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PubMed1980

The uptake of enzymes into lysosomes: an overview.

Although it is possible to introduce enzymes and other proteins into lysosomes by nonspecific or "fluid" endocytosis, this process is very inefficient. Efficiency and selectivity are provided by the interaction of receptors on the cell surface and specific markers on the protein. Because most lysosomal enzymes are glycoproteins, the carbohydrate recognition systems are particularly relevant to their uptake. The systems that have been discovered are cell-specific and recognize the following terminal sugar residues: mammalian hepatocytes, galactose (also N-acetylgalactosamine, glucose) and L-fucose; avian hepatocytes, N-acetylglucosamine; mammalian reticuloendothelial cells, mannose (also N-acetylglucosamine, glucose); human fibroblasts, mannose 6-phosphate. Because of the ubiquity of mannose-terminated oligosaccharide chains on lysosomal enzymes derived from tissues, the reticuloendothelial system is probably of major importance in clearing injected enzymes from the circulation. The mannose 6-phosphate recognition system probably functions in directing endogenous enzymes, synthesized by fibroblasts, to the lysosomes of these cells. The existence of cell-specific recognition systems presents a challenge to future attempts at enzyme replacement in lysosomal storage diseases; enzymes will have to be selected or modified to have the appropriate marker for uptake by the cells where storage occurs.

Animals↗
PubMedDate not supplied

[Metabolism of the basic component of connective tissue at various stages of developing experimental liver cirrhosis].

A system of GAG-hydrolase was studied in liver tissue and blood plasma during development of CCl4-produced cirrhosis of liver tissue in series of experiments involving 400 adult rat males. Dissimilar pathways of the matrix formation, related to dynamics of the GAG-hydrolases activity, were detected within various steps of the chronic CCL4-produced liver tissue impairments in these rats. Alterations in the enzymatic activity were stable and regular in each series of the experiment and correlated with dynamics of the adaptation-compensatory responses.

Animals↗
PubMed1996

Outcome of unrelated donor bone marrow transplantation in 40 children with Hurler syndrome.

Long-term survival and improved neuropsychological function have occurred in selected children with Hurler syndrome (MPS I H) after successful engraftment with genotypically matched sibling bone marrow transplantation (BMT). However, because few children have HLA-identical siblings, the feasibility of unrelated donor (URD) BMT as a vehicle for adoptive enzyme therapy was evaluated in this retrospective study. Forty consecutive children (median, 1.7 years; range, 0.9 to 3.2 years) with MPS I H received high-dose chemotherapy with or without radiation followed by BMT between January 27, 1989 and May 13, 1994. Twenty-five of the 40 patients initially engrafted. An estimated 49% of patients are alive at 2 years, 63% alloengrafted and 37% autoengrafted. The probability of grade II to IV acute graft-versus-host disease (GVHD) was 30%, and the probability of extensive chronic GVHD was 18%. Eleven patients received a second URD BMT because of graft rejection or failure. Of the 20 survivors, 13 children have complete donor engraftment, two children have mixed chimeric grafts, and five children have autologous marrow recovery. The BM cell dose was correlated with both donor engraftment and survival. Thirteen of 27 evaluable patients were engrafted at 1 year following URD BMT. Neither T-lymphocyte depletion (TLD) of the bone marrow nor irradiation appeared to influence the likelihood of engraftment. Ten of 16 patients alive at 1 year who received a BM cell dose greater than or equal to 3.5 x 10(8) cells/kg engrafted, and 62% are estimated to be alive at 3 years. In contrast, only 3 of 11 patients receiving less than 3.5 x 10(8) cells/kg engrafted, and 24% are estimated to be alive at 3 years (P = .05). The mental developmental index (MDI) was assessed before BMT. Both baseline and post-BMT neuropsychological data were available for 11 engrafted survivors. Eight children with a baseline MDI greater than 70 have undergone URD BMT (median age, 1.5 years; range, 1.0 to 2.4 years). Of these, two children have had BMT too recently for developmental follow-up. Of the remaining six, none has shown any decline in age equivalent scores. Four children are acquiring skills at a pace equal to or slightly below their same age peers; two children have shown a plateau in learning or extreme slowing in their learning process. For children with a baseline MDI less than 70 (median age, 2.5 years; range, 0.9 to 2.9 years), post-BMT follow-up indicated that two children have shown deterioration in their developmental skills. The remaining three children are maintaining their skills and are adding to them at a highly variable rate. We conclude that MPS I H patients with a baseline MDI greater than 70 who are engrafted survivors following URD BMT can achieve a favorable long-term outcome and improved cognitive function. Future protocols must address the high risk of graft rejection or failure and the impact of GVHD in this patient population.

Bone Marrow Transplantation↗