Biomedical Engineering Reference
In-Depth Information
Knowledge gained from cell adhesion studies with SAMs has been used to
develop culture substrates with the appropriate cell adhesion glycoproteins for
different types of cells [
7
-
10
]. Stem cells, capable of self-renewal and differentia-
tion into multiple cell types, are found in embryonic and adult tissues. Pluripotent
stem cells, like embryonic stem cells and induced pluripotent stem cells, have been
developed in vitro. These cells are expected to provide cell sources for regenerative
medicine. Various culture conditions have been developed to enable expansion of
these cells without loss of their multi- and pluripotency and to induce differentia-
tion into viable cells with specific functions.
In the last few years, our group has focused on neural stem cells (NSCs). NSCs
were discovered by screening rodent CNS cells for responses to epidermal growth
factor (EGF) [
11
]. Integrin and epidermal growth factor receptor (EGFR) coordi-
nately regulate cell migration, survival, and growth by modulating a common set of
signaling pathways. Moreover, EGF was shown to be a mitogen for NSCs. Taking
these facts into consideration, we hypothesized that NSCs might be selectively
trapped on SAM surfaces through EGF-EGFR interactions, and that this interaction
might strongly promote NSC proliferation due to EGFR signaling. In the second
part of this article (Sect.
3
), we will describe our own work on cultured NSC
interactions with surface-immobilized EGF.
Regenerative medicine and tissue engineering have opened new therapeutic
domains. Stem cells have become therapeutic units for generating functional cells
and tissues. One of themore successful endeavors has been the transplantation of islets
of Langerhans (islets), which produce and release insulin, as a treatment for patients
with type 1 diabetes. However, implantation of living cells into a host induces various
undesirable biological responses similar to the responses against artificial materials,
such as blood coagulation, complement activation, inflammatory reactions, and
immune reactions. Understanding biological responses to artificial materials [
2
]and
surface modification methods for biomaterials gives bases to evade adverse host
responses and to improve functions of transplanted cells. For living cells and tissues,
however, surface treatment should be carried out under the physiological conditions
that do not deteriorate their viability and biological functions. We developed new
methods to modify the surfaces of cells and tissues to increase their compatibility with
a host environment. In the last part of this review (Sect.
4
), we discuss the latest
methods for modifying islet surfaces and their effects on islet-host compatibility.
2 Cell Adhesion to a Model Biomaterial Surface
2.1 Self-Assembled Monolayer as a Model Surface
Self-assembled monolayers (SAMs) of alkanethiols, HS(CH
2
)
n
X, where X denotes
various functional groups, are frequently used to prepare model surfaces [
3
-
6
].
Alkanethiols or alkanedisulfides chemisorb from a solution onto a surface coated
