Mitochondrial dysfunction in inflammatory bowel diseases
Mitochondria are important gatekeepers of intestinal epithelial cell homeostasis, and mitochondrial dysfunction is associated with the development of inflammatory bowel diseases. Increased mitochondrial fission is a novel feature associated with intestinal pathology, and our research explores the interplay between mitochondrial form and function and intestinal inflammation susceptibility.
Focus Group: Cell Stress in Intestinal Tissue Repair and Microbiome Homeostasis
Prof. Thaddeus Stappenbeck (Cleveland Clinic, Lerner Research Institute), Alumnus Hans Fischer Senior Fellow | Kaelin Smith (TUM), Doctoral Candidate
Host: Prof. Dirk Haller (TUM)
Mitochondria and intestinal diseases
Mitochondria are dynamic organelles that act as metabolic and signaling hubs that regulate various cellular processes such as energy production. Mitochondria do not always exist as just singular organelles, but also as a dynamic network whose components can physically and functionally interact. This mitochondrial network is continually changing to fulfill various cellular requirements. These mitochondrial networks can fuse together or separate via the processes of mitochondrial fusion and mitochondrial fission. Mitochondrial fusion facilitates the connection of neighboring mitochondria to create larger, elongated mitochondrial networks. This is useful when the cell has increased energy requirements and needs to increase surface area for ATP production. On the other hand, mitochondrial fission allows mitochondria to fragment from the network into smaller, separated mitochondria. This can be useful to segregate damaged components for recycling or to prepare for cellular division. These processes are tightly regulated, and a breakdown in either process can contribute toward disease susceptibility. Perturbations in mitochondrial fission and fusion have been linked with the development of multiple inflammatory pathologies [1].
The term inflammatory bowel diseases (IBD) refers to a group of chronic inflammatory diseases of the intestine, primarily Crohn’s disease and ulcerative colitis. Mitochondria are considered important gatekeepers of intestinal epithelial cell (IEC) homeostasis, and perturbations in mitochondrial function and metabolism have been implicated in the onset and course of IBD [2]. These mitochondrial defects include altered mitochondrial bioenergetics, an increase in mitochondrial stress response signaling, and an impaired proliferative and differentiation capacity of the intestine [3]. Colonic biopsy samples from IBD patients also show an increased presence of fragmented mitochondrial networks indicative of increased mitochondrial fission. This increased fission phenotype was also positively correlated with inflammation severity [4]. However, exactly how various mitochondrial morphologies and increased mitochondrial fission mechanistically link with IBD development has not been explored in depth. Therefore our research explores how mitochondrial network forms and functions affect intestinal disease susceptibility.
Mitochondrial networks in mouse models of inflammatory bowel diseases
The first aim of this project was to explore how mitochondrial networks differ in terms of shape, size, and localization in different models of intestinal inflammatory diseases. Immunofluorescence staining and confocal imaging was used to visualize mitochondrial structures in intestinal epithelial cells. Tissue sections were prepared from several IBD-relevant mouse models that recapitulate various aspects of human IBD. One of these mouse models is the metabolic injury mouse model (Hsp60flox/flox X VillinCreERT2-Tg X Il10-/-), where the mice develop an injury phenotype in the intestine following conditional deletion of the mitochondrial chaperone Hsp60. This tissue injury phenotype is accelerated when coupled with a full body IL10-deficiency, which increases susceptibility for colitis development [5]. In this model we found that intestinal injury is correlated with reduced mitochondrial mass in intestinal epithelial cells from the colon. Additionally, there is an increased presence of smaller, circular mitochondrial morphologies compared to controls (Fig. 1). This data shows that mitochondrial networks are altered across various IBD-relevant conditions.
Figure 1
Mitochondrial fission knockout via CRISPR-Cas9 approaches
The second aim of this project was to explore the role of mitochondrial fission in an in vitro cell culture-based setting. CRISPR-Cas9 based approaches were used to knock out (KO) dynamin-related protein 1 (Drp1), the main mitochondrial fission protein, in the Mode-K intestinal epithelial cell line (i.e., Drp1 KO Mode-K). While cellular morphology looked normal in the KO cell line, immunofluorescence staining shows that Drp1 loss is associated with increased presence of fused mitochondrial networks (particularly in the peri-nuclear region) compared to controls that contained a mixture of both fused and fragmented networks (Fig. 2). Additionally, Drp1 KO Mode-K cells also showed an increase in mitochondrial stress signaling. This data highlights Drp1 as an important regulator of mitochondrial network shape and function.
