Bile acid cytotoxicity in human dermal fibroblasts: mechanistic insights into effluent-induced peristomal skin damage

Bile acids in intestinal effluent may play an underrecognized mechanistic role in peristomal skin injury, yet their direct effects on dermal fibroblasts—the stomal cells essential for wound repair—have not been defined. As amphipathic detergents, bile acids disrupt membrane integrity, alter intracellular signaling and promote cell death in epithelial cells. They are present in intestinal effluent along with digestive proteases that can contribute to peristomal skin damage. Our previous work demonstrated that bile acids, particularly chenodeoxycholic acid (CDCA), increase protease activity and cell death in colonic epithelial (T84) cells in a pH-dependent manner. These findings provided the rationale to interrogate whether dermal fibroblasts exhibit similar vulnerability or unique mechanistic responses, given their central role in maintaining skin integrity and orchestrating wound repair. We hypothesized that bile acids induce dose- and time-dependent cytotoxicity in primary human dermal fibroblasts, with CDCA causing the greatest loss of membrane integrity and viability. Primary normal human dermal fibroblasts (NHDF, passages 3–6) were treated with CDCA, ursodeoxycholic acid (UDCA), or lithocholic acid (LCA) at 50–500 µM for 0.5–24 h (0.1% DMSO control). LDH activity in conditioned media quantified membrane damage (U/L) and Annexin V-FITC/propidium iodide staining assessed apoptosis and necrosis via fluorescence microscopy and ImageJ analysis. Data from ≥3 independent experiments were analyzed by one- or two-way ANOVA with Tukey’s post-hoc test (α = 0.05). LDH activity increased in a dose- and time-dependent manner. At 50 µM, LDH release reached 29.3 ± 15.9 U/L (CDCA), 28.0 ± 5.7 U/L (UDCA), and 48.8 ± 12.1 U/L (LCA) after 2 h. At 100 µM, values rose to 483.5 ± 83.5 U/L (CDCA), 464.7 ± 45.7 U/L (UDCA), and 496.6 ± 33.8 U/L (LCA) (p < 0.01). Fibroblasts treated with bile acids lost the normal spindle shaped morphology with LCA eliciting the fastest response within 1 h. These were dose-dependent with higher concentrations (250–500 µM) causing complete detachment by 24 h. Annexin V/PI staining confirmed that cells treated with bile acids transitioned from early apoptosis at low concentrations to necrosis at higher doses and longer exposures. These findings demonstrate, for the first time, that human dermal fibroblasts undergo rapid and robust bile acid–induced injury through both apoptotic and necrotic pathways. The consistent, dose-dependent cytotoxicity across CDCA, UDCA, and LCA indicates that fibroblasts lack the differential tolerance observed in epithelial cells, suggesting a cell-type–specific mechanism of effluent-mediated skin damage. Morphologic disruption and complete detachment at higher concentrations further underscore the susceptibility of the dermal compartment to bile acid exposure. Collectively, these data provide a mechanistic framework linking effluent composition to peristomal skin breakdown and impaired wound repair and highlight the need for targeted protective strategies that mitigate bile acid–driven stomal toxicity in ostomy and cholestatic conditions. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.