Mucopolysaccharidosis type VII (MPS7) is a lysosomal storage disorder (LSD) resulting from mutations in the β-glucuronidase gene, leading to multiorgan dysfunction and fetal demise. While postnatal enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation have resulted in some phenotypic improvements, prenatal treatment might take advantage of a unique developmental window to penetrate the blood-brain barrier or induce tolerance to the missing protein, addressing two important shortcomings of postnatal therapy for multiple LSDs. We performed in utero ERT (IUERT) at E14.5 in MPS7 mice and improved survival of affected mice to birth. IUERT penetrated brain microglia, whereas postnatal administration did not, and neurological testing (after IUERT plus postnatal administration) showed decreased microglial inflammation and improved grip strength in treated mice. IUERT prevented antienzyme antibody development even after multiple repeated postnatal challenges. To test a more durable treatment strategy, we performed in utero hematopoietic stem cell transplantation (IUHCT) using congenic CX3C chemokine receptor 1–green fluorescent protein (CX3CR1-GFP) mice as donors, such that donor-derived microglia are identified by GFP expression. In wild-type recipients, hematopoietic chimerism resulted in microglial engraftment throughout the brain without irradiation or conditioning; the transcriptomes of donor and host microglia were similar. IUHCT in MPS7 mice enabled cross-correction of liver Kupffer cells and improved phenotype in multiple tissues. Engrafted microglia were seen in chimeric mice, with decreased inflammation near donor microglia. These results suggest that fetal therapy with IUERT and/or IUHCT could overcome the shortcomings of current treatment strategies to improve phenotype in MPS7 and other LSDs.

No abstract

Galactosialidosis is a rare lysosomal storage disease caused by a congenital defect of protective protein/cathepsin A (PPCA) and secondary deficiency of neuraminidase-1 and b-galactosidase. PPCA is a lysosomal serine carboxypeptidase that functions as a chaperone for neuraminidase-1 and b-galactosidase within a lysosomal multi-protein complex. Combined deficiency of the three enzymes leads to accumulation of sialylated glycoproteins and oligosaccharides in tissues and body fluids and manifests in a systemic disease pathology with severity mostly correlating with the type of mutation(s) and age of onset of the symptoms. Here, we describe a proof-of-concept, preclinical study toward the development of enzyme replacement therapy for galactosialidosis, using a recombinant human PPCA. We show that the recombinant enzyme, taken up by patient-derived fibroblasts, restored cathepsin A, neuraminidase-1, and b-galactosidase activities. Long-term, bi-weekly injection of the recombinant enzyme in a cohort of mice with null mutation at the PPCA (CTSA) locus (PPCA -/-), a faithful model of the disease, demonstrated a dose-dependent, systemic internalization of the enzyme by cells of various organs, including the brain. This resulted in restoration/normalization of the three enzyme activities, resolution of histopathology, and reduction of sialyloligosacchariduria. These positive results underscore the benefits of a PPCA-mediated enzyme replacement therapy for the treatment of galactosialidosis.

No abstract

Introduction Mucopolysaccharidosis type 7 (MPS7) is a lysosomal storage disorder typically fatal in utero. Postnatal enzyme replacement therapy (ERT) to replace missing glucuronidase (GUS) does not penetrate the blood-brain barrier (BBB). We investigated whether in utero ERT (IUERT) specifically targets brain microglia (natural GUS storehouses and key brain inflammation mediators) and whether in utero hematopoietic stem cell transplantation (IUHSCT) results in microglial engraftment as a strategy for permanent correction. Methods We performed IUERT by injecting GUS into MPS7 fetuses mid-gestation, and analyzed tissue homogenates (via colorimetric substrate) and brain microglia (via flow cytometry) for enzyme activity after 4-7 days. We performed IUHSCT by transplanting HSCs mid-gestation from CX3CR1-GFP donors. We examined blood, bone marrow, and brain for engraftment. We assessed brain inflammation by staining for CD68. We performed RNA sequencing to characterize engrafted microglia. Results IUERT resulted in detectable brain GUS activity. Flow cytometry showed that GUS activity after IUERT was near wild-type levels, and brains harvested in adulthood had decreased inflammation via CD68 immunohistochemistry. IUHSCT resulted in multilineage engraftment of hematopoietic cells in blood and bone. Confocal microscopy revealed multifocal engraftment of donor-derived microglia. RNA sequencing indicated that engrafted microglia were nearly identical to endogenous microglia. MPS7 chimeras had evidence of reduced brain inflammation near donor microglia. Conclusion Both IUERT and IUHSCT are complementary treatment modalities that can penetrate the BBB and ameliorate neurologic manifestations of diseases such as MPS7. These results lay the foundation for future studies using in utero molecular therapies for MPS7 as well as other storage disorders.