Assessment of size and nucleo-cytoplasmic characteristics of the squamous cells of the corneal epithelium

Ozone exposure affects corneal epithelial fate by promoting mtDNA leakage and cGAS/STING activation

Ozone is a common air pollutant associated with various human diseases. The human ocular surface is frequently exposed to ozone in the troposphere, but the mechanisms by which ozone affects the ocular surface health remain unclear. This study aimed to establish a mouse model to investigate the effects of ozone exposure on the ocular surface and the corneal epithelium. The findings revealed that ozone exposure disrupted corneal epithelial homeostasis and differentiation, resulting in corneal squamous metaplasia. Further, ozone exposure induced oxidative damage and cytoplasmic leakage of mitochondrial DNA (mtDNA), thereby activating the cGAS/STING signaling pathway. The activation of the cGAS/STING signaling pathway triggered the activation of downstream NF-κB and TRAF6 signaling pathways, causing corneal inflammation, thereby promoting corneal inflammation and squamous metaplasia. Finally, C-176, a selective STING inhibitor, effectively prevented and treated corneal inflammation and squamous metaplasia caused by ozone exposure. This study revealed the role of mtDNA leakage-mediated cGAS/STING activation in corneal squamous epithelial metaplasia caused by ozone exposure. It also depicted the abnormal expression pattern of corneal epithelial keratin using three-dimensional images, providing new targets and strategies for preventing and treating corneal squamous metaplasia and other ocular surface diseases.

Evaluation of the Cytonucleomorphometric Parameters for Cases Diagnosed as Squamous Cell Abnormality on Conventional Cervico-Vaginal Pap Smears

Background and Aim

The natural history of cervical cancer is unique that it is preceded by a precancerous condition for a long time. Morphometry as a tool can be used in early and accurate diagnosis of these precancerous and cancerous lesions. The present study aims at assessing the utility of cellular and nuclear morphometry in differentiating squamous cell abnormality from benign conditions and also differentiating the categories of squamous cell abnormalities.

Materials and Methods

Forty-eight diagnosed cases of squamous epithelial cell abnormality, that is, 10 cases each of atypical squamous cell of undetermined significance (ASC-US), low-grade squamous intraepithelial lesion (LSIL), high-grade SIL (HSIL), and squamous cell carcinoma (SCC) and eight cases of ASC-H (ASC cannot exclude HSIL), were made the sample population and compared with a control population of 10 cases of negative for intraepithelial lesion or malignancy (NILM). Parameters like nuclear area (NA), nuclear perimeter (NP), nuclear diameter (ND), nuclear compactness (NC), cellular area (CA), cellular diameter (CD), cellular perimeter (CP), and nucleocytoplasmic (N/C) ratio were used.

Results

There was a significant difference in the six groups of squamous cell abnormality based on NA, NP, ND, CA, CP, and CD (P < 0.05) using one-way analysis of variance. Nuclear morphometry parameters like NA, NP, and ND were found to be the maximum for HSIL, followed by LSIL, ASC-H, ASC-US, SCC, and NILM groups in decreasing order. The mean CA, CP, and CD were found to be the maximum for NILM, followed by LSIL, ASC-US, HSIL, ASC-H, and SCC in decreasing order. On post hoc analysis, the lesions can be divided into three groups: NILM/normal; ASC-US and LSIL; and ASC-H, HSIL, and SCC, based on N/C ratio.

Conclusion

In cervical lesions, holistic parameter of cytonucleomorphometry should be taken rather than taking nuclear morphometry only. N/C ratio is a highly statistically significant parameter that can differentiate between low-grade lesions and high-grade lesions.

Conjunctival cytologic features in patients with unilateral primary acquired nasolacrimal duct obstruction

PURPOSE

To evaluate the cytologic features of conjunctival epithelium in patients with unilateral primary acquired nasolacrimal duct obstruction (PANDO) using impression cytology.

METHODS

Twenty-four patients with unilateral PANDO for at least 1 year were enrolled in this study. The healthy eyes of the patients are assessed as control group. All patients were subjected to ophthalmic surface examination with conjunctival impression cytology analysis. Squamous metaplasia and goblet cell density were graded according to Nelson grading system.

RESULTS

The mean age was 52.7 ± 16.3 (range 21-70) years. The mean period for complaints of epiphora was 3.2 ± 2.4 (range 1-8) years. The eye with PANDO had a mean squamous metaplasia grade of 2.38 ± 0.59 versus 1.91 ± 0.82 for control eyes (p = 0.011). The mean grade of goblet cell density was 2.0 ± 0.51 for eyes with PANDO and 2.38 ± 0.65 for control eyes (p = 0.013). There was no statistically significant correlation between conjunctival cytological features in terms of squamous metaplasia and goblet cell density grades and duration of epiphora complaint (r = -0.04, p = 0.82; r = 0.09, p = 0.66, respectively).

CONCLUSIONS

PANDO may cause alterations in conjunctival impression cytology. Successful dacryocystorhinostomy surgeries will help to protect ocular surface health.

