• Navarro, Guadalupe
• Hu, Kenneth H.
• Kratochvil, Michael J.
• Yadava, Koshika
• Zhao, Wenting
• Nagy, Nadine
• Zerda, Adi De La
• Kaber, Gernot
• Johnson, Pamela Y.
• Bollyky, Paul L.
• Butte, Manish J.
• Annes, Justin P.
• Wight, Thomas N.
• Heilshorn, Sarah C.
• Cui, Yi

Abstract

We have identified a novel role for hyaluronan (HA), an extracellular matrix (ECM) polymer, in governing the mechanical properties of inflamed tissues. We recently reported that insulitis in type 1 diabetes (T1D) of mice and humans is preceded by intra-islet accumulation of HA, a highly hygroscopic polymer. Using the DORmO double transgenic (DO11.10 x RIPmOVA) mouse model of T1D, we asked whether autoimmune insulitis was associated with changes in the stiffness of islets. To measure islet stiffness, we used atomic force microscopy (AFM) and developed a novel "bed of nails"-like approach that uses quartz glass nanopillars to anchor islets, solving a long-standing problem of keeping tissue-scale objects immobilized while performing AFM. We measured stiffness via AFM nanoindentation with a spherical indenter and found that insulitis made islets mechanically soft compared to controls. Conversely, treatment with 4-methylumbelliferone (4-MU), a small-molecule inhibitor of HA synthesis, reduced HA accumulation, diminished swelling, and restored basal tissue stiffness. These results indicate that HA content governs the mechanical properties of islets. In hydrogels with variable HA content we confirmed that increased HA leads to mechanically softer hydrogels, consistent with our model. In light of recent reports that the insulin production of islets is mechanosensitive, these findings open up an exciting new avenue of research into the fundamental mechanisms by which inflammation impacts local cellular responses.

Topics

• impedance spectroscopy
• polymer
• atomic force microscopy
• glass
• glass
• nanoindentation