| Outline
of the Completed Research |
| Clinical Science ＆ Pathobiology |
|
To determine the mechanism of hoof wall degeneration caused by water accumulated in bedding material, the process of water infiltration from the hoof wall cross-section was observed by nuclear magnetic resonance microimaging. Samples of unprocessed normal hoof wall and hoof wall pre-immersed in ultra-pure water, horse urine, ammonia solution or urea solution were used. In the unprocessed hoof wall, amplification of signals proceeded from the water absorptive surface towards the inside. There was a correlation between time-lapse changes in signal intensity in the horn tubules and the intertubular horn, indicating that the infiltration of water could occur in both two parts. In the samples pre-immersed in horse urine, observation up to 24 hours after water absorption revealed that signaling was low compared to those pre-immersed in ultra-pure water, but that amplification of the signal was large in the later stage of the water absorption process. Moreover, in the samples pre-immersed in ammonia solution, images were similar to those of hoof walls processed with horse urine. From these findings, it was suggested that immersion in urine can cause changes in the characteristics of distribution and transfer of water in the hoof wall. Basic study on equine regenerative
medicine using cell growth factor A basic study was conducted on a drug delivery system (DDS) that provides sustained release of the cell growth factor bFGF and its application to equine regenerative medicine. In studies of the restoration effects on a full-thickness skin loss wound model, it was confirmed that blood vessels were quickly induced and the formation of the epithelium was promoted by the use of the DDS. In studies of restoration effects on a model of full-thickness defects of articular cartilage in the equine carpal joint, the expected regeneration of hyaline cartilage was not observed. Conversely, restoration due to granulation tissue of the bone tunnel in carpal bones was superior compared to the control group. Although it became clear from this research that a DDS based on sustained release of bFGF has potential for clinical application, it was thought necessary to reconsider the choice of cell growth factor appropriate for cartilage regeneration. Clinico-pathological study on sports injuries and other disorders in racehorses（2003-2007） Purpose Results 1. We studied the incidence and risk of injury by superficial digital flexor tendonitis and suspensory desmitis that occurred during racing and training over the twelve months of 1999. As a result, the respective rates of incidence were 11.1% and 3.6%. We demonstrated that the risk of injury caused by both diseases increased with age, and was also higher in males. 2. We studied the hoof wall growth rate in laminitic hooves over a year. As a result, the hoof wall growth rate in laminitic hooves was lower than that of normal hooves (the lowest rate recorded being 47% of that of normal horses). We also found that a slowed growth rate can be improved through special farrier techniques whereby the bearing border of the laminitic hoof is raised above the ground level. 3. We studied the impact of differences in bedding under the foot. As a result, it became clear that sawdust and coconut palm husk easily become lodged under the foot when contaminated with urine, and that, as a consequence of this, sawdust and coconut palm husk are more prone to cause hoof wall damage, compared to rice straw. II. Clinico-pathological diagnosis of horse fatalities and diseases of unknown cause 1. We conducted a histopathological study of the healing mechanism of laminitis. As a result, we identified factors such as the point of genesis of lamellar wedge, making it possible to estimate the point when laminitis occurs. We also discovered that there are regions in which the basement membrane zone of the regenerated laminar layer in laminitis does not improve for at least three months, and this was thought to be one cause of the recurrency of laminitis. 2. The pathology of canker was clinically examined. As a result, we proved that bacteria of the genus Treponema are involved in the occurrence of chronic proliferative pododermatitis, and that combined use of surgery with the removal of lesions using sterile maggots is effective in treating canker. 3. We conducted endoscopic examination and histopathological examination on a young racehorse that had contracted a respiratory disorder of unknown cause. As a result, we found that dynamic pharyngeal collapse based on muscle degeneration of the muscles of the pharynx (particularly the stylopharyngeus muscles) had occurred. From this, we confirmed that endoscopic examination of the pharynx is important when diagnosing young horses that contract respiratory disorders. 4. To study the pathology of catheter-induced jugular phlebitis, we experimentally retained a catheter in the jugular vein of a horse for several days and observed changes in the vein tissue. At points that contacted the catheter, acute inflammation consisting principally of eosinophils was recognized, leading to the conjecture that a hypersensitivity reaction to the catheter had occurred. 5.
