Effects of recombinant equine growth hormone on in vitro biomechanical properties of the superficial digital flexor tendon of Standardbred yearlings in training

OBJECTIVE: To determine whether recombinant equine growth hormone (rEGH) would alter the in vitro biomechanical properties of the forelimb superficial digital flexor tendon (SDFT) in exercising young Standardbred horses. STUDY DESIGN: Randomized complete block design. ANIMALS: Twelve Standardbred yearlings. METHODS: Horses were trained for 12 weeks on a high-speed treadmill (10% positive incline). rEGH was administered intramuscularly (IM) daily (10 microg/kg during week 4; 20 microg/kg for weeks 5-9) to 6 horses (treated group), whereas 6 horses (control group) were administered an equivalent daily volume of sterile water IM. At 12 weeks, horses were euthanatized and left forelimb SDFTs were collected and stored (-70 degrees C). A section from the mid-region of the SDFT was held in cryoclamps with a 4 cm interspace distance and distracted at 10 mm/s until failure. The variables evaluated were maximal load at yield and failure, ultimate and yield tensile stress and strain, tendon stiffness, and mode of failure. Data were analyzed using unpaired, two-tailed, Student's t-test. Statistical significance was set at P < or =.05. RESULTS: Yield and ultimate tensile stress were significantly lower in the rEGH-treated horses compared with controls. There was a trend toward increased maximal displacement, increased ultimate tensile strain, and decreased tendon stiffness in rEGH-treated horses compared with controls. Tensile stress and cross-sectional area, and tensile stress and stiffness were significantly correlated at yield and failure points. CONCLUSIONS: rEGH, administered at the manufacturer's recommended dose rates to maturing Standardbred horses in training, does not significantly augment the in vitro biomechanical properties of the forelimb SDFT. CLINICAL RELEVANCE: Administration of rEGH to young horses in training is unlikely to enhance the physiologic adaptation of the SDFT to exercise stress.     

The effect of recombinant equine growth hormone on the biomechanical properties of healing superficial digital flexor tendons in horses

OBJECTIVE: To evaluate the effect of recombinant equine growth hormone (rEGH) on the in vitro biomechanical properties of healing superficial digital flexor tendon (SDFT) in horses. STUDY DESIGN: Completely randomized design. SAMPLE POPULATION: Twelve Standardbred horses, 3 to 7 years of age, with ultrasonographically normal forelimb SDFT. METHODS: One week after induction of collagenase (2,000 U) induced superficial flexor tendonitis, horses were randomly divided into groups of 6. One group was administered intramuscular rEGH (10 microg/kg/day for 1 week, then 20 microg/kg/day for 5 weeks), whereas the other group (control subjects) were administered an equivalent volume of saline (0.9% NaCl) solution. At the end of this 6-week treatment, horses were killed and one forelimb SDFT from each horse was harvested for biomechanical testing under uniaxial tension. Results were analyzed using an unpaired Student's t test; significance was set at P 相似文献   

The effect of equine recombinant growth hormone on second intention wound healing in horses

OBJECTIVE: To evaluate the effect of intramuscular administration of recombinant equine growth hormone on healing of full thickness skin wounds on equine limbs. STUDY DESIGN: Experimental. ANIMALS: Nine Standardbred horses. METHODS: In study 1, standardized full thickness skin wounds (2.5 x 2.5 cm) were made over the dorsomedial aspect of the mid-cannon bone of 1 forelimb and 1 hindlimb in 9 horses. Wounds were bandaged without treatment (control subjects) and videorecorded twice weekly until healed. Then, in study 2, similar wounds were created on the opposite limbs; 6 horses were administered intramuscular recombinant equine growth hormone (10 microg/kg daily for 7 days, then 20 microg/kg daily for 49 days), and 3 horses (control subjects) were administered equivalent volumes of sterile water. Wounds were videorecorded twice weekly until healed. Wound healing variables were measured from the videorecordings using a computer software package and analyzed as a randomized complete block design factorial analysis of variance; significance was set at P <.05. RESULTS: No differences in the measured variables were detected between wounds in study 1 and the control wounds in study 2. In recombinant equine growth hormone-treated horses, wounds retracted more during treatment and contracted faster after treatment stopped when compared with wounds from untreated horses. No other treatment effects were detected. CONCLUSIONS: Recombinant equine growth hormone seemingly increases wound retraction. After treatment ceases, wound contraction increases. CLINICAL RELEVANCE: Intramuscular administration of recombinant equine growth hormone (10 microg/kg daily for 7 days, then 20 microg/kg daily for 49 days) does not appear to have any beneficial clinical effect on healing of equine limb wounds.     

