0saline – 80 days42.9hGH-DNA – 80 days311.725.7untreated scid – 80 days511.2Tail lenght (cm)saline – 40 days413.1hGH-DNA – 40 days324.239.0untreated scid – 40 days45.8saline – 80 days41.0hGH-DNA – 80 days312.023.6untreated scid – 80 days511.3Femur lenght (mm)hGH-DNA – 40 days318.71177.5hGH-DNA – 80 days416.11139.91Calculated with basis on saline-treated co-aged miceMoreover mIGF-I, the main GH-dependent mediator of growth, was measured in plasma samples and the levels of mIGF-I in treated pubertal lit/scid mice were completely normalized 15 days post treatment and not significantly different to values for co-aged untreated non-dwarf mice, however the same did not occur to the adult lit/scid treated mice and their co-aged scid mice. These results are very promising and demonstrates the significance of early onset of gene therapy treatment in the lit/scid mouse model for phenotypic correction of GHD.