Intravitreal implantation of TPP1-transduced stem cells delays retinal degeneration in canine CLN2 neuronal ceroid lipofuscinosis.

The CLN2 form of neuronal ceroid lipofuscinosis is a neurodegenerative disease that results from mutations in the TPP1 gene. Affected children exhibit progressive declines in most neurological functions including vision. Functional declines are accompanied by progressive brain and retinal atrophy. TPP1 encodes the soluble lysosomal enzyme tripeptidyl peptidase-1 (TPP1). Dachshunds with a TPP1 null mutation exhibit a disorder very similar to human CLN2 disease. Periodic infusion of recombinant TPP1 protein or a single injection of a TPP1 gene therapy vector into the cerebrospinal fluid of affected dogs significantly delays the onset and progression of neurological signs but does not slow vision loss or retinal degeneration. Studies were conducted to determine whether intravitreal implantation of autologous bone marrow derived stem cells transduced with a TPP1 expression construct would inhibit retinal degeneration in the canine model. A single injection of the transduced cells at an early stage in the disease progression substantially inhibited the development of disease-related retinal function deficits and structural changes. No adverse effects of the treatment were detected. These findings indicate that ex vivo gene therapy using autologous stem cells is an effective means of achieving sustained delivery of therapeutic compounds to tissues such as the retina for which systemic administration would be ineffective.

Brain diffusion tensor imaging in dogs with degenerative myelopathy.

BACKGROUND: Degenerative myelopathy (DM) in dogs shares similarities with superoxide dismutase 1-associated human amyotrophic lateral sclerosis (ALS). Brain microstructural lesions are quantified using diffusion tensor imaging (DTI) in ALS patients. OBJECTIVE: Characterize brain neurodegenerative changes in DM-affected dogs using DTI. ANIMALS: Sixteen DM-affected and 8 control dogs. METHODS: Prospective observational study. Brain DTI was performed at baseline and every 3 months on DM-affected dogs and compared to controls. Fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were calculated on specified regions of interest. Gait scores (0, normal to 14, tetraplegia) were assigned at each scan. Diffusion tensor imaging values in DM-affected dogs were compared to controls, gait scores, and evaluated over time. RESULTS: Mean age was 5.7 years (SD 3.2) in controls and 9.7 years (SD 1.4) in DM-affected dogs. In DM-affected dogs, mean baseline gait score was 4 (SD 1), and mean score change from baseline to last scan was 4.82 (SD 2.67). Nine dogs had ≤3 scans; 7 had >3 scans. Accounting for age, no differences in DTI indices were identified for any brain or proximal spinal cord regions between DM-affected dogs and controls (P > .05). Diffusion tensor imaging values poorly correlated with gait scores (R2 < .2). No significant changes were identified in diffusion indices over time (P > .05). CONCLUSIONS AND CLINICAL IMPORTANCE: Diffusion tensor imaging indices did not differentiate DM-affected from control dogs, detect longitudinal changes, or differentiate disease severity. Findings do not yet support brain DTI as an imaging biomarker.

Clinical Presentation of Chiari-like Malformation in 2 Persian Cats.

Two Persian breed cats, 10 and 5 years of age, were presented separately for difficulty prehending food as well as behavioral abnormalities including interanimal aggression and restlessness, pacing, or compulsive overgrooming. Both cats would regularly rest their head and neck in an extended position. Neurologic examination demonstrated calvarial and craniocervical junction pain in both and an L4-S3 myelopathy in one. Brain MRI of both cases, and CT and necropsy in 1 case, demonstrated ventriculomegaly and caudal fossa crowding, cerebellar indentation, and foramen magnum herniation consistent with Chiari-like malformation. No syringomyelia was present in either cat. The 2 cats were treated with anti-inflammatory doses of prednisolone with little to no clinical response, but experienced improvement with pregabalin and omeprazole. The 2 cats' clinical signs were consequently attributed to neuropathic and posture-related pain secondary to Chiari-like malformation. Persian breed cats may have a predisposition to Chiari-like malformation, which may not be solely a morphometric variant, and symptomatic cats may present with manifestations of neuropathic pain different from the classic signs reported in dogs.

AAV gene transfer delays disease onset in a TPP1-deficient canine model of the late infantile form of Batten disease.

The most common form of the childhood neurodegenerative disease late infantile neuronal ceroid lipofuscinosis (also called Batten disease) is caused by deficiency of the soluble lysosomal enzyme tripeptidyl peptidase 1 (TPP1) resulting from mutations in the TPP1 gene. We tested whether TPP1 gene transfer to the ependyma, the epithelial lining of the brain ventricular system, in TPP1-deficient dogs would be therapeutically beneficial. A one-time administration of recombinant adeno-associated virus (rAAV) expressing canine TPP1 (rAAV.caTPP1) resulted in high expression of TPP1 predominantly in ependymal cells and secretion of the enzyme into the cerebrospinal fluid leading to clinical benefit. Diseased dogs treated with rAAV.caTPP1 showed delays in onset of clinical signs and disease progression, protection from cognitive decline, and extension of life span. By immunostaining and enzyme assay, recombinant protein was evident throughout the brain and spinal cord, with correction of the neuropathology characteristic of the disease. This study in a naturally occurring canine model of TPP1 deficiency highlights the utility of AAV transduction of ventricular lining cells to accomplish stable secretion of recombinant protein for broad distribution in the central nervous system and therapeutic benefit.

Protein C activity in dogs: adaptation of a commercial human colorimetric assay and evaluation of effects of storage time and temperature.

Objectives of this study were to adapt a commercial human protein C (PC) colorimetric assay for use in dogs and to investigate effects of various storage conditions. The human assay was modified by using pooled canine plasma for calibration and by increasing the activation time. PC activity was measured in fresh canine plasma and in plasma stored under various conditions. PC activity of some stored samples was significantly different from that of fresh plasma; however, differences were small. No difference was detected in samples stored under similar conditions but analyzed in different laboratories using similar methodology. Results of this study indicate that the human colorimetric assay is suitable for canine samples if pooled canine plasma is used for calibration, that Clinical and Laboratory Standards Institute sample storage guidelines developed for testing in humans are appropriate for dogs, and that comparisons of results from laboratories using similar methodology are legitimate.