Effect of Human Pregnancy-Specific β-Glycoprotein on Blood Cell Regeneration After Bone Marrow Transplantation

Abstract

Pregnancy-specific β1-glycoprotein (PSG) is composed of a family of highly homologous proteins initially isolated from human placenta and pregnancy serum. Recent studies showed that PSGs are also present in a number of ectopic sites, including uncultured peripheral blood and bone marrow cells. This report aims at studying the in vivo effect of the PSGs on murine hematopoiesis. The profile of recovery of blood cells after transplantation of viable nucleated bone marrow cells in 7-irradiated mice with and without the administration of the purified human protein was studied. Five groups of mice were given 0.1 μg human serum albumin, 0.1 μg IL6, 1 μg PSG, 10 μg PSG, and 50 μg PSG, respectively, per mouse per day consecutively for 20 days. The mice were bled once every 2 days, and the platelet and WBC counts were determined using a Nebauer hemacytometer (Hausser Scientific, Buffalo, NY). The recovery of platelet count after bone marrow transplant was much faster in mice receiving 1 μg PSG/day than in animals in any other group. On Day 20 post-transplant, the platelet count of animals in this group reached 178,600 ± 15,759/μl (mean ± standard deviation) which was significantly (P < 0.05) higher than that of any other group. On Day 26, the platelet count reached a low normal value of 190,844 ± 6,380/μl with a range of 185,420–200,500/μl. This value was 3-fold higher than that of the control group (68,600 ± 15,486/μl in the human serum albumin group). Mice given 1 μg or 10 μg PSG/day also had their WBC count recover significantly faster and achieved a normal value (12,440 ± 3,680/μl for the 1-μg PSG group, and 12,154 ± 3,016/μl for the 10-μg PSG group) within the experimental period. On the other hand, the controls, or mice given 50 μg PSG/day did not recover as rapidly and did not achieve a normal WBC count within the experimental period. These results suggest that human placental PSGs enhance platelet and WBC recovery after bone marrow transplant.