We carried out pathological examination on a sick horse that
had tumors all over its body, including numerous organs in the
thoracic and abdominal cavities. As a result, these tumors were
recognized to be extremely rare nephroblastomes that had translocated
all over the body. Synovial osteochondromatosis was also observed
inside the hock joint. Establishing a method of evaluating qualitative and structural changes in hoof wall. Collaborative study between Clinical Sciences and Pathobiology Division, Equine Research Institute and John D. REILY, Nottingham University (2004-2005) Despite
pronounced improvements in shoeing technology, such as the increased
use of shoes designed for both training and racing, racehorses
are still forced into frequent layoffs by shoeing difficulties
due to hoof diseases thought to be caused by hoof wall degeneration
(e.g. hoof wall separation). The causes of this are complex
and preventive measures extremely difficult to establish, but
before identifying the cause, The aim of the research was to
establish a method of evaluating dynamic and structural changes
in the hoof wall characteristics and, furthermore, to elucidate
whether or not imposing restricted training in the growth stage
of the hoof causes changes to the tubule density (TD) of horn
tubules in the hoof wall or the modulus of elasticity (ME) of
the hoof wall. After establishing a method of evaluating the
hoof wall using an exercise group subjected to restricted training
and a control group permitted to graze freely, we studied the
impact of exercise on hoof wall characteristics (morphological
and dynamic properties). As a result, we found that restricted
training did not change the thickness of the hoof wall but reduced
tubule density (TD). Meanwhile, on measuring the modulus of elasticity
(ME) of the hoof wall, we found that restricted training had
no impact on ME. Moreover, no significant correlation was found
between TD and ME. From this, it was thought that exercise does
cause changes to the tissue architecture of the hoof wall through
a kind of adaptation, but that exercise does not tend to change
dynamic characteristics. Research on markers for locomotive disorders in racehorses: The usefulness of COMP as a marker for locomotive disorders (2004-2005) Cartilage
Oligometric Matrix Protein (COMP) is a type of glycoprotein that
exists specifically in articular cartilage, synovial membrane
and tendons. In humans, fluctuations in the serum content of
these has already been clinically applied as a disorder marker
for arthritis, and in recent years the possibility of screening
injuries using the volume ratio of various types of COMP fragments
present in synovial fluid has been reported. There is very little
knowledge on equine COMP fragments in the field of veterinary
science. Therefore, in joint work with a British researcher,
we posed the hypothesis that ﾒIn
equine tendinitis and arthritis, different types of COMP fragments
are present in serumﾓ,
and studied the possibility of their clinical application as
markers for locomotive disorders in racehorses. Elucidation of the functions of tendon cells using in vitro culture: Development of an evaluation model for the healing process of tendinitis using culture tendon cells. Commissioned to Katsuhiko ARAI, Department of Tissue Physiology, Tokyo University of Agriculture and Technology (2003-2005) While
clinical tests using actual horses are vital for application
to diagnosis and treatment, developing an alternative to animal
experiments has become an important task for researchers, with
so many problems now emerging in the treatment of experimental
animals. In this research, as an aid to establishing a method
of diagnosis and early cure for tendinitis, we aimed to establish
an experimental model using cultured tendon cells that can reproduce
the pathological state of tendinitis, and to elucidate the molecular
mechanism of occurrence and healing of tendinitis by studying
the characteristics of equine cultured tendon cells under various
conditions. First, as a basic study aimed at developing a healing
evaluation model for tendinitis using cultured tendon cells,
we analyzed the mRNA expression of matrix-related protein in
tendon tissue on occurrence of acute tendinitis, and found strong
expressions of hyaluronidase, MMP-13 matrix metalloproteinase13
and cathepsin D. Meanwhile, we found that, in tendon cells cultured
in relax gel, the expression of the same enzyme genes as in the
affected tendon tissue is reproduced. From the above, we felt
that culture in relax gel is suitable as a cell culture model
that can reflect the pathological state of tendinitis. We also
demonstrated differences in cell properties arising from the
fact that collagen relaxing capacity and the expression of collagen
receptors are lower in cultured cells derived from affected tendons
than in those derived from normal tendons, and proved that the
cytokine reactivity of cultured tendon cells is influenced by
the matrix composition used in culture. |
