Importance of HLA typing, PRA and DSA tests for successful parathyroid allotransplantation

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.

Is parathyroid allotransplantation a viable option in the treatment of permanent hypoparathyroidism? A review of the literature

BACKGROUND

The standard clinical treatment for hypoparathyroidism, replacement of calcium and vitamin metabolites (calcitriol), has been used for decades; however, evidence points to its inefficiency in acting on the pathophysiology of the disease, which may precipitate or aggravate conditions already related to hypoparathyroidism. Therapies based on recombinant human parathyroid hormone have emerged in recent years but still have low availability due to their high cost. Parathyroid allotransplantation (Pt-a) has been reported as a strategy for treating more severe cases.

METHODS

This narrative review highlights relevant aspects of conventional permanent hypoparathyroidism treatment and provides a comprehensive and critical review of the reports of applications of Pt-a, especially those carried out in recent years. Particular focus is placed on the following key points: parathyroid immunogenicity, immunosuppression regimens (short-term or chronic), techniques to reduce the expression of immunogenic molecules, follow-up time, and reductions in calcium and vitamin D supplementation.

CONCLUSION

Pt-a has been considered a safe and relatively low-cost therapy and is believed to have the potential to cure the disease, in addition to treating symptoms. However, there is considerable heterogeneity in treatment protocols; therefore, more studies are required to improve the standardization of the procedure and thus improve the consistency of outcomes.

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.

HLA-DR, -DP, -DQ expression status of parathyroid tissue as a potential parathyroid donor selection criteria and review of literature

BACKGROUND

Basic and clinical studies about parathyroid allotransplantation have to be utilized with more definitive criteria for longer graft survival. Several reports demonstrated different isolation and cultivation methods for parathyroid cells to minimize their immunogenicity. In this study, we aim to compare and evaluate the clinical characteristics and the status of HLA class II expression changes in parathyroid tissue.

METHODS

A total of 22 parathyroid hyperplasia tissue donors was included in this study. Clinical characteristics were evaluated and compared with the HLA-DR, -DP, -DQ mRNA, and protein expression levels which were determined by qRT-PCR and Western blot.

RESULTS

We have compared the clinical characteristics (age, dialysis duration, frequency, recurrency of hyperparathyroidism and, calcimimetic usage) and HLA class II expression. HLA class II mRNA and protein levels showed varied expression patterns between tissues. Only, the HLA-DP has high mRNA expression levels without affecting the protein level when compared with the ages of the tissue donors. In addition, the HLA-DR, HLA-DP, and HLA-DQα1 protein expression levels showed a permanent and varied expression rate between tissues.

CONCLUSION

Expression of HLA class II molecules in parathyroid cells appears to constitute a decisive factor. Despite the lack of clinical outcomes, present data proposes new insight with a detailed understanding of parathyroid immunogenicity. In the future, randomized controlled clinical trials are needed for the accurate assessment of the effect of the varied HLA class II expression profiles in parathyroid tissue.

Parathyroid allotransplantation for the treatment of permanent hypoparathyroidism: A systematic review

BACKGROUND

Hypoparathyroidism is the most common complication of bilateral operations in the central neck. No formal guidelines exist for the management of permanent hypoparathyroidism. Current treatment involving medical supplementation increases resource utilization and patient morbidity while decreasing quality of life. Parathyroid allotransplant (PA) offers a promising therapy; however, the optimal technique and role of immunosuppression (IS) in PA remain unclear.

METHODS

We performed a systematic search of the Embase, MEDLINE, and Cochrane Library databases to identify studies investigating PA for treatment of hypoparathyroidism.

RESULTS

A total of 24 studies including 186 individual allograft transplants in 146 patients were identified. Pooled graft survival for allotransplants in transplant-naïve vs prior transplant recipients was 29.9% and 80%, respectively.

CONCLUSIONS

PA using normocellular, fresh parathyroid donor tissue that is ABO-compatible, with induction and, at minimum, short-term maintenance IS presents a potentially safe and effective therapeutic option for permanent hypoparathyroidism in patients tolerating IS.

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.

HLA-DQB1 mismatch increase risk of severe bleeding independently in recipients of allogeneic stem cell transplant

Severe bleeding is a major cause of death in acute leukemia (AL) patients with graft-versus-host disease (GVHD) after allogene hematopoietic stem-cell transplantation (allo-HSCT). However, the prognostic value and prediction of HSCT-associated severe bleeding in GVHD patients have not been reported in cohort studies. We did a retrospective analysis of 200 AL patients with GVHD after allo-HSCT from Feb 1, 2014, to Dec 1, 2015. Multivariate analysis showed that the severe bleeding class was associated with the risk of death (HR 2.26, 95% CI 1.31-3.92, p<0.001***). In order to predict severe bleeding and figure out the solution to bleeding events, we established a multiple logistic regression model. HLA-DQB1 unmatching, megakaryocyte reconsititution failure, and III or IV GVHD were the independent risk factors for severe bleeding. Among all the variations above, OR of HLA-DQB1 was the highest (OR: 16.02, 95% CI: 11.54-48.68). Adding HLA-DQB1 to other factors improved the reclassification for predicting severe bleeding (NRI=0.195, z=2.634, p=0.008**; IDI=0.289, z=3.249, p<0.001***). Lasso regression was used to select variants. A nomogram of the logistic model was generated and displayed. Calibration curve demonstrated excellent accuracy in estimating severe bleeding (C index of 0.935). HLA-DQB1 showed excellent efficacy of predicting severe bleeding in HSCT patients.

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.