Chondrodystrophic Dogs Research Articles

Post mortem evaluation of spinal cord and protruded intervertebral discs in dogs without neurological abnormalities

ABSTRACT: The aim of this study was to verify the presence of protrusion of the intervertebral disc (IVD) causing compression of the spinal cord and/or roots of cauda equina in 30 dogs above seven years of age with no evidence of previous neurological abnormalities. After the occurrence of death or euthanasia, a laminectomy was performed from C2 to the sacral vertebra to verify the presence of IVD protrusions. The protruded IVD were macroscopically graded according to the Thompson scale, and the corresponding spinal cord segment was histologically analyzed for nervous tissue compression. Of the 30 dogs, twelve (40%) presented disc protrusion, and of these 12 dogs, seven (58%) presented more than one protruded disc. Disc protrusion was observed in 3.2% (25/780) of all IVD evaluated. Of the six chondrodystrophic dogs, five (83%) presented disc protrusion. Of the 24 nonchondrodystrophic dogs, seven (29%) presented IVD protrusion. The site that showed the highest frequency of protrusion was L4-L5 (6/25) followed by the L6-L7 region (3/25) and C6-C7 (3/25). Only two of the medullary segments evaluated showed histological changes, with presence of focal lymphocytic infiltration and multifocal mild hemorrhage in the gray matter. Under the conditions of this study, 40% of dogs older than seven years old showed IVD protrusions without showing neurological signs, with no abnormality of the nervous tissue in 92% of the evaluated segments. Thus, the protrusion of the IVD in some dogs, can only be a finding of no clinical relevance.

The Myth of Fibroid Degeneration in the Canine Intervertebral Disc: A Histopathological Comparison of Intervertebral Disc Degeneration in Chondrodystrophic and Nonchondrodystrophic Dogs.

Since the seminal work by Hans-Jörgen Hansen in 1952, it has been assumed that intervertebral disc (IVD) degeneration in chondrodystrophic (CD) dogs involves chondroid metaplasia of the nucleus pulposus, whereas in nonchondrodystrophic (NCD) dogs, fibrous metaplasia occurs. However, more recent studies suggest that IVD degeneration in NCD and CD dogs is more similar than originally thought. Therefore, the aim of this study was to compare the histopathology of IVD degeneration in CD and NCD dogs. IVDs with various grades of degeneration (Thompson grade I-III, n = 7 per grade) from both CD and NCD dogs were used (14 CD and 18 NCD dogs, 42 IVDs in total). Sections were scored according to a histological scoring scheme for canine IVD degeneration, including evaluation of the presence of fibrocyte-like cells in the nucleus pulposus. In CD dogs, the macroscopically non-degenerated nucleus pulposus contained mainly chondrocyte-like cells, whereas the non-degenerated nucleus pulposus of NCD dogs mainly contained notochordal cells. The histopathological changes in degenerated discs were similar in CD and NCD dogs and resembled chondroid metaplasia. Fibrocytes were not seen in the nucleus pulposus, indicating that fibrous degeneration of the IVD was not present in any of the evaluated grades of degeneration. In conclusion, intervertebral disc degeneration was characterized by chondroid metaplasia of the nucleus pulposus in both NCD and CD dogs. These results revoke the generally accepted concept that NCD and CD dogs suffer from a different type of IVD degeneration, in veterinary literature often referred to as chondroid or fibroid degeneration, and we suggest that chondroid metaplasia should be used to describe the tissue changes in the IVD in both breed types.

Magnetic resonance imaging versus computed tomography to plan hemilaminectomies in chondrodystrophic dogs with intervertebral disc extrusion.

To determine the influence of preoperative computed tomography (CT) versus magnetic resonance (MR) on hemilaminectomies planned to treat thoracolumbar (TL) intervertebral disc (IVD) extrusions in chondrodystrophic dogs. Prospective clinical study. Forty chondrodystrophic dogs with TL IVD extrusion and preoperative CT and MR studies. MR and CT images were randomized and reviewed by 4 observers masked to the dog's identity and corresponding imaging studies. Observers planned the location along the spine, side, and extent (number of articular facets to be removed) based on individual reviews of CT and MR studies. Intra-observer agreement was determined between overall surgical plan, location, side, and size of the hemilaminectomy planned on CT versus MR of the same dog. Similar surgical plans were developed based on MR versus CT in 43.5%-66.6% of dogs, depending on the observer. Intra-observer agreement in location, side, and size of the planned hemilaminectomy based on CT versus MR ranged between 48.7%-66.6%, 87%-92%, and 51.2%-71.7% of dogs, respectively. Observers tended to plan larger laminectomy defects based on MR versus CT of the same dog. Findings from this study indicated considerable differences in hemilaminectomies planned on preoperative MR versus CT imaging. Surgical location and size varied the most; the side of planned hemilaminectomies was most consistent between imaging modalities.

