P0038 Perianal Fistula Closure after Heterologous Mesenchymal Stem Cell Injections is Associated with Protein Levels indicating Lower Tissue Immune Infiltrate, Specific Proteins Involved in the Control of Apoptosis, and Probable Higher Tissues Remodeling and Proteasome Activity
Authors: Meuwis M A , Baiwir D , Fleron M , Mazzucchelli G , Boutaffala L , Reenaers C , Van Kemseke C , Vieujean S , Bettonville V , Briquet A , Lechanteur C , Coimbra Marques C , Louis E 
Published: January 2025

Abstract

Background
Perianal fistulae affects 30-34% of patients with Crohn’s Disease (CD)[1]. Scarce evidences are available on the perianal fistula pathophysiology. Bone marrow-derived Mesenchymal Stem Cells (bmMSCs) local injections have been found safe and efficient for 50% of CD patients included in a previous prospective monocentric study[2]. The present study aims at identifying potential proteins associated with fistulae closure following bmMSCs local injection, using the biological material collected during fistula tract curettage

Methods
In the prospective interventional uncontrolled study carried out at CHU of Liège (2019 - 2021), 16 CD have been treated and 10 curettage samples have been analyzed by label free proteomics using mass spectrometry technology[3]. Differential analysis comparing responders (R) with perianal fistula closure at W48 (n=5) with non-responders (NR), with absence of closure at any visit including W48, (n=5), identified specific proteomic profile changes, which were also evaluated by Gene Ontology analyses to identify biological processes, cell types and pathways associated with fistula closure.

Results
total of 1883 proteins were identified and the differential analysis revealed 48 proteins differentially distributed in R versus NR profiles. Only 18 were more abundant in R, among which the product of the STK4, PLP2, CYB5B and FLG genes, showing the strongest significant increases in R and therefore potential associations with fistula closure after bmMSCs injections. The fistula tract material of patients showing no closure (NR) reveal higher number of proteins, together with NR&gt;R relative abundances, associated with inflammatory and immune infiltrates, with chemokines, bacterial invasion. NR profiles show as well lower numbers and relative levels of proteins involved in wound healing and in matrix remodeling than in R (figures 1 and 2). Among the proteins, differentially distributed in R versus NR, specific pro-apoptotic (R&gt;NR) and anti-apoptotic proteins (NR&gt;R) could be highlighted, in addition to specific proteins acting upstream pathways involved in morphogenesis, carcinogenesis and fibrosis (HIPPO, MAPK, JAK-STAT pathways and TGF signaling).

Conclusion
Our data provide the first descriptive picture of proteins and likely process/pathways associated with fistula closure after bmMSCs treatment. While independent confirmations are required these preliminary results suggest that the apoptotic process, cell infiltrate degree and proteins involved in tissue remodelling and wound healing, already impacted in fistulae tracts before the bmMSCs injections might be important factors associated with fistula closure outcome in this trial.

References
[1]C. G. C. McGregor, R. Tandon, and A. Simmons, "Pathogenesis of Fistulating Crohn’s Disease: A Review," Cell. Mol. Gastroenterol. Hepatol., vol. 15, no. 1, pp. 1–11, 2023, doi: 10.1016/j.jcmgh.2022.09.011.
[2]C. Reenaers et al., "Clinical and MRI Evolution After Local Injection of Bone Marrow-Derived Mesenchymal Stem Cells in Perianal Fistulae in Crohn’s Disease: Results From a Prospective Monocentric Study," J. Crohn’s Colitis, vol. 17, no. 5, pp. 728–737, May 2023, doi: 10.1093/ecco-jcc/jjac192.
[3]A.-M. Merli et al., "Solute Carrier Family 12 Member 2 as a Proteomic and Histological Biomarker of Dysplasia and Neoplasia in Ulcerative Colitis," J. Crohn’s Colitis, vol. 15, no. 2, pp. 287–298, 2021, doi: 10.1093/ecco-jcc/jjaa168.