Comprehensive analysis of human keratinocyte and opportunistic pathogenic Candida interactions. Comprehensive analysis of human keratinocyte and opportunistic pathogenic Candida interactions

In recent years, microbiome studies revealed that Candida species are common colonisers of the human skin. The distribution of species however varies greatly. Although C. parapsilosis is more likely to resemble skin commensals, opinions are divided, and discrepancies are present regarding C. albicans, that is also often associated with cutaneous candidiasis. Therefore, we aimed to thoroughly assess the nature of skin epithelial cell - Candida interactions. To study species-specific host reponses, we examined phagocytosis, cytokine and metabolic responses in different keratinocytes (HaCaT, HPV-KER) along with host cell damage following fungal stimuli. These results suggest that C. albicans triggers an enhanced antifungal response, thus does not closely resembe skin commensals, like C. parapsilosis. Furthermore, HPV-KER might serve as a more applicable tool for studying keratinocyte antifungal responses. To rigorously examine yeast-keratinocyte interactions, we applied two distinct isolates of both C. albicans (SC5314, WO-1) and C. parapsilosis (GA1, CLIB214). Comparison of the two fungi’s virulence revealed that while C. albicans effectively adheres to human keratinocytes and causes subsequent damage, C. parapsilosis is unable to establish lasting physical contact and causes less harm. In terms of keratinocyte response, both cell lines showed significantly enhanced cellular (% phagocytosis), humoral (IL-6, IL-8) and metabolic responses (2-ketoglutaric acid, citric acid, threorine, hypotaurine) to C. albicans strains, while those towards C. parapsilosis remained relatively low or similar to the control condition. Under certain conditions strain preference was also detected. Of the two cell lines, HPV-KER was more sensitive, as besides interspecies differences, intraspecies differences were also measurable. Overall design: During the experiments C. albicans SC5314, WO-1 and C. parapsilosis GA1 and CLIB214 strains, and undifferentiated HPV-KER and HaCaT human keratinocyte cell lines were used. Then, for RNA-extraction, total of 3x 10^5 keratinocytes were seeded per well. Cells were infected with C. parapsilosis CLIB214 (MOI of 1:1) and C. albicans SC5314 (MOI of 1:25) for 12 hours.

近年来，微生物组研究表明，念珠菌属（Candida）物种是人类皮肤常见的定植菌。不过不同念珠菌物种的皮肤分布差异显著。尽管副光滑念珠菌（C. parapsilosis）更倾向于被认为是皮肤共生菌，但学界对此存在分歧；而对于常与皮肤念珠菌病相关的白念珠菌（C. albicans），相关认知也存在不一致之处。为此，本研究旨在全面评估皮肤上皮细胞与念珠菌的相互作用本质。为探究物种特异性宿主应答，本研究检测了不同角质形成细胞（keratinocyte）系HaCaT、HPV-KER在真菌刺激后的吞噬作用、细胞因子与代谢应答，以及宿主细胞损伤情况。研究结果显示，白念珠菌可触发更强的抗真菌应答，因此其与副光滑念珠菌这类皮肤共生菌的特性并不相似。此外，HPV-KER细胞系或许是研究角质形成细胞抗真菌应答的更适用模型。为严格探究酵母菌与角质形成细胞的相互作用，本研究使用了两株不同分离株的白念珠菌（SC5314、WO-1）与副光滑念珠菌（GA1、CLIB214）。对两种真菌的毒力比较结果显示：白念珠菌可有效黏附人类角质形成细胞并引发后续细胞损伤，而副光滑念珠菌无法建立持久的物理接触，仅造成轻微损伤。就角质形成细胞应答而言，两种细胞系对白念珠菌菌株均表现出显著增强的细胞层面（吞噬百分率）、体液层面（IL-6、IL-8）以及代谢层面（2-酮戊二酸、柠檬酸、苏氨酸、次牛磺酸）应答，而对副光滑念珠菌的应答则相对较低，或与对照组水平相近。在特定条件下，还检测到菌株偏好性差异。在两种细胞系中，HPV-KER的敏感性更高：不仅存在物种间应答差异，还可检测到种内差异。实验整体设计：本实验使用了白念珠菌SC5314、WO-1与副光滑念珠菌GA1、CLIB214菌株，以及未分化的人角质形成细胞系HPV-KER与HaCaT。随后，每孔接种3×10^5个角质形成细胞用于RNA提取。细胞分别以感染复数（MOI）1:1的副光滑念珠菌CLIB214，与MOI 1:25的白念珠菌SC5314感染12小时。