Effects of selected plant materials on in vitro wound healing using cell culture model

Abstract

Since ancient times, wounds have been treated using plant based remedies. Of these remedies, Aloe species especially A. vera is probably the most prominent. Aloe vera is also the most studied of the Aloe genus in terms of wound healing efficacy. A. ferox is another aloe with known use as a wound healing remedy and with wound healing effects supported in literature. Recently, a hybrid of A. vera and A. ferox, called A. muthi-muthi, has been cultivated. Plants rich in bioactive phytochemicals are often consumed for their perceived health benefits. Herbal infusions, or “teas”, are often made from plants like Aspalathus linearis (rooibos) and Cyclopia spp. (honeybush). Although honeybush has been demonstrated to have health effects such as anti-tumour activity, the wound healing potential of this genus is mostly unknown. In order to investigate the in vitro wound healing effects of A. muthi-muthi gel and whole leaf material, as well as Cyclopia genistoides extracts (both crude extracts and fractions rich in benzophenones and xanthones respectively), an appropriate model needed to be selected. Human immortalised keratinocytes (HaCaT cells) serve as an analogue to rapidly proliferating human epidermis and a scratch assay using this cell line was used to simulate wound healing in vitro. Induced scratches served as simulated “wounds”. Wound closure was measured 24 h and 48 h after scratches into monolayers of HaCaT cells were induced. The closure rate was also subsequently determined. To determine whether the plant materials selected for this study exhibited cytotoxic effects, an methyl thiazolyl tetrazolium (MTT)-assay was performed prior to the scratch assays to determine cell viability after an exposure period of 48 h. From the results of the MTT-assays, no severe cytotoxic effects were observed in HaCaT cells exposed to all plant materials at all experimental concentrations. None of the Cyclopia genistoides extracts tested displayed any improvement in wound closure or closure rate. On the other hand, a statistically significant (p < 0.05) improvement in percentage wound closure and closure rate was observed in HaCaT cells treated with A. muthi-muthi gel, corresponding with what has been found in literature with A. vera and A. ferox. Contrary to the findings of the A. muthi-muthi gel, no improvement in wound closure and closure rate shown in HaCaT cells treated with A. muthi-muthi whole leaf was found compared to an untreated control. Subsequently, a migration assay was also performed on A. muthi-muthi gel using the CytoSelect™ 24-well migration assay kit. No improvement in HaCaT cell migration compared to an untreated control was observed, however.