In recent years there have been advancements in the use of biological therapies for musculoskeletal disease. Things such as
IRAP, PRP and stem cells are now commonly used in horses. The goal of this presentation is to review the results of studies
that have justified its use in horses and how these are used clinically.
IRAP, or Interleukin-1 Receptor Antagonist is commercially known as autologous condition serum, and relies on the production
of IRAP from the horse's own blood. IRAP is known to inhibit the effects of Interleukin-1, which is a critical factor in the
inflammatory cascade of joints. Clinically, blood is withdrawn from the horse into special syringes, which must be transported
to a specially-equipped laboratory for preparation. The IRAP is then filtered and frozen for intraarticular administration.
Currently it is recommended to use IRAP once weekly for 3 treatments, but we have also been using it monthly for horses with
chronic, low-grade arthritic conditions. Experimental results show that IRAP decreased clinical lameness and inflammatory
changes within synovial membrane. At this time although interleukin-1 receptor antagonist has been found in the IRAP preparation,
there is growing evidence that other growth factors are involved as well.
Stem cells are now being used in joints without much objective information to justify its use. Commercially, there are two
sources of "stem cells" that are in use. Fat based stem cells have been commercially available for several years, and the
method basically extracts the vascular fraction from that tissue. It is unclear whether these are truly mesenchymal cells,
although there is some clinical evidence that they can be beneficial for healing of soft tissue injuries such as tendon and
ligament disease. Bone marrow derived stem cells have recently come on the market. Bone marrow is harvested from the horse
and then cells are grown in culture for several weeks. These expanded cells are then reinjected either into the tissue or
into the joint to help facilitate healing. As of now, the only objective data in horses does not support its use, as it had
little disease-or symptom-modifying effects in horses with experimental osteoarthritis. However, anecdotally, there have been
cases which have improved after treatment. There is also clinical evidence horses with meniscal lesions can respond favorably
to bone marrow derived stem cells.
Platelet-rich plasma has also come on the market in recent years. The theory for its use is that platelets contain growth
factors that can help stimulate repair of tissues. There is some clinical and experimental evidence to suggest that it can
help with healing soft tissues such as tendons and ligaments. Currently, I find this treatment to be beneficial for soft tissue
lesions, in particular proximal suspensory desmitis lesions. It can be used both intralesionally as well as around the area
in order to help facilitate healing.
Although it is rare to have reactions to these medications, there have been occasions where horses have become quite reactive
after injection. It is unknown what the cause of this is and it is a good idea to warn the owners prior to treatment that
this is likely to happen. In our experience even when a horse flares to theses medications they do respond well to conservative
therapy with systemic antiinflammatory treatment.
The use of biological therapies for musculoskeletal disease is a continuing trend and it is likely that other biological based
treatment will be commercially available in the near future.