Patterns of Growth Factor Receptor Expression Correlate with Concentrations of Their Respective Growth Factors in Mouse Milk during Lactation

Abstract

Growth factors (GF) are crucial components in breast milk contributing to regulation of neonatal small intestinal maturation. Concentrations of GF change during the lactation period, but there is limited data on expression of their receptors in the neonatal small intestine during this time. C57BL/6 mice were used as a model to explore expression patterns for milk GF receptors. Small intestines of mice pups were collected at regular intervals during fetal life and up to postnatal day (PD) 60. Gene expression of GF receptors (EGF, TGF‐β family, IGF, VEGF, PDGF, HGF, FGF, NGF and EPO receptors), were determined by qPCR. All receptors showed significantly greater expression in the fetus and a sharp decrease after PD14 [figure 1]. At this time mouse pups start to ingest solid food. Another experiment to avoid a solid food effect was therefore conducted by removing pups when dams were given solid foods. The results showed the same trend – decreasing greatly from PD14, demonstrating that theexpressionof GF receptors was not related to solid food intake. To explore whether thisexpression patternwascorrelated with concentrations of the corresponding GF in the milk, milk samples were collected regularly from PD0 to PD21, and GF were analyzed by ELISA. TGF‐β and VEGF concentrationswere found to show trends similar to their receptor changes in the small intestine, whereas EGF and IGF‐1 reached their maximum level during mid‐lactation. In conclusion, growth factor receptors in the small intestine of mouse pups show a sudden decrease after PD14, which is not caused by solid food intake. Growth factors in milk may regulate their respectivereceptors through different mechanisms due to their different functions during early development of the small intestine.