Aquaporin 5 promotes corneal wound healing

Reticulated Retinoic Acid Synthesis is Implicated in the Pathogenesis of Dry Eye in Aqp5 Deficiency Mice

Purpose

Abnormalities in aquaporins are implicated in the pathological progression of dry eye syndrome. Retinoic acid (RA) regulates cellular proliferation, differentiation, and apoptosis in the cornea, thereby being associated with dry eye disease (DED). The objective of this study is to explore the underlying mechanisms responsible for RA metabolic abnormalities in corneas lacking aquaporin 5 (AQP5).

Methods

Dry eye (DE) models were induced via subcutaneous scopolamine hydrobromide. Aqp5 knockout (Aqp5-/-) mice and DE mice were utilized to assess corneal epithelial alterations. Tear secretion, goblet cell counts, and corneal punctate defects were evaluated. The impact of Aqp5 on RA-related enzymes and receptors was investigated using pharmacological RA or SR (A JunB inhibitor), a transcription factor JunB inhibitor, treatment in mouse corneal epithelial cells (CECs), or human corneal epithelial cells (HCECs). The HCECs and NaCl-treated HCECs underwent quantitative real-time PCR (qRT-PCR), immunofluorescent, Western blot, and TUNEL assays. The regulation of transcription factor JunB on Aldh1a1 was explored via ChIP-PCR.

Results

Aqp5 and Aldh1a1 were reduced in both CECs of DE mice and NaCl-induced HCECs. Aqp5-/- mice exhibited DE phenotype and reduced Aldh1a1. RA treatment reduced apoptosis, promoted proliferation, and improved the DE phenotype in Aqp5-/- mice. JunB enrichment in the Aldh1a1 promoter was identified by ChIP-PCR. SR significantly increased Aldh1a1 expression, Ki67, and ΔNp63-positive cells, and decreased TUNEL-positive cells in CECs and HCECs.

Conclusions

Our findings demonstrated the downregulation of Aqp5 expression and aberrant RA metabolism in DE conditions. Knockout of Aqp5 resulted in reduced production of RA through activation of JunB, subsequently leading to the manifestation of DE symptoms.

AQP5 promotes epithelial-mesenchymal transition and tumor growth through activating the Wnt/β-catenin pathway in triple-negative breast cancer

BACKGROUND

Emerging data identifies aquaporin 5 (AQP5) as a vital player in many kinds of cancers. Over expression of AQP5 was associated with increased metastasis and poor prognosis, suggesting that AQP5 may facilitate cancer cell proliferation and migration. Our previous studies also showed that AQP3 and AQP5 were highly expressed in triple-negative breast cancer (TNBC) and the expression of AQP3 and AQP5 in TNBC tissue was positive correlated with advanced clinical stage.

OBJECTIVE

We aim to investigate the role of AQP5 in TNBC oncogenesis and development.

METHODS

MDA-MB-231 cells were transfected with siRNA-AQP5 and AQP5 overexpression vector to establish a differential expression system for AQP5. Cell proliferation and apoptosis of MDA-MB-231 cells were detected by CCK-8 (Cell Counting Kit-8) and FCM (flow cytometry), respectively. Cell migration and invasion abilities were evaluated by wound healing assay and transwell assay. The qRT-PCR and western blot assays were used to study the effect of AQP5 expression level on the expression of epithelial-to-mesenchymal transition (EMT) related molecules. The effects of ICG-001, a Wnt/β-catenin signaling pathway inhibitor, on the invasive and migratory capabilities of overexpressed AQP5 cells and downstream molecules were measured.

RESULTS

1. The expression of AQP5 in the MDA-MB-231 cells was significantly higher than that in the MCF-10A cells. 2. Up-regulation of AQP5 significantly promoted the proliferation, migration and invasion of TNBC cells, while inhibited the cell apoptosis; in addition, up-regulation of AQP5 increased the expression of Bcl-2 and decreased the expression of Caspase-3. However, knockdown of AQP5 presented the adverse effects of AQP5 overexpression. 3. Overexpressed AQP5 induced the overexpression of EMT-related factors, which further promoted the migration and invasion of cells. 4. Overexpression of AQP5 could up-regulate the expression of β-catenin in the nucleus followed by increasing the expression levels of downstream genes in Wnt/β-catenin signaling pathway. Moreover, ICG-001, the inhibitor of Wnt/β-catenin signaling pathway, could significantly attenuate the effect of overexpression of AQP5 on cells, further confirming that AQP5 may promote the proliferation, migration and invasion of TNBC cells by activating Wnt/β-catenin signaling pathway.

