Andrea Carvalho

The db/db mouse: a useful model for the study of diabetic retinal neurodegeneration.

Background To characterize the sequential events that are taking place in retinal neurodegeneration in a murine model of spontaneous type 2 diabetes (db/db mouse). Methods C57BLKsJ-db/db mice were used as spontaneous type 2 diabetic animal model, and C57BLKsJ-db/+ mice served as the control group. To assess the chronological sequence of the abnormalities the analysis was performed at different ages (8, 16 and 24 weeks). The retinas were evaluated in terms of morphological and functional abnormalities [electroretinography (ERG)]. Histological markers of neurodegeneration (glial activation and apoptosis) were evaluated by immunohistochemistry. In addition glutamate levels and glutamate/aspartate transporter (GLAST) expression were assessed. Furthermore, to define gene expression changes associated with early diabetic retinopathy a transcriptome analyses was performed at 8 week. Furthermore, an additional interventional study to lower blood glucose levels was performed. Results Glial activation was higher in diabetic than in non diabetic mice in all the stages (p<0.01). In addition, a progressive loss of ganglion cells and a significant reduction of neuroretinal thickness were also observed in diabetic mice. All these histological hallmarks of neurodegeneration were less pronounced at week 8 than at week 16 and 24. Significant ERG abnormalities were present in diabetic mice at weeks 16 and 24 but not at week 8. Moreover, we observed a progressive accumulation of glutamate in diabetic mice associated with an early downregulation of GLAST. Morphological and ERG abnormalities were abrogated by lowering blood glucose levels. Finally, a dysregulation of several genes related to neurotransmission and oxidative stress such as UCP2 were found at week 8. Conclusions Our results suggest that db/db mouse reproduce the features of the neurodegenerative process that occurs in the human diabetic eye. Therefore, it seems an appropriate model for investigating the underlying mechanisms of diabetes-induced retinal neurodegeneration and for testing neuroprotective drugs.

Increased HAS2‐driven hyaluronic acid synthesis in shar‐pei dogs with hereditary cutaneous hyaluronosis (mucinosis)

The Chinese shar-pei dog is known for its distinctive feature of wrinkled and thickened skin, defined as primary or hereditary cutaneous mucinosis. In a recent report, we identified the mucinous material deposited in the shar-pei skin as the polysaccharide hyaluronan (HA). In the present work, the molecular and cellular mechanisms underlying this phenotype have been identified in dermal fibroblasts isolated from shar-pei dogs. The production of HA, which appeared to be mainly associated with cell membrane protrusions and also intracellular, was higher in shar-pei fibroblasts than in control cells. The HA accumulation is related to a higher mRNA expression of the isoform HAS2 of the HA-synthesizing enzyme family, hyaluronan synthases (HAS). The higher expression of HAS2 in shar-pei fibroblasts was confirmed at the protein level. The other HAS isoenzymes, HAS1 and HAS3, and the HA-degrading enzymes, Hyal1 and Hyal2, were not differentially expressed in shar-pei fibroblasts compared with cells from control dogs. Fibroblasts from shar-pei dogs and from control dogs are morphologically different as observed by transmission electron microscopy. Scanning electron microscopy revealed a large number of cellular protrusions with associated globular deposits. Electron microscopy after labelling with biotinylated HA-binding protein confirmed an increased HA content in shar-pei fibroblasts, which could be localized in several subcellular structures. The authors propose the name hereditary cutaneous hyaluronosis (HCH) for affected dogs, because it better defines the cutaneous mucinosis of shar-pei dogs.

Benign intraocular teratoid medulloepithelioma causing glaucoma in an 11‐year‐old Arabian mare

CASE DESCRIPTION An 11-year-old Arabian mare was presented for investigation of a visible, pale-colored intraocular mass in the right eye. CLINICAL FINDINGS An intraocular mass was detected clinically and ultrasonographically as originating from the superior temporal quadrant of the ciliary body and iris and causing secondary glaucoma. The echodense mass was occupying the majority of the vitreous chamber and extended into the anterior chamber. The left eye appeared normal. TREATMENT AND OUTCOME Enucleation was recommended for therapeutic and diagnostic purposes. No adjuvant treatment was given. Histopathological examination demonstrated a benign intraocular teratoid medulloepithelioma located at the ciliary body. Immunohistochemical studies showed that neoplastic cells were positive for vimentin, S-100 protein, neuron-specific enolase (NSE), and nestin and negative for glial fibrillary acidic protein (GFAP). Electron microscopy revealed abundant cellular matrix and blood vessels surrounding tumor cells, which had indented, round to oval nuclei. There were also apoptotic bodies and cells containing melanosomes of variable shape and size. Eight years later, the horse has had no recurrence and maintains normal vision in the left eye. CLINICAL RELEVANCE This is the first report of a benign teratoid intraocular medulloepithelioma in an adult horse and the ultrastructural and immunohistochemical characterization of a teratoid medulloepithelioma in this species.