Vascularized whole thymus transplantation in Rowett nude rats: Effect of thymus allograft volume on tolerance induction

Novel Approach to Vascular Thymic Tissue Transplantation in Humans: A Case Report

BACKGROUND

Vascular thymus transplantation has been explored in animal models but remains untested in humans. Current approaches to congenital athymia involve avascular transplantation of allogeneic thymic tissue, which may delay immune recovery. Building on animal studies, we propose revascularization of thymic tissue in a human model. This case report details about the revascularization of neonatal thymic tissue in an elderly woman with terminal cancer, evaluating revascularization efficacy, rejection risks, and procedural safety over a 3-week period.

CASE REPORT

A thymic tissue graft obtained from a neonate during corrective heart surgery was implanted into the left radial forearm of an 85-year-old woman. The graft was evaluated for 3 weeks, with one thymic vein anastomosed to the cephalic vein and one thymic artery to the radial artery. No immunosuppression or HLA matching was employed. Weekly Doppler ultrasound and postexplantation histopathology monitored blood flow and graft status. Hematologic, biochemical, radiological evaluations, and daily clinical follow-up were conducted.

CONCLUSION

This preliminary research demonstrates the feasibility of revascularizing a neonatal thymus in an adult using microsurgical techniques.

Anterior retroperitoneal approach in constructing thymokidney organs in swine for xenotransplantation

Introduction

Thymokidneys (TK) have been constructed to transplant life-supporting kidney grafts containing donor thymic tissue to induce transplant tolerance. Historically, TKs were constructed by inserting pieces of thymus tissue under the kidney capsule using an intra-abdominal or posterior retroperitoneal (lateral/flank) approach. The intra-abdominal approach is technically easier but causes intra-abdominal adhesions and makes kidney procurement more challenging. The posterior retroperitoneal approach causes fewer complications, but thymus tissue implantation is technically demanding due to limited visibility and exposure of the kidney. We herein describe the anterior retroperitoneal approach that overcomes these challenges.

Methods

8-week-old GalTKO-swine (n = 2) were sedated, intubated, and draped. Cervical thymus lobes were isolated and excised. Via a small midline abdominal incision, the peritoneum was dissected bilaterally from the abdominal muscles, identifying both kidneys without entering the peritoneal cavity. Multiple thymus pieces were inserted under the kidney capsule. After 8 weeks, TKs were recovered for flow cytometric and histopathological analysis.

Results

In all kidneys, we successfully constructed TKs with functional thymus tissue under the kidney capsule, verified by histopathology and flow cytometry. No surgical complications were observed, and no adhesions were observed intra-abdominally nor around the kidney, as the peritoneum covered the implanted tissue.

Conclusion

The anterior retroperitoneal approach to constructing thymokidneys is easy to perform, offers excellent kidney exposure, allows a larger volume of thymus tissue to be implanted, and decreases the risk of intra-abdominal adhesions. Such constructed TKs are easy to procure with minimal risk of injury to the vascularized thymus as the prerenal peritoneum covers it.

Recent advances in endocrine organoids for therapeutic application

The endocrine system, consisting of the hypothalamus, pituitary, endocrine glands, and hormones, plays a critical role in hormone metabolic interactions. The complexity of the endocrine system is a significant obstacle to understanding and treating endocrine disorders. Notably, advances in endocrine organoid generation allow a deeper understanding of the endocrine system by providing better comprehension of molecular mechanisms of pathogenesis. Here, we highlight recent advances in endocrine organoids for a wide range of therapeutic applications, from cell transplantation therapy to drug toxicity screening, combined with development in stem cell differentiation and gene editing technologies. In particular, we provide insights into the transplantation of endocrine organoids to reverse endocrine dysfunctions and progress in developing strategies for better engraftments. We also discuss the gap between preclinical and clinical research. Finally, we provide future perspectives for research on endocrine organoids for the development of more effective treatments for endocrine disorders.

The effect of thymus transplantation on donor-specific chimerism in the rat model of composite osseomusculocutaneous sternum, ribs, thymus, pectoralis muscles, and skin allotransplantation

INTRODUCTION

Research on tolerance has proven that development of donor-specific chimerism (DSC) may accompany tolerance induction in vascularized composite allotransplantation (VCA). In this study, we aimed to determine the effect of thymus transplantation on the induction of DSC in rat VCA model of osseomusculocutaneous sternum (OMCS) and osseomusculocutaneous sternum and thymus (OMCST) allotransplantation.

MATERIALS AND METHODS

A total of 20 Lewis-Brown Norway and Lewis rats, 5-6 weeks old, weighting between 120 and 150 g, were used in the study. OMCS (n = 5) and OMCST (n = 5) allografts were harvested from Lewis-Brown Norway donors (RT1^l + n ) based on the common carotid artery and external jugular vein, and a heterotopic transplantation was performed to the inguinal region of the Lewis (RT1^l ) recipients under cyclosporine A monotherapy (16 mg/kg) protocol tapered to 2 mg/kg and maintained for the duration of the study. The peripheral blood chimerism levels (T-cell, B-cell, and monocyte/granulocyte/dendritic cell-MGDC populations) were evaluated at days 7, 14, 35, 63, 100, and 150 posttransplant by flow cytometry. At Day 150, thymus, spleen, and liver samples were assessed by polymerase chain reaction (PCR) in the presence of DSC.

RESULTS

Total chimerism level increased in both OMCST and OMCS groups at all time points. At 150 days posttransplant, chimerism in OMCST group was significantly higher (12.91 ± 0.16%) than that in OMCS group (8.89 ± 0.53%%, p < .01), and PCR confirmed the presence of donor-derived cells in the liver and spleen of all OMCST recipients and in one liver sample and two spleen samples in OMCS recipients without thymus transplant.

CONCLUSIONS

This study confirmed the direct effects of thymus transplantation on the induction and maintenance of DSC in T-cell, B-cell, and MGDC populations. These results confirm correlation between thymus transplantation and DSC induction.

A model of isolated, vascular whole thymus transplantation in nude rats

BACKGROUND

We used a model of vascularized thymus lobes as a whole isolated organ transplantation in rats.

MATERIALS AND METHODS

Male Fisher rats (F344, RT11v1; n = 10) and male homozygous Rowett nude rats (rnu/rnu; n = 10) were used as donors and recipients, respectively. Both vascular lobes of the thymus as a whole isolated organ were heterotopically transplanted to the neck of recipients. The right common carotid artery of the donor thymus was anastomosed end-to-end to the homonymous artery of the recipient. The anterior vena cava and the left brachiocephalic vein of the donor thymus were anastomosed end-to-side to the right and left external jugular veins of the recipient, respectively. Histological examination was used to monitor graft viability; graft function was assessed using flow cytometry (FCM) and immunologic effects by skin grafts in vivo.

RESULTS

All recipients survived. Preparation of the donors and recipients took 35.6 ± 5.5 minutes and 60.3 ± 15.1 minutes, respectively. The blood supply to the thymus graft was patent. Histology of the thymus on postoperative days 14, 56, and 112 revealed viable grafts with preserved microarchitecture. FCM analysis showed 37.18 ± 11.1% CD3+ T cells at day 21 after transplantation. Skin grafts from F344 and Rowett rats survived 8-10 and more than 30 days, respectively, whereas all third-party Sprague Dawley grafts were rejected within 5 days.

CONCLUSION

We developed a novel model of isolated, direct vascularized whole thymus transplantation in nude rats, in which both lobes of the fully vascularized thymus were harvested en bloc for successful transplantation.