Maeva, Anna; (2024) Novel Multimodal Analysis of Skin Collagen Changes in IPL and Ageing. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis aims to explore the impacts of direct Ultra violet (UV) light exposure (mainly Intense Pulse Light) on the properties of type I and type III collagen in tissue as well as the natural ageing process of collagen fibrils in normal human tissue when it is naturally exposed to external and internal factors. Various models of different complexity were used in the study. Collagen fibrils were first analysed on a nano, micro, and macroscale, to ascertain the alignment and material characteristics of rat tail collagen fibres. These fibres were then exposed to increasing levels of Intense Pulse Light (IPL) radiation used clinically for photo-rejuvenation. It was found that increased irradiation was proportional to the disorder and degradation of the collagen sheets both on a qualitative and qualitative approach. This approach was then moved into a more complex EpiSkin model which was impregnated with MG-63 cells. The same level of irradiation exposure proved that as a result of exposure, especially at high levels where gelatinization occurred, cells were no longer able to grow at the same rate, relative to the control sample. A porcine model was subsequently applied ex-vivo due to its similarity in many dermatological characteristics to human skin. Porcine models were irradiated at a low, medium and high irradiation at 1x, 3x, and 10x. These samples were quantitatively observed using polarized microscopy and atomic force microscopy (AFM). They were also qualitatively analysed using AFM mechanics and scanning acoustic microscopy (SAM). Increased levels of irradiation showed increased gelatinization, increased Young’s modulus, decreased attenuation and speed of sound as well as a high degree of de-banding and disorganization. As a result of these studies, ex-vivo skin biopsies from 40 female patients were examined from the mammary tissue as well as the cheek to look at the mechanical properties of collagen fibrils as a result of natural ageing. The same technique was used utilizing both a qualitative and quantitative approach as that of the porcine samples but this time incorporating pixel analysis via quantitative-nano histology. The results were in line with previously observed. The older samples showed visible signs of ageing with loss 2 de-banding, increased porosity, increased Young’s modulus and speed of sound attenuation. Finally, the suppression of inflammatory processes was explored in elderly male patients and its effect on collagen fibril formation, an integral part of immune health which deteriorates with age. A p38 MAK suppressed pathway drug was used for 4 days which resulted in mild increase in the order and stability of collagen, which in the short term was an unexpected, albeit positive, result, given the turnover of cells in the tissue. The findings of this thesis demonstrate multi-modal analysis for collagen damage and clearly demonstrate the potential short-term effect of IPL, inflammation and ageing on human skin. It was found that IPL irradiation showed damaging effects on both rat tail collagen molecules and basic rat tail collagen scaffolds, affecting secondary and tertiary structure. IPL also played a role in changing the way cells behaved in more advance collagen scaffolds which lead to in-vitro results from porcine models showing severe damage to collagen structure with increasing radiation levels. These results, when compared to natural ageing of human skin tissue showed resemblance to natural ageing and the formation of AGE (Advanced Glycation End Products).

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