Revascularisation of human parathyroid tissue transplanted to athymic mice

The revascularisation process of transplanted human normal, hyperplastic and adenomatous parathyroid tissue was analysed at 2 and 4 days and 1, 2, 4, 7 and 12 weeks after transplantation to athymic mice. The transplants were examined by light and electron microscopy, immunohistochemistry and autoradiography. Vessels were detected by monoclonal antibodies specific for mouse and human endothelial cells. Immunohistochemistry demonstrated ingrowth of vessels from the host into the transplant and at one week numerous capillary sprouts were observed in the peripheral parts of the transplants. During the first week, peak levels of proliferation (labelling index) were observed in endothelial cells and capsular fibroblasts, and the proliferative capacity of endothelial cells was most pronounced in adenoma transplants. Fenestrated capillaries were observed in hyperplastic and adenomatous transplants, but not in transplants of normal tissue. In conclusion, revascularisation of transplanted human parathyroid tissue is enabled by ingrowth of vessels from the host into the transplant. The proliferative capacity of endothelial cells is higher and the process of maturation is faster in hyperplastic and adenomatous tissue compared to normal tissue.     

Recurrent hyperparathyroidism due to parathyroid autografts: incidence, presentation, and management

Recurrent hyperparathyroidism (HPT) occurs in a small percentage of patients undergoing parathyroidectomy for primary HPT and is usually due to inadequate excision of hyperfunctioning parathyroid tissue in the neck, a missed ectopic and hyperplastic parathyroid, or, less commonly, parathyroid carcinoma and parathyroid autografts. In order to determine the incidence, clinical characteristics, and outcome of patients with recurrent HPT due to parathyroid autografts, we reviewed our experience with 604 consecutive patients operated on for primary HPT between 1965 and 1989. One hundred of these patients received parathyroid autografts consisting of portions of one or more parathyroid glands. Three patients with autografts, placed in the sternocleidomastoid muscle, developed recurrent HPT due to their autografts for an incidence of 3 per cent. Recurrent disease was diagnosed between 62 and 113 months with an average of 89 months. The autotransplants in all three of these patients were from hyperplastic or adenomatous parathyroid tissue. Two patients had a history of neck irradiation. Preoperative thallium scans accurately localized the hyperfunctioning parathyroid tissue in all three patients. At operation, the hyperfunctioning autografts had grown into a discrete mass with a single vascular pedicle and were resected. Histologic examination disclosed either hyperplastic or adenomatous tissue, and corresponded to the histology and location of the original tissue transplanted in each case. Follow-up ranges from 12 to 67 months, with an average of 48 months. All patients remain cured and none require oral calcium supplementation. We conclude that graft-dependent recurrent HPT is due to the autotransplantation of hyperplastic or adenomatous parathyroid tissue and that thallium scanning is instrumental for diagnosis and localization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Depressed expression of calcium receptor in parathyroid gland tissue of patients with hyperparathyroidism

The factors involved in abnormal parathyroid cell secretory function and growth in patients with primary (I degree) and secondary (II degree) hyperparathyroidism are still incompletely understood. We compared the expression of the calcium-sensing receptor (CaR) at the gene message and the protein level in parathyroid tissue obtained from patients with I degree non-uremic or II degree uremic hyperparathyroidism with that in normal parathyroid tissue, using in situ hybridization and immunohistochemistry techniques. The expression of the CaR mRNA and protein was reduced in most cases of I degree adenoma and II degree hyperplasia, compared with strong expression normal parathyroid tissue. In II degree hyperparathyroidism, expression of both receptor mRNA message and protein was often particularly depressed in nodular areas, compared with adjacent non-nodular hyperplasia. Decreased Ca-R expression in adenomatous and hyperplastic parathyroid glands would be compatible with a less efficient control of PTH synthesis and secretion by plasma calcium than in normal parathyroid tissue.     

