Permeability of the mouse zona pellucida: a structure-staining-correlation model using coloured probes

Abstract

Coloured molecular probes of diverse molecular structure were used to define the permeability of the zona pellucida of preimplantation mouse embryos. The molecular characteristics examined were: electric charge, the size of conjugated aromatic groups and the hydrophilic-lipophilic character, all of which can be described numerically. It was hoped that definition of the types of compound able to cross the zona pellucida would contribute to identification and understanding of potential maternal--embryonic signals. The staining pattern of 51 dyes in unfertilized and fertilized one-cell eggs was recorded and 16 dyes were subsequently used to test two-, four- and eight-cell embryos further, to establish whether the permeability of the zona pellucida altered with developmental age. Four different staining patterns were observed that directly correlated with the numerical parameters of the probe but were independent of developmental age. The size of the conjugated system and the hydrophilic-lipophilic balance of the probe were important in determining its interaction with the zona pellucida and embryo whereas electric charge appeared to have little influence. The resulting model is useful for predicting likely interactions between chemically defined molecules and biological entities and suggests that most biologically active molecules and metabolites can pass through the zona pellucida unhindered and enter the embryo with ease.

Insight into PreImplantation Factor (PIF*) Mechanism for Embryo Protection and Development: Target Oxidative Stress and Protein Misfolding (PDI and HSP) through Essential RIPK Binding Site

“…While maternal-derived compounds still can reach the embryo, access through the embryo cell membrane is more limited. It favors transfer of lipophilic, cationic and large conjugated system compounds [1]. Maternally-derived or embryo-secreted trophic compounds were previously reported.…”

Embryo‐Maternal Communication in Bovine – Strategies for Deciphering a Complex Cross‐Talk

“…Therefore, the size of a signal molecule is not limiting for its passage, but rather its hydrophobic characteristics. Turner and Horobin (1997) demonstrated that extremely hydrophilic proteins with low van der Waals forces are not able to penetrate the EEM, while lipophilic proteins with high van der Waals forces get enriched in the matrix and proteins with a slightly lipophilic or hydrophilic character and low van der Waals forces easily penetrate the matrix. Consequently, the simple detection of a protein in one compartment, embryonic or maternal, does not directly mean that it is able to penetrate the EEM and to act as a signal in the embryo‐maternal communication.…”

Structural Dynamics and Function of Early Embryonic Coats

“…Attempts have recently been made to study the physicochemical basis of this selectivity systematically in the mouse, defining molecular parameters of the permeating substances (like hydrophilic or lipophilic properties, the conjugated bond number) that may be of a predictive value. Although differences in permeation properties are noted, it became clear in those model experiments that most biologically active molecules and metabolites can pass through the coats of early mouse embryos largely unhindered [Turner and Horobin, 1997]. On the basis of the modifications of the coats that occur particularly in blastocyst stages in various animals (as discussed above) one should be cautious with rapid extrapolation to other species, and from one stage to the other, and also from in vitro experiments to the in vivo situation.…”