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Introduction: Tendon injuries are notorious for slow and functionally inferior healing. It is claimed that cell-based therapy would result in faster and more efficient healing of injured tissues with less postoperative complications. Given the limitations associated with ex vivo cellular expansion, we tried to evaluate the possible effects of intratendinous injection of adipose derived stromal vascular fraction on mechanical properties of tendon repair., Methods: The model of injury was complete sharp transection of rabbit deep digital flexor tendon followed by primary suture repair and an intratendinous injection of either allogeneic stromal vascular fraction or placebo. Tendons were harvested at three and eight weeks after surgery., Results: The results of mechanical testing showed the treatment caused significant increase in ultimate and yield loads, stress, and energy absorption of repairs compared to controls at both time points. Also, improvement in terms of strain and stiffness were detected at the eighth week in treatments., Discussion: In comparison with the result of previous studies using cultured mesenchymal stem cells from bone marrow or adipose tissue; the improved mechanical properties observed in the present study suggest that choosing stromal vascular fraction as a readily accessible and instant source of multipotent cells instead of expensive and long-lasting culture expansion may seem more favorable in cell based therapy for tendon injuries. The mechanical functionality of the repairs observed in the present study encourages further investigations into the use of stromal vascular fraction for the repair of tendon injuries.

Objective: To evaluate the potential effects of uncultured adipose-derived stromal vascular fraction on tendon healing., Methods: Twenty five adult male New Zealand white rabbits weighing 2.5-3.0 kg were used. Five rabbits were used as donors of adipose tissue and the rest were divided into control and treatment groups. The injury model was completed by unilateral tenotomy through the middle one third of deep digital flexor tendon. Immediately after suture repair, either fresh stromal vascular fraction from enzymatic digestion of adipose tissue or placebo was intratendinously injected at tendon stumps in treatment and control groups, respectively. Immobilization with cast was continued for two weeks after surgery. Animals were sacrificed at eight weeks after surgery and tendons underwent histological, immunohistochemical, and mechanical evaluations. Statistical analyses of quantitative and qualitative data were assessed using one-way analysis of variance and Mann-Whitney U-test, respectively., Results: Histological evaluations demonstrated superior fibrillar linearity and continuity, and decreased vascularity in treatment group indicated improved organization and remodeling of neotendons. Immunohistochemistry de- monstrated a significant increase in collagen I expression in treatment group. Ultimate load and energy absorption capacity were both significantly increased in cell-treated repairs compared with controls., Conclusion: The present study shows that intratendinous injection of uncultured adipose-derived stromal vascular fraction results in improved structural and mechanical properties of tendon repairs and it could be an effective modality for treating tendon injury.

Objective(s): Tendon healing is substantially slow and often associated with suboptimal repair. Cell therapy is one of the promising methods to improve tendon repair. Blastema, a population of undifferentiated cells, represents characteristics of pluripotent mesenchymal stem cells and has the potentials to be used in regenerative medicine. The aim of this study was to investigate the use of blastema allotransplantation in rabbit tendon healing. Materials and Methods: In this study, one rabbit was used as a blastema donor, and twenty-four rabbits were divided into control and treatment groups. Blastema cells were obtained from ear pinna upon punch hole injury in the donor rabbit. Under general anesthesia, a complete transverse tenotomy was performed on the midsubstance of deep digital flexor tendon followed by suture-repair. In the treatment group, 1 × 106 blastema cells suspended in buffer saline were injected intratendinously at the repair site, while the control group received only the buffer saline. Cast coaptation was maintained for two weeks. Eight weeks after the operation, tendons were harvested, and histopathological, biomechanical, and biochemical assays were performed on samples. Results: Mechanical testing showed a significant increase in ultimate load, energy absorption, stiffness, yield load, stress, and strain in blastema-treated tendons compared to controls. Also, higher hydroxyproline content and improved collagen alignment along with lower inflammatory cell infiltration and decreased angiogenesis were observed in blastema-treated tendons. Conclusion: Increased levels of hydroxyproline and improved histopathological and biomechanical parameters in the treatment group suggest that blastema cells could be considered an adjunct to tendon repair in rabbits. [ABSTRACT FROM AUTHOR]

Objective: Tendon never returns to its complete biological and mechanical properties after repair. Bone marrow and, recently, adipose tissue have been used as sources of mesenchymal stem cells which have been proven to enhance tendon healing. In the present study, we compared the effects of allotransplantation of bone marrow derived mesenchymal stromal cells (BMSCs) and adipose derived stromal vascular fraction (SVF) on tendon mechanical properties after experimentally induced flexor tendon transection. Materials and Methods: In this experimental study, we used 48 adult male New Zealand white rabbits. Twelve of rabbits were used as donors of bone marrow and adipose tissue, the rest were divided into control and treatment groups. The injury model was a unilateral complete transection of the deep digital flexor tendon. Immediately after suture repair, 4×106 cells of either fresh SVF from enzymatic digestion of adipose tissue or cultured BMSCs were intratendinously injected into tendon stumps in the treatment groups. Controls received phosphate-buffered saline (PBS). Immobilization with a cast was continued for two weeks after surgery. Animals were sacrificed three and eight weeks after surgery and tendons underwent mechanical evaluations. The differences among the groups were analyzed using the analysis of variance (ANOVA) test followed by Tukey's multiple comparisons test. Results: Stromal cell transplantation resulted in a significant increase in ultimate and yield loads, energy absorption, and stress of repairs compared to the controls. However, there were no statistically significant changes detected in terms of stiffness. In comparison, we observed no significant differences at the third week between SVF and BMSCs treated tendons in terms of all load related properties. However, at the eighth week SVF transplantation resulted in significantly increased energy absorption, stress and stiffness compared to BMSCs. Conclusion: The enhanced biomechanical properties of repairs in this study advocates the application of adipose derived SVF as an excellent source of multipotent cells instead of traditional BMSCs and may seem more encouraging in cell-based therapy for tendon injuries. [ABSTRACT FROM AUTHOR]