Three-Dimensional Fluorescent Image Analysis of Small Fiber Neuropathy in Human Skin Biopsies
Munch, Alexandra E.
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Diabetes and the resulting hyperglycemia give rise to a variety of somatosensory deficiencies, which lead to reduced cutaneous innervation in the extremities, namely small fiber neuropathy (SFN). SFN is characterized by the progressive loss of sensation in the hands and feet, which may be painful or asymptomatic. As a result, traditional physical exams are not sensitive enough to measure nerve fiber loss. The positive correlation between the presence of SFN and decreased intraepidermal nerve fiber (IENF) density in skin biopsy samples has been repeatedly documented and is the accepted measure for diagnosis. The standard diagnostic approach for quantifying this loss of innervation consists of manually counting IENFs crossing the dermal-epidermal border in 2D skin cross-sections. The present study introduces and validates a 3D volumetric approach for assessment of IENF loss in human skin biopsies using confocal immunofluorescence microscopy and the Imaris computer software for analyses. Skin samples were obtained from diabetic patients with confirmed neuropathy, diabetic patients without confirmed neuropathy and age-matched controls, and analyzed for both morphometric and morphologic changes. Our data support the hypothesis that this novel technique provides a more accurate and objective measurement of IENF density than the standard 2D counting procedure. The 3D digitalized analysis, which also allowed for exploration of morphologic changes, revealed a trend of increased nerve straightness and nerve branching with disease progression. Future studies will further examine these trends and the application of this surrogate approach to better diagnose and understand the progression of SFN.