CONCLUSIONS

In the TNBC cells, AQP5 modulates the expression levels of EMT-related proteins through activation of Wnt/β-catenin signaling pathway, thus enhancing the cell proliferation, migration and invasion while inhibiting the cell apoptosis.

PAX6/CXCL14 regulatory axis promotes the repair of corneal injury by enhancing corneal epithelial cell proliferation

BACKGROUND

Corneal injuries, often leading to severe vision loss or blindness, have traditionally been treated with the belief that limbal stem cells (LSCs) are essential for repair and homeostasis, while central corneal epithelial cells (CCECs) were thought incapable of such repair. However, our research reveals that CCECs can fully heal and maintain the homeostasis of injured corneas in rats, even without LSCs. We discovered that CXCL14, under PAX6's influence, significantly boosts the stemness, proliferation, and migration of CCECs, facilitating corneal wound healing and homeostasis. This finding introduces CXCL14 as a promising new drug target for corneal injury treatment.

METHODS

To investigate the PAX6/CXCL14 regulatory axis's role in CCECs wound healing, we cultured human corneal epithelial cell lines with either increased or decreased expression of PAX6 and CXCL14 using adenovirus transfection in vitro. Techniques such as coimmunoprecipitation, chromatin immunoprecipitation, immunofluorescence staining, western blot, real-time PCR, cell colony formation, and cell cycle analysis were employed to validate the axis's function. In vivo, a rat corneal epithelial injury model was developed to further confirm the PAX6/CXCL14 axis's mechanism in repairing corneal damage and maintaining corneal homeostasis, as well as to assess the potential of CXCL14 protein as a therapeutic agent for corneal injuries.

RESULTS

Our study reveals that CCECs naturally express high levels of CXCL14, which is significantly upregulated by PAX6 following corneal damage. We identified SDC1 as CXCL14's receptor, whose engagement activates the NF-κB pathway to stimulate corneal repair by enhancing the stemness, proliferative, and migratory capacities of CCECs. Moreover, our research underscores CXCL14's therapeutic promise for corneal injuries, showing that recombinant CXCL14 effectively accelerates corneal healing in rat models.

CONCLUSION

CCECs play a critical and independent role in the repair of corneal injuries and the maintenance of corneal homeostasis, distinct from that of LSCs. The PAX6/CXCL14 regulatory axis is pivotal in this process. Additionally, our research demonstrates that the important function of CXCL14 in corneal repair endows it with the potential to be developed into a novel therapeutic agent for treating corneal injuries.

Aquaporins in the Cornea

The cornea is an avascular, transparent tissue that allows light to enter the visual system. Accurate vision requires proper maintenance of the cornea's integrity and structure. Due to its exposure to the external environment, the cornea is prone to injury and must undergo proper wound healing to restore vision. Aquaporins (AQPs) are a family of water channels important for passive water transport and, in some family members, the transport of other small molecules; AQPs are expressed in all layers of the cornea. Although their functions as water channels are well established, the direct function of AQPs in the cornea is still being determined and is the focus of this review. AQPs, primarily AQP1, AQP3, and AQP5, have been found to play an important role in maintaining water homeostasis, the corneal structure in relation to proper hydration, and stress responses, as well as wound healing in all layers of the cornea. Due to their many functions in the cornea, the identification of drug targets that modulate the expression of AQPs in the cornea could be beneficial to promote corneal wound healing and restore proper function of this tissue crucial for vision.

Microsporidia persistence in host impairs epithelial barriers and increases chances of inflammatory bowel disease

Microsporidia are intracellular fungus-like pathogens and the infection symptoms include recurrent diarrhea and systematic inflammations. The major infection route of microsporidia is the digestive tract. Since microsporidia are hard to fully eliminate, the interactions and persistence of the pathogen within epithelium may modulate host susceptibility to digestive disorders. In this study, both in vitro and in vivo infection models were applied. The alterations of epithelial barrier integrity, permeability, and tight junction proteins after microsporidia infection were assessed on MDCK/Caco-2 monolayers. The fecal intestinal microbiota and tissue alterations after microsporidia infection were assessed on C57BL/6 mice. Moreover, the susceptibility to develop dextran sulfate sodium (DSS)-induced inflammatory bowel diseases (IBDs) was also analyzed by the murine infection model. The results demonstrated that microsporidia infection increased epithelium permeability, weakened wound healing capability, and destructed tight junction protein zonula occludens-1. Microsporidia infection also dysregulates intestinal microbiota. These impairing effects of microsporidia increased host vulnerability to develop enteritis as shown by the murine model of DSS-induced IBD. Our study is the first to elucidate molecular mechanisms of the damaging effects of microsporidia on host epithelium and pointed out the cryptic threats of latent microsporidia infection to public health as reflected by the increased chances of developing more severe diseases.IMPORTANCEMicrosporidia are widely present in nature and usually cause latent and persistent infections in hosts. Given the fact that the digestive tract is the major infection route, it is of great importance to explore the consequences of microsporidia infection on the intestinal epithelial barrier and the risks to the host. In this study, we demonstrated the destructing effects of microsporidium infection on epithelial barriers manifested as increased epithelial permeability, weakened wound healing ability, and disrupted tight junctions. Moreover, microsporidia made the host more susceptible to dextran sulfate sodium-induced inflammatory bowel disease. These findings provide new evidence for us to better understand and develop novel strategies for microsporidia prevention and disease control.

