RESUMO
Cellular fate and gene expression patterns are modulated by different epigenetic factors including non-coding RNAs (ncRNAs) and chromatin organization. Both factors are dynamic throughout male germ cell differentiation on the seminiferous tubule, despite the transcriptional inactivation in the last stages of spermatogenesis. Sperm maturation during the caput-to-cauda transit on the epididymis involves changes in chromatin organization and the soma-to-germ line transference of ncRNAs that are essential to obtain a functional sperm for fertilization and embryo development. Here, the male environment (diseases, drugs, mental stress) is crucial to modulate these epigenetic factors throughout sperm maturation, affecting the corresponding offspring. Paternal transgenerational inheritance has been directly related to sperm epigenetic changes, most of them associated with variations in the ncRNA content and chromatin marks. Our aim is to give an overview about how epigenetics, focused on ncRNAs and chromatin, is pivotal to understand spermatogenesis and sperm maturation, and how the male environment impacts the sperm epigenome modulating the offspring gene expression pattern.
Assuntos
Humanos , Masculino , Cromatina/genética , Epigênese Genética/genética , Espermatogênese/genética , Expressão Gênica , Diferenciação CelularRESUMO
El estrés oxidativo es definido como un desbalance entre la producción de oxidantes y antioxidantes. La inducción de tolerancia a estrés en los ovocitos conllevaría a un mejor desarrollo embrionario. En bovinos, la incubación de ovocitos maduros con diferentes estresores (térmicos, alta presión hidrostática, oxidativos) incrementaría la tasa de generación de blastocitos. Este estudio evalúa el efecto de la modulación del estado redox incrementando el estrés oxidativo con H2O2 en ovocitos maduros bajo condiciones de cultivo in vitro y su efecto sobre el potencial de desarrollo embrionario. Para ello, ovocitos procedentes de ovarios de matadero fueron madurados en medio TCM-199 suplementado durante 2223 h, a 38,5 °C, 5 % CO2 y humedad a saturación. Al final de las 2223 h se incubaron los ovocitos maduros con 0, 50, 100 y 200 µM H2O2. La fecundación in vitro se realizó co-incubando los ovocitos durante 18 h con una concentración final de 1x106 espermatozoides/mL. Los presuntos cigotos fueron denudados y cultivados en medio KSOM-0,4 % BSA a 38,5 °C en atmósfera de baja tensión de O2 (5 % O2, 5 % CO2 y 90 % N2) y humedad a saturación. El estrés oxidativo inducido con H2O2 a una concentración de 50 y 100 µM produce una tasa de división de los embriones similar al control (88,7 %, 83,2 % y 86,4 % respectivamente, p>0,05), disminuyendo significativamente al utilizar una concentración de 200 µM (58,8 %, p<0,05). Asimismo, H2O2 causó un efecto similar en la tasa de blastocitos con 50 µM (20,4 % vs. 25,8 % control, p>0.05) pero disminuyó significativamente con 100 y 200 µM (10,7 % y 3,3 % respectivamente, p<0,05). Es posible, que estos embriones resistentes al estrés oxidativo puedan tener una mayor sobrevida durante los procesos de criopreservación que generan altos niveles de especies reactivas de oxígeno en los embriones.
Oxidative stress is defined as an imbalance between the production of oxidants and antioxidants. The induction of stress tolerance in oocytes leads to a better embryonic development. In cattle incubating mature oocytes with different stressors (thermal, high hydrostatic pressure, oxidative) increase the generation rate of blastocysts. The purpose of this study was to evaluate the effect of modulating the redox state increasing the oxidative stress through H2O2 in mature oocyte under in vitro culture conditions and its effect on the potential of embryonic development. To do this, oocytes from slaughterhouse ovaries were matured in TCM-199 medium supplemented for 2223 h at 38.5 °C, 5 % CO2 and humidified atmosphere. At the end of 2223 h, the treatments with 0, 50, 100 and 200 µM H2O2 were applied for 1 h. IVF was performed co-incubating the eggs for 18 h with a final concentration of 1x106 sperm/mL. The presumptive zygotes were denuded and cultured in medium KSOM-0.4 % BSA to 38.5 °C in an atmosphere of low concentration of O2 (5 % O2, 5 % CO2 and 90 % N2) and humidified atmosphere. The results show that the induction of oxidative stress by H2O2 produces a similar effect using a concentration of 50 and 100 mM in the cleavage rate of embryos compared to control (88.7 %, 83.2 % and 86,4 % respectively, p>0.05) and decreasing significantly by using a concentration of 200 mM (58.8 %, p<0.05). Also, H2O2 caused a similar effect on the rate of blastocysts with 50 µM (20.4 % vs. 25.8 control, p>0.05) but decreased significantly with 100 and 200 µM (10.7 % and 3.3 % respectively, p<0.05). It is possible that these embryos resistant to oxidative stress may have a higher survival in the cryopreservation processes that generating high levels of reactive oxygen species.