The Impact of Sex Steroids Inhibiter on Thymic Function Following Hematopoietic Stem Cell Transplantation

Objective

To evaluate the impact of luteinizing hormone-releasing hormone (LHRH) on the protection of thymic function after allogenic hematopoietic stem cell transplantation (allo-HSCT).

Methods Established model of allogenic murine HSCT (C₅₇BL/6→BALB/c). The severity of acute graft-versus-host-disease (GVHD) was assessed by a clinical scoring system that incorporates five clinical parameters: weight loss, posture, activity, fur texture and skin integrity. The intra-cellular levels of interferon-γ (INFγ), tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β) in thymocyte were analyzed by protein array and thymic function was evaluated by quantification of signaljoint TCR rearrangement excision circles (sjTRECs).

Results Recipients in group A (allogenic mice), B( allogenic LHRH castrated-mice) and C (syngenic mice) all attained hematopoiesis reconstitution. White blood cell counts of mice in groups A, B and C were over 1.0×10⁹/L on day (10.60±1.34), day (9.40±0.55) and day (9.40±0.89), respectively. There was no significant difference among the time of hematopoiesis reconstitution in three groups. The time of acute GVHD occuring was on day +11±0.5 and +14±0.5 posttransplantation, respectively, in groups A and B, and all mice had acute GVHD with the incidence of 100% in groups A and B. The average scores of acute GVHD in groups A and B were (1.56±0.51) and (0.92±0.49), respectively. Acute GVHD scores in group A was significantly higher than that in group B (P=0.000). The levels of INFγ, TNFα and IL-1β in control groups were 1.67±1.76 ng/ml, 1.69±1.07 pg/ml and 5.55±3.56 pg/ml, respectively. The levels of INFγ in groups A, B and C were (10.74±2.55) ng/ml,(6.81±2.33) ng/ml and (5.52±3.96) ng/ml, respectively. The levels of TNFα were (7.51±2.89) pg/ml, (4.30±0.63) pg/ml and (3.36±2.31) pg/ml, respectively. The levels of IL-1β were (25.83±8.91) pg/ml, (19.33±3.03) pg/ml and (11.94±4.00) pg/ml, respectively. There were significant differences in the levels of cytokines between group A and the control group (P=0.000, 0.000, 0.000). The levels of cytokines in group B were significantly higher than those of control group (P 0.010,0.037,0.000). The levels of INFγ in group C were significantly higher than those of the control group (P=0.044). Among groups A, B and C, there were significant differences in the levels of INFγ, TNFα and IL-1β (P=0.001,0.000,0.000). The levels of INFγ and TNFα in group A were significantly higher than those in group B (P=0.041,0.013). The levels of INFγ, TNFα and IL-1β in group A were significantly higher than those in group C (P=0.009, 0.002, 0.000). The analysis of linear regression showed that the average levels of INFγ paralled with aGVHD scores (r² 0.363,P=0.038). The average sjTRECs copies/1000 PBMNCs were (39.41±44.68) in the control group and (12.29±13.02), (58.01±71.82) and (19.61±14.59) in groups A, B and C, respectively. There was no significant difference in the multiple comparisons of peripheral blood levels of sjTRECs among these four groups (P=0.575).

Conclusion INFγ ATNFα and IL-1β might be involved in the damage to the thymus by acute GVHD. Sex steroid inhibitor can not only reduce the severity of thymic damage after allo-HSCT, but also reduce the severity of aGVHD and the mechanism might be associated with the reduction of intracellular levels of INFγ and TNFα in thymocyte.