Aquaporin 5 in the eye: Expression, function, and roles in ocular diseases

As a water channel protein, aquaporin 5 (AQP5) is essential for the maintenance of the normal physiological functions of ocular tissues. This review provides an overview of the expression and function of AQP5 in the eye and discusses their role in related eye diseases. Although AQP5 plays a vital role in ocular functions, such as maintaining corneal and lens transparency, regulating water movement, and maintaining homeostasis, some of its functions in ocular tissues are still unclear. Based on the key role of AQP5 in eye function, this review suggests that in the future, eye diseases may be treated by regulating the expression of aquaporin.

The multifaceted role of aquaporins in physiological cell migration

Cell migration is an essential process that underlies many physiological processes, including the immune response, organogenesis in the embryo, and angiogenesis, as well as pathological processes such as cancer metastasis. Cells have at their disposal a variety of migratory behaviors and mechanisms that seem to be specific to cell type and the microenvironment. Research over the past two decades has elucidated the water channel protein family of aquaporins (AQPs) as a regulator of many cell migration-related processes, from physical phenomena to biological signaling pathways. The roles that AQPs play in cell migration are both cell type- and isoform-specific; thus, a large swath of information has accumulated as researchers seek to identify the responses across these distinct variables. There does not seem to be a universal role that AQPs play in cell migration; the complex interplay between AQPs and cell volume management, signaling pathway activation, and in a few identified circumstances, gene expression regulation, has shown the intricate, and perhaps paradoxical, role of AQPs in cell migration. The objective of this review is to provide an organized and integrated collection of recent work that has elucidated the many mechanisms by which AQPs regulate cell migration.NEW & NOTEWORTHY Research has elucidated the water channel protein family of aquaporins (AQPs) as a regulator of many cell migration-related processes, from physical phenomena to biological signaling pathways. The roles that AQPs play in cell migration are both cell type- and isoform-specific; thus, a large swath of information has accumulated as researchers seek to identify the responses across these distinct variables. This review compiles insights into the recent findings linking AQPs to physiological cell migration.

Role of aquaporins in corneal healing post chemical injury

Aquaporins (AQPs) are transmembrane water channel proteins that regulate the movement of water through the plasma membrane in various tissues including cornea. The cornea is avascular and has specialized microcirculatory mechanisms for homeostasis. AQPs regulate corneal hydration and transparency for normal vision. Currently, there are 13 known isoforms of AQPs that can be subclassified as orthodox AQPs, aquaglyceroporins (AQGPs), or supraquaporins (SAQPs)/unorthodox AQPs. AQPs are implicated in keratocyte function, inflammation, edema, angiogenesis, microvessel proliferation, and the wound-healing process in the cornea. AQPs play an important role in wound healing by facilitating the movement of corneal stromal keratocytes by squeezing through tight stromal matrix and narrow extracellular spaces to the wound site. Deficiency of AQPs can cause reduced concentration of hepatocyte growth factor (HGF) leading to reduced epithelial proliferation, reduced/impaired keratocyte migration, reduced number of keratocytes in the injury site, delayed and abnormal wound healing process. Dysregulated AQPs cause dysfunction in osmolar homeostasis as well as wound healing mechanisms. The cornea is a transparent avascular tissue that constitutes the anterior aspect of the outer covering of the eye and aids in two-thirds of visual light refraction. Being the outermost layer of the eye, the cornea is prone to injury. Of the 13 AQP isoforms, AQP1 is expressed in the stromal keratocytes and endothelial cells, and AQP3 and AQP5 are expressed in epithelial cells in the human cornea. AQPs can facilitate wound healing through aid in cellular migration, proliferation, migration, extracellular matrix (ECM) remodeling and autophagy mechanism. Corneal wound healing post-chemical injury requires an integrative and coordinated activity of the epithelium, stromal keratocytes, endothelium, ECM, and a battery of cytokines and growth factors to restore corneal transparency. If the chemical injury is mild, the cornea will heal with normal clarity, but severe injuries can lead to partial and/or permanent loss of corneal functions. Currently, the role of AQPs in corneal wound healing is poorly understood in the context of chemical injury. This review discusses the current literature and the role of AQPs in corneal homeostasis, wound repair, and potential therapeutic target for acute and chronic corneal injuries.

