Cellular toxicity profile of a new ophthalmic sponge

Introduction: Ophthalmic sponges are used for cleaning the eye surface and absorbing fluids during ophthalmic procedures. This study compared the biological safety and stability of a new ophthalmic sponge, Occucell® (OccuTech Inc, Seongnam, Korea), on the human conjunctival epithelial cells with those of preexisting products to evaluate its clinical application.Materials and Methods: The cytotoxicity of four products, Occucell, a new product, Ultracell®, Eyetec-1, and Eyetec-2, on conjunctival epithelial cells, was evaluated using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) analysis. Additionally, human conjunctival epithelial cells were stained with a Live & Dead marker and observed using a fluorescence microscope. To evaluate the effect of the ophthalmic sponges on the secretion of IL-1β and TNF-α, cultured conjunctival epithelial cells were treated with 0.5% DMSO eluates of the ophthalmic sponges, and IL-1β and TNF-α mRNA levels were estimated using real-time polymerase chain reaction assays.Results: Cells treated with Occucell showed comparable viability to those treated with other preexisting products. Conjunctival epithelial cells showed more than 90% viability when treated with the ophthalmic sponge extracts, as determined by the MTT assay. No significant differences in the number of live & dead cells were observed between the control and treatment groups. Cells treated with all four ophthalmic sponge eluates showed similar IL-1β and TNF-α mRNA levels.Discussion: Occucell, an eye sponge used during ophthalmic surgery in clinical practice, did not affect the viability of conjunctival epithelial cells, and more than 90% of the cells were viable after the treatment. Further, Occucell showed similar effects on IL-1β and TNF-α secretion as that of other ophthalmic sponges used in the clinic. This suggested that Occucell is a safe product comparable to the preexisting products.

Effect of tear fluid sampling and processing on total protein quantity and electrophoretic pattern

Human tears contain more than 1500 proteins that could be diagnostically relevant. To date, numerous candidates on a biomarker of protein origin were identified for ocular and systemic diseases. However, the suitable sampling method is still the subject of discussion. To address the need for a description of sampling methods properties for possible clinical analyses, we studied a total protein concentration and electrophoretic pattern of tear fluid collected by capillary tubes, Schirmer strips, cellulose microsponges, and flushing. The total protein concentration was 4.339 μg/μL ± 1.905 μg/μL, 0.967 μg/μL ± 0.117 μg/μL, 0.022 μg/μL ± 0.016 μg/μL, and 0.008 μg/μL ± 0.006 μg/μ for the capillary tubes, Schirmer strips, flushing, and cellulose microsponges, respectively. Sodium dodecyl sulfate polyacrylamide electrophoresis showed the different patterns of tear proteins obtained by the above-mentioned sampling methods. These differences could originate from the use of a bigger amount of extraction reagent that was not used in the case of capillary tubes, and retention of the proteins by strips and sponges. Taken together, capillary tubes, Schirmer strips, cellulose microsponges, and flushing represent sensitive and convenient sampling methods for tear fluid collection. For the isolation of proteins from strips and sponges, and for the flushing, less than 100 μL of a reagent should be used to ensure the sufficient concentration of the biomarkers in a trace amount.

Tear fluid biomarkers in major depressive disorder: Potential of spectral methods in biomarker discovery

Spectroscopic methods represent a group of analytical methods that demonstrate high potential in providing clinically relevant diagnostic information, such as biochemical, functional or structural changes of macromolecular complexes that might occur due to pathological processes or therapeutic intervention. Although application of these methods in the field of psychiatric research is still relatively recent, the preliminary results show that they have the capacity to detect subtle neurobiological abnormalities in major depressive disorder (MDD). Methods of mass spectrometry (MALDI-TOF MS), zymography, synchronous fluorescence spectroscopy (SFS), circular dichroism (CD) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) were used to analyze the human tear fluid of subjects with MDD. Using MALDI-TOF MS, two diagnostically significant peaks (3747 and 16 411 m/z) were identified with an AUC value of 0.89 and 0.92 in tear fluid of subjects with MDD vs controls, respectively. We also identified various forms of matrix metalloproteinase 9 in subjects with MDD using zymography and synchronous fluorescence spectra (SFS) showed a significant increase in fluorescence intensity at 280 nm. CD spectra were redshifted in tear fluid of subjects with MDD vs healthy controls. FTIR spectroscopy showed changes in the positions of peaks for amide A, I, II in tear fluid of subjects with MDD vs controls. Moreover, atomic force microscopy (AFM) showed different pattern in the crystal structures of tear fluid components in subjects with MDD. SFS, CD, FTIR spectroscopy, AFM and MALDI-TOF MS confirmed, that the human tear fluid proteome could be helpful in discriminating between the group of subjects with MDD and healthy controls. These preliminary findings suggest that spectral methods could represent a useful tool in clinical psychiatry, especially in establishing differential diagnosis, monitoring illness progression and the effect of psychiatric treatment.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).

Aquaporin 1 (AQP1) Expression in Healthy Dog Tears

Simple Summary

The characterisation of tear proteins is very important for scientists and clinicians, as it enhances their understanding of ocular physiological phenomena that sometimes evolve into diseases. Recently, ophthalmic research has been focused on aquaporins (AQPs), a family of water channel proteins that are largely ubiquitous in body tissues and are known for their role in water and small solute transport across cell membranes. Based on AQPs’ presumable role in the eye, the aim of the present study was to investigate the expression of aquaporin-1 (AQP1) by Western blot analysis in canine eye tears. To this end, we collected tears from both eyes of 15 healthy dogs by employing two tear collection methods: Schirmer tear strips (STS) and ophthalmic sponges (OS). Moreover, ocular parameters such as Schirmer tear test 1 (STT 1), intraocular pressure (IOP), and tear film break up time (BUT) were measured, and fluorescein and lissamine green staining were performed to uncover possible correlations among the aforementioned parameters. Our results showed that the expression of AQP1 in tears collected by both methods and expressed as multiple bands (measured by densitometry) was higher for the tears collected by OS than for those collected by STS. This work forms the basis of future studies aiming to understand and establish the involvement of AQPs in the production and secretion of tears.

Abstract

Aquaporins (AQPs) are a family of thirteen membrane proteins that play an essential role in the transport of fluids across the cell plasma membrane. Recently, the expression of AQPs in different ocular tissues and their involvement in the pathophysiology of eye diseases, have garnered attention. Considering that literature on AQP expression in the lacrimal glands and their secretion is scarce, we aimed to characterise AQP1 expression in the tears of healthy dogs using two tear collection methods (Schirmer tear strips (STS) and ophthalmic sponges (OS)). Fifteen healthy dogs, free of ophthalmic diseases, were included in the study. Tear collection was performed by using STS in one eye and OS in the other. After the extraction of proteins from the tears, the expression of AQP1 was analysed by Western blotting. AQP1 was expressed as a band of 28 kDa. In addition, differences were observed in the expression of AQP1 and in the correlation between tear volume and protein concentration, in tears collected by the two different methods. Our results suggest that AQP1 has a specific role in tear secretion; further research is required to assess its particular role in the function of the ocular surface in eye physiology and pathology.