Early morphogenesis of the canine lens capsule, tunica vasculosa lentis posterior, and anterior vitreous body. A transmission electron microscopic study

Surgical management and histologic and immunohistochemical features of a cataract and retrolental plaque secondary to persistent hyperplastic tunica vasculosa lentis/persistent hyperplastic primary vitreous (PHTVL/PHPV) in a Bloodhound puppy

The objective of this study was to describe the clinical, histologic and immunohistochemical features, the surgical treatment, and outcome of a cataract secondary to persistent hyperplastic tunica vasculosa lentis/persistent hyperplastic primary vitreous (PHTVL/PHPV) in a dog. A 4-month-old male Bloodhound dog presented for evaluation of a cataract. A complete ophthalmic examination and ocular ultrasonography were performed. A resorbing cataract with intralenticular hemorrhage, lens induced uveitis, and PHTVL/PHPV were diagnosed. Extracapsular cataract extraction using phacoemulsification was performed. A primary posterior capsulectomy was performed to remove a retrolental plaque with the posterior capsule; the excised plaque was submitted for histopathology and immunohistochemical staining. A 41-Diopter intraocular lens (IOL) was implanted. Functional vision was maintained postoperatively during the 21-month follow-up period. Histologically, the posterior capsule was coiled and exhibited duplication. The retrolental plaque was comprised of dense fibrous connective tissue, blood vessels, free red blood cells, hemosiderin-laden macrophages, a pocket of neural tissue and numerous perivascular mast cells. With immunohistochemical staining, the neural elements were determined to be glial cells compatible with astrocytes. Cataract secondary to PHTVL/PHPV can be successfully treated using phacoemulsification and planned posterior capsulectomy. Posterior lens capsule duplication, mast cells and astrocytic glial cells may be normal components of the fibrovascular retrolental plaque associated with PHTVL/PHPV.

Ocular complications of persistent hyperplastic primary vitreous in three dogs

Persistent hyperplastic primary vitreous (PHPV) syndrome associated with either severe ocular complications or multiple ocular lesions was diagnosed in three young dogs, a Samoyed, a Spanish Pachon, and a mixed breed dog. Due to opacification of the anterior ocular structures, B-mode and color-flow Doppler ultrasonography were performed to aid diagnosis. The Samoyed presented with unilateral hyphema; the Spanish Pachon presented with unilateral secondary glaucoma associated with uveitis and hyphema OD and leucocoria OU; and the mixed breed presented with bilateral leucocoria. B-mode ultrasonography of the Samoyed revealed a subcapsular cataract and a hyperechoic tubular structure attached from the optic disk to the posterior lens capsule. In the Spanish Pachon B-mode ultrasonography of the right eye indicated microphakia, cataract formation, and a retrolental mass with a thin hyperechoic strand stretching from the optic disk to the posterior lens; and for the right eye cataract formation, PHPV, retinal detachment, and vitreous hemorrhage. In the mixed breed dog, B-mode ultrasonography of both eyes indicated microphthalmia, retrolental mass, and hyperechoic lenses. By color-flow Doppler imaging, blood flow was present in the retrolental mass of the right eye suggesting a persistent hyaloid artery.

Morphologic alterations in the anterior lens capsule of canine eyes with cataracts

OBJECTIVE

To examine the morphologic changes in the anterior lens capsule and lens epithelium of canine eyes with cataracts.

SAMPLE POPULATION

Anterior lens capsules from the eyes of 25 dogs with cataracts and from an additional 10 canine globes with lenses subjectively assessed to be normal.

PROCEDURE

Thickness of each anterior lens capsule was measured by use of a digital microscopic camera and imaging software. All 25 capsules from eyes with cataracts were submitted for light microscopy; 4 were also submitted for electron microscopy.

RESULTS

Thickness of the anterior lens capsule increased with age for the normal lenses and the lenses with cataracts; the change with age was similar for both groups. Light microscopy revealed fibrous metaplasia of lens epithelial cells in 7 of 25 anterior lens capsules with focal thickenings of the posterior aspect of the capsule. Electron microscopy revealed deposition of collagen and basement membrane-like material by fibroblast-like cells.

CONCLUSIONS

Results indicate that thickness of the anterior lens capsule in dogs increases with age and that this increase in thickness is not significantly different between normal lenses and lenses with cataracts. In addition, epithelial cells from lenses with cataracts may undergo metaplasia to form plaques composed of fibrous tissue and ectopic basement membrane produced by epithelial cells.