Influence of topically applied cold treatment on core temperature and cell viability in equine superficial digital flexor tendons

OBJECTIVE: To determine rate and degree of cooling for the superficial digital flexor tendon (SDFT) during a standard cryotherapy application in horses and evaluate in vitro effects of cooling on survival of tendon cells. SAMPLE POPULATION: 6 limbs of 5 adult horses and cultured cells obtained from SDFT of 3 adult horses during necropsy. PROCEDURE: In vivo data were acquired by use of a thermocouple temperature probe inserted into the SDFT of a forelimb of each standing sedated horse. After baseline temperatures were recorded, a commercial compression splint with circulating coolant was placed on each selected limb, which was then exposed to cold treatment for 60 minutes. Temperatures were recorded at 30-second intervals. Mean minimum core temperature was calculated and used to design a protocol for in vitro cold treatment of cells. Specimens were obtained from the SDFT of horses during necropsy; tendon cells were cultured in suspension and exposed to 1-hour of cold treatment that mimicked the in vivo procedure. Viability of cells after cold treatment was compared with viability of cells maintained at body temperature. RESULTS: After 1 hour of cold treatment, SDFT core temperature was reduced by a mean of 21.8 degrees C, reaching a mean minimum temperature of 10 degrees C. Viability did not differ significantly between cold-treated and control cells. CONCLUSION AND CLINICAL RELEVANCE: Results indicated that topical application of cryotherapy significantly reduced core SDFT temperature in standing sedated horses. Temperatures achieved in vivo during cold treatment were not detrimental to the in vitro viability of tendon cells.     

An in vitro biomechanical comparison of a prototype intramedullary pin-plate with a dynamic compression plate for equine metacarpophalangeal arthrodesis

OBJECTIVES : To compare the biomechanical properties of a prototype intramedullary pin-plate (IMPP) implant specifically designed for equine metacarpophalangeal (MCP) arthrodesis with a dynamic compression plate (DCP) system. STUDY DESIGN : In vitro biomechanical testing of paired cadaveric equine forelimbs with a simulated traumatic disruption of the suspensory apparatus, stabilized by one of two methods for MCP arthrodesis. ANIMAL POPULATION : Twenty-one pairs of adult equine cadaveric forelimbs. METHODS : Each forelimb had the distal sesamoidean ligaments severed to create a disrupted suspensory apparatus. For each forelimb pair, the MCP joint was stabilized with the IMPP in one limb, and a DCP in the other limb. Seven matching limb pairs were tested in axial compression in a single cycle to failure, 7 matching limb pairs were tested in torsion in a single cycle to failure, and 7 matching limb pairs were fatigued tested in axial compression. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS : The mean yield load, yield stiffness, and failure load (axial compression, torsional loading) was significantly greater for the IMPP compared with the DCP system. Mean cycles to failure for axial compression was significantly greater for the IMPP compared with the DCP system. Significance in all tests was P<.0001. CONCLUSION : The IMPP was superior to the DCP system in resisting the biomechanical forces most likely to cause failure of MCP joint arthrodesis. CLINICAL RELEVANCE : The IMPP implant should be considered for MCP arthrodesis in horses with traumatic disruption of the suspensory apparatus. The specific design of the IMPP implant may facilitate equine MCP arthrodesis and avoid convalescent complications related to cyclic fatigue.     

