2nd Year Research Reviews – 2014

Calogera Simonaro, PhD
Icahn School of Medicine at Mount Sinai, New York, NY
“Pentosan Polysulfate and GAGs in MPS”

We have previously investigated the effects of PPS in MPS animals (MPS I & VI), and surprisingly found a significant reduction of tissue GAGs (Frohbergh et al., 2014; Simonaro et al., 2016).  These findings were recently confirmed in two proof-of-concept clinical trials (in MPS I & II patients), where urine GAGs were reduced up 50% compared to baseline during 6 months of treatment (Hennermann et al., 2016).  The goal of this research study was therefore to investigate the mechanism(s) underlying this novel finding. The expression of several genes encoding GAG-synthetic enzymes was examined in skin fibroblasts from MPS patients by quantitative PCR, and found to be elevated compared to cells from healthy individuals. The pattern of abnormal gene expression was dependent on the MPS type.  PPS treatment led to reduced expression of several of these genes in a “type” and patient-specific manner.  We also observed enhanced staining of several lysosomal markers in tissues of MPS animals treated with PPS, suggesting an effect on lysosomal integrity.  Electron microscopy of MPS patient cells treated with PPS showed enhanced binding to the surface, consistent with the hypothesis that the anti-inflammatory effects of PPS are at least in part due to binding of cell-surface receptors (e.g., TLR-4).  Overall, we conclude that the positive clinical effects of PPS may be due to multiple factors, including direct effects on GAG-metabolizing enzymes (perhaps due to the structural similarities between PPS and GAGs), a potential effect on lysosomal integrity, and modulation of cell signaling through binding of surface receptors.

Beverly Davidson, PhD
The Children’s Hospital of Philadelphia
“Overcoming limitations inherent in sulfamidase to improve MPS IIIA gene therapy”

The goal of this project is to use genetic methods to modify Heparan N-Sulfatase (HNS) to improve secretion from genetically modified cells, which in turn would result in greater therapeutic benefit for MPS IIIA. In year one of this project, we identified an HNS variant with properties of improved secretion and improved uptake in vitro. During the second year of study, we compared the HNS variant and wild type HNS in vivo after AAV gene transfer into a mouse model of MPS IIIA. Gene transfer of sequences encoding the HNS variant, but not wild type HNS, reversed the spatial learning and memory deficiencies inherent in MPS IIIA mice. HNS enzyme activities in the CSF and brain tissues were approximately two times higher in variant vs. normal HNS-expressing mice.  Also, varianttreated mice showed decreases in secondary lysosomal enzyme elevations. Together, our data show that gene transfer of the HNS variant is advantageous over wildtype HNS for MPS IIIA gene therapy.