Department of Pediatrics, Division of Genetics, University of California, San Diego, La Jolla, CA, USA.
Tissue Technology Shared Resource, Biorepository and Tissue Technology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Mol Genet Metab. 2021 Dec;134(4):309-316. doi: 10.1016/j.ymgme.2021.11.006. Epub 2021 Nov 17.
Cystinosis is an autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene encoding the lysosomal cystine transporter, cystinosin, and leading to multi-organ degeneration including kidney failure. A clinical trial for cystinosis is ongoing to test the safety and efficacy of transplantation of autologous hematopoietic stem and progenitor cells (HSPCs) ex vivo gene-modified to introduce functional CTNS cDNA. Preclinical studies in Ctns mice previously showed that a single HSPC transplantation led to significant tissue cystine decrease and long-term tissue preservation. The main mechanism of action involves the differentiation of the transplanted HSPCs into macrophages within tissues and transfer of cystinosin-bearing lysosomes to the diseased cells via tunneling nanotubes. However, a major concern was that the most common cystinosis-causing mutation in humans is a 57-kb deletion that eliminates not only CTNS but also the adjacent sedopheptulose kinase SHPK/CARKL gene encoding a metabolic enzyme that influences macrophage polarization. Here, we investigated if absence of Shpk could negatively impact the efficiency of transplanted HSPCs to differentiate into macrophages within tissues and then to prevent cystinosis rescue. We generated Shpk knockout mouse models and detected a phenotype consisting of perturbations in the pentose phosphate pathway (PPP), the metabolic shunt regulated by SHPK. Shpk mice also recapitulated the urinary excretion of sedoheptulose and erythritol found in cystinosis patients homozygous for the 57-kb deletion. Transplantation of Shpk-HSPCs into Ctns mice resulted in significant reduction in tissue cystine load and restoration of Ctns expression, as well as improved kidney architecture comparable to WT-HSPC recipients. Altogether, these data demonstrate that absence of SHPK does not alter the ability of HSPCs to rescue cystinosis, and then patients homozygous for the 57-kb deletion should benefit from ex vivo gene therapy and can be enrolled in the ongoing clinical trial. However, because of the limits inherent to animal models, outcomes of this patient population will be carefully compared to the other enrolled subjects.
胱氨酸贮积症是一种常染色体隐性溶酶体贮积症，由编码溶酶体胱氨酸转运体胱氨酸酶的 CTNS 基因突变引起，导致多器官退行性变，包括肾衰竭。目前正在进行一项针对胱氨酸贮积症的临床试验，以测试体外基因修饰自体造血干细胞和祖细胞 (HSPCs) 移植的安全性和疗效，从而引入功能性 CTNS cDNA。此前在 Ctns 小鼠中的临床前研究表明，单次 HSPC 移植可显著降低组织胱氨酸含量并长期保存组织。主要作用机制涉及移植的 HSPC 分化为组织内的巨噬细胞，并通过隧道纳米管将携带胱氨酸酶的溶酶体转移至病变细胞。然而，人们主要关注的是，人类最常见的胱氨酸贮积症致病突变是 57-kb 缺失，该缺失不仅消除了 CTNS，还消除了相邻的 sedopheptulose 激酶 SHPK/CARKL 基因，该基因编码一种影响巨噬细胞极化的代谢酶。在这里，我们研究了 Shpk 的缺失是否会对移植的 HSPC 分化为组织内的巨噬细胞的效率产生负面影响，然后防止胱氨酸贮积症的恢复。我们生成了 Shpk 敲除小鼠模型，并检测到戊糖磷酸途径 (PPP) 和 SHPK 调节的代谢旁路的扰动组成的表型。Shpk 小鼠还再现了 57-kb 缺失纯合子胱氨酸贮积症患者的 sedoheptulose 和赤藓糖醇的尿排泄。将 Shpk-HSPCs 移植到 Ctns 小鼠中可显著降低组织胱氨酸负荷并恢复 Ctns 表达，以及改善与 WT-HSPC 受者相当的肾脏结构。总的来说，这些数据表明 SHPK 的缺失不会改变 HSPC 拯救胱氨酸贮积症的能力，因此，57-kb 缺失纯合子的患者应受益于体外基因治疗，并可被纳入正在进行的临床试验。然而，由于动物模型固有的局限性，将仔细比较该患者群体的结果与其他入组的受试者。
