Acute Graft versus Host Disease (aGvHD) is seen in recipients of allogeneic hematopoietic stem cell transplantation (Allo-

HSCT) and causes up to 50% morbidity and mortality by affecting the skin, intestinal system and liver. aGvHD is treated

with immune suppressing steroids, which is succesful in half of the patients. Patients who are steroid resistant require

secondary treatments, that may be effective, but are accompanied by side effects and lowering the dose of these

treatments to prevent side effects results in progression of GvHD and increased mortality. Bone marrow mesenchymal

stem cells (BM-MSC) are effective in the treatment of steroid resistant aGvHD due to their immune modulatory properties

and are used as a last resort. There is no appropriate aGvHD model available therefore, we aim here to simultaneously

develop two completely different aGvHD models. We plan to develop 1) an in vivo aGvHD model, using immune deficient

mice that are treated with reduced intensity chemotherapy, which requires less mice, in stead of the current murine aGvHD

models that require high level chemotherapy and are associated with high mortality, and 2) a completely novel in vitro

“aGvHD-in-a-dish” model, using healthy intestinal organoids (colonoids). Our aim is to develop an in vitro a GvHD model

that closely resembles the in vivo aGvHD model and can therefore be used in stead of the animal model for future aGvHD

research.

Tissue damage caused by chemotherapy and donor T cell activation plays an important role in the development of

intestinal aGvHD. Treatment strategies should focus on repair of the tissue damage and suppression of T cells. Intestinal

mesenchymal stem cells (I-MSCs) are important factors contributing to homeostasis of the intestinal niche. The

therapeutic effects of I-MCs for the treatment of aGvHD have never been assessed. Since I-MSCs have an epigenetic

memory belonging to the intestine, these cells have the possibility to display superior effects in the treatment of intestinal

aGvHD in comparison to MSCs derived from other tissues.

MSCs in our in vivo and in vitro aGvHD models and compare these directly to the effects of BM-MSCs.

Therefore, here we aim to assess the therapeutic effects of I-

Colonoids are among the first organoids developed and have been used to assess new treatment options, drug dose and

toxicity testing for a range of bowel diseases. Here we would like to induce aGvHD in the colonoids, compare the model

with our in vivo model and assess the regenerative potential and/or immune modulatory properties of IMCs in this model.

In summary, we plan to 1) develop an in vivo aGvHD model using an immune deficient mouse model and a low

chemotherapy regime; 2) develop an in vitro aGvHD model using healthy intestinal organoids; 3) assess the differentiation

and regerative potential of IMCs and compare these with BM-MSCs; 4) compare the migratory, regenerative and immune

modulatory properties of IMCs and BM-MSCs in the in vivo aGvHD mouse model; and 5) compare the immune modulatory

effects of IMCs and BM-MSCs in the in vitro intestinal organoid aGvHD model. This will allow us to study aGvHD within

the scope of this project and in future collaborations with other researchers and to test new treatment options in our novel

aGvHD models that require less mice and can serve as a base for future studies.

Furthermore, because of the similarities to the human situation, the model can be used for personalized medicine: in order to assess the aGvHD risk related to a treatment, organoids can be made from bowel biopsies and co-cultured with donor- derived T-cells. As such the model has potential to serve as a pre-transplant risk assessment.