Limb loading activity of adult horses confined to box stalls in an equine hospital barn

OBJECTIVE: To determine a range of limb loading activity for healthy adult horses confined to box stalls in an equine veterinary teaching hospital and determine the effects of hospital environmental factors on load rates and daily limb loading patterns. ANIMALS: 6 mature healthy horses of various ages, breeds, and sexes, and 1 horse with a repaired metatarsal fracture. PROCEDURE: Step monitors were placed on 2 limbs of adult horses confined to box stalls. Relocation steps and weight shifts were recorded, as loading events, for 24 hours. Influence of forelimb versus hind limb and environmental factors on load rate (loading events per hour) were assessed with repeated-measures ANOVA. RESULTS: Loading activity was greater for the forelimb than the hind limb and was greater during the day than the night. Loading activity differences were not associated with daytime environmental factors. CONCLUSIONS AND CLINICAL RELEVANCE: Horses with normal locomotor activity appear to have higher load rates for forelimbs compared with hind limbs and higher load rates during the day compared with night. Knowledge of influence of environmental factors and mechanical restraint on limb loading activity may be useful in management of horses with musculoskeletal disorders. This information may also be used for in vitro simulation of in vivo loading of limbs during cyclic biomechanical investigations.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 4. Morphometric, microscopic and biomechanical properties of the digital tendons of the forelimb

AIM: To determine the weight, volume, density and cross-sectional area (CSA) of the digital flexor tendons, common digital extensor tendon (CDET) and suspensory ligament (SL) of the forelimb of young Thoroughbred horses in early training, and to assess the response to a training programme of known parameters of superficial digital flexor tendon (SDFT) tissue at mid-metacarpal level. METHODS: The tendons of seven 2-year-old Thoroughbred horses in training were inspected, transected into segments of known length, and compared with those from seven untrained horses matched for age, sex and breed. The weight, volume, density and CSA of each segment, and the crimp angle, histological features, and biomechanical ultimate stress and stiffness of tendon samples from the mid-metacarpal region of the SDFT were determined. RESULTS: There was no macroscopic evidence of swelling or discolouration in any of the tendon segments or cut surfaces. The volumes of SDFT and CDET segments of horses in the trained group were significantly greater than those in the untrained group (p=0.036 and p=0.039, respectively). A greater increase in volume than weight resulted in a lower density in the SDFT but not CDET in trained compared with untrained horses (p=0.038). CSA of these two tendons was significantly greater in the trained group (p=0.002 and 0.036, respectively), the percentage increase being greater in the CDET than the SDFT. The number of tenocytes at four sites in the mid-metacarpal SDFT region was less in trained than untrained horses (p=0.025). There was no histological evidence of inflammation, and no difference in crimp angle between groups. There was no significant between-group difference in stiffness or ultimate stress of tendon strips. CONCLUSIONS: Volume and CSA of the SDFT and CDET were larger in trained than untrained horses. The SDFT was less dense in the trained group. Because no evidence of tendonitis was detected and training appeared to have no significant effect on crimp angle or biomechanical properties of tendon strips, the size and density changes were presumed to be adaptive and induced by the training. CLINICAL RELEVANCE: Although evident in this in vitro study, the detection of adaptive from initial pathological increase in size of the SDFT is likely to be difficult in vivo.     

An in vitro biomechanical investigation of an equine interlocking nail

OBJECTIVE: To determine the mechanical properties of Equine Interlocking Nail (EIN; JD Wheat Veterinary Orthopedic Research Laboratory, University of California, Davis) stabilized osteotomized tibiae and compare these variables with estimated in vivo loads. STUDY DESIGN: In vitro biomechanical investigation. ANIMALS: Twelve adult equine cadaveric tibiae. SAMPLE POPULATION: EIN-stabilized tibiae were tested monotonically under compression, 3- and 4-point bending, and torsion. Mechanical properties were compared with estimated in vivo loads. RESULTS: EIN-tibial composite mean compressive yield load (11 kN) and bending moment (216 Nm) were greater than loads expected postoperatively in vivo; however, the mean torsional yield load (156 Nm) was less than that expected in vivo. CONCLUSIONS: EIN-stabilized tibiae had compressive and bending strengths greater than those expected to maintain stability during walking in adult horses. Torsional yield strength did not appear sufficient to provide stability during walking in vivo. CLINICAL RELEVANCE: The EIN is not a feasible method of fracture repair for adult equine tibial fractures at this time, because its mechanical properties appear inadequate to withstand the postoperative torsional loads encountered during walking. Because this method of fracture repair may offer biological advantages, further modification of an interlocking nail for adult horses appears warranted.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 4. Morphometric,microscopic and biomechanical properties of the digital tendons of the forelimb

AIM: To determine the weight, volume, density and cross-sectional area (CSA) of the digital flexor tendons, common digital extensor tendon (CDET) and suspensory ligament (SL) of the forelimb of young Thoroughbred horses in early training, and to assess the response to a training programme of known parameters of superficial digital flexor tendon (SDFT) tissue at mid-metacarpal level.

