Histology and immunohistochemistry study of ovine tendon grafted with cBMSCs and BMMNCs after collagenase-induced tendinitis.

Objectives: The aim of this study was to compare the regeneration abilities of cultured bone marrow mesenchymal cells (cBMSC) and bone marrow mononuclear cells (BMMNC) with fibrin glue, saline solution and sham control in collagenase-induced tendinitis of the Achilles tendon in sheep.
Methods: Six sheep were recruited randomly to each group: cBMSC, BMMNC, fibrin, saline and sham control. Each group received the relative treatment two weeks after inducing lesions (T(0)). After eight weeks (T(8)) of treatment, the tendons were harvested and evaluated for histomorphology, Collagen type I, III, Cartilage Oligomeric Matrix Protein (COMP) and CD34 positive cells expression.
Results: Histology and immunohistochemistry showed similar capabilities of cBMSC and BMMNC to restore the architecture of fibres and Extra Cellular Matrix (ECM), with a high expression of collagen type I and COMP and a very low expression of collagen type III in treated tendons. The complete architectural disruption of fibres, dramatic reduction of collagen Type I and COMP expression and increase collagen type III expression were commonly observed in tendons treated with fibrin or saline only. The presence of CD34 positive cells was appreciable in the BMMNC group while few cBMSC showed this cluster of differentiation, not expressed in tendons treated with fibrin or saline.
Clinical Significance: The data in this study show the efficacy of cBMSC and BMMNC in regenerating tendon tissue after collagenase-induced tendinitis.