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- Author or Editor: Yan Lu x
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Abstract
Objective—To compare 2 methods of quantitating chondrocyte viability and to determine chondrocyte response to thermal injury over time.
Sample Population—108 stifle joints from 54 adult rats.
Procedures—Cartilage from the distal aspect of the femur was treated ex vivo with radiofrequency energy at a probe setting that would result in immediate partial-thickness chondrocyte death; untreated sections served as controls. Explants were cultured, and cell viability was compared by use of lactate dehydrogenase (LDH) histochemical staining and calcein AM and ethidium homodimer-1 confocal laser microscopy (CLM) cell viability staining. Terminal deoxynucleotidyl transferase–mediated X-dUTP nick end labeling (TUNEL) was used to detect apoptosis. All labeling studies were performed 0, 1, 3, 7, 14, and 21 days after treatment.
Results—In the treated tissues, a greater percentage of viable cells were found with CLM, compared with LDH staining. This result contrasted that of control tissues in which LDH staining indicated a greater percentage of live cells than CLM. The greatest number of TUNEL-positive chondrocytes was present at day 3, declining at later time intervals.
Conclusions and Clinical Relevance—CLM and LDH histochemistry techniques yield different absolute numbers of live and dead cells, resulting in differing percentages of live or dead cells with each technique. These differences may be related to the enzymes responsible for activation in each technique and the susceptibility of these enzymes to thermal injury. Results of TUNEL indicate that apoptosis contributes to chondrocyte death after thermal injury, with a peak signal identified 3 days after insult.
Abstract
Objective—To determine the effects of 2 doses of recombinant human bone morphogenetic protein-2 in an absorbable collagen sponge (rhBMP-2/ACS) on bone healing in dogs.
Animals—27 adult dogs.
Procedures—Dogs underwent a mid-diaphyseal (1-mm) tibial osteotomy (stabilized with external skeletal fixation) and received an ACS containing 0.28 mg (0.2 mg/mL) or 0.56 mg (0.4 mg/mL) of rhBMP-2 or no treatment (control dogs). All dogs were examined daily; bone healing was assessed via radiography and subjective lameness evaluation every 2 weeks. After euthanasia at 8 weeks, tibiae were evaluated biomechanically and histologically.
Results—Control dogs required antimicrobial treatment for pin-site–related complications more frequently than did rhBMP-2/ACS–treated dogs. At 4 and 6 weeks, weight bearing was greater in dogs treated with rhBMP-2/ACS (0.2 mg/mL) than in control dogs, albeit not significantly. Compared with control treatment, both doses of rhBMP-2/ACS accelerated osteotomy healing at 4, 6, and 8 weeks, and the 0.2 mg/mL dose enhanced healing at 2 weeks; healing at 6 weeks was greater for the lower-dose treatment than for the higher-dose treatment. Histologically, healing at 8 weeks was significantly improved for both rhBMP-2/ACS treatments, compared with control treatment. Among groups, biomechanical variables did not differ, although less osteotomy-site failures occurred in rhBMP-2/ACS–treated groups.
Conclusions and Clinical Relevance—In dogs that underwent tibial osteotomy, rhBMP-2/ACS (0.2 mg/mL) appeared to accelerate bone healing and reduce lameness (compared with control treatment) and apparently augmented bone healing more than rhBMP-2/ACS (0.4 mg/mL). Compared with control dogs, rhBMP-2/ACS–treated dogs required antimicrobial treatments less frequently.
Abstract
Objective—To compare effects of synovectomy performed by use of monopolar radiofrequency energy (MRFE) versus mechanical debridement in rabbits with induced inflammatory arthritis.
Animals—25 mature female New Zealand White rabbits.
Procedure—Inflammatory arthritis was induced in both femoropatellar joints of each rabbit. Joints then were treated by mechanical debridement or MRFE treatment or served as sham-operated controls. Rabbits were euthanatized 2 weeks or 3 months after surgery. Biopsy specimens of synovium were analyzed by use of light microscopy.
