Increased activity of MAPKAPK2 within mesenchymal cells as a target for inflammation associated fibrosis in Crohn's Disease

BACKGROUND

Mesenchymal stromal cells are suggested to play a critical role in the Crohn's Disease (CD) associated fibrosis. MAPKAPK2 (MK2) has emerged as a potential therapeutic target to reduce inflammation in CD. However, cell-specific pattern of pMK2 activation and its role in the CD associated fibrosis are unknown. The objectives of this study were to evaluate cell-specific changes in MK2 activity between predominantly inflammatory CD versus CD with fibrotic complication and define the role of stromal cell-specific MK2 activation in CD-associated fibrosis.

METHODS

CD tissue, CD tissue derived mesenchymal stromal cells known as myo-/fibroblasts (CD-MFs), fibroblast specific MK2 conditional KO mice were used.

RESULTS

We observed that in the inflamed area of predominantly inflammatory CD, high MK2 activity was equally distributed between mesenchymal and hematopoietic cells. By contrast, in CD with fibrotic complications, high MK2 activity was mostly associated with mesenchymal stromal cells. Using ex vivo CD tissue explants and IL-10KO murine colitis model, we demonstrated that pro-fibrotic responses are significantly reduced by treatment with the MK2 inhibitor PF-3644022. Inhibition of MK2 activity in primary cultures of CD-MFs significantly reduced basal and TGF-β1-induced profibrotic responses. Using fibroblast-specific MK2 knockout mice in chronic DSS colitis, we demonstrated that fibroblast intrinsic MK2 signaling is among the key processes involved in the chronic inflammation induced profibrotic responses.

CONCLUSIONS

Our data suggest that activation of MK2 within fibroblasts contributes to the chronic inflammation induced fibrosis in CD and that targeting MK2 has potential for the development of novel therapeutic approaches for fibrosis in CD.

MyD88-mediated signaling in myo-/fibroblasts is required for control of macrophage maturation under mucosal tolerance in the gut

Introduction

Colonic myo-/fibroblasts (MFs) are cells of mesenchymal origin in a healthy gut are among the key players in the mucosal tolerance that involve MF-restricted MyD88 signaling. MFs and macrophages interact in colonic tissue. However, the mechanisms of MF mediated regulation of macrophages under intestinal mucosal tolerance has emerging evidence. We hypothesized that MF-restricted MyD88 signaling regulates macrophage maturation under colonic mucosal tolerance.

Methods

RNAseq, qRT-PCR, H&E, and flow cytometry was used for analysis of colonic tissue/cell derived from B6ACTA2CreMyD88fl/fl, B6Col1a2CreMyD88fl/fl and B6RagCol1a2CreMyD88fl/fl MF-specific conditional KO mice.

Results

MF-specific deletion of MyD88 in vivo resulted in the development of microcolitis and was associated with dysbiotic decrease in Firmicutes to Bacteroidetes bacterial ratio, a hallmark of intestinal inflammation. This process was associated with the increase in colonic expression of genes linked to the inflammatory activity of myeloid cells and accumulation of immature monocyte-derived macrophages. In vitro deletion of MyD88 from MFs (isolated from MF-specific MyD88 conditional KO mice) resulted in changes of basal and TLR4 mediated pathways involved in myeloid cell migration/maturation and inflammation. Using MF-macrophage co-cultures we demonstrated the MF-restricted MyD88 signaling suppresses myeloid cell inflammatory activity.

Conclusion

Intrinsic MyD88 signaling within colonic mesenchymal cells is critical to control myeloid cell differentiation and inflammatory activity under mucosal tolerance in the gut.

Supported by CTSA/TL1 5TL1TR001440-04 UTMB Institute for Translational Science and R01 DK103150 National Institute of Diabetes and Digestive and Kidney Diseases.