Use of bone marrow mesenchymal stem cells in case of excision of superficial flexor tendon in the horse: a case report.

Tendon injuries in horses often compromise the return to the same level of activity, despite what is considered appropriate management, because the scar tissue formed in the repair process make the tendon functionally deficient in comparison to normal. A multitude of treatments have been advocated for the management of tendon injuries, including the intralesional injection in the lesion of mesenchymal cells and the use of Growth factors (platelet rich Plasma). In this study, the authors describe the use of autologous MSC in PRP medium in an Arabian horse to enhance the repair of severed traumatic superficial digital flexor tendon (SDFT) surface. A 3-year-old Arabian horse was admitted because of a right frontlimb 3 cm reverse V shaped wound between middle and distal third of the palmar metacarpal surface, with few blood lost, caused by entangled wire fence of the paddock. It was evident from outside the complete tear of the SDFT. The horse was immediately subjected to surgery under general anesthesia. During surgery, after curettage of the extremities, the two stumps of the tendon were apposed with Bunnell suture and the fascia was then closed in continuous pattern. In a second surgical field, bone marrow was aspirated from iliac crest. Immediately after surgery a cast was applied. Anti-inflammatory and antibiotic drugs were administered for 10 days. A total of 75 ml of bone marrow aspirate were collected and sent to the laboratory, where samples were diluted 1:1 in PBS solution supplemented with antibiotics and centrifuged for 15 min at 300g. The pellet was re-suspended in 5ml of culture medium (DMEM and TCM-199, 1:1 plus 10% FBS), placed on 5 ml of 70% Percoll solution and centrifuged at 1200g for 30 min. The interface layer was then aspirated and re-suspended in culture medium, washed for three time by centrifugation and seeded into 25 cm2 flasks. In vitro culture was performed in a 5% CO2 incubator at 38.5°C. Medium was refreshed after 48 h then twice a week. After six weeks the cast was removed and an ultrasound examination was performed. A big abnormality of tendon shape, anaechoic lesion with a cross section area (CSA) of about 75% of tendon volume was evident. The fiber disruption pattern was along the midline, with the division of tendon into medial and lateral components. Therefore, it was decided to make an ultrasound guided inoculum MSC in PRP suspension (11.1 x 106 cells in 4 ml of platelet gel). The patient followed a rehabilitation protocol for about four months. Fifteen days after treatment with MSC and PRP, the flexor right metacarpal area was significantly increased in volume compared to the contralateral. The ultrasound examination revealed an early stage of re-organization of tendon fibers with a less persistent hypoechoic fiber pattern. Four months after the injection, the overall appearance of the area was still slightly enlarged. At the ultrasound examination an axially isoechogenic alignment fiber bundle, favorable CSA and textural improvement was evident and the trend of tendon fibers was normal. One year after the injury the horse is in sport activity. In conclusion the result obtained is largely satisfactory starting from four months after inoculation when the tendon showed a reorganization of the fibers entirely physiological. Such data must be confirmed by treating a significant number of patients with the same acute lesion and not suffering recurrence during follow up longer than one year.