Therapeutic Effects of Umbilical Cord Blood-Derived Mesenchymal Stem Cells Combined with Polydeoxyribonucleotides on Full-Thickness Rotator Cuff Tendon Tear in a Rabbit Model

While therapies using mesenchymal stem cells (MSCs) to treat rotator cuff tendon tear (RCTT) have yielded some promising preliminary results, MSCs therapy has not yet completely regenerated full-thickness RCTT (FTRCTT). It has recently been reported that polydeoxyribonucleotide (PDRN) is effective in the treatment of chronic rotator cuff disease. We hypothesized that local injection of human umbilical cord blood-derived (UCB)–MSCs with PDRN would be more effective in regenerating tendon tear than UCB-MSCs alone. The purpose of this study was to evaluate the effects of UCB–MSCs combined with different doses of PDRN on the regeneration of RCTT in a chronic RCTT model by using a rabbit model. New Zealand white rabbits (n = 24) with FTRCTT were allocated randomly into three groups (8 rabbits per group). Three different injectants (G1-S, 0.2 mL UCB-MSCs; G2-P1, 0.2 mL UCB-MSCs with one injection of 0.2 mL PDRN; G3-P4, 0.2 mL UCB-MSCs, and four injections of 0.2 mL PDRN per week) were injected into FTRCTT under US-guidance. After the rabbits were euthanized, we evaluated ross morphological and histological change. Motion analysis was also performed. There were significant differences in gross morphological changes between before, and at 4 weeks after injection, in all three groups, but no differences were found among the three groups. Masson’s trichrome (MT) or anti-type 1 collagen antibody (COL-1)-positive cell densities in G2-P1 and G3-P4 were improved significantly compared with those in G1-S, but showed no significant difference between G2-P1 and G3-P4. On motion analysis, walking distance and fast walking time in G2-P1 and G3-P4 were significantly longer/higher than those in G1-S, but showed no significant differences between G2-P1 and G3-P4. These results demonstrated that there was no significant difference in the gross morphologic change of tendon tear between UCB-MSCs only and combination with PDRN injection in rabbit model of chronic traumatic FTRCTT. Furthermore, there were no significant differences in the regenerative effects between high and low doses of (0.8 and 0.2) mL of PDRN.