Prognostic Factors Associated with Recovery of Ambulation and Urinary Continence in Dogs with Acute Lumbosacral Spinal Cord Injury.

BackgroundLimited information is available about prognostic factors for recovery after spinal cord injury (SCI) to the L4‐S3 segments. Previous research suggests that L4‐S3 SCI does not have a worse prognosis than T3‐L3 SCI.Hypothesis/ObjectivesTo elucidate prognostic factors for regaining urinary continence and ambulation in dogs with L4‐S3 SCI and compare prognosis to T3‐L3 SCI.Animals/MethodsA retrospective study on 61 nonambulatory dogs with L4‐S3 SCI, matched to dogs with T3‐L3 SCI, compared 3 weeks after onset. Prognostic factors explored using logistic regression and used for matching: nonchondrodystrophic dogs >15 kg versus dogs that were chondrodystrophic or <15 kg; compressive versus noncompressive lesions; presence versus absence of conscious pain perception (CPP); and lower vs upper motor neuron (LMN/UMN) incontinence.ResultsFewer L4‐S3 dogs regained continence compared to T3‐L3 dogs (64 vs 85%, P = .0033), but no difference existed for regaining ambulation (66 vs 75%, P = .1306). In L4‐S3 SCI dogs, fewer dogs regained continence with loss of CPP (P < .001), LMN incontinence (P = .004), and noncompressive lesions (P = .006). Negative prognostic factors for regaining ambulation included absent CPP (P < .001) and large nonchondrodystrophic breed (P = .022).Conclusions and Clinical ImportanceDogs with L4‐S3 SCI have a poorer short‐term prognosis than do dogs with T3‐L3 SCI. Dogs with L4‐S3 SCI had a poor prognosis with loss of CPP, or noncompressive lesions combined with LMN incontinence. Small‐breed or chondrodystrophic dogs with retained CPP, compressive lesions, and UMN incontinence had an excellent prognosis. These findings may help guide decision‐making in L4‐S3 SCI.

Proportion recovery and times to ambulation for non-ambulatory dogs with thoracolumbar disc extrusions treated with hemilaminectomy or conservative treatment: A systematic review and meta-analysis of case-series studies

Thoracolumbar intervertebral disc extrusion is a common cause of spinal cord dysfunction in dogs. Peer-reviewed studies reporting treatment of predominantly chondrodystrophic dogs with disc extrusion with loss of ambulation with either hemilaminectomy or conservative treatment (rest, analgesics and anti-inflammatories) were evaluated in a systematic review of the literature.Generally, the level of evidence available was low with no controlled studies and only case series available. In the meta-analysis, there was a clear trend to a greater proportion of dogs recovering and returning faster to ambulation for dogs treated with hemilaminectomy than for conservatively treated dogs. The mean proportions that recovered for neurological grades 3, 4 and 5 were 93, 93 and 61% for those treated with hemilaminectomy, and 79, 62 and 10% for those treated conservatively (Grade 3 – non-ambulatory paraparetic dogs; grade 4 – paraplegic dogs with intact deep pain perception; grade 5 – paraplegic dogs without intact deep pain perception). Due to the use of case series, these results represent between-study comparisons, thereby increasing the risk of selection bias and other biases. Data presented in this review support the current recommendations for surgical management of non-ambulatory dogs with disc-extrusion, but controlled clinical studies comparing outcomes are necessary to confirm these findings.

Influence of chondrodystrophy and brachycephaly on geometry of the humerus in dogs.

