Resumo

Lipofuscin granules (LG) are known as age pigments because display a progressive constant increase with age in the cytoplasm of mammalians neurons. The LG are autofluorescent organelles originated from lysosomes containing hydrolytic enzymes. Studies of LG using electron microscopy (EM) have revealed an electron-lucent lipid and an electron-dense protein component, both within a single membrane. Among the cells of the cerebral cortex, the pyramidal ones seem to present the highest rate of these lipopigments accumulation. The aim of this work is to study the LG number and characteristics from neurons of human temporal cortex from individuals on different ages. The human temporal cortex samples were collected during lobotomy surgeries on patients with temporal lobe epilepsy. The samples were divided on three groups based on the subjects age: group A: 20-28 years old (n = 4), group B: 37-41 years old (n = 5) and group C: 50-55 years old (n = 5). The ratio between the LG area per soma neuronal area was estimated using Sudan Black staining (3 sections per sample - 150 cells per section) on light microscopy (LM) observation. On EM (20 cells per sample, n = 2), we are analyzing the number of LG, the ratio between the LG area by area of soma cytoplasm, and the relative lipid and protein portions of the LG in relation of each granule area. The data were analyzed by one way ANOVA followed by the post hoc test of Tukey. The LM analysis revealed that the ratio between the LG area per soma neuronal area was higher in older subjects. There were statistical differences between groups A (average of µm2 ± SD; 3.16 ± 0.73) and B (4.33 ± 0.96; p=0.009), and between groups B and C (8.21 ± 2.94; p = 0.009). The EM analysis showed no differences in the total number of LG. However, group A (23 ± 4.95) presented higher value on the LG/soma neuroplasm area when compared to B (57 ± 3.53) and C (66 ± 2.82; p = 0.003). There are differences on the proportion lipid or protein/LG on each granule depending of the subjects age, with higher proportion of lipids on the older ones (p = 0,010). The data obtained on LM are consistent with several studies that observed an increase of LG with age. Considering that the size of LG was higher in older individuals, it might be possible that the increase of LG along aging is related to the lipid accumulation in these granules.