MERKEL COMPLEXES OF HUMAN DIGITAL SKIN - 3-DIMENSIONAL IMAGING WITH CONFOCAL LASER MICROSCOPY AND DOUBLE IMMUNOFLUORESCENCE

Three-dimensional (3-D) reconstruction of images provided by confocal scanning laser microscopy (CSLM) is a powerful tool in a morpho-functi onal approach to cutaneous innervation studies. To investigate mechano receptors in the hand, a study of Merkel complexes was performed in hu man finger. A double fluorescent-conjugated immunolabeling with antibo dies against neurofilament (NF 200) and cytokeratin (CK 20) on floatin g, thick cutaneous samples (80 to 100 mu m), was used. After acquisiti on of serial optical planes by CSLM, reconstruction was performed with 3-D reconstruction software tools. Merkel cells were clearly labeled with CK 20, whereas nerve components were only NF 200 reactive. The ce lls, localized on the basal lamina of the epidermis, were usually arra nged in clusters of five to eight cells. Each cell was connected to a nerve process ramification originating from a unique fiber. Quantitati ve data, compiled from a sample of 25 Merkel complexes, gave a mean ce ll diameter of 13 +/- 1 mu m and a mean nerve fiber size of 3 +/- 1 mu m. Surface measurements were done on a single reconstructed cluster w ith a mean and standard error which only refers to the optical 3-D res olution. It gives a surface of 12 +/- 1 mu m(2) for the contact zone b etween cell and nerve fiber and a cluster area of about 500 mu m(2). T he great precision of reconstructed images provides a detailed analysi s of spatial relationships between abutting nerve fibers and Merkel ce lls. Data interpretation is improved with complementary ultrastructura l and physiological studies results, and this allows an accurate inves tigation of cutaneous sensory endings. J. Comp. Neurol. 398:98-104, 19 98. (C) 1998 Wiley-Liss, Inc.