Ascorbic Acid Promotes the Stemness of Corneal Epithelial Stem/Progenitor Cells and Accelerates Epithelial Wound Healing in the Cornea

Abstract

High concentration of ascorbic acid (vitamin C) has been found in corneal epithelium of various species. However, the specific functions and mechanisms of ascorbic acid in the repair of corneal epithelium are not clear. In this study, it was found that ascorbic acid accelerates corneal epithelial wound healing in vivo in mouse. In addition, ascorbic acid enhanced the stemness of cultured mouse corneal epithelial stem/progenitor cells (TKE2) in vitro, as shown by elevated clone formation ability and increased expression of stemness markers (especially p63 and SOX2). The contribution of ascorbic acid on the stemness enhancement was not dependent on the promotion of Akt phosphorylation, as concluded by using Akt inhibitor, nor was the stemness found to be dependent on the regulation of oxidative stress, as seen by the use of two other antioxidants (GMEE and NAC). However, ascorbic acid was found to promote extracellular matrix (ECM) production, and by using two collagen synthesis inhibitors (AzC and CIS), the increased expression of p63 and SOX2 by ascorbic acid was decreased by around 50%, showing that the increased stemness by ascorbic acid can be attributed to its regulation of ECM components. Moreover, the expression of p63 and SOX2 was elevated when TKE2 cells were cultured on collagen I coated plates, a situation that mimics the in vivo situation as collagen I is the main component in the corneal stroma. This study shows direct therapeutic benefits of ascorbic acid on corneal epithelial wound healing and provides new insights into the mechanisms involved. Stem Cells Translational Medicine 2017;6:1356–1365

Differential distribution of the epigenetic marker 5‐hydroxymethylcytosine occurs in hair follicle stem cells during bulge activation

“…Moreover, Lameira et al showed that resveratrol can epigenetically alter 5‐hmC levels, and additional studies have linked resveratrol to stem cell proliferation and hair growth via the prostaglandin D2 pathway . Furthermore, ascorbic acid, a known promoter of epithelial stem cells, has also been shown to stimulate hair growth and alter 5‐hmC levels by modulating TET activity …”

“…5-hmC, 5-hydroxymethylcytosine; IHC, immunohistochemistry resveratrol can epigenetically alter 5-hmC levels, and additional studies have linked resveratrol to stem cell proliferation and hair growth via the prostaglandin D2 pathway [23][24][25]. Furthermore, ascorbic acid, a known promoter of epithelial stem cells, has also been shown to stimulate hair growth and alter 5-hmC levels by modulating TET activity 17,[26][27][28]. Using these agents known to modulate HF growth via epigenetic pathways, a subset of mouse BSCs in organ cultures underwent signs of activation, as indicated by Ki67 labeling.…”

Different Effects of Pro-Inflammatory Factors and Hyperosmotic Stress on Corneal Epithelial Stem/Progenitor Cells and Wound Healing in Mice

“…The mice corneal epithelial stem/progenitor cells used in this study have high expression levels of limbal progenitor cells markers ΔNp63 and importin 13 and have low expression levels of differentiated markers ck3/12 and involucrin, implying that these cells still retain stem cell properties. The TKE2 cells were cultured in keratinocyte serum‐free low‐Ca 2+ medium to maintain the undifferentiated state, and this cell line has already been characterized and used for the study of CESC and corneal wound healing in other reports . In addition, in order to validate our results from the TKE2 cells, we used primary cultured rabbit corneal epithelial cells for key experiments such as cell cycle and apoptosis detection.…”

“…that these cells still retain stem cell properties. The TKE2 cells were cultured in keratinocyte serum-free low-Ca 2+ medium to maintain the undifferentiated state, and this cell line has already been characterized and used for the study of CESC and corneal wound healing in other reports [40][41][42][43]. In addition, in order to validate our results from the TKE2 cells, we used primary cultured rabbit corneal epithelial cells for key experiments such as cell cycle and apoptosis detection.…”

Topical Ascorbate Administration in Severe Ocular Burns

“…Ascorbate is considered to be important with respect to wound healing and prevention of corneal ulceration [5]. After an ocular burn, the disposability of ascorbate in the aqueous humor and the cornea may be reduced for weeks [6].…”