The Inflammatory Response in the Murine Ovalbumin-Induced Skin Inflammation Model Is Robust Despite Major Gut Microbiota Differences.

Valid pre-clinical animal models are essential for effective drug development in inflammatory skin diseases like atopic dermatitis. Most murine models exhibit low-to-moderate inflammatory responses with significant variability, undermining their validity and contributing to high drug attrition rates. Previous studies showed that microbiota transfer and early-life microbial exposure affect inflammatory phenotypes and allergy development. This concept might extend to other pre-clinical inflammatory models. We tested the impact of different microbiotas on ovalbumin (OVA)-induced skin inflammation in mice, by using BALB/c substrains from different vendors. Additionally, germ-free mice were co-housed for 2 weeks with specific-pathogen-free (SPF) mice at 6 weeks of age, resulting in delayed gut colonization. Thereafter, mice were sensitized with OVA in aluminum hydroxide and challenged with OVA on the ear. Skin inflammation was assessed through ear cytokine and serum immunoglobulin E (IgE) levels. Different T cell populations were analyzed in the spleen and ear-draining lymph node with flow cytometry. Microbiota composition was analyzed via 16S rRNA sequencing. Despite substantial differences in microbiota composition as well as T cell proportion across vendors, similar inflammatory responses to OVA were observed. An early sterile environment resulted in elevated serum IgE and fewer T cells in ear-draining lymph nodes compared to SPF mice but did not affect ear tissue cytokines. These studies demonstrate that the OVA-induced skin inflammation model is robust to microbiota differences, enhancing reproducibility while highlighting persistent issues of variability and low effect size.