In vitro analysis of multipotent mesenchymal stromal cells as potential cellular therapeutics in neurometabolic diseases in pediatric patients.

Multipotent mesenchymal stromal cells (MSCs) play an important role in stromal support for hematopoietic stem cells, immune modulation, and tissue regeneration. We investigated their potential as cellular therapeutic tools in neurometabolic diseases as a growing number of affected children undergo to bone marrow transplantation. MSCs were isolated from bone marrow aspirates and expanded ex vivo under various culture conditions. MSCs under optimal good medical practice (GMP)-conform culture conditions showed the typical morphology, immunophenotype, and plasticity. Biochemically, the activities of beta-hexosaminidase A, total beta-hexosaminidase, arylsulfatase A (ASA), and beta-galactosidase measured in MSCs were comparable to those in fibroblasts of healthy donors. These four enzymes were interesting for their expression in MSCs, as each of them is defective, respectively, in well-known neurometabolic diseases. We found that MSCs released significant amounts of ASA into the media. In coculture experiments, fibroblasts from patients with metachromatic leukodystrophy, who are deficient for ASA, took up a substantial amount of ASA that was released into the media from MSCs. Mannose-6-phosphate (M6P) inhibited this uptake, which was in accordance with the M6P receptor-mediated uptake of lysosomal enzymes. Taken together, we show that MSCs produce appreciable amounts of lysosomal enzyme activities, making these cells first-choice candidates for providing metabolic correction when given to enzyme-deficient patients. With the example of ASA, it was also shown that an enzyme secreted from MSCs is taken up by enzyme-deficient patient fibroblasts. Given the plasticity of MSCs, these cells represent an interesting add-on option for cellular therapy in children undergoing bone marrow transplantation for lysosomal storage diseases and other neurometabolic diseases.