Immunofluorescent microscopic investigation of the distal arrector pili: Ademonstration of the spatial relationship between alpha 5 beta 1 integrin and fibronectin

Currently there is limited knowledge regarding the anatomy of the distal ar rector pili (AP) muscle. A previous study implicated fibronectin and alpha 5 beta 1 integrin binding as the anchor between the AP and the extracellula r matrix (ECM). The purpose of this study was to strengthen this hypothesis . Serial frozen sections of human scalp skin were double-labeled via immuno fluorescent staining for alpha 5 beta 1 with fluorescein and fibronectin wi th rhodamine, followed by fluorescent microscopy. Granular staining for alp ha 5 beta 1 with fluorescein and smooth staining for fibronectin with rhoda mine were seen at the periphery of the AP muscle bundles and along the dist al fibers. Precise co-localization of alpha 5 beta 1 and fibronectin was ob served at the AP-ECM interface by means of a dual filter. Analysis of varia nce was used on the relative density of staining for each epitope. Staining for both epitopes was significantly brighter at the distal fibers than at the middle or proximal portions of the muscle. A computerized three-dimensi onal reconstruction provides a detailed picture of the microanatomy of the discal AP, which allows mathematical evaluation of the forces of contractio n The anatomic co-localization between alpha 5 beta 1 and fibronectin stren gthens our hypothesis that interaction of these epitopes mediates the attac hment of the distal AP to the ECM.