Role of thymulin on the somatotropic axis in vivo.

AIMS: There is clear evidence for the existence of a bi-directional thymus-somatotropic axis and several studies suggest that the thymic peptide thymulin may be involved in this communication. We undertook to assess the impact of serum thymulin immunoneutralization in C57BL/6 mice and that of neonatal thymulin gene therapy (NTGT) in nude mice on body weight (BW) gain and on the histomorphometric profile of the somatotrope population. MAIN METHODS: Immunoneutralization of thymulin was done from postnatal day 1 to 35 by i.p. injections of rabbit anti-thymulin serum (α-FTS) and normal rabbit serum (NRS) in controls. NTGT was implemented in nudes using an adenoviral vector expressing a synthetic gene for thymulin (RAd-FTS). On postnatal day 1, heterozygous (nu/+) and homozygous (nu/nu) pups received a single bilateral i.m. injection either RAd-FTS or RAd-GFP (a control vector expressing green fluorescent protein). BW gain was recorded and at the end of the study the pituitaries were immunostained for growth hormone (GH). Serum GH and thymulin were determined by radioimmunoassay and bioassay, respectively. KEY FINDINGS: Thymulin immunoneutralization induced a significant decrease in BW gain, serum GH and somatotrope cell density as well as an increase in somatotrope cell size. NTGT markedly increased BW gain, serum thymulin (P<0.01) and somatotrope cell and volume density in nu/nu mice. SIGNIFICANCE: Our results suggest that thymulin plays a relevant physiological role on the thymus-somatotropic axis in mice.

Morphological changes induced by insulin-like growth factor-I gene therapy in pituitary cell populations in experimental prolactinomas.

In previous studies, we assessed the effects of intrapituitary injection of a recombinant adenoviral vector (RAd) harboring the cDNA for rat insulin-like growth factor type I (RAd-IGF-I) on the lactotrope and somatotrope populations in estrogen-induced prolactinomas. In the present study, we aimed to confirm these findings and further analyze the effect of transgenic RAd-IGF-I on the other pituitary cell populations in female rats. All animals except the intact group (no estrogen and no stereotaxic injection) received subcutaneous estrogen for 30 days, and the groups which received RAd-IGF-I or RAd expressing green fluorescent protein (control) were additionally treated with the appropriate vectors on experimental day 0. The RAd-IGF-I group showed a significant decrease in serum growth hormone and prolactin levels and lactotrope and somatotrope cell size induced by estrogen treatment. Cell density was not affected by 7 days of IGF-I gene therapy. Estrogen had an inhibitory effect on thyrotrope cell density, whereas with RAd-IGF-I there was a nonsignificant trend towards restoration of cell density, without changes in cell size. RAd-IGF-I treatment decreased corticotrope cell size without changing cell density. Estrogen decreased gonadotrope cell size and density, which was reversed by RAd-IGF-I. We conclude that in estrogen-induced pituitary tumors, IGF-I gene therapy has inhibitory effects on the lactotrope, somatotrope and corticotrope populations, while reversing the effect of estrogen on gonadotropic cells.

Effect of insulin-like growth factor-I gene therapy on the somatotropic axis in experimental prolactinomas.

Insulin-like growth factor-I (IGF-I) provides a physiologic feedback effect within the somatotropic axis. Gene therapy was implemented in young female Sprague-Dawley rats which received 2 pituitary stereotaxic injections of a control recombinant adenoviral vector expressing green fluorescent protein (RAd-GFP) or IGF-I (RAd-IGF-I). The animals were sacrificed 7 days after injection. Previously, on day -23, the experimental groups received subcutaneous implants of 17-beta estradiol. Morphometric analysis revealed that the somatotrope cells in estrogen-treated rats without stereotaxic injections showed a significant (p < 0.01) increase in the cell size compared with intact controls (59.9 +/- 1.1 vs. 42.9 +/- 1.2 microm(2)) and had a significant (p < 0.05) decrease in cell density with respect to intact animals (10.5 +/- 0.1 vs. 19.7 +/- 1.7). The treatment of pituitary adenomas with RAd-IGF-I induced a significant (p < 0.05) decrease in cell size with respect to E(2) + RAd-GFP (51.3 +/- 0.3 vs. 58.9 +/- 0.3 microm(2)) and no changes in cell density compared with RAd-GFP-injected animals (12.8 +/- 1.7 vs. 10.5 +/- 0.1). Serum growth hormone was higher (p < 0.01) in estrogen-treated animals versus controls (146.7 +/- 6 vs. 73.9 +/- 9 ng/ml). In rats carrying estrogen-induced adenomas, RAd-IGF-I injection induced a significant (p < 0.05) decrease in serum growth hormone compared to RAd-GFP-injected animals (107.5 +/- 7 vs. 142.4 +/- 9 ng/ml). IGF-I gene therapy appears to be an effective approach for the treatment of experimental somatomammotropic pituitary tumors and could be potentially useful as an adjuvant of conventional therapies.

Insulin-like growth factor-I gene therapy reverses morphologic changes and reduces hyperprolactinemia in experimental rat prolactinomas.

