Stem cells application in meniscal tears: a systematic review of pre-clinical and clinical evidence

Objective: Conservative and surgical treatments for meniscal lesions are various and this field of orthopedic surgery is in continuous development. Stem cells represent one of the current options to stimulate meniscal healing. The present systematic review aimed at summarizing the state of art in the application of stem cells for the treatment of meniscal damage both at pre-clinical and clinical level. Materials and methods: The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed to perform this systematic review. A systematic search was performed using the PubMed (MEDLINE), EMBASE and Cochrane Library databases. All the studies dealing with the application of stem cells as a treatment for meniscal tears were pooled, data were extracted and analyzed. The studies were divided into two groups (pre-clinical and clinical), and then, discussed independently. Results: A total of 18 studies were included. Thirteen were classified as "pre-clinical" and five as "clinical". The most commonly used cells were mesenchymal stem cells (MSC), derived from bone marrow (BMMSC), synovial tissue (SMSC), or adipose tissue (ADSC). Follow-ups ranged from 2 to 16 weeks for the pre-clinical studies and from 3 to 24 months for the clinical studies. All studies documented good results in terms of laboratory markers/scores, clinical and radiologic evaluation. Conclusions: Based on the currently available data, it is not possible to establish the best cell source or delivery method for the treatment of meniscal injuries. Bone Marrow derived stem cells delivered through injection represent the most studied approach, with the most promising results. However, the full impact of these therapies through their different sub-type of stem cells and implantation techniques still needs to be critically analyzed through larger randomized controlled trials with longer follow-up.