METHODS: The tendons of seven 2-year-old Thoroughbred horses in training were inspected, transected into segments of known length, and compared with those from seven untrained horses matched for age, sex and breed. The weight, volume, density and CSA of each segment, and the crimp angle, histological features, and biomechanical ultimate stress and stiffness of tendon samples from the mid-metacarpal region of the SDFT were determined.

RESULTS: There was no macroscopic evidence of swelling or discolouration in any of the tendon segments or cut surfaces. The volumes of SDFT and CDET segments of horses in the trained group were significantly greater than those in the untrained group (p=0.036 and p=0.039, respectively). A greater increase in volume than weight resulted in a lower density in the SDFT but not CDET in trained compared with untrained horses (p=0.038). CSA of these two tendons was significantly greater in the trained group (p=0.002 and 0.036, respectively), the percentage increase being greater in the CDET than the SDFT. The number of tenocytes at four sites in the mid-metacarpal SDFT region was less in trained than untrained horses (p=0.025). There was no histological evidence of inflammation, and no difference in crimp angle between groups. There was no significant between-group difference in stiffness or ultimate stress of tendon strips.

CONCLUSIONS: Volume and CSA of the SDFT and CDET were larger in trained than untrained horses. The SDFT was less dense in the trained group. Because no evidence of tendonitis was detected and training appeared to have no significant effect on crimp angle or biomechanical properties of tendon strips, the size and density changes were presumed to be adaptive and induced by the training.

CLINICAL RELEVANCE: Although evident in this in vitro study, the detection of adaptive from initial pathological increase in size of the SDFT is likely to be difficult in vivo.     

Tendonitis of branches of the superficial digital flexor tendon in Standardbred racehorses: 15 cases

This case report describes the clinical and ultrasonographic findings and performance outcome of distal tendonitis of the superficial digital flexor tendon (SDFT) in Standardbred racehorses. Cases with distal tendonitis of the SDFT in isolation (not associated with a metacarpal lesion) were reviewed retrospectively. The clinical and ultrasonographic findings and performance outcome were reviewed. The injury was located on the left forelimb in 67% (10/15) of horses and on the right forelimb in 33% (5/15). None of the horses were affected bilaterally. The lateral branch was involved in 80% of the cases (12/15) and medial branch in 20% (3/15). None of the horses were affected biaxially. Mean time between injury and first start ± s.d. was 302 ± 142 days. Returning to racing was observed in 93% of the horses (14/15), with a reinjury rate of 22% (2/9). For horses which raced after the injury, the number of starts, shows and wins was not significantly different before and after injury, regardless of the location of the lesion. Tendonitis of branches of the SDFT in isolation carries a good prognosis in Standardbred racehorses. A higher return to racing and a lower reinjury rate may be expected compared to lesions in the metacarpal region.     

In vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: prototype equine spoon plate versus axially positioned dynamic compression plate and two abaxial transarticular cortical screws inserted in lag fashion

