Igf2bp1 Is Required for Full Induction of Ptgs2 mRNA in Colonic Mesenchymal Stem Cells in Mice

Abstract

Background & Aims Prostaglandin-endoperoxide synthase (Ptgs)2 is an enzyme involved in prostaglandin production during the response to mucosal damage. Its expression is regulated, in part, by mRNA-binding proteins that control the stability of Ptgs2 mRNA. We used a precise system of colonic injury and repair to identify Ptgs2 mRNA-binding proteins. Methods We used endoscopy-guided mucosal excision to create focal injury sites in colons of mice. Wound beds from wild-type, Ptgs2−/−, Ptgs2+/−, and Myd88−/− mice were analyzed at 2-day intervals following injury for aspects of repair and Ptgs2 expression. We used cultured colonic mesenchymal stem cells (cMSCs) that express Ptgs2 to identify and analyze molecules that regulate Ptgs2 expression. Results Ptgs2−/− mice had defects in wound repair, validating the biopsy technique as a system to study the regulation of Ptgs2. Ptgs2+/− mice had similar defects in wound healing, so full induction of Ptgs2 is required for wound repair. In wild-type mice, levels of Ptgs2 mRNA increased significantly in the wound bed 2 and 4 days after injury; the highest levels of Ptgs2 were observed in cMSCs. In a functional small hairpin RNA knockdown screen, we identified Igf2bp1, a VICKZ mRNA-binding protein, as a regulator of Ptgs2 expression in cMSCs. Igf2bp1 also interacted physically with Ptgs2 mRNA. Igf2bp1 expression was induced exclusively in wound-bed cMSCs, and full induction of Ptgs2 and Igf2bp1 during repair required Myd88. Conclusions We identified Igf2bp1 as a regulator of Ptgs2 mRNA in mice. Igf2bp1 is required for full induction of Ptgs2 mRNA in cMSCs.

Mucosally transplanted mesenchymal stem cells stimulate intestinal healing by promoting angiogenesis

“…This was not an immediate consequence of injury, as α-SMA loss occurred 6 days after biopsy injury (14). In our previous study, coadministration of two stable prostaglandin analogs of PGE 2 and PGI 2 prevented loss of staining in the muscularis propria of mucosally injured Ptgs2 -/-mice (14). Here, we determined that PGI 2 was the critical prostaglandin for smooth muscle protection after mucosal injury.…”

“…We previously showed that colonic mucosal injury of Ptgs2 -/-mice led to penetrating ulcers, as highlighted by loss of α-smooth muscle actin (α-SMA [Acta2]) staining within the underlying muscularis propria (Figure 1, A and B). This was not an immediate consequence of injury, as α-SMA loss occurred 6 days after biopsy injury (14). In our previous study, coadministration of two stable prostaglandin analogs of PGE 2 and PGI 2 prevented loss of staining in the muscularis propria of mucosally injured Ptgs2 -/-mice (14).…”

“…We previously showed that Ptgs2 -/-mice lost α-SMA staining underlying wound beds at day 6 after injury (14). As α-SMA expression can be downregulated in myofibroblasts (48) or vascular cells (49) following inflammation, it is possible that smooth muscle cells in injured Ptgs2 -/-mice underwent dedifferentiation following injury.…”

“…Thus, the in vivo mechanisms of mucosal repair are tractable using this model. We previously found that focal injury induced by biopsy (biopsy injury) in prostaglandin-deficient mice leads to penetrating ulcers that develop around 6 days after the initial injury (14). As we ultimately wanted to use MSC transplantation to stimulate repair in this model, we first needed to determine the mechanism of penetrating ulcer formation.…”

Intestinal myofibroblast-specific Tpl2-Cox-2-PGE 2 pathway links innate sensing to epithelial homeostasis

“…We hypothesize that innate stimulation-driven Tpl2-mediated Cox-2-PGE 2 expression in IMFs is part of an on/off switch mechanism conditionally activated to support crypt function under emergency conditions enhancing stem/progenitor cell survival and/or proliferation. Relevantly, a PGE 2 -expressing population identified to be mesenchymal stem cells but not myofibroblasts (50) shows defective repositioning close to crypts in the rectum of DSS-treated Myd88 −/− mice but not altered Cox-2 expression (30). However, the exact relationship between this population, intestinal fibroblasts, and myofibroblasts is not completely clear (51).…”