(#26) Alterations in the Molecular Pathways Involved in the Expression of Hyaluronan in Human Pancreatic Islets

PRESENTED BY: Edgard Cruz

Authors
First NameLast NameAffiliation/Institution
Edgard A.CruzUniversity of Tennesee Health Science Center
NataliyaLenchikUniversity of Tennessee Health Science Center
MarthaCampbell-ThompsonUniversity of Florida, Gainesville
ClaytonMatthewsUniversity of Florida, Gainesville
MarkAtkinsonUniversity of Florida, Gainesville
Ivan C.GerlingUniversity of Tennessee Health Science Center
 

Purpose

Hyaluronic acid (HA) has been found to accumulate in the extracellular matrix (ECM) of insulitic islets. Low molecular weight HA (LMW-HA) is associated with activation of inflammatory pathways and recruitment/activation of T-cells involved in the progression of Type 1 diabetes (T1D). This study used a previously described dataset of transcriptomes from 260 individual islets to evaluate the changes in transcription of genes from these pathways in normal vs. insulitic islets.
 

Methods

Analysis of prior data from 260 laser-captured human pancreatic islet samples from nPOD organ donors. Samples were obtained from 3 disease states: Control, AB+, and T1D. Tissue staining produced four types of islets: Ins+CD3-, Ins+CD3+, Ins-CD3+, and Ins-CD3-. RNA transcriptomes were collected and data analyzed by unpaired, uneven t-tests. Literature review and data mining with WebGestalt into geneontology and KEGG pathways were performed to identify specific genes of interest – which were then analyzed for expression differences in Ins+CD3- vs. Ins+CD3+ islets (normal vs insulitic).
 

Summary of Results

Hyaluronan Lyase 2, a gene responsible for cleaving high molecular weight hyaluronic acid (HMW-HA) to the proinflammatory low molecular weight form, was increased in islets from AB+ donors compared to both controls and T1D donor islets. Expression levels above 600 units were seen in 13/77 islets from AB+ donors (17%) but not in islets from control (0/73) or T1D donors (0/110). LMW-HA binding with receptors such as CD44 and TLR4 on T cells may cause cascade events which promotes leukocyte recruitment and infiltration. Multiple genes involved in pathways activated by LMW-HA were found to be differentially expressed in islets with insulitis vs those without. Those genes are associated with CD44 cascade signaling, leukocyte recruitment, apoptosis, ECM degradation, angiogenesis, as well as β cell function and differentiation.
 

Conclusions

Our data show an increased expression of LMV-HA in 17% of islets from AB+ donors but not in islets from controls and T1D donors. Genes from pathways that are downstream activated by LMV-HA were increased in insulitic (Ins+CD3+) islets compared to normal (Ins+CD3-) islets. This suggests an important role for HYAL2 in the early stages of islet pathology.