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Fisiología espermática, fragmentación del ADN y niveles de expresión génica de Prm1, Prm2, Tnp1 y Tnp2 en relación a la edad en ratones

By Jonathan Humberto Vásquez Cavero

Abstract

--- Age has an influence in the proper packaging of sperm chromatin, rendering it more vulnerable as time goes on. Protamines are the most abundant nuclear proteins in the mature spermatozoon and they are responsible for packing the paternal genome inside the sperm cell nucleus, making it inaccessible to nucleases or mutagens, thus protecting it. Mice with only one copy of these genes are infertile, which proves that are essential for normal spermatic function. The aim of this study was to look for a correlation between male age and sperm protamination at molecular and physiological levels. Male mice (Mus musculus Linnaeus, 1758) from C57BLACK6 (C57BL6) strain (20-25g) were used and distributed in two age groups: 3-4 month old mice ("Young" group: G1) and 18-21 month old ("Elderly" group: G2). Spermatozoa obtained from the epididymis tail were employed in sperm motility analysis, DNA fragmentation analysis by bidimensional comet assay, and oxidative stress by TBARS assay. Testicular tissue was used for assess the gene expression of Prm1, Prm2, Tnp1 and Tnp2, by real time PCR (RT-qPCR). When analyzing sperm motility, MOT (50.63 ± 6.60% vs 30.38 ± 5.16 %) and MR (24.50 ± 3.04 % vs 13.92 ± 3.02 %) were higher in G1 compared to G2 (p0.05). The proportion of sperm cells with fragmented DNA were not significantly different (G1 vs G2, 20.51 ± 1.41 % vs 20.11 ± 1.29 % respectively, p>0.05) and there were also no differences in the percentage of fragmented DNA of those subpopulations (17.36 ± 0.49 % vs 17.76 ± 0.62 %, p>0.05). Gene expression levels of Prm2 and Tnp1 were significantly overexpressed in G2 in comparison to G1 (p0.05). Tampoco se observaron diferencias significativas en la proporción de espermatozoides con ADN fragmentado entre los grupos G1 y G2 (20.51 ± 1.41 % vs 20.11 ± 1.29 %, p>0.05), ni en la cantidad de ADN fragmentado por espermatozoide entre ambos grupos (17.36 ± 0.49 % vs 17.76 ± 0.62 %, p>0.05). La comparación de los niveles de expresión de los genes Prm1, Prm2, Tnp1 y Tnp2 demostró que Prm2 y Tnp1 en el G2 se sobreexpresan observándose una diferencia significativa respecto al G1 (p0.05). Si bien el aumento de la edad presentó diferencias significativas con los niveles de expresión Prm2 y Tnp1, esto no sería suficiente para ejercer algún impacto sobre la producción de ROS y el aumento de la fragmentación del ADN espermático, debido quizás al papel protagónico de Prm1 en la protaminación espermática reportado en todas las especies estudiadas hasta la fecha y cuyos niveles de expresión no son alterados en el grupo de ratones viejos. Se concluye que el incremento de la edad no altera la protaminación espermática en ratones

Topics: Ratones como animales de laboratorio, Espermatogénesis en animales
Publisher: 'Universidad Nacional Mayor de San Marcos, Vicerectorado de Investigacion'
Year: 2012
OAI identifier: oai:renati.sunedu.gob.pe:sunedu/881622
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