LEUKEMIA INHIBITORY FACTOR IN HUMAN ENDOMETRIUM THROUGHOUT THE MENSTRUAL-CYCLE

Leukaemia inhibitory factor (LIF) is a pleiotropic cytokine previously demonstrated to be essential for blastocyst implantation in mice. Sam ples of endometrium from normal cyclic women throughout the menstrual cycle were tested for LIF messenger RNA by Northern blot analysis and the corresponding protein was localised immunohistochemically with a p olyclonal antibody to LIF. Western blot analysis detected a 45 kDa LIF protein in an extract from late secretory tissue. The expression of L IF messenger RNA transcript was detected only during the mid and late secretory phases of the cycle after day 20. Immunoreactive LIF was obs erved in all human endometrial samples. In the stroma there were moder ate to high levels of immunohistochemical staining throughout the cycl e with considerable variation between individuals but no cyclical vari ation. Epithelial staining, both luminal and glandular, was also prese nt throughout the cycle but this was relatively low in the proliferati ve phase and strongest in the mid to late secretory phases. The marked cyclical changes of immunoreactive LIF in the human endometrial epith elium suggest a paracrine/autocrine role for LIF in endometrial functi on. Whether LIF is essential for implantation in the human remains to be established.