Early immunohistochemical detection of pulmonary micrometastases in dogs with osteosarcoma.

BACKGROUND: Despite decades of research, the early phases of metastatic development are still not fully understood. Canine osteosarcoma (OS) is a highly aggressive cancer, with a high metastatic rate (> 90%), despite a low overt metastatic prevalence at initial diagnosis (< 15%). Canine OS is generally regarded as a good clinically relevant model for human OS. The aim of this hypothesis-generating study was to evaluate a method to detect pulmonary micrometastases and study their prevalence in dogs with OS without macroscopic metastases. We prospectively enrolled dogs with OS that received no cancer-specific treatment (n = 12) and control dogs without cancer (n = 2). Dogs were necropsied and sampled immediately after euthanasia. The OS dogs were classified as having macroscopic metastases (n = 2) or not (n = 10). We immunohistochemically stained one tissue sample from each of the seven lung lobes from each dog with a monoclonal antibody (TP-3) to identify micrometastases (defined as clusters of 5-50 tumour cells), microscopic metastases (> 50 tumour cells) and TP-3 positive single cells (< 5 tumour cells). RESULTS: We showed that pulmonary micrometastases easily overseen on routine histology could be detected with TP-3. Pulmonary micrometastases and microscopic metastases were present in two dogs with OS without macroscopic metastases (20%). Micrometastases were visualised in three (43%) and four (57%) of seven samples from these two dogs, with a mean of 0.6 and 1.7 micrometastases per sample. Microscopic metastases were present in one (14%) and four (57%) of seven samples from the same two dogs, with a mean of 0.14 and 1.0 microscopic metastases per sample. There were four (57%) and two (29%) samples with neither microscopic metastases nor micrometastases for each of these two dogs. The prevalence of pulmonary micrometastases (20%) was significantly lower than expected (> 90%) based on commonly expected metastatic rates after amputation (P < 0.0001). There was no statistically significant difference in the number of TP-3 positive single cells in between groups (P = 0.85). CONCLUSIONS: Pulmonary micrometastases could be detected with TP-3 immunohistochemistry in a subset of dogs with OS before macroscopic metastases had developed. We propose that dogs with spontaneous OS represent clinically relevant models to study early micrometastatic disease.

Association between clinical signs and histopathologic changes in the synovium of the tarsocrural joint of horses with osteochondritis dissecans of the tibia.

OBJECTIVE: To develop a scoring system for histopathologic changes in the synovium of tarsocrural joints (TCJs) of horses with osteochondritis dissecans (OCD) and to test for association between histopathologic changes and joint effusion or lameness. ANIMALS: 93 horses with OCD of the intermediate ridge of the tibia of 1 or both TCJs (134 joints) and 38 control horses without disease of TCJs (38 joints). PROCEDURES: For OCD-affected horses, pretreatment lameness, TCJ effusion, and results of pelvic limb flexion test were scored. Synovial biopsy specimens were obtained from TCJs of OCD-affected horses during arthroscopy, and similar postmortem tissue specimens were obtained from control horses through a small arthrotomy. Histologic signs of synovitis in 172 biopsy specimens were scored by 2 pathologists (A and B) by use of 2 criteria: synoviocyte proliferation and cellular infiltration. RESULTS: Analysis of scoring revealed good to very good intraobserver agreement within pathologist A (weighted kappa [WK], 0.76 to 0.81), and moderate to good agreement within pathologist B (WK, 0.56 to 0.63). Interobserver agreement for synoviocyte proliferation (WK, 0.34 to 0.52) and cellular infiltration (WK, 0.38 to 0.48) scores was fair to moderate. Joint effusion and synoviocyte proliferation were significantly associated, as were joint effusion and cellular infiltration. There was no association between histopathologic changes and the other clinical signs evaluated. CONCLUSIONS AND CLINICAL RELEVANCE: The scoring system was helpful for evaluating synovial inflammation caused by OCD of the intermediate ridge of the tibia in horses. Histopathologic signs of synovial inflammation were associated with effusion but not with lameness.

Impact of natural sheep-goat transmission on detection and control of small ruminant lentivirus group C infections.

Dissemination of small ruminant lentivirus (SRLV) infections in Norway is affected by the different control strategies used for maedi-visna virus (MVV) infections in sheep and caprine arthritis-encephalitis virus (CAEV) infections in goats. Here we investigated SRLV phylogenetic group variants in sheep. CAEV-like isolates, belonging to phylogenetic group C, were found among both seropositive sheep and goats in mixed flocks, in which sheep and goats are kept together. Intra-herd clustering confirmed that mixed flock animals were infected by the same virus variant, suggesting ongoing interspecies transmission. Few sheep flocks were found to be infected with the MVV-like phylogenetic group A. The apparent absence of SRLV group A type in goats is probably due to the MVV control programme and animal management practices. SRLV group C targets lungs and mammary glands in sheep, and induces typical SRLV pathological lesions. SRLV group C isolated from the sheep mammary glands suggested a productive infection and potential for transmission to offspring. SRLV group C was most prevalent among goats. A lower PCR sensitivity in seropositive sheep suggested a lower load of SRLV group C provirus in sheep than in goats. Higher genetic divergence of group C than in other SRLV groups and extensive heterogeneity among group C isolates in the matrix C-terminal region demonstrate the need for identifying conserved target regions when developing PCR protocols for SRLV detection. As sheep and goats may serve as reservoirs for all SRLV genogroup types, successful control programmes require inclusion of both species.

Chronic kidney disease with three cases of oxalate-like nephrosis in Ragdoll cats.

Two unrelated Ragdoll cat mothers in Norway were found dead from renal disease. The histopathology was consistent with oxalate nephrosis with chronic or acute-on-chronic underlying kidney disease. Both cats had offspring and relatives with signs of urinary tract disease, including a kitten dead with urethral gravel. Eleven living Ragdoll cats, including nine relatives of the dead cats and the male father of a litter with similarly affected animals, were tested for primary hyperoxaluria (PH) type 1 and 2 by urine oxalate and liver enzyme analysis. Renal ultrasound revealed abnormalities in five living cats. One of these was azotaemic at the time of examination and developed terminal kidney disease 9 months later. A diagnosis of PH was excluded in 11 cats tested. The inheritance and aetiological background of the renal disease present in the breed remains unresolved at this point in time.

Clinical, radiographic, and pathologic abnormalities in dogs with multiple epiphyseal dysplasia: 19 cases (1991-2005).

OBJECTIVE: To determine clinical, radiographic, and pathologic abnormalities in dogs with multiple epiphyseal dysplasia (MED). DESIGN: Retrospective case series. ANIMALS: 19 dogs with MED from 10 litters. PROCEDURES: The diagnosis was made on the basis of radiographs of the shoulder region and vertebral column. Ten dogs underwent necropsy. RESULTS: There were 11 Hygenhund, 6 Dunker, 1 Golden Retriever, and 1 English Pointer. Most dogs were examined because of lameness that developed at 5 to 8 months of age. The most common radiographic abnormality was a deficiency in ossification of the epiphyses, apophyses, and cuboidal bones of the appendicular skeleton and the epiphyses of the vertebrae; ossification of the metaphyses and the diaphyses typically were normal. Disease severity was consistent among littermates, but varied among dogs from different litters. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that MED is a rare condition in dogs characterized by a deficiency in ossification of the epiphyses of the long bones, the epiphyses of the vertebrae, the cuboidal bones, and the apophyses. Radiographic abnormalities were evident in dogs examined as young as 8 weeks of age, and most dogs had developed severe lameness by 5 to 8 months of age. The condition most likely had an autosomal recessive mode of inheritance, although genetic studies of mode of inheritance could not be performed.

Focal changes in blood supply during normal epiphyseal growth are central in the pathogenesis of osteochondrosis in pigs.

Cartilage canals are temporary vessel-containing structures within the growth cartilage. The canals gradually regress with age in a process designated chondrification, where the content of the canals is replaced by cartilage. The process of chondrification is considered physiological; however, premature regression has been associated with the formation of lesions of osteochondrosis. The purpose of the present study was to gain further insight into the nature of and relationship between chondrification of cartilage canals and the initial steps in the pathogenesis of osteochondrosis with respect to morphology, presence of factors influencing the processes, and mode of cellular death. The articular-epiphyseal cartilage complexes of the distal femur of 48 pigs were studied, combining a technique of perfusion and tissue clearing with histological and immunohistological methods. The results provided strong evidence that the process of chondrification occurs at the terminations of the cartilage canals and is characterized by disintegration of the endothelial cells and transformation of perivascular cells into matrix-producing chondrocytes. Lesions of osteochondrosis, however, are characterized by necrosis of the portion of the affected cartilage canal distal to a point of interruption, with subsequent necrosis of adjacent resting zone growth cartilage. This interruption of the cartilage canal blood supply occurs at the junction between cartilage and bone where anastomoses are formed between cartilage canal vessels and vessels from the bone marrow. It is possible that microfractures occurring secondary to minor trauma at a vulnerable time in the development of the cartilage may be the initial event in pathogenesis of osteochondrosis.

Experimental ischemia of porcine growth cartilage produces lesions of osteochondrosis.

Osteochondrosis is a disorder of growth cartilage in which a focal failure of blood supply has been proposed as an important initiating factor. In the present study we investigated the effect on epiphyseal growth cartilage of experimentally interrupting the blood supply to a limited area of the distal femur of growing pigs. In 12 pigs, a thin full-thickness cartilage slab was removed from the abaxial margin of the medial condyle, thereby transecting a limited number of cartilage canals. The pigs were culled 1, 2, 3, 7, 14, 21 and 29 days post-surgery. The condylar cartilage was studied histologically, immunohistologically and by use of the TUNEL method. The transection induced cellular death of cartilage canal elements followed by cellular death of chondrocytes within the deep layers of the resting zone of the epiphyseal growth cartilage. However, in the superficial layers of the resting zone, chondrocytes appeared to proliferate into and subsequently chondrify some of the necrotic cartilage canals. The dying and dead cells were TUNEL-positive, but active caspase 3-negative. The loss of vascular supply induced increased VEGF-immunostaining in chondrocytes surrounding the affected area. We conclude that transection of cartilage canals produces chondronecrosis in the deep resting zone of the epiphyseal growth cartilage similar to that observed in spontaneously occurring osteochondrosis.

Renal histomorphology in dogs with pyometra and control dogs, and long term clinical outcome with respect to signs of kidney disease.

BACKGROUND: Age-related changes in renal histomorphology are described, while the presence of glomerulonephritis in dogs with pyometra is controversial in current literature. METHODS: Dogs with pyometra were examined retrospectively for evidence of secondary renal damage and persisting renal disease through two retrospective studies. In Study 1, light microscopic lesions of renal tissue were graded and compared in nineteen dogs with pyometra and thirteen age-matched control bitches. In Study 2, forty-one owners of dogs with pyometra were interviewed approximately 8 years after surgery for evidence of clinical signs of renal failure in order to document causes of death/euthanasia. RESULTS: Interstitial inflammation and tubular atrophy were more pronounced in dogs with pyometra than in the control animals. Glomerular lesions classified as glomerular sclerosis were present in both groups. No unequivocal light microscopic features of glomerulonephritis were observed in bitches in any of the groups. Two bitches severely proteinuric at the time of surgery had developed end stage renal disease within 3 years. In five of the bitches polyuria persisted after surgery. Most bitches did not show signs of kidney disease at the time of death/euthanasia. CONCLUSION: Tubulointerstitial inflammation was observed, but glomerular damage beyond age-related changes could not be demonstrated by light microscopy in the dogs with pyometra. However, severe proteinuria after surgery may predispose to development of renal failure.