Aquaporin5 Deficiency Aggravates ROS/NLRP3 Inflammasome-Mediated Pyroptosis in the Lacrimal Glands

Purpose

The pathogenesis of the lacrimal glands (LGs) is facilitated by inflammation mediated by the NACHT, LRR, and NLRP3 inflammasomes in dry eye disease. This research aimed to explore the protective effects of Aquaporin 5 (AQP5) on LGs by inhibiting reactive oxygen species (ROS) and the NLRP3 inflammasome.

Methods

AQP5 knockout (AQP5-/-) mice were used to evaluate pathological changes in LGs. ROS generation was detected with a dichlorodihydro-fluorescein diacetate assay. Lipid metabolism was assessed by Oil Red O staining. The reversal of the mitochondrial membrane potential was detected using a JC-1 fluorescent probe kit. The effect of AQP5 on NLRP3/caspase-1/Gasdermin-D (GSDMD)-mediated pyroptosis was examined using pharmacological treatment of N-acetyl L-cysteine or MCC950.

Results

AQP5 loss significantly increased ROS generation, lipid metabolism disorders, TUNEL-positive cells, and reversal of the mitochondrial membrane potential in the AQP5-/- LGs. NLRP3 upregulation, increased caspase-1 and GSDMD activity, and enhanced IL-1β release were detected in the AQP5-/- mouse LGs and primary LG epithelial cells. MCC950 significantly suppressed NLRP3 inflammasome-related pyroptosis induced by AQP5 deficiency in LGs and primary LG epithelial cells. Furthermore, we discovered that prestimulating the AQP5-/- primary LG epithelial cells with N-acetyl L-cysteine decreased NLRP3 expression, caspase-1 and GSDMD activity levels, and IL-1β release.

Conclusions

Our results revealed that AQP5 loss promoted NLRP3 inflammasome activation through ROS generation. Inhibiting the ROS or NLRP3 inflammasome significantly alleviated the damage and pyroptosis of AQP5-deficient LG epithelial cells, which could provide new insights into dry eye disease.

The Extracts of Dendrobium Alleviate Dry Eye Disease in Rat Model by Regulating Aquaporin Expression and MAPKs/NF-κB Signalling

Dry eye is one of the most common ocular surface diseases caused by tear film instability and ocular surface damage due to an abnormal quality or quantity of tears. Inflammatory factors can initiate relevant transduction signalling pathways and trigger the inflammatory cascade response, resulting in ocular surface inflammation. It has been shown that the active ingredients in Dendrobium, such as polysaccharides, alkaloids and phenols, have anti-inflammatory, anti-tumour and immunity-boosting effects, and Dendrobium officinale extract can improve glandular secretion function, increase salivary secretion and increase the expression level of water channel protein in salivary glands in patients with dry eye syndromes. We investigated the in vitro cytoprotective effect of Dendrobium extracts in sodium chloride induced hyperosmotic conditions in human cornea keratocytes (HKs). Results showed that Dendrobium officinale Kimura et Migo water extract (DOW) and Dendrobium loddigesii Rolfe water extract (DLW) could upregulate the expression of aquaporins (AQP)5 protein, thus exerting a repairing effect by promoting cell migration. Furthermore, oral administration of DOW and DLW enhanced tear production in rats and exerted a protective effect on ocular surface damage. DOW and DLW could upregulate the expression of AQP5 and mucin (muc)5ac proteins in the lacrimal gland and reduce the inflammatory response. DOW and DLW inhibited the activation of the corresponding mitogen-activated protein kinases (MAPK) and NF-KB pathway, thereby playing a role in improving dry eye symptoms. This study provides a new perspective on dry eye treatment, and DOW and DLW may be potential therapeutic agents for dry eye.

Comprehensive Analysis of Aquaporin Superfamily in Lung Adenocarcinoma

Background: Lung adenocarcinoma (LUAD) is the most predomintnt lung cancer subtype with increasing morbidity and mortality. Previous studies have shown that aquaporin (AQP) family genes were correlated with tumor progression and metastasis in several kinds of malignancies. However, their biological behaviors and prognostic values in LUAD have not been comprehensively elucidated.

