Jorma Halttunen

Chronic rejection in rat aortic allografts. An experimental model for transplant arteriosclerosis.

Chronic rejection has several histological appearances, depending on the type of organ graft. Common to all of them is transplant arteriosclerosis associated with an ongoing inflammatory response in the transplanted graft. To the contrary of classical atherosclerosis, in which the manifestations are mostly focal, proximal, and asymmetric, transplant arteriosclerosis is generalized, and the intimal thickening is concentric. In this article, we describe an experimental animal model whereby transplant arteriosclerosis may be investigated in the inbred rat. Aortic allografts were transplanted from DA (RTIa) to major histocompatibility complex-incompatible WF (RTIv) rats or, for control, to rats of the DA strain. Transplantation was followed by an acute inflammation episode in the aortic adventitia of the allograft, largely lacking in the syngeneic graft, with a prominence of lymphoid activation markers (Cd25) in the cells of the inflammatory infiltrate. The inflammation episode peaked at 2 months after transplantation, became attenuated, and was followed by a proliferative response of myocytes in the allograft media. An increase in the migration of myocytes to the subendothelial space (presumably through small breaks generated in the internal elastic lamina) was observed thereafter, and myocyte proliferation continued in the intima with some intermingled macrophages. Finally, necrosis and disappearance of myocytes and their replacement by fibrous tissue were observed in the media. These alterations are virtually identical with the vascular lesion of chronically rejecting parenchymal organ transplants in human subjects. We suggest that aortic allografts exchanged between histoincompatible rat strains may be used as an experimental model for transplant arteriosclerosis.

Endoscopic treatment of pancreatic pseudocysts

BackgroundThis study aimed to assess the effectiveness of therapeutic endoscopy in the treatment of pancreatic pseudocysts, and to define factors limiting endoscopic therapy.MethodsThe results of therapeutic endoscopy were evaluated for 170 patients with pancreatic pseudocysts treated at the Department of Surgery, Helsinki University Central Hospital, during the 6-year period from 1998 to 2003.ResultsThe therapeutic endoscopy success rate was 86.1%, with 23 (13.9%) patients requiring operative treatment because therapeutic endoscopy was unsuccessful or technically impossible. There was little morbidity and no procedure-related mortality. The majority of the 38 complications, which arose from 380 procedures, could be treated conservatively.ConclusionsEndoscopic methods are safe and effective for the treatment of pancreatic pseudocysts. The indications for surgery include inaccessible pancreatic duct, location, or content of the pseudocyst rendering the problem not amenable to endoscopic therapy, as well as complications of the endoscopic treatment.

Chronic rejection of rat aortic allograft: II. Administration of cyclosporin induces accelerated allograft arteriosclerosis

Abstract. Rat aortic allografts immunosuppressed with cyclosporin ‐ but not with azathioprine or steroids ‐ develop an early inflammatory lesion in the subendothelial space. This “endothelialitis” is followed by an influx of proliferating smooth muscle cells into the intima, resulting in intimal thickening and accelerated arteriosclerosis. Administration of azathioprine and steroids largely ameliorates the development of the accelerated lesion. Similar endothelialitis and accelerated arteriosclerosis have been observed previously in the autopsy material of cardiac transplant recipients. Our results confirm the suggestion that the development of accelerated allograft arteriosclerosis is most likely linked to cyclosporin administration.

Intestinal adaptation after massive proximal small-bowel resection in the pig

BACKGROUND Small-intestinal adaptation to resection has been extensively studied in rats. The present study investigates morphology, crypt cell proliferation, and disaccharidase activities of the remaining small intestine and colon after 75% proximal resection of porcine small intestine. METHODS Specimens were obtained from the proximal jejunum, middle and distal ileum, and proximal colon preoperatively (n = 5) and 14 weeks after small-bowel transection (n = 5) or resection (n = 5). Proliferation was analyzed immunohistochemically with the Ki-67 antigen MIB-1. Disaccharidase activities were determined in accordance with the method of Dahlqvist. RESULTS In addition to macroscopic enlargement, resection markedly increased the villi and crypts of the remaining small bowel. Crypt cell proliferation decreased with advancing age after transection but remained at the preoperative level after resection. Specific, but not total, activities of maltase and sucrase in the mid-ileum decreased after resection. CONCLUSION Small-intestinal adaptation in the pig involves macroscopic enlargement and a prompt increase in villus size, which is associated with high crypt cell proliferation.

Impact of class II major histocompatibility complex antigen expression on the immunogenic potential of isolated rat vascular endothelial cells.

