Improvement of postoperative hypocalcemia by repeated allotransplantation of parathyroid tissue without anti-rejection therapy

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.

Simultaneous Kidney and Parathyroid Transplantation in the Management of Genetic Hypoparathyroidism in a Child

Background.

Genetically determined hypoparathyroidism can lead to life-threatening episodes of hypocalcemia and, more rarely, to end-stage kidney disease at a young age. Parathyroid allotransplantation is the only curative treatment, and in patients already receiving immunosuppression for kidney transplantation, there may be little additional risk involved. We report the first such case in a child.

Methods.

An 11-y-old girl, known to have hypoparathyroidism secondary to an activating pathogenic variant in the calcium-sensing receptor, developed end-stage kidney disease and was started on intermittent hemodialysis. Since the age of 2.5 y, she had been receiving treatment with exogenous synthetic parathyroid hormone (PTH). In June 2019, at the age of 11.8 y, she received a living-donor kidney and simultaneous parathyroid gland transplant from her father. The kidney was implanted into the right iliac fossa, followed by implantation of the parathyroid gland into the exposed rectus muscle.

Results.

The kidney graft showed immediate function while the intrinsic serum PTH level remained low at 3 ng/L. Exogenous PTH infusion was reduced on day 6 posttransplantation to stimulate PTH production by the new gland, which resulted in improving intrinsic PTH concentrations of 28 ng/L by day 9. Twelve months after transplantation, PTH levels remain in normal range and the kidney graft function is stable with a serum creatinine of 110 μmol/L.

Conclusions.

Simultaneous living donation and transplantation of a kidney and a parathyroid gland into a child is safe and feasible and has the potential to cure primary hypoparathyroidism as well as kidney failure.

Parathyroid Allotransplantation: A Systematic Review

Background: To date, there is no satisfactory treatment for patients with calcium and vitamin D supplementation refractive hypoparathyroidism. Parathyroid allotransplantation by design is a one-time cure through its restoration of the parathyroid function and, therefore, could be the solution. A systematic literature review is conducted in the present paper, with the aim of outlining the possibilities of parathyroid allotransplantation and to calculate its efficacy. Additionally, various transplantation characteristics are linked to success. Methods: This review is carried out according to the PRISMA statement and checklist. Relevant articles were searched for in medical databases with the most recent literature search performed on 9 December 2021. Results: In total, 24 articles involving 22 unique patient cohorts were identified with 203 transplantations performed on 148 patients. Numerous types of (exploratory) interventions were carried out with virtually no protocols that were alike: there was the use of (non-) cryopreserved parathyroid tissue combined with direct transplantation or pretreatment using in vitro techniques, such as culturing cells and macro-/microencapsulation. The variability increased further when considering immunosuppression, graft histology, and donor–recipient compatibility, but this was found to be reported in its entirety by exception. As a result of the large heterogeneity among studies, we constructed our own criterium for transplantation success. With only the studies eligible for our assessment, the pooled success rate for parathyroid allotransplantation emerged to be 46% (13/28 transplantations) with a median follow-up duration of 12 months (Q1–Q3: 8–24 months). Conclusions: Manifold possibilities have been explored around parathyroid allotransplantation but are presented as a double-edged sword due to high clinical diverseness, low expertise in carrying out the procedure, and unsatisfactory study quality. Transplantations carried out with permanent immunosuppression seem to be the most promising, but, in its current state, little could be said about the treatment efficacy with a high quality of evidence. Of foremost importance in pursuing the answer whether parathyroid allotransplantation is a suitable treatment for hypoparathyroidism, a standardized definition of transplantation success must be established with a high-quality trial.

MANAGEMENT OF ENDOCRINE DISEASE: Postsurgical hypoparathyroidism: current treatments and future prospects for parathyroid allotransplantation

BACKGROUND

Permanent postsurgical hypoparathyroidism (POSH) is a major complication of anterior neck surgery in general and of thyroid surgery in particular. Depending on diagnostic criteria, up to 10% of patients undergoing bilateral thyroid surgery develop POSH. This leads to a multitude of symptoms that decrease the quality of life and burden the healthcare provision through complex needs for medication and treatment of specific complications, such as seizures and laryngospasm.

