Histochemistry of Equine Damaged Tendons, Ligaments and Articular Cartilage

Abstract

Background: The injury repair process in tendons and ligaments includes different phases such as inflammation, neovascularization, fibroblast proliferation and fibrosis. Collagen type and tissue characteristics of tendon and ligament repair are described such as type collagen differentiation and properties of the scars tissue. The degeneration of articular cartilage when, characterized by loss of the articular layers associated of the decreased of proteoglycans. The aim of this study is to describe by histochemistry techniques the characteristics of tissue scar, collagen type in the repair process of tendons and ligaments, as well as articular cartilage degeneration.Materials, Methods & Results: Tissue samples of equine tendons, ligaments and articular cartilage of the metacarpophalangeal joint region were evaluated by ultrasonography, macroscopically and prepared for routine histopathology (H&E staining). The inclusion criterion of the samples in this study was based on the presence of lesions characterized in H&E stain as fibroplasia, neovascularization, collagenolysis, chondroid metaplasia in tendons and ligaments and fibrillation and cartilaginous eburnation lesions in the articular cartilage samples. The Masson’s trichrome, Picrosirius red and Alcian blue staining techniques were also performed in addition to H&E. Pathologic findings in the tendons and ligaments included fibroplasia, collagenolysis, chondroid metaplasia and lymphohistioplasmacytic inflammation. Tendons and ligaments scars were composed of type III collagen but there was also some type I collagen. Fiber alignment of tendons and ligaments in the reorganization tissue was not flawless and the fiber appearance was characterized by a lack of the fiber crimp and parallelism. The fibroplasia was characterized by endotendinous tickening areas associated with the presence of loose connective tissue. In the areas of loose connective tissue substitution, collagen type fibers are intercalated to a lesser extent by type-III collagen fibers. In the Alcian blue stained samples of articular cartilage observed the surface layer and the matrix zone of calcified cartilage were weakly stained in blue.Discussion: Three special stains were utilized in this study along with the H&E evaluation elucidating the behavior tendons, ligaments and articular cartilage injury. The important observation in this study was fibroplasia in tendons and ligaments seems to be composed by abundant of loose connective tissue, chondrocytes and intermingled collagen type I and III fibers associated with lack of crimps alignment of the fibers. The fragile structure suggested by the Masson’s trichrome stain results (presence of the loose connective tissue) in this study perhaps make the tendons and ligaments receptive to other lesions. The characteristic blue discoloration of collagen fibers was only observed in the loose connective tissue may be because the dye penetration becomes easier when compared to the dense connective tissue (stained in red). The Masson’s trichrome made possible the differentiated the dense connective tissue of the loose connective tissue. The combined histochemistry staining technics allowed an improved characterization of fiber alignment, collagen type, inflammatory cell infiltration and neovascularization, which happens during the repair process of tendons and ligaments. The fibrillation and eburnation of the articular cartilage were associated with the decrease Alcian Blue staining characterized by degeneration process of articular cartilage.

Mechanical Overloading Induced-Activation of mTOR Signaling in Tendon Stem/Progenitor Cells Contributes to Tendinopathy Development

“…The results are consistent with previous reports that loose, immature, or degenerative connective tissues are stained blue, whereas normal tendon consisting of dense connective tissues (mainly collagen type I) are stained red with MT staining (Martinello et al, 2015;Bastiani et al, 2018). The reason for such a difference in color may be that dye penetration is easier in loose connective tissue than in the normal dense connective tissue (Bastiani et al, 2018). Using MT staining, this study was able to confirm that rapamycin injection decreased the extent of connective tissue disorganization and degeneration in the ITR tendons.…”

“…Normal cage tendons were stained red, whereas ITR tendons were stained blue. The results are consistent with previous reports that loose, immature, or degenerative connective tissues are stained blue, whereas normal tendon consisting of dense connective tissues (mainly collagen type I) are stained red with MT staining ( Martinello et al, 2015 ; Bastiani et al, 2018 ). The reason for such a difference in color may be that dye penetration is easier in loose connective tissue than in the normal dense connective tissue ( Bastiani et al, 2018 ).…”

Comparação fotomicrográfica das fibras colágenas equinas da inserção proximal do músculo interósseo III

“…Histologicamente a inserção proximal do MI III em cavalos da raça Crioulo e Puro Sangue de Corrida (PSC) apresentam uma organização tecidual fascicular muito semelhante ao observado nos tendões. O tecido conjuntivo denso é delimitado por tecido conjuntivo frouxo e intercalado com fibras musculares e adipócitos (De Bastiani et al, 2018). Sabe-se que as lesões de MI III são uma importante causa de claudicação e que tais alterações aumentam as proporções de colágeno tipo III em tecidos danificados em comparação a tecidos normais.…”