CELL THERAPY FOR REPAIR OF CARTILAGE DEFECTS IN THE ANKLE – HOW DOES IT WORK AND WHO SHOULD WE TREAT?

Tian Lan, Karina Wright, Nilesh Makwana, Andrew Bing, Charlotte Hulme and Helen McCarthy

Funded by the Orthopaedic Institute

Cartilage defects often develop in the ankle following traumatic injury, commonly leading to osteoarthritis (OA) if left untreated. Symptomatic patients may experience swelling, locking, catching, prolonged pain and will require surgical interventions. So far, microfracture still remains the “gold standard” for lesions less than 150 mm2. However, advanced cell therapies are required for larger defects and patients who failed microfracture surgery. Autologous chondrocyte implantation (ACI) has been successfully used in treating knee cartilage defects, however, it has not been approved by NICE to use in the ankle.

Ankle surgeons at RJAH have been trialling a new procedure for treating cartilage defects in the ankle (see picture insert 1) using an injection of Bone Marrow Aspirate Concentrate (BMAC) onto the damaged cartilage surface, with promising preliminary results. Briefly, Bone Marrow Aspirate (BMA) is taken from the hip and concentrated using the Complete Cartilage repair (CCR) commercial kit, which uses centrifugation to enrich the therapeutically active components of bone marrow. BMAC is mixed with hyaluronan and fibrin glue, forming a gel which can be injected onto the defect site and holding the BMAC in position (see picture insert 2).

While BMAC has shown positive clinical outcomes, we want to determine which components are therapeutic and which group of people will potentially benefit from this treatment. Enriched mesenchymal stem cells (MSCs) in BMAC are proposed to be inducers of cartilage regeneration, however, currently there is no point-of-care assessment for BMAC quality; especially regarding the proportion of MSCs within. This part of the study aims to characterise the cellular component of CCR-generated BMAC using a point-of[1]care device, and to correlate the results with patient clinical outcomes to identify potential therapeutic components in the BMAC.

Donor-matched bone marrow aspirate (BMA), BMAC and BMAC mixed with thrombin (B+T – the CCR treatment) were obtained from consented patients undergoing surgery with CCR. Total nucleated cells (TNC), red blood cell (RBC) and platelet (PLT) counts were measured using a Horiba Micros ES60 haematology analyser, and the proportion of MSCs in BMA, BMAC and B+T were assessed. Our results show BMAC preparations were highly variable in terms of cellular components. Mixing BMAC and thrombin however, as described in the CCR protocol, resulted in a dramatic reduction in TNCs, PLTs and MSCs.

 The next stage of this Orthopaedic Institute funded PhD study will be to use a multiplex assay to investigate the cytokine and growth factors in the BMAC plasma layer, and to try to find the active components for BMAC therapy. At the same time, we are also optimising an in vitro co-culture system to mimic the CCR surgical procedure, to investigate which part of the CCR procedure (BMAC or hyaluronan and fibrin glue or both of them) is the active component for cartilage regeneration.