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LIMA, E.R. Optimization of in vivo transfer parameters of the growth hormone gene aiming at the phenotypic correction of dwarf mice, Dissertação (Mestrado) Instituto de Pesquisas Energéticas e Nucleares, Universidade de São Paulo, São Paulo, 2016. Growth hormone deficiency (GHD) is conventionally treated with repeated injections of the recombinant hormone. This work aimed at establishing an alternative treatment based on the transfer of the human (hGH) or mouse growth hormone (mGH) genes into lit/lit or lit/scid dwarf mice, using plasmid DNA administration associated with electrotransfer, in order to achieve the maximum growth recovery compared to normal mice (catch-up growth). Administration of the plasmid containing the mGH gene was first carried out in the exposed quadriceps or non-exposed anterior tibialis (TA) muscle. Using different electrotransfer conditions, based on alternate pulses of high (1000 V/cm) and low (100 V/cm) voltage (HV/LV, HV/8LV) or consecutive pulses of low voltage (8 pulses of 150 V/cm), the TA muscle in the HV/LV condition showed the highest levels of mGH expression: 6.7 ± 2.5 ng/mL. Exposure time and amount of the enzyme hyaluronidase (HI) required for electrotransfer were also analyzed. The time of 30 minutes and the dose of 20 U HI provided the best results of expression. Different amounts of DNA were also tested, but the administration of 50 μg DNA/animal was confirmed as the best. In the optimization of the volume of plasmid solution administered to TA, it was observed that injection of 20 μL of DNA showed a significantly higher expression of the protein compared with 10 μL. Aiming at a higher GH expression, an experiment was carried out by adding poly-L-glutamate to the DNA diluent, comparing also different electrotransfer conditions (HV/LV and 375 V/cm). The condition of 375 V/cm, without the polymer addition, provided the higher concentrations of both hGH and mGH in the serum of lit/scid or lit/lit mice, respectively. Using 3 pulses of 375 V/cm and administration of mGH-DNA in two locations on each TA muscle, the highest expression levels of up to 14.7 ± 3.7 ng mGH/mL were obtained. These were the parameters utilized in a bioassay, which was also carried out by measurement of the initial and final femur length by radiography. In this 36-day bioassay, the growth curve of treated lit/lit mice was similar to that of heterozygous untreated mice and the mGH levels of DNA group were significantly higher (P<0.0002) than the control group. Treated mice also showed a higher mIGF-I concentration in the serum compared to the control group. Concerning growth parameters, DNA-treated group showed percentages of increase highly significant compared to the control group, with P<0.001 for body weight and P<0.002 for body, tail and both femurs lengths, with catch-up values of the order of 79% for femur lengths. We can conclude that an efficient non-viral gene transfer methodology has been established, which lead to a complete growth normalization of the dwarf mice through the use of younger animals, as reported in the literature and in a recent paper of our group.

Otimização de parâmetros de transferência &lt;i&gt;in vivo&lt;/i&gt; do gene do hormônio de crescimento visando a correção fenotípica de camundongos anões