Similarities in DSG1 and KRT3 Downregulation through Retinoic Acid Treatment and PAX6 Knockdown Related Expression Profiles: Does PAX6 Affect RA Signaling in Limbal Epithelial Cells?

Abstract

Congenital PAX6-aniridia is a rare panocular disease resulting from limbal stem cell deficiency. In PAX6-aniridia, the downregulation of the retinol-metabolizing enzymes ADH7 (All-trans-retinol dehydrogenase 7) and ALDH1A1/A3 (Retinal dehydrogenase 1, Aldehyde dehydrogenase family 1 member A3) have been described in limbal epithelial cells (LECs) and conjunctival epithelial cells. The aim of this study was to identify the role of retinol derivates in the differentiation of human LEC and its potential impact on aniridia-associated keratopathy development. Human LEC were isolated from healthy donor corneas and were cultured with retinol, retinoic acid, or pan-retinoic acid receptor antagonist (AGN 193109) acting on RARα, β, γ (NR1B1, NR1B2 NR1B3) or were cultured with pan-retinoid X receptor antagonist (UVI 3003) acting on RXR α, β, γ (retinoid X receptor, NR2B1, NR2B2, BR2B3). Using qPCR, differentiation marker and retinoid-/fatty acid metabolism-related mRNA expression was analysed. DSG1 (Desmoglein 1), KRT3 (Keratin 3), and SPINK7 (Serine Peptidase Inhibitor Kazal Type 7) mRNA expression was downregulated when retinoid derivates were used. AGN 193109 treatment led to the upregulation of ADH7, KRT3, and DSG1 mRNA expression and to the downregulation of KRT12 (Keratin 12) and KRT19 (Keratin 19) mRNA expression. Retinol and all-trans retinoic acid affect some transcripts of corneal LEC in a similar way to what has been observed in the LEC of PAX6-aniridia patients with the altered expression of differentiation markers. An elevated concentration of retinol derivatives in LEC or an altered response to retinoids may contribute to this pattern. These initial findings help to explain ocular surface epithelia differentiation disorders in PAX6-aniridia and should be investigated in patient cells or in cell models in the future in more detail.

PAX6 disease models for aniridia

“…[ 73 ] This model was further used to identify morphological and molecular alterations, such as impaired migration and ability to differentiate into corneal epithelial cells, as well as novel PAX6 downstream targets, for instance, ADH7, ALDH1A1 , and SPINK7 . [ 73 74 75 76 ] MEK/extracellular signal-regulated kinases (ERK) signaling pathway repressor drugs, duloxetine and ritanserin, have been recently tested on mutant LESCs and have shown to rescue PAX6 haploinsufficiency and restore PAX6 production. [ 77 78 ]…”

The Effect of Glaucoma Treatment on Aniridia-Associated Keratopathy (AAK) – A Report from the Homburg Register for Congenital Aniridia

“…Limbal stem cell insufficiency and altered ocular surface as well as a continuous inflammatory processes are discussed as the cause of the progression of keratopathy [17][18][19][20][21][22][23][24][25]. Therefore, there is a consensus among experts to use preservative-free preparations for topical therapy, if possible, in order to avoid aggravation of the inflammatory state by proinflammatory additives such as benzalkonium chloride [6][7][8]12].…”

Congenitalis aniridia – egy spektrumbetegség magyarországi adatai

“…A későbbi stádiumokban a keratopathia progrediál, és a szaruhártya centruma is érintetté válik és megvastagszik a pannusképződés és az ereződés következtében [4,10,11]. Emiatt a könnyfilm állandó instabilitása, valamint recidiváló szaruhártya-eróziók jelentkeznek, és fokozódó látásromlás jellemző a szaruhártya hegesedése miatt [4,[9][10][11][12][13][14][15][16]. Ugyanakkor érdekes módon az OSDIpontszám alapján 30 beteg (90,90%) került szárazszempanaszok tekintetében a normáltartományba, és súlyos szárazszem-betegséget az OSDI-kérdőív egy betegnél sem igazolt.…”