Microwave treatment of the cornea leads to localised disruption of the extracellular matrix

Ultrastructural Aspects of Corneal Functional Recovery in Rats Following Intrastromal Keratocyte Injection

Purpose

Donor tissue shortfalls and postsurgical complications are driving novel corneal tissue regeneration approaches. Corneal stromal keratocytes (CSKs) have shown promise in promoting corneal repair and restoring transparency. We investigated the impact of intrastromal CSK injection on corneal ultrastructure and proteoglycan (PG) distribution in a rat injury model.

Methods

Rats were divided into four groups: normal (n = 12), injured (irregular phototherapeutic keratectomy centrally; n = 6), CSK (injured + human CSK intrastromal injection; n = 6), and PBS (injured + PBS injection; n = 6). Three weeks after treatment, corneas were examined by slit-lamp and optical coherence tomography. Corneal ultrastructure was analysed via small-angle x-ray scattering (collagen fibril diameter, interfibrillar spacing and matrix order), transmission electron microscopy with cuprolinic blue before and after chondroitinase digestion (CS/DS and KS PGs), and immunofluorescence staining (lumican and decorin).

Results

Irregular phototherapeutic keratectomy caused corneal opacity and significantly disrupted stromal ultrastructure, characterized by increased haze density (P < 0.0001), change in central corneal thickness (P = 0.0005), and interfibrillar spacing (P < 0.0001), along with decreased fibril diameter (P < 0.0001), matrix order (P < 0.0001), CS/DS (P < 0.0001) and KS (P < 0.0001) PGs, lumican, and decorin. CSK injection recovered corneal clarity and native stromal ultrastructure, with haze density (P = 0.8086), change in central corneal thickness (P = 0.9503), fibril diameter (P = 0.1139), interfibrillar spacing (P = 0.5879), matrix order (P = 0.9999), CS/DS (P = 0.9969) and KS (P = 0.2877) PGs, lumican, and decorin returning to normal. In contrast, the PBS group exhibited similar corneal injury responses to the injured group.

Conclusions

CSK injection resolved early stage corneal scarring by restoring stromal collagen arrangement and PG distribution, further endorsing its potential for treating corneal opacities.

Keratometry and ultrastructural changes after microwave thermokeratoplasty in rabbit eyes

PURPOSE

To conduct keratometry and investigate the ultrastructural changes after microwave thermokeratoplasty (MTK) in rabbit eyes.

METHODS

Eighteen New Zealand rabbits (18 eyes) were recruited for this study. Ten eyes were chosen for slit-lamp photography and corneal topography at 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively. Two rabbits were sacrificed on 1 day, 1 week, 1 month, and 3 months postoperatively. All remaining rabbits were sacrificed at 6 months postoperatively. The cornea was observed using hematoxylin and eosin staining and transmission electron microscopy. Data are expressed as mean ± standard deviation. p value was determined using repeated-measures analysis of variance.

RESULTS

Corneal edema, disorganized corneal collagen fibers in the heated area, and necrotic fibroblasts were observed at 1 day and 1 week postoperatively. At 1 month postoperatively, corneal edema was not observed, and corneal cell morphology was normal. Moreover, corneal collagen fibers in the heated area shrunk and tended to be organized. The K1 and K2 values significantly decreased from 49.0 ± 1.2 D and 50.5 ± 0.9 D preoperatively to 40.3 ± 1.2 D and 43.2 ± 0.8 D 6 months postoperatively, respectively. The corneal thickness was 353.1 ± 9.3 µm preoperatively and 317.8 ± 27.7 µm at 6 months postoperatively; the difference was not statistically significant.

CONCLUSIONS

Corneal keratometry showed flattening after MTK. Moreover, corneal collagen fibers in the heated area shrunk and tended to be organized at 6 months postoperatively. Further studies are required to determine the safety and stability of MTK.

I22: SAXS/WAXS beamline at Diamond Light Source - an overview of 10 years operation

Beamline I22 at Diamond Light Source is dedicated to the study of soft-matter systems from both biological and materials science. The beamline can operate in the range 3.7 keV to 22 keV for transmission SAXS and 14 keV to 20 keV for microfocus SAXS with beam sizes of 240 µm × 60 µm [full width half-maximum (FWHM) horizontal (H) × vertical (V)] at the sample for the main beamline, and approximately 10 µm × 10 µm for the dedicated microfocusing platform. There is a versatile sample platform for accommodating a range of facilities and user-developed sample environments. The high brilliance of the insertion device source on I22 allows structural investigation of materials under extreme environments (for example, fluid flow at high pressures and temperatures). I22 provides reliable access to millisecond data acquisition timescales, essential to understanding kinetic processes such as protein folding or structural evolution in polymers and colloids.

Safety profiles of terahertz scanning in ophthalmology

Terahertz (THz) technology has emerged recently as a potential novel imaging modality in biomedical fields, including ophthalmology. However, the ocular biological responses after THz electromagnetic exposure have not been investigated. We conducted a rabbit study to evaluate the safety profiles of THz scanning on eyes, at a tissue, cellular, structural and functional level. Eight animals (16 eyes) were analysed after excessive THz exposure (control, 1 h, 4 h, and 1 week after continuous 4-h exposure; THz frequency = 0.3 THz with continuous pulse generated at 40 µW). We found that at all the time points, the corneas and lens remained clear with no corneal haze or lens opacity formation clinically and histopathologically. No thermal effect, assessed by thermographer, was observed. The rod and cone cell-mediated electroretinography responses were not significantly altered, and the corneal keratocytes activity as well as endothelial viability, assessed by in-vivo confocal microscopy, was not affected. Post-exposed corneas, lens and retinas exhibited no significant changes in the mRNA expression of heat shock protein (HSP)90AB1), DNA damage inducible transcript 3 (DDIT3), and early growth response (EGR)1. These tissues were also negative for the inflammatory (CD11b), fibrotic (fibronectin and α-smooth muscle actin), stress (HSP-47) and apoptotic (TUNEL assay) responses on the immunohistochemical analyses. The optical transmittance of corneas did not change significantly, and the inter-fibrillar distances of the corneal stroma evaluated with transmission electron microscopy were not significantly altered after THz exposure. These results provide the basis for future research work on the development of THz imaging system for its application in ophthalmology.