BACKGROUND: The implementation of gene therapy for the treatment of pituitary tumors emerges as a promising complement to surgery and may have distinct advantages over radiotherapy for this type of tumors. Up to now, suicide gene therapy has been the main experimental approach explored to treat experimental pituitary tumors. In the present study we assessed the effectiveness of insulin-like growth factor I (IGF-I) gene therapy for the treatment of estrogen-induced prolactinomas in rats. RESULTS: Female Sprague Dawley rats were subcutaneously implanted with silastic capsules filled with 17-beta estradiol (E2) in order to induce pituitary prolactinomas. Blood samples were taken at regular intervals in order to measure serum prolactin (PRL). As expected, serum PRL increased progressively and 23 days after implanting the E2 capsules (Experimental day 0), circulating PRL had undergone a 3-4 fold increase. On Experimental day 0 part of the E2-implanted animals received a bilateral intrapituitary injection of either an adenoviral vector expressing the gene for rat IGF-I (RAd-IGFI), or a vector (RAd-GFP) expressing the gene for green fluorescent protein (GFP). Seven days post vector injection all animals were sacrificed and their pituitaries morphometrically analyzed to evaluate changes in the lactotroph population. RAd-IGFI but not RAd-GFP, induced a significant fall in serum PRL. Furthermore, RAd-IGFI but not RAd-GFP significantly reversed the increase in lactotroph size (CS) and volume density (VD) induced by E2 treatment. CONCLUSION: We conclude that IGF-I gene therapy constitutes a potentially useful intervention for the treatment of prolactinomas and that bioactive peptide gene delivery may open novel therapeutic avenues for the treatment of pituitary tumors.

Estructura y ultraestructura del pancreas endocrino de ratones transgenicos diabeticos / Structure and ultrastructure of the endocrine pancreas in diabetic transgenic mice

El objetivo del trabajo fue corroborar los cambios estructurales y determinar las alteraciones ultraesctructurales ocurridas en el páncreas endocrino de ratones con un síndrome inducido de diabetes mellitus insulinodependiente (DMID). Para ello se utilizaron ratones transgénicos (OVE 27) que sobreexpresan el gen de calmodulina en las células beta del páncreas endocrino; en estos animales, el aumento de calmodulina disminuye los niveles de calcio citosólico de las células beta, produciendo alteraciones morfológicas y funcionales que desencadenan una DMID de curso severo. Para nuestro estudio se obtuvieron y procesaron porciones del páncreas (cola) de 4 ratones transgénicos machos diabéticos de 5 semanas de edad (glucemia: 376 + 2 mg/del) y de 4 controles no transgénicos de la misma cepa, sexo y edad (glucemia: 113 + 13 mg/dl). El estudio inmunohistoqu­mico con microscop­a de luz confirmó que los ratones transgénicos presentan una disminución del número y tama o de los islotes con distorsión de su arquitectura, sin respuesta inflamatoria asociada. Los estudios ultraestructurales demostraron diversos grados de da o en las células Beta, tales como la presencia de interdigitaciones de membrana y alteraciones de sus organelas y de sus gránulos de secreción. Estos hallazgos coinciden con el deterioro cuantitativo y funcional de las células beta y la conservación de las problaciones celulares no-beta de los islotes. Estos cambios ultraestructurales en las células beta del páncreas del modelo experimental estudiado, sumados a las alteraciones inmunohistoquímicas previamente descriptas, contribuyen a explicar la manifestación de la diabetes.

Estructura y ultraestructura del pancreas endocrino de ratones transgenicos diabeticos / Structure and ultrastructure of the endocrine pancreas in diabetic transgenic mice

El objetivo del trabajo fue corroborar los cambios estructurales y determinar las alteraciones ultraesctructurales ocurridas en el páncreas endocrino de ratones con un síndrome inducido de diabetes mellitus insulinodependiente (DMID). Para ello se utilizaron ratones transgénicos (OVE 27) que sobreexpresan el gen de calmodulina en las células beta del páncreas endocrino; en estos animales, el aumento de calmodulina disminuye los niveles de calcio citosólico de las células beta, produciendo alteraciones morfológicas y funcionales que desencadenan una DMID de curso severo. Para nuestro estudio se obtuvieron y procesaron porciones del páncreas (cola) de 4 ratones transgénicos machos diabéticos de 5 semanas de edad (glucemia: 376 + 2 mg/del) y de 4 controles no transgénicos de la misma cepa, sexo y edad (glucemia: 113 + 13 mg/dl). El estudio inmunohistoquímico con microscopía de luz confirmó que los ratones transgénicos presentan una disminución del número y tama o de los islotes con distorsión de su arquitectura, sin respuesta inflamatoria asociada. Los estudios ultraestructurales demostraron diversos grados de da o en las células Beta, tales como la presencia de interdigitaciones de membrana y alteraciones de sus organelas y de sus gránulos de secreción. Estos hallazgos coinciden con el deterioro cuantitativo y funcional de las células beta y la conservación de las problaciones celulares no-beta de los islotes. Estos cambios ultraestructurales en las células beta del páncreas del modelo experimental estudiado, sumados a las alteraciones inmunohistoquímicas previamente descriptas, contribuyen a explicar la manifestación de la diabetes. (AU)