To assess the geometry of canine humeri as seen on radiographs in chondrodystrophic dogs (CD) and brachycephalic dogs (BD) compared to non-chondrodystrophic dogs (NCD). Mediolateral (ML) and craniocaudal (CC) radiographs of skeletally mature humeri were used (CD [n = 5], BD [n = 9], NCD [n = 48]) to evaluate general dimensions (length, width, canal flare, cortical thickness), curvature (shaft, humeral head, and glenoid), and angulation (humeral head and condyle). Measurements from CD, BD, and NCD were compared. Mean humeral length was shorter in CD (108 mm) compared to BD (184 mm, p = 0.001) and NCD (183 mm, p <0.001). Craniocaudal cortical thickness at 70% of humeral length and ML cortical thickness at 30%, 50%, and 70% of humeral length were less in CD compared to BD and NCD. Humeral shaft curvature was greater in CD (9.9°) compared to BD (6.7°, p = 0.023). The ratio of glenoid radius of curvature / humeral length was greater for CD (11.1%) compared to NCD (9.7%, p = 0.013). The ratio of humeral width / humeral length was greater for BD (29.4%) compared to NCD (26.2%, p = 0.043). The ratio of glenoid length / humeral length was greater in CD (18.0%) than BD (16.4%, p = 0.048) and NCD (15.6%, p <0.001). Bone proportions and curvature in CD differ from BD and NCD. Differences are minor and unlikely to have clinical significance.

Canine chondrodystrophic intervertebral disc disease (Hansen type I disc disease)

Intervertebral disc disease (IVDD) is the most common spinal disease in dogs. Chondrodystrophic dogs, which have disproportionably short and curved limbs, are predisposed to Hansen type I IVDD and of these the miniature Dachshund is over represented [1,2], is more likely to be presented at an earlier age [3] and is at greater risk of a severe spinal cord injury [4]. The tendency for IVDD in Dachshunds is inherited [5,6] and a major locus on chromosome 12 harbours genetic variations affecting the development of intervertebral disc calcification [7]. Hansen type I disc degeneration is thought to occur because of loss of notochordal cells which produce proteoglycans which “hold water” in the disc. Chondrodystrophic dogs have a primary deficiency of notochordal cells, a study found that large notochordal cells in the nucleus pulposus of chondrodystrophoid dogs formed 13% of the cell population in young dogs and fell to 0.4% in adults, whereas they were the predominant cell type in the nonchondrodystrophoid dogs at all ages [8]. Thus chondrodystrophoid dogs suffer early degenerative changes in the disc and a concomitant reduction in proteoglycan content, increased collagen, and loss of water content making the discs likely to herniate [8]. Certain lifestyle factors may increase or decrease risk of IVDD and this is currently under investigation. There is a suggestion that exercise (including stair climbing) reduces the incidence of disc calcification [9]. By contrast it has been hypothesized that obesity/lack of postural muscle strength may increase risk. Dachshunds with intervertebral disc extrusion had significantly smaller cross sectional area and greater fat infiltration in the epaxial muscles (muscles which lie dorsal to the horizontal septum of the vertebrae which mobilize and globally stabilize the trunk [10]) compared to dogs presenting with fibrocartilagenous embolism (another acute onset intervertebral disc related spinal disease) [11]. In addition chondrodystrophic dogs may have increased risk of IVVD if they have a more extreme conformation e.g. Dachshunds that have a longer back and shorter limbs are more at risk [12] and breeds with a comparatively heavy head such as the Bassett Hound may be more at risk of cervical disc disease. Breeds with a tendency for kyphoscoliosis such as the French Bulldog may be more at risk of IVDD in the IVDs adjacent to a vertebral malformation [13,14]. This presentation details the pathogeneis, clinical presentation, diagnosis and treatment of IVDD in chondrodystrophic dogs.

