Immunostaining of a heterodimeric dermatan sulphate proteoglycan is correlated with smooth muscles and some basement membranes

Ex vivo demonstration of canine corneal pre-Descemet's anatomy using pneumodissection as for the big bubble technique for deep anterior lamellar keratoplasty

The recent discovery and characterization of pre-Descemet's layer (PDL; also termed the Dua's layer or the Dua-Fine layer) has advanced the understanding of various posterior corneal pathologies and surgeries in human. This study aimed to characterize the ultrastructure of the posterior stroma and interfacial zone of Descemet's membrane (DM) in canine eyes. Eighteen canine corneo-scleral discs were included. Intrastromal air injection resulted in the formation of type 1 big bubble (BB) in 73% (n = 11/15) of corneas, with a mean diameter of 11.0 ± 1.3 mm. No type 2 BB was created. Anterior segment optical coherence tomography, histology and transmission electron microscopy confirmed that the wall of BB was composed of DM, in contact with remaining stroma (canine PDL; cPDL). The cPDL was populated with keratocytes, of varying thickness of 16.2 ± 4.2 µm in close apposition to the DM, and composed of collagen bundles arranged in transverse, longitudinal and oblique directions. The interfacial zone, between DM and cPDL, showed fibril extension in all three directions, predominantly longitudinal. Irregular extensions of DM material into cPDL stroma were observed. No long-spaced collagen was detected. In conclusion, there exists a well-defined cleavage plane between the posterior stroma and cPDL, with similar but not identical characteristics as in humans, that is revealed by pneumodissection. This adds to our understanding of the anatomy of the posterior most canine cornea, which will have significant clinical impact on posterior corneal surgery and understanding of corneal pathology in dogs.

Neonatal steroids induce a down-regulation of tenascin-C and elastin and cause a deceleration of the first phase and an acceleration of the second phase of lung alveolarization

Pre- and postnatal corticosteroids are often used in perinatal medicine to improve pulmonary function in preterm infants. To mimic this clinical situation, newborn rats were treated systemically with dexamethasone (Dex), 0.1-0.01 mg/kg/day on days P1-P4. We hypothesized that postnatal Dex may have an impact on alveolarization by interfering with extracellular matrix proteins and cellular differentiation. Morphological alterations were observed on 3D images obtained by high-resolution synchrotron radiation X-ray tomographic microscopy. Alveolarization was quantified stereologically by estimating the formation of new septa between days P4 and P60. The parenchymal expression of tenascin-C (TNC), smooth muscle actin (SMA), and elastin was measured by immunofluorescence and gene expression for TNC by qRT-PCR. After Dex treatment, the first phase of alveolarization was significantly delayed between days P6 and P10, whereas the second phase was accelerated. Elastin and SMA expressions were delayed by Dex treatment, whereas TNC expression was delayed and prolonged. A short course of neonatal steroids impairs the first phase of alveolarization, most likely by altering the TNC and elastin expression. Due to an overshooting catch-up during the second phase of alveolarization, the differences disappear when the animals reach adulthood.

Canine Duplication of Descemet's Membrane

The morphology of a duplication phenomenon of the canine Descemet's membrane (DM) is described in relation to signalment, history, and ocular disease status. Sixty-six canine eyes from the Comparative Ocular Pathology Laboratory of Wisconsin archives between 2000 and 2007 were examined. All cases were stained with hematoxylin and eosin and Alcian blue periodic acid-Schiff (PAS), while 14 cases were additionally stained with Masson's trichrome, picrosirius red, cytokeratin AE1/AE3 (CK), vimentin, and α-smooth muscle actin (SMA). Transmission electron microscopy (TEM) examination was performed in 3 corneas and in 1 normal control eye. Alcian blue PAS staining and TEM confirmed the basement membrane nature of the abnormal secondary DM. The thickness of the first DM, referred to as the corneal layer (CL) and the second or anterior chamber layer (ACL), were nearly the same, with no significant difference seen ( P = .93). In 39% (26/66) of the eyes, a fibrous, collagenous matrix component was present between the CL and ACL, which contains vimentin-positive and α-SMA-negative spindle cells (14/14).The corneal endothelial cells in 7/14 eyes stained weakly with CK and strongly in 2 additional eyes. The most frequent histopathologically confirmed, clinical ocular histories were chronic glaucoma in 76% (50/66) of eyes, previous intraocular surgery in 36% (24/66), lens luxation in 21% (4/66), and blunt trauma in 15% (10/66) of the cases. We speculate that activation and migration of endothelial cells, in association with trauma or lens contact, play a role in the pathogenesis of this phenomenon.

