BACKGROUND: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. METHODS: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. RESULTS: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. CONCLUSION: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.

Background Intestinal transplantation (ITx) represents the only curative option for patients with irreversible intestinal failure. Nevertheless, its rejection rate surpasses that of other solid organ transplants due to the heightened immunological load of the gut. Regulatory T-cells (Tregs) are key players in the induction and maintenance of peripheral tolerance, suggesting their potential involvement in modulating host vs. graft responses after ITx. Thus, we investigated the association of Tregs with allograft outcomes in pediatric patients and in an experimental model of small bowel transplantation. Methods Treg frequency in human samples was analyzed by Flow cytometry (CD4+CD25highCD127-, blood samples) and immunohistochemistry (FoxP3, graft samples). Experimental allogenic-heterotopic small bowel transplantation was performed in rats and animals divided into 3 groups: non-immunosuppressant treatment, rapamycin (2 mg/kg), and tacrolimus (0.6 mg/kg) treatment. Acute cellular rejection (ACR) was diagnosed based on clinical and histological findings, graft gene expression of pro- and anti-inflammatory mediators assessed by RT-qPCR, serum IL-6 and IL-10 levels by Luminex, and Treg frequency analyzed by flow cytometry (CD4+CD25highFoxP3+). Results Blood samples from patients undergoing ACR exhibited a significant reduction in the Treg number compared to those with normo-functional grafts. Similarly, a diminished number of FoxP3+ cells was observed in mucosa samples with ACR. In the experimental model, rapamycin-treated animals displayed clinical and histological findings resembling those not receiving immunosuppression treatment. Notably, ACR correlated with a high CD8/CD4 ratio, loss of T-cell chimerism, mRNA upregulation of pro-inflammatory genes and diminished graft Treg frequency. In contrast, tacrolimus treatment prevented ACR and facilitate blood and graft Treg expansion. Remarkably, recipients who achieved Treg expansion within the graft remained free of ACR even after discontinuation of the immunosuppressant treatment and this phenomenon was associated with increased levels of serum IL-10. Conclusion Our clinical and experimental findings underscore the association between Treg frequency and graft rejection after ITx, advocating for strategies that promote their expansion within the gut mucosa to enhance long-term outcomes.

ABSTRACT Purpose: To mitigate ischemia-reperfusion injury (IRI) triggered in solid organ transplant procedures, we aimed to evaluate the effects of multi-organ abdominal ischemic preconditioning (MAIP) in the context of renal IRI. Methods: An experimental kidney transplant model was conducted. Rats were divided into three groups: an intervention free basal group from which physiological data was collected; a control group (CT), which consisted of transplanted animals without MAIP; and a treated group, in which a MAIP protocol was implemented in the donor during the procurement of the left kidney, monitoring the recipient for 24 hours. Results: Urea, creatinine, and lactate dehydrogenase, as well as histopathological analysis (Banff: CT 1,66 ± 0,57 vs. basal 0, and MAIP 1), showed a clear trend in favor of MAIP group. Similar results were observed for tumor necrosis factor-α, interleukin-6 and CXCL10, as well as indicators of oxidative stress, with statistically significant levels for CXCL10 [0,295 ± 0,0074 arbitrary units (AU) CT and 0,0057 ± 0,0065 AU MAIP] and TBARS (2,93 ± 0,08 nmol/μg CT; and 2,49 ± 0,23 nmol/μg MAIP; p 0.05). Conclusion: The findings indicated that the MAIP exerts a protective influence on the transplanted kidneys, functioning as an IRI-protective strategy and enhancing the parameters associated with renal graft functionality.

Background After intestinal or multivisceral transplant, closing the abdominal wall can be challenging, as negative pressure dressing or synthetic meshes pose risks like infections and fistulas. Clinical practice has evolved from vascularized abdominal wall transplants to non-vascularized Abdominal Rectus Fascia (TxARF). Although it was successful, many immunological aspects remain unknown, highlighting the need for further research. Methods The technique was developed by reproducing the technical aspects of the procedure described for humans in rats (Wistar and Sprague Dawley). Twenty-six Isogenic and Allogeneic TxARF procedures were performed and followed until 30 and 120 post-transplant days (PTD). The non-implanted fascias served as a control group. Rats were then re-assessed for engraftment on 7, 11, 30 and 120 PTD. Fascia samples were taken to assess neovascularization by quantifying cell composition and blood vessels using H&E and Orcein staining. Results All animals (N=26) survived at 30 and 120 PTD, with 4 (15.4 %) developed subcutaneous serum collection. Upon reoperation, grafts showed neovascularization. No adhesions were observed between the intestines and the grafts. The principal cell compound of the fascia was represented by Fibroblasts (18.35 cells/field) and Myocytes (6.57 cells/field). A significant increment of the number of blood vessels were observed during the period studied (p=0.046). Conclusions Our report on TxARF in rats, proves the feasibility of this experimental and translational model, showing similar results to those published in the clinical field. Further studies are required to evaluate the immunogenicity as well as the changes in ARF overtime.

Introduction: Small intestinal transplantation has emerged as an essential treatment for intestinal failure, but its relatively high graft rejection rate and mortality rate when compared to those of other transplanted organs has led to difficulties in post-transplantation treatment management. Methods: The recently-developed technique of creating organoids from somatic stem cells has created a challenging opportunity to develop a treatment that involves the creation of a substitute small intestine using autologous cells instead of transplanting another individual’s small intestines. The remaining partial large intestine is then used as the stem cell niche, and autologous small intestinal organoid transplantation is conducted on its epithelium in order to create a pedunculated hybrid graft. Results: This is a new surgical technique for interposing with the original ileocecal region. The hybrid large intestine acquires both the lymphatic vessels that are involved in nutrient absorption and the original peristaltic function of the large intestine. Conclusions: This lecture touches upon the history of the development of organoid medicine, after which an introduction is provided of the revolutionary surgical technique in which a functional small intestine is created by regenerating autologous cells.