We have investigated the immunogenic potential of rat heart vascular endothelial cells by their ability to induce an accelerated rejection of a relevant heart allograft, and related the immunogenic potential to the expression of class II major histocompatibility complex (MHC) antigens on the endothelial cell surface. Only 12% of freshly isolated rat vascular endothelial cells express class II antigens in serum-free medium, and the level of expression is low as judged by immunoperoxidase staining and/or the ability of endothelial cells to bind staphylococci to the cell surface after treatment with monoclonal antibodies to the class II molecule. On the other hand, 99% of the endothelial cells under the same conditions express class I, and the level of expression is high. The class II antigen expression of vascular endothelial cells can be upregulated to more than 98% by recombinant gamma-interferon in vitro—and, con

Evidence that lymphocyte traffic into rejecting cardiac allografts is CD11a- and CD49d-dependent.

Acute cardiac allograft rejection is characterized by infiltration of leukocytes into tissue parenchyma, but the site of entry and endothelial adhesion molecules involved are not yet defined. Lymphocyte binding to frozen sections prepared from day-3 rejecting cardiac allografts was significantly increased compared with sections made from normal hearts (number of bound lymphocytes, 983±216 per mm2 vs. 309±121, respectively, P<0.001) or syngeneic grafts. The bound lymphocytes were located exclusively only on the top of the capillary structures and not on any other sites on the heart vasculature. We further wanted to analyze which of the cloned endothelial adhesion molecules and their counterreceptors would be involved in the increased lymphocyte binding. Lymphocyte pretreatment with

Ileal nutritional function after one-stage orthotopic ileum transplantation in the growing pig: Reversal of lethal short bowel syndrome

Intestinal isolation is associated with hypoplasia of defunctioned mucosa and reduction in the segmental absorption, whereas the presence of luminal nutrition is essential for the expression of the ileal adaptive response after proximal small bowel resection. On the other hand, intensive postoperative graft monitoring is obligatory because of the disastrous consequences of small bowel graft rejection. Thus, the authors sought to develop an experimental ileum transplantation model that provided immediate graft placement in bowel continuity, together with readily available graft monitoring connection through a proximal Roux-en-Y enterostomy. Four groups of pigs were prepared: RESTX (n = 9), proximal 50% small bowel resection with simultaneous orthotopic ileum autotransplantation; RES (n = 7), proximal 50% small bowel resection; NONRES (n = 6), transection; and SB (n = 5), short bowel. Early (1 to 4 weeks) and long-term (5 to 12 weeks) studies of animal growth, nutritional status, disaccharide absorption, water and electrolyte balances, and liver function were performed after ileum autotransplantation (IAT) in relation to small intestine of variable length with undivided mesentery (intact neural and lymphatic connections). The perioperative transplantation mortality rate remained at about 10%. Reasons not related to the transplantation procedure accounted for the late complication rate of 38%. In the ileum autotransplantation (RESTX) group, weight gain was recovered 2 to 3 weeks after transplantation, and the mean weight reached the preoperative level at 5 weeks. The SB pigs underwent progressive weight loss. The transection (NONRES) and proximal resection (RES) animals gained weight at similar rates. IAT had no effect on the plasma protein concentrations. Proximal resection, with or without IAT, was associated with depressed plasma cholesterol contents in the early period. Plasma cholesterol levels amended long-term, after both IAT and proximal resection. IAT resulted in deficient intraluminal processing of maltose, whereas isolated proximal resection tended to enhance disaccharide absorption early after the surgery. The short bowel pigs were not able to preserve sufficient nutritional status, and demonstrated a marked decline in the hemoglobin, protein, and cholesterol levels. No biochemical signs suggestive of potential liver damage caused by portocaval graft vascularization were recognized. These findings suggest that one-stage ileum autotransplantation provides sufficent absoprtive capacity to reverse otherwise lethal short bowel syndrome in the growing pig. However, transplantation disturbs the in vivo absorptive function of the nonrejecting ileum. Long-term impairment in disaccharide absorption may be partially related to an altered intestinal adaptive response secondary to proximal resection when combined with simultaneous transplantation. The authors developed this ileal small bowel transplantation model using rapidly growing pigs, wherein body weight gain represents an objective parameter of intestinal absorptive function. Only this type of animal model can yield clinically relevant data in the evaluation of a transplants ability to provide sufficient nutritional function in a growing recipient.