The effect of hyaluronic acid size and concentration on branching morphogenesis and tubule differentiation in developing kidney culture systems: potential applications to engineering of renal tissues

Hyaluronic acid (HA) is a glycosaminoglycan of tissue engineering importance that plays a vital role in mammalian development. In vitro kidney culture methods were utilized to investigate the importance of HA during renal organogenesis. We found that HA has the ability to simultaneously modulate ureteric bud (UB) branching, promote mesenchymal-to-epithelial transformation, and promote differentiation of both metanephric mesenchyme (MM) and the UB depending on the concentration and molecular weight (MW) of HA. Hyaluronidase inhibited branching morphogenesis in both isolated UB and whole kidney cultures, suggesting endogenous HA is required for branching morphogenesis. HA exhibited morphogen-like properties, stimulating branching morphogenesis at low concentrations (0.1%) and low MW (6.55 kDa), but inhibiting at high concentrations (3.75%) and high MW (234.4 kDa). Furthermore, HA of every MW tested promoted collecting duct differentiation as measured by AQP-2 expression. E-cadherin immunostaining and qPCR of nephron differentiation markers (OAT-1, NaP(i)-2, AQP-1, and THP) demonstrated that HA of a variety of MWs strongly promotes mesenchymal epithelialization and nephron differentiation in a concentration-dependent manner. Since the HA synthesis and degradation genes, has-2 and hyal-2, are highly expressed during kidney development, this data suggests that specific sizes and concentrations of HA may act to independently regulate UB branching and promote tubular maturation, representing a potential switch for ending branching morphogenesis, as well as initiating nephron differentiation. In addition, the ability of HA to promote in vitro embryonic kidney growth and maturation, together with the biocompatibility and crosslinking capability of HA, suggests a potential use of HA for both creating an instructive, 3D scaffold for in vitro kidney engineering from developmental tissues, as well as promoting tubule regeneration in injured or cryopreserved kidneys.

Aging changes of mouse corneal endothelium and Descemet's membrane

The purpose of this study was to characterize age-associated changes in the corneal endothelium and Descemet's membrane (DM) in C57BL/6 mice, an inbred strain commonly used as a genetic disease model. Corneas from mice aged 2 weeks to 24 months were studied. Light microscopy was used to assess central endothelial cell density, area, and morphology. Transmission electron microscopy was used to assess thickness and ultrastructural features of DM. Central corneal endothelial cell density showed a rapid decline from 5,232+/-892 cells/mm(2) (mean+/-S.D.) at 2 weeks to 2,532+/-112 cells/mm(2) at 16 weeks of age. Thereafter, cell density declined more slowly, reaching 2,004+/-134 cells/mm(2) at 24 months of age. DM thickness showed an approximately linear increase from 1.12+/-0.22 microm (mean+/-S.D.) at 2 weeks to 4.19+/-1.17 microm at 24 months of age. DM in 2 and 6 week age groups was composed entirely of material with an electron dense, periodic banding pattern. Sixteen week, 12 month, and 24 month age groups exhibited an additional, progressively thicker, homogeneous layer lacking periodic banding. The observed age-dependent thickening of DM was predominantly due to accumulation of the posterior, non-banded layer. In C57BL/6 mice, central endothelial cell density declines with age and DM progressively thickens due to accumulation of a posterior, non-banded portion. These age-associated changes are strikingly similar to observations in humans and thus further support the potential usefulness of the mouse model for studying disorders of the corneal endothelium and Descemet's membrane.

