Objective—To determine the effects of phenylbutazone
(PBZ) on bone activity and bone formation in
Animals—12 healthy 1- to 2-year-old horses.
Procedures—Biopsy was performed to obtain unicortical
bone specimens from 1 tibia on day 0 and
from the contralateral tibia on day 14. Fluorochromic
markers were administered IV 2 days prior to and on
days 0, 10, 15, and 25 after biopsy was performed.
Six horses received PBZ (4.4 mg/kg of body weight,
PO, q 12 h) and 6 horses were used as controls. All
horses were euthanatized on day 30 and tissues from
biopsy sites, with adjacent cortical bone, were collected.
Osteonal density and activity, mineral apposition
rate (MAR), and percentage of mineralized tissue
filling the biopsy-induced defects in cortical bone
were assessed. Serum samples from all horses were
analyzed for bone-specific alkaline phosphatase activity
and concentration of PBZ.
Results—MAR was significantly decreased in horses
treated with PBZ. Regional acceleratory phenomenon
was observed in cortical bone in both groups but was
significantly decreased in horses treated with PBZ.
Osteonal activity was similar at all time points in all
horses. In control horses, percentage of mineralized
tissue filling the cortical defects was significantly
greater in defects present for 30 days, compared with
defects present for 14 days. Differences in percentage
of mineralized tissue were not detected in horses treated
Conclusions and Clinical Relevance—PBZ
decreased MAR in cortical bone and appeared to
decrease healing rate of cortical defects in horses.
(Am J Vet Res 2000;61:537–543)
Objective—To isolate and characterize bone marrow–derived equine mesenchymal stem cells (MSCs) for possible future therapeutic applications in horses.
Sample Population—Equine MSCs were isolated from bone marrow aspirates obtained from the sternum of 30 donor horses.
Procedures—Cells were cultured in medium (alpha-minimum essential medium) with a fetal calf serum content of 20%. Equine MSC features were analyzed to determine selfrenewing and differentiation capacity. For potential therapeutic applications, the migratory potential of equine MSCs was determined. An adenoviral vector was used to determine the transduction rate of equine MSCs.
Results—Equine MSCs can be culture-expanded. Equine MSCs undergo cryopreservation in liquid nitrogen without altering morphologic characteristics. Furthermore, equine MSCs maintain their ability to proliferate and differentiate after thawing. Immunocytochemically, the expression of the stem cell marker CD90 can be detected on equine MSCs. The multilineage differentiation potential of equine MSCs was revealed by their ability to undergo adipogenic, osteogenic, and chondrogenic differentiation.
Conclusions and Clinical Relevance—Our data indicate that bone marrow–derived stromal cells of horses can be characterized as MSCs. Equine MSCs have a high transduction rate and migratory potential and adapt to scaffold material in culture. As an autologous cell population, equine MSCs can be regarded as a promising cell population for tissue engineering in lesions of the musculoskeletal system in horses.