Objective—To clone full-length equine pigment epithelium-derived factor (PEDF) complementary DNA (cDNA) and to evaluate its temporal expression during repair of wounds in horses.
Animals—4 clinically normal 2-to 3-year-old Standardbred mares.
Procedures—Full-length equine PEDF cDNA was cloned by screening size-selected cDNA libraries derived from biopsy specimens obtained from the wound edge 7 days after experimental creation of a 6.25-cm2 full-thickness wound in the skin of the lateral thoracic wall. Expression was evaluated in normal skin and in biopsy specimens obtained weekly from experimentally induced wounds on the trunk and limbs of horses. Temporal gene expression was determined by use of reverse transcriptase PCR assay.
Results—Equine PEDF shared 87% sequence and 88% peptide homology with human PEDF. Wounding caused upregulation of PEDF mRNA, which did not return to baseline by the end of the study in either anatomic location. Relative overexpression was evident in wounds on the trunk, compared with expression for wounds on the limbs.
Conclusions and Clinical Relevance—This study characterized full-length equine cDNA for PEDF and determined that the gene for PEDF appeared to be upregulated in response to dermal wounding. Although the cause of exuberant granulation tissue is probably multifactorial, these data suggested that PEDF, via its potent antiangiogenic capabilities, may contribute to superior healing in wounds on the trunks of horses by protecting such wounds from excessive formation of vascular granulation tissue that characterizes wounds on the limbs of this species.
Objective—To determine the effect of a silicone dressing
on the rate and quality of repair of limb wounds and
compare microvascular occlusion and apoptosis in
wounds treated with the silicone dressing and those
treated with a conventional dressing in horses.
Procedure—Horses received two 6.25-cm2 wounds
on each metacarpus. Ten wounds were treated with a
silicone dressing; the other 10 were treated with a
control dressing. Quality of repair and wound size
were evaluated at each bandage change. Time to healing
and the number of excisions of exuberant granulation
tissue were recorded. Biopsy specimens taken
from healed wounds were evaluated semiquantitatively
via histologic examination, p53 immunohistochemical
analysis, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)
to quantify apoptosis, and electron microscopic examination
to measure microvessel luminal diameters.
Results—The silicone dressing surpassed the conventional
dressing in preventing formation of exuberant
granulation tissue and improving tissue quality.
Microvessels were occluded significantly more often
in wounds dressed with the silicone gel, which also
diminished the expression of mutant p53, an indirect
inhibitor of apoptosis, although greater apoptosis was
not confirmed quantitatively by use of TUNEL.
Conclusions and Clinical Relevance—Because the
silicone dressing inhibited the formation of exuberant
granulation tissue, it may be integrated in a management
strategy designed to improve the repair of limb
wounds in horses. (Am J Vet Res 2005;66:1133–1139)
Objective—To evaluate the effect of platelet-rich plasma on wounds on the distal aspect of the forelimb in horses.
Animals—6 mixed-breed 10- to 15-year-old mares.
Procedures—3 wounds were created on metacarpal regions in each of 6 horses (n = 36 wounds total). Eighteen wounds were treated with platelet-rich plasma and bandaged, whereas 18 control wounds were similarly bandaged with no prior topical treatment. Decrease in wound surface area and the required number of excisions of exuberant granulation tissue were recorded until complete healing. Tissue specimens were taken from wounds at 1 week for histologic examination and measurement of transforming growth factor-β1 concentrations and at closure for histologic examination, biomechanical evaluation, and measurement of collagen type I and type III mRNA.
Results—Platelet-rich plasma favored excessive development of granulation tissue and significantly slowed wound healing at 1, 2, and 3 weeks after surgery. Transforming growth factor-β1 had a 1.6-fold higher concentration in treated wounds, compared with untreated wounds. Histologic, biomechanical, and gene expression data did not differ significantly between treated and control wounds.
Conclusions and Clinical Relevance—Topical application of autologous platelet-rich plasma did not accelerate or improve the quality of repair of small granulating wounds on limbs of horses. This treatment may better suit wounds with massive tissue loss or, alternatively, chronic wounds that would benefit from a fresh source of mediators to accelerate the healing process.
Objective—To evaluate the ability of signal attenuation–based quantitative magnetic resonance imaging (QMRI) to estimate subchondral bone mineral density (BMD) as assessed via quantitative computed tomography (QCT) in osteoarthritic joints of horses.
Sample Population—20 metacarpophalangeal joints from 10 horse cadavers.
Procedures—Magnetic resonance (MR) images (dorsal and transverse T1-weighted gradient recalled echo [GRE] and dorsal T2*-weighted GRE fast imaging employing steady-state acquisition [T2*-FIESTA]) and transverse single-slice computed tomographic (CT) images of the joints were acquired. Magnetic resonance signal intensity (SI) and CT attenuation were quantified in 6 regions of interest (ROIs) in the subchondral bone of third metacarpal condyles. Separate ROIs were established in the air close to the joint and used to generate corrected ratios and SIs. Computed tomographic attenuation was corrected by use of a calibration phantom to obtain a K2HPO4-equivalent density of bone. Correlations between QMRI performed with different MR imaging sequences and QCT measurements were evaluated. The intraobserver repeatability of ROI measurements was tested for each modality.
Results—Measurement repeatability was excellent for QCT (R2 = 98.3%) and QMRI (R2 = 98.8%). Transverse (R2 = 77%) or dorsal (R2 = 77%) T1-weighted GRE and QCT BMD measurements were negatively correlated, as were dorsal T2*-FIESTA and QCT (R2 = 80%) measurements. Decreased bone SI during MR imaging linearly reflected increased BMD.
Conclusions and Clinical Relevance—Results of this ex vivo study suggested that signal attenuation–based QMRI was a reliable, clinically applicable method for indirect estimation of subchondral BMD in osteoarthritic metacarpophalangeal joints of horses.
To assess the feasibility of a canister-free negative-pressure wound therapy (NPWT) device (PICO™ 1.6, Smith & Nephew Medical Ltd) and evaluate its effect on early phases of wound healing in canine experimental cutaneous wounds.
5 adult spayed female research Beagles.
In a pilot experimental study, 1 full-thickness 2-cm X 2-cm cutaneous wound was surgically created on each hemithorax in each dog. Wounds were treated with either NPWT or a conventional wound dressing for 14 days. Bandage changes and wound evaluations were done at 7 time points. First macroscopic appearance of granulation tissue, smoothness of granulation tissue, and percentages of wound contraction and epithelialization were compared between treatments. Wounds were sampled at 3 time points for histopathologic analyses and semiquantitative scoring.
NPWT dressings were well tolerated by all dogs. Complete seal of the dressing required the application of adhesive spray, and maintenance of the vacuum lessened over time. Self-limiting skin irritations appeared in all dogs and hampered the attainment of negative pressure. Granulation tissue developed faster and was more abundant in control wounds. Wound contraction, epithelialization, and fibroblast proliferation were greater in control wounds at the end of the study.
This canister-free NPWT device is feasible but problematic in maintaining a vacuum, requiring frequent revisions of the dressing. Further studies are necessary to evaluate the effect of this device on early phases of wound healing. Its benefits in wound healing remain unknown.