Chronic vascular rejection: histologic comparison between two murine experimental models.

Area of Science:

• Transplantation immunology
• Vascular biology
• Surgical pathology

Background:

• Chronic vascular rejection (CVR) is a significant challenge in organ transplantation.
• Previous development of a murine orthotopic aortic allograft model for CVR studies.
• Introduction of human arterial grafts into SCID/Beige mice for CVR research.

Purpose of the Study:

• To compare the pathological differences in chronic vascular rejection lesions between two experimental models.
• To evaluate the suitability of human arterial grafts versus murine aortic allografts in mimicking clinical CVR.

Main Methods:

• Two models were used: murine aortic allografts (C57BL/6 to DBA/2) and human superior mesenteric artery grafts into SCID/Beige mice reconstituted with human spleen cells.
• Grafts were analyzed at 35 days post-transplantation using histology and morphometry.
• Intimal thickening was quantified via transverse sections.

Main Results:

• Both models exhibited typical CVR lesions, including neointimal thickening, T-cell infiltration, and smooth muscle cell (SMC) proliferation.
• A key difference observed was the disappearance of SMC in the media of mouse aortic allografts, whereas the media remained intact in human arterial transplants.
• This indicates distinct pathological responses in the vascular wall.

Conclusions:

• The findings suggest that human arterial grafts in SCID/Beige mice provide a more accurate representation of clinical chronic vascular rejection pathology.
• The conservation of the media layer in human grafts aligns with observations in clinical organ transplantation.
• The murine aortic allograft model, while useful, may not fully recapitulate the vascular wall changes seen in human CVR.