Viability and functionality of fresh and cryopreserved human hyperplastic parathyroid tissue tested in vitro

Factors influencing the success of cryopreserved parathyroid autotransplantation: A systematic review

Permanent hypoparathyroidism is a postoperative complication of thyroid and parathyroid surgery and can be cured by cryopreserved parathyroid autotransplantation (CPAT). However, due to the lack of unified and standardized guidelines, the limited ability of the parathyroid tissue itself to withstand cryopreservation, and some yet-to-be-defined processes or technologies, the success rate of cryopreserved parathyroid autotransplantation varies between institutions; it is low for some institutions and high for others. Due to the sparsity of data, views vary on which factors most influence the success rate of cryopreserved parathyroid autotransplantation. In this review, we analyzed the following probable influencing factors: ischemic period before cryopreservation; processes of cryopreservation and thawing, including freezing medium; freezing and thawing methods; duration of cryopreservation; examination of the graft before transplantation; graft site; mass of transplanted tissue fragments; blood calcium level; and the evaluation criteria for cryopreserved parathyroid autotransplantation success. Although the effects of these factors are debatable, we hypothesized that examining them in the above-given order to determine whether they affect the success rate of cryopreserved parathyroid autotransplantation could be beneficial to maximizing the success rate. Our findings led us to conclude that cryopreserved parathyroid autotransplantation operations should be standardized. Standardized guidelines for cryopreserved parathyroid autotransplantation that include such factors as ischemic period time, freezing and thawing methods, and recipient status should be established based on a comprehensive analysis of these factors.

Parathyroid Tissue Cryopreservation: Does the Storage Time Affect Viability and Functionality?

Parathyroidectomy is a standard practice to treat recurrent or persistent hyperparathyroidism. However, this can lead to the onset of hypoparathyroidism, treatable with the autotransplantation of parathyroid tissue (PT). Tissue can be transplanted immediately after parathyroidectomy or cryopreserved and transplanted only in case of necessity. Since 2011, the Cord Blood Bank and Cardiovascular Tissue Bank of Emilia-Romagna has been storing PT for potential autologous transplantation. To date, there are highly variable data about the viability and function of PT after thawing. However, it is not clear if the PT quality is affected by different cryopreservation protocols and/or by the storage time. The aim of this study was to assess the ex vivo function and viability of the PTs of ten patients stored in the Bank. Tissue morphology was evaluated before and after cryopreservation through histological investigations. PT function was analyzed by assessing the ability of cryopreserved PT to synthesize and secrete parathyroid hormone (PTH) in response to different calcium concentrations. Moreover, viability and function were also investigated on tissue-isolated cells in culture. These data show that tested tissues appear to be viable and able to produce PTH even after 5 years of storage, and the histological architecture is well preserved.

Dual-specificity phosphatases are implicated in severe hyperplasia and lack of response to FGF23 of uremic parathyroid glands from rats

Phosphate load accelerates the progression of secondary hyperparathyroidism (sHPT). In advanced stages of sHPT, there is a marked hyperplasia and resistance to classical regulatory endocrine factors such as calcium, calcitriol, or fibroblast growth factor 23 (FGF23), which suppresses PTH secretion by an ERK-dependent mechanism. Nephrectomized rats were fed with a high- or normal-phosphorus diet for different periods of time to induce sHPT. Biochemical parameters, parathyroid gland microarrays, quantitative real-time PCR, and immunohistochemistry (ERK/phospho-ERK) were performed. To test the role of dual-specificity phosphatases (Dusp) on parathyroid gland regulation, normal parathyroid glands were cultured with FGF23 and Dusp. Uremic rats fed with a high-phosphorus diet showed more severe sHPT, higher serum FGF23 levels and mortality, and decreased parathyroid Klotho gene expression. In all stages of sHPT, parathyroid microarrays displayed a widespread gene expression down-regulation; only a few genes were overexpressed, among them, Dusp5 and -6. In very severe sHPT, a significant reduction in phospho-ERK (the target of Dusp) and a significant increase of Dusp5 and -6 gene expression were observed. In ex vivo experiments with parathyroid glands, Dusp partially blocked the effect of FGF23 on PTH secretion, suggesting that Dusp might play a role in parathyroid regulation. The overexpression of Dusp and the inactivation of ERK found in the in vivo studies together with the ex vivo results might be indicative of the defense mechanism triggered to counteract hyperplasia, a mechanism that can also contribute to the resistance to the effect of FGF23 on parathyroid gland observed in advanced forms of chronic kidney disease.