MRI-based relationships between spine pathology, intervertebral disc degeneration, and muscle fatty infiltration in chondrodystrophic and non-chondrodystrophic dogs

Background ContextHuman studies have revealed a link between muscle degeneration and low back pain, although the cause and effect of this relationship is not clear. Dogs provide a naturally developing model of intervertebral disc (IVD)-related low back pain that may provide insight into relationships between IVD and muscle degeneration. PurposeThis study aimed to quantify, via magnetic resonance imaging (MRI), the magnitude and location of fatty infiltration in spine muscles of chondrodystrophic (CD) and non-chondrodystrophic (NCD) dogs suffering from both intervertebral disc herniation (IVDH) and non-disc-related spinal disorders, and relate this to intervertebral disc degeneration (IVDD). Study DesignThis study used retrospective MRI-based analysis of IVDD and muscle fatty infiltration in CD and NCD dogs. MethodsA portion of this study was funded ($1,000) by the Pet Trust Fund, Ontario Veterinary College. Magnetic resonance imaging from 180 dogs were separated into four groups: (1) CD with IVDH; (2) CD with non-IVDH spinal pathology; (3) NCD with IVDH; (4) NCD with non-IVDH spinal pathology. For each dog at intervertebral levels T12–T13 to L6–L7, IVDD was subjectively graded and muscle-fat indices (MFIndices) were quantified for multifidus, erector spinae, and psoas muscle groups. ResultsIntervertebral disc degeneration grade was higher (p<.0001) for CD compared with NCD dogs, and for dogs diagnosed with IVDH compared with dogs with non-IVDH pathology. Muscle-fat indices of multifidus and psoas were higher (p<.01), indicating greater fatty infiltration, for NCD compared with CD dogs, and for dogs with non-IVDH pathology compared with dogs with IVDH. Erector spinae demonstrated higher (p<.0001) MFIndices compared with multifidus and psoas; however, this level of fatty infiltration was not dependent upon breed or pathology. ConclusionsDog groups with higher average IVDD grades demonstrated less fatty infiltration within their multifidus and psoas muscles, compared with groups with lower IVDD grades. This finding was consistent across both CD and NCD breeds as well as across dogs presenting with IVDH and those presenting with a non-IVDH spinal pathology. Thus, the presence or severity of IVDD is not uniquely related to fatty infiltration in these muscles, but rather the presence, or possibly severity or chronicity, of general spine pathology is likely a better predictor of fatty infiltration.

Assessment of Intrathecal Pressure in Chondrodystrophic Dogs With Acute Thoracolumbar Disk Disease.

To assess intrathecal pressure (ITP) in chondrodystrophic dogs with thoracolumbar disk extrusion. Prospective cohort study. Group 1: 11 chondrodystrophic dogs with thoracolumbar disk extrusion and present deep pain sensation. Group 2 (control): 3 healthy chondrodystrophic laboratory dogs without spinal disease. Diagnosis was based on neurologic signs, magnetic resonance imaging (MRI) findings, and surgical confirmation. Blood pressure was maintained within physiologic range during anesthesia. A standardized surgical procedure was applied to minimize factors that could influence measurement readings. An extended hemilaminectomy was performed and ITP was measured with a fiber optic catheter. The catheter was inserted in the subarachnoid space 1 spinal segment caudal to the level of herniation and its tip was advanced to the site of compression. Significantly higher ITP occurred in chondrodystrophic dogs with acute thoracolumbar disk disease compared with controls. ITP was not associated with duration of clinical signs, neurologic status, outcome, degree of spinal cord compression, or signal intensity changes as assessed by MRI. Acute thoracolumbar disk disease leads to elevated ITP in chondrodystrophic dogs, which may contribute to increased compression of spinal cord parenchyma.

Assessment of Intrathecal Pressure in Chondrodystrophic Dogs With Acute Thoracolumbar Disk Disease

Assessment of Intrathecal Pressure in Chondrodystrophic Dogs With Acute Thoracolumbar Disk Disease

Conditioned medium derived from notochordal cell-rich nucleus pulposus tissue stimulates matrix production by canine nucleus pulposus cells and bone marrow-derived stromal cells.

