Takaharu Nagasaka

Histopathology, pathophysiology, and indications for surgical treatment of renal hyperparathyroidism

Morphological changes in the parathyroid glands evidently occur early during renal failure. Histopathological investigations have suggested that parathyroid cells initially increase diffusely with a normal lobular structure (diffuse hyperplasia). The parathyroid glands then become hyperplastic with some nodules (nodular hyperplasia). Cells in nodules grow monoclonally and proliferate aggressively, possibly induced by some kind of genetic abnormality. Pathophysiologically, in cells consisting of hyperplastic nodules, suppression of parathyroid hormone (PTH) secretion under the influence of excess extracellular calcium is more deranged, possibly due to a reduction of calcium-sensing receptors. Vitamin D receptor density decreases more severely in these cells, possibly causing abnormal PTH synthesis, PTH secretion, and even parathyroid cell proliferation. According to histopathological and pathophysiological findings, patients with nodular hyperplasia during renal hyperparathyroidism may be refractory to medical treatments, including calcitriol pulse therapy, and parathyroidectomy will become necessary. There is a relationship between the pattern of parathyroid hyperplasia and glandular weight in which glands weighing more than 500 mg may be pathognomonic of nodular hyperplasia. Glandular volume, estimated by ultrasonography, is one of several important criteria indicating parathyroidectomy. In order to prevent a recurrence of hyperparathyroidism, all nodular hyperplastic tissue should be extirpated.

Clonal analysis of nodular parathyroid hyperplasia in renal hyperparathyroidism

Abstract. Although it is well known that chronic renal failure induces parathyroid hyperplasia, the pathogenesis and development of this parathyroid lesion in this disease are poorly understood. Histopathologically, there is progression from diffuse to nodular hyperplasia, and each nodule consists of a single cell type with aggressive proliferative potential. Pathophysiologic and clinical investigations have suggested that neoplastic tumors may emerge from nodular hyperplasia. In this study the clonality of parathyroid tissue in nodular and diffuse hyperplasia in renal hyperparathyroidism was analyzed by a method based on restriction fragment length polymorphism of the X chromosome-linked phosphoglycerokinase gene and on random inactivation of the gene by methylation. DNA of peripheral lymphocytes was screened in 43 women undergoing parathyroidectomy for advanced renal hyperparathyroidism, and 10 of these patients appeared to be heterozygous. Fourteen specimens from these patients were available for clonal analysis. The analysis showed that all four specimens of diffuse hyperplasia were polyclonal, whereas all seven specimens from nodules in nodular hyperplasia and all three samples representing parathyroid tissue removed from forearm because of graft-dependent recurrence were revealed to be monoclonal. It is likely that the clonal origin of each nodule is independent. These results suggest that in renal hyperparathyroidism parathyroid glands initially grow diffusely and polyclonally, and then the cells in the nodules are later transformed monoclonally and proliferate aggressively. From the present study it can be concluded that nodular hyperplasia represents monoclonal parathyroid neoplasia, which might explain why patients with nodular hyperplasia in renal hyperparathyroidism are refractory to medical treatment, requiring parathyroidectomy. To prevent recurrences, nodular hyperplastic tissue should not be left at surgery.

Are N-glycolylneuraminic acid (Hanganutziu-Deicher) antigens important in pig-to-human xenotransplantation?

Abstract:  Background:  N‐glycolylneuraminic acid (NeuGc) epitopes, so called Hanganutziu–Deicher (HD) antigens, which are widely expressed on endothelial cells of all mammals except humans, are considered to be potential targets for natural and elicited anti‐nonGalα1‐3 Gal (Gal) antibodies in humans. We previously reported that anti‐NeuGc antibodies were not detected in healthy humans by enzyme‐linked immunosorbent assay (ELISA) using NeuGc‐GM3‐coated plates, and no antibody production was observed in patients with a history of exposure to pig cells. However, a recent paper has revealed that (i) anti‐NeuGc antibodies to porcine red blood cells (PRBC) are detectable in most healthy humans, and (ii) the majority of anti‐nonGal antibodies are specific for NeuGc epitopes. The purpose of this study was to reassess whether NeuGc is important as an immunogenic nonGal epitope.

