Generating hair follicle inductive dermal papillae cells from adipose derived mesenchymal stem cells

Master Thesis


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University of Cape Town

Current management options for cutaneous burn wounds, including split thickness skin grafts and cultured epithelial autografts, generate an epithelial barrier which lacks a dermal layer and skin adnexae including hair follicles and sebaceous glands. This results in a loss of pliability and contractures that cause functional and cosmetic impairment. Embryological hair follicle morphogenesis results from a complex series of mesenchymal-epithelial interactions and to date a method of generating de novo folliculogenesis from human cells has yet to be accomplished. Existing models rely on combining 'inductive’ dermal and 'receptive’ epithelial components and placing them within a suitable model. Epithelial cells are easily obtainable from skin biopsies therefore obtaining sufficient quantities of 'trichogenic’ dermal cells remains the most significant challenge of this approach. The main aim of this project is to contribute to the achievement of de novo folliculogenesis by generating dermal papillae (DP) like-spheroids using adipose derived mesenchymal stem cells (ASCs) that, when combined with responsive epithelial cells, would be capable of inducing hair follicle formation. ASCs were directed towards a hair follicle DP-like fate by culture using the hanging drop method and exposure to Wnt, mimicking signalling and mesenchymal condensation in embryological hair follicle induction. Gene expression analysis using RT-PCR showed that the DP-cell marker Versican is expressed at high levels in ASCs under routine culture conditions and the exposure of ASCs to Wnt results in a more than threefold increase in this expression. These results suggest that Wnt/β-catenin signalling may regulate DP cell aggregative growth through modifying versican expression possibly through binding of β-catenin to the TCF transcription factor complex. Culture of ASCs using the hanging drop method produces spheroids similar in size to human hair follicle DP. Histology of these spheroids demonstrates viable cells that flatten around the outside. The spheroids grow out when replated onto Matrigel in a 3D culture model and exhibit a morphology similar to that of primary hair follicle DP cells. Analysis of mRNA expression demonstrates that Versican expression is significantly upregulated in DP-like spheroids in the absence or presence of Wnt demonstrating that Versican may be responsible for both induction and maintenance of mesenchymal cell condensates. Alpha smooth muscle actin is expressed in low levels in ASC spheroids compared to ASCs in a monolayer and this may reflect a 'migratory’ myofibroblast like phenotype of ASCs in a monolayer similar to cells with the hair follicle dermal sheath. The addition of Wnt to ASC spheroids has no additional effect on Versican expression possibly reflecting a negative feedback loop resulting from high local concentrations of endogenous Wnt expression from ASCs. The results of this study show that spheroid cell culture and exposure to Wnt of ASCs results in cell clusters with similar morphology and gene expression to hair follicle DP cells. The novel method of DP-like cell generation described in this study makes use of cells that are readily obtainable from patients and require minimal time and manipulation in culture and therefore could potentially be rapidly translatable to clinical trials.