Conditioned medium derived from notochordal cell-rich nucleus pulposus tissue (NCCM) was previously shown to have a stimulatory effect on bone marrow stromal cells (BMSCs) and nucleus pulposus cells (NPCs) individually, in mixed species in vitro cell models. The objective of the current study was to assess the stimulatory effect of NCCM on NPCs in a homologous canine in vitro model and to investigate whether combined stimulation with NCCM and addition of BMSCs provides a synergistic stimulatory effect. BMSCs and NPCs were harvested from chondrodystrophic dogs with confirmed early intervertebral disc (IVD) degeneration. NCCM was produced from NP tissue of nonchondrodystrophic dogs with healthy IVDs. BMSCs or NPCs alone (3×10(6) cells/mL) and NPCs+BMSCs (6×10(6) cells/mL; mixed 1:1) were cultured for 4 weeks in 1.2% alginate beads under base medium (BM), NCCM, or with addition of 10 ng/mL transforming growth factor-β1 (TGF-β1) as a positive control. Beads were assessed for glycosaminoglycan (GAG) and DNA contents by biochemical assays, GAG deposition by Alcian blue staining, and gene expression (aggrecan, versican, collagen 1 and 2, SOX9, A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), and matrix metalloproteinase 13 [MMP13]) with real-time quantitative RT-PCR. NCCM increased NPC proliferation, proteoglycan production, and expression of genes associated with a healthy NP-like phenotype. BMSCs also showed increased proteoglycan production under NCCM, but these effects were not observed at the gene level. Combined stimulation of NPCs with NCCM and coculturing with BMSCs did not result in increased proteoglycan content compared to stimulation with NCCM alone. NCCM stimulates matrix production by both NPCs and BMSCs and directs NPCs toward a healthier phenotype. NCCM is therefore promising for IVD regeneration and identification of the bioactive components will be helpful to further develop this approach. In the current study, no synergistic effect of adding BMSCs was observed.

Medical Infrared Imaging (Thermography) of Type I Thoracolumbar Disk Disease in Chondrodystrophic Dogs

To: (1) determine the success of medical infrared imaging (MII) in identifying dogs with TLIVDD, (2) compare MII localization with magnetic resonance imaging (MRI) results and surgical findings, and (3) determine if the MII pattern returns to that of normal dogs 10 weeks after decompression surgery. Prospective case series. Chondrodystrophic dogs (n = 58) with Type I TLIVDD and 14 chondrodystrophic dogs with no evidence of TLIVDD. Complete neurologic examination, MII, and MRI studies were performed on all dogs. Dogs with type I TLIVDD had decompressive surgery and follow-up MII was performed at 10 weeks. Pattern analysis software was used to differentiate between clinical and control dogs, and statistical analysis using anatomic regions of interest on the dorsal views were used to determine lesion location. Recheck MII results were compared with control and pre-surgical images. Computer recognition pattern analysis was 90% successful in differentiating normal dogs from dogs affected by TLIVDD and 97% successful in identifying the abnormal intervertebral disc space in dogs with TLIVDD. Statistical comparisons of the ROI mean temperature were unable to determine the location of the disc herniation. Recheck MII patterns did not normalize and more closely resembled the clinical group. MII was 90% successful differentiating between normal dogs and 97% successful in identifying the abnormal intervertebral disc space in dogs with TLIVDD. Abnormal intervertebral disc space localization using ROI mean temperature analysis was not successful. MII patterns 10 weeks after surgery do not normalize.

Original surgical treatment of thoracolumbar subarachnoid cysts in six chondrodystrophic dogs.

BackgroundSubarachnoid cysts are rare conditions in veterinary medicine, associated with spinal cord dysfunction. Most of the 100 cases of subarachnoid cysts described since the first report in 1968 were apparently not true cysts. Reported cysts are usually situated in the cervical area and occur in predisposed breeds such as the Rottweiler. The purpose of this retrospective study, from May 2003 to April 2012, was to describe the distinctive features of thoracolumbar spinal subarachnoid cysts, together with their surgical treatment and outcome in 6 chondrodystrophic dogs.ResultsFive Pugs and 1 French Bulldog were examined. Images suggestive of a subarachnoid cyst were obtained by myelography (2/6) and computed tomography myelography (4/6), and associated disc herniation was observed in 3/6 dogs. A hemilaminectomy was performed. The protruding disc eventually found in 5/6 dogs was treated by lateral corpectomy. The ventral leptomeningeal adhesions observed in all dogs after durotomy were dissected. No or only mild post-operative neurological degradation was observed. Follow-up studies (7 months to 4 years) indicated good outcome and no recurrence.ConclusionsAll the thoracolumbar subarachnoid cysts described in these 6 chondrodystrophic dogs were associated with leptomeningeal adhesions. Good results seemed to be obtained by dissecting and removing these adhesions. A protruding disc, found here in 5/6 dogs, needs to be ruled out and can be treated by lateral corpectomy.