Methods: RNA sequencing and real-time reverse transcription PCR (RT-PCR) were used to assess AQP1/3/4/5 gene expressions in LUAD patients using GEPIA and UALCAN databases. And then Kaplan–Meier analysis, cBioPortal, Metascape, GeneMANIA, TISIDB, and TIMER were utilized to determine the prognostic value, mutation frequency, and immune cell infiltration of AQP family members in LUAD.

Results: We found that AQP3 expression was significantly elevated and AQP1 expression was markedly reduced in LUAD patients, whereas the expression levels of AQP4 and AQP5 exhibited no significant changes. The Kaplan–Meier survival analysis indicated that the higher expressions of AQP1/4/5 were related to longer overall survival (OS). Of interest, AQP3 was significantly correlated with the clinical tumor stage and lower AQP3 expression showed favorable prognosis in stage I LUAD patients, which indicated that AQP3 may be a potential prognostic biomarker for patients. Through functional enrichment analysis, the functions of these four AQPs genes were mainly involved in the passive transport by aquaporins, water homeostasis, and protein tetramerization. Moreover, AQP1/3/4/5 expression was strongly associated with tumor-infiltrating lymphocytes (TILs) in LUAD.

Conclusion: AQP3 can be used as a prognosis and survival biomarker for stage I LUAD. These findings may provide novel insights into developing molecular targeted therapies in LUAD.

Aquaporins 8 and 9 as Possible Markers for Adult Murine Lacrimal Gland Cells

Aquaporins (AQPs) are proteins that selectively transport water across the cell membrane. Although AQPs play important roles in secretion in the lacrimal gland, the expression and localization of AQPs have not been clarified yet. In the current study, we investigated the expression pattern of AQP family members in the murine lacrimal gland during development. Lacrimal gland tissues were harvested from E13.5 and E17.5 murine embryos and from mice 8 weeks of age (adults). Corneal and conjunctival tissues from the latter served as controls. Total RNA was isolated and analyzed for the expression of AQP family members using qPCR. The localization of AQPs in the adult lacrimal gland in adult murine lacrimal glands was also analyzed. Expression of Aqp8 and Aqp9 mRNAs was detected in the adult lacrimal gland but not in the cornea, conjunctiva, or fetal lacrimal gland. AQP8 and AQP9 and α-SMA partially colocalized around the basal regions of the acinar unit. The levels of Aqp3 mRNAs and protein were much lower in the adult lacrimal gland but were readily detected in the adult cornea and conjunctiva. Our study suggests that AQP8 and AQP9 may serve as markers for adult murine lacrimal gland, ductal, and myoepithelial cells.

Aquaporin 5 Facilitates Corneal Epithelial Wound Healing and Nerve Regeneration by Reactivating Akt Signaling Pathway

Aquaporins (AQPs) are normally expressed in the corneal epithelium. The aim of this study was to determine whether AQP5 played a role in corneal epithelial wound healing. AQP5 knockout (AQP5^-/-) mice were constructed using CRISPR/Cas9 technology. A corneal wound healing model was performed using epithelial debridement on corneas. The time to corneal epithelial and nerve regeneration was significantly delayed in the AQP5^-/- mice. Reduced Ki-67-positive cells and nerve growth factor (NGF) expression were confirmed in the AQP5^-/- mice during healing. The epithelial and nerve regeneration rates were significantly promoted in the AQP5^-/- mice by treatment with NGF, which was accompanied by recovered levels of phosphorylated Akt. NGF treatment also improved the recovery of corneal nerve fiber density and sensitivity in the AQP5^-/- mice. However, the promotion of NGF induced corneal epithelial and nerve regeneration rates, and Akt reactivation was reversed by Akt inhibitor. The significant impairment of corneal wound healing in the AQP5^-/- mice resulted from distinct defects in corneal epithelial cell proliferation and nerve regeneration. The results provided evidence for the involvement of aquaporin in cell proliferation and suggested that AQP5 induction could be a potential therapy for accelerating the resurfacing of corneal defects.

Molecular characteristics and spatial distribution of adult human corneal cell subtypes

Bulk RNA sequencing of a tissue captures the gene expression profile from all cell types combined. Single-cell RNA sequencing identifies discrete cell-signatures based on transcriptomic identities. Six adult human corneas were processed for single-cell RNAseq and 16 cell clusters were bioinformatically identified. Based on their transcriptomic signatures and RNAscope results using representative cluster marker genes on human cornea cross-sections, these clusters were confirmed to be stromal keratocytes, endothelium, several subtypes of corneal epithelium, conjunctival epithelium, and supportive cells in the limbal stem cell niche. The complexity of the epithelial cell layer was captured by eight distinct corneal clusters and three conjunctival clusters. These were further characterized by enriched biological pathways and molecular characteristics which revealed novel groupings related to development, function, and location within the epithelial layer. Moreover, epithelial subtypes were found to reflect their initial generation in the limbal region, differentiation, and migration through to mature epithelial cells. The single-cell map of the human cornea deepens the knowledge of the cellular subsets of the cornea on a whole genome transcriptional level. This information can be applied to better understand normal corneal biology, serve as a reference to understand corneal disease pathology, and provide potential insights into therapeutic approaches.

