Stefania Briganti

The sebaceous gland (SG) is a highly dynamic skin appendage that plays a central role in maintaining skin homeostasis through lipid production, immune modulation, and interactions with the skin microbiome. Dysregulation of SG function is implicated in several dermatological disorders, including acne and other inflammatory skin diseases. Over the past decades, a wide range of experimental models has been developed to investigate SG biology and pathology. These include in vivo animal models, ex vivo human skin explants, primary sebocyte cultures, and immortalized sebocyte cell lines, each offering distinct advantages and limitations. More recently, significant progress has been made in the development of advanced three-dimensional (3D) models of sebaceous gland biology, including sebocyte spheroids, SG organoids, human skin equivalents containing sebaceous components, and organotypic co-culture models, which better recapitulate the structural and functional complexity of SGs. In particular, the emergence of SG organoids derived from adult or pluripotent stem cells represents a breakthrough, enabling the study of sebocyte differentiation, lipid metabolism, and cell–cell interactions in a physiologically relevant context. Despite these advances, current models still face important challenges, including incomplete cellular maturation, limited representation of the immune and vascular components, and insufficient modeling of the native skin microenvironment. Future developments integrating bioengineering approaches, microfluidic platforms, and multi-cellular systems are expected to further enhance model complexity and translational relevance. This review summarizes current knowledge on experimental models developed to study SG and sebocyte physiology and pathology.

Melanoma is the deadliest form of skin cancer, characterized by high metastatic potential and intrinsic heterogeneity. In addition to genetic mutations such as BRAF^V600E^ and NRAS, lipid metabolic reprogramming has emerged as a critical factor in tumor progression and therapy resistance. Lipid metabolism supports melanoma cell survival, phenotypic switching, immune evasion, and resistance to targeted therapies and immunotherapy, while also modulating susceptibility to ferroptosis. This review summarizes current knowledge on lipid dysregulation in melanoma, highlighting alterations in fatty acid synthesis, desaturation, uptake, storage, and oxidation, as well as changes in phospholipids, sphingolipids, cholesterol, and bioactive lipid mediators. These lipid pathways are tightly regulated by oncogenic signaling networks, including MAPK and PI3K–AKT–mTOR pathways, and are influenced by tumor microenvironmental stressors such as hypoxia and nutrient limitation. Advances in lipidomics technologies, particularly mass spectrometry-based approaches, have enabled comprehensive profiling of lipid alterations at bulk, spatial, and single-cell levels, offering new opportunities for biomarker discovery and therapeutic stratification. Targeting lipid metabolic vulnerabilities represents a promising strategy to improve melanoma diagnosis, prognosis, and treatment efficacy.

Skin pigmentation results from complex cellular interactions and is influenced by genetic, environmental, and metabolic factors. Emerging evidence highlights the multiple pathways by which lipids regulate melanogenesis and points to lipid metabolism and signaling as key players in this process. Lipidomics is a high-throughput omics approach that enables detailed characterization of lipid profiles, thus representing a valid tool for evaluating skin lipid functional role in both physiological melanogenesis and pigmentary disorders. The use of lipidomics to gain a deeper comprehension of the role of lipids in skin pigmentation is still an evolving field, but it has allowed the identification of significant lipid dysregulation in several pigmentary pathologies. This review summarizes the current knowledge on the involvement of lipids in skin pigmentation, focusing on lipid profile alterations described in hyper- and hypopigmentary disorders such as post-inflammatory hyperpigmentation, melasma, solar lentigo, and vitiligo. Lipidomic profiling reveals disease-specific alterations supporting the pivotal role of lipid signaling in the physiopathological mechanisms of melanogenesis. These findings provide insights into disease pathogenesis and show promise for the discovery of biomarkers and innovative therapeutic strategies for pigmentary disorders.

The sebaceous gland (SG) is an integral part of the pilosebaceous unit and is a very active and dynamic organ that contributes significantly to the maintenance of skin homeostasis. In addition to its primary role in sebum production, the SG is involved in the maintenance of skin barrier function, local endocrine/neuroendocrine function, the innate immune response, and the regulation of skin bacterial colonization. Structural and functional alterations of SGs leading to the dysregulation of sebum production/composition and immune response may contribute to the pathogenesis of inflammatory dermatoses. This review summarises the current knowledge on the contribution of SGs to the pathogenesis of common inflammatory skin diseases. These findings are crucial for the development of more effective therapeutic strategies for the treatment of inflammatory dermatoses.

Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor expressed in many tissues, including skin, where it is essential for maintaining skin barrier permeability, regulating cell proliferation/differentiation, and modulating antioxidant and inflammatory responses upon ligand binding. Therefore, PPARγ activation has important implications for skin homeostasis. Over the past 20 years, with increasing interest in the role of PPARs in skin physiopathology, considerable effort has been devoted to the development of PPARγ ligands as a therapeutic option for skin inflammatory disorders. In addition, PPARγ also regulates sebocyte differentiation and lipid production, making it a potential target for inflammatory sebaceous disorders such as acne. A large number of studies suggest that PPARγ also acts as a skin tumor suppressor in both melanoma and non-melanoma skin cancers, but its role in tumorigenesis remains controversial. In this review, we have summarized the current state of research into the role of PPARγ in skin health and disease and how this may provide a starting point for the development of more potent and selective PPARγ ligands with a low toxicity profile, thereby reducing unwanted side effects.

Glucocorticoids (GCs) are commonly used in the treatment of inflammatory skin diseases, although the balance between therapeutic benefits and side effects is still crucial in clinical practice. One of the major and well-known adverse effects of topical GCs is cutaneous atrophy, which seems to be related to the activation of the glucorticoid receptor (GR) genomic pathway. Dissociating anti-inflammatory activity from atrophogenicity represents an important goal to achieve, in order to avoid side effects on keratinocytes and fibroblasts, known target cells of GC action. To this end, we evaluated the biological activity and safety profile of two novel chemical compounds, DE.303 and KL.202, developed as non-transcriptionally acting GR ligands. In primary keratinocytes, both compounds demonstrated anti-inflammatory properties inhibiting NF-κB activity, downregulating inflammatory cytokine release and interfering with pivotal signaling pathways involved in the inflammatory process. Of note, these beneficial actions were not associated with GC-related atrophic effects: treatments of primary keratinocytes and fibroblasts with DE.303 and KL.202 did not induce, contrarily to dexamethasone—a known potent GC—alterations in extracellular matrix components and lipid synthesis, thus confirming their safety profile. These data provide the basis for evaluating these compounds as effective alternatives to the currently used GCs in managing inflammatory skin diseases.

The endocannabinoid system regulates physiological processes, and the modulation of endogenous endocannabinoid (eCB) levels is an attractive tool to contrast the development of pathological skin conditions including cancers. Inhibiting FAAH (fatty acid amide hydrolase), the degradation enzyme of the endocannabinoid anandamide (AEA) leads to the increase in AEA levels, thus enhancing its biological effects. Here, we evaluated the anticancer property of the FAAH inhibitor URB597, investigating its potential to counteract epithelial-to-mesenchymal transition (EMT), a process crucially involved in tumor progression. The effects of the compound were determined in primary human keratinocytes, ex vivo skin explants, and the squamous carcinoma cell line A431. Our results demonstrate that URB597 is able to hinder the EMT process by downregulating mesenchymal markers and reducing migratory potential. These effects are associated with the dampening of the AKT/STAT3 signal pathways and reduced release of pro-inflammatory cytokines and tumorigenic lipid species. The ability of URB597 to contrast the EMT process provides insight into effective approaches that may also include the use of FAAH inhibitors for the treatment of skin cancers.

Cutaneous squamous cell carcinoma (cSCC) is the most common UV-induced keratinocyte-derived cancer, and its progression is characterized by the epithelial–mesenchymal transition (EMT) process. We previously demonstrated that PPARγ activation by 2,4,6-octatrienoic acid (Octa) prevents cutaneous UV damage. We investigated the possible role of the PPARγ activators Octa and the new compound (2Z,4E,6E)-2-methoxyocta-2,4,6-trienoic acid (A02) in targeting keratinocyte-derived skin cancer. Like Octa, A02 exerted a protective effect against UVB-induced oxidative stress and DNA damage in NHKs. In the squamous cell carcinoma A431 cells, A02 inhibited cell proliferation and increased differentiation markers’ expression. Moreover, Octa and even more A02 counteracted the TGF-β1-dependent increase in mesenchymal markers, intracellular ROS, the activation of EMT-related signal transduction pathways, and cells’ migratory capacity. Both compounds, especially A02, counterbalanced the TGF-β1-induced cell membrane lipid remodeling and the release of bioactive lipids involved in EMT. In vivo experiments on a murine model useful to study cell proliferation in adult animals showed the reduction of areas characterized by active cell proliferation in response to A02 topical treatment. In conclusion, targeting PPARγ may be useful for the prevention and treatment of keratinocyte-derived skin cancer.