Altered adenylate cyclase kinetics in hyperfunctioning human parathyroid glands

Current evidence suggests that parathyroid gland adenylate cyclase is involved in the control of parathyroid hormone (PTH) secretion. Thus, the altered control of PTH release in hyperparathyroidism may relate to altered adenylate cyclase activation. Therefore, we examined adenylate cyclase kinetics in membrane preparations from hyperfunctioning human parathyroid glands and normal human and bovine parathyroid tissues. There were no differences in the affinity for ATP between enzymes of normal and pathological tissue. However, the enzyme in 10 hyperfunctioning glands showed increased affinity for Mg++. The activation constant for Mg++ (KaMg) of adenylate cyclase in normal human glands was 10.6 +/- 2 mM, a value not different from that of normal bovine parathyroid tissue (9.5 +/- 1 mM). In contrast, the adenylate cyclase in membrane preparations from three of four hyperplastic and six of seven adenomatous human glands showed a markedly reduced KaMg, ranging from 0.85-1.64 mM and from 1.58-6.46 mM, respectively. In one adenoma and one hyperplastic gland, the Ka of the enzyme for Mg++ was close to normal. The addition of guanylylimidodiphosphate or GTP to the incubation mixture increased, in a dose-dependent manner, the apparent KaMg of the enzyme in the abnormal tissue toward normal, suggesting a defective nucleotide regulatory site in the adenylate cyclase of hyperparathyroid glands. In addition, the hyperparathyroid gland enzyme was less susceptible to inhibition by calcium, requiring 0.7-1 mM Ca++ for 50% inhibition, whereas comparable inhibition of the normal adenylate cyclase was seen at 0.22-0.28 mM Ca++. We conclude that the abnormal control of PTH secretion in hyperparathyroidism may be related, at least in part, to alterations in the characteristics of parathyroid gland adenylate cyclase.     

The lack of interaction between transplanted human fetal pancreas and liver

Trophism between transplanted hepatocytes and pancreatic endocrine tissue has been demonstrated with both adult and late gestational fetal tissue. Since this effect has not been looked for with fetal tissue obtained early in pregnancy, we conducted a series of experiments transplanting human liver and pancreas, which was obtained early in the second trimester (15-20 weeks gestation), beneath the renal capsule of athymic mice. Fetal pancreatic explants increased in size after transplantation into nondiabetic mice, but their insulin content 11 weeks later was not different from that of grafts that included liver explants. Reversal of diabetes was achieved in 2 of 5 diabetic mice transplanted with pancreas alone, but none of the mice that received pancreas and liver became normoglycemic. Histological examination of grafted liver explants, which consist of hepatocytes and hematopoietic cells, showed that hepatocytes survived for only two weeks regardless of the presence of pancreatic explants. Bile ducts differentiated by this time in both groups and were still present at 7 weeks. In conclusion, there was no trophic effect observed between transplanted fetal human liver and pancreatic endocrine tissue obtained early in pregnancy; bile duct differentiation is a feature of fetal human liver xenografted into the athymic mouse.     

Ultrastructural localization of GLUT 1 and GLUT 3 glucose transporters in rat brain

Owing to the complexity of the parathyroid hormone's metabolic interactions, clinical hypoparathyroidism is one of the most difficult of all endocrine disorders to treat. Therefore, causative treatment of this disorder by transplantation of parathyroid glands is highly desirable. We have recently documented the long-term in vivo function of iso- and allotransplanted rat parathyroid tissue without systemic immunosuppression in an animal model. In view of the potential clinical use of this method, human parathyroid tissue has been microencapsulated and transplanted over the highest immunological barrier. In a controlled, long-term animal study in the parathyroidectomized rat, the effect of microencapsulation on xenotransplanted human parathyroid tissue was evaluated over 30 weeks (native and microencapsulated parathyroid tissue = 40 rats respectively). Functionally, human parathyroid tissue was able to replace that of the rat. All animals that had received microencapsulated parathyroid tissue were normocalcemic for 16 weeks; 27/40 at the end of the study. In contrast, serum calcium concentrations dropped to post-parathyroidectomy levels within 4 weeks in those animals that had received native tissue only. Histologic evaluation of the explanted, functionally successful xenografts showed vital parathyroid tissue inside intact microcapsules surrounded by a small rim of fibroblasts. Avital fibrotic remnants were demonstrated in animals with non-encapsulated parathyroid tissue. Thus, we have established the feasibility of microencapsulation of human parathyroid tissue, preserving its viability over long periods in vivo even if xenotransplanted. In combination with an improved tissue culture method, transplantation of human parathyroid tissue and maintenance of its physiological function is reproducibly achieved without postoperative systemic immunosuppression over the highest transplantation barrier. This may be a crucial step towards the first clinical application of this method.     

