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Early prenatal development of the brush border enzymes in the embryonal intestine
1Department of Histology and Embryology, Medical Faculty, Palacký University, Olomouc, Czechoslovakia.
Insights
Human embryonic intestinal development shows early protease activity, particularly DPP IV, on the primitive epithelium. Later, brush border enzymes like disaccharidases and phosphatases emerge as villi and crypts differentiate.
Area of Science:
- Developmental biology
- Gastroenterology
- Human embryology
Background:
- The intestinal brush border enzymes play crucial roles in nutrient digestion and absorption.
- Understanding the developmental timeline of these enzymes is essential for comprehending early human intestinal function.
Purpose of the Study:
- To investigate the spatiotemporal activity of brush border enzymes during human embryonic intestinal development.
- To characterize the emergence and localization of peptidase, phosphatase, and disaccharidase groups.
Main Methods:
- Analysis of enzyme activity using standard biochemical methods.
- Study conducted on intestinal tissue from 45 human embryos (4-22 weeks of intrauterine life).
- Enzymes examined included DPP IV, APM, APA, GGT, BBEP, ALP, ACP, AMP, ATP, saccharose, lactase, and trehalase.
Main Results:
- Protease activity, notably DPP IV, was detected early (pre-week 8) on the primitive intestinal epithelium.
- Following villus and crypt formation (post-week 9), high protease activity persisted in the differentiating microvillous zone.
- Disaccharidase and phosphatase activity (e.g., ALP, AMP) appeared after week 12 in the developing brush border.
Conclusions:
- Brush border enzyme expression in the human embryonic intestine follows a specific developmental sequence.
- Proteases, particularly DPP IV, are among the earliest enzymes to exhibit significant activity.
- The differentiation of enterocytes and the formation of the brush border are critical for the establishment of digestive enzyme functions.
Abstract:
Standard methods were used for the study of the activity of brush border enzymes in the epithelium of the intestine of 45 human embryos aged from 4 to 22 weeks of the intrauterine life. Enzymes of the peptidase group (DPP IV, APM, APA, GGT, BBEP), of the phosphatase group (ALP, ACP, AMP, ATP), and of the disaccharidase group (saccharose, lactase, trehalase) were studied. In the embryonal developmental period (to week 8), the activity of proteases was mainly detected on the luminal surface of the primitive pseudostratified columnar epithelium of the intestine anlage. The highest activity was displayed by DPP IV. In the period from the 8th week, villi are formed from the duodenum up to the ileum. After week 9, differentiation of Lieberkühn crypts was observed. The activity of proteases was very high (DPP IV especially) in the differentiating microvillous zone of primitive enterocytes. Gradient of apex-base activity of the villus was maximal on the apex of villi. After week 12 of the intrauterine life, the activity of disaccharidases ALP and AMP occurs in the differentiating brush border, and a low activity of BBEP of the protease group is present.