@misc{10481/79476,
year = {2023},
url = {https://hdl.handle.net/10481/79476},
abstract = {Inflammatory bowel disease (IBD) is a chronic disease with increasing incidence and prevalence,
currently affecting millions of people worldwide, which can lead to an aggressive colitis-associated
cancer (CAC) with a poor prognosis. Its etiology seems to rely on the complex combination of
different factors, including environmental determinants, genetic predisposition, microbiota
imbalance, and mucosa immune defects. This compromises the intestinal epithelial barrier,
leading to an altered immune response characterized by excessive and sustained cytokine
production and immune cell recruitment and activation. Thus, the state of intestinal mucosal
tolerance, i.e. immunological unresponsiveness to innocuous food antigens and the commensal
microbiota, becomes disrupted. Understanding these mechanisms has potential translational
value for IBD therapy and management, as well as for preventing the development of CAC.
Human intestinal mesenchymal cells (iMCs) represent a heterogeneous population of various cell
types, such as fibroblasts, myofibroblasts, pericytes, smooth muscle cells and resident
mesenchymal stromal cells (MSCs), which reside in the subepithelial compartment where they
provide much of the structural framework of the intestine. However, iMCs also play important roles
regulating the homeostasis/maintenance of the epithelial barrier and promoting immunological
tolerance against commensal bacteria and food antigens. Moreover, recent investigations have
proposed that iMCs may play dual roles both inhibiting or supporting gut inflammation and injury
in IBD, as well as reducing or promoting tumor growth and metastasis, depending on their
response to inflammatory mediators and/or TLR agonists.
The study of the stromal compartment of tissues was pioneered by Owen and Friendenstein, who
discovered fibroblastic cells in the bone marrow with the capacity to give rise to bone, adipocytes
and hematopoiesis-supporting stroma. Such MSCs are defined by a set of criteria postulated by
the International Society for Cell Therapy (ISCT), and can be isolated from a variety of adult and
neonatal tissues. Importantly, cultured MSCs retain part of their in vivo characteristics and provide
a suitable model to analyze various aspects of stromal cells in health and disease. The design of
new therapies against IBD and CAC should contemplate the importance of iMCs both in the
homeostasis of the healthy intestine and the chronic inflammation even though further studies are
needed to fully understand their properties on tissue regeneration and immunomodulation.
In order to address this, we set the following objectives:
1. Isolation and characterization of the immunomodulatory and tissue regenerative
properties of intestinal MSCs (iMSCs) in vitro.
2. Analysis of the effect of iMSCs administration in dextran sulfate sodium (DSS)-induced
acute colitis in mice: evaluation of disease severity, immune responses, tissue
regeneration and microbiota composition. 3. Analysis of the effect of iMSCs administration on cancer progression in a model of colitisassociated
cancer: evaluation of tumor growth, immune responses, and microbiota
composition.
First, plastic-adherent iMCs were isolated from human intestinal resections and expanded in vitro.
We then confirmed their identity as iMSCs according to the definition by ISCT, i.e: (i) expression
of CD73, CD90, CD105, while lacking CD31, CD34 and CD45, and (ii) possessing the ability to
differentiate into adipocytes, chondroblasts and osteoblasts in vitro.
Then, we explored the immunomodulatory properties of iMSCs in vitro. Our data show that iMSCs
significantly repressed CD4+ and CD8+ T cell proliferation, partly through a indoleamine-2,3-
dioxygenase (IDO)-dependent mechanism. Furthermore, iMSCs reduced the LPS-mediated
induction of TNF-α in THP-1 macrophages, suggesting a polarization into anti-inflammatory M2
macrophages. In addition, isolated iMSCs enhanced wound closure in a scratch wound healing
assay, using human normal colon epithelial cells.
Second, we analyzed their properties in vivo in an experimental model of acute intestinal
inflammation induced by DSS in C57/bl6 mice, which displays human IBD-like features. One
single intraperitoneal injection of iMSCs significantly reduced the disease activity index (DAI),
ameliorated the histological damage of the colon and improved the integrity of the intestinal
epithelium. The anti-inflammatory effect exerted by iMSCs was associated with a reduced
expression of pro-inflammatory cytokines including TNF-α, IL-6 and IL-12, as well as of the
adhesion molecule ICAM-1 and iNOS, thus suggesting a M2-polarization of macrophages.
Interestingly, when the microbiota was analysed, the treated mice presented a higher species
richness (Chao1 index) and diversity (Shannon index), than the untreated colitic mice. Besides,
iMSCs modified the abundance of key phyla affected by the DSS, such as Proteobacteria and
Actinobacteria.
Finally, the iMSCs were evaluated in a murine model of CAC consisting of the injection
of azoxymethane (AOM) followed by three cycles of DSS to C57/bl6 mice. Two intraperitoneal
injections of iMSCs at the peaks of the two last DSS cycles significantly reduced colitis and the
associated intestinal tumor development. The iMSCs reduced the colonic expression of several
inflammatory mediators that drive CAC, including IL-6, TNF-α, IL-17/IL-23 and COX-2; the
activation of the signaling pathways of PI3K/AKT and IL-6/STAT3 as well as the levels of tumorpromoting
β-catenin). The iMSCs treatment also lowered the number of intestinal neutrophils and
eosinophils in comparison to CAC mice. As shown in the DSS model, iMSCs also decreased the
proportion of M1 macrophages, and partly restored the normal intestinal macrophage
differentiation. Regarding their effect on microbiota composition, iMSCs ameliorated the CACinduced
dysbiosis, restoring the OTUs and Shannon parameters and diminishing the alterations
in the relative abundance of Bacteroidetes and Verrucomicrobia.
In summary, our data show that human iMSCs isolated from the noninflamed intestine possess
potent tissue-regenerative and immunomodulatory capacities in vitro and in vivo, that could be
considered as key elements to ameliorate IBD severity and protect against CAC development.},
organization = {Tesis Univ. Granada.},
publisher = {Universidad de Granada},
title = {Therapeutic potential of intestinal mesenchymal stromal cells in inflammatory bowel disease and colorectal cancer},
author = {Hidalgo García, Laura},
}