A novel arthroscopic technique for intraoperative mobilisation of synovial mesenchymal stem cells

Background: Mesenchymal Stem Cells (MSCs) have emerged as a promising candidate for tissue regeneration and restoration of intraarticular structures such as cartilage, ligaments and menisci. However, their routine use is limited in part by their low numbers and the need for methods and procedures outside of the joint or surgical field.

Purpose: To demonstrate feasibility of a technique in which minimally manipulated synovial MSC can be mobilised during knee arthroscopy. Thereby showing proof of concept for the future clinical use of native joint resident MSCs in single-stage joint repair strategies.

Study Design: Descriptive laboratory study

Methods: Patients (n=15) undergoing knee arthroscopy that were free from synovitis or active inflammation were selected. Three samples of irrigation fluid were collected from each patient at inception of the procedure, after an initial inspection of the joint and after agitation of the synovium. MSC numbers were evaluated by colony forming unit-fibroblastic assay. Synovial fluid resident and synovial-mobilised MSCs phenotype was determined by flow cytometry and their functionality by trilineage differentiation. Adhesion of culture expanded mobilised MSCs to fibrin scaffolds was also evaluated to ascertain whether mobilised MSCs might concentrate at site of bleeding.

Results: Normal irrigation during arthroscopy depleted resident synovial fluid MSCs (4-fold decrease, n=15). MSC numbers mobilised using a purpose made device were significantly higher (105-fold) then those mobilised using a cytology brush (median of 5,763 and 54 colonies respectively, p=0.001, n=15). The mobilised cellular fraction contained viable MSCs with proliferative potential and trilineage differentiation capacity for bone, cartilage and fat lineages and cultured daughter cells exhibited the standard MSC phenotype. Following culture, mobilised synovial MSCs also adhered to various fibrin scaffolds in vitro. The technique was simple and convenient to use and not associated with any complications.

Conclusions: Numbers of functional MSCs can be greatly increased during arthroscopy using this technique to mobilise cells from the synovium.