Objectives— To compare in vitro monotonic biomechanical properties of an equine spoon plate (ESP) with an axial 3‐hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws (DCP‐TLS) inserted in lag fashion for equine proximal interphalangeal (PIP) joint arthrodesis. Study Design— Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. Animal Population— Cadaveric adult equine forelimbs (n=18 pairs). Methods— For each forelimb pair, 1 PIP joint was stabilized with an ESP (8 hole, 4.5 mm) and 1 with an axial 3‐hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion. Six matching pairs of constructs were tested in single cycle to failure under axial compression with load applied under displacement control at a constant rate of 5 cm/s. Six construct pairs were tested for cyclic fatigue under axial compression with cyclic load (0–7.5 kN) applied at 6 Hz; cycles to failure were recorded. Six construct pairs were tested in single cycle to failure under torsional loading applied at a constant displacement rate (0.17 radians/s) until rotation of 0.87 radians occurred. Mean values for each fixation method were compared using a paired t‐test within each group with statistical significance set at P<.05. Results— Mean yield load, yield stiffness, and failure load for ESP fixation were significantly greater (for axial compression and torsion) than for DCP‐TLS fixation. Mean (± SD) values for the ESP and DCP‐TLS fixation techniques, respectively, in single cycle to failure under axial compression were: yield load 123.9 ± 8.96 and 28.5 ± 3.32 kN; stiffness, 13.11 ± 0.242 and 2.60 ± 0.17 kN/cm; and failure load, 144.4 ± 13.6 and 31.4 ± 3.8 kN. In single cycle to failure under torsion, mean (± SD) values for ESP and DCP‐TLS, respectively, were: stiffness 2,022 ± 26.2 and 107.9 ± 11.1 N m/rad; and failure load: 256.4 ± 39.2 and 87.1 ± 11.5 N m. Mean cycles to failure in axial compression of ESP fixation (622,529 ± 65,468) was significantly greater than DCP‐TLS (95,418 ± 11,037). Conclusion— ESP was superior to an axial 3‐hole narrow DCP with 2 abaxial transarticular screws inserted in lag fashion in resisting static overload forces and cyclic fatigue. Clinical Relevance— In vitro results support further evaluation of ESP for PIP joint arthrodesis in horses. Its specific design may provide increased stability without need for external coaptation support.     

Histological and biomechanical effects of palatal sclerotherapy in the horse using sodium tetradecyl sulfate

Palatal sclerotherapy using sodium tetradecyl sulfate has been suggested as a treatment for dorsal displacement of the soft palate in young Standardbred horses. The present study evaluated histological and biomechanical changes in the equine soft palate following trans-endoscopic treatment with a low dose of this compound. Two horses were euthanased and examined at 2 weeks and at 1, 2, 4 and 6 months post-sclerotherapy, while two further horses served as untreated controls. The technique was easily performed in all cases without major complications. On histological examination there was no evidence of palatal necrosis, inflammation or fibrosis in any of the treated or control animals. There was no variation in the density of palatal connective tissue between individuals, and on biomechanical assessment no significant difference in the stiffness of the palatal tissue was found between treated and control horses at any time. The lower dose of sodium tetradecyl sulfate used in this study relative to previous reports, might explain the absence of tissue alterations. This method of sclerotherapy did not alter the morphology or biomechanical properties of normal equine soft palates.     

Functional adaptation through changes in regional biochemical characteristics during maturation of equine superficial digital flexor tendons

OBJECTIVE: To quantify and compare biochemical characteristics of the extracellular matrix (ECM) of specimens harvested from tensional and compressive regions of the superficial digital flexor tendon (SDFT) of horses in age classes that include neonates to mature horses. SAMPLE POPULATION: Tendon specimens were collected on postmortem examination from 40 juvenile horses (0, 5, 12, and 36 months old) without macroscopically visible signs of tendonitis. PROCEDURE: Central core specimens of the SDFT were obtained with a 4-mm-diameter biopsy punch from 2 loaded sites, the central part of the mid-metacarpal region and the central part of the mid-sesamoid region. Biochemical characteristics of the collagenous ECM content (ie, collagen, hydroxylysylpyridinoline crosslink, and pentosidine crosslink concentrations and percentage of degraded collagen) and noncollagenous ECM content (percentage of water and glycosaminoglycans, DNA, and hyaluronic acid concentrations) were measured. RESULTS: The biochemical composition of equine SDFT was not homogeneous at birth with respect to DNA, glycosaminoglycans, and pentosidine concentrations. For most biochemical variables, the amounts present at birth were dissimilar to those found in mature horses. Fast and substantial changes in all components of the matrix occurred in the period of growth and development after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Unlike cartilage, tendon tissue is not biochemically blank (ie, homogeneous) at birth. However, a process of functional adaptation occurs during maturation that changes the composition of equine SDFT from birth to maturity. Understanding of the maturation process of the juvenile equine SDFT may be useful in developing exercise programs that minimize tendon injuries later in life that result from overuse.     

