The effect of pH on cell viability, cell migration, cell proliferation, wound closure, and wound reepithelialization: In vitro and in vivo study

Abstract

Wound microenvironment plays a major role in the process of wound healing. It contains various external and internal factors that participate in wound pathophysiology. The pH is an important factor that influences wound healing by changing throughout the healing process. Several previous studies have investigated the role of pH in relation to pathogens but studies concentrating on the effects of pH on wound healing itself are inconclusive. The purpose of this study was to comprehensively and in a controlled fashion investigate the effect of pH on wound healing by studying its effect on human primary keratinocyte and fibroblast function in vitro and on wound healing in vivo. In vitro, primary human keratinocytes and fibroblasts were cultured in different levels of pH (5.5-12.5) and the effect on cell viability, proliferation, and migration was studied. A rat full-thickness wound model was used to investigate the effect of pH (5.5-9.5) on wound healing in vivo. The effect of pH on inflammation was monitored by measuring IL-1 α concentrations from wounds and cell cultures exposed to different pH environments. Our results showed that both skin cell types tolerated wide range of pH very well. They further demonstrated that both acidic and alkaline environments decelerated cell migration in comparison to neutral environments and interestingly alkaline conditions significantly enhanced cell proliferation. Results from the in vivo experiments indicated that a prolonged, strongly acidic wound environment prevents both wound closure and reepithelialization while a prolonged alkaline environment did not have any negative impact on wound closure or reepithelialization. Separately, both in vitro and in vivo studies showed that prolonged acidic conditions significantly increased the expression of IL-1 α in fibroblast cultures and in wound fluid, whereas prolonged alkaline conditions did not result in elevated amounts of IL-1 α.

Human saliva stimulates skin and oral wound healing in vitro

“…However, it must also be considered that cytotoxic proteins such as LL37, as mentioned above, are also present in saliva, indicating that a delicate balance exists between mitogens and antimicrobial proteins (Boink et al, 2017). It has been shown that a prolonged acidic wound environment can prevent wound closure and re-epithelialization (Kruse et al, 2017). Even though pH values of saliva can differ between donors, pooled saliva results in batches within the pH range (6.5 to 8.5) that have been shown to be welltolerated for keratinocyte proliferation (Sharpe, Harris, Jubin, Bainbridge, & Jordan, 2009).…”

The effect of cell density, proximity, and time on the cytotoxicity of magnesium and galvanically coupled magnesium–titanium particles in vitro

“…Although the pH did increase with the increase of particle concentrations, the pH did not vary over a wide range, and stayed between 7.4 and 9.1. 27,28 Just based on the pH changes alone, cells should have proliferated more at low particle concentrations due to slight pH increase (pH up to 8.0), compared to control. Although Mg-Ti sacrificed more cells than Mg, there was no difference in pH measurements between Mg and Mg-Ti.…”

Bioinorganics and Wound Healing

“…In contradiction to the animal and clinical studies, Kruse et al have shown using titanium chambers implanted in rats that contain culture medium buffered at different pH, which prolonged exposure of the wound to an acidic environment prevents wound closure and re‐epithelialization, whereas an alkaline environment did not have a negative impact on wound closure or re‐epithelialization when compared to physiological pH. This suggests that a temporary exposure to acidic conditions is more beneficial to heeling than full time exposure and that on a term exposure to an alkaline pH (8.5) would be beneficial for wound healing.…”

“…It as demonstrate in an in vitro scratch wound model that a pH increase from 7.4 to 8.4 causes a decrease in fibroblast proliferation and migration . In contrast, it was shown that alkaline pH (pH = 8.5) could increase proliferation while decreasing the migration . pH also affects keratinocyte behavior; it has been shown that lowering the pH was deleterious to the cells for both proliferation and migration .…”

“…pH also affects keratinocyte behavior; it has been shown that lowering the pH was deleterious to the cells for both proliferation and migration . Proliferation was found to be optimal in slightly alkaline environment, but migration decreases in both acidic and alkaline environments …”