Lysosomal enzyme activities in fresh and frozen chorionic villi and in cultured trophoblasts

Effect of ethanol and progesterone on monoamine oxidase activity in cultured cells of human term placenta

OBJECTIVE

The aim of this study was to evaluate the effect of ethanol and progesterone on the monoamine oxidase activity in cultured human term placental cells.

STUDY DESIGN

Human placental cells were prepared from normal human term placentas by enzymatic dispersion in Dulbecco's modified Eagle medium. The viability of placental cells prepared by our method was 90%, and the yield of placental cells was 0.6 x 10(6) cells per gram of wet placental tissue. Five milliliters of Dulbecco's modified Eagle medium containing 3 x 10(5) placental cells was plated in a 25 cm2 flask and cultured for 8 days in an incubator at 37 degrees C under an atmosphere of 5% carbon dioxide and 95% oxygen with a saturated humidity. During the culture period the culture medium was replenished every 2 days. A confluent monolayer condition was achieved after 8 days in culture. The cultured placental cells were treated with different concentrations of ethanol (0, 34.6, and 69.2 mmol/L) and progesterone (0, 16, and 32 mumol/L) on day 8 of culture for 48 hours. At the end of treatment placental cells from control and treated flasks were harvested for the analysis of monoamine oxidase activity by spectrophotometry. The effects of ethanol and progesterone on cultured placental cells were statistically analyzed by one-way analysis of variance followed by Duncan's multiple comparisons procedure.

RESULTS

A human placental cell culture system has been established from normal human term placentas. The monoamine oxidase activity in 8-day-cultured human term placental cells was significantly higher than that of freshly prepared placental cells. Ethanol concentrations at 34.6 and 69.2 mmol/L significantly increased and progesterone concentration at 32 mumol/L significantly decreased the monoamine oxidase activity.

CONCLUSION

These results suggest that the cultured human term placental cells can be used to examine the in vitro effects of ethanol and progesterone on monoamine oxidase activity. However, the physiologic significance of progesterone's inhibitory effect and the stimulatory effect of ethanol monoamine oxidase activity in the in vivo system have yet to be further investigated.

Identification of an intermediate form of beta-N-acetylhexosaminidase in chorionic villi

A minor form of beta-N-acetylhexosaminidase has been found in chorionic villi, in addition to the major forms A and B. This form does not hydrolyze the 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside-6-sulpha te substrate, is thermostable, has a higher mol mass (120,000) than A and B (100,000) and on analytical isoelectric focusing, it shows a microheterogeneity with values ranging between 6.3 and 7.0. For these characteristics, it resembles beta-N-Acetylhexosaminidase P from pregnancy serum, from which is chromatographically indistinguishable.

Variation of lysosomal enzyme activity with gestational age in chorionic villi

The activities of 14 lysosomal enzymes in chorionic villi at gestational ages of 6-12 weeks were assayed. Arylsulphatases A and B, alpha-glucosidase and beta-glucuronidase activities increased with advancing gestational age. When compared with the activity in cultured amniotic fluid cells, arylsulphatase A, beta-galactosidase, alpha-glucosidase, heparan N-sulphatase, alpha-L-iduronidase, alpha-mannosidase, neuraminidase, and sphingomyelinase showed significant differences. All except beta-glucuronidase showed lower activity in chorionic villi than in cultured amniotic fluid cells. Prenatal diagnosis using chorionic villi was possible except for alpha-L-iduronidase. Storage at -20 degrees C up to 42 days did not significantly affect activity. The results emphasize the importance of using fresh or frozen age-matched control tissue for diagnosis.

Prenatal diagnosis of I-cell disease in the first and second trimesters

First trimester prenatal diagnosis of I-cell disease (1 case) was based on demonstration of profound deficiency of N-acetylglucosamine 1-phosphotransferase in chorionic villi and in cultured trophoblasts derived from the chorionic villus specimen. Deficiency of this enzyme in cultured amniotic fluid cells obtained via amniocentesis was the basis for prenatal diagnosis of I-cell disease in the second trimester (2 cases). In both procedures, the diagnosis was corroborated by the finding of intracellular deficiency and extracellular elevation of multiple lysosomal enzymes in the fetal cell cultures (trophoblasts and amniotic fluid cells), as well as a significant increase in several lysosomal enzyme activities in the maternal serum.

First trimester prenatal evaluation for I-cell disease by N-acetyl-glucosamine 1-phosphotransferase assay

First trimester prenatal diagnosis was offered to a couple at risk for having a child with I-cell disease (mucolipidosis II). The prenatal evaluation was based for the first time on examination of N-acetylglucosamine 1-phosphotransferase activity, deficiency of which is the primary biochemical defect in both I-cell disease and pseudo-Hurler polydystrophy (mucolipidosis III). Heterozygote levels of this enzyme activity were determined in chorionic villi obtained at 9 weeks of gestation, as well as in cultured trophoblasts derived from this specimen, and led to the diagnosis of an unaffected fetus. This procedure has advantages over that based on detection of abnormal intracellular-extracellular distribution of lysosomal enzyme activities, which is expressed only in homozygotes and fully expressed only in cell culture specimens.

A nonpathologic allele (IW) for low alpha-L-iduronidase enzyme activity vis-a-vis prenatal diagnosis of Hurler syndrome

We identified a phenotypically normal obligate heterozygote for Hurler syndrome with exceedingly low levels of alpha-L-iduronidase enzyme activity. Subsequent investigation determined that low alpha-L-iduronidase activity was systemic, also characteristic of the subject's leukocytes and cultured skin fibroblasts. Residual alpha-L-iduronidase activity of cultured fibroblasts was found to have reduced catalytic activity (Vmax) against the 4-methylumbelliferone substrate, but normal substrate affinity (KM). Additional studies further characterized the residual enzyme activity in this woman who is an apparent compound heterozygote for Hurler syndrome, and for an allele with low alpha-L-iduronidase activity lacking pathologic manifestation. Such low activity "pseudodeficiency" alleles will complicate attempts at prenatal diagnosis of Hurler syndrome and related disorders in rare families.