Whole structural reconstruction and quantification of epidermal innervation through the suction blister method and skin-clearing technique

Abstract

Three-dimensional (3-D) analysis of intraepidermal nerve fibers (IENFs) is conducted to advance assessment methods for peripheral neuropathies and pruritic skin disorders. The skin-clearing technique was proven to be a reliable method for 3-D imaging of IENFs. Nonetheless, it still requires further improvement in the imaging process. The aim of this study was to standardize the 3-D evaluation method of IENFs and to suggest promising 3-D biomarkers for clinical application. A total of nine healthy individuals were prospectively enrolled. The newly adopted suction blister method was combined with the tissue-clearing technique. The detailed structure of the IENFs was reconstructed and quantified using the neuron tracing software. The suction blister method showed improved linear integrity of IENFs compared with those obtained from the previously used salt-split skin test. The 3-D parameters most significantly related to natural aging were the convex hull two-dimensional perimeter and the total length (both p = 0.020). The meaningful correlations were followed by total volume (p = 0.025), ends (p = 0.026), convex hull 3-D surface, and complexity (both p = 0.030). Thus, the 3-D parameters could be utilized as possible biomarkers to identify ambiguous pathologies of peripheral neuropathies and pruritic skin disorders.

A Novel Three-Dimensional Analysis Method for Accurate Evaluation of Cutaneous Small Sensory Nerve Fibers in Mice

“…The present study demonstrated that the majority of IENFs in the mouse plantar epidermis did not branch. In humans, IENFs exhibit substantial branching, especially in the young, and this structure simplifies with age, suggesting that the degree of nerve fiber branching may also be an indicator of neuropathy [21] . However, in our young adult mice, the IENFs were sparsely branched, and the pattern was clearly different from that of humans.…”

“…Therefore, the conventional two-dimensional (2D) analysis method using tissue sections has limitations in analytical accuracy, and a new method for more precise quantification is needed. To address this issue, a 3D analysis method for the IENF density using skin biopsies has been proposed in humans, and its usefulness has been demonstrated [21][22][23] .…”