Sebum plays a dual role in skin homeostasis, maintaining barrier function and providing antimicrobial defense. However, its dysregulation drives the pathophysiology of common skin diseases. This review explains that abnormal sebum secretion promotes acne vulgaris by inducing follicular occlusion and Cutibacterium acnes (C. acnes) proliferation, while altered composition impairs the epidermal barrier. Key factors such as high-glycemic diets, androgen fluctuations, and environmental conditions significantly influence sebaceous gland activity. The underlying molecular mechanisms involve inflammatory and hormonal pathways, including dysregulation of peroxisome proliferator-activated receptor gamma (PPARγ) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling. We conducted a systematic literature search using keywords related to sebum physiology and pathology. This review also discusses emerging therapeutic targets and the potential of advanced sebaceous gland models for future research. This synthesis provides a theoretical foundation for developing targeted interventions in dermatology and cosmetics.

To investigate the potential of recombinant protein disulfide isomerase (PDI) as a raw material for skin-repair cosmetics, an engineered PDI-producing strain was constructed using the Pichia pastoris X33 expression system. The target protein was obtained through methanol-induced expression and anion-exchange chromatography purification, and its cytotoxicity and pro-adhesive effects on human skin fibroblasts (HSFs) were evaluated. The results showed that the purified recombinant PDI protein had an apparent molecular weight of approximately 55.7 kDa. Treatment with 0.04–5 µmol/L recombinant PDI for 24 h did not affect cell viability. On culture surfaces coated with 62.5 nmol/L recombinant human fibronectin (rhFN) or 31.25 nmol/L recombinant human collagen (rhC), the addition of 250 nmol/L recombinant PDI increased the HSF adhesion area ratio to approximately 2.1-fold that of the rhFN-alone group (p < 0.0001) and 1.9-fold that of the rhC-alone group (p < 0.0001). Collectively, the recombinant PDI protein exhibits good biocompatibility and pro-adhesive activity, demonstrating its potential as a candidate raw material for skin-repair cosmetics.