Stimulation of Canine Nucleus Pulposus Cells and Bone Marrow-Derived Stromal Cells with Notochordal Cell-Secreted Factors

IntroductionIntervertebral disc (IVD) degeneration, a major cause for low back pain, is characterized by a decreasing number of nucleus pulposus cells (NPCs),1 which are then unable to maintain a h...

Canine epidermal neural crest stem cells: characterization and potential as therapy candidate for a large animal model of spinal cord injury.

The discovery of multipotent neural crest-derived stem cells, named epidermal neural crest stem cells (EPI-NCSC), that persist postnatally in an easy-to-access location-the bulge of hair follicles-opens a spectrum of novel opportunities for patient-specific therapies. We present a detailed characterization of canine EPI-NCSC (cEPI-NCSC) from multiple dog breeds and protocols for their isolation and ex vivo expansion. Furthermore, we provide novel tools for research in canines, which currently are still scarce. In analogy to human and mouse EPI-NCSC, the neural crest origin of cEPI-NCSC is shown by their expression of the neural crest stem cell molecular signature and other neural crest-characteristic genes. Similar to human EPI-NCSC, cEPI-NCSC also expressed pluripotency genes. We demonstrated that cEPI-NCSC can generate all major neural crest derivatives. In vitro clonal analyses established multipotency and self-renewal ability of cEPI-NCSC, establishing cEPI-NCSC as multipotent somatic stem cells. A critical analysis of the literature on canine spinal cord injury (SCI) showed the need for novel treatments and suggested that cEPI-NCSC represent viable candidates for cell-based therapies in dog SCI, particularly for chondrodystrophic dogs. This notion is supported by the close ontological relationship between neural crest stem cells and spinal cord stem cells. Thus, cEPI-NCSC promise to offer not only a potential treatment for canines but also an attractive and realistic large animal model for human SCI. Taken together, we provide the groundwork for the development of a novel cell-based therapy for a condition with extremely poor prognosis and no available effective treatment.

Potential regenerative treatment strategies for intervertebral disc degeneration in dogs

Pain due to spontaneous intervertebral disc (IVD) disease is common in dogs. In chondrodystrophic (CD) dogs, IVD disease typically develops in the cervical or thoracolumbar spine at about 3–7 years of age, whereas in non-chondrodystrophic (NCD) dogs, it usually develops in the caudal cervical or lumbosacral spine at about 6–8 years of age. IVD degeneration is characterized by changes in the biochemical composition and mechanical integrity of the IVD. In the degenerated IVD, the content of glycosaminoglycan (GAG, a proteoglycan side chain) decreases and that of denatured collagen increases. Dehydration leads to tearing of the annulus fibrosus (AF) and/or disc herniation, which is clinically characterized by pain and/or neurological signs. Current treatments (physiotherapy, anti-inflammatory/analgesic medication, surgery) for IVD disease may resolve neurological deficits and reduce pain (although in many cases insufficient), but do not lead to repair of the degenerated disc. For this reason, there is interest in new regenerative therapies that can repair the degenerated disc matrix, resulting in restoration of the biomechanical function of the IVD. CD dogs are considered a suitable animal model for human IVD degeneration because of their spontaneous IVD degeneration, and therefore studies investigating cell-, growth factor-, and/or gene therapy-based regenerative therapies with this model provide information relevant to both human and canine patients. The aim of this article is to review potential regenerative treatment strategies for canine IVD degeneration, with specific emphasis on cell-based strategies.

A Prospective Evaluation of CT in Acutely Paraparetic Chondrodystrophic Dogs

The clinical usefulness of computed tomography (CT) as a sole diagnostic modality in identifying disc lesion(s) in chondrodystrophic breeds presenting with acute signs of intervertebral disc disease (IVDD) is incompletely characterized. CT was used prospectively to determine the validity of this tool. Neurologic examinations and CT scans were performed on all dogs at presentation. Surgical decompression was based on those findings. Clinical follow-up examinations were performed on days 1 and 14 postsurgically. CT detected a lesion consistent with clinical findings in 63 of 69 cases (91%). All 63 dogs with Hansen type I IVDD lesions were identified on CT alone. The surgeon and radiologist agreed on lesion level in 72 of 78 lesions (92%) and lateralization in 71 of 78 lesions (91%). Improvement in neurologic grade was documented in 60 of 69 dogs (87%) by 14 days. CT imaging can be used as a single imaging modality in chondrodystrophic dogs presenting with acute paresis. CT used in this manner is a reliable and noninvasive tool for detecting spinal compression secondary to IVDD in chondrodystrophic dogs.

