Role of Interleukin-1β in Acute Inflammation and Graft Death After Cell Transplantation to the Heart

Abstract

Background— Poor survival of grafted cells is a major factor hindering the therapeutic effect of cell transplantation; however, the causes of cell death remain unclear. We hypothesized that interleukin-1β (IL-1β) might play a role in the acute inflammatory response and graft death after cell transplantation and that inhibition of IL-1β might improve graft survival. Methods and Results— 14 C-labeled male skeletal muscle precursor cells were implanted into female mouse hearts by direct intramuscular injection. The amount of 14 C-label provides an estimate of the surviving cell number, whereas the amount of male-specific Smc y gene measured by polymerase chain reaction indicates the total (surviving+proliferated) number of donor-derived cells. At 10 minutes after implantation, 44.8±2.4% of the grafted cells survived and this steadily decreased to 14.6±1.1% by 24 hours, and to 7.9±0.6% by 72 hours (n=6 in each point). Proliferation of the surviving cells, which began after 24 hours, resulted in an increase in the total cell number from 15.5±0.8% at 24 hours to 24.4±1.6% at 72 hours. Acute inflammation was prominent at 24 hours and was reduced by 72 hours, in parallel with IL-1β expression. Administration of anti-IL-1β antibody improved graft survival at both 24 (25.6±1.6%) and 72 hours (14.8±1.1%) and resulted in a 2-fold increase in the total cell number at 72 hours (45.8±2.4%). The effects of IL-1β inhibition corresponded with a reduced inflammatory response. Conclusion— IL-1β is involved in acute inflammation and graft death after direct intramyocardial cell transplantation. Targeted inhibition of IL-1β may be a useful strategy to improve graft survival.