Adult mesenchymal stem cells for the treatment in patients with rotator cuff disease: present and future direction

Abstract

Comment on: Jo CH, Chai JW, Jeong EC, et al. Intratendinous injection of autologous adipose tissue-derived mesenchymal stem cells for the treatment of rotator cuff disease: a first-inhuman trial. Stem Cells 2018;36:1441-50. Rotator cuff tendon tear (RCTT) is reported to be one of the most common causes of chronic shoulder pain in the United States with more than 250,000 RCTT repairs each year (1). Individuals under 60 years of age show a 6% incidence of full-thickness RCTT, while those over 60 show an incidence of 30%, as determined by cadaveric studies (2). RCTT results in considerable disability and diminished quality of life for many patients (3). Chronic tendon degeneration is currently considered a major contributor to the pathology of RCTT (4). Treatment for RCTT includes conservative treatments such as exercise, electrotherapy, acupuncture, manual treatment, taping, steroid and platelet-rich plasma injections and surgical treatment (5). Surgical repair for tendon tear is one of the most common orthopedic procedures undertaken today (6). The classification of RCTT using a reliable classification method is critical to improve the treatment of rotator cuff disease. This classification has been used to determine the appropriate treatments to achieve the best results for each type of tendon tear. Many factors such as tear size, shape, retraction, and fatty infiltration have been identified as important factors when assessing a patient with a symptomatic RCTT. RCTT are classified as either partial-or full-thickness. Partial-thickness tears are focal defects in the rotator cuff tendon and involve only bursal or articular surface or intratendinous. Full-thickness tears extend from the articular surface to the bursal surface of the tendon. Ellman (7) proposed a classification system for partial-thickness RCTT based on intra-operative findings according to the location (bursal-side, articular-side, and intratendinous), grade, and tear area (mm 2). In his classification, a grade 3 tear is >6 mm deep (>50%), a grade 2 tear is 3-6 mm in depth but not exceeding one-half of the tendon thickness (25-50%), and a grade 1 tear is considered as <3 mm deep (<25%). DeOrio and Cofield (8) developed classification systems for full-thickness RCTT, which involved measuring the anterior-posterior length of the tendon that was torn off of the humeral head at the time of surgery. Their system classified tendon tear size as massive if the tear was greater than 5 cm, large if the tear was 3-5 cm, medium if the tear was 1-3 cm, and small if the tear was less than 1 cm in length. For acute tears, and in patients younger than 65 years, in the case of chronic, reparable tears larger than 1 cm and without significant chronic muscle changes (such as atrophy, fatty infiltration, and impairment of the biomechanical properties of the repair sites), early surgical repair can be considered. Early surgical repair can also be considered in large bursal-sided partial thickness tears (larger than 6 mm or more than 50% of the tendon thickness) because the risk of tear progression and rate of failure of conservative treatment is high (9). However, the failure rate for rotator cuff tendon repair is 20-90% (10) and the outcome can vary depending on the patient's age, tear size, chronicity, muscle atrophy, fatty degeneration, tendon quality, operative technique, and postoperative rehabilitation treatment (11). Revision rotator