Amlodipine, but not MDR1 polymorphisms, alters the pharmacokinetics of cyclosporine A in Japanese kidney transplant recipients

Background. Cyclosporine A (CsA) is a critical immunosuppressive drug with a narrow therapeutic range and wide interindividual variation in its pharmacokinetics. Many factors, including P-glycoprotein (PGP), influence the oral bioavailability and interpatient variability of CsA. A number of polymorphisms have been identified in the human MDR1 gene, and some of them have been found to be associated with an altered expression of PGP. We have investigated the role of these polymorphisms in CsA absorption from kidney transplant recipients. In addition, we also investigated the effect of amlodipine on CsA absorption. Methods. The area under the time-concentration curve from 0 to 2 hr (AUC0–2) estimated by the trapezoidal rule was used for the evaluation of extent of CsA absorption. The genotypes were identified by a polymerase chain reaction, restriction fragment length polymorphism analysis. Results. No association was found between polymorphisms in the MDR1 and CsA AUC0–2/dose/kg. In contrast, the combination of amlodipine significantly increased CsA AUC0–2/dose/kg (706.2 &mgr;g·hr/L to 819.2 &mgr;g·hr/L, P <0.05). Furthermore, we attempted to compare MDR1 polymorphisms and the absorption of CsA again without patients receiving amlodipine, but there was still no significant difference. Conclusions. There is no relationship between polymorphisms for MDR1 and CsA absorption, suggesting polymorphisms for MDR1 cannot account for the interpatient variability of CsA. Amlodipine, which is the substrate of PGP, significantly increased CsA absorption. These results indicate that PGP plays a significant role in CsA absorption, but its polymorphisms could not influence the CsA absorption.

Potential value of human thrombomodulin and DAF expression for coagulation control in pig‐to‐human xenotransplantation

Miwa Y, Yamamoto K, Onishi A, Iwamoto M, Yazaki S, Haneda M, Iwasaki K, Liu D, Ogawa H, Nagasaka T, Uchida K, Nakao A, Kadomatsu K, Kobayashi T. Potential value of human thrombomodulin and DAF expression for coagulation control in pig‐to‐human xenotransplantation. Xenotransplantation 2010; 17: 26–37.

Comparative study of efficacy of removal of anti‐ABO and anti‐gal antibodies by double filtration plasmapheresis

Abstract: Successful clinical ABO‐incompatible renal transplantation has been achieved by the removal of anti‐A or anti‐B antibodies using double filtration plasmapheresis (DFPP). We have compared changes in the levels of anti‐donor antibodies and the histopathology of the renal grafts following human ABO‐incompatible allotransplantation and pig‐to‐baboon xenotransplantation using pretransplantDFPP.

Production of cloned pigs expressing human thrombomodulin in endothelial cells.

Yazaki S, Iwamoto M, Onishi A, Miwa Y, Hashimoto M, Oishi T, Suzuki S, Fuchimoto D‐I, Sembon S, Furusawa T, Liu DG, Nagasaka T, Kuzuya T, Ogawa H, Yamamoto K, Iwasaki K, Haneda M, Maruyama S, Kobayashi T. Production of cloned pigs expressing human thrombomodulin in endothelial cells. Xenotransplantation 2012; 19: 82–91.