Persistent hyperplastic tunica vasculosa lentis and persistent hyperplastic primary vitreous in transgenic line TgN3261Rpw

Persistent hyperplastic tunica vasculosa lentis and persistent hyperplastic primary vitreous are congenital ocular anomalies that can lead to cataract formation. A line of insertional mutant mice, TgN3261Rpw, generated at the Oak Ridge National Laboratory in a large-scale insertional mutagenesis program was found to have a low incidence (8/243; 3.29%) of multiple developmental ocular abnormalities. The ocular abnormalities include persistent hyperplastic primary vitreous, persistent hyperplastic tunica vasculosa lentis, failure of cleavage of the anterior segment, retrolental fibrovascular membrane, posterior polar cataract, and detached retina. This transgenic mouse line provides an ontogenetic model because of the high degree of similarity of this entity in humans, dogs, and mice.

The human hyaloid system: cell death and vascular regression

The present study had investigated the roles of apoptosis and necrosis in the regression of the human fetal hyaloid vasculature. Normal human fetal hyaloid specimens (n = 67) ranging from 10 to 20 weeks' gestation were studied. Specimens were either immunolabeled with anti-von Willebrand factor and major histocompatibility complex class I antibodies or investigated using the terminal-deoxyribonucleotidyl transferase-mediated dUTP-biotin DNA nick-end labeling technique. A fluorescent DNA-binding dye acridine orange/ethidium bromide mixture was also applied to unfixed flat mounts of hyaloid vasculature and some specimens were processed for transmission electron microscopy. Vascular regression including cell loss in the connecting vessels, stretching and thinning of the vasa hyaloidea propria, tunica vasculosa lentis and the pupillary membrane was clearly evident after 13 weeks' gestation. Cresyl violet staining revealed condensed cells and pyknotic bodies throughout the hyaloid system; cell death occurred either in single cells or along small capillary segments associated with vascular regression. Acridine orange/ethidium bromide staining showed DNA condensation at early and late stages of cell death. Similarly, DNA nick-end labeling was positive in endothelial cells, pericytes and vessel and non-vessel associated hyalocytes. The observation of hyalocytes juxtaposed to cytolysed endothelial cells may indicate a role for these cells in vascular regression. Features of apoptosis were more evident during early vascular regression whilst necrosis was increasingly evident at later stages.

The human hyaloid system: cellular phenotypes and inter-relationships

We have investigated the expression of leucocyte markers, phenotypic characteristics and cellular relationships of the normal human fetal hyaloid vasculature using immunohistochemistry, light and electron microscopy. Antibodies against von Willebrand Factor, alpha-smooth muscle actin, glial fibrillary acidic protein, vimentin, major histocompatibility complex classes-I and -II, CD45 (leucocyte-common antigen) and calcitonin gene-related peptide were used to identify the cellular constituents of the hyaloid vasculature in whole mounts. Additional morphological features were described at the ultrastructural level. Endothelial cells throughout the hyaloid system were immunoreactive to von Willebrand Factor and major histocompatibility complex class-I antibodies. Pericytes were immunoreactive to alpha-smooth muscle actin antibody; labeled cells were distributed along large branches of the hyaloid artery, vasa hyaloidea propria, tunica vasculosa lentis and pupillary membrane but no immunoreactivity was detected on small connecting capillaries. Vessel and non-vessel-associated hyalocytes on the hyaloid artery, vasa hyaloidea propria, tunica vasculosa lentis, pupillary membrane and vitreous were immunoreactive to major histocompatibility complex classes-I and -II, CD45 and calcitonin gene-related peptide antibodies. Anti-glial fibrillary acidic protein reactivity was detected on Bergmeister's papilla but not on the hyaloid artery. Cells immunoreactive for vimentin were present throughout the hyaloid vasculature including small connecting capillaries. Ultrastructural observations of the hyaloid vasculature revealed junctional complexes, including zonulae adherens, macula adherens and possible zonulae occludens, between adjacent endothelial cells. Fenestrae were not observed in the gestational ages included in the present study. The use of whole mounts in conjunction with specific antisera has provided novel immunohistochemical definitions of the structure and cellular constituents of the human hyaloid. The results indicate that hyalocytes are a heterogeneous population of leucocyte-lineage cells.

Early morphogenesis of persistent hyperplastic tunica vasculosa lentis and primary vitreous (PHTVL/PHPV). Scanning electron microscopic observations

This study provides scanning electron microscopic observations on the early morphogenesis of persistent hyperplastic tunica vasculosa lentis and primary vitreous (PHTVL/PHPV) in canine fetuses at days 28 35 postcoitum (D28 and D35). From previous studies regarding PHTVL/PHPV it is known that a retrolental plaque of fibrovascular tissue is present in eyes of affected canine fetuses from the D33 stage. The contribution of vitreous cells to the formation of the plaque is supported by the results of this study. The lens capsules at the stages described were not found to contain abnormalities such as transparent (thinner) parts or rents, as have been described for postnatal cases of PHTVL/PHPV. These findings support the hypothesis that the capsular anomalies observed in postnatal patients are secondary entities.