The Lactocrine Hypothesis and Laser Microdissection: Evaluating Tissue-Specific Effects of Milk-Borne Factors on Gene Expression in the Neonatal Porcine Uterus

Abstract

In the pig, development of the uterus begins in utero and is promoted postnatally via communication of milk-borne bioactive factors (MbFs) that advance development of neonatal somatic tissues. The passage of MbFs from mother to neonate is termed lactocrine signaling. The porcine endometrium is estrogen receptor (ESR1) –negative and relaxin (RLX) receptor (RXFP1) –positive at birth (postnatal day 0 = PND 0). Expression of stromal ESR1 by PND 2 is directly associated with the onset of uterine gland genesis. Data for RLX in milk suggests that a critical lactocrine programming window for uterine development exists between birth and PND 2. Developmental disruption between PND 0 and 14 reduces uterine capacity in the adult. The extent to which lactocrine signaling affects organizationally critical stromal-epithelial interactions and resulting morphological changes is unknown. Laser microdissection (LMD) is a tool that can be used to physically separate specific cell or tissue types from histological preparations for use in molecular analysis. However, application of LMD for such purposes presents technical challenges and optimization of these factors is necessary to obtain robust data. Here, objectives are to i) review aspects of uterine development, ii) establish a protocol for the use of LMD in evaluating stromal-epithelial interactions that drive uterine development and iii) determine the effects of nursing for 48 h from birth on endometrial compartment-specific ESR1, RXFP1, vascular endothelial growth factor (VEFGA) expression and uterine morphology as seen on PND 2 and PND 14.