利用病患特異性的誘導性多能幹細胞探討第二型黏多醣症的神經退化性病變機制及測試藥物

Abstract

第二型黏多醣症 (MPS II) 由於己醛糖酸鹽硫酸脂酶 (IDS) 缺乏，導致醣胺聚醣 (GAG)的積累。第二型黏多醣症嚴重型會引起漸進性神經性退化以及死亡，而目前的治療方法無效。因此，在本研究中，我們從四名患有第二型黏多醣症嚴重型的患者生成多株誘導性多能幹細胞 (iPSCs) 及其同基因對照組 (isogenic control, ISO)。這些第二型黏多醣症幹細胞 (MPS II-iPSCs) 能成功分化成第二型黏多醣症特異性皮質神經元，顯示出特徵性生化和細胞表型，包括磷酸化 tau 陽性軸突珠串和明顯的電生理異常。然而，這些缺陷在同基因對照組 (ISO) 分化的神經元中大部分都獲得改善，這表明MPS II-iPSC分化的神經元能忠實地呈現第二型黏多醣症皮質神經元的病理生理特徵。在分析RNA-seq數據後，我們發現MPS II成熟神經元與健康受試者相比，Wnt/β-catenin、p38 MAP激酶和鈣信號通路的基因表達存在差異。基於這些失調的通路，我們使用這種成熟的第二型黏多醣症神經元平台測試了幾種相關化合物和藥物。一種高度選擇性的小分子肝醣合成酶激酶3β (GSK3β) 抑製劑顯著改善第二型黏多醣症神經元神經元的存活率、神經突形態和電生理異常。如我們的研究所示，第二型黏多醣症誘導性多能幹細胞平台揭示了第二型黏多醣症中神經元退化和死亡的機制，並可能有助於評估治療候選藥物。此外，這項工作表明第二型黏多醣症相關的神經元功能障礙在早期並非不可逆轉，針對第二型黏多醣症神經元中GAG積累所導致下游的失調信號通路進行治療，可能有助於挽救神經退化過程。

Mucopolysaccharidosis type II (MPS II), due to iduronate-2-sulfatase deficiency, leads to glycosaminoglycans (GAG) accumulation. Severe MPS II causes progressive neurodegeneration and death, while current treatments are ineffective. To this end, in the present study, we generated several clones of induced pluripotent stem cells (iPSCs) and their isogenic control (ISO) from four patients affected with the serve form of MPS II. The MPS II-iPSCs were successfully differentiated into MPS II-specific cortical neurons showing the characteristic biochemical and cellular phenotypes, including phosphorylated tau-positive axonal beading and distinct electrophysical abnormalities. However, these deficits were largely rescued in ISO-iPSC-neurons, indicating that the MPS II-iPSC-derived neurons faithfully displayed the pathophysiological features of MPS II cortical neurons. After analyzing RNA-seq data, we identified differences in the gene expression of the Wnt/β-catenin, p38 MAP kinase, and calcium signaling pathways in MPS II mature neurons compared to controls. Based on these dysregulated pathways, several related chemicals and drugs were tested using this mature MPS II neuron-based platform. A highly selective small molecule glycogen synthase kinase 3β (GSK3β) inhibitor significantly ameliorated neuronal survival, neurite morphology, and electrophysiological defects in MPS II neurons. Thus, the MPS II iPSC platform is valuable for dissecting the mechanism of neuronal degeneration and death in MPS II and may help evaluate therapeutic candidates. In addition, this study suggests that MPS II-associated neuronal dysfunction is not irreversible at the early stage and that targeting the dysregulated signaling pathways downstream of GAG accumulation in MPS II neurons may help to rescue the neurodegenerative process.