Regenerative medicine

in horses

A STUDY conducted in the United States a number of years ago determined that lameness was the most common medical condition that equine veterinarians were asked to investigate by horse owners. The average cost of each lameness examination was approximately $432, which equated to $550 million per annum in the United States alone. There has therefore been significant interest and investment in research focusing on the development and advancement of both diagnostic and therapeutic strategies for equine lameness.

One such area of research is regenerative cell-based therapies. Regenerative cell-based medicine refers to the use of either the body’s own cells, or products from these cells, in the treatment of disease or injury. In general terms, this involves harvesting specific cells from either the injured individual or another horse. These cells are then processed, and the resultant product is typically injected into the damaged region or structure. A variety of cell-based therapies are in existence, and this can often result in confusion. The three treatments used most commonly in current equine practice are outlined below.

ARTHRITIS

Arthritis is a degenerative, inflammatory condition of joints which, results in progressive destruction of the joint cartilage. This results in pain, which is demonstrated outwardly as lameness. The most common cause of arthritis is a previous joint injury.

When a joint is damaged, numerous chemicals are produced by the body that drive the inflammatory process within the joint. One of the major offenders is interleukin-1 (IL-1). IRAP blocks the receptor or docking point for IL-1, and IRAP can therefore slow the progression of arthritis and reduce inflammation, pain and lameness.

IRAP is obtained by harvesting 50ml of the horse’s own blood which is then incubated in a special vial for 24 hours. The blood is then spun in a centrifuge, which separates the IRAP portion from the other blood cells. The resultant IRAP can then be either used immediately or frozen and stored for over one year. IRAP is administered by injecting it directly into the affected joint, but it can also be used for selected tendon and ligament injuries.

HEAD & SPINAL SURGERY

PRP (Platelet Rich Plasma) has been widely used in human medicine for several years in head and spinal surgery, in the treatment of arthritis and for damaged tendons and ligaments. Platelets are cells within the blood that are responsible for clotting the blood, but also contain important chemicals for growth and healing. Once injected, the platelets release large amounts of these growth factors, which stimulate local cells to grow and repair damaged tissue, in addition to attracting stem cells within the body to the damaged area. PRP typically does not speed up healing but improves the quality of repair tissue so that the likelihood of the horse re-injuring the same structure is reduced.

PRP is obtained by harvesting a small amount of the horse’s own blood which is then processed in a specialised centrifuge which separates the platelet component from the other components of the blood sample and concentrates it. This process takes about 15 minutes and the product can either be used immediately or stored and used at a future date. PRP can be used in the treatment of arthritis where it is injected directly into affected joints or into or around damaged tendons or ligaments.

STEM CELLS

Stem cells are by far the best known and most controversial of all cell-based therapies. Stem cells are immature cells in the body that can be stimulated to turn into any other type cell in the body. When the body is injured, stem cells are recruited and form part of the normal healing process. Through research, we are learning to isolate and manipulate these stem cells, with the goal of improving healing of damaged structures or organs.

Stem cells are found in bone marrow, fat, blood vessel walls, tendon, ligament and umbilical cord blood among other places. In adult horses, stem cells for our clinical use are predominantly obtained from harvesting either fat or bone marrow.

For fat-derived stem cells, fat is harvested from around the tail head. This is then shipped to a specialist laboratory where the stem cells are separated from the fat and concentrated. The concentrated fat-derived stem cells are then shipped back to the veterinarian ready for use. Typically, this process takes approximately three days.

Bone marrow derived stem cells are obtained by harvesting bone marrow from either the sternum (breastbone) or hip. The bone marrow is then shipped to a specialist laboratory where the sample is cultured, which greatly increases the number of stem cells in the final product compared to fat-derived stem cells.

Typically the more stem cells present in the sample the better. This process can take anywhere from three to six weeks until the stem cells are ready to be injected back into the horse. A portion of the sample may be stored in a stem cell bank for use at a future date. Currently, there is no conclusive evidence as to which source of stem cells is superior; however, the majority of research suggest that bone marrow derived stem cells are preferable.

A third commercial form of stem cells has recently become available which involves collection of blood from the umbilical cord at the time of birth. These cells are then preserved in liquid nitrogen at -196°C for the duration of the horse’s life and can be accessed at any time. An annual fee is payable to the stem cell bank for storage, and this can be transferred to the new owner if the horse is sold.

Stem cells obtained in this manner are more immature than those obtained from either fat or bone marrow and thus are thought to have a greater ability to transform into the desired various cell types. Umbilical cord blood is a relatively non-invasive source of high-quality stem cells, without the ethical considerations of obtaining stem cells from embryos.

Presently, unlike other medications, there are no rules or regulations governing the use of regenerative cell-based therapies and therefore, it is important that only experienced individuals administer such advanced treatments.

Summarily, cell-based regenerative therapies are still in their infancy and only with the fullness of time and continued research will we be able to exploit their full potential.

Turlough McNally MVB Dip ACVS Dip ECVS MRCVS is a member of the Veterinary Ireland Equine Group and is a specialist in equine surgery at Anglesey Lodge Equine Hospital, The Curragh, Co Kildare

Email: hq@vetireland.ie

Telephone: 01-4577976