Magnetic resonance imaging findings in dogs with traumatic intervertebral disk extrusion with or without spinal cord compression: 31 cases (2006–2010)

To determine the prevalence of spinal cord compression subsequent to traumatic intervertebral disk (IVD) extrusion in dogs, characterize factors associated with spinal cord compression in dogs with traumatic IVD extrusion, and evaluate the outcomes of dogs with traumatic IVD extrusion with or without spinal cord compression. Retrospective case series. 31 dogs with traumatic IVD extrusion. Medical records and MRI findings were reviewed for dogs with a history of trauma to the spinal region. Dogs were included in the study if a neurologic examination and MRI were performed and there was a description of clinical signs and MRI findings including identification of the spinal cord segment affected by IVD extrusion, presence or absence of spinal cord compression, treatment, and outcome available for review. 31 of 50 (62%) dogs had traumatic IVD extrusions without any other detectable vertebral lesions; 9 (29%) and 22 (71%) of those 31 dogs did and did not have spinal cord compression, respectively. Dogs with spinal cord compression were significantly older and more likely to be chondrodystrophic and have evidence of generalized IVD degeneration, compared with dogs without spinal cord compression. The outcome for dogs with spinal cord compression was similar to that for dogs without spinal cord compression. Results indicated traumatic IVD extrusion was common and should be considered as a differential diagnosis for dogs with trauma to the spinal region, and spinal cord compression should be evaluated, especially in older or chondrodystrophic dogs.

Gene expression profiling of early intervertebral disc degeneration reveals a down-regulation of canonical Wnt signaling and caveolin-1 expression: implications for development of regenerative strategies

IntroductionEarly degeneration of the intervertebral disc (IVD) involves a change in cellular differentiation from notochordal cells (NCs) in the nucleus pulposus (NP) to chondrocyte-like cells (CLCs). The purpose of this study was to investigate the gene expression profiles involved in this process using NP tissue from non-chondrodystrophic and chondrodystrophic dogs, a species with naturally occurring IVD degeneration.MethodsDual channel DNA microarrays were used to compare 1) healthy NP tissue containing only NCs (NC-rich), 2) NP tissue with a mixed population of NCs and CLCs (Mixed), and 3) NP tissue containing solely CLCs (CLC-rich) in both non-chondrodystrophic and chondrodystrophic dogs. Based on previous reports and the findings of the microarray analyses, canonical Wnt signaling was further evaluated using qPCR of relevant Wnt target genes. We hypothesized that caveolin-1, a regulator of Wnt signaling that showed significant changes in gene expression in the microarray analyses, played a significant role in early IVD degeneration. Caveolin-1 expression was investigated in IVD tissue sections and in cultured NCs. To investigate the significance of Caveolin-1 in IVD health and degeneration, the NP of 3-month-old Caveolin-1 knock-out mice was histopathologically evaluated and compared with the NP of wild-type mice of the same age.ResultsEarly IVD degeneration involved significant changes in numerous pathways, including Wnt/β-catenin signaling. With regard to Wnt/β-catenin signaling, axin2 gene expression was significantly higher in chondrodystrophic dogs compared with non-chondrodystrophic dogs. IVD degeneration involved significant down-regulation of axin2 gene expression. IVD degeneration involved significant down-regulation in Caveolin-1 gene and protein expression. NCs showed abundant caveolin-1 expression in vivo and in vitro, whereas CLCs did not. The NP of wild-type mice was rich in viable NCs, whereas the NP of Caveolin-1 knock-out mice contained chondroid-like matrix with mainly apoptotic, small, rounded cells.ConclusionsEarly IVD degeneration involves down-regulation of canonical Wnt signaling and Caveolin-1 expression, which appears to be essential to the physiology and preservation of NCs. Therefore, Caveolin-1 may be regarded an exciting target for developing strategies for IVD regeneration.