Optimal effectiveness of BDNF for fetal nigral transplants coincides with the ontogenic appearance of BDNF in the striatum

Transplantation of fetal nigral dopamine neurons into the caudate and putamen of Parkinson's disease patients produces limited symptomatic relief. One approach to augment the outgrowth and function of nigral grafts includes exposure of the graphs to neurotrophic factors; however, the temporal requirements for optimizing these actions are unknown. The present study characterized the ontogeny of brain-derived neurotrophic factor (BDNF) in the rat striatum and used this information to define and evaluate three distinct periods of BDNF infusion into fetal nigral grafts transplanted into the striatum of rats with experimental Parkinson's disease. At postnatal day 1 (P1), BDNF and dopamine were measured at 17 and 27% of peak levels, respectively, that occurred at P27 for both. Both compounds showed their greatest surge between P7 and P20, increasing from 40% to approximately 95% of peak levels. Exogenous BDNF infused into transplants during weeks 1 and 2 after the transplantation, which coincide with the developmental period embryonic day 14 (E14)-P7 for transplanted tissue, did not improve rotational behavior or enhance fiber outgrowth of transplanted dopamine neurons. Delaying the BDNF infusion until transplanted tissue was approximately P8-P21 greatly enhanced the effect on rotational behavior and doubled the area of dopamine fiber outgrowth from the transplants. Delaying the infusion until transplanted tissue was approximately P36-P49 failed to augment fiber outgrowth and decreased the behavioral function of transplants. Thus, the optimal effect of exogenous BDNF on the development of dopamine neurons in fetal nigral transplants occurs at a postnatal age when endogenous dopamine and BDNF show the greatest increases during the normal development of the striatum.     

Thymoma-associated myasthenia gravis. Transplantation of thymoma and extrathymomal thymic tissue into SCID mice

To study the possible role of thymomas and of extrathymomal thymic tissue in the development and maintenance of myasthenia gravis, we transplanted fragments of either tissue into SCID mice and monitored the production of anti-acetylcholine receptor antibodies in the recipients. Furthermore, the transplants were characterized by immunohistochemistry. Unlike after transplantation of thymus with lymphofollicular hyperplasia that induced high titers of anti-acetylcholine receptor antibodies, thymoma transplants never produced autoantibodies. Mice transplanted with extrathymomal thymic tissue also failed to produce anti-acetylcholine receptor antibodies except one group that received transplants containing hyperplastic extrathymomal tissue. These findings may explain the refractoriness of thymomatous myasthenia to thymectomy.     

Direct cloning of human parathyroid hyperplasia cells in soft-agar culture

Parathyroid specimens removed from patients with clinical hyperparathyroidism were cultured in a two-layer soft-agar system. Four patients had parathyroid hyperplasia and one had a parathyroid adenoma. Colonies grew from single-cell suspensions of each specimen. Plating efficiency ranged from 0.001 to 0.05%. No colonies grew from normal bovine parathyroid specimens. Parathormone was detected in 0.9% NaCl solution incubated with the culture plates of three of the four human specimens tested. Parathormone levels determined by radioimmunoassay ranged from 10.4 < 100 ng/ml. Plates tested serially showed a progressive rise in parathormone levels with time and an increase in colony size and number. Microscopic evaluation of the cellular layer showed clusters of cells morphologically consistent with parathyroid origin. Colonies remained viable for approximately 3 weeks. These data confirm that malignancy of tissue in vivo is not necessary for colony formation in agar and that human parathyroid hyperplasia or adenoma cells produce and secrete parathormone in this system.     

