Enhancing effects of silkworm expressed recombinant human macrophage colony-stimulating factor on hematopoietic recovery of irradiation-injured mice

OBJECTIVE: To study the hematopoietic enhancing effects of recombinant human macrophage colony-stimulating factor (rhM-CSF) expressed in silkworm. METHOD: Balb/c mice were irradiated with sublethal dose of 60 Co gamma-rays and then administered intraperitoneally with silkworm expressed rhM-CSF (1000 U per individual for 7 days) in treatment group or with normal saline (for 7 days as well) in control group. The hematopoietic recovery of irradiation mice was observed by comparing peripheral white blood cell (WBC) counts, differential counts of WBC and bone marrow hematopoietic progenitor cell colony forming assay in soft agar at different time after irradiation. RESULTS: The total WBC counts (x 10(9)/L) of treatment group at day 15 and 20 after irradiation(3.42 +/- 1.20, 5.56 +/- 2.50, respectively) were significantly higher than those of control group (2.03 +/- 0.90, 3.72 +/- 2.30; both P < 0.05). On days 10, 15, 20, 25 and 30 after irradiation, the monocyte counts (x 10(9)/L) of treatment group (0.08 +/- 0.06, 0.16 +/- 0.10, 0.48 +/- 0.35, 0.47 +/- 0.21 and 0.33 +/- 0.17, respectively) were all significantly higher than those of control group (0.025 +/- 0.016, 0.05 +/- 0.04, 0.23 +/- 0.16, 0.33 +/- 0.19 and 0.17 +/- 0.13; all P < 0.05). On days 15, 20 and 25, the granulocyte count (X 10(9)/L) of treatment group (1.03 +/- 0.61, 2.18 +/- 1.19 and 3.28 +/- 1.09) were also higher than those of control group (0.62 +/- 0.37, 1.40 +/- 0.99 and 2.20 +/- 0.74; all P < 0.05). On day 9 after irradiation, the bone marrow CFU-GM yield of control group (19 +/- 11/10(6) cells) was significantly lower than that of treatment group (78 +/- 30/10(6) cells, P < 0.05). CONCLUSION: rhM-CSF expressed in silkworm could accelerate hematopoietic recovery in irradiated mice.