Functional and morphometric study of cryopreserved human parathyroid tissue transplanted into nude mice

As part of an ongoing study of the characteristics of transplanted fresh normal and pathologic parathyroid tissues, we transplanted cryopreserved human parathyroid tissue into nude mice. Hyperplastic glands cryopreserved for various lengths of time (<2 weeks and >1 year) were transplanted into the gluteus muscle of nude mice. Specimens grafted were of two sizes: 10 mg and 30 mg. Serum human parathyroid hormone (hPTH) concentration was estimated by a double-antibody immunoradiometric assay prior to transplantation and 2, 4, and 8 weeks after transplantation. A low-calcium diet was given to some mice to evaluate any effects on the grafts of low serum concentrations of calcium. All mice were killed 4 hours after injection of bromodeoxyuridine (Brd U) for assessment of the cell proliferation in grafted parathyroid tissue. Although hPTH secretion of cryopreserved tissue was only half that of fresh tissue, the cryopreserved tissue released hPTH, as did fresh tissue. hPTH secretion was accelerated by stimulation of a low-calcium diet, and PTH secretion was positively correlated with the volume of transplanted tissue. The number of Brd U-immunoreactive cells was correlated with the serum concentration of hPTH (r = 0.95), which indicates that cell proliferation is closely related to PTH secretion under the condition of successful transplantation. The experimental transplantation of cryopreserved tissue into nude mice, coupled with a concise immunohistochemical study of the grafts conducted prior to their transplantation into humans, can contribute to the evaluation of PTH secretion and cell proliferation.