Regional and zonal variations in the sulfation patterns of chondroitin sulfate in normal equine corneal stroma

OBJECTIVE

To determine regional and zonal variation in sulfation patterns of chondroitin sulfate in normal equine corneal stroma.

SAMPLE POPULATION

22 normal eyes from 11 horses.

PROCEDURE

Corneas were collected within 24 hours of death from equine necropsy specimens. After papain-chondroitinase digestion of corneal tissue, disaccharides deltaDi4S and deltaDi6S were quantified by use of capillary zone electrophoresis in the superficial, middle, and deep zones of central and peripheral regions of the cornea.

RESULTS

For the 2 regions combined, deltaDi6S/deltaDi4S values were significantly lower in the deep and middle zones, compared with that of the superficial zone. In the central region, deep and middle zones had significantly lower deltaDi6S/deltaDi4S values than the superficial zone did. In the peripheral region, the deep zone had significantly lower deltaDi6S/deltaDi4S values, compared with superficial and middle zones. In the deep zone, the peripheral region had significantly lower deltaDi6S/deltaDi4S values than the central region did.

CONCLUSIONS AND CLINICAL RELEVANCE

Distribution of deltaDi6S/deltaDi4S values follows a gradient across the healthy equine cornea, being smallest in the deep and middle zones of the central region and the deep zone of the peripheral region. Regional and zonal differences in the distribution of stromal deltaDi6S and deltaDi4S may influence the role of glycosaminoglycans in health, disease, and wound repair of the equine cornea.

Molecular characterization of a novel basement membrane-associated proteoglycan, leprecan

A monoclonal antibody was used in early studies to identify a novel chondroitin sulfate proteoglycan, secreted by L-2 cells, the core protein of which was approximately 100 kDa. To characterize this proteoglycan core protein at the molecular level, an L-2 cell cDNA library was probed by expression screening and solution hybridization. Northern blot analysis assigned transcript size to approximately 3.1 kilobases and, after contig assembly, the coding region of the mRNA corresponded to 2.18 kilobases. Immunoassays were performed to confirm the identity of this sequence, using a polyclonal antibody raised against an expressed fusion protein encoded by sequence representing the carboxyl half of the molecule. The antibody recognized the core protein in Western blots after prior digestion of the intact proteoglycan with chondroitinase ABC. Immunostaining tissue sections with the same antibody localized the proteoglycan to basement membranes, and expression of the entire sequence in Chinese hamster ovary K-1 cells showed that the protein encoded by the sequence secreted as a chondroitin sulfate proteoglycan. The core protein not only has motifs permitting glycosylation as a proteoglycan, but also possesses the endoplasmic reticulum retrieval signal, KDEL, which suggests that, in addition to its role as a basement membrane component, it may also participate in the secretory pathway of cells.

Corneal cell proteins and ocular surface pathology

The cornea is a transparent and avascular tissue that functions as the major refractive structure for the eye. A wide variety of growth factors, chemokines, cytokines and their receptors are synthesized by corneal epithelial and stromal cells, and are found in tears. These molecules function in corneal wound healing and in inflammatory responses. Proteoglycans and glycoproteins are essential for normal corneal function, both at the air-epithelial interface and within the extracellular matrix. The ocular MUC mucins may play roles in forming the mucus layer of the tear film, in regulating tear film spread, and in inhibiting the adhesion of pathogens to the ocular surface. Lumican, keratocan and mimecan are the major keratan sulfate proteoglycans of the corneal stroma. They are essential, along with other proteoglycans and interfibrillar proteins, including collagens type VI and XII, for the maintenance of corneal transparency. Corneal epithelial cells interact with a specialized extracellular matrix structure, the basement membrane, composed of a specific subset of collagen type IV and laminin isoforms in addition to ubiquitous extracellular matrix molecules. Matrix metalloprotein-ases have been identified in normal corneal tissue and cells and may play a role in the development of ulcerative corneal diseases. Changes in extracellular matrix molecule localization and synthesis have been noted in other types of corneal diseases as well, including bullous keratopathy and keratoconus.