Skin Collagen Fiber Molecular Order: A Pattern of Distributional Fiber Orientation as Assessed by Optical Anisotropy and Image Analysis

Abstract

BackgroundBirefringence can reveal much of the morphology, molecular order, heterogeneity of fiber orientation, and nonlinear optical properties of biopolymers such as collagen. However, the detailed characterization of skin collagen fibers using optical anisotropy methods remains elusive. A clear understanding of collagen fiber organization in skin tissues may be important in the interpretation of their structural-functional relationships under normal and pathological conditions. In this study, fiber orientation in collagen bundles (CBs) and their supramolecular organization were examined in rat skin using polarization microscopy and image analysis.Methodology/Principal FindingsImage variations with rotation of the microscope stage and selection of the in-depth focus plane were investigated in unstained sections of varying thicknesses from rat skin fragments. Total birefringence (image analysis) and form and intrinsic birefringence (Sénarmont’s method) were estimated. Based on the birefringent images, CBs were found to contain intercrossing points with a twisted helical distribution of collagen fibers (chiral elements) and frequently presented circular structures. Collagen fibers were observed to extend from the surface level to deeper planes, creating a 3D-network of oriented intertwined CBs. At least three levels of birefringent brilliance intensity were revealed by image analysis, indicating a heterogeneous spatial organization of the CBs. Slight differences in optical retardations were found for CBs immersed in some of the fluids used in a comparison of 170- and 240-day old rats.Conclusion/SignificancePolarization microscopy studies provide detailed high-quality structural information on rat skin CBs. A 3D-network structure based on image analysis and birefringence compensation for collagen fibers is suggested for CBs. Form and intrinsic birefringence evaluation can reveal differences in the rat skin associated with age at the levels of collagen fiber crystallinity and macromolecular organization. These findings may inspire future studies of the feedback mechanisms by which spatial, bioelectrical and biomechanical information is transmitted from CBs to skin cells.

Biomodulation effects of LED and therapeutic ultrasound combined with semipermeable dressing in the repair process of cutaneous lesions in rats

“…The energy provided by LED therapy alters this condition, generating an environment that favors the formation of new blood vessels and proliferation of fibroblasts, which produce collagen fibers and extracellular matrix 8,15 . Several studies have demonstrated the action of LED during the early stages of tissue repair in a variety of clinical situations by the early activation of the inflammatory phase, significantly increasing fibroblast proliferation and reducing the inflammatory infiltrate 7,10 .…”

Comparative Study of Morphometric and Fourier Transform Infrared Spectroscopy Analyses of the Collagen Fibers in the Repair Process of Cutaneous Lesions

“…18,19,41 At 14 days, the qualitative histological analysis showed a predominance of thick fibers (type I) in the group LED + D, when compared with the other groups, which is characteristic of the process of fibrillogenesis. 4,40,42 Moreover, in this experimental period, the animals in the groups treated with phototherapy (LED and LED + D) had statistically significant morphometric results regarding the deposition of collagenous fibers, when compared with the control. Considering the data obtained at this experimental time for the LED group, this result is probably due to the action of phototherapy, making energy available to the cells that were damaged by the surgical process, thus accelerating the repair process during its secondary phase.…”

“…1,2 It is critical for the formation of the extracellular matrix of connective tissue. 3,4 It is important to quantify this protein in skin wounds because its formation is associated with the tissue repair process. [3][4][5] The macroscopic and histomorphometric analyses provide qualitative and quantitative benefits in assessing the evolution of tissue repair process.…”

“…3,4 It is important to quantify this protein in skin wounds because its formation is associated with the tissue repair process. [3][4][5] The macroscopic and histomorphometric analyses provide qualitative and quantitative benefits in assessing the evolution of tissue repair process. However, new analytical techniques have been studied for a better understanding of tissue repair process.…”

“…However, new analytical techniques have been studied for a better understanding of tissue repair process. 4,6,7 Among the optical spectroscopic techniques, Fourier transform infrared spectroscopy (FT-IR) stands out for its ability to identify biological tissue components through the characterization of vibrational modes of molecular radicals. 8 It produces spectral images of histological sections and identifies biomolecular changes in tissues by studying the variance of the vibrational bands of biomolecules.…”