Article

Collagen and Picrosirius Red Staining: A polarized light assessment of fibrillar hue and spatial distribution

Department of Anesthesiology, University of Massachusetts Medical School, Worcester, MA, USA
J. morphol. Sci 01/2005; 22(2):97-104.

ABSTRACT

Collagen plays a vital role in maintaining structural integrity and in determining tissue function. Therefore, methods to detect, quantify, and analyze collagen are valuable. Nevertheless, stains historically employed to detect collagen have disadvantages, principally a poor specificity for thin fibers. Conversely, picrosirius red, which has the capability to detect thin fibers, although frequently used, is seldom exploited to the fullest extent. Our goal was, using picrosirius red staining, circularly polarized light, and image-analysis software, not only to identify fibers and quantify collagen content, but also to assess fiber hue and the spatial distribution of the different colors. To assess collagen content, we used a subtraction technique to remove interstitial space and non-collagen elements from images of skin wounds, myocardial scars, and arterial tissue. The hue component of the resulting image was obtained, and the number of red, orange, yellow, and green (the colors of collagen fibers in order of decreasing thickness) pixels calculated. Finally, we assessed the spatial distribution of individual colors by the application of color threshold filters. Skin wound analysis demonstrated good inter-observer agreement for collagen content and fiber color. In myocardial scars, collagen content increased from 1 (61%) to 5 weeks (95%) after injury. The proportion of green (thin) fibers decreased (43 to 4%), while the proportion of orange (thick) fibers increased (13 to 65%). Color threshold application revealed regional variation in fiber color within subintimal arterial lesions. These methods increase the amount of structural information obtained from picrosirius red-stained sections. INTRODUCTION Collagen fibers play a vital role not only in maintaining structural integrity, but also in determining tissue function. For example, collagen degradation and loss after myocardial infarction is associated with infarct expansion and subsequent functional decline [33]. On the other hand, although collagen confers tensile strength, excess accumulation is often detrimental. For instance, increased fibrosis after kidney transplant leads to a decrease in renal function and eventual graft failure [6,9], and hence quantification of fibrosis has been suggested as a means to predict graft survival. In such examples, insight into pathological structure-function relationships depends upon accurate identification of collagen fibers.

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    • "The sections were observed with a BX53 Olympus microscope and the images were acquired using an Olympus DP 21 camera. PSR stained sections were investigated under polarized light and the images were processed in order to quantitatively determine the proportion between red/thick collagen fibers and green/thin collagen fibers, by using imageJ ®[30,31]. The red signal is related to the thicker/mature collagen fibers of type I collagen while the green signal is related to the thinner/immature collagen fibers of type III collagen[14]. "

    Full-text · Article · Jan 2016 · Biofabrication
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    • "Picrosirius red staining of the femur was used to assess collagen content (Fig. 8A) as described previously [39]. Mecp2 stop/y mice showed a significant decrease (−24%) in collagen content compared to Wt mice (Fig. 8B; Wt = 65.1 ± 8.6%; Mecp2 stop/y = 48.8 "
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    Full-text · Article · Oct 2014 · Bone
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    • "Although type III collagen fibers are usually thinner than type I fibers, it would be presumptuous to state that green (thin) fibers and orange-red (thick) fibers are indicative of type III and type I collagen, respectively. The same authors also speculated the possibility of a green fiber being an immature, thin type I fiber or a thick type I fiber being “smeared” by a sectioning artifact, thereby decreasing its thickness.[9] "
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    ABSTRACT: Introduction:Radiation, commonly employed as neoadjuvant, primary, and adjuvant therapy for head and neck cancer causes numerous epithelial and stromal changes, prominent among which is fibrosis with its early and late consequences. Very little is known about the true nature of the fibrosed tissue and the type of fibers accumulated. Radiotherapy affects the supporting tumor stroma often resulting in a worsening grade of tumor post-radiation.Aim:To study epithelial, neoplastic, stromal, and glandular changes in oral cavity induced by radiation therapy for oral squamous cell carcinoma (OSCC) using special stains.Materials and Methods:The study included 27 samples of recurrent OSCC following completion of radiotherapy (recurrence within an average span of 11 months), and 26 non-irradiated cases of OSCC. Patients with a history of combined radiotherapy and chemotherapy were not included in the study. The epithelial changes assessed included epithelial atrophy, apoptosis, necrosis, dysplasia, and neoplasia. The connective tissue was evaluated for amount of fibrosis, quality of fibers (using picrosirius red staining), fibrinous exudate, necrosis, pattern of invasion, vessel wall thickening, and salivary gland changes. The aforementioned changes were assessed using light and polarizing microscopy and tabulated.Statistical Analysis:Epithelial and connective tissue parameters were compared between the irradiated and non-irradiated cases using chi square and t-tests.Results:Epithelial and connective tissue parameters were found to be increased in irradiated patients. Pattern of invasion by tumor cells varied from strands and cords between the two groups studied. The effect of radiation was seen to reflect on the maturity of fibers and the regularity of their distribution.
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