Transcription Factor ATF3 Participates in DeltaNp63-Mediated Proliferation of Corneal Epithelial Cells.

Understanding the regulatory mechanisms underlying corneal epithelial cell (CEC) proliferation in vitro may provide the means to boost CEC production in cell therapy for ocular disorders. The transcription factor ΔNp63 plays a crucial role in the proliferation of CECs, but the underlying mechanisms is yet to be elucidated. TP63 and ΔNp63 are encoded by the TP63 gene via alternative promoters. We previously reported that both ΔNp63 and activating transcription factor (ATF3) are substantially expressed in cultured CECs, but the regulatory relationship between ΔNp63 and ATF3 is unknown. In the present study, we found that ΔNp63 increased ATF3 expression and ATF3 promoter activity in cultured CECs. The deletion of the p63 binding core site reduced ATF3 promoter activity. CECs overexpressing ATF3 exhibited significantly greater proliferation than control CECs. ATF3 knockdown suppressed the ΔNp63-induced increase in cell proliferation. Overexpression of ATF3 in CECs significantly elevated protein and mRNA levels of cyclin D. The protein levels of keratin 3/14, integrin ß1, and involucrin did not differ between ATF3-overexpressing CECs, ATF3-downregulated CECs, and control cells. In conclusion, our results suggest that ΔNp63 increases CEC proliferation via the ΔNp63/ATF3/CDK pathway.

Revisiting Existing Evidence of Corneal Endothelial Progenitors and Their Potential Therapeutic Applications in Corneal Endothelial Dysfunction.

PURPOSE: A recent successful clinical trial demonstrated that a less invasive cell-injection procedure is a viable medical modality for treating corneal endothelial dystrophy. This medical advance still relies on human corneal endothelial cell (HCEC) sources derived from rare cornea donations. The progenitor of the corneal endothelium, which has the characteristics of active proliferation and lineage restriction, will be an ideal cell source for expansion ex vivo. However, the distribution of progenitor-like cells in the corneal endothelial sheet has been under debate for more than a decade. METHODS: This paper re-examines the scientific evidence of the existence of human corneal endothelial progenitors (HCEPs) from the aspects of (1) the origin of cornea formation during ocular development, (2) manifestations from clinical studies, and (3) the distinctive properties of ex vivo-cultured subpopulations. RESULTS: The discrepancies regarding different types of progenitor-like cells in various locations of the cornea are based on the fact that the corneal endothelium is derived from different cell types with multiple origins during corneal formation. CONCLUSIONS: Resolving this long-standing issue in corneal biology will enable various types of progenitors to be isolated and their potencies regarding the formation of functional endothelial cells to be examined. Additionally, an effective niche system for quantitatively producing therapeutic cells can be formulated to satisfy the burning need associated with corneal endothelial dystrophy in the future.

Early keratectomy in the treatment of moderate Fusarium keratitis.

PURPOSE: To evaluate the treatment outcomes and costs of early keratectomy in the management of moderate Fusarium keratitis. METHODOLOGY/PRINCIPAL FINDINGS: Consecutive cases of culture proven Fusarium keratitis treated at our hospital between January 2004 to December 2010 were included in this retrospective study. There were 38 cases of moderate keratitis with infiltrates between 3 to 6 mm in diameter and depth of infiltration not exceeding the inner 1/3 of the cornea. After excluding 5 patients with incomplete follow-up data, 13 patients who received early keratectomy within 1 week of admission were compared with a group of 20 patients treated medically. The significance of the association between early keratectomy and visual acuity, progression to perforation, secondary glaucoma and cataract formation, adjuvant therapy, hospitalization days and cost were assessed. There were no differences between the keratectomy and medication groups in regards to age, sex, presence of systemic diseases, and hypopyon formation on presentation. The early keratectomy group had a shorter hospital stay than the medical therapy group. Disease duration was significantly lower in the early keratectomy group (median: 29.0 vs. 54.5 days, P<0.001). Median hospitalization costs per patient were lower with early keratectomy (mean ward fee: 15175.4 vs. 44159.5 NTD, P<0.001; mean donor fee: 0 vs. 900.0 NTD, P<0.001), primarily because of reductions in hospital stay. More patients in the medication group developed perforations than in the keratectomy group (20% vs. 0%, respectively) and the perforation-free rate was higher in those with early keratectomy, but the results were not statistically significant. CONCLUSIONS/SIGNIFICANCE: Early keratectomy in moderate Fusarium keratitis may reduce length of hospital stay, hospital costs, and perforation rates.

STAT3 regulates the proliferation and differentiation of rabbit limbal epithelial cells via a ΔNp63-dependent mechanism.

PURPOSE: To explore the roles of STAT3 in the regulation of ΔNp63-dependent proliferation and differentiation of rabbit limbal keratinocytes. METHODS: siRNAs were designed to specifically suppress the expression of STAT3 and ΔNp63, and their effects on limbal epithelial cell proliferation and differentiation were examined. Ectopically expressed ΔNp63 was used to compensate for the decreased endogenous ΔNp63. Immunoblot was used to examine the expressions of STAT3, ΔNp63, K3, integrin ß1, and involucrin. RESULTS: Limbal tissue expresses higher level of phosphorylated and nuclear translocated STAT3 compared with that of the cornea. Knockdown of STAT3 expression reduces the expression of ΔNp63, inhibits the expansion of limbal epithelial outgrowth, suppresses the expression of integrin ß1, and promotes the expression of involucrin. CONCLUSIONS: STAT3 enhances the proliferation of limbal keratinocytes through a ΔNp63-dependent mechanism. Suppression of this pathway inhibits cell proliferation with a concomitant increase of cell differentiation.