Crypt fission peaks early during infancy and crypt hyperplasia broadly peaks during infancy and childhood in the small intestine of humans

Background: Postnatal growth of the small intestine occurs by crypt hyperplasia and by the less recognised mechanism of crypt fission. How the small intestine grows is largely extrapolated from animals and is poorly described in humans. Aim: To investigate crypt fission and crypt hyperplasia as mechanisms of intestinal growth in humans. Patients and Methods: Proximal intestinal samples were taken from 3 neonates at surgical, anastomosis, and duodenal biopsies were taken at endoscopy from 16 infants (mean age 0.7, range 0.3-1.7 years), 14 children (mean age 7.9, range 2.4-16.2 years), and 39 adults. Morphometric measures of villous area, crypt length (measure of crypt hyperplasia), and percentage of bifid crypts (measure of crypt fission) were assessed by a microdissection technique. Results: Mean crypt fission rates in neonates, infants, children, and adults were 7.8%, 15%, 4.9%, and 1.7%, respectively. In particular, crypt fission peaked at 18% in 5 infants from 6 to 12 months of age. Mean crypt length was 123 mu m in neonates, 287 mu m in infants, 277 mu m in children, and 209 mu m in adults. Thus, crypt hyperplasia had a broad peak during infancy and childhood. Conclusions: We conclude that crypt fission was present predominantly during infancy, and crypt hyperplasia occurred during both infancy and childhood.