Reduced transforming growth factor-beta signaling in cartilage of old mice: role in impaired repair capacity

Osteoarthritis (OA) is a common joint disease, mainly effecting the elderly population. The cause of OA seems to be an imbalance in catabolic and anabolic factors that develops with age. IL-1 is a catabolic factor known to induce cartilage damage, and transforming growth factor (TGF)-beta is an anabolic factor that can counteract many IL-1-induced effects. In old mice, we observed reduced responsiveness to TGF-beta-induced IL-1 counteraction. We investigated whether expression of TGF-beta and its signaling molecules altered with age. To mimic the TGF-beta deprived conditions in aged mice, we assessed the functional consequence of TGF-beta blocking. We isolated knee joints of mice aged 5 months or 2 years, half of which were exposed to IL-1 by intra-articular injection 24 h prior to knee joint isolation. Immunohistochemistry was performed, staining for TGF-beta1, -2 or -3, TGF-betaRI or -RII, Smad2, -3, -4, -6 and -7 and Smad-2P. The percentage of cells staining positive was determined in tibial cartilage. To mimic the lack of TGF-beta signaling in old mice, young mice were injected with IL-1 and after 2 days Ad-LAP (TGF-beta inhibitor) or a control virus were injected. Proteoglycan (PG) synthesis (³⁵S-sulfate incorporation) and PG content of the cartilage were determined. Our experiments revealed that TGF-beta2 and -3 expression decreased with age, as did the TGF-beta receptors. Although the number of cells positive for the Smad proteins was not altered, the number of cells expressing Smad2P strongly dropped in old mice. IL-1 did not alter the expression patterns. We mimicked the lack of TGF-beta signaling in old mice by TGF-beta inhibition with LAP. This resulted in a reduced level of PG synthesis and aggravation of PG depletion. The limited response of old mice to TGF-beta induced-IL-1 counteraction is not due to a diminished level of intracellular signaling molecules or an upregulation of intracellular inhibitors, but is likely due to an intrinsic absence of sufficient TGF-beta receptor expression. Blocking TGF-beta distorted the natural repair response after IL-1 injection. In conclusion, TGF-beta appears to play an important role in repair of cartilage and a lack of TGF-beta responsiveness in old mice might be at the root of OA development.

Evaluation of carbon dioxide laser and conventional incisional techniques for resection of soft palates in brachycephalic dogs

OBJECTIVE

To compare clinical outcome, healing, and effect of tracheostomy in conventional incisional and carbon dioxide (CO2) laser techniques for resection of soft palates in brachycephalic dogs.

DESIGN

Prospective randomized trial.

ANIMALS

20 adult brachycephalic dogs.

METHODS

Dogs were randomly allocated into 4 groups, and 1 of the following was performed: palate resection by use of a CO2 laser; incisional palate resection and closure with suture; and palate resection by use of a C02 laser or incision with tracheostomy. A clinical score for respiratory function was assigned to each dog at 0, 2, 8, 16, and 24 hours. Biopsy specimens of incision sites obtained at days 0, 3, 7, and 14 were examined. Data were analyzed to determine the effects of technique on clinical and histologic outcome.

RESULTS

Mean surgical time for laser (309 seconds) was significantly shorter than for sharp dissection (744 seconds). Surgical technique significantly affected clinical scores at 3 of the 5 postoperative time points, but differences were not clinically apparent. Tracheostomy significantly affected clinical scores at 3 of 5 postoperative time points. After tracheostomy tube removal, clinical scores were similar to those of dogs without tracheostomies. Inflammation, necrosis, and ulceration were evident in all groups at day 3; these lesions had almost resolved by day 14. Most complications were associated with tracheostomy.

CONCLUSIONS AND CLINICAL RELEVANCE

Clinical outcomes appear to be similar with the laser and incisional techniques. Regarding surgical time and ease, laser resection of the soft palate appears advantageous. Tracheostomy is not warranted in dogs that have uncomplicated surgeries and recoveries.

Histopathological, radiographic, and arthrographic comparison of the biceps tendon in normal dogs and dogs with biceps tenosynovitis

In dogs surgically treated for biceps tenosynovitis, the most common histopathological findings were fibrosis and collagen degeneration (n=13), synovial villous or vascular hyperplasia (n=10), lymphocytic-plasmacytic infiltrates (n=10), cartilaginous metaplasia (n=8), and ischemic necrosis (n=5). Degree of histopathological changes was associated with degree (p equals 0.000), but not duration (p equals 0.543), of lameness. Furthermore, there was no association between histopathological changes and age or radiographic and arthrographic findings. Cartilage metaplasia was the only histopathological finding in both affected tendons (8/18) and normal control dogs (13/13). Age and size of the control dogs were not determined; however, since all these dogs were clinically normal, fibrocartilaginous metaplasia can be present as an incidental finding in the biceps tendon of origin in dogs.

Calcinosis circumscripta of the thoracic wall in a German shepherd dog

Calcinosis circumscripta of the left thoracic wall was diagnosed in a six-month-old, female German shepherd dog by thoracic radiography and ultrasonographic-guided biopsy. The puppy developed the lesion following a left thoracotomy to repair a patent ductus arteriosus. Complete resolution occurred following surgical excision of the lesion. Calcinosis circumscripta associated with routine surgical manipulation and postoperative inflammation has been reported rarely but should be suspected when a focal, mineralized lesion occurs at a previous surgical site, especially in German shepherd dogs.

Removal of a cholesteatoma in a dog, using a caudal auricular approach

A new surgical method for treating cholesteatoma in dogs is described. Although rarely reported in dogs, cholesteatomas may be more common than previously believed. Complete excision of a cholesteatoma is associated with low recurrence and good long-term prognosis. Surgical intervention, with total ear canal ablation and lateral bulla osteotomy, has been recommended in dogs with tumors of the middle ear; however, this technique often results in conductive hearing loss. Through a caudal auricular approach to the tympanic bulla, we were able to preserve the external ear canal, reconstruct the auditory ossicles, and graft the tympanic membrane. Results of brain stem auditory-evoked response tests in the dog revealed intact conduction potentials. A caudal auricular approach to the tympanic bulla is technically possible, preserves normal appearance, and may maintain, or even improve, hearing conduction of affected ears in dogs.

Surgical excision of soft tissue fibrosarcomas in cats

OBJECTIVE

The purpose of this study was to determine the tumor-free interval and survival times of cats who had one (group 1) or more (group 2) surgeries, or surgery and radiation therapy (RTH) (group 3) for treatment of soft tissue fibrosarcomas (FSA).

STUDY DESIGN

Retrospective study.

ANIMALS OR SAMPLE POPULATION

45 client-owned cats.

METHODS

Medical records of cats with soft tissue FSA were examined. Vaccination and feline leukemia virus (FeLV) status, age, sex, breed, tumor location, number of surgeries, completeness of excision, and histopathological grade were evaluated to correlate with tumor-free interval and survival periods.

RESULTS

Overall median tumor-free interval and survival times were 10 and 11.5 (range, 1 to 40) months. Median tumor-free interval and survival times were more than 16 months each in group 1, more than 5 and 13 months in group 2, and 4.5 and 9 months in group 3. Age, sex, breed, vaccination or FeLV status, tumor location, or histopathological grade did not affect median tumor-free interval or survival times (P > .05). Cats with complete excisions had significantly longer median tumor-free interval (> 16 versus 4 months) and survival time (> 16 versus 9 months) than those with incomplete excisions (P = .008). Radiation therapy did not seem to extend tumor-free interval and survival times (P = .013). However, most group 3 cats had incomplete surgical excisions, resulting in recurrent or progressive disease.

CONCLUSIONS

Complete surgical excision of FSA in cats is possible and can be curative.

CLINICAL RELEVANCE

Aggressive surgical excision with wide margins appears to contribute to extended tumor-free interval and survival times in cats with soft tissue FSA. Controlled prospective studies are needed to determine the efficacy of RTH in treatment.