Unexpected localization of AQP3 and AQP4 induced by migration of primary cultured IMCD cells

Aquaporin-2-4 (AQP) are expressed in the principal cells of the renal collecting duct (CD). Beside their role in water transport across membranes, several studies showed that AQPs can influence the migration of cells. It is unknown whether this also applies for renal CD cells. Another fact is that the expression of these AQPs is highly modulated by the external osmolality. Here we analyzed the localization of AQP2-4 in primary cultured renal inner medullary CD (IMCD) cells and how osmolality influences the migration behavior of these cells. The primary IMCD cells showed a collective migration behavior and there were no differences in the migration speed between cells cultivated either at 300 or 600 mosmol/kg. Acute increase from 300 to 600 mosmol/kg led to a marked reduction and vice versa an acute decrease from 600 to 300 mosmol/kg to a marked increase in migration speed. Interestingly, none of the analyzed AQPs were localized at the leading edge. While AQP3 disappeared within the first 2-3 rows of cells, AQP4 was enriched at the rear end. Further analysis indicated that migration induced lysosomal degradation of AQP3. This could be prevented by activation of the protein kinase A, inducing localization of AQP3 and AQP2 at the leading edge and increasing the migration speed.

Modulatory effect of aquaporin 5 on estrogen-induced epithelial-mesenchymal transition in prostate epithelial cells

Background

Estrogen is involved in the pathophysiological process of benign prostatic hyperplasia (BPH), in which epithelial-mesenchymal transition (EMT) plays an important role. Upregulation of aquaporin (AQP) 5, which is directly activated by estrogen, has been reported to promote EMT in multiple cells. This study aimed to examine the effects of AQP5 on estrogen-induced EMT in the prostate.

Methods

Normal prostate (NP) tissue samples without any histopathological changes and BPH tissue samples with pathologically confirmed hyperplasia were obtained. An EMT cell model was subsequently established by adding estradiol (E2) to RWPE-1 cells, after which AQP5 knockdown was performed. Tissue morphological and immunohistochemical features were examined using hematoxylin-eosin and immunohistochemical staining. Western blot analysis was performed to determine the expression of AQPs, estrogen receptors, and EMT-related proteins. Cell proliferation was assessed and supernatants were collected for enzyme-linked immunosorbent assay to determine transforming growth factor-β1 (TGF-β1) concentrations. Immunofluorescence staining was performed to assess protein expressions in RWPE-1 cells.

Results

BPH tissues exhibited greater EMT (TGF-β1: 1.362 ± 0.196 vs. 0.107 ± 0.067, P = 0.003; vimentin: 1.581 ± 0.508 vs. 0.221 ± 0.047, P < 0.001; E-cadherin: 0.197 ± 0.188 vs. 1.344 ± 0.088, P < 0.001), higher AQP5 (1.268 ± 0.136 vs. 0.227 ± 0.055, P < 0.001) and estrogen receptor (ER) α (1.250 ± 0.117 vs. 0.329 ± 0.134, P < 0.001) expression but lower ERβ (0.271 ± 0.184 vs. 1.564 ± 0.130, P < 0.001) expression than NP tissues. E2-stimulated cells had higher AQP5 expression (1.298 ± 0.058 vs. 1.085 ± 0.104, P = 0.049), increased cell proliferation (1.510 ± 0.089 vs.1.000 ± 0.038, P < 0.001), and EMT (TGF-β1 concentration: 0.352 ± 0.021 ng/mL vs. 0.125 ± 0.014 ng/mL, P < 0.001; vimentin: 1.641 ± 0.120 vs. 0.188 ± 0.020, P = 0.002; E-cadherin: 0.075 ± 0.030 vs. 0.843 ± 0.046, P < 0.001) than controls. E2-stimulated cells with AQP5 knockdown exhibited decreased EMT (TGF-β1 concentration: 0.223 ± 0.041 ng/mL vs. 0.352 ± 0.021 ng/mL, P = 0.016; vimentin: 0.675 ± 0.056 vs. 1.641 ± 0.120, P = 0.001; E-cadherin: 0.159 ± 0.037 vs. 0.075 ± 0.030, P = 0.040) than E2-stimulated cells with non-related small interfering RNA (siRNA).

