ARSA activity reconstitution and neurophysiological analysis of transplanted MLD mice. (A) Sulfatide assay on PBMCs from mice transplanted with ARSA-transduced (ARSA-LV) or GFP-transduced (As2^–/–) HSCs, 7 months after BMT, and from WT mice. Sulfatide metabolism in WT and reconstituted As2–/– mice is shown by LRh-sulfatide reduction and appearance of galactosylceramide (LRh-GalCer) (average and range of picomoles normalized for total protein content). (B) PNC assay on PBMCs as in A. ARSA activity is expressed relative to the value obtained from WT mice. Full ARSA activity reconstitution and overexpression above the WT level was observed in ARSA-transplanted mice. (C–E) Neurophysiological assessment of central and peripheral motor conduction in 8-month-old MLD mice transplanted with ARSA- or GFP-transduced HSCs, and WT mice with the same genetic background (n = 15 mice per group). Significantly lower CCTs (C) and F wave latency values (D), and significantly higher sciatic MCV values (E) were recorded in ARSA- transplanted mice compared with GFP controls. Comparison with WT shows nearly complete prevention of motor conduction impairments (P > 0.05 for all parameters). (F–H) Neurophysiological assessment in the same groups of ARSA- and mock-transplanted mice as in C–E, at 12 months of age, and in age-matched, WT HSC–transplanted mice (n = 10 mice per group). The analysis shows maintenance of the therapeutic effect in ARSA-transplanted mice and significantly faster motor conduction as compared with WT HSC–transplanted ones (*P < 0.01 between ARSA-LV and As2^–/–; ***P < 0.05 between ARSA-LV and WT HSC–transplanted mice). Data are expressed as single recordings and means.