Generation of novel mouse models with mitochondrial perturbations
The third aim of this project was to develop and characterize two novel IBD mouse models with a Drp1 knockout in intestinal epithelial cells. These models allow examination of how Drp1-mediated mitochondrial fission contributes towards intestinal homeostasis and whether Drp1 knockout has any protective effects against IBD development. As increased mitochondrial fission is a feature found in IBD patient samples and IBD-relevant mouse models, inhibition of Drp1 could be a novel therapeutic strategy to prevent intestinal disease development. These models include one with a chronic loss of Drp1 in intestinal epithelial cells (Drp1flox/flox x VillinCre x Il10-/-) and one with an acute loss of Drp1 in intestinal epithelial cells (Drp1flox/flox x VillinCreERT2-Tg x Il10-/-). Both models have been successfully generated, and comprehensive characterization of these mouse models is still in progress. This ongoing characterization includes tissue histology analyses, mitochondrial morphology visualization, and assessment of mitochondrial stress and inflammation markers.
Figure 2
are shown with white arrows. Tom20 (green, mitochondria), DAPI (blue, nucleus), Actin (red, cytoskeleton). Scale: 25μm.
Future outlook
In the future, we plan to conduct high-resolution electron microscopy-based imaging to examine mitochondrial morphology at the ultrastructural level. Furthermore, it would be of great interest to examine mitochondrial form and function in alternative IBD-relevant models to more deeply understand how mitochondrial shape interplays with inflammation and intestinal epithelial properties. The full results of this study will be disseminated via conference contributions in 2026, and the full study will be submitted as a research publication in the second half of the year (manuscript pending).
The rates of IBD are rapidly rising in the Western world, and IBD has emerged as a chronic public health concern. The elucidation of the mechanisms that contribute toward disease pathogenesis is of critical importance to identify new intervention strategies and develop novel therapeutics for patients living with chronic intestinal diseases. In summary, mitochondria are important regulators of intestinal epithelial cell homeostasis, and mitochondrial dysfunction is a key feature of intestinal diseases. Mitochondrial fission and fusion are underexplored mechanisms that can provide insight into how the interplay between mitochondrial form and function mechanistically contribute toward diseases susceptibility.
[1]
D. M. McKay, N. L. Mancini, J. Shearer, and T. Shutt, “Perturbed mitochondrial dynamics, an emerging aspect of epithelial-microbe interactions,” American Journal of Physiology-Gastrointestinal and Liver Physiology, vol. 318, no. 4, pp. G748–G762, Apr. 2020, doi: 10.1152/ajpgi.00031.2020
[2]
E. Rath, A. Moschetta, and D. Haller, “Mitochondrial function — gatekeeper of intestinal epithelial cell homeostasis,” Nature Reviews Gastroenterology & Hepatology, vol. 15, no. 8, pp. 497–516, Aug. 2018, doi: 10.1038/s41575-018-0021-x
[3]
S. Khaloian et al., “Mitochondrial impairment drives intestinal stem cell transition into dysfunctional Paneth cells predicting Crohn’s disease recurrence,” Gut, vol. 69, no. 11, pp. 1939–1951, Feb. 2020, doi: 10.1136/gutjnl-2019-319514.
[4]
A. K. Chojnacki, S. Navaneetha Krishnan, H. Jijon, T. E. Shutt, P. Colarusso, and D. M. McKay, “Tissue imaging reveals disruption of epithelial mitochondrial networks and loss of mitochondria-associated cytochrome-C in inflamed human and murine colon,” Mitochondrion, vol. 68, pp. 44–59, Nov. 2022, doi: 10.1016/j.mito.2022.10.004
[5]
E. Urbauer et al., “Mitochondrial perturbation in the intestine causes microbiota-dependent injury and gene signatures discriminative of inflammatory disease,” Cell Host & Microbe, vol. 32, no. 8, pp. 1347-1364.e10, Jul. 2024, doi: 10.1016/j.chom.2024.06.013
Selected publications
- K.F. Smith, D. Aguanno, E. Urbauer, S.T. Espenschied, H. Sesaki, T.S. Stappenbeck and D. Haller, “Mitochondrial Networks are Differentially Altered in Models of Intestinal Injury and Disease,” United European Gastroenterology Journal, vol. 13, no. S8, Oct. 2025, [Abstract].