[Lysosomal enzyme deficiency: in vitro correlation of deficient cells using a conditioned medium or by co-culturing...

We demonstrate that lysosomal enzyme (alpha-L-fucosidase) can enrich deficient fibroblasts, with purified enzyme brought by the medium, or with an enzyme supply by various cell sources. The co-culture systems lead to a deficient cell correction, whatever donor cells are lymphocytes or lymphoblastoid cells. This correction arise only with alive cells, and is strongly inhibited by mannose-6-phosphate. Our results do not support the hypothesis that cell to cell contact independently of mannose-6-phosphate binding site is necessary for transfer of lysosomal enzyme from lymphocytes to fibroblasts. We suggest that the neighbourhood of cells leads to a phosphorylated precursor increase in the pericellular area, which creates an enzyme stabilizing effect favourable at its incorporation.