# Longitudinal Correlations between Molecular Compositions of Stratum Corneum and Breast Milk Factors during Infancy: A Prospective Birth Cohort Study

## TL;DR

This study explores how breast milk factors correlate with the development of infants' skin barrier over time.

## Contribution

The study is the first to examine longitudinal correlations between breast milk factors and stratum corneum molecular components during infancy.

## Key findings

- Breast milk factors correlated with stratum corneum molecular components at different ages and skin depths.
- The correlations suggest breast milk influences the maturation of the skin barrier in infants.
- Findings may enhance understanding of skin diseases linked to barrier abnormalities.

## Abstract

Breast milk contains numerous factors that are involved in the maturation of the immune system and development of the gut microbiota in infants. These factors include transforming growth factor-β1 and 2, immunoglobin A, and lactoferrin. Breast milk factors may also affect epidermal differentiation and the stratum corneum (SC) barrier in infants, but no studies examining these associations over time during infancy have been reported. In this single-center exploratory study, we measured the molecular components of the SC using confocal Raman spectroscopy at 0, 1, 2, 6, and 12 months of age in 39 infants born at our hospital. Breast milk factor concentrations from their mothers’ breast milk were determined. Correlation coefficients for the two datasets were estimated for each molecular component of the SC and breast milk factor at each age and SC depth. The results showed that breast milk factors and molecular components of the SC during infancy were partly correlated with infant age in months and SC depth, suggesting that breast milk factors influence the maturation of the SC components. These findings may improve understanding of the pathogenesis of skin diseases associated with skin barrier abnormalities.