Pulsed Application of the Stem Cell Mobilization Agent Plerixafor Attenuates the Development of Transplant Vasculopathy in a Murine Aortic Allograft Model

Background: Plerixafor known as hematopoietic stem cell mobilization agent increases the peripheral blood content of effector and regulatory T cells (Tregs) and hereby may have beneficial effects attenuating the development of cardiac allograft vasculopathy (CAV). Hence, the aim of the present study was to evaluate the impact of plerixafor on CAV in a murine aortic allograft model using different application procedures by a single dose, continuous, or pulsed application.

Method: Allogeneic donor aorta grafts (n = 8 per group) from C57BL/6 mice (H2b) were abdominally transplanted into CBA mice (H2k). The application of plerixafor was performed either continuously for 14 days using implanted small osmotic pumps [1 mg/kg/d] or by subcutaneous administration of a single dose [1 and 5 mg/kg] at day 1 after transplantation (Tx) or by pulsed injections of 1 mg/kg on days 1, 7, 14, and 21 after Tx, respectively. Altered cell distribution was monitored by FACS. Aortic grafts were evaluated for neointima development by EvG 30 days after Tx. In addition, immunofluorescence and intragraft gene expression analysis were performed.

Results: At day 14 after Tx, significantly less hematopoietic stem cells (HSCs) were found in the bone marrow of all plerixafor treated mice versus control; however, only in the pulsed application group significantly more HSCs were found in the peripheral blood on day 14 after Tx versus control (0.045% ± 0.002%; p < 0.01 [pulsed] vs. 0.0068% ± 0.002% [control]). The injection of plerixafor (single and pulsed) significantly elevated the fraction of Tregs in the blood compared with continuously plerixafor supply and the control, respectively. Intragraft gene expression analysis revealed clearly reduced IFNγ, E-selectin, ICAM-1 and Granzyme B but higher TGFβ pattern. Measurements of the allografts luminal occlusion on day 30 after Tx showed significant less obliteration in the pulsed treated group versus control (33.65% ± 8.84 vs. 53.13% ± 12.41) going along with decreased CD4+ T cell allograft infiltration on day 30.

Conclusion: We assume that the pulsed application of plerixafor leads to potent stem cell mobilization and hereby attenuate the chronic rejection in murine aortic allografts. The injection of repeated low dose plerixafor seems to be more advantageous compared with continues application via pump or a single dose injection. Reduced inflammation-determined mediators but increased TGFβ may reflect immune modulating effects by plerixafor.

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Artikel online veröffentlicht:
28. Januar 2023