Optimization of Mouse Growth Hormone Plasmid DNA Electrotransfer into Tibialis Cranialis Muscle of "Little" Mice.

Previous non-viral gene therapy was directed towards two animal models of dwarfism: Immunodeficient (lit/scid) and immunocompetent (lit/lit) dwarf mice. The former, based on hGH DNA administration into muscle, performed better, while the latter, a homologous model based on mGH DNA, was less efficient, though recommended as useful for pre-clinical assays. We have now improved the growth parameters aiming at a complete recovery of the lit/lit phenotype. Electrotransfer was based on three pulses of 375 V/cm of 25 ms each, after mGH-DNA administration into two sites of each non-exposed tibialis cranialis muscle. A 36-day bioassay, performed using 60-day old lit/lit mice, provided the highest GH circulatory levels we have ever obtained for GH non-viral gene therapy: 14.7 ± 3.7 ng mGH/mL. These levels, at the end of the experiment, were 8.5 ± 2.3 ng/mL, i.e., significantly higher than those of the positive control (4.5 ± 1.5 ng/mL). The catch-up growth reached 40.9% for body weight, 38.2% for body length and 82.6%-76.9% for femur length. The catch-up in terms of the mIGF-1 levels remained low, increasing from the previous value of 5.9% to the actual 8.5%. Although a complete phenotypic recovery was not obtained, it should be possible starting with much younger animals and/or increasing the number of injection sites.

Optimization of mouse growth hormone plasmid DNA electrotransfer into tibialis cranialis muscle of “little” mice

Previous non-viral gene therapy was directed towards two animal models of dwarfism: Immunodeficient (lit/scid) and immunocompetent (lit/lit) dwarf mice. The former, based on hGH DNA administration into muscle, performed better, while the latter, a homologous model based on mGH DNA, was less efficient, though recommended as useful for pre-clinical assays. We have now improved the growth parameters aiming at a complete recovery of the lit/lit phenotype. Electrotransfer was based on three pulses of 375 V/cm of 25 ms each, after mGH-DNA administration into two sites of each non-exposed tibialis cranialis muscle. A 36-day bioassay, performed using 60-day old lit/lit mice, provided the highest GH circulatory levels we have ever obtained for GH non-viral gene therapy: 14.7 ± 3.7 ng mGH/mL. These levels, at the end of the experiment, were 8.5 ± 2.3 ng/mL, i.e., significantly higher than those of the positive control (4.5 ± 1.5 ng/mL). The catch-up growth reached 40.9% for body weight, 38.2% for body length and 82.6%–76.9% for femur length. The catch-up in terms of the mIGF-1 levels remained low, increasing from the previous value of 5.9% to the actual 8.5%. Although a complete phenotypic recovery was not obtained, it should be possible starting with much younger animals and/or increasing the number of injection sites.

Brain STAT5 signaling modulates learning and memory formation.

The signal transducer and activator of transcription 5 (STAT5) is a transcription factor recruited by numerous cytokines. STAT5 is important for several physiological functions, including body and tissue growth, mammary gland development, immune system and lipid metabolism. However, the role of STAT5 signaling for brain functions is still poorly investigated, especially regarding cognitive aspects. Therefore, the objective of the present study was to investigate whether brain STAT5 signaling modulates learning and memory formation. For this purpose, brain-specific STAT5 knockout (STAT5 KO) mice were studied in well-established memory tests. Initially, we confirmed a robust reduction in STAT5a and STAT5b mRNA levels in different brain structures of STAT5 KO mice. STAT5 KO mice showed no significant alterations in metabolism, growth, somatotropic axis and spontaneous locomotor activity. In contrast, brain-specific STAT5 ablation impaired learning and memory formation in the novel object recognition, Barnes maze and contextual fear conditioning tests. To unravel possible mechanisms that might underlie the memory deficits of STAT5 KO mice, we assessed neurogenesis in the hippocampus, but no significant differences were observed between groups. On the other hand, reduced insulin-like growth factor-1 (IGF-1) mRNA expression was found in the hippocampus and hypothalamus of STAT5 KO mice. These findings collectively indicate that brain STAT5 signaling is required to attain normal learning and memory. Therefore, STAT5 is an important downstream cellular mechanism shared by several cytokines to regulate cognitive functions.

