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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.

Carbohydrate structures on PRBC are different from those on PAEC. Healthy human sera contain anti-nonGal IgG antibodies to NeuGc expressed on PRBC, but not on PAEC. We speculate that anti-nonGal IgG antibodies to PRBC can recognize both NeuGc and protein, and this may be the reason why such antibodies have not been detected by ELISA. A definite conclusion about the immunogenicity of NeuGc has not been obtained. More sera from patients (not from non-human primates) sensitized with porcine cells or organs need to be studied.

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In addition to effective suppression of antibody-induced complement activation, hTM expression in PAEC may be essential for regulating procoagulant activity in xenotransplantation.