Expression of Parafibromin in Distant Metastatic Parathyroid Tumors in Patients with Advanced Secondary Hyperparathyroidism Due to Chronic Kidney Disease

BackgroundRecently, somatic inactivating mutations in HRPT2 have been reported in the majority of sporadic parathyroid carcinoma in primary hyperparathyroidism (HPT). Parafibromin is a tumor suppressor protein encoded by HRPT2, and loss of nuclear expression of parafibromin was found in approximately 70% of the carcinoma. In secondary HPT due to chronic kidney disease (CKD), parathyroid carcinoma is very rare and whether HRPT2 plays a role in the carcinogenesis in these cases is not clear. We evaluated the expression of parafibromin in hemodialysis patients with distant metastatic parathyroid tumors.MethodsBetween June 1973 and December 2006, 2,142 patients underwent parathyroidectomy (PTx) for secondary HPT in our department. We encountered five (0.23%) patients with distant metastatic parathyroid tumors. We evaluated the immunohistochemistry for parafibromin in eight primary parathyroid glands removed from the neck at the initial operation and/or at reoperation and seven distant metastatic tumors resected at reoperation.ResultsIn only one lung metastatic parathyroid tumor, negative staining for parafibromin was detected. In the other three lung, two regional node, and one chest wall metastatic parathyroid tumor, parafibromin was strongly stained in the nuclei of the parathyroid cells. Among eight primary glands, except for one with weakly positive staining, the expression of parafibromin was detected diffusely and strongly.ConclusionWe conclude that the inactivating mutations and/or allelic loss of the HRPT2 gene may not play a major role in parathyroid carcinogenesis in secondary HPT due to CKD, but in these cases cancer development may be associated with a heterogeneous genetic disorder.

Successful cross‐breeding of cloned pigs expressing endo‐β‐galactosidase C and human decay accelerating factor

Yazaki S, Iwamoto M, Onishi A, Miwa Y, Suzuki S, Fuchimoto D, Sembon S, Furusawa T, Hashimoto M, Oishi T, Liu D, Nagasaka T, Kuzuya T, Maruyama S, Ogawa H, Kadomatsu K, Uchida K, 
Nakao A, Kobayashi T. Successful cross‐breeding of cloned pigs expressing endo‐β‐galactosidase C and human decay accelerating factor. Xenotransplantation 2009; 16: 511–521.

Removal of blood group A/B antigen in organs by ex vivo and in vivo administration of endo-ß-galactosidase (ABase) for ABO-incompatible transplantation

BACKGROUND ABO incompatibility in organ transplantation is still a high risk factor for antibody-mediated rejection, despite the progress in effective treatments. We have explored the possibility of using the enzyme to remove the blood type A/B antigen in organs. METHODS Recombinant endo-beta-galactosidase (ABase), which releases A/B antigen, was produced in E. coli BL-21. Human A/B red blood cells (RBC) were digested with ABase, and subjected to flow cytometric analysis after incubation with human sera. Purified recombinant ABase was intravenously administered to a baboon. Biopsies were taken from kidney and liver before and 1, 4 and 24 h after in vivo administration. Excised baboon kidneys were perfused with cold UW solution+/-purified recombinant ABase and preserved at 4 degrees C. Biopsies were taken before and 1 and 4 h after ex vivo perfusion. The change in A/B antigen expression was analyzed by immunohistochemical study. RESULTS ABase removed 82% of A antigen and 95% of B antigen in human A/B red blood cells, and suppressed anti-A/B antibody binding and complement activation effectively. ABase was also found to remain active at 4 degrees C. In vivo infusion of ABase into a blood type A baboon demonstrated a marked reduction of A antigen expression in the glomeruli of kidney (85% at 1 h, 9% at 4 h and 13% at 24 h) and the sinusoids of liver (47% at 1 h, 1% at 4 h and 3% at 24 h) without serious adverse effects. After ex vivo perfusion and cold storage of excised baboon kidney (blood type B) with ABase, the expression levels of B antigen in glomeruli were reduced to 49% at 1 h and 6% at 4 h. CONCLUSIONS This alternative approach might be useful for minimizing antibody removal and anti-B cell immunosuppression as an adjuvant therapy in ABO-incompatible kidney, liver and possibly heart transplantation.