Conclusion

Our findings suggest that estrogen induces BPH possibly by promoting AQP5 expression. Hence, AQP5 might be a novel target for modulating EMT in prostate epithelial cells.

Expression Profiles of CircRNA and mRNA in Lacrimal Glands of AQP5-/- Mice With Primary Dry Eye

Purpose: This work aimed to identify differentially expressed circular RNAs (circRNAs) and elucidate their potential function in aquaporin 5 (AQP5) knockout (AQP5^–/–) mice with the primary dry eye phenotype.

Methods: A slit lamp examination was performed on AQP5^–/– mice to assess corneal epithelial defects using fluorescein sodium staining. Hematoxylin–eosin staining and transmission electron microscopy analysis were performed to identify structural changes in lacrimal gland epithelial cells due to AQP5 deficiency. The expression profiles of circRNA and messenger RNA (mRNA) were determined by a microarray analysis. The selected circRNA was verified by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to predict the biological functions and the potential pathways of parental genes involved in lacrimal gland epithelial cell changes. According to the bioinformatics analysis of identified circRNAs, we predicted a circRNA–miRNA–mRNA network of phagosomes.

Results: The AQP5^–/– mice spontaneously exhibit dry eye symptoms, wherein the AQP5 deficiency changes the structure of lacrimal gland epithelial cells. The analysis revealed that, compared to AQP5^+/+ mice, 30 circRNAs in the lacrimal glands of AQP5^–/– mice were differentially expressed (fold change ≥ 2.0, p < 0.05). Nine upregulated circRNAs were identified using qRT-PCR, and nine upregulated validated circRNAs, 40 altered microRNAs (miRNAs), and nine upregulated mRNAs were identified through a network analysis. The KEGG analysis showed that these nine target genes were expressed in phagosomes.

Conclusion: The AQP5^–/– mice have primary and stable dry eye phenotypes from birth. We identified differently expressed circRNAs in the lacrimal glands of AQP5^–/– and AQP5^+/+ mice, predicting a circRNA–miRNA–mRNA network of phagosomes. CircRNA likely plays an important role in lacrimal gland epithelial cell pathogenesis. Therefore, it is reasonable to use circRNA as a potential therapeutic agent for the treatment of dry eyes.

Distinct expression patterns of aquaporin 3 and 5 in ductal and alveolar epithelial cells in mouse mammary glands before and after parturition

Milk osmolarity maintains an isotonic status for suckling infants during lactation. However, it remains unclear how the water content in milk is regulated in lactating mammary glands. In lactating mammary alveoli and ducts, mammary epithelial cells (MECs) are in direct contact with milk. In this study, we focus on two types of water channels, aquaporin 3 (AQP3) and AQP5, in alveolar and ductal MECs before and after parturition. AQP3 showed diffuse localization in the cytoplasm of ductal MECs but concentrated localization in the basolateral membrane of alveolar MECs during the late pregnancy and lactation periods. Translocation of AQP5 from the cytoplasm toward the apical membrane occurred in ductal MECs immediately before parturition. Subsequently, we examined the hormonal influences on the expression of AQP3 and AQP5 in cultured MECs in vitro. Progesterone and estrogen distinctly increased AQP3 and AQP5 in cultured MECs, respectively. Cotreatment with prolactin and dexamethasone significantly decreased both AQP3 and AQP5. Prolactin also facilitated the translocation of AQP5 into the apical membrane of MECs. In cultured MECs, AQP3 was homogeneously expressed in MECs, whereas AQP5 showed different expression levels between MECs regardless of the hormonal treatment. Different activation states of the prolactin/STAT5 pathway were also observed between ductal and alveolar MECs. These findings suggest that the expression pattern of AQP3 and AQP5 is distinctly regulated by lactogenic hormones in alveolar and ductal MECs before and after parturition. AQP5 expressed in ductal MECs may function as a water channel to regulate milk osmolarity in mice.

Rescue of human corneal epithelial cells after alkaline insult using renalase derived peptide, RP-220

AIM

To study the effect of renalase peptide, RP-220, on cell viability of human corneal epithelial cells after alkali insult.

METHODS

A dose-response relationship between cell viability and exposure to NaOH solution were characterized using cultured human corneal epithelial cells. Viability of corneal epithelial cells was determined using commercially available MTT and CyQUANT^® assays.

RESULTS

At a concentration of 6 mmol/L, insult with NaOH leads to reduced corneal epithelial cell viability by approximately 30%. This reduced viability was prevented by treating the cells after initial insult with the 20-amino acid renalase derived peptide (RP-220).

