A failure in self-tolerance leads to autoimmune
destruction of pancreatic β-cells and type 1 diabetes (T1D). Low molecular
weight dextran sulfate (DS) is a sulfated semi-synthetic polysaccharide with demonstrated
cytoprotective and immunomodulatory properties <i>in vitro</i>. However, whether DS can protect pancreatic β-cells,
reduce autoimmunity and ameliorate T1D is unknown. Here we report that DS, but
not dextran, protects human β-cells against cytokine-mediated cytotoxicity <i>in vitro</i>. DS also protects mitochondrial
function and glucose-stimulated insulin secretion and reduces chemokine
expression in human islets in a pro-inflammatory environment. Interestingly, daily
treatment with DS significantly reduces diabetes incidence in pre-diabetic non-obese
diabetic (NOD) mice, and most importantly, reverses diabetes in early-onset
diabetic NOD mice. DS decreases β-cell death, enhances islet heparan sulfate
(HS)/heparan sulfate proteoglycan (HSPG) expression and preserves β-cell mass
and plasma insulin in these mice. DS administration also increases the
expression of the inhibitory co-stimulatory molecule programmed death-1 (PD-1) in
T-cells, reduces interferon-γ+ CD4+ and CD8+ T-cells and enhances the number of
FoxP3+ cells. Collectively, these studies demonstrate that the action of one
single molecule, DS, on β-cell protection, extracellular matrix preservation
and immunomodulation can reverse diabetes in NOD mice highlighting its
therapeutic potential for the treatment of T1D.