Cell therapy for the treatment of tendinopathy--a systematic review on the pre-clinical and clinical evidence.

OBJECTIVES: This review aimed to summarize the current evidence on the safety/efficacy of cell therapy for the treatment of tendinopathy.
METHODS: A systematic literature search was conducted using various databases with relevant keywords. Both original animal and human controlled studies, covering any cell type for the treatment of naturally occurring, overuse or collagenase-induced tendinopathy, and with full text available, were included. The quality of all included studies was assessed. Relevant data on study design, safety and efficacy outcomes were extracted.
RESULTS: Eleven original studies were selected, of which nine were pre-clinical studies using the collagenase-induced tendon injury model and two were clinical studies. Types of cells, scaffolds, dosages and treatment regimens used varied. All the studies performed cell injection once. A critical appraisal of the included studies showed sub-optimal blinding. Cell therapy was generally reported to be safe, except minor complications, in the short term. Cell therapy was reported to improve tendon architecture in histology but equivocal finding was observed in sonographic/MRI examination, functional and biomechanical performance.
CONCLUSIONS: The current evidence was inadequate to make a conclusion whether cell therapy was safe and effective. Further study with adequate sample size and follow-up time, appropriate controls and optimal blinding is required. Confirmation of finding, using different tendinopathy animal models, by systematic investigation of the effects of cell sources, dosages and regimens on the outcomes, and by the inclusion of tendon pain assessment in both animals and human, is recommended. Research on the mechanisms of how cell worked in tendon repair is essential.