EFFECT OF RECOMBINANT CANINE STEM-CELL FACTOR, A C-KIT LIGAND, ON HEMATOPOIETIC RECOVERY AFTER DLA-IDENTICAL LITTERMATE MARROW TRANSPLANTS IN DOGS

We studied the effect of recombinant canine stem cell factor (rcSCF) o n hematopoietic recovery, incidence of graft failure, graft-vs.-host d isease (GVHD), and survival after marrow transplantation from dog leuk ocyte antigen (DLA)-identical canine littermates. Ten animals received 100 pg rcSCF/kg/day b.i.d. by subcutaneous injection on days 2 throug h 10 after 920 cGy total body irradiation and transplantation of a mea n of 3.7 x 10(8) marrow cells/kg body weight. None of the dogs receive d GVHD prophylaxis. All animals showed hematopoietic engraftment. The median number of days to achieve 1000 neutrophils/mm(3) was 9; 100 mon ocytes/mm(3) were reached after 15 days, 500 lymphcytes/mm(3) after 21 days, and 20,000 platelets/mm(3) after 16 days. One animal developed GVHD involving skin, gut, and liver and died of bacterial pneumonia 21 days after transplantation. The remaining nine dogs were observed for a median of 37 days (range 29-84 days) posttransplantation until they were killed. Facial edema was seen in three dogs during the first 2-3 days of rcSCF administration. These results show that within the limi ts of this study it appears to be safe to administer SCF after DLA-ide ntical littermate marrow transplants in dogs. Comparison with previous ly published data in the same model showed that neutrophil and monocyt e recovery was significantly faster in dogs receiving SCF treatment co mpared with dogs without growth factor treatment (recovery to achieve 1000 neutrophils/mm(3): median 9 days vs. 13 days, p = 0.002; recovery to 100 monocytes/mm(3): median 15 days vs. 105 days, p = 0.0002). Oth erwise, no significant differences were seen. Results obtained with SC F treatment were similar to those previously obtained in the same mode l with recombinant human granulocyte colony-stimulating factor (rhG-CS F) treatment except that recovery of lymphocytes to 500/mm(3) appeared to be more rapid in G-CSF-treated dogs (median 15 days vs. 21 days, P = 0.03).