Tseng, H.-C. | bioRxiv Science

bioRxiv2022

A Noninvasive Skin Biopsy of Free Nerve Endings via Realtime Third-Harmonic Microscopy

Skin biopsy was the only method to provide free-intraepidermal-nerve-endings (FINEs) structural information for the differential diagnosis of small fiber neuropathy (SFN). Its invasive nature was particularly unfavorable for patients with diabetic coagulation abnormalities thus there is an unmet clinical need for a non-invasive FINEs imaging tool. Here we show a tightly-focused epi-Third-harmonic-generation microscope (TFETM) for unmyelinated FINEs imaging. Its label-free capability was confirmed by PGP9.5 immunohistochemistry staining and a longitudinal spared nerve injury model study. Moreover, through proposing a dot-connecting algorithm, we established the operational protocol to count three-dimensionally the intraepidermal nerve fibers (IENF) and define the quantitative IENF index. Our clinical trial showed that the label-free IENF index can differentially identify SFN (P-value=0.0102) and was well correlated with IENF density of skin biopsy (Pearsons correlation, R-value= 0.98) in the DPN group. Our study suggested that the unstained dot-connecting third-harmonic microscopy imaging can noninvasively provide FINEs structure information assisting diagnosing SFN.

bioengineering↗

bioRxiv2021

The In Vivo Source of Type I and Type III IFNs is Pathogen Dependent

Type I (-, {beta}) and type III (-{lambda}) interferons (IFNs) are produced in response to virus infection and upregulate a largely overlapping set of IFN stimulated genes which mediate the protective effects of these antiviral cytokines. In vitro studies have demonstrated the redundancy of these two cytokine families which activate the same transcription factor, IFN stimulated gene factor 3 (ISGF3), via distinct ligands and receptors. However, in vivo, these IFN types do have distinct functions based on receptor distribution, but also ligand availability. Using a newly generated IFN-{lambda} reporter mouse strain we have observed that both type I and type III IFNs are produced in response to respiratory tract infection by Newcastle disease virus (NDV) and influenza A virus (IAV). In the case of NDV these IFNs are synthesized by different cell types. Type I IFNs are produced primarily by alveolar macrophages, type III IFNs are made only by epithelial cells, and production of either is dependent on MAVS. While epithelial cells of the respiratory tract represent the primary target of IAV infection, we found that they did not significantly contribute to IFN-{lambda} production, and IFN-{lambda} protein levels were largely unaffected in the absence of MAVS. Instead we found that pDCs, a cell type known for robust IFN- production via TLR/MyD88 signaling, were the major producers of IFN-{lambda} during IAV infection, with pDC depletion during influenza infection resulting in significantly reduced levels of both IFN- and IFN-{lambda}. In addition, we were able to demonstrate that pDCs rely on type I IFN for optimal IFN-{lambda} production. These studies therefore demonstrate that the in vivo producers of Type III IFNs in response to respiratory virus infection are pathogen dependent, a finding which may explain the varying levels of cytokine production induced by different viral pathogens.

immunology↗