Morphometric analysis of EM48-positive inclusions/aggregates shows age-dependent differences.

<p>Young (3 week) and old (15 month) rats received a stereotaxic injection of lentiviral vectors encoding Htt171-82Q (2 µl, 200 ng/µl of p24) into the striatum. Histological evaluation was carried out 4 weeks after infection using EM48 immunohistochemistry and image analysis software. The number of EM48 positive objects was computed for 25 bins (steps of 4 µm²) based on cross-sectional area. <i>A</i>, typical individual distribution of object size is shown for 3 young rats (#1 to #3) and 3 old rats (#1 to #3). Note that the proportion of small aggregates (grey vertical bar) is higher in old animals than in young rats. <i>B</i>, the averaged distribution of small aggregates is shown for the two experimental groups (n = 6 per group). Note the clear cut augmentation of the number of aggregates with an apparent cross-sectional area in the 4–20 µm² range in older rats. Note also that the distribution peak of EM48 positive objects in the 40–60 µm² range was shifted to the left in older rats (∼46 µm²) as compared to young animals (∼58 µm²). A similar shift was found in all animals, consistent with a decreased nuclear inclusion size. Results are expressed as mean+/−SEM. *p<0.05, ANOVA and Bonferroni's <i>post hoc</i> test.