Marina Koulikovska

Composite core-and-skirt collagen hydrogels with differential degradation for corneal therapeutic applications

UNLABELLED Scarcity of donor tissue to treat corneal blindness and the need to deliver stem cells or pharmacologic agents to ensure corneal graft survival are major challenges. Here, new composite collagen-based hydrogels are developed as implants to restore corneal transparency while serving as a possible reservoir for cells and drugs. The composite hydrogels have a centrally transparent core and embedded peripheral skirt of adjustable transparency and degradability, with the skirt exhibiting faster degradation in vitro. Both core and skirt supported human epithelial cell populations in vitro and the skirt merged homogeneously with the core material to smoothly distribute a mechanical load in vitro. After in vivo transplantation in rabbit corneas over three months, composites maintained overall corneal shape and integrity, while skirt degradation could be tracked in vivo and non-invasively due to partial opacity. Skirt degradation was associated with partial collagen breakdown, thinning, and migration of host stromal cells and macrophages, while the central core maintained integrity and transparency as host cells migrated and nerves regenerated. IMPACT This study indicates the feasibility of a collagen-based composite hydrogel to maintain corneal stability and transparency while providing a degradable peripheral reservoir for cell or substance release.

An accurate method to determine Bowman's layer thickness in vivo in the human cornea.

PURPOSE To determine an accurate value for Bowmans layer (BL) thickness in vivo in humans. METHODS Seventeen corneal transplant patients were examined preoperatively by laser-scanning in vivo confocal microscopy (IVCM), and corneal buttons were removed postoperatively and sectioned for light microscopy (LM). Nine corneas with uniformly thick BL by LM were used for thickness measurement. In the uniformly thick samples, probable overestimation of BL thickness in vivo by a first in vivo method (Method 1) led to the development of a revised in vivo method (Method 2). Method 2 was used to measure BL thickness in 20 healthy volunteers. RESULTS In nine patients, mean BL thickness prior to transplantation was 13.7 ± 1.6 μm by IVCM (Method 1) while BL thickness of the removed corneal button was 9.7 ± 1.7 μm by LM (P < 0.001). The correlation of BL thickness between IVCM (Method 1) and LM was poor (P = 0.226). In 20 right eyes of 20 normal corneas, both in vivo methods were used to determine BL thickness. Mean BL thickness by Method 1 was 13.2 ± 1.6 μm and by Method 2 was 9.1 ± 1.4 μm (P < 0.001). BL thickness measurements by both in vivo methods were highly correlated (P < 0.001). CONCLUSION BL thickness by a revised in vivo method was close to LM values in this study and to values reported in fixed tissue in other studies. The authors believe this revised method provides the most accurate estimates of BL thickness in vivo to date.

Respiratory syncytial virus and chlamydia are not detectable by PCR in ongoing vernal keratoconjunctivitis

Respiratory syncytial virus (RSV) and chlamydial infection may be pathogenetic factors in allergic diseases, perhaps also in ocular allergy. We analyzed the presence of RSV and chlamydial nucleic acids using reverse transcription (RT)-PCR and PCR, respectively, in conjunctival biopsies from patients with vernal keratoconjunctivitis (VKC) in order to determine whether these agents play a role in the maintenance of the disease. All biopsy samples were negative for both RSV (n = 15 for VKC and n = 10 for control subjects) and chlamydia (n = 8 for VKC and n = 7 for control subjects) homologous sequences. A direct association between RSV or chlamydial infection and ongoing inflammation in VKC could, therefore, not be confirmed.

Platelet-Rich Plasma Prolongs Myofibroblast Accumulation in Corneal Stroma with Incisional Wound

Abstract Purpose: The purpose of this study was to determine whether platelet-rich plasma (PRP) has an effect on corneal stromal cells in a rat model of wound healing following corneal incision. Materials and Methods: The effect of PRP on corneal wound healing in vivo was investigated in a corneal incision wound model in rats. 40 rats were wounded by deep corneal incision, and treated with either topically administered PRP (20 rats) or sodium chloride (20 rats). At 4 h and 1, 3, and 5 days after incision, α-smooth muscle actin (α SMA), SMAD2 and SMAD3 expression and apoptosis in stromal cells were evaluated by immunohistochemistry, and IL-1β mRNA expression was evaluated by real time PCR. Results: PRP-treated corneas exhibited reduced stromal cell apoptosis at day 3 and day 5 (p = 0.038, and <0.001, respectively) relative to controls. Interleukin-1β mRNA expression, however, was unchanged in PRP-treated corneas relative to controls. Topical PRP treatment resulted in a higher proportion of αSMA-positive myofibroblasts recruited to the wound site relative to control corneas. PRP did not affect activation of SMAD2 but activation of SMAD3 was significantly reduced at day 1 (p = 0.001) and dramatically increased at day 5 (p = 0.032). Conclusions: PRP treatment resulted in suppressed stromal cell apoptosis followed by SMAD3 activation and a greater proportion of myofibroblasts present at the wound site. Suppression of stromal cell apoptosis after corneal wounding by use of a growth factor-rich formulation may lead to myofibroblast accumulation by modulation of the TGF-β pathway.

The suppression of early angiogenic markers by the antiangiogenic aptamer Macugen® is dose dependent

The suppression of early angiogenic markers by the antiangiogenic aptamer Macugen R is dose dependent