Fluorescein as a marker for subretinal transplantation of human fetal neural retina

PURPOSE: To investigate the effect of fluorescein on human fetal neural retina and adult rat retina; and to use fluorescein to map the area of subretinal transplantation. METHODS: In vitro: Human fetal neural retina (8 to 14 weeks gestational age) was incubated in 0.03% fluorescein in Dulbecco's Modified Eagles Medium (DMEM) or DMEM alone for 30 min. Viability was determined using the trypan blue exclusion test, and results were compared. Effects of the fluorescein on cell morphology were assessed by observation of primary cultures for 1 week. In vivo: Human fetal neural retina was mechanically dissociated in 0.03% fluorescein in DMEM and transplanted to the subretinal space of immunosuppressed rats. To control for the effect of fluorescein on the grafted tissue, transplants were also performed in DMEM only. After transplantation, indirect ophthalmoscopy and true color fundus photography were performed to document the area covered by the transplant. One month after transplantation, the appearance of grafts exposed to fluorescein was compared to those that were not, at the light microscopic level. RESULTS: In vitro: Exposure of human fetal neural retina to fluorescein had no effect on viability. Similarly, in tissue culture, the fluorescein-exposed cells exhibited the same phenotype as the controls. In vivo: Immediately after transplantation the graft site was clearly outlined within the subretinal area and fluoresced intensely. There were no traces of the dye 2 h after transplantation. Cells that were transplanted with fluorescein survived transplantation, and one month after transplantation could be seen forming subretinal grafts. No differences were noted between these and control grafts. CONCLUSIONS: Fluorescein is an effective dye for immediate and transient localization of trans-scleral transplants to the subretinal space. It allows mapping of the area covered by the injection without interfering with the viability and differentiation of the transplanted cells. It allows unequivocal photo- and video-documentation in both the albino and pigmented fundi. It is already FDA approved for many other extra- and intraocular studies and now has directly been shown to be non-toxic to both human fetal neural retina and adult rodent retina.     

Functioning oxyphil adenoma of parathyroid gland. An ultrastructural and biochemical study

Oxyphil cells and oxyphil cell adenomas of parathyroid glands are, in most instances, regarded to be nonfunctioning. Although 21 cases of hyperparathyroidism associated with parathyroid oxyphil cell adenoma have been reported, secretion of hormone by these tumors has not been conclusively demonstrated. A parathyroid adenoma, diagnosed by light microscopy as oxyphil type, together with the results from ultrastructural and biochemical studies of the patient's adenomatous tissue, are reported here. The patient, a 64-year-old male, was found to have elevated serum calcium, low serum phosphorus, and elevated serum immunoreactive parathormone: findings consistent with hyperparathyroidism. After excision of two small normal-appearing glands and one greatly enlarged (1.9 g) parathyroid gland, those laboratory values returned to normal. Light microscopy of the enlarged parathyroid indicated that it consisted almost entirely of an oxyphil adenoma. Electron microscopy revealed that the adenoma was composed mainly of mitochondria-rich oxyphil cells but also of interspersed transitional oxyphil cells and rare scattered chief cells. Golgi zones, rough endoplasmic reticulum, and prosecretory and secretory-like granules were observed in some oxyphil cells, in most transitional oxyphil cells, and in the infrequent chief cells. Thus, many of these cells appear to contribute to the production and secretion of parathormone. Biochemical studies performed directly on the adenomatous tissue demonstrated that it was able to synthesize proparathormone and parathormone, although the proportion of hormonal peptide synthesis relative to that of the total protein synthesis in this tissue was much smaller (0.9%) than that found in normal parathyroid tissue (5.7%). There was a small increase in immunoreactive parathormone when the adenoma tissue was incubated in a low-calcium medium. These findings indicate that this oxyphil adenoma of the parathyroid gland synthesized and secreted parathormone, apparently to some extent autonomously, but suggest that its capacity to do so was largely dependent on its component of cells other than fully developed oxyphil cells, such as transitional oxyphil cells.     

