ABSTRACT
Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that is known to play an important role in blastocyst implantation. The putative action of LIF in the regulation of uterine function has been examined using mid-secretory stage monkey endometrial stromal cells cultured on rat-tail collagen type I and treated with recombinant human LIF (rhLIF) or immunoneutralized LIF (in LIF) under serum-free condition. Long-term ovariectomized rhesus monkeys (n=8) underwent simulation of their menstrual cycles with steroid hormones and endometrial tissue samples were collected on cycle day 18; stromal cells were isolated and grown in primary culture on three-dimensional collagen matrix. Significant decline in cellular protein synthesis (P < 0.01) and cell proliferation index (P < 0.05) was observed in cells with increasing doses (0-1000 ng/ml) of rhLIF under serum-free in vitro condition. JAK1 expression in cultured cells increased (P < 0.01) in response to rhLIF as revealed from Western blot and confocal laser scanning microscopic examination, STAT1 and STAT2 expressions were unchanged, while pSTAT3 expression increased (P < 0.01) with increased concentration of rhLIF in culture medium. Autophosphorylation of JAK1 in endometrial stromal cells showed no change with increasing concentration (0.01 to 100 ng/ml) of rhLIF in vitro, but significant (P < 0.05) increase was observed with the time of exposure to rhLIF. Immunoneutralization of LIF or no addition of rhLIF to cultured cells led to significant (P < 0.01) increase in stromal cell proliferation index and significant (P < 0.01) decrease in the level of JAK1 and its autophosphorylation as compared to cells exposed to rhLIF alone. From the present set of experiments we conclude that rhLIF affects the physiological behaviour of monkey mid secretory stage endometrial stromal cells in vitro via the JAK-STAT signaling pathway.