Progranulin (PGRN) haploinsufficiency is a major risk factor for frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43) pathology (FTLD- GRN ). Multiple therapeutic strategies are in clinical development to restore PGRN in the CNS, including gene therapy. However, a limitation of current gene therapy approaches aimed to alleviate FTLD-associated pathologies may be their inefficient brain exposure and biodistribution. We therefore developed an adeno-associated virus (AAV) targeting the liver (L) to achieve sustained peripheral expression of a transferrin receptor (TfR) binding, brain-penetrant (b) PGRN variant [AAV(L):bPGRN] in two mouse models of FTLD- GRN , namely, Grn knockout and GrnxTmem106b double knockout mice. This therapeutic strategy avoids potential safety and biodistribution issues of CNS-administered AAVs and maintains sustained concentrations of PGRN in the brain after a single dose. AAV(L):bPGRN treatment reduced several FTLD- GRN –associated pathologies including severe motor function deficits, aberrant TDP-43 phosphorylation, dysfunctional protein degradation, lipid metabolism, gliosis, and neurodegeneration in the brain. The potential translatability of our findings was tested in an in vitro model using cocultured human induced pluripotent stem cell (hiPSC)–derived microglia lacking PGRN and TMEM106B and wild-type hiPSC-derived neurons. As in mice, aberrant TDP-43, lysosomal dysfunction, and neuronal loss were ameliorated after treatment with exogenous TfR-binding protein transport vehicle fused to PGRN (PTV:PGRN). Together, our studies suggest that peripherally administered brain-penetrant PGRN replacement strategies ameliorate FTLD- GRN relevant phenotypes including TDP-43 pathology, neurodegeneration, and behavioral deficits. Our data provide preclinical proof of concept for the use of this AAV platform for treatment of FTLD- GRN and potentially other CNS disorders.

中文翻译：

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脑渗透性颗粒体蛋白前体的外周表达可挽救额颞叶变性小鼠模型的病理状态


颗粒体蛋白前体 (PGRN) 单倍体不足是 TAR DNA 结合蛋白 43 (TDP-43) 病理学 (FTLD-GRN) 额颞叶变性的主要危险因素。多种治疗策略正在临床开发中，以恢复 CNS 中的 PGRN，包括基因治疗。然而，当前旨在减轻 FTLD 相关病理的基因治疗方法的局限性可能在于其大脑暴露和生物分布效率低下。因此，我们开发了一种靶向肝脏 (L) 的腺相关病毒 (AAV)，以在两只小鼠中实现转铁蛋白受体 (TfR) 结合、脑渗透 (b) PGRN 变体 [AAV(L):bPGRN] 的持续外周表达FTLD-GRN模型，即Grn敲除小鼠和GrnxTmem106b双敲除小鼠。这种治疗策略避免了中枢神经系统施用 AAV 的潜在安全性和生物分布问题，并在单次剂量后维持大脑中 PGRN 的持续浓度。 AAV(L):bPGRN 治疗减少了多种 FTLD-GRN 相关的病理，包括严重的运动功能缺陷、异常的 TDP-43 磷酸化、功能失调的蛋白质降解、脂质代谢、神经胶质增生和大脑神经变性。我们的研究结果的潜在可转化性在体外模型中进行了测试，使用共培养的缺乏 PGRN 和 TMEM106B 的人诱导多能干细胞 (hiPSC) 衍生的小胶质细胞和野生型 hiPSC 衍生的神经元。与小鼠中一样，用与 PGRN 融合的外源 TfR 结合蛋白转运载体 (PTV:PGRN) 治疗后，异常的 TDP-43、溶酶体功能障碍和神经元损失得到改善。总之，我们的研究表明，外周给药的脑渗透性 PGRN 替代策略可改善 FTLD-GRN 相关表型，包括 TDP-43 病理、神经变性和行为缺陷。 我们的数据为使用该 AAV 平台治疗 FTLD-GRN 和潜在的其他中枢神经系统疾病提供了临床前概念证明。