Biomedical subjects

C Ricordi

Publications and source records attributed to C Ricordi.

At least 199 records · Page 11Linked to original sources

PubMed1994

Mixed xenogeneic chimerism (mouse+rat-->mouse) to induce donor-specific tolerance to sequential or simultaneous islet xenografts.

We previously reported that donor-specific rat islet xenografts were accepted by fully xenogeneic (rat-->mouse) chimeras when the islets were transplanted at least six weeks following reconstitution. The purpose of the present study was to examine whether a similar outcome would occur for mixed xenogeneic (mouse+rat-->mouse) chimeras if the islets were placed coincident with the time of bone marrow infusion. As with fully xenogeneic chimeras (rat-->mouse), synchronous donor-specific F344 rat (Rt1A1) islet xenografts were significantly prolonged (MST > 139 days) in mixed xenogeneic (mouse+rat-->mouse) chimeras, while MHC-disparate third-party WF rat (Rt1Au) grafts were rejected (MST = 21.2 days). The transplanted donor-specific islets were functional to maintain euglycemia and they were regulated in function to respond to a glucose challenge. For potential clinical application, it would be of obvious benefit if the islet xenografts could be placed at the time of bone marrow transplantation. We therefore performed similar studies using donor islets administered simultaneously with bone marrow. Donor-specific islet xenografts were permanently accepted by all mouse recipients (n = 5). When MHC-disparate third-party rat islets were transplanted, only 3 of 8 islet xenografts were rejected; the other 5 remained functional from 77 to 90 days posttransplantation. Although prolonged and functional, the MHC-disparate islets that were accepted exhibited histologic evidence of fibrosis and rejection, while those matched to the donor did not. These data therefore suggest that donor-specific islet xenografts are permanently accepted if placed simultaneously or sequentially following mixed xenogeneic bone marrow reconstitution.

Animals↗

PubMed1994

Acceleration of chronic failure of intrahepatic canine islet autografts by a short course of prednisone.

A topic of current interest in islet transplantation is the selection of an optimal site for long-term graft survival since the intrahepatic site may be characterized by long-term failure. Additionally, the use of immunosuppressive agents such as prednisone may adversely affect long-term graft function. In this study, we examined the long-term outcome of intrahepatic canine islet autografts and compared this with results obtained in animals treated with a short-term course of steroids or steroids plus insulin. Islets were isolated using the automated method and were purified on discontinuous Euro-Collins Ficoll gradients (densities: 1.108, 1.096, 1.037). Prednisone-treated dogs were hyperglycemic during treatment but returned to normoglycemia after steroid withdrawal. Control and insulin-treated animals were normoglycemic following autotransplant, with no difference in plasma glucose levels between controls and the insulin-treated animals. All control dogs became diabetic at 11, 14, 17, and 19 months following islet autograft. Prednisone-treated dogs had more rapid onset of diabetes at 7, 11, and 12 months following ITx. Prednisone-treated dogs given insulin became hyperglycemic at 10, 14, 18, and 19 months post ITx. Graft failure was preceded by a decline in IVGTT Kg values and diminished insulin secretion. At the time of graft failure islets showed no lymphocytic infiltration and islets stained positive for glucagon but few insulin-containing cells were seen. Thus, even when an initially adequate B cell mass was transplanted, the intrahepatic site was characterized by long-term canine autograft failure. A short course of prednisone accelerated the time to graft failure and insulin treatment reversed this acceleration.

Animals↗

PubMed1994

Control of cytosolic free calcium in cultured human pancreatic beta-cells occurs by external calcium-dependent and independent mechanisms.

Changes in cytosolic intracellular free Ca2+ ([Ca2+]i) in response to glucose, glyburide, cholinergic agonists, and elevated [K+]o (external potassium concentration) were measured in cultured human islet beta-cells. In the absence of glucose, the mean resting [Ca2+]i in single beta-cells was 84.5 +/- 4.7 nM (n = 86) and remained unchanged in low external [Ca2+]o (Ca2+ concentration) (< 0.2 microM) at 23-25 C. Glucose (5.6-33 mM) induced a slow dose-related [Ca2+]i rise up to 300.0 +/- 50.6 nM (n = 19). This [Ca2+]i rise always occurred with a delay that varied from cell to cell (approximately 10-120 sec), and the steady state [Ca2+]i exhibited a sigmoidal dependence on glucose concentration (midpoint at 14.9 mM). The glucose-induced rise in [Ca2+]i was attenuated by about 62% in low external [Ca2+]o and was not affected by dantrolene, a drug that inhibits Ca2+ release from the endoplasmic reticulum. In the absence or presence of glucose, cholinergic receptor agonists evoked a biphasic increase in [Ca2+]i up to 350 nM; the delayed component of the [Ca2+]i rise was blocked by dantrolene. A rapid elevation of [K+]o to 40 mM also elicited a biphasic rise in [Ca2+]i, which peaked at about 250 nM and was inhibited by the Ca2+ channel antagonist nifedipine. Glyburide (4 microM) in the absence of glucose also induced a [Ca2+]o-dependent rise in [Ca2+]i. Increasing the concentration of glucose from 4 to 16.7 mM evoked a biphasic pattern of insulin secretion from perifused isolated islets at 37 C. Finally, in the presence of 4 mM glucose, a cholinergic muscarinic receptor agonist stimulated insulin secretion. A glucose-stimulated [Ca2+]i rise was also studied at 24 and 37 C in cultured rat islet cells. Our results suggest that the Ca2+ required for glucose-induced and muscarinic agonist-potentiated insulin release enters the cytosol from both extracellular and intracellular Ca2+ stores.

Calcium↗

PubMed1994