Nonadenomatous thymic unencapsulated parathyroid tissue as a cause of persistent primary hyperparathyroidism

Primary hyperparathyroidism may be caused by ectopic intrathymic parathyroid adenomas or hyperplastic parathyroid glands. The association of the ectopic inferior parathyroid glands and the thymus is due to their common embryologic origin from the third pharyngeal pouch. We report a case of primary hyperparathyroidism due to an unusual pathologic parathyroid gland formation: nonadenomatous thymic unencapsulated parathyroid tissue. Two unsuccessful neck exploration revealed only two normal parathyroid glands within the cervical area. Radiologic imaging studies failed to localize an ectopic parathyroid adenoma. Mediastinal exploration and thymectomy showed one small focus of unencapsulated hypercellular parathyroid tissue expanding peripherally along the septa of thymic adipose tissue. The hyperparathyroidism resolved with the surgical procedure.     

Host-graft circulation and vascular morphology in pancreatic tissue transplants in rats

One of the most determining factors for the survival of tissue grafts is an intact vasculature. This vasculature must, however, be linked to the circulation of the host animals for survival and growth to occur. The mechanism(s) of revascularization of pancreatic tissue grafts is still unclear and more so the process by which the host blood vessels anastomose with those of the graft. The microvasculature and revascularization of neonatal pancreatic tissue fragments transplanted into the anterior eye chamber of rats were investigated using conventional light and electron microscopy as well as the india ink perfusion method. Light microscopy demonstrated that the blood vessels of the host iris revascularized the transplants within 24 h of transplantation. Sinusoidal blood capillaries were observed to invade the peripheral parts of the grafts. The capillary encroachment from the iris into the graft continued through the second day of transplantation. The host-graft anastomosis developed completely and became prominent and conspicuous after the third day of transplantation. Many capillaries were observed to encroach into the graft from the iris. The vasculature of the graft was increased in comparison with that of normal pancreatic tissue. This increase was prominent especially around pancreatic islet and ductal cells which survived after transplantation. Blood cells observed in these vessels of the graft indicated a functional state. The ultrastructure of the intrinsic blood vessels of the graft was intact and showed the peculiar fenestrations normally seen in the blood vessels of endocrine tissues. These observations indicated that pancreatic tissue fragments transplanted into the anterior eye chamber of rats were revascularized within 24 h. The revascularization was completed at the end of the third day of transplantation when definitive blood vessels linked the circulation of the graft with that of the iris.     

Effect of dose size on the pharmacokinetics of orally administered quinine

Parathyroid scintigraphy is useful in detecting residual hyperplastic parathyroid tissue in patients who continue to have hyperthyroidism after "total parathyroidectomy." Typically, only the neck and mediastinum are imaged. The authors report a case in which images of the forearm were helpful in detecting hyperplastic autologous transplanted parathyroid tissue.     

Normal human cementum-derived cells: isolation, clonal expansion, and in vitro and in vivo characterization

Cultures of primary human cementum-derived cells (HCDCs) were established from healthy premolar teeth extracted for orthodontic reasons. Cementum was manually dissected, fragmented, and digested twice with collagenase. Following a thorough wash to remove liberated cells, the remaining cementum fragments were plated in Dulbecco's modified Eagle's medium/F12 medium containing 10% fetal bovine serum. Discrete colonies that contained cells exhibiting fibroblast-like morphology were visible after 14-21 days of culture. When the colonies became sufficiently large, cells from individual colonies were isolated and subcultured. Cementum-derived cells exhibited low levels or no alkaline phosphatase activity and mineralized in vitro to a lesser degree than human periodontal ligament (PDL) cells and human bone marrow stromal cell (BMSC) cultures. To study differentiation capacities of HCDCs, cells were attached to hydroxyapatite/tricalcium phosphate ceramic and transplanted subcutaneously into immunodeficient mice. The transplants were harvested 3, 6, and 8 weeks after transplantation and evaluated histologically. In human BMSC transplants, new bone tissue was formed with a prominent osteoblastic layer and osteocytes embedded in mineralized bone matrix. No osseous tissue was formed by PDL cells. Of six single colony-derived strains of HCDCs tested, three formed a bone-like tissue that featured osteocyte/cementocyte-like cells embedded within a mineralized matrix and which was lined with a layer of cells, although they were somewhat more elongated than osteoblasts. These results show that cells from normal human cementum can be isolated and expanded in vitro. Furthermore, these cells are capable of differentiating and forming mineralized tissue when transplanted into immunodeficient mice.     

