Short summary

The purpose of this protocol is to investigate the effect of allogenic mesenchymal stem cells (MSC) as treatment for symptomatic knee osteoarthritis. 106 patients in the ages of 40-80 years, with typical symptoms of knee osteoarthritis and a verified Kellgren-Lawrence score of 2-4 will be included. At baseline they will be randomly allocated into 2 groups of either MSC treatment or placebo.

Rationale

Osteoarthritis (OA) is the most common joint disease in adults worldwide. Studies have shown about one-third of all adults having radiological signs of OA while clinically significant osteoarthritis of the hip, hand or knee is present in 8.9 % of the adult population. Knee osteoarthritis is the most common type and present in 6% of all adults (1,2). The lifetime risk of developing symptomatic knee osteoarthritis is nearly 50% higher with a history of knee injury. The risk of developing knee OA is as high as 66% in people with obesity (3,4).

The healthcare burden of knee osteoarthritis is by the World Health Organization rated as high as patients with cardiac dysrhythmias, liver cirrhosis, or end stage kidney disease are (5). In addition, patients with knee OA have an excess mortality compared with the general population and could be considered an indicator for general health (6). Finally, due to the current increase in lifetime expectancy, there will be an equal expected increase in medical costs for OA patients (7).

The primary treatments for knee OA include exercise, weight reduction, analgesics and/or non-steroid inflammatory drugs. Other treatment therapies include corticosteroid injections, hyaluronic injection, injections of platelet rich plasma and glucosamine (8). However, surgical intervention with total knee arthroplasty remains as last resort, but should be postponed as much as possible, especially in patients < 60 years (9). Mesenchymal stem cells (MSCs) are used in an increasing number of diseases, including OA. MSCs can be extracted from various tissues, MSCs derived from bone marrow have increased potency for tissue regeneration and has shown great potential in both animals and humans (10). MSCs have the ability to differentiate into several cell lineages. Specifically, MSCs isolated from bone marrow show better chondrogenic differentiation capacity compared to cells derived from other sources (11). Due to the possibility of culturing MSC and their therapeutic properties, these cells offer an attractive, potential treatment option. However, it is unknown whether the clinical effect is a regenerative response or based on paracrine signaling and immunomodulatory effects. While autologous MSC transplantation is feasible, the clinical use has several limitations. This includes the time-consuming culture expansion and possible pain at aspiration locations for the patients. Allogeneic MSC transplantation is a more clinically feasible option since it allows the development of cell products, so they are always ready to be used in elective therapy. This is because MSCs are immune evasive and allogeneic MSC transplantation is hereby possible, due to the low level of human leukocyte antigen and major histocompatibility complex expression (11,12). Several systematic reviews have tried to conclude the best strategy for administration of MSC for knee OA, and the latest published meta-analysis concludes that larger scale randomized controlled trials (RCT) are needed for the final determination of the effect (13). Hence, this project aims to determine the efficacy of repeated allogenic stem cell intraarticular injections for treatment of knee OA compared to placebo.

The hypothesis of this study is that 2 injections of MSC with 6 months interval improves knee function from baseline to 1 year after injection in patients with knee arthritis, compared to placebo.

Description of the cohort

All patients will be recruited at Næstved Hospital, Department of Orthopedics, Region Zealand, Denmark. The study population consists of patients diagnosed with knee OA and referred to the orthopedic clinic at Næstved Hospital. Inclusion criteria: - Age of 40 to 80 years old - Kellgren-Lawrence grade 2-4 of the knee based on a standing x-ray within 6 months of examination - Symptoms of knee osteoarthritis (load related pain, joint pain, stiffness, and locomotor restriction) for ≥2 months - American Society of Anesthesiologist physical status classification system ASA 1-3 - Being able to read and understand Danish - Informed consent Exclusion criteria: - Pregnancy - Existing total or partial knee arthroplasty in index knee - Other surgery of target knee within the last 3 months - Daily use of corticosteroids

Data and biological material

Data regarding participant's medical history will be collected via the electronic medical journal system of Region Zealand "Sundhedsplatformen". When included in the study, the study participants will receive an electronic questionnaire regarding background medical information. Only the staff involved in this trial will have access to the electronic questionnaires and the Research Electronic Data Capture (REDcap) database. All data in the REDcap database will be locked in upon completion of the study before statistical analysis. Participants related background data: Demographics: - Age - Gender - Body mass Index (BMI) - American Society of Anesthesiologists Score (ASA) - Other regions with pain at inclusion Knee history: - Knee pain o Duration o NRS in activity and resting - Other diseases affecting the joints (RA, CRPS, fibromyalgia etc.) - Use of analgesics and/or non-steroid inflammatory drugs - Use of other medical treatments for knee pain (glucosamine, other) - Previous physiotherapy guided knee training (e.g. GLA:D) - Kellgren-Lawrence grade and localization of the knee OR HLA antibodies: MSC expression of HLA class II molecules are low (HLA-DR), whereas the cells express HLA class I (HLA-ABC). Even though the allogenic MSCs are injected in the knee, this procedure could increase the risk of developing an HLA-antibody response. This will be addressed by analysis for HLA antibodies in blood samples drawn before intervention, before the second injection, and at the final follow up. Furthermore, the blood samples will be used for analysis of a range of immunological markers to investigate if a systemic immunomodulatory effect can be detected.

Collaborating researchers and departments

Department of Clinical Immunology, Zealand University Hospital, Koege, Denmark

• Susanne G Sækmose: MD, MSc, Ph
• Ole BV Pedersen: MD, PhD, Associate Professor

Department of Orthopaedic Surgery and Traumatology, Odense University Hospital, Denmark

• Martin Lindberg-Larsen: MD, PhD, Associate Professor and head of research