Biological, mechanical, and immune changes in an abdominal rectus fascia transplant model in rats

Primary abdominal wall closure after intestinal and multivisceral transplants remains a challenge. Avascular transplant of the abdominal rectus fascia (TxARF) has emerged as an alternative to reduce postoperative morbidity and mortality. This study aimed to evaluate tissue and immunological responses to TxARF in a rat model without immunosuppression.

A total of 34 TxARFs were performed in rats (17 isogenic [ISO] and 17 allogeneic [ALLO]), with recipients sacrificed at 30 and 120 days after surgery. Serum and graft samples were analyzed for donor-specific antibodies (DSAs), elasticity, cellular analysis by flow cytometry, histopathology, and immunohistochemistry for CD3+ cells.

Muscle fiber loss was observed at 30 days, with collagen content significantly higher in ALLO (55.97 ± 3.68) and ISO (33.13 ± 3.85) groups than controls (3.78 ± 0.47) (P <.0001). The lateral portions of the grafts showed more large blood vessels, whereas the medial areas had small vessels. The ALLO group exhibited increased resistance to stretching and elasticity loss. Despite the lack of immunosuppression, CD3+ levels in all groups were similar to controls, with only 1 animal showing a positive DSA response.

Long-term changes include muscle fiber replacement with fibrosis and loss of elasticity, especially in the alloreactive group. No significant immune response occurred, confirming the fascia's low immunogenicity.