Organization and histochemical phenotype of human fetal cerebellar cells following transplantation into the cerebellum of nude mice

Previous rodent studies have demonstrated the capacity of cerebellar transplants to organize into trilaminar cell layers typically observed in the normal cerebellum. In Purkinje Cell (PC)-deficient animals, PCs will migrate into the host and form synaptic connections. Recently, fetal cerebellar grafts transplanted into the Purkinje cell degeneration (pcd) mutant mouse were shown to result in an improvement of motor behaviors. These studies indicate the potential therapeutic use of neural transplantation in patients with cerebellar degeneration. In the present study, human fetal cerebellar tissue (8.5 wk postconception) was dissociated and transplanted into the normal cerebellum of nude mice. Six months following transplantation, histological analysis revealed donor cells in recipient mice. Immunostaining for the 28 kDa calcium-binding protein (calbindin) revealed the presence of donor PCs that were organized in discrete cellular layers within the transplant neuropil. In most cases the dendritic processes were oriented in a planar fashion perpendicular to the transplant cell layer. Human neurofilament immunostaining revealed bundles of donor fibers within the core of the transplant and/or at the periphery. These bundles were found to be calbindin positive (PC fibers). Three animals provided evidence of donor PC axon growth ventrally into host white matter, and in one case, this ventral migration reached the deep cerebellar nuclei. Most notable was the development of a pronounced folia-like organization by the implanted cell suspensions. Glial processes within the grafts were aligned perpendicular to the long axis of the transplant folia. These results demonstrate the capacity of human fetal cerebellar cell suspension to reorganize into cell layers typical of the normal cerebellum following transplantation into the rodent cerebellum, and develop an organotypic folia-like organization.     

Human embryonic spinal cord grafts in adult rat spinal cord cavities: survival, growth, and interactions with the host

The ability of solid pieces of transplanted human embryonic spinal cord to survive, grow, and integrate with adult rat host spinal cord tissue was investigated. Unilateral cavities were surgically created at vertebral level T12-T13 in 10 athymic nude rats and 5 regular Sprague-Dawley rats. Seven of the athymic rats acutely received a human spinal cord graft, while the remaining 8 rats served as controls, with cavities alone. After 6 months the morphological outcome was evaluated with cresyl violet and with immunohistochemistry using antibodies toward human-specific neurofilament (hNF), human-specific Thy-1 (Thy-1), neurofilament, glial fibrillary acidic protein, serotonin (5-HT), and tyrosine hydroxylase (TH). The in situ morphology of the human embryonic spinal cord was also investigated and compared with grafts that were six months older. Solid human embryonic spinal cord grafts showed a 100% survival rate, grew to fill the volume of the cavity in a noninvasive manner, and expressed human specific antigens 6 months postgrafting. Thy-1 immunoreactivity (IR) was demonstrated up to 8 mm rostral to the graft suggestive of graft-derived fiber outgrowth. hNF-IR fibers and 5-HT- and TH-IR fibers traversed the graft-host border for a few hundred micrometers, respectively. Finally, our findings suggest that grafted solid pieces of human embryonic spinal cord minimize cystic deformations seen in the adult rat spinal cord with a unilateral cavity.     

