Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Biology and Biomedical Sciences: Immunology

Language

English (en)

Date of Award

1-1-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Thaddeus Stappenbeck

Abstract

Colonic injury and inflammation exhibit high morbidity and mortality in western society and are increasingly diagnosed in human patients. In many models of such gastrointestinal insults, prostaglandin endoperoxide synthetase 2: Ptgs2; cyclooxygenase 2) and its downstream synthetic products, most notably prostaglandin E2, support proliferation and modulate the inflammatory immune response, two functions involved in proper injury response. We identified a primary source of this mediator as a population of stromal cells constitutively expressing Ptgs2 that appear to be required in two different model injury systems: administration of dextran sodium sulfate: DSS) and colonic biopsy. The central role of Ptgs2-expressing cells in injury demonstrates the importance of understanding Ptgs2 regulation. We therefore created a robust in vitro system for studying the pathways and molecules involved by isolation of Ptgs2-expressing colonic stromal cells and identified the isolated lines as colonic mesenchymal stem cells: cMSCs). We then demonstrated the dominance of post-transcriptional regulation of Ptgs2 expression in cMSCs. Subsequent global gene array analysis comparing these cMSCs to a similar cell isolated from the bone marrow revealed a number of candidate genes with potential roles in post-transcriptional regulation of Ptgs2 expression. We determined that Fgf9 can regulate Ptgs2 through Fgf receptor expressed preferentially in cMSCs. Downstream of Fgf9, phosphorylation of Erk and increased abundance of mRNA binding protein CUGbp2 augments Ptgs2 expression. Furthermore, Fgf9 expression in the adult colonic epithelium ideally positions this growth factor to affect Ptgs2 expression in vivo. We also found that loss of insulin growth factor 2 binding protein 1: Igf2bp1 or Imp1) results in a decrease in Ptgs2 and confirmed the ability of Imp1 protein and Ptgs2 mRNA to interact in the cellular environment. Additionally, we discovered increased Imp1 expression in the colonic biopsy wound bed compared to normal mucosa and co-localization of Imp1 in wound bed Ptgs2-expressing cells. Overall, this work has uncovered multiple mechanisms involved in the complex post-transcriptional regulation of Ptgs2 in isolated stromal cells and demonstrated the role of these pathways in response to multiple forms of colonic injury.

Comments

Permanent URL: http://dx.doi.org/10.7936/K7Z60M1W

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