HaCaT cells are a spontaneously immortalized, aneuploid human keratinocyte line, noted for retaining differentiation potential in vitro—making them a reliable proxy for human skin studies. They have been leveraged in diverse experimental contexts :

1. Infection models : HaCaT cells serve as a robust “skin substrate” to study microbial colonization dynamics involving S. epidermidis, S. aureus, P. aeruginosa, and more. (more)
2. Immune modulation : Upon stimulation with sensitizers or irritants, HaCaT cells significantly upregulate interleukin‑8 (IL‑8) expression—a key inflammatory marker.
3. UVB response & microvesicle release : Exposure to UVB radiation triggers the release of keratinocyte-derived microvesicle particles (MVPs) that mediate systemic signaling—highlighting HaCaT’s utility in photobiology.
4. Receptor signaling studies : Experiments manipulating CXCR4 and cytokines (e.g., IL-22) in HaCaT cells elucidate pathways relevant to epidermal proliferation and inflammatory regulation.

Researchers have used HaCaT cells to explore transfection-based oncogenic transformation—for instance, PDGF-B expression increased fibroblast proliferation and drove tumorigenicity in mouse models.

Dermal fibroblasts play a structural and dynamic role in the dermis, synthesizing extracellular matrix components like collagen, laminin, and fibronectin that support wound healing and skin architecture.

These cells have been employed to :

1. Validate scaffolds and regenerative strategies for burn healing by restoring extracellular matrix using fibrin sealants and collagen constructs (see University College London research).
2. Facilitate iPSC development : Harvard Stem Cell researchers have reprogrammed fibroblasts into pluripotent states—correcting genetic disorders via homologous recombination in vivo.

Classic fibroblast lines like NIH‑3T3—mouse embryonic fibroblasts—have served as feeder layers for keratinocyte cultures since the 1970s, establishing a foundational basis for skin model development.

1. Skin barrier & infection studies : HaCaT is central to modeling pathogen-keratinocyte-microbiome interactions (e.g., S. aureus, P. aeruginosa).
2. Inflammatory modulation : IL‑8 dynamics in response to irritants/antigens (e.g., contact hypersensitivity models).
3. Photobiology and immunosuppression : UVB-induced MVPs and systemic signaling through PAFR and CaSR pathways.
4. Cancer and transformation : PDGF-B’s role in promoting fibroblast proliferation and tumor formation in HaCaT derivatives.
5. Wound regeneration : Strategies combining fibroblast scaffolds and growth factors for dermal repair; harnessing ECM dynamics.
6. Stem cell biology : Dermal fibroblast utility as reprogramming substrates for iPSC generation.