Results—At 2 weeks after surgery, samples from MRFE-treated joints had fewer plasma cells and more heterophils than the other 2 groups and more lymphocytes than sham-operated controls, whereas samples from mechanically debrided joints had greater numbers of lymphocytes and heterophils than sham-operated controls. At 3 months after surgery, samples from MRFE-treated joints had fewer plasma cells than sham-operated controls, more heterophils than mechanically debrided and sham-operated controls, and more macrophages than mechanically debrided joints. There was no difference in synovial ablation, synovial proliferation, or fibrosis among the 3 groups at 2 weeks or 3 months after surgery.
Conclusions and Clinical Relevance—Analysis of results of this study documented a similar degree of synovial ablation when comparing use of MRFE to mechanical debridement. In rabbits with this method of induced inflammatory arthritis, there were no detectable benefits of MRFE or mechanical debridement on the synovium, compared with results for sham-operated control joints, at 2 weeks and 3 months after surgery for most of the synovial variables evaluated. ( Am J Vet Res 2004;65:573–577)
Abstract
Objective—To determine the critical temperature that reduces chondrocyte viability and evaluate the ability of chondrocytes to recover after exposure to the critical temperature.
Sample Population—Cartilage explants obtained from the humeral heads of 30 sheep.
Procedures—In a randomized block design, 318 full-thickness cartilage explants were collected from 30 humeral heads of sheep and cultured for up to 14 days. On the first day of culture (day 0), explants were subjected to temperatures of 37°, 45°, 50°, 55°, 60°, or 65°C for 5 minutes by heating culture tubes in a warming block. The ability for chondrocytes to recover after exposure to the critical temperature was determined by evaluating viability at days 0, 1, 3, 7, and 14 days after heating. Images were analyzed by use of confocal laser microscopy.
Results—Analysis of images revealed a significant decrease in live cells and a significant increase in dead cells as temperature increased. Additionally, the deepest layer of cartilage had a significantly lower percentage of live cells, compared with values for the 3 most superficial layers. Chondrocytes did have some ability to recover temporarily after the initial thermal insult.
Conclusions and Clinical Relevance—A strong relationship exists between increasing temperature and cell death, with a sharp increase in chondrocyte death between 50° and 55°C. Chondrocytes in the deepest cartilage layer are most susceptible to thermal injury. The threshold of chondrocyte recovery from thermal injury is much lower than temperatures reached during chondroplasty by use of most radiofrequency energy devices.
Abstract
Objective—To identify cardiac mechanisms that contribute to adaptation to high altitudes in Tibetan antelope (Pantholops hodgsonii).
Animals—9 male Tibetan antelope and 10 male Tibetan sheep (Ovis aries).
Procedures—Tibetan antelope and Tibetan sheep inhabiting a region with an altitude of 4,300 m were captured, and several cardiac variables were measured. Expression of genes for atrial natriuretic peptide, brain natriuretic peptide, and calcium-calmodulin–dependent protein kinase II δ was measured via real-time PCR assay.
Results—Ratios of heart weight to body weight for Tibetan antelope were significantly greater than those of Tibetan sheep, but ratios of right-left ventricular weights were similar. Mean ± SD baseline heart rate (26.33 ± 6.15 beats/min) and systolic arterial blood pressure (97.75 ± 9.56 mm Hg) of antelope were significantly lower than those of sheep (34.20 ± 6.57 beats/min and 130.06 ± 17.79 mm Hg, respectively). The maximum rate of rise in ventricular pressure in antelope was similar to that in Tibetan sheep, but after exposure to air providing a fraction of inspired oxygen of 14.6% or 12.5% (ie, hypoxic conditions), the maximum rate of rise in ventricular pressure of the antelope increased significantly to 145.1% or 148.1%, respectively, whereas that of the sheep decreased to 68.4% or 70.5%, respectively. Gene expression of calcium-calmodulin–dependent protein kinase II δ and atrial natriuretic peptide, but not brain natriuretic peptide, in the left ventricle of the heart was significantly higher in antelope than in sheep.
Conclusions and Clinical Relevance—Hearts of the Tibetan antelope in this study were well adapted to high-altitude hypoxia as shown by higher heart weight ratios, cardiac contractility in hypoxic conditions, and expression of key genes regulating cardiac contractility and cardiac hypertrophy, compared with values for Tibetan sheep.
