Long-term type 1 diabetes enhances in-stent restenosis after aortic stenting in diabetes-prone BB rats.

Type 1 diabetic patients have increased risk of developing in-stent restenosis following endovascular stenting. Underlying pathogenetic mechanisms are not fully understood partly due to the lack of a relevant animal model to study the effect(s) of long-term autoimmune diabetes on development of in-stent restenosis. We here describe the development of in-stent restenosis in long-term (~7 months) spontaneously diabetic and age-matched, thymectomized, nondiabetic Diabetes Prone BioBreeding (BBDP) rats (n = 6-7 in each group). Diabetes was suboptimally treated with insulin and was characterized by significant hyperglycaemia, polyuria, proteinuria, and increased HbA(1c) levels. Stented abdominal aortas were harvested 28 days after stenting. Computerized morphometric analysis revealed significantly increased neointima formation in long-term diabetic rats compared with nondiabetic controls. In conclusion, long-term autoimmune diabetes in BBDP rats enhances in-stent restenosis. This model can be used to study the underlying pathogenetic mechanisms of diabetes-enhanced in-stent restenosis as well as to test new therapeutic modalities.

Development of transplant vasculopathy in aortic allografts correlates with neointimal smooth muscle cell proliferative capacity and fibrocyte frequency.

OBJECTIVE: Transplant vasculopathy consists of neointima formation in graft vasculature resulting from vascular smooth muscle cell recruitment and proliferation. Variation in the severity of vasculopathy has been demonstrated. Genetic predisposition is suggested as a putative cause of this variation, although cellular mechanisms are still unknown. Using a rat aorta transplant model we tested the hypothesis that kinetics of development of transplant vasculopathy are related to neointimal smooth muscle cell proliferative capacity and fibrocyte frequency, the latter being putative neointimal smooth muscle ancestral cells. METHODS: Aortic allografts were transplanted in Lewis and Brown Norway, as well as MHC-congenic Lewis.1N and Brown Norway.1L recipients. Severity of transplant vasculopathy was quantified 4, 8, 12 and 24 weeks after transplantation. Host-endothelial chimerism, as a reflection of vascular injury, was determined by specific immunofluorescence. Neointimal smooth muscle cell proliferative capacity was determined in vitro and in situ. Fibrocyte frequency and phenotype were determined after in vitro culture by cell counting, immunofluorescence and in situ zymography. RESULTS: Compared to Lewis, Brown Norway recipients developed accelerated transplant vasculopathy which is dependent on the presence of Brown Norway non-MHC-encoded determinants. Accelerated transplant vasculopathy was associated with increased levels of host-endothelial chimerism and increased neointimal smooth muscle cell proliferation, the latter being accompanied by increased endothelial and smooth muscle cell-derived neuropilin-like protein mRNA expression. Moreover, accelerated transplant vasculopathy was associated with increased frequency of circulating gelatinase-expressing CD45(+)vimentin(+) fibrocytes. CONCLUSION: Susceptibility for transplant vasculopathy appears to be genetically controlled and correlates with neointimal smooth muscle cell proliferative capacity and circulating fibrocyte frequency.

Dichotomous effects of rosiglitazone in transplantation-induced systemic vasodilator dysfunction in rats.

BACKGROUND: Transplantation-induced systemic endothelial dysfunction causes severe cardiovascular morbidity and mortality after transplantation. Interventions that improve systemic endothelial function after transplantation and furthermore reduce intragraft vascular dysfunction might improve graft and patient survival. Treatment with the PPARgamma agonist rosiglitazone is an intervention that potentially fulfills these criteria. In this study, we determined the effect of rosiglitazone treatment on transplantation-induced endothelial dysfunction and vasomotor activity in an experimental model for chronic transplant dysfunction in rats. METHODS: Lewis abdominal aortic allografts were orthotopically transplanted into Brown Norway recipients that received either regular chow or chow containing rosiglitazone (approximately 4.2 mg/day). Endothelium-dependent (response to metacholine) and total (response to sodium nitrite) vasodilatory responses were determined in autologous thoracic aortic rings using an ex vivo organ bath setup. Measurements were performed 8 weeks after transplantation. RESULTS: Aortic allografting induced systemic endothelial dysfunction as measured by reduced endothelium-dependent vasodilation in the recipient's vascular system. Rosiglitazone treatment restored endothelium-dependent vasodilatory responses to pretransplantation levels. However, rosiglitazone treatment reduced the total dilatory response despite normalized endothelial function, indicating impairment of vascular smooth muscle cell vasomotor activity. CONCLUSIONS: Rosiglitazone treatment after allogeneic transplantation restores endothelial function but impairs vascular smooth muscle cell vasomotor activity. This dichotomous effect of rosiglitazone might impede use of rosiglitazone after organ transplantation since this potentially increases cardiovascular risk despite improved endothelial cell function.