Gene Expression Profiling of Early Intervertebral Disk Degeneration

Introduction Early degeneration of the IVD involves a change in the nucleus pulposus (NP) cell population, characterized by the replacement/differentiation of the native notochordal cells (NCs) by/into chondrocyte-like cells (CLCs). In this respect, the NC has received considerable attention as a potential NP progenitor cell and as a target to realize disk regeneration.1,2 The canine species is affected by naturally occurring IVD degeneration, like humans.3 Moreover, with regard to the maintenance of NCs and the occurrence of IVD degeneration, the canine species reveals a unique phenomenon. In chondrodystrophic dogs, NCs are replaced by CLCs before the age of 1 year, with a concurrent onset of IVD degeneration at all spinal levels. By contrast, in nonchondrodystrophic dogs the NC remains the predominant cell type of the NP during the majority of life; replacement of NCs by CLCs and concurrent IVD degeneration only occur at old age. The aim of this study is to investigate gene expression profiles in the process of early NP degeneration, thereby revealing potential biomolecular signaling pathways for IVD regeneration. Materials and Methods Canine IVD samples from chondrodystrophic and nonchondrodystrophic dogs were classified into (1) NP rich in NCs, (2) NP containing both NCs and CLC-cells (Mixed), and (3) early degenerated NP rich in CLCs (Fig. 1). Gene expression profiling of the NP of these three groups was performed using a two-color cDNA-microarray, with subsequent validation (qPCR and immunohistochemistry) in IVD samples and cultures of primary NCs. Results Early IVD degeneration involved significant regulations of various pathways, including extracellular matrix (ECM) remodeling, plasmin, and plasminogen activator urokinase. Bone Morphogenetic Protein (BMP)-, and Wnt/β-catenin-signaling and cytoskeleton remodeling. Wnt/β-catenin signaling plays a crucial role in maintaining the notochordal fate during embryogenesis and stem-cell fate determination, but is also involved in IVD degeneration and regeneration. Whether the differential expression of Wnt/β-catenin-signaling is associated with degeneration or is an attempt to repair the damaged IVD remains uncertain. Both NCs and CLCs showed nuclear and cytoplasmic expression of the Wnt effector protein β-catenin4; axin2 gene expression, a specific read-out for Wnt signaling, revealed a dual response: in the initial stages of NP degeneration tended to increase (Mixed group), but diminished with ongoing degeneration (CLC-rich group). A concurrent increase in Wnt inhibitory factor 1 gene expression was observed, which may be a significant factor involved in the downregulation of canonical Wnt signaling in the chondrodystrophic dogs.5 Caveolin-1, which is known to regulate canonical Wnt signaling,6 emerged as a significantly regulated gene. NCs in culture showed robust caveolin-1 gene and protein expression and IVD degeneration involved significant decrease in Caveolin-1 gene and protein expression. Conclusion Early IVD degeneration involves significant alterations in biomolecular pathways involved in ECM synthesis, cell-matrix interactions, and cytoskeletal remodeling. Subclinical, early IVD degeneration is associated with diminished Wnt/β-catenin signaling activity. In this process, caveolin-1 expression appears to be a relevant factor in NC physiology and thus maintenance of the healthy NP. I confirm having declared any potential conflict of interest for all authors listed on this abstract No Disclosure of Interest None declared Risbud MV, Shapiro IM. Notochordal cells in the adult intervertebral disc: new perspective on an old question. Critical Reviews in Eukaryotic Gene Expression 2011;21(1):29–41 Erwin WM. The enigma that is the nucleus pulposus cell: the search goes on. Arthritis Research and Therapy 2010;12(3):118 Bergknut N, et al. The dog as an animal model for intervertebral disc degeneration? Spine (Phila Pa 1976) 2011; Epub ahead of print Smolders LA, et al. Basal canonical Wnt signaling of the notochordal cells is upregulated during the process of intervertebral disc degeneration. Journal of orthopaedic Research 2011; Epub ahead of print Surmann-Schmitt C, et al. Wif-1 is expressed at cartilage-mesenchyme interfaces and impedes Wnt3a-mediated inhibition of chondrogenesis. Journal of cell Science 2009;122(Pt 20):3627–3637 Yamamoto H, et al. Caveolin is necessary for Wnt-3a-dependent internalization of LRP6 and accumulation of beta-catenin. Developmental Cell 2006;11(2):213–223