In-depth multi-level analysis of the neovascularization and integration process of a non-vascularized rectus fascia following intestinal transplantation

Introduction: Failure to close the abdominal wall after intestinal (ITx) and multiviseral transplantation (MvTx) remains a challenge, associated with increased morbidity and mortality. An attractive method is the use of non-vascularized rectus fascia (NVRF) in which both layers of the abdominal rectus fascia are used as an inlay patch without vascular anastomosis, with excellent short-term outcomes. The aim of our study is to provide an in-depth multi-level analysis (ranging from clinical, radiological, histological, contrast-enhanced microCT (CECT) to immunological evaluation) of the neovascularization and integration process of the NVRF based on three consecutive cases following ITx. Methods: Three patients underwent a NVRF transplantation in combination with an ITx between September 2019 and September 2022 at the Leuven Intestinal Failure and Transplant unit. A retrospective analysis was performed. Ethical approval for reporting was obtained (S67453). Results: The first patient was a 49-year old female who received a NVRF during combined liver-ITx and had an uneventful recovery. At 1 month, ultrasound doppler confirmed neovascularization of the graft. Five months later, at the time of continuity surgery, the donor fascia was macroscopically well integrated. H&E staining on biopsy confirmed the good integration of the graft with intense fibrotic reaction around the NVRF without rejection. CD31-staining showed neovascularisation on the interface with the native fascia. CECT analysis revealed the presence of microvasculature enveloping the donor fascia as well as penetrating the graft at the interface with the native fascia; Fig. 1a: sagittal view of CECT image, red arrow indicating blood vessels in the NVRF (blue line). Fig. 1b: 3-dimensial render of neovascularisation. The second patient was a 51-year old male who received a NVRF after a MvTx. Two weeks later, during a re-operation the fascia showed macroscopic neovascularization. Since the skin could not be closed, a VAC-system was placed on top of the fascia and secondary closure was obtained. The patient died six months post-transplant from a metastasized abdominal mesothelioma. The third patient was a 31-year old male who underwent MvTx. Eleven days post-transplant and after re-operation for intra-abdominal collections, primary closure could not be attained and a non-ABO-matched third party fascia was used to cover the defect. Six days after NVRF transplant, anti-A natural and immune antibodies were slightly increased suggesting the presence of de-novo specific antibodies against the third party fascia. Twelve days later, the patient died of an acute rupture of a mycotic aneurysm of the aorta tube. At re-intervention, the fascia looked macroscopically intact. Conclusion: We showed in this case series additional evidence of the neovascularization and integration, by fibrotic reaction, of donor NVRF after intestinal transplantation