Characteristics of human fetal spinal cord grafts in the adult rat spinal cord: influences of lesion and grafting conditions

The present study evaluated the growth potential and differentiation of human fetal spinal cord (FSC) tissue in the injured adult rat spinal cord under different lesion and grafting conditions. Donor tissue at 6-9 weeks of gestational age was obtained through elective abortions and transplanted either immediately into acute resection (solid grafts) or into chronic contusion (suspension and solid grafts) lesions (i.e., 14-40 days after injury) in the thoracic spinal cord. The xenografts were then examined either histologically in plastic sections or immunocytochemically 1-3 months postgrafting. Intraspinal grafts in acute lesions demonstrated an 83% survival rate and developed as well-circumscribed nodules that were predominantly composed of immature astrocytes. Solid-piece grafts in chronic contusion lesions exhibited a 92% survival rate and also developed as nodular masses. These grafts, however, contained many immature neurons 2 months postgrafting. Suspension grafts in chronic contusion lesions had an 85% survival rate and expanded in a nonrestrictive, diffuse pattern. These transplants demonstrated large neuronally rich areas of neural parenchyma. Extensive neuritic outgrowth could also be seen extending from these grafts into the surrounding host spinal cord. These findings show that human FSC tissue reliably survives and differentiates in both acute and chronic lesions. However, both the lesion environment and the grafting techniques can greatly influence the pattern of differentiation and degree of host-graft integration achieved.     

Love, courage, and honor

OBJECTIVES: Despite the increasing success of whole-organ pancreas transplantation, the success of clinical islet allografts has remained limited. One of the factors limiting the success is the difficulty in monitoring islet allografts after transplantation. The aim of these studies is to develop a method of "biopsying" human islet allografts using a forearm islet implantation site. METHODS: A subtherapeutic number of isolated human islets were placed in the forearm under the muscle fascia in three human recipients with Type I insulin dependent diabetes. All of the recipients had undergone successful cadaveric renal transplantation at least one year prior and were maintained on their baseline immunosuppression. Aliquots of the islet grafts were removed 7 and 14 days to assess engraftment and graft infiltrate. To verify that the islets were viable, 400 were handpicked and transplanted into B6-scid mice made diabetic with streptozotocin. RESULTS: The biopsy site was found in all three cases. In one patient, no islets were recovered. In two other patients, viable islet tissue was recovered 7 days after transplantation. Immunohistology at 7 days showed the presence of both insulin and glucagon-staining cells in the islets. At 14 days in these two patients, a mononuclear cell infiltrate was observed in the explanted islet biopsies. Immunohistology showed the relative absence of insulin-staining cells with intact glucagon-staining cells. This finding is consistent with recurrent autoimmunity in the islet grafts. DISCUSSION: This preliminary study shows that the forearm biopsy site is a useful method to retrieve human islet grafts after transplantation. The islets engraft and are easily found in the first weeks after transplantation. These data suggest that recurrent autoimmunity may affect islet allografts. Further studies will be needed to determine if the histology in the forearm will correlate with the fate of intraportal or intraperitoneal islet allografts. Although they were shown to reduce the incidence of early allograft failure, their influence on the long-term graft survival remains to be proven.     

Assessment of donor cell and matrix survival in fresh articular cartilage allografts in a goat model

The long-term survival of allografts of articular cartilage has been proposed to be dependent on the survival of the cells that maintain the unique structural and material properties of the allograft. In this study, we assessed cell survival in 24 fresh articular cartilage allografts of the medial plateau in a Spanish-goat model. A DNA-probe technique was used to distinguish clearly between DNA from donor (allograft) and host cells. The intraarticular survival of viable allograft chondrocytes in the transplanted articular cartilage started to diminish as early as 3 weeks after transplantation; however, there was considerable variation in the amount of donor cell DNA detected in the allografts at 6 and 12 months following transplantation. This contrasts with our experience with fresh allografts of ligament, tendon, and meniscus, in which no donor DNA was detected 4 weeks after transplantation. DNA from host cells was present in all articular cartilage allografts, as evidenced by detectable unique host DNA patterns. Histological and histochemical assays showed that none of the transplants demonstrated normal structure and composition at 1 year after transplantation. The grafts in which large quantities of donor DNA were present appeared grossly superior to those with no or reduced remaining demonstrable donor DNA.