Influence of Birch Bark Triterpenes on Keratinocytes and Fibroblasts from Diabetic and Nondiabetic Donors

Abstract

Impaired wound healing is one of the main risk factors associated with diabetes mellitus. Few options are available to treat diabetic wounds, and therefore efficient remedies are urgently needed. An interesting option might be an extract of birch bark (TE) that has been clinically proven to accelerate acute wound healing. We investigated the effects of TE and its main components betulin and lupeol in cultured normal keratinocytes and dermal fibroblasts from diabetic and nondiabetic donors. These in vitro models can provide insights into possible beneficial effects in wound healing. TE and betulin treatment led to increased mRNA levels of chemokines, pro-inflammatory cytokines, and mediators important in wound healing, e.g., IL-6, TNFα, IL-8, and RANTES. We observed a pronounced upregulation of MIF, IL-8, and RANTES on the protein level. Furthermore, a shape change of the actin cytoskeleton was seen in keratinocytes and fibroblasts, and the Rho-GTPases and p38-MAPK were found to be activated in keratinocytes. On the basis of our results, TE is worthy of further study as a potential option to influence wound-healing processes under diabetic conditions. These first insights need to be confirmed by clinical studies with diabetic patients.

Comparison of In-Vitro and Ex-Vivo Wound Healing Assays for the Investigation of Diabetic Wound Healing and Demonstration of a Beneficial Effect of a Triterpene Extract

“…As the major second type of cells in the skin is fibroblasts, we tested whether TE might induce the expression of cytokines in fibroblasts under different glucose conditions. We investigated cytokines which have previously been shown to be induced by TE in fibroblasts under normal culture conditions [30] and which are important for wound healing[31]. We observed a significant increase of IL-6, IL-8, IL-1 ß, and CCL-2 expression in fibroblasts under various glucose concentrations (Table 2).…”

“…As we knew about the beneficial effect of TE in-vivo and ex-vivo under euglycaemic conditions [22–24] and its effect on cytokine production and cytoskeleton in diabetic keratinocytes and fibroblasts [30] and because triterpenes are known to have beneficial effects in diabetes[40], we used TE as a test substance in our various in-vitro and ex-vivo models. Interestingly, it only showed a positive effect in the ex-vivo model.…”

Human α defensins promote the expression of the inflammatory cytokine interleukin‐8 under high‐glucose conditions: Novel insights into the poor healing of diabetic foot ulcers

“…A previous study showed that IL‐8 was increased in diabetic wounds and that baseline levels of the IL‐8 mRNA were elevated in human dermal fibroblasts from diabetic donors compared with that from nondiabetic donors . Thus, determine whether IL‐8 was highly expressed in diabetic wound exudates, four exudate samples were collected with DFUs, and the amount of IL‐8 was quantified by ELISA.…”

“…Base on the effects of IL‐8 in the chemotaxis of neutrophils and the recruitment of neutrophils on the upregulation and overexpression of several α defensins, we hypothesized that α defensins may be involved in IL‐8 production. As resident cells of the skin, fibroblasts are essential for wound healing; however, the roles of fibroblasts in pathological functions in diabetic wounds remain largely unclear.…”

“…During injury and infection, defensins and related antimicrobial peptides, which are widely expressed, play important roles in innate immunity . For example, recruited neutrophils upregulate and overexpress several α defensins, which protect the skin and subcutaneous tissue against diverse microorganisms . In addition to their main function of killing invader microorganisms directly, defensins also play diverse roles in wound healing.…”