Skin as an endocrine organ: A narrative review

Cutaneous-immuno-neuro-endocrine (CINE) system: A complex enterprise transforming skin into a super organ

Skin is now emerging as a complex realm of three chief systems viz. immune system, nervous system, and endocrine system. The cells involved in their intricate crosstalk, namely native skin cells, intra-cutaneous immune cells and cutaneous sensory neurons have diverse origin and distinct functions. However, recent studies have explored their role beyond their pre-defined functional boundaries, such that the cells shun their traditional functions and adopt unconventional roles. For example, the native skin cells, apart from providing for basic structural framework of skin, also perform special immune functions and participate in extensive neuro-endocrine circuitry, which were traditionally designated as functions of cutaneous resident immune cells and sensory neurons respectively. At the cellular level, this unique collaboration is brought out by special molecules called neuromediators including neurotransmitters, neuropeptides, neurotrophins, neurohormones and cytokines/chemokines. While this intricate crosstalk is essential for maintaining cutaneous homeostasis, its disruption is seen in various cutaneous diseases. Recent study models have led to a paradigm shift in our understanding of pathophysiology of many such disorders. In this review, we have described in detail the interaction of immune cells with neurons and native skin cells, role of neuromediators, the endocrine aspect in skin and current understanding of cutaneous neuro-immuno-endocrine loop in one of the commonest skin diseases, psoriasis. An accurate knowledge of this unique crosstalk can prove crucial in understanding the pathophysiology of different skin diseases and allow for generation of targeted therapeutic modalities.

Psoriasis: What Is New in Markers of Disease Severity?

Introduction. Psoriasis is a chronic inflammatory skin disease and is the result of the interaction between numerous external and internal factors. Psoriasis presents a wide range of skin manifestations encompassing individual lesions varying from pinpoint to large plaques that can evolve into generalised forms. The lesions mirror the pathophysiological mechanisms involved in psoriasis pathogenesis, such as inflammation, dysregulation of immune response, uncontrolled proliferation of keratinocytes and angiogenesis. In this article, we present the latest advances achieved regarding markers that correlate with psoriasis severity. Material and method. We have performed a narrative review on markers of psoriasis severity, including articles published between March 2018-March 2023. Results. We have identified four categories of markers: inflammation markers, oxidative stress markers, hormonal markers and cancer-related markers. The main focus was on inflammation biomarkers, including immunomodulatory molecules, haematological parameters, inflammatory cells and costimulatory molecules. Conclusions. The analysed data indicate that markers associated with inflammation, oxidative stress and hormones, and cancer-related markers could be useful in assessing the severity of psoriasis. Nevertheless, additional research is required to ascertain the practical importance of these biomarkers in clinical settings.

Frontal Fibrosing Alopecia and Reproductive Health: Assessing the Role of Sex Hormones in Disease Development

Frontal Fibrosing Alopecia (FFA) is a distinctive form of cicatricial alopecia characterized by gradual hairline recession, predominantly affecting postmenopausal individuals, thus implying a potential hormonal origin. This narrative review, spanning 2000 to 2023, delves into PubMed literature, focusing on the menopausal and hormonal status of women with FFA. The objective is to unravel the intricate nature of FFA and its plausible associations with hormonal dysregulations in women. While menopause remains a pivotal demographic characteristic linked to FFA, existing data suggest that its hormonal imbalances may not fully account for the development of FFA. Conversely, substantial evidence indicates a strong association between a reduction in fertile years, particularly through surgical interventions leading to an abrupt hormonal imbalance, and FFA in women. Additionally, exposure to hormone replacement therapy or oral contraceptives has shown varying degrees of association with FFA. Gynecologists should maintain a heightened awareness regarding the ramifications of their interventions and their pivotal role in overseeing women's fertility, recognizing the potential influence on the progression of FFA. The recurrent theme of hormonal disruption strongly implies a causal connection between alterations in sex hormones and FFA in women. Nevertheless, this relationship's extent and underlying mechanisms remain subjects of ongoing debate.

A Systematic Review of Keratinocyte Secretions: A Regenerative Perspective

Cell regenerative therapy is a modern solution for difficult-to-heal wounds. Keratinocytes, the most common cell type in the skin, are difficult to obtain without the creation of another wound. Stem cell differentiation towards keratinocytes is a challenging process, and it is difficult to reproduce in chemically defined media. Nevertheless, a co-culture of keratinocytes with stem cells usually achieves efficient differentiation. This systematic review aims to identify the secretions of normal human keratinocytes reported in the literature and correlate them with the differentiation process. An online search revealed 338 references, of which 100 met the selection criteria. A total of 80 different keratinocyte secretions were reported, which can be grouped mainly into cytokines, growth factors, and antimicrobial peptides. The growth-factor group mostly affects stem cell differentiation into keratinocytes, especially epidermal growth factor and members of the transforming growth factor family. Nevertheless, the reported secretions reflected the nature of the involved studies, as most of them focused on keratinocyte interaction with inflammation. This review highlights the secretory function of keratinocytes, as well as the need for intense investigation to characterize these secretions and evaluate their regenerative capacities.