Human milk induces fetal small intestinal cell proliferation - involvement of a different tyrosine kinase signaling pathway from epidermal growth factor receptor

Abstract

Breast milk has non-nutritional protective effects on recipient infants. It has been speculated that bioactive substances present in human milk have important roles in protecting infants. However, the mechanisms by which such substances protect newborns are unclear. Therefore, we analyzed the growth-promoting activity of human milk and the intracellular signaling mechanism thereof using human fetal small intestinal (FHS 74 Int) cells. Epidermal growth factor (EGF) stimulated the proliferation of these cells. However, this stimulation was less effective than that of aqueous milk (5% vol/vol). The bioactivity of human milk was heat stable but protease sensitive. EGF receptor tyrosine kinase inhibitor did not repress the milk-induced growth-promoting effect on fetal small intestinal cells. Regarding the intracellular signaling pathway, the milkinduced cell proliferation pathway was tyrosine kinase dependent but was neither mitogen-activated protein (MAP) kinase nor phosphatidylinositol-3 (PI-3) kinase dependent. On the other hand, EGF-induced cell proliferation was tyrosine kinase, MAP kinase, and PI-3 kinase dependent. Rapid tyrosine phosphorylation of several intracellular proteins was detected after milk stimulation. Furthermore, the time course of phosphorylation induced by milk was different from that induced by EGF. The sizes of the proteins phosphorylated in response to milk were different from those of the Shc proteins phosphorylated in response to EGF. These results suggest that human milk induces fetal intestinal cell proliferation through a unique tyrosine kinase pathway different from the EGF receptor signaling pathway.

Postnatal Epithelial Growth of the Small Intestine in the Rat Occurs by Both Crypt Fission and Crypt Hyperplasia

“…Our data show that a range of growth factors and their receptors are expressed in infant rats as shown by their specific mRNA (both growth factors and receptors). This would explain why it is possible to induce a growth response either in vitro or in vivo with a variety of growth factors given in pharmacologic doses (1,2,(17)(18)(19)(20)(21)(22)(23). Our data did not show predominance of expression of any 1 conventional growth factor or their receptor in infant rats at an age when crypt fission is high.…”

“…A recent study by Mandir et al (16) investigated crypt fission by the same microdissection technique in rats at 3,4,6,9,12,18,26, and 48 weeks of age and found that crypt fission was 4.6% and 8.4%, respectively, at 3 and 6 weeks of age, before declining steadily to 1.5% at 48 weeks of life. In contrast to this study, our study investigated rats beginning at 7 days of life and therefore found an earlier broad peak of crypt fission of 10.5% at day 11 of life, but which had a broad tail until day 25 of life.…”

Cell-based models to test the effects of milk-derived bioactives

“…For studies of human milk-derived bioactives, the small intestinal FHs 74 Int. cell line has been widely used as a model (Ichiba et al, 1992;Kawamura et al, 1994;Wagner et al, 1998;Hirai et al, 2002;Takeda et al, 2004). We have shown that these small intestinal cells represent a very sensitive model for milk-derived bioactives (Purup et al, 2007).…”

Host Factors in Amniotic Fluid and Breast Milk that Contribute to Gut Maturation

“…After fetal maturation, human milk becomes the foodstuff essential for the neonate's survival, and yet, it is more than its nutritional component for it has the capacity to stimulate cell growth and repair and provide immune protection and enhance immunocompetence [28, 29, [39][40][41][42][43][44][45]. Human milk contains numerous growth modulators [41,45,46] [66][67][68], and granulocyte colony-stimulating factor (CSF) [69], to name but a few.…”

“…As summarized in Table 2, numerous bioactive substances in human milk, not found in formulas, are known to stimulate GI mucosal proliferation in adult and animal models and facilitate maturation and closure of the neonatal GI tract from the outside milieu [3, 39,40,66,72,115,116]. The physiological significance of milk-borne growth factors is widely accepted and supported by the following:…”