Rosiglitazone attenuates transplant arteriosclerosis after allogeneic aorta transplantation in rats.

BACKGROUND: Transplant arteriosclerosis is a leading cause of chronic transplant dysfunction and is characterized by occlusive neointima formation in intragraft arteries. Development of transplant arteriosclerosis is refractory to conventional immunosuppressive drugs and adequate therapy is not available. In this study, we determined the efficacy of the synthetic peroxisome proliferator-activated receptor (PPAR)-gamma agonist rosiglitazone to attenuate the development of transplant arteriosclerosis in rat aortic allografts. METHODS: Lewis aortic allografts were transplanted into Brown Norway recipient rats. Recipient rats received either approximately 5 mg rosiglitazone/day (starting 1 week before transplantation until the end of the experiment) or were left untreated. Transplant arteriosclerosis was quantified using morphometric analysis. Alloreactivity was measured in vitro using mixed lymphocyte reactions. Regulatory T cell frequency and function were analyzed using flow cytometry and in vitro suppression assays, respectively. Intragraft gene expression was analyzed using real-time polymerase chain reaction. Finally, medial and neointimal vascular smooth muscle cell proliferation was analyzed in vitro. RESULTS: Rosiglitazone significantly reduced transplant arteriosclerosis development 8 weeks after transplantation (P<0.01 vs. nontreated). Rosiglitazone reduced T cell alloreactivity which was not mediated through modulation of CD4+CD25+FoxP3+ regulatory T cells. Reduced development of transplant arteriosclerosis coincided with reduced intragraft expression of stromal-derived factor-1alpha and platelet-derived growth factor receptor-beta. Finally, rosiglitazone reduced growth-factor-driven proliferation of both medial and neointimal vascular smooth muscle cells in vitro, which was not mediated through PPARgamma. CONCLUSION: PPARgamma agonists may offer a new therapeutic strategy in clinical transplantation to attenuate the development of transplant arteriosclerosis and thereby chronic transplant dysfunction.

Cytomegalovirus-enhanced development of transplant arteriosclerosis in the rat; effect of timing of infection and recipient responsiveness.

Cytomegalovirus (CMV) is put forward as a risk factor for transplant arteriosclerosis (TA). In this article, we studied CMV-enhanced development of TA in rats in different donor/recipient combinations in relation to the timing of infection. Recipient rats transplanted with an aortic allograft (BN to Lew) were infected with rat CMV (RCMV) at different time-points relative to transplantation. The virus-induced effects on TA development were also determined in other strain combinations (PVG to AO and DA to WF). Finally, transmission of RCMV from aortic grafts and its effect on TA was studied. RCMV infection enhanced TA development only in Lew recipients and only after infection early post-transplantation (days 1-5). Virus transmission to the recipient only occurred from 5 and 10 days infected aortic donor-grafts, however without affecting TA development. These data indicate that the acute alloresponse and acute CMV infection need to occur simultaneously to enhance TA. This effect, however, appears to be strain combination dependent and therefore cannot be generalized.

Thymectomy should be the first choice in the protection of diabetes-prone BB rats for breeding purposes.

Diabetes-prone (DP)-BB rats spontaneously develop diabetes and are widely used as an animal model for the study of type 1 diabetes. Since DP-BB rats develop diabetes before or at the time of breeding, such rats used for breeding need to be protected against diabetes development by the transfer of regulatory T cells obtained from diabetes-resistant (DR)-BB rats, by insulin treatment or by thymectomy. Thymectomy of juveniles is not commonly used to protect DP-BB rats, and we investigated whether breeding with thymectomized DP-BB rats was a realistic alternative to the two other methods. No differences in pregnancy rates, numbers of pups per litter or growth rates of pups were found. Moreover, no differences were found in diabetes development in the offspring. Protection of juvenile DP-BB rats by thymectomy is comparable to the other established procedures, is simple and safe, and the rats recover well from the procedure. Breeding with thymectomized animals will reduce the number of animals needed, and it improves the well-being of the animals because it reduces the negative side effects associated with the other procedures such as episodes of hypo and hyperglycaemia. Therefore, although thymectomy is an invasive procedure, we would like to recommend weanling thymectomy as the first choice for the protection of DP-BB rats for breeding purposes.

Positively charged biomaterials exert antimicrobial effects on gram-negative bacilli in rats.

