First Use of Optical Coherence Tomography on In Vivo Inflammatory Acne-Like Lesions: A Murine Model

Dynamic evaluation of pathological changes in a mouse acne model by optical imaging technology

Acne vulgaris is a disorder of the pilosebaceous unit that is primarily caused by hyperseborrhoea, colonization with Propionibacterium acnes, hyperkeratosis and an inflammatory response. Existing pharmacodynamic assessment methods primarily focus on a single causative factor at a certain time point, making it difficult to assess multiple factors simultaneously in real time. Therefore, it is crucial to establish a dynamic and nondestructive method for the assessment of acne in vivo. This study utilized four-dimensional optical imaging techniques to assess the pathogenic factors and pathological progression of acne. LSCI was employed to measure blood flow; TPEF was used to observe inflammatory changes (NAD(P)H) in epidermal granular layer cells and structural changes in collagen fibres in the dermal layer. Additionally, the dermatoscope was used to investigate the micro-characterization of the lesions. We observed that the epidermis in the lesion area was thickened, hair follicles were keratinized, and there was obvious inflammation and blood flow aggregation by optical imaging technology. Based on these findings, the pathological progression of this acne model could be divided into the inflammation phase, accompanied by bacterial colonization, and the reparative phase. These results provide a new perspective for the assessment of acne and offer an experimental basis for the selection of precise drugs for clinical use.

Dermoscopy, Reflectance Confocal Microscopy and Optical Coherence Tomography Features of Acne: A Systematic Review

Noninvasive imaging techniques have recently outlined precise microscopic features of acne elementary lesions and accurate quantifications for disease severity staging and therapeutical efficacy follow-up. The aim of this review is to systematically describe current applications of dermoscopy, reflectance confocal microscopy (RCM), and optical coherence tomography (OCT) in acne vulgaris assessment and management. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. We included studies conducted on human subjects with elementary lesions of acne vulgaris, reporting assessment of the lesions with dermoscopy, RCM, and/or OCT. At present there are few large studies regarding acne and noninvasive imaging techniques, representing the main limitation of this review. Clinical examination represents the first line in acne diagnosis and treatment. However, dermoscopy, RCM, and OCT are further tools that can improve acne classification, monitoring of treatment, and pathophysiologic characterization. In the near future, dermoscopy, RCM, and OCT could become routinely used for the evaluation of acne vulgaris to provide a deeper knowledge of the disease and to guide the clinician in the prescription of tailored treatment protocols based on each patient’s characteristics.

Skin Barriers in Dermal Drug Delivery: Which Barriers Have to Be Overcome and How Can We Measure Them?

Although, drugs are required in the various skin compartments such as viable epidermis, dermis, or hair follicles, to efficiently treat skin diseases, drug delivery into and across the skin is still challenging. An improved understanding of skin barrier physiology is mandatory to optimize drug penetration and permeation. The various barriers of the skin have to be known in detail, which means methods are needed to measure their functionality and outside-in or inside-out passage of molecules through the various barriers. In this review, we summarize our current knowledge about mechanical barriers, i.e., stratum corneum and tight junctions, in interfollicular epidermis, hair follicles and glands. Furthermore, we discuss the barrier properties of the basement membrane and dermal blood vessels. Barrier alterations found in skin of patients with atopic dermatitis are described. Finally, we critically compare the up-to-date applicability of several physical, biochemical and microscopic methods such as transepidermal water loss, impedance spectroscopy, Raman spectroscopy, immunohistochemical stainings, optical coherence microscopy and multiphoton microscopy to distinctly address the different barriers and to measure permeation through these barriers in vitro and in vivo.