P-12   THREE-DIMENSIONAL RECONSTRUCTION OF FOLLICULAR UNITS BY SERIAL HORIZONTAL SECTIONING

E. Poblet, F. Jimenez*, F. Ortega**. Depts. of Pathology, Hospital of Albacete; Dermatology, Clínica San Roque of Las Palmas*; and Dept. of Morphology University of Las Palmas of Gran Canaria**. Spain.

Background: Hair follicles are grouped and distributed in well-defined histologic structures known as follicular units (FU). A complete knowledge of the microanatomy of this structure is necessary in order to better understand its physiology and significance. Objective: To perform a three-dimensional reconstruction of the microscopic anatomy of the follicular units by analysing large and multiple serial horizontal tissue sections of scalp skin. Methods: Large (2 x 1 cm) tissue sections were obtained from human scalp samples and stained with hematoxylin and eosin and Masson´s trichrome. Sections were cut at intervals of 6 microns. Each section was numbered sequentially. The course of each unit was tracked down using serial horizontal sections from the upper infudibulum to the lower isthmus. Multiple digital photographs were taken from each section at a magnification (x100) that allowed us to observe the different structures of each unit (hair follicles, arrector muscles and sebaceous glands). Based on these digital photographs, a large mosaic photographic landscape of each section was obtained, and a three-dimensional reconstruction of the follicular units was finally composed using an imaging processor software. Results: Our results confirmed the distribution of the hairs in a pattern already described in the literature. However, the serial analysis of large areas allowed us to demonstrate that at a certain point of the isthmus level the arrector pili muscles forms a muscular unit, which is located at one pole of the FU. Conclusions: Our method of serial horizontal sectioning of large samples allowed us to achieve a more realistic three dimensional microanatomy of the follicular unit. A new vision of the interaction between the arrector pili muscles and the hair follicles is proposed. This new model suggests that the arrector pili muscles may play a role in maintaining the integrity of the follicular unit as well as in sebum secretion.