Lysosomal and GBA studies. (A) Transmission electron microscope photography of passage 5 MSCs, the lysosomes being the dark gray organelles; scale bar = 1 μm. (B) Total lysosomal content assessed by flow cytometry of Lyso Tracker Yellow–stained passage 3 MSCs. (C) Relative mRNA levels for GBA in passage 4 MSCs. (D) Scanned autoradiogram of a Western blot performed for GBA expression analysis on passage 4 MSCs, with β-tubulin expression used as a loading control on the same samples. The large band for GBA is explained by differently glycosylated forms of GBA. (E) GBA enzymatic activity expressed in nanomoles of 4-MU formed per hour per milligrams of total protein content in the sample. **P < .001. (F-G) Sphingolipids were analyzed in normal and Gaucher disease MSCs by high-performance liquid chromatography–tandem mass spectrometry and were normalized for total cellular inorganic phosphate. Shown are glucosylceramide levels (F) and sphingosine-1-phosphate (G). *P < .05. All error bars represent 1 SD.