Keratinocytes, a major cellular component of the epidermis, are responsible for restoring the epidermis after injury through a process termed epithelialization. This review will focus on the pivotal role of keratinocytes in epithelialization, including cellular processes and mechanisms of their regulation during re-epithelialization, and their cross talk with other cell types participating in wound healing. Discoveries in epidermal stem cells, keratinocyte immune function, and the role of the epidermis as an independent neuroendocrine organ will be reviewed. Novel mechanisms of gene expression regulation important for re-epithelialization, including microRNAs and histone modifications, will also be discussed. Epithelialization is an essential component of wound healing used as a defining parameter of a successful wound closure. A wound cannot be considered healed in the absence of re-epithelialization. The epithelialization process is impaired in all types of chronic wounds. A comprehensive understanding of the epithelialization process will ultimately lead to the development of novel therapeutic approaches to promote wound closure.

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Langerhans cells (LCs) are a specialized subset of epidermal dendritic cells. They represent one of the first cells of immunological barrier and play an important role during the inflammatory phase of acute wound healing. Despite considerable progress in our understanding of the immunopathology of diabetes mellitus and its associated co-morbidities such as diabetic foot ulcers (DFUs), considerable gaps in our knowledge exist. In this study, we utilized the human ex vivo wound model and confirmed the increased epidermal LCs at wound edges during early phases of wound healing. Next, we aimed to determine differences in quantity of LCs between normal human and diabetic foot skin and to learn if the presence of LCs correlates with the healing outcome in DFUs. We utilized immunofluorescence to detect CD207+ LCs in specimens from normal and diabetic foot skin and DFU wound edges. Specimens from DFUs were collected at the initial visit and 4 weeks at the time when the healing outcome was determined. DFUs that decreased in size by >50% were considered to be healing, while DFUs with a size reduction of <50% were considered non-healing. Quantitative assessment of LCs showed a higher number of LCs in healing when compared to non–healing DFU’s. Our findings provide evidence that LCs are present in higher number in diabetic feet than normal foot skin. Healing DFUs show a higher number of LCs compared to non-healing DFUs. These findings indicate that the epidermal immune barrier plays an important role in the DFU healing outcome and may offer new therapeutic avenues targeting LC in non-healing DFUs.

Acne vulgaris is a prevalent and non-discriminatory condition affecting individuals of all races and ethnicities. As people with skin of color make up a rapidly expanding segment of the US population, dermatologic care must evolve accordingly to address their distinct concerns. Patients with skin of color with acne can be particularly challenging, given their potential for cosmetically disturbing complications, including post-inflammatory hyperpigmentation and keloid development. A variety of treatments have been shown to be effective in preventing or treating these complications. Topical retinoids are considered first-line therapy for acne in patients of color; topical alternatives include azelaic acid, dapsone, and antimicrobials. Hydroquinone may be used in combating post-inflammatory hyperpigmentation, specifically. For more severe acne, oral agents, including oral antibiotics or isotretinoin, may be used. Most recently, various lasers and phototherapies have been suggested for their safety and efficacy in patients with skin of color with acne. Ultimately, recognizing the clinical and histologic differences, as well as the variations in treatment regimens for darker skin types will allow for better care and patient satisfaction.