Partial correction of the dwarf phenotype by non-viral transfer of the growth hormone gene in mice: Treatment age is critical.

Non-viral transfer of the growth hormone gene to different muscles of immunodeficient dwarf (lit/scid) mice is under study with the objective of improving phenotypic correction via this particular gene therapy approach. Plasmid DNA was administered into the exposed quadriceps or non-exposed tibialis cranialis muscle of lit/scid mice followed by electroporation, monitoring several growth parameters. In a 6-month bioassay, 50µg DNA were injected three times into the quadriceps muscle of 80-day old mice. A 50% weight increase, with a catch-up growth of 21%, together with a 16% increase for nose-to-tail and tail lengths (catch-up=19-21%) and a 24-28% increase for femur length (catch-up=53-60%), were obtained. mIGF1 serum levels were ~7-fold higher than the basal levels for untreated mice, but still ~2-fold lower than in non-dwarf scid mice. Since treatment age was found to be particularly important in a second bioassay utilizing 40-day old mice, these pubertal mice were compared in a third bioassay with adult (80-day old) mice, all treated twice with 50µg DNA injected into each tibialis cranialis muscle, via a less invasive approach. mIGF1 concentrations at the same level as co-aged scid mice were obtained 15days after administration in pubertal mice. Catch-up growth, based on femur length (77%), nose-to-tail (36%) and tail length (39%) increases was 40 to 95% higher than those obtained upon treating adult mice. These data pave the way for the development of more effective pre-clinical assays in pubertal dwarf mice for the treatment of GH deficiency via plasmid-DNA muscular administration.

Mesenchymal Stem Cells as Therapeutic Candidates for Halting the Progression of Diabetic Nephropathy.

Mesenchymal stem cells (MSCs) possess pleiotropic properties that include immunomodulation, inhibition of apoptosis, fibrosis and oxidative stress, secretion of trophic factors, and enhancement of angiogenesis. These properties provide a broad spectrum for their potential in a wide range of injuries and diseases, including diabetic nephropathy (DN). MSCs are characterized by adherence to plastic, expression of the surface molecules CD73, CD90, and CD105 in the absence of CD34, CD45, HLA-DR, and CD14 or CD11b and CD79a or CD19 surface molecules, and multidifferentiation capacity in vitro. MSCs can be derived from many tissue sources, consistent with their broad, possibly ubiquitous distribution. This article reviews the existing literature and knowledge of MSC therapy in DN, as well as the most appropriate rodent models to verify the therapeutic potential of MSCs in DN setting. Some preclinical relevant studies are highlighted and new perspectives of combined therapies for decreasing DN progression are discussed. Hence, improved comprehension and interpretation of experimental data will accelerate the progress towards clinical trials that should assess the feasibility and safety of this therapeutic approach in humans. Therefore, MSC-based therapies may bring substantial benefit for patients suffering from DN.

A novel homologous model for gene therapy of dwarfism by non-viral transfer of the mouse growth hormone gene into immunocompetent dwarf mice.

