STEM study - Specific Tissue Engineering in Medicine

The gastrointestinal mucosa has an amazing regenerative capacity, enabling
rapid restoration of its physiological functions following injury. The ability
to do this resides within the epithelial stem cells located in the bottom of
the gastrointestinal epithelial units. Recent advances towards isolation and
characterization of epithelial stem cells made it possible to explore
therapeutic approaches based on tissue engineering for gastrointestinal
epithelial diseases. Especially in cases of small intestinal and liver disease
where standard treatment protocols (e.g. whole organ transplantation) are not
sufficiently effective, there is a need for alternative therapeutic
interventions, like adult stem cell transplantation.
Autologous tissue engineering is an attractive therapeutic alternative to
organ transplantation. Recently, Hans Clevers et al have established a method
that enables the growth of vast amounts of mouse intestinal and gastric tissue
from intestinal crypts or gastric units. These 3-dimensional cultures have been
shown to recapitulate in vitro the features of the in vivo epithelia, since
they allow the maintenance of the stem cells and differentiated cells in
culture in a so-called organoid or *mini-organ*. Furthermore, no genetic
aberrations have been detected after months in culture, indicating that under
these culture conditions the cells are stable. Therefore, this culture system
provides a unique opportunity to model the architecture of epithelium in vitro,
facilitating the advance of tissue engineering.
Preliminary data show that it is feasible to generate organoids from human
intestinal biopsies (T. Sato, personal communication). Another group of
investigators communicated additional preliminary data in which they show that
colonic organoids can be successfully transplanted into mice that have been
treated with DSS to induce colitis. By using fluorescently-labeled organoids,
they demonstrated proper engraftment of epithelial cells that were behaving
similarly to endogenous tissue (T. Nakamura, personal communication).
These latest findings prompted us to pursue this technique to the next
level and determine transplantation possibilities of engineered tissue from
human gastrointestinal biopsies as an alternative treatment to whole organ
transplantation. Furthermore, the in vitro system will be useful in studying
pathogenesis of disease and develop and test novel treatment strategies (in a
personalized setting).

The STEM study presented here aims to increase our knowledge of the most common
intestinal, gastric and liver epithelial diseases with the ultimate goal to
treat these disorders.
Particularly, children that have severe malfunction of their
gastrointestinal epithelium, like in cases of MVID, are completely dependent on
TPN and are too young to undergo organ transplantation. For these patients, we
aim to develop a transplantation method with engineered autologous tissue that
is genetically modified to repair the original genetic defect or by using
engineered tissue from close relatives.
In order to take this technique into the clinic, we need to enhance our
knowledge about the differentiation of epithelial tissue in general and improve
the techniques of tissue engineering. Therefore, we will take gastrointestinal
epithelial biopsies or resected material into tissue engineering cultures in
which we will determine the differentiation potential of the tissue-specific
epithelial stem cells, the possibility to perform gene targeting on epithelial
stem cells and the feasibility to use engineered tissue for transplantation
purposes.

This is an observational study in which we will culture biopsy or resection
material from epithelial tissue of both pediatric and adult patients in order
to engineer epithelial tissue. The engineered tissue will be used to study the
differentiation potency of tissue-specific stem cells. Furthermore, we will
determine genomic status of the tissue and compare to healthy control to
determine disease-related aberrancies. In case of rare diseases or unknown
deficiencies, we will determine genetic abnormalities in DNA of patients.
The knowledge we obtain from this study will be used to set-up future
intervention studies to transplant in vitro engineered specific tissue into
patients with epithelial disorders. Furthermore, the method can be used as a
modelsystem to study pathogenesis of disease and develop and test novel
treatment strategies (in a personalized setting).

Despite the fact that every biopsy encompasses a certain risk (chance of
performation during colonoscopy <1:1000 ), obtaining several additional
biopsies will not significantly increase that risk. During the biopsy or
surgical procedure, 4 additional biopsies per location or parts of the resected
material will be processed for the STEM study and taken into culture. We will
draw 10 ml of blood which will be used for DNA analysis. In future, we aim to
engineer a vast amount of autologous tissue for transplantation purposes which
may become a beneficial treatment for patients with similar diseases.