Three‐Dimensional Morphometry of the Cerebellum During Intrauterine Development in Sheep Using Unbiased Design‐Based Stereology

Sheep have been used as an ideal translational model for embryological studies of the central nervous system. The objective of the present study was to establish normal quantitative parameters for the cerebellum during intrauterine development in sheep, using unbiased design-based stereological methods. Twenty sheep embryos were divided into four gestational age groups (9-11, 12-14, 15-17 and 18-20 weeks of gestation). The orientator method was used to obtain isotropic, uniform and random sections. The fractional volume of white matter, grey matter and different layers was estimated by a point-counting system. The cerebellar surface area was estimated through the use of test lines. The total volume of the cerebellum increased from 0.1142 ± 0.02644 cm³ to 1.4717 ± 0.3558 cm³ during development. The volume of white matter increased from 0.0785 ± 0.02616 cm³ to 0.5316 ± 0.12677 cm³, and the volume of grey matter showed an increase from 0.0785 ± 0.02616 cm³ to 0.5316 ± 0.12677 cm³. The volume of the external granular, molecular and internal granular layers increased from 0.009 ± 0.00249 cm³, 0.0078 ± 0.00175 cm³, 0.0189 ± 0.00403 cm³ to 0.0942 ± 0.01986 cm³, 0.2311 ± 0.04582 cm³, 0.5367 ± 0.1666 cm³, respectively. The surface area of the cerebellum increased from 5.54 ± 1.75 cm² to 53 ± 11.6 cm². All aforementioned parameters showed a positive significant (p < 0.05) correlation with gestational age. The standard data of this research could be used as a reference for the accurate surveying of cerebellar development and also for practical applications in veterinary embryological neurology.