Stromal matrix directs corneal fibroblasts to re-express keratocan after injury and transplantation.

Every tissue has an extracellular matrix (ECM) with certain properties unique to it - the tissue 'niche' - that are necessary for normal function. A distinct specific population of quiescent keratocan-expressing keratocytes populate the corneal stroma during homeostasis to maintain corneal function. However, during wound healing, when there is alteration of the niche conditions, keratocytes undergo apoptosis, and activated corneal fibroblasts and myofibroblasts attempt to restore tissue integrity and function. It is unknown what the fate of activated and temporary fibroblasts and myofibroblasts is after the wound healing process has resolved. In this study, we used several strategies to elucidate the cellular dynamics of corneal wound healing and the fate of corneal fibroblasts. We injured the cornea of a novel mouse model that allows cell-lineage tracing, and we transplanted a cell suspension of in vitro-expanded corneal fibroblasts that could be tracked after being relocated into normal stroma. These transplanted fibroblasts regained expression of keratocan in vivo when relocated to a normal stromal niche. These findings suggest that transformed fibroblasts maintain plasticity and can be induced to a keratocyte phenotype once relocated to an ECM with normal signaling ECM.

Ocular Paraneoplastic Syndromes: A Critical Review of Diffuse Uveal Melanocytic Proliferation and Autoimmune Retinopathy.

Background: Dozens of paraneoplastic syndromes affect the visual system ranging from conjunctival pemphigoid to encephalopathy of the occipital cortex. The most profiled ocular syndromes are bilateral diffuse uveal melanocytic proliferation (BDUMP) and the autoimmune retinopathies.Purpose: To review the critical features of these 2 entities then concentrate on advancements in treatment made within the last 10 years.Study Design: Literature review with structured data abstraction.Results: Major insights into pathogenesis have been wanting. Plasmapheresis appears to improve vision in a substantial proportion of patients with BDUMP. The number of clinical variables that influence visual outcome in paraneoplastic retinopathies combined with the variety of local and systemic treatment options makes interpretation of clinical effectiveness difficult.Conclusions: The rarity of these disorders makes randomized clinical trials unlikely. It may be time for a clinical professional organization to use a modified Delphi method to establish a consensus algorithm for the diagnosis and management of retinal paraneoplastic syndromes to augment clinical communications and clinical trials.

Collagen XIV Is an Intrinsic Regulator of Corneal Stromal Structure and Function.

Collagen XIV is poorly characterized in the body, and the current knowledge of its function in the cornea is limited. The aim of the current study was to elucidate the role(s) of collagen XIV in regulating corneal stromal structure and function. Analysis of collagen XIV expression, temporal and spatial, was performed at different postnatal days (Ps) in wild-type C57BL/6 mouse corneal stromas and after injury. Conventional collagen XIV null mice were used to inquire the roles that collagen XIV plays in fibrillogenesis, fibril packing, and tissue mechanics. Fibril assembly and packing as well as stromal organization were evaluated using transmission electron microscopy and second harmonic generation microscopy. Atomic force microscopy was used to assess stromal stiffness. Col14a1 mRNA expression was present at P4 to P10 and decreased at P30. No immunoreactivity was noted at P150. Abnormal collagen fibril assembly with a shift toward larger-diameter fibrils and increased interfibrillar spacing in the absence of collagen XIV was found. Second harmonic generation microscopy showed impaired fibrillogenesis in the collagen XIV null stroma. Mechanical testing suggested that collagen XIV confers stiffness to stromal tissue. Expression of collagen XIV is up-regulated following injury. This study indicates that collagen XIV plays a regulatory role in corneal development and in the function of the adult cornea. The expression of collagen XIV is recapitulated during wound healing.

Collagen XII Is a Regulator of Corneal Stroma Structure and Function.

Purpose: The aim of this study was to determine the roles of collagen XII in the regulation of stromal hierarchical organization, keratocyte organization, and corneal mechanics. Methods: The temporal and spatial expression of collagen XII at postnatal days 4, 10, 30, 90, and 150 were evaluated in wild-type (WT) mice. The role of collagen XII in hierarchical organization was analyzed by measuring fibril diameter and density, as well as stromal lamellar structure, within ultrastructural micrographs obtained from WT and collagen XII-deficient mice (Col12a1-/-). Keratocyte morphology and networks were assessed using actin staining with phalloidin and in vivo confocal microscopy. The effects of collagen XII on corneal biomechanics were evaluated with atomic force microscopy. Results: Collagen XII was localized homogeneously in the stroma from postnatal day 4 to day 150, and protein accumulation was shown to increase during this period using semiquantitative immunoblots. Higher fibril density (P < 0.001) and disruption of lamellar organization were found in the collagen XII null mice stroma when compared to WT mice. Keratocyte networks and organization were altered in the absence of collagen XII, as demonstrated using fluorescent microscopy after phalloidin staining and in vivo confocal microscopy. Corneal stiffness was increased in the absence of collagen XII. Young's modulus was 16.2 ± 5.6 kPa in WT and 32.8 ± 6.4 kPa in Col12a1-/- corneas. The difference between these two groups was significant (P < 0.001, t-test). Conclusions: Collagen XII plays a major role in establishing and maintaining stromal structure and function. In the absence of collagen XII, the corneal stroma showed significant abnormalities, including decreased interfibrillar space, disrupted lamellar organization, abnormal keratocyte organization, and increased corneal stiffness.