Effects of heterologous hematopoietic cytokines on in vitro differentiation of cultured porcine inner cell masses.

An exogenous supply of hematopoietic cytokines is essential for maintaining murine embryonic stem (ES) cells in a proliferative yet undifferentiated state. Recently, it was demonstrated that hematopoietic cytokines utilize the gp130 signal transduction pathway to maintain this phenotype, although their involvement toward maintaining porcine ES cell pluripotency has not been established. Therefore, the objective of this study was to determine the effectiveness of several heterologous hematopoietic cytokines at maintaining the isolated porcine inner cell masses (pICM) in an undifferentiated state. pICMs (day 7) were isolated by immunosurgery and cultured 4 days in one of six treatments: control medium, human leukemia inhibitory factor (hLIF; 1,000 mu/ml), human interleukin-6 (hIL-6; 100 ng/ml), hIL-6 + hIL-6 soluble receptor (hIL6 + sR; 100 ng/ml + 2.5 micrograms/ml), human oncostatin M (hOSM; 100 ng/ml), or rat ciliary neurotrophic factor (rCNTF; 100 ng/ml). All cytokines were prepared in Dulbecco's Modified Eagle's Medium/Ham's F-10 (1:1)-based medium. Morphology of pICMs was evaluated on a scale of 1 (fully undifferentiated) to 5 (fully differentiated) at 24-h intervals. Differentiation was significantly lower on day 2 for rCNTF vs. hLIF cultured pICMs (2.07 +/- 0.15 vs. 2.70 +/- 0.16; P < 0.05). Furthermore, addition of rCNTF gave the lowest overall mean differentiation score (2.53 +/- 0.15). However, none of the cytokines significantly delayed differentiation over controls for the 4-day culture period (P > 0.05). Since these heterologous cytokines were unable to inhibit differentiation, it is unlikely they will be beneficial towards isolating porcine ES cell lines under current conditions. Future work with homologous cytokines and dose effects may prove more beneficial.