Histological and Immunohistochemical Evaluation of Autologous Cultured Bone Marrow Mesenchymal Stem Cells and Bone Marrow Mononucleated Cells in Collagenase-Induced Tendinitis of Equine Superficial Digital Flexor Tendon
Figure 3
Tissue slides obtained from SDFTs injected with cBMSCs, and BMMNCS. Tissue stains with hematoxylin-eosin (H and E) and Herovyci (Hero) highlight the longitudinal orientation of collagen fibers after transplantation of cBMSCs and BMMNCS; Histological examination of the sham tendons, both with HE and Herovyci staining, showed the presence of mature collagen (i.e., predominantly strong red Herovyci staining of fibers in tendon sections) and a longitudinal fiber orientation, signifying a normal tendon architecture. Additionally, the absence or very scanty mononuclear cell infiltrate was observed in all normal control tendons. No inflammatory or other reactions to the fibrin glue were observed in any of the treated limbs, and at T21 no fibrin residues were recognized in microscopic examinations. (T21) Tissue slides from the superficial digital flexor tendons (SDFT) following experimentally induced tissue injury and subsequent treatment with cultured bone marrow mesenchymal stem cells (cBMSCs (a)) and Bone Marrow Mononucleated Cells (BMMNCS (b)). Incomplete maturation of collagen was verified by the observation of blue staining fibers mixed with red ones. In BMMNCS a large number of mononucleated cells are recognizable in the interfascicular zone. Immunohistochemistry stains for Collagen type I (C/I) and collagen type III (C/III) show a high expression of C/I and a very low expression of C/III. Stains for cartilage oligomeric matrix protein (COMP) expression. BMMNCS-treated SDFT (b) show a strong, diffuse expression like sham SDFT (Figure 4()). Immunohistochemistry staining for the expression of CD34+ mononucleated cells in cBMSCs (a) shows a low expression limited to the interfascicular zone. In BMMNCS (b)-treated SDFT, the presence of numerous mononucleated CD34+ cells near microvessels, which sometimes show some CD34+ endotheliocytes in their wall, which is highlighted. In cBMSC- and BMMNCS-treated SDFTs, microscopic examination at T21 revealed a longitudinal orientation of newly formed collagen fibers. At this time point, sections stained by the Herovyci method revealed minimal areas of blue-stained thin, well-oriented precollagen fibers mixed with well-differentiated and- oriented red-stained mature collagen fibers, indicating a still somewhat incomplete collagen maturation at this time in the treatment. In BMMNCS-treated SDFTs also, large numbers of mononucleated cells were present in the interfascicular zone. In contrast, in placebo SDFTs, injected with saline or fibrin, the tissue architecture was disrupted or markedly modified, showing blue precollagen and red collagen fibers randomly or not longitudinally oriented, and a relatively loss of the architectural pattern.