Adaptive lipid metabolism after ileal autotransplantation in pigs with proximal gut resection

BACKGROUND Transplantation of the small intestine impairs intestinal absorptive function, but the adaptive response of a segmental graft is unknown. The aim of this study was to investigate the effects of ileal autotransplantation on the adaptive absorption and metabolism of lipids in pigs that had undergone proximal gut resection. METHODS Serum lipids, plasma vitamins A and E, absorption and excretion of cholesterol, bile acids and fat, plasma cholesterol precursor and plant sterol proportions to cholesterol (respective markers of cholesterol synthesis and absorption), enteric structure, and transit were determined 4, 8, and 14 weeks after 75% proximal resection with (n = 15) or without (n = 15) autotransplantation of the remaining ileum. RESULTS As compared with pigs that underwent proximal gut resection, the additional autotransplantation reduced the adaptive increase in total serum and high-density lipoprotein cholesterol, plasma plant sterol proportions and vitamin E concentrations, cholesterol and fat absorption efficiency, and villus height (p < 0.05 for all) during the 14 postoperative weeks and resulted in increases of up to 4.6, 2.7, 1.3, and 2.1 times the plasma cholesterol precursors (p < 0.005), fecal excretion of bile acids (p < 0.0005), neutral steroids (p < 0.005), and net elimination of cholesterol (p < 0.0005), respectively. Cholesterol and fat absorption and plasma plant sterols were significantly enhanced between 8 and 14 weeks after autotransplantation (p < 0.05, p < 0.005, and p < 0.05, respectively), whereas fecal elimination of cholesterol remained increased until the end of the follow-up. CONCLUSIONS Autotransplantation of the ileum in pigs that have undergone proximal small bowel resection disturbs the adaptive absorption of cholesterol, bile acids, fat, and fat-soluble vitamins, resulting, through increased fecal elimination of cholesterol, in decreased serum cholesterol despite a marked compensatory increase in cholesterol synthesis.

Frequency and Functional Characterization of Specific T-Helper Cells Infiltrating Rat Kidney Allografts during Acute Rejection

T‐helper cells (ThC) play an important role in the induction of both cytotoxic T‐cell responses and B‐cell responses against the grafted organ. Furthermore, ThC alone are capable of causing graft rejection in T cell‐deprived mice and rats. In view of these observations we found it important to analyse the frequency and functions of donor‐specific ThC in the allograt and in the recipient lymphoid system during the course of acute renal allograft rejection. A limiting dilution assay was developed which, due to the absence of exogenous interleukin 2 (IL‐2) and the low numbers of stimulator cells used, appears to be highly selective for the proliferation of specific ThC. Kidney transplants were performed from LBN (RT1n) to congenic Lewis (RT11) sirain differing in major histocompatibilily complex (MHC) only. The inflammatory (white) cells were recovered from the graft, and blood and recipient spleen and the frequency of RT1n‐ responding ThC were determined at different times after transplantation. In the kidney graft itself, the frequency of ThC responding to RT1n MHC antigens was 1:3000 on day 2 and increased to l:670–1320 at the peak of inflammation. In the spleen, the frequency increased from l:l000 on day 0 to 1:200 on day 8, and remained high even after the graft was rejected. In the blood, the frequency stayed at the 1:400–1:800 level, and increased to 1:200 only after the graft had been completely destroyed. Individual ThC clones deriving from limited dilution assays of kidney and spleen cells were recovered and expanded with irradiated donor cells without IL‐2 and finally with exogenous IL‐2 only. All clones showed the T‐helper (W3/25) phenolype, seven out of eight tested clones showed a specific anamnestic response lo RT1n alloantigens and no response to RT11 or RT1a in a secondary MLC, 12 out of 12 clones produced IL‐2 and 11 out of 11 clones produced gamma interferon upon re‐stimulation with relevant allogeneic cells, and eight out of ten clones collaborated with syngeneic B cells for Ig synthesis, indicating that they were indeed derived from specific ThC and/or from their precursors. Taken together, the results demonstrate that specific ThC and/or their precursors represent only a very small minority in the graft‐infiltrating inflammatory population. This makes it most unlikely that ihe ThC themselves are responsible for graft destruction; the results indicate rather that a major role of ThC in situ may be instruction of immunologically specific and nonspecific components of inflammation.

Failure of rat kidney nephron components to induce allogeneic lymphocytes to proliferate in mixed lymphocyte kidney cell culture.

Rat kidney glomerular mesangial, glomerular epithelial, and tubular epithelial, cells were isolated in virtually pure form and studied in mixed lymphocyte kidney cell culture (MLKC) for their ability to induce allogeneic spleen lymphocyte proliferation. The responses were compared with proliferative responses induced by allogeneic endothelial cells or spleen lymphocytes in the same strain combination. Stimulator cells were treated or left untreated with gamma-interferon, known to increase the major histocompatibility complex class II (and class I) expression of the stimulator cells. The results demonstrate that the nephron components are not able to induce lymphoproliferation in the MLKC. In contrast, the endothelial cells of rat heart were potent inducers of lymphoproliferation in mixed lymphoeyte endothelial cell cultyres (MLEC), as were allogeneic spleen cells. Although the kidney parenchymal cells have been shown to be immunogenie in vivo, the present finding suggests that they are unable to function as antigen-preseting cells on their own.