An Alternative and Up-To-Date Recommendation for a Proper Site for Parathyroid Transplantation: The Omentum.

OBJECTIVES: Various sites have been used for parathyroid allotransplant, such as injection into the forearm, sternocleidomastoid, or deltoid muscles. However, transplant efficiency in these regions varies according to the results reported in the literature and also obtained from our previous studies. Using the omentum "as a natural incubator" for composite tissue-derived cell transplants to increase transplant success is possible. MATERIALS AND METHODS: To examine the efficiency of transplant sites for parathyroid allotransplant, we compared clinical cases from the literature and our experience with 23 cases. The omental transplant process is performed under general anesthesia by laparoscopic intervention. The abdominal cavity is visualized with an endocamera from a 5-mm trocar. With the help of a flexible catheter from another 5-mm trocar, microencapsulated or naked parathyroid cells are deposited on the omentum in approximately 30 mL of isotonic saline. The trocar sites are then sutured, and the surgery is terminated. Recipients were followed for 6 months with examination of biochemical parameters (parathormone, calcium, and phosphorus levels), medication use, and clinical scoring. RESULTS: In the 23 patients who received parathyroid allotransplants over the omentum, 7 recipients did not exhibit any changes according to the scoring system criteria. However, on average, serum calcium and phosphorus levels remained within the healthy reference range. In addition, use of oral medications among patients decreased, indicating successful transplant survival. These results were consistent with a significant decrease in hypocalcemia symptoms among patients. CONCLUSIONS: In the 23 patients, the success rate was 69.5% for the first 6-month period after transplant. Recent developments and large cohorts are needed to demonstrate the higher efficacy of parathyroid allotransplant over the omentum.

The Challenge of Preoperative Panel Reactive Antibody Positivity in Parathyroid Transplantation.

OBJECTIVES: Identifying suitable recipient criteria and matching recipients with appropriate donors are required to increase survival for parathyroid transplant. This study was undertaken to evaluate transplant survival rates while comparing preoperative panel reactive antibody positivity. MATERIALS AND METHODS: The study included 14 hypoparathyroidism patients who presented to our clinic for parathyroid transplant. Preoperative ABO compatibility and negative cross-match tests were prioritized for recipient-donor matching, and panel reactive antibody screening tests were performed. During the 24-month follow-up, we evaluated medication use and serum calcium, phosphorus, and parathormone levels of patients. RESULTS: Preoperative panel reactive antibody positivity was assessed in 3 groups. The HLA class I-positive group (mean fluorescence intensity range, 179-1770) showed decreased medication use and stability in serum calcium levels. The HLA class IIpositive (mean fluorescence intensity range, 85-3959) showed decreased medication use by 25% to 50% and returned to their former prescription doses after 12 months. An opposite pattern was observed in 2 patients with panel reactive antibody positivity for both HLA classes (mean fluorescence intensity range, 462-2289), with 1 patient requiring medication for continuing symptoms and the other patient occasionally taking additional magnesium supplementation, despite decreased medication doses after 12 months. Serum calcium levels remained normal, and parathormone and phosphorus levels were elevated. CONCLUSIONS: Improving patient symptoms and having no requirement for intravenous calcium replacement are priorities, and monitoring serum levels is the next important step. Varied panel reactive antibody positivities and survival rates indicate a requirement, and each HLA class could require a proper limitation for the mean fluorescence intensity. Preoperative mean fluorescence intensity cut-off value should be <900. Higher mean fluorescence intensity values in panel reactive antibody screenings could increase risk of short-term graft survival after parathyroid transplant. Further studies should include immunological risk assessments by individualizing the outcome with donor-specific antibodies.

Graft survival effect of HLA-A allele matching parathyroid allotransplantation.

Permanent hypoparathyroidism is an endocrine disease that is mostly associated with the disruption of the parathyroid glands during surgery. Allotransplantation is the most promising approach for treatment particularly for its cost-effective and exact curative potential. Herein our aim was to evaluate human leukocyte antigen (HLA)-A allele matching effect on clinical improvement and graft survival after parathyroid transplantation. We performed parathyroid transplantation between ABO/Rh compatible recipient and an unrelated donor who has chronic kidney disease. Preoperative immunological tests include panel reactive antibody, T-flow cytometry crossmatch, B-flow cytometry crossmatch, autoflow cytometry crossmatch, and complement-dependent cytotoxicity crossmatch tests were performed. After histopathological evaluation, half of the resected parathyroid gland cells were isolated and transplanted to the omentum surface by laparoscopy. The transplantation outcome was followed up throughout 382 days. The recipient discharged 2 days after transplantation without any complication. During follow-up, calcium and vitamin D supplementation reduced to a one-third dose; even the intact PTH levels remained low. However, clinical improvement was observed by serum calcium levels. The recipient still continues with low-dose supplementation after 382 days of post-transplantation. Parathyroid cell transplantation to the omental tissue is the most promising option even with only one allele matching for patients with using lifelong high-dose supplementation. Clinical improvements and long-term effect of HLA-A allele matching should be evaluated with more studies and in larger cohorts as well.