(256k) Dextran Sodium Sulfate Exposure Affects Intestinal Mucus Integrity

Dextran
Sodium Sulfate Exposure Affects Intestinal Mucus Integrity

Jaclyn Y. Lock¹,
Taylor Carlson², Albert Chen²,
Rebecca L. Carrier^1,2

¹Department of Bioengineering, ²Department
of Chemical Engineering, Northeastern University

Introduction:
Dextran sodium sulfate (DSS) is
frequently utilized to induce intestinal inflammation in animal models of colitis. This model is heavily used since it mimics
the histological features of colitis, but the mechanism by which DSS induces
inflammation remains unclear. Mucus, a natural biomaterial, covers the entire
gastrointestinal tract and selectively controls the diffusion of molecules,
particulate matter, and microorganisms to the underlying epithelial layer. Thus,
we hypothesize that DSS may impact the mucus barrier. In this study, we
investigated how DSS exposure affects mucus barrier properties through particle
and microbe tracking, and micro-structural analysis. These studies may provide
information on the potential role of an altered mucus barrier in progression of
inflammation.

Materials and Methods: Native porcine intestinal mucus was
harvested within two hours of sacrifice. Transport properties of green fluorescent protein (GFP) expressing Escherichia coli (E. coli), and 200 nm
fluorescent particles with surface carboxyl, amine, and polyethylene glycol
(PEG) functionalization were probed using multiple particle tracking technique.
Briefly, microbes or particles were diluted in the presence of 1% DSS or
maleate buffer (MB) control. 20 sec video particle trajectories were analyzed
using a modification of a MATLAB script developed by Maria Kilfoil³
to calculate mean mean-squared displacement (<MSD>) and effective
diffusivity (D_eff),
where MSD = [x(t + τ) – x(t)]² +
[y(t + τ) – y(t)]² and D_eff= MSD * 4τ, x(t) and
y(t) represent the particle coordinates at a given time and τ is the time
scale. To image the changes in particle and microbe distribution within lectin-stained mucus exposed to DSS or MB control, z-stack
images were obtained using a confocal microscope. Scanning electron microscopy
was utilized to visualize micro-structural changes when 1% DSS was dosed to
porcine intestinal mucus. StudentÕs
T-test was used to determine significance between particle and microbe
transport with α = 0.05.

Results and
Discussion:  Particle diffusion in mucus
 exposed to 1% DSS was
significantly hindered. Specifically, there was a 8-,
3-, and 5- fold decrease in <MSD> for amine-, carboxyl-, and PEGylated
particles when dosed with 1% DSS compared to MB control. Interestingly, for E. coli undergoing active transport, the
microbes moved faster in the presence of 1% DSS in intestinal mucus and there
was an increase in linear trajectories (Fig. 1).

Conclusion: These results
indicate that a 1% DSS solution does alter mucus barrier properties, both with
respect to particles and microbes. Further in
vivo studies investigating impact of orally dosed DSS on a mucus layer on
intact tissue will facilitate understanding the role of DSS in inflammation.