Abstract
Impaired healing of skin wounds is a significant clinical challenge. Hydrogels formulated from natural polysaccharides can provide protection and moisture to wounds. Extraction, formulation, and use of polysaccharides can be associated with environmental and ethical costs. Indigenous communities prepare polysaccharides to treat wounds, utilising intergenerational mōhiotanga (wisdom) on the symbiotic relationship between endemic plants and tangata (people) while protecting the taiao (environment). In Aotearoa New Zealand, mātauranga Māori (knowledge) and rongoā Māori (healing) recognise the therapeutic use of mamaku (Cyathea medullaris), an endemic tree fern. Mamaku mucilage has traditionally been used for wound healing and gastrointestinal issues, as well as a food source. This thesis aimed to elucidate the mechanistic healing properties of this traditional polysaccharide preparation in skin wound models, blending science and mātauranga Māori to advance transcultural research and indigenous hauora (well-being).
A literature review revealed a gap in integrating traditional knowledge into modern polysaccharide wound care research. Traditional practices, including harvesting methods, preparation rituals, and ecological insights, were at best acknowledged but at worst ignored in recent studies, with most using overcomplicated approaches that required extracted botanical polysaccharides to be refabricated with further active or stabilising agents. This understanding informed the methodological approach of this thesis, aiming to strengthen the integration of traditional medicine systems.
Mamaku fronds were seasonally harvested according to the maramataka (Māori lunar calendar) to enhance the mauri (life force) of the rongoā, then were traditionally prepared to form hydrogels. The mucilage contained approximately 10% polysaccharide, which was observed to be released with processing, and was found to be stable for three months with cold storage and three days under human physiological conditions.
Keratinocyte monolayers were shown to tolerate mamaku mucilage at up to 1% polysaccharide content. The polysaccharide preparation did not affect scratch wound closure or pro-inflammatory chemokine production under standard conditions, but increased proliferation (p < 0.05), differentiation, and tight junction levels in wounded keratinocytes. Further, in wounds stimulated with a pro-inflammatory cytokine cocktail, mamaku polysaccharide reduced cytokine and chemokine proliferation (p ≤ 0.05), without affecting the rate of closure. These results were consistent with alginate polysaccharide and hydrocortisone controls.
Keratinocyte layers cultured at the air-liquid interface were shown to tolerate up to 2% mamaku polysaccharide when applied topically (p > 0.05). When scratch wounds in this model were stimulated with cytokine cocktail, mamaku polysaccharide reduced cell death (p ≤ 0.05), and decreased cytokine, chemokine, and growth factor production (all p ≤ 0.05), but adversely affected wound closure (p ≤ 0.05), as observed for the alginate and hydrocortisone controls.
However, when applied to intact keratinocyte layers stimulated with cytokine cocktail, the mamaku mucilage reduced trans-epidermal leakage, cell death, and the production of cytokines and chemokines, while restoring keratinocyte proliferation, differentiation, and tight junctions (all p ≤ 0.05). Again, responses were similar to the alginate and hydrocortisone controls.
In summary, following traditional guidance, the mamaku mucilage was shown to alter keratinocyte production of molecules involved in skin inflammation and integrity, thus providing a potential mechanism by which rongoā mamaku promotes wound healing. Importantly, this study highlighted the valuable role that indigenous medicine systems can play in advancing wound care when indigenous knowledge is successfully integrated into scientific research.