METHODS

Narrative review of current medical treatments for POSH and of the experience accumulated with parathyroid allotransplantation.

RESULTS

In most patients, POSH is controlled with regular use of calcium supplements and active vitamin D analogues but a significant proportion of patients continue to experience severe symptoms requiring repeated emergency admissions. Replacement therapy with synthetic PTH compounds (PTH1-34, Natpara® and PTH1-84, teriparatide, Forsteo®) has been assessed in multicentre trials, but the use of this medication is restricted by costs and concerns related to the risk of development of osteosarcoma. Based on recent case reports of successful allotransplantation of parathyroid tissue between siblings, there is renewed interest in this technique. Data on selection of donors, parathyroid cell preparation before allotransplantation, site and timing of transplantation, need for immunosuppression and long-term outcomes are reviewed.

CONCLUSION

A prospective trial to assess the efficacy of parathyroid allotransplantation in patients with severely symptomatic protracted post-surgical hypoparathyroidism is warranted.

Fresh tissue parathyroid allotransplantation with short-term immunosuppression: 1-year follow-up

BACKGROUND

Permanent hypoparathyroidism is a serious problem and requires medications indefinitely. Parathyroid allotransplantation (PA) with short-term immunosuppression is definitive choice but long-term results are not clear.

METHOD

We performed PA from two donors to two recipients. Both recipients were 39-year-old females. Donors were a 32-year-old female and a 36-year-old male, who both have chronic kidney disease. Routine tests, viral markers, and cross-matches were analyzed individually. The parathyroid glands were resected from the living donors, fragmented quickly in the operation room and injected into the left deltoid muscles of the two recipients.

RESULTS

Methylprednisolone was administered on post-PA day one and two. Recipients were discharged from the hospital without complications. Calcium and PTH levels were observed throughout 1 year. We did not observe any complications during the follow-up period. Medications ceased in post-transplantation week 1 for Case 1 and after 1 month for Case 2.

CONCLUSION

Fresh tissue PA with short-term immunosuppression appears to be a promising technique that is easy to perform, is cost-effective, has low risk of side effects and minimal complications with compatibility for HLA conditions. A longer follow-up period and more case studies are needed to determine the risks and benefits of this procedure for future cases.

Mechanisms of tolerance to parental parathyroid tissue when combined with human allogeneic thymus transplantation

BACKGROUND

The induction of tolerance toward third-party solid organ grafts with allogeneic thymus tissue transplantation has not been previously demonstrated in human subjects.

OBJECTIVE

Infants with complete DiGeorge anomaly (having neither thymus nor parathyroid function) were studied for conditions and mechanisms required for the development of tolerance to third-party solid organ tissues.

METHODS

Four infants who met the criteria received parental parathyroid with allogeneic thymus transplantation and were studied.

RESULTS

Two of 3 survivors showed function of both grafts but subsequently lost parathyroid function. They demonstrated alloreactivity against the parathyroid donor in mixed lymphocyte cultures. For these 2 recipients, parathyroid donor HLA class II alleles were mismatched with the recipient and thymus. MHC class II tetramers confirmed the presence of recipient CD4(+) T cells with specificity toward a mismatched parathyroid donor class II allele. The third survivor has persistent graft function and lacks alloreactivity toward the parathyroid donor. All parathyroid donor class II alleles were shared with either the recipient or the thymus graft, with minor differences between the parathyroid (HLA-DRB1∗1104) and thymus (HLA-DRB1∗1101). Tetramer analyses detected recipient T cells specific for the parathyroid HLA-DRB1∗1104 allele. Alloreactivity toward the parathyroid donor was restored with low doses of IL-2.

CONCLUSION

Tolerance toward parathyroid grafts in combined parental parathyroid and allogeneic thymus transplantation requires matching of thymus tissue to parathyroid HLA class II alleles to promote negative selection and suppression of recipient T cells that have alloreactivity toward the parathyroid grafts. This matching strategy may be applied toward tolerance induction in future combined thymus and solid organ transplantation efforts.