Laryngeal Transplantation in the Setting of Cancer: A Rat Model:

Total laryngeal transplant explanted: 14 years of lessons learned

In 1998, the first successful total laryngeal transplant was performed. Outstanding voice quality and swallowing function were achieved, and over the subsequent 14 years, much was learned about tolerance of a transplanted larynx. After approximately a decade, a slowly progressive, chronic rejection process gradually rendered the organ nonfunctional, and the patient and his providers deemed him appropriate for explantation. This is a report of the clinical indications and outcome surrounding the explantation of the first successful total laryngeal transplant.

Ten-Month Laryngeal Allograft Survival with Use of Pulsed Everolimus and Anti—αβ T-Cell Receptor Antibody Immunosuppression

Objectives:

The risks of daily immunosuppression limit the use of laryngeal transplantation as a reconstructive option. Pulsed immunosuppressive dosing can lessen these risks. The study objective was to develop a long-term pulsing regimen that minimizes exposure to immunosuppressive agents.

Methods:

Rat laryngeal transplantation was performed. Everolimus (1 mg/kg per day) and anti–αβ T-cell receptor (TCR) antibodies (250 μg) were given for 7 days beginning 1 day before transplantation and for 5 days beginning on day 90 after transplantation. On day 180, group 1 (n = 5) received the initial regimen for 3 days, and group 2 (n = 5) received everolimus (1 mg/kg per day) until euthanization, which occurred when parathyroid hormone (PTH) levels dropped to less than 11 pg/mL or at 300 days.

Results:

Four of the 5 rats in group 1 had normal PTH levels at 300 days. The PTH level for 1 rat was less than 11 pg/mL at 270 days. In group 2, none of the 5 rats had normal PTH levels at 300 days. Two had PTH levels below 11 pg/mL at 270 days, and 3 had PTH levels below 11 pg/mL at 300 days. The allografts that survived beyond 300 days had an essentially normal histologic appearance.

Conclusions:

Pulsed immunosuppression prevented allograft rejection for 10 months and was more effective than daily everolimus. Short-term perioperative therapy followed by pulsed, tapered dosing is a viable alternative to traditional regimens and may decrease associated risks.

Long-Term Laryngeal Allograft Survival Using Low-Dose Everolimus

OBJECTIVE: The purpose of this study was to explore the mechanism and utility of everolimus as a single-agent therapy in preventing mouse laryngeal allograft rejection.

STUDY DESIGN: Prospective animal study.

SETTING: Academic research at a tertiary medical center.

SUBJECTS AND METHODS: Fifteen recipient mice (five per group) were injected with everolimus (1 mg/kg/d) until euthanized at 15, 30, and 60 days posttransplantation. Five mice received transplants without immunosuppression and were euthanized at day 15. Larynges were graded for rejection severity. Draining lymph nodes and spleens were evaluated by flow cytometry to assess the systemic immunological environment.

RESULTS: Each time group demonstrated minor allograft rejection (rejection severity scores: 2.51, 2.46, 2.78; no rejection, 1; severe, 6). This was not significantly different between groups. Everolimus-treated mice had significantly less rejection at all time points compared with non-immunosuppressed mice. Flow cytometry showed a blunted cytotoxic T-cell response, differentiation favoring regulatory T-cells, and decreased number and function of dendritic cells.

CONCLUSIONS: Everolimus successfully prevents laryngeal allograft rejection up to 60 days posttransplantation. It appears to increase the production of regulatory T-cells while decreasing cytotoxic T-cell and dendritic cell response. Everolimus alone or in combination with other immunosuppressants may enable laryngeal transplantation to become a viable reconstructive option following laryngectomy for malignancy.