Chronic rejection in vascularized composite allografts

Area of Science:

• Immunology
• Transplantation Medicine
• Pathology

Background:

• Chronic rejection is a significant challenge in solid organ transplantation.
• Vascularized composite tissue allotransplantation (VCA) presents unique challenges in understanding chronic rejection.
• Limited data exists on chronic rejection in human VCA cases.

Purpose of the Study:

• To outline key issues in chronic rejection of VCA.
• To identify pathological features indicative of VCA chronic rejection.
• To review current understanding and proposed mechanisms.

Main Methods:

• Review of existing literature on VCA chronic rejection.
• Analysis of reported pathological findings in animal models and human VCA transplants.
• Synthesis of proposed immunologic and non-immunologic mechanisms.

Main Results:

• Chronic rejection features observed in animal models and limited human VCA transplants (knee, hand).
• Consistent finding of transplant vasculopathy with intimal hyperplasia, leading to graft dysfunction/loss.
• Other reported features include tertiary lymphoid follicles, graft fibrosis, and edema; antibody-mediated rejection is not conclusively established.

Conclusions:

• Chronic rejection in VCA is not well-defined, similar to solid organ transplantation.
• Transplant vasculopathy is a primary indicator of chronic VCA rejection.
• Intimal hyperplasia, detectable by advanced imaging, is a key component of transplant vasculopathy.