The possibilities for non-viral GH gene therapy are studied in immunocompetent dwarf mice (lit/lit). As expression vector we used a plasmid previously employed in immunodeficient dwarf mice (pUBI-hGH-gDNA) by replacing the human GH gene with the genomic sequence of mouse-GH DNA (pUBI-mGH-gDNA). HEK-293 human cells transfected with pUBI-mGH-gDNA produced 3.0 µg mGH/10(6) cells/day compared to 3.7 µg hGH/10(6) cells/day for pUBIhGH- gDNA transfected cells. The weight of lit/lit mice treated with the same two plasmids (50 µg DNA/mouse) by electrotransfer into the quadriceps muscle was followed for 3 months. The weight increase up to 15 days for mGH, hGH and saline treated mice were 0.130, 0.112 and 0.027 g/mouse/day. Most sera from hGH-treated mice contained anti-hGH antibodies already on day 15, with the highest titers on day 45, while no significant anti-mGH antibodies were observed in mGH-treated mice. At the end of 3 months, the weight increase for mGH-treated mice was 34.3%, while the nose-to-tail and femur lengths increased 9.5% and 24.3%. Mouse-GH and hGH circulating levels were 4-5 ng/mL 15 days after treatment, versus control levels of ~0.7 ng GH/mL (P<0.001). In mGH-treated mice, mIGF-I determined on days 15, 45 and 94 were 1.5- to 3-fold higher than the control and 1.2- to 1.6-fold higher than hGH-treated mice. The described homologous model represents an important progress forming the basis for preclinical testing of non-viral gene therapy for GH deficiency.

Growth responses following a single intra-muscular hGH plasmid administration compared to daily injections of hGH in dwarf mice.

In previous work, sustained levels of circulating human growth hormone (hGH) and a highly significant weight increase were observed after electrotransfer of naked plasmid DNA (hGH-DNA) into the muscle of immunodeficient dwarf mice (lit/scid). In the present study, the efficacy of this in vivo gene therapy strategy is compared to daily injections (5 µg/twice a day) of recombinant hGH (r-hGH) protein, as assessed on the basis of several growth parameters. The slopes of the two growth curves were found to be similar (P > 0.05): 0.095 g/mouse/d for protein and 0.094 g/mouse/d for DNA injection. In contrast, the weight increases averaged 35.5% (P < 0.001) and 23.1% (P < 0.01) for protein and DNA administration, respectively, a difference possibly related to the electroporation methodology. The nose-to-tail linear growth increases were 15% and 9.6% for the protein and DNA treatments, respectively, but mouse insulin-like growth factor I (mIGF-I) showed a greater increase over the control with DNA (5- to 7-fold) than with protein (3- to 4-fold) administration. The weight increases of several organs and tissues (kidneys, spleen, liver, heart, quadriceps and gastrocnemius muscles) were 1.3- to 4.6-fold greater for protein than for DNA administration, which gave a generally more proportional growth. Glucose levels were apparently unaffected, suggesting the absence of effects on glucose tolerance. A gene transfer strategy based on a single hGH-DNA administration thus appears to be comparable to repeated hormone injections for promoting growth and may represent a feasible alternative for the treatment of growth hormone deficiency.

Long-term human growth hormone expression and partial phenotypic correction by plasmid-based gene therapy in an animal model of isolated growth hormone deficiency.

BACKGROUND: A model for in vivo gene therapy based on electroporation of human growth hormone (hGH)-coding naked DNA in the muscle of dwarf (lit/lit) and immunodeficient dwarf (lit/scid) mice is described. METHODS: A plasmid containing the ubiquitin C promoter and the genomic hGH sequence was administered to the exposed quadriceps muscle, followed by electrotransfer using eight 50-V pulses of 20 ms at a 0.5-s interval. Serum hGH levels were determined after various days of DNA administration and a long-term body weight gain experiment was carried out. RESULTS: Serum hGH, determined 3 days after DNA administration, revealed a significant dose-response curve (p < 0.01) in the 0-50 microg range. Because 50 microg of plasmid DNA produced circulating hGH levels of 2-3 ng/ml for at least 12 days, a long-term body weight gain assay was carried out. After 60 days, the weight of treated lit/scid mice increased 33.1% compared to a 4.2% weight decrease for the control group. hGH circulating levels were of the order of 1.5-3 ng/ml throughout the experiment and the average weight increase during the first 10 days was comparable to that obtained upon regular daily injection of 10 microg of recombinant hGH per mouse, producing comparable circulating levels of the hormone. A lower, but still significant increase in body weight was obtained upon repeating the experiment in immunocompetent dwarf mice (lit/lit). CONCLUSIONS: We report for the first time sustained levels of circulating hGH after intramuscular naked DNA administration and, consequently, a highly significant weight increase of dwarf 'little' mice.