Page 925 - Adams and Stashak's Lameness in Horses, 7th Edition

Principles of Therapy for Lameness 891

OA in endurance horses and reported that 80% of horses results suggest that these cells may also have a place in
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were able to return to regular work following treatment. intrasynovial therapies.
VetBooks.ir reported in the human literature. 33–35,40,71,94,96 shown to have a detrimental effect on cell viability, with
The concomitant use of CS and MSCs has been
While largely positive, variable results have also been
both MPA and TA resulting in the rapid death of signifi-
cant numbers of MSCs, and should not be performed.
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AUTOLOGOUS PROTEIN SOLUTION Similar effects have been shown when combining cul-
tured BMSCs with therapeutic concentrations of amino-
Autologous protein solution (APS, Pro‐Stride®) is a glycoside antimicrobials (150‐mg gentamicin or 250‐mg
newly developed, modified blood product generated amikacin), resulting in >95% cell death within 2 hours
from a dual‐device system that concentrates plasma and of incubation. Based on these findings, the co‐injection
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WBC proteins and enriches platelet growth factors. APS of BMSCs and aminoglycoside antimicrobials is not rec-
is meant to achieve the goals of both ACS (IRAP) and ommended. The same study reported minimal effects of
PRP through a two‐step centrifugation process. This HA (22‐mg total dose) on the viability and proliferation
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process separates a small volume of plasma concen- of cultured BMSCs, with a trend noted for mild stimula-
trated with platelets and WBCs, which is then filtered tion and enhanced secretion of immunomodulatory
through polyacrylamide beads to desiccate and further mediators. 18
concentrate growth factors and plasma proteins. Concentrated bone marrow aspirate concentrate
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Additionally, APS can be drawn, processed, and injected (BMAC) is another autologous source of MSCs being
stall side without the need for incubation or processing. investigated for the treatment of OA and regeneration of
A prospective, randomized, placebo‐controlled clini- cartilage in osteochondral defects. While the overall
cal trial that evaluated the efficacy of a single IA injec- concentration of MSCs in BMAC is limited, BMAC also
tion of APS in horses with OA in various high‐motion serves as a source of growth factors important for the
joints found that treated horses had significant improve- induction of chondrogenesis. 64,100,102 BMAC has been
ments in lameness grade, asymmetry indices of vertical shown to improve cartilage healing in horses following
peak force, and range of joint motion by 14 days’ post- microfracture repair of cartilage defects. Horse treated
treatment. In this group of horses, APS had a greater with BMAC had improved structure, matrix composi-
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likelihood of a therapeutic response in horses with a tion, and integration of the cartilage repair tissue into
lameness score <4, <10% vertical force asymmetry, or the surrounding normal cartilage. Overall, similar pos-
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absence of marked osteophyte formation, subchondral itive results have also been published in the human lit-
sclerosis, or joint space narrowing. erature for treating OA in the knee. Although further
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Current research on APS in horses has been limited; work is needed, current evidence suggests that BMAC
however, the benefits described in the previous study has the potential to be an effective, minimally invasive
have been validated in both canines and humans. In a option to help repair cartilage defects and treat OA in
study of 21 dogs with OA of the stifle or elbow, a single the horse.
injection of APS resulted in reduced pain and lameness
scores and increased weight‐bearing associated with the
OA‐affected joint at 12 weeks’ postinjection. A study
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involving 41 human patients that received a single injec- POLYACRYLAMIDE HYDROGEL
tion of APS for knee OA showed significant clinical Polyacrylamide hydrogel (PAAG) is a nontoxic, non‐
improvement in pain scores as well as reduction in bone immunogenic, nondegradable, and biocompatible poly-
marrow lesion size on MRI and osteophyte formation mer gel consisting of 2.5% cross‐linked polyacrylamide
6–12 months after injection. 72 with a long‐lasting viscous effect shown to support cel-
lular growth and augment tissues. This product has
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historically been used as a bulking agent to enhance soft
BONE MARROW‐ OR FAT‐DERIVED tissue integrity in human medicine. 16,86,88 Just recently
MESENCHYMAL STEM CELL THERAPY approved for use by veterinarians in the United States,
PAAG has been a newly investigated therapeutic option
The use of bone marrow‐derived mesenchymal stem for treating OA in horses.
cells (BMSCs) or fat‐derived mesenchymal stem cells An international multicenter study that evaluated the
(MSCs) has grown in popularity in equine practice in efficacy of IA PAAG in horses with OA showed that
the last decade. It is believed that these cells possess PAAG significantly alleviated lameness and joint effu-
anti‐inflammatory properties and may also contribute sion, with 59% of horses sound 1 month after treat-
to healing of musculoskeletal tissues by becoming ment. Improvement in the number of non‐lame horses
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incorporated into the repair tissue. A recent retrospec- and reduction in joint effusion were observed over
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tive study of 40 horses that received IA injection of time, with 82.5% of horses sound after 24 months.
BMSCs that had been expanded to approximately Furthermore, the effect of treatment increased over time
10–20 million cells revealed a return to athleticism in with no significant side effects observed in treated joints.
72% of all horses with IA injuries, ranging from mild to A comparative prospective study by the same author
severe. IA administration of BMSCs postoperatively also demonstrated that horses with OA treated with
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for stifle lesions has also been reported in horses, with PAAG had significantly improved clinical signs when
improved ability to return to work (75%). Although compared with horses treated with TA combined with
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more is known regarding the efficacy of MSCs in ten- sodium HA. A preliminary field trial that evaluated
don injuries compared with synovial disease, early the efficacy of a 4% PAAG in osteoarthritic horses