Label-Free Infrared Spectral Histology of Skin Tissue Part I: Impact of Lumican on Extracellular Matrix Integrity

Abstract

Proteoglycans (PG) play an important role in maintaining the extracellular matrix (ECM) integrity. Lumican, a small leucine rich PG, is one such actor capable of regulating such properties. In this study, the integrity of the dermis of lumican-deleted Lum −/− vs. wildtype mice was investigated by conventional histology and by infrared spectral histology (IRSH). Infrared spectroscopy is a non-invasive, rapid, label-free and sensitive technique that allows to probe molecular vibrations of biomolecules present in a tissue. Our IRSH results obtained on control (WT, n = 3) and Lum −/− (n = 3) mice showed that different histological structures were identified by using K-means clustering and validated by hematoxylin eosin saffron (HES) staining. Furthermore, an important increase of the dermis thickness was observed in Lum −/− compared to WT mice. In terms of structural information, analysis of the spectral images also revealed an intra-group homogeneity and inter-group heterogeneity. In addition, type I collagen contribution was evaluated by HES and picrosirius red staining as well as with IRSH. Both techniques showed a strong remodeling of the ECM in Lum −/− mice due to the looseness of collagen fibers in the increased dermis space. These results confirmed the impact of lumican on the ECM integrity. The loss of collagen fibers organization due to the absence of lumican can potentially increase the accessibility of anti-cancer drugs to the tumor. These results are qualitatively interesting and would need further structural characterization of type I collagen fibers in terms of size, organization, and orientation.

Assessment of Ovarian Tumor Growth in Wild-Type and Lumican-Deficient Mice: Insights Using Infrared Spectral Imaging, Histopathology, and Immunohistochemistry

“…The correlation process resulted in a new image with a correlation scale ranging from 0 (dark color) to 1 (white color). In this way, the distribution of collagen in the tissue could be visualized [ 40 ].…”

“…Moreover, edemas were observed in tumor sections of both groups (Figure 2e,f), but were significantly predominant in Lum −/− mice (Figure 2g, p = 0.02). These differences might be explained by the loss of ECM integrity due to altered collagen fibrilogenesis caused by lumican depletion, resulting in an increased tumor growth [34,40]. Alterations in stromal tissue components can inhibit or promote epithelial tumorigenesis.…”

“…At the tissue level, FTIR imaging, combined with multivariate statistical analysis, has shown the ability to discriminate inflammatory from non-inflammatory breast cancer tissues [ 38 ], and metastatic from non-metastatic lymph nodes in melanoma patients [ 39 ]. In a recent study, dermis of wild-type versus lumican-deficient mice were characterized by infrared spectral imaging [ 40 ]. In addition, melanoma primary tumors treated with or without lumican-derived peptide were discriminated through infrared spectral imaging [ 41 ].…”

Lumican Inhibits In Vivo Melanoma Metastasis by Altering Matrix-Effectors and Invadopodia Markers

“…Biologically, lumican is able to regulate various physiological processes, like collagen fibrillo-genesis, cell proliferation, adhesion, migration and invasion [ 21 , 25 , 26 ]. Moreover, the anticancer effect of lumican was reported in numerous publications [ 13 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. The former studies [ 28 , 29 ] utilized as a melanoma model, B16F1 cells transfected with the human lumican cDNA injected subcutaneously in wild-type C57BL/6J mice.…”