Corneal Surface and Superficial Cells as Viewed by Scanning Electron Microscopy and Impression Cytology Sampling

PURPOSE

To objectively compare sizes of corneal epithelial surface cells visualized by scanning electron microscopy (SEM) or collected by impression cytology (IC).

METHODS

Corneas of recent postmortem sheep eyes were either glutaraldehyde fixed for SEM or IC samples taken, glutaraldehyde fixed, and then stained with Giemsa. The corneal epithelial surface was examined at ×200, with the borders of all cells marked and dimensions and areas measured. For SEM, the cells were classified as having light, medium, or dark electron reflex and by the number of cell sides.

RESULTS

SEM revealed a mosaic of polygonal features with different electron reflexes according to the density of cell surface microplicae. The cell area and longest dimension were predictably dependent on the number of cell sides. Compared with the overall average cell area of 1598 μm(2) (range 200-3900 μm(2)), the dark reflex cells were predominantly the largest, with an average area of 2435 μm(2) and having the average longest dimension of 59.9 μm(2). Cells collected by IC had a range of areas from 1150 to 4800 μm(2) but were predominantly large and had an average area of 2802 μm(2) with the average cell longest dimension averaging 64.4 μm(2). IC-sampled cells had nucleocytoplasmic ratio values consistent with their having a squamous phenotype.

CONCLUSIONS

Cells sampled by IC from the corneal epithelial surface are predominantly those that are enlarged (and flattened out) in preparation for desquamation, a feature also attributed to the dark reflex cells seen in SEM.

Assessment of Consistency in Assignment of Severe (Grade 3) Squamous Metaplasia to Human Bulbar Conjunctiva Impression Cytology Cell Samples

Nucleus-to-cytoplasm (N:C) characteristics of published images of human bulbar conjunctival cells designated as showing severe (grade 3) squamous metaplasia were retrospectively assessed. From publications over a 40-year period, measurements were made from images of cell and nucleus size (based on areas and dimensions) and four different calculations were made for nucleo-cytoplasmic (N:C) ratios. From 54 published images, the mean nucleus-to-cytoplasm area ratio (NU/CYT AREA ratio) was 0.145 +/- 0.077 (range 0.052 to 0.346), compared to two different reference set values of 0.069 +/- 0.017 and 0.080 +/- 0.021. Similarly, a nucleus-to-cytoplasm length ratio (as LNLONG) was 0.308 +/- 0.080 (range 0.191 to 0.475) compared to reference values of 0.226 +/- 0.032 and 0.236 +/- 0.034. Similar differences in reference values were obtained using two other N:C ratio calculations. A wide range of values was found for morphometric N:C indices from published images, especially those without a scale bar, indicating a high incidence of inconsistent grading assignments. Overall, only about 30% of the published images showed morphological features consistent with severe squamous metaplasia (i.e., with the rest neither enlarged nor showing substantially changed N:C ratios) with no substantial pictorial evidence indicating that cells from the human bulbar conjunctiva have pyknotic nuclei. Current evidence indicates that grade 3 squamous metaplasia cells should be substantially enlarged.

A systematic assessment of goblet cell sampling of the bulbar conjunctiva by impression cytology

The purpose of this study was to assess the apparent goblet cell density (GCD) from conjunctival impression cytology (CIC) samples in relation to the number of conjunctival cells collected onto the filters. CIC specimens were collected from the superior-temporal bulbar conjunctiva of 16 pigmented rabbits onto Biopore (Millicell-CM) membranes, fixed with buffered glutaraldehyde and stained with Giemsa. Different numbers of microscope fields of view in each of the specimens were imaged by light microscopy using a 20× magnification objective lens (200× final magnification), and the goblet cells marked and counted. The GCD values/sq. mm were calculated. The same conjunctival region of 3 other rabbits was also prepared for transmission electron microscopy (TEM) by fixation, in situ, with the same buffered glutaraldehyde. Mean values for GCD estimates were found to vary from 399 to 1576 cells/sq. mm, depending on the image sampling and analysis strategy chosen, with the lowest inter-sample variance of around 10% being found if a maximum goblet cell count was taken on substantially multilayered regions of the CIC specimens. Counts of the number of goblet cells per 1000 visible conjunctival epithelial cells yielded a value of close to 90 (range 36-151), with modest inter-sample variability of around 30%. A three or ten 200× microscope field and random sampling strategy yielded mean GCD values between 542 and 670 cells/sq. mm, but with very high intra- and inter-sample variance of at least 60% and sometimes higher than 100%. TEM confirmed the multilayered organization of the conjunctiva and the deeper lying goblet cells. The general use of a goblet cell count as an objective marker for conjunctival normality or health is likely to be highly variable unless a more specific strategy is adopted. Beyond providing details of exactly the counting strategy used, it would be very useful to provide full details of the actual microscope field size used as well as information on the intra-sample variability in goblet cell counts.