Biomaterial-centered infection is a much-dreaded complication associated with the use of biomedical implants. Although positively charged biomaterial surfaces stimulate bacterial adhesion, it has been suggested that surface growth of adhering Gram-negative bacilli is inhibited on positively charged surfaces. In the present paper, we determined the infection rate of differently charged poly(methacrylates) in rats. To this end, 2 x 10(6)/cm(2) Escherichia coli O2K2 or 2 x 10(4)/cm(2) Pseudomonas aeruginosa AK1 were seeded on glass discs coated with three differently charged poly(methacrylates) coatings in a parallel plate flow chamber. Three rats received six subcutaneous discs (two discs of each charge variant) seeded with E. coli, while three other rats received discs seeded with P. aeruginosa. The numbers of viable bacteria on the surfaces were determined 48h after implantation. On 50% of all positively charged discs viable E. coli were absent, while the negatively charged discs were all colonized by E. coli. P. aeruginosa, however, were isolated from both positively and negatively charged discs. Probably, P. aeruginosa can circumvent the antimicrobial effect of the positive charge through the formation of extracellular polysaccharides.

Short-term dietary adjustment with a hydrolyzed casein-based diet postpones diabetes development in the diabetes-prone BB rat.

From earlier studies it appears that weaning associated changes in the animal's physiology and that of the pancreas in particular, render diabetes-prone Bio-Breeding (DP-BB) rats susceptible to the induction and development of insulin-dependent diabetes mellitus (IDDM). In this study we tested whether a short-term dietary adjustment at weaning would influence the development of diabetes later in life. For this purpose a diet in which the protein source was replaced with hydrolyzed casein (HC) was given to the rats from weaning to 60 days of age and from weaning to 130 days of age. The control group received the cereal-based standard diet throughout the experiment. The short-term dietary adjustment resulted in a significant delay of diabetes development. The rats fed the HC diet from weaning to 130 days of age showed a lower incidence of diabetes at 130 days of age. No differences were seen in the histological insulitis scores between the rats of the different treatment groups. Interestingly, when testing (mucosal) immune functions of short-term HC-fed rats, their mesenteric lymph node cells (MLNC) showed increased interferon-gamma (IFN-gamma) and reduced interleukin-10 (IL-10) production after in vitro stimulation. These results demonstrate that short-term dietary adjustments at a young age can influence the course of diabetes later in life. The shift in cytokine profile of MLNC of the HC-fed rats suggests that mechanisms involved can be at the level of both the (mucosal) immune system and the beta cell.

Origin of vascular smooth muscle cells and the role of circulating stem cells in transplant arteriosclerosis.

To date, clinical solid-organ transplantation has not achieved its goals as a long-term treatment for patients with end-stage organ failure. Development of so-called chronic transplant dysfunction (CTD) is now recognized as the predominant cause of allograft loss long term (after the first postoperative year) after transplantation. CTD has the remarkable histological feature that the luminal areas of intragraft arteries become obliterated, predominantly with vascular smooth muscle cells (VSMCs) intermingled with some inflammatory cells (transplant arteriosclerosis, or TA). The development of TA is a multifactorial process, and many risk factors have been identified. However, the precise pathogenetic mechanisms leading to TA are largely unknown and, as a result, adequate prevention and treatment protocols are still lacking. This review discusses the origin (donor versus recipient, bone marrow versus nonbone marrow) of the VSMCs in TA lesions. Poorly controlled influx and subsequent proliferative behavior of these VSMCs are considered to be critical elements in the development of TA. Available data show heterogeneity when analyzing the origin of neointimal VSMCs in various transplant models and species, indicating the existence of multiple sites of origin. Based on these findings, a model considering plasticity of VSMC origin in TA in relation to severity and extent of graft damage is proposed.

Role of peritoneal macrophages in cytomegalovirus-induced acceleration of autoimmune diabetes in BB-rats.

BACKGROUND: As one of the natural perturbants, infection with cytomegalovirus (CMV) is believed to play a role in the development of Type I diabetes. Using the DP-BB rat model for autoimmune diabetes, we here report about possible mechanisms responsible for R(at)CMV-induced accelerated onset of diabetes. METHODS: Rats were i.p. infected with 2 x 10(6) plaque forming units (pfu) RCMV and followed for diabetes development. Presence of RCMV antigens and DNA was analyzed by immunohistochemistry and PCR on pancreatic tissue and isolated islets. The effect of viral infection on peritoneal macrophages (pMphi) and diabetes development was studied by analyzing numbers of pMphi, virus permissiveness and by depletion of this subset by peritoneal lavage. RESULTS: RCMV accelerated onset of diabetes without infecting pancreatic islets. Immunohistochemistry and PCR on pancreas and isolated islets indicated that islets are non-permissive for RCMV. Infection results in an influx of pMