RESUMO
During embryonal development, neuronal death occurs only by apoptosis and not by necrosis. Apoptotic neuronal loss may be responsible for altered brain development associated with prematurity and perinatal insults. Neurotrophic factors such as brian-derived neurotrophic factor [BDNF], and neurotrophin 3 [NT3] play crucial roles in protecting neurons form entering or progressing along an apoptotic pathway. The aim of this work was to measure BDNF and NT3 level at different gestational ages in human umbilical cord blood. In addition, we searched for differences in BDNF and NT3 levels in the presence or absence of factors that may affect intrauterine conditions and thus neurodevelopmental outcome. We collected 80 samples of cord blood and categorized them accordingly into three gestational age groups: group 1 [24-30 weeks], group 2 [31-36 weeks], and group 3 [37-42 weeks]. BDNF and NT3 levels were determined by ELISA. The BDNF levels were 798.3 +/- 492.5, 1401 +/- 650.8, and 2236.6 +/- 376.8 pg/ml in group 1, group 2, and group 3, respectively, with a significant difference between the 3 groups [p=0.0001]. In contrast, NT3 levels did not show significant change across gestational ages [p=0.2]. NT3 levels also did not correlate with BDNF levels across gestational ages [r=0.23; p=0.27]. The presence of premature rupture of membranes, chorioamnionitis, pregnancy-induced hypertension, or small for gestational age did not alter either BDNF or NT3 levels significantly. BDNF and NT3 levels were significantly higher in samples from subjects whose mothers received two doses of antenatal steroids compared with those who received only one dose of steroids, and those with no antenatal steroids[p=0.001, and p=0.04]. Cord blood levels of BDNF may reflect the degree of neutral maturity in premature infants. Increased BDNF and NT3 levels may also mediate improved neurodevelopment outcome in infants who received antenatal steroids