In vivo visualization of uterine mast cells by two-photon microscopy

Abstract

Transgenic mice expressing fluorescent proteins in specific cell populations are widely used for the study of in vivo behavior of these cells. We have recently reported that uterine mast cells (uMCs) are important for implantation and placentation. However, their in vivo localization in uterus before and during pregnancy is unknown. Herein, we report the direct observation of uMCs in vivo using doubletransgenic C57BL/6J Mcpt5-Cre ROSA26-EYFP mice with high expression of enhanced yellow fluorescent protein in MC protease 5 (Cma1 (Mcpt5))-expressing cells by intravital two-photon microscopy. We were able to monitor MCs live in utero during the murine estrous cycle and at different days of pregnancy. We demonstrated that uMCs accumulated during the receptive phase of the female (estrus) and persisted in large numbers at early pregnancy stages and around mid-gestation and declined in number in non-pregnant animals at diestrus. This intravital microscopy technique, including a custom-made microscope stage and the adaption of the surgical procedure, allowed the access of the uterus and implantations for imaging. The introduced application of intravital microscopy to C57BL/6J-Mcpt5-Cre ROSA26-EYFP mice offers a novel and powerful in vivo approach to further address the evident relevance of uMCs to reproductive processes with obvious clinical implications.

Cellular Regulation of the Uterine Microenvironment That Enables Embryo Implantation

“…They remain high in numbers if pregnancy establishes. By using in vivo microscopy, we could confirm that uMCs are present in abundance in the uterus of pregnant C57BL/6J Mcpt5-Cre ROSA26-EYFP mice (14). They are localized in close proximity to blood vessels (13, 14).…”

“…They are present in high numbers at specific sites along the non-pregnant uterus as shown in vivo (12). The same is true for uterine mast cells (uMCs) that differ enormously from MCs found in other tissues (13, 14), and for uterine macrophages that are crucial in modulating later trophoblast function (15). Some immune cells present in the uterus fluctuate in number through the different phases of the menstrual cycle in human beings or the estrus cycle in mice.…”

Mast cells—Good guys with a bad image?

“…132 In addition, uMCs are able to influence angiogenesis, decidual remodeling, 48,133,134 and control uterus contractions, 127,135,136 processes that are important for giving birth. 118 Not only the total number of MCs, but also the histamine content of the rat uterus changed throughout the cycle, increasing before ovulation, reaching the maximum during ovulation and decreasing after implantation of the blastocyst. MCs remain present in large numbers at early pregnancy stages and around mid-gestation in mice but declined in number in non-pregnant animals at diestrum.…”

“…[118][119][120][121][122] As in the rest of the body, these MCs are very often located near blood vessels [123][124][125] or myometric smooth muscle cells. [118][119][120][121][122] As in the rest of the body, these MCs are very often located near blood vessels [123][124][125] or myometric smooth muscle cells.…”

Uterine natural killer cells: supervisors of vasculature construction in early decidua basalis

“…This amyloid deposition process may occur in a transient fashion, making detection by traditional histological techniques difficult. The continued adaptation and use of live imaging systems to address questions surrounding vascular, immune cell, and trophoblast interactions in mice and in human cell cultures hold great promise for refining, modifying, and improving current understanding of the maternal-fetal interface (Schmerse et al 2014).…”