CONCLUSION

RP-220 has a pro-survival role for RP-220 following alkaline insult to corneal epithelial cells.

Biomaterials and controlled release strategy for epithelial wound healing

The skin and cornea are tissues that provide protective functions. Trauma and other environmental threats often cause injuries, infections and damage to these tissues, where the degree of injury is directly correlated to the recovery time. For example, a superficial skin or corneal wound may recover within days; however, more severe injuries can last up to several months and may leave scarring. Thus, therapeutic strategies have been introduced to enhance the wound healing efficiency and quality. Although the skin and cornea share similar anatomic structures and wound healing process, therapeutic agents and formulations for skin and cornea wound healing differ in accordance with the tissue and wound type. In this review, we describe the anatomy and epithelial wound healing processes of the skin and cornea, and summarize the therapeutic molecules that are beneficial to the respective regeneration process. In addition, biomaterial scaffolds that inherently possess bioactive properties or modified with therapeutic molecules for topical controlled release and enhanced wound healing efficiency are also discussed.

Altered expression of aquaporin 1 and aquaporin 5 in the cornea after primary blast exposure

PURPOSE

Our study aimed to determine whether the altered expression of biomarkers linked to corneal injuries, such as the edema-regulating proteins aquaporin-1 and aquaporin-5 (AQP1 and AQP5), occurred following primary blast exposure.

METHODS

Adult male Dutch Belted rabbits were anesthetized and exposed to blast waves with peak overpressures of 142.5-164.1 kPa (20.4-23.4 psi). These exposure groups experienced peak blast overpressure-specific impulses (impulse per unit surface area) of 199.6-228.5 kPa-ms. Unexposed rabbits were included as controls. The animals were euthanized at 48 h post-exposure. Corneas obtained from the euthanized blast-exposed and control rabbits were processed for quantitative PCR and western blot to quantify mRNA and the protein expression of AQP1 and AQP5. Immunohistochemical analysis was conducted to determine the cellular localization of AQP1 and AQP5.

RESULTS

Corneal thickness increased up to 18% with the peak blast overpressure-specific impulses of 199.6-228.5 kPa-ms at 48 h after blast exposure. mRNA levels of AQP1 and AQP5 increased in the whole cornea lysates of blast-exposed rabbits relative to those of the controls. Western blot analyses of whole cornea lysates revealed that the expression levels of AQP1 and AQP5 were approximately 2- and 1.5-fold higher, respectively, in blast-exposed rabbits compared to controls. The extent of AQP1 immunostaining (AQP1-IS) increased in the epithelial cell layer after blast exposure. The AQP5-IS pattern changed from a mixed membrane and cytoplasmic expression in the controls to predominantly cytoplasmic expression in the basally located cornea epithelial cells of blast-exposed rabbits.

CONCLUSIONS

Primary blast exposure resulted in edema-related changes in the cornea manifested by the altered expression of the edema-regulating proteins AQP1 and AQP5 with blast overpressure-specific impulses. These findings support potential acute corneal injury mechanisms in which the altered regulation of water permeability is caused by primary blast exposure.

Effect of D-Panthenol on Corneal Epithelial Healing after Surface Laser Ablation

Purpose

To study the effect of D-panthenol (provitamin B5) on corneal epithelial healing, in cases of surface laser ablation. Patients and Methods: 45 eyes, of 45 patients undergoing laser surface ablation, received D-panthenol 2% in one eye and artificial tear drops of similar composition not containing D-panthenol in the other eye, postoperatively, for 2 months. Patients were examined daily for 3 days after the procedure. They were then examined weekly for 1 month. An additional examination was made after 2 months. Visual acuity (Log MAR) was assessed at every visit. Rate of healing (% of covered area) and subjective sensation of discomfort (scale 0–5) were assessed in the 1st 3 visits. Residual manifest cylinder (D) (as a parameter of corneal irregularity) and corneal clarity (epithelial and stromal haze) were assessed from week 1 to month 2.

Results

During the first 3 days, both groups showed statistically nonsignificant (P > 0.05) results. From week 1 to month 2, eyes receiving D-panthenol showed better vision and less residual cylinder (P < 0.05) at week 1. For all other parameters, and at different examinations, both groups showed a statistically nonsignificant (P > 0.05) difference. Still, eyes receiving D-panthenol showed better values at the majority of the parameters tested.

Conclusion

D-Panthenol effect on corneal epithelial regeneration is of minimal clinical relevance. A different dosage and a larger sample of patients might reveal a statistical relevance. This trial is registered with https://doi.org/10.1186/ISRCTN81441126.