In vitro cyclic biomechanical properties of an interlocking equine tibial nail

OBJECTIVE: To determine cyclic biomechanical properties of gap osteotomized adult equine tibiae stabilized with an equine interlocking nail (EIN). STUDY DESIGN: In vitro experimental biomechanical investigation. SAMPLE POPULATION: Thirteen adult equine cadaveric tibiae. METHODS: Adult equine tibiae with transverse, midshaft, 1-cm gap osteotomies, stabilized with an equine interlocking nail, underwent cyclic biomechanical testing in vitro under axial compression, 4-point bending, and torsion. Different specimens were subjected to different load levels that represented estimated in vivo loads at 2 Hz for 740,000 cycles. Fatigue life and gap strain were calculated. RESULTS: Compression and bending, but not torsional, fatigue life were longer than time necessary for bone healing. Compressive, but not bending or torsional, gap strains were small enough to be compatible with fracture healing by primary bone formation. Gap strains for compressive, bending, and torsional loads were compatible with indirect, or secondary, bone formation. CONCLUSIONS: Further modification should be made to the equine interlocking nail to increase bending stiffness and torsional fatigue life. CLINICAL RELEVANCE: The stainless steel equine intramedullary interlocking nail is unlikely to provide appropriate long-term stability for fracture healing in adult equine tibiae without modifications in the nail design and material.     

The occurrence of equine arteritis virus in Australia

This paper reports the first isolation of equine arteritis virus (EAV) in Australia and serological evidence of exposure to EAV in Australian horses. Twelve Standardbred stallions imported from North America were found to shed EAV in semen. One hundred and seven stallions were tested for serum antibodies to EAV and 73% of Standardbred stallions tested were seropositive as compared to 8% of Thoroughbred stallions. Serum antibody was detected in 71% of Standardbred mares, 6% of Standardbred racehorses and 1% of Thoroughbred mares and racehorses. Examination of stored serums demonstrated that EAV had been present in Australia since at least 1975.     

Extracellular matrix composition of the equine superficial digital flexor tendon: relationship with age and anatomical site

The objectives of the present study were to test the hypotheses that: (1) the composition of the extracellular matrix of the equine superficial digital flexor tendon (SDFT) shows great functional similarities with articular cartilage, i.e. that significant differences exist in biochemical composition of differently loaded areas (which in the case of tendons may be more apparent as tendon shows more obvious differences than cartilage); and (2) that, as in articular cartilage, no substantial alterations in biochemical composition take place during ageing once adulthood has been attained. Tendon samples were taken from 60 adult slaughter horses from a central area at cross-section in the mid-metacarpal region and at the height of the proximal sesamoid bones (sesamoid region) of the SDFT. Contents of collagenous and non-collagenous components were determined. None of the parameters were correlated with age in either region, except for a significant increase in pentosidine cross-links with age in the sesamoid region. Between the two anatomical regions, there were significant differences in all variables, except for hydroxylysylpyridinoline cross-links. It was concluded that in the equine SDFT, similar to articular cartilage, most molecular parameters are not influenced by age in mature horses, indicating a low remodelling rate. Tendon composition is clearly different between regions, apparently reflecting different specific modes of biomechanical loading at the points sampled.     

Microdamage in the equine superficial digital flexor tendon

The forelimb superficial digital flexor tendon (SDFT) is an energy-storing tendon that is highly susceptible to injury during activities such as galloping and jumping, such that it is one of the most commonly reported causes of lameness in the performance horse. This review outlines the biomechanical and biothermal effects of strain on the SDFT and how these contribute to the accumulation of microdamage. The effect of age-related alterations on strain response and subsequent injury risk is also considered. Given that tendon is a slowly healing and poorly regenerative tissue, prompt detection of early stages of pathology in vivo and timely adaptations to training protocols are likely to have a greater outcome than advances in treatment. Early screening tools and detection protocols could subsequently be of benefit in identifying subclinical signs of degeneration during the training programme. This provides an opportunity for preventative strategies to be implemented to minimise incidences of SDFT injury and reduce recovery periods in elite performance horses. Therefore, this review will focus on the modalities available to implement early screening and prevention protocols as opposed to methods to diagnose and treat injuries.     

Characterization and clinical application of mesenchymal stem cells from equine umbilical cord blood

Tendinitis of the superficial digital flexor tendon (SDFT) is a significant cause of lameness in horses; however, recent studies have shown that stem cells could be useful in veterinary regenerative medicine. Therefore, we isolated and characterized equine umbilical cord blood mesenchymal stem cells (eUCB-MSCs) from equine umbilical cord blood obtained from thoroughbred mares during the foaling period. Horses that had tendinitis of the SDFT were treated with eUCB-MSCs to confirm the therapeutic effect. After eUCB-MSCs transplantation, the core lesion in the SDFT was found to decrease. These results suggest that transplantation using eUCB-MSCs could be another source of cell treatment.     

Effects of platelet-derived growth factor-BB on the metabolic function and morphologic features of equine tendon in explant culture

OBJECTIVE: To evaluate the effects of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on the metabolic function and morphologic features of equine superficial digital flexor tendon (SDFT) in explant culture. Animals-6 euthanized horses (2 to 5 years old). METHODS: Forelimb SDFT explants were cultured for 6 days as untreated control specimens or treated with rhPDGF-BB (1, 10, 50, or 100 ng/mL of medium). Treatment effects on explant gene expression were evaluated via real-time PCR analysis of collagen type I, collagen type III, PDGF-A, and PDGF-B mRNA. Explants were assayed for total collagen, glycosaminoglycan, and DNA content; histologic changes were assessed via H and E staining and immunohistochemical localization of collagen types I and III. RESULTS: No morphologic or proliferative changes were detected in tendon explant sections. After high-dose rhPDGF-BB treatment, gene expression of collagen types I and III was increased and decreased, respectively. Expression of PDGF-A and PDGF-B mRNA was significantly increased at 24 hours, but later decreased to have few or negative autoinductive effects. Although PDGF gene expression waned after 48 hours of culture, collagen type I gene expression was significantly increased at 48 hours and reached peak value on day 6. Glycosaminoglycan and DNA content of explants were unchanged with rhPDGF-BB treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that rhPDGF-BB use may be of benefit in the repair of equine tendon, particularly through induction of collagen type I mRNA. Positive autoinductive effects of PDGF-BB in equine SDFT explants were detected early following culture medium supplementation, but these diminished with time.     

Evaluation of the induction of vasoactive mediators from equine digital vein endothelial cells by endotoxin

OBJECTIVE: To determine the effect of endotoxin (lipopolysaccharide [LPS]) on vasoactive mediator production by cultured equine digital vein endothelial cells (EDVECs). SAMPLE POPULATION: EDVECs obtained from forelimb digital veins of 7 healthy adult horses. PROCEDURES: EDVECs were incubated with or without LPS (1 microg/mL) for 0, 2, 4, 6, 22, and 24 hours. The EDVECs were incubated for 18 hours with LPS (10 pg/mL to 1 microg/mL) with or without ibuprofen, cycloheximide, or L-nitroarginine methyl ester. Medium concentrations of prostacyclin, cyclic guanosine monophosphate, endothelin-1, and thromboxane A(2) were determined. Changes in inducible nitric oxide synthase and cyclooxygenase-2 expression were determined. RESULTS: LPS stimulated mean 4.2- and 14.1-fold increases in EDVEC prostacyclin and cyclic guanosine monophosphate production, respectively, after 22 hours. These effects were LPS concentration-dependent (LPS concentrations that induced a response halfway between the maximum response and baseline of 1.50 and 1.22 ng/mL, respectively). The LPS-induced cyclic guanosine monophosphate production was significantly inhibited (to basal concentrations) by L-nitroarginine methyl ester, and prostacyclin production was inhibited by cycloheximide and ibuprofen. Production of thromboxane A(2) by EDVECs was not detected. Endothelin-1 accumulated in the medium, but LPS did not enhance its production. Inducible nitric oxide synthase expression in EDVECs was not detected with the available antibodies, whereas LPS stimulated cyclooxygenase-2 expression in a time- and concentration-dependent manner. CONCLUSIONS AND CLINICAL RELEVANCE: LPS stimulated vasoactive mediator production by equine endothelial cells, which may play a role in LPS-induced digital hypoperfusion.