Annuloaortic ectasia in a four-month-old male Newfoundland dog: long-term follow-up and immunofluorescent study.

A 4 month-old, 14.8 kg, male Newfoundland dog was presented for cardiovascular evaluation following detection of a heart murmur. Echocardiography revealed enlargement of the sinuses of Valsalva and marked, diffuse dilation of the ascending aorta (annuloaortic ectasia, AAE), with mild/equivocal subaortic stenosis (SAS). The dog was monitored over the duration of its lifetime, with serial echocardiograms performed at 5, 6, and 8 months and 1, 2, 3, 4, 8, and 10 years demonstrating persistent, diffuse dilation of the ascending aorta. The dog lived until it was 10 years old and died of metastatic carcinoma. Postmortem examination confirmed AAE and mild SAS. Hematoxylin and eosin and Weigert van Gieson stains were used to compare the ascending aorta to the descending aorta and left subclavian artery, and to compare aortic samples to those of three control dogs. Histopathologic evaluation revealed mild medial degeneration in the ascending aorta of all four dogs. Immunofluorescent microscopy was used for determining the deposition of proteins known to play a role in aortic aneurysms in humans: fibrillin-1 (FBN1), latent transforming growth factor beta binding protein 4 (LTBP4) and fibronectin. The ascending aorta of the AAE case demonstrated reduced deposition of FBN1, indicating that its loss may have contributed to aortic dilation. Diffuse, primary ascending aortic dilation is uncommonly reported in dogs; when it is, it carries a poor prognosis. This case provides an important example of marked dilation of the ascending aorta in a dog that lived with no associated adverse effects for 10 years.

Left subclavian artery dissection associated with connective tissue abnormalities resembling Marfan-like syndrome in an English bulldog.

The unexpected demise of a 12-year-old male neutered English bulldog solicited a gross examination, which revealed a blood-filled space occurring in the proximal left subclavian artery (LSA). It originated about 1 cm from the branching point of the vessel and progressively dilated for 3 cm distal to this origin. Histopathological investigation showed that the tunica media of the LSA was more than 50% split, with the blood-filled space dissecting through the arterial wall. In the tunica media of the LSA, severe multifocal fragmentation and/or loss of the elastic fibers was observed. The retained disorganized elastic fibers were separated and disoriented due to accumulations of acid mucopolysaccharide. Marked, diffuse medial, and adventitial fibrous tissue deposition was also identified. The cause of death was attributed to acute hemorrhagic and necrotizing pancreatitis with pulmonary edema, suggesting that LSA dissection was an incidental finding. Subclavian artery dissection is extremely rare in humans, where the involvement of the LSA in cases of aortic dissection both with or without Marfan syndrome has been reported. Aortic and pulmonary artery dissection in bovines and aortic aneurysm and dissection in dogs have been reported to be associated with Marfan and Marfan-like syndromes, respectively. Histopathological findings suggestive of underlying connective tissue abnormalities resembling Marfan-like syndrome (i.e., the appearance of the elastic tissue and the degenerative changes of the tunica media) were detected in the first case of LSA dissection in dogs and veterinary medicine, herein described.

Aortic tear and dissection related to connective tissues abnormalities resembling Marfan syndrome in a Great Dane.

Aortic tears and acute aortic dissection are rarely reported in dogs. This report describes a case of aortic dissection and probable sinus of Valsalva rupture in a young Great Dane with associated histopathologic findings suggestive of a connective tissue abnormality.

Connective tissue disorders in domestic animals.

Though soft tissue disorders have been recognized and described to some detail in several types of domestic animals and small mammals for some years, not much progress has been made in our understanding of the biochemical basis and pathogenesis of these diseases in animals. Ehlers-Danlos syndrome described in dogs already in 1943 and later in cats affects mainly skin in these animals. The involved skin is thin and hyperextensible with easily inflicted injuries resulting in hemorrhagic wounds and atrophic scars. Joint laxity and dislocation common in people are less frequently found in dogs. No systemic complications, such as organ rupture or cardiovascular problems which have devastating consequences in people have been described in cats and dogs. The diagnosis is based on clinical presentation and on light or electron microscopic features of disorganized and fragmented collagen fibrils. Several cases of bovine and ovine dermatosparaxis analogous to human Ehlers-Danlos syndrome type VIIC were found to be caused by mutations in the procollagen I N-proteinase (pnPI) or ADAMTS2 gene, though mutations in other sites are likely responsible for other types of dermatosparaxis. Cattle suffering from a form of Marfan syndrome were described to have aortic dilatation and aneurysm together with ocular abnormalities and skeletal involvement. As in people mutations at different sites of bovine FBN1 may be responsible for Marfan phenotype. Hereditary equine regional dermal asthenia (HERDA), or hyperelastosis cutis, has been recognized in several horse breeds as affecting primarily skin, and, occasionally, tendons. A mutation in cyclophilin B, a chaperon involved in proper folding of collagens, has been identified in some cases. Degenerative suspensory ligament desmitis (DSLD) affects primarily tendons and ligaments of certain horse breeds. New data from our laboratory showed excessive accumulation of proteoglycans in organs with high content of connective tissues. We have identified an abnormal form of decorin with altered biological activity in these proteoglycan deposits, and more recently changes in processing of aggrecan were found by us and other investigators.The naturally occurring diseases of soft tissues in domestic animals described here have a potential to serve as good models for analogous human diseases. This is the case particularly relevant to dogs as a half out of the more than 400 naturally occurring hereditary canine diseases has the potential to serve as a model for human disease.

Cardiovascular lesions in bovine Marfan syndrome.

Bovine Marfan syndrome is a genetic disease with many of the clinical and pathologic manifestations of human Marfan syndrome. Major manifestations include ectopia lentis and aortic dilatation, aneurysm, and rupture. Affected cattle have a defect in fibrillin metabolism similar to that in human patients. Ten cattle were followed and their disease progression and lesions documented. Ages ranged from a term fetus (No. 9) to a 4-year-old cow (No. 4); three animals were male (Nos. 1-3) and seven were female (Nos. 4-10). Of eight animals (80%) that died or were euthanatized (Nos. 1-3, 5-9), six (75%) had severe cardiovascular lesions identified at necropsy. Gross cardiovascular lesions of bovine Marfan syndrome included cardiac tamponade secondary to aortic rupture (animal Nos. 3, 6, 8), dissecting aneurysms of the aorta and pulmonary artery (animal No. 5), and intrauterine cardiac tamponade secondary to rupture of the pulmonary artery (animal No. 9). Microscopically, Verhoeff Van Gieson-stained sections of aorta contained severe fragmentation of the elastic laminae in the aortic media, but the cystic medial necrosis seen in human Marfan aortae was not identified, even in the chronic aortic dissection. Ultrastructurally, affected aortic tissue was characterized by thin, dark elastic fibers with abundant, tangled microfibrils on the periphery. Swirls of collagen fibers and bundles of hypertrophic smooth muscle cells replaced damaged elastic laminae. Gross and microscopic cardiovascular lesions in bovine Marfan syndrome are similar to those in human Marfan syndrome. Bovine Marfan syndrome is a valuable model for investigation of molecular pathogenesis and treatment of human Marfan syndrome.

Identification of defects in the fibrillin gene and protein in individuals with the Marfan syndrome and related disorders.

The Marfan syndrome is an autosomal dominant disorder with pleiotropic manifestations that involve the cardiovascular, ocular, and skeletal systems. Through a number of investigational approaches, the gene encoding for fibrillin, the FBN1 gene on chromosome 15, has been identified as the defective gene causing the Marfan syndrome. Fibrillin is the large glycoprotein with a repetitive domain structure and is a major protein component of microfibrils, a fibrillar system closely associated with elastin in connective tissue. Mutational analysis of defects in the FBN1 gene in patients with the Marfan syndrome has revealed that most mutations are private or unique in an affected individual or family. Analysis of fibrillin protein or gene defects in individuals with related phenotypes has revealed that a perinatal lethal syndrome, termed neonatal Marfan syndrome, is due to FBN1 gene mutations. In addition, fibroblast cell strains from a subset of patients with idiopathic scoliosis have fibrillin protein defects. Last, fibroblasts from calves affected with bovine Marfan syndrome display defects in the fibrillin protein. These studies have wide-ranging implications in the diagnosis, treatment, and prevention of Marfan syndrome and related disorders.

Abnormal fibrillin metabolism in bovine Marfan syndrome.

Bovine Marfan syndrome is a disorder that closely resembles human Marfan syndrome in its clinical signs and pathological lesions. The similarities between the human and bovine diseases suggest that similar metabolic defects could be responsible. Although indirect immunofluorescent assays for fibrillin in skin biopsies did not distinguish affected cattle from control animals, cultures of skin fibroblasts of affected animals were distinguished from normal, unrelated control animals and normal half-siblings on the basis of fibrillin staining. After 72 to 96 hours in culture, stained with anti-fibrillin monoclonal antibody 201, hyperconfluent fibroblast cultures of affected cattle had less immunoreactive fibrillin than control cultures, and the staining pattern was granular rather than fibrillar. Under similar culture conditions, normal bovine aortic smooth muscle cells produced large amounts of immunoreactive fibrillin, but smooth muscle cells from a single affected cow showed markedly less fibrillin staining. In pulse-chase metabolic labeling experiments with [35S]cysteine, dermal fibroblasts from 6 affected calves, incorporated far less fibrillin into the extracellular matrix than control cells. These findings are similar to those reported in human Marfan syndrome, and they suggest that the bovine Marfan syndrome, like the human disorder, is caused by a mutation in fibrillin, leading to defective microfibrillar synthesis.

Normal elastin content of aorta in bovine Marfan syndrome.

Samples from the ascending aortae from two calves affected by bovine Marfan syndrome were subjected to biochemical analyses of the connective tissue and were compared to age-matched controls. Elastin was extracted from the aortic samples with 5 M guanidine-HCl, bacterial collagenase digestion, and dithiothreitol reduction. Amino acid analysis revealed that desmosine and isodesmosine levels were the same in Marfan calves as in control animals. Gravimetric measurements of elastin, amino acid composition, soluble protein, and uronic acid values also showed no significant difference between Marfan and control tissue. In contrast to elastin, collagen in aortae of Marfan calves was significantly higher than the mean of several controls. These findings, along with other observations of this animal model, support the conclusion that the microscopic and biochemical lesions of aortic elastin in bovine Marfan syndrome likely result from defective microfibrillar metabolism. Absence of cystic medial necrosis in bovine Marfan aortae may explain normal elastin content in the animal model.

An animal model of the Marfan syndrome.

A congenital syndrome of long, thin limbs, severe joint and tendon laxity, microspherophakia, ectopia lentis, heart murmurs and aortic dilatation was identified in 7 calves. All affected calves were sired by a single phenotypically normal bull suspected of germline mosaicism for a new mutation resulting in this disease. One of the calves subsequently died with ruptured aorta at age 16 months. Histopathologic and electron microscopic studies of the aortic media of affected calves demonstrated disorganized elastin and narrowed elastic lamina separated by widened spaces. This bovine disease provides a unique animal model of the human Marfan syndrome. A herd of cattle with this disease is being developed for further studies.