This study is looking at a new treatment, using the patient's own stem cells (the repair cells of the body), to see whether this can help reduce pain and promote healing of the Achilles tendon, without side effects.

Tendon disorders compromise pain free activity and often progress to chronic pain with a major impact on quality of life. More than 85,000 patients each year see their general practitioner (GP) with Achilles Tendinopathy (AT) which affects the lower leg in young and middle aged adults. The main treatment is physiotherapy, although surgery is eventually considered in 25-45%of patients, an intervention that requires several months of immobilisation and has unpredictable outcomes.

Other treatments include, shockwave therapy, Platelet Rich Plasma (PRP) (a blood injection of platelet rich plasma) and steroid injections, but other than physiotherapy non have been shown to be better than placebo. There is a need for improved nonsurgical treatments. There is an established treatment in horses that involves injection of the horses own stem cells into the tendon, which has been shown to be effective but has never been used in man. We wish to translate the technology to humans and propose a pilot phase II trial to establish the safety of stem cells implanted in diseased human tendon. We aim to study 10 patients with chronic mid substance achilles tendinopathy to assess safety as our primary outcome measure. In addition we capture clinical outcomes scores and ultrasound appearances. Other than the stem cell injection, all assessments will be non invasive. Participants will be otherwise healthy adults, aged 18-70 and recruited from routine outpatient clinics at the Royal National Orthopaedic Hospital, presenting with a painful heel, diagnosed by a specialist as Achilles tendinopathy, and having already undergone a minimum of 6 months of physiotherapy. Each participant will have 6 months follow up. This study will help inform a larger clinical trial in the future for which a further ethics application will be made.

Inclusion Criteria:

• Aged ≥18 and ≤ 70 (both males and females)
• Participants with chronic midportion AT (as defined by pain in region of AT and tender swelling in mid portion of AT (no tenderness over bony attachment to heel) with symptoms for longer than 6 months who have failed conservative treatment (at least a full course of physiotherapy) and for whom surgery is being considered
• Able to provide written informed consent

Exclusion Criteria:

• Previous bony surgery (e.g. reconstructive pelvic osteotomy) at or in proximity to the bone marrow harvest site
• Pregnancy or lactation
• Current use of steroids, anti-tumour necrosis factor (TNF) drugs, methotrexate, or ciprofloxacin (or use within 4 weeks of assessment for eligibility)
• Positive for hepatitis B virus (HBV), Hepatitis C virus (HCV), Human Immunodeficiency Virus (HIV 1 and 2), syphilis and human t-cell leukaemia virus (HTLV)
• Previous AT surgery on the tendon to receive mesenchymal stem cell (MSC) implantation
• Inflammatory arthritis
• Known or suspected underlying haematological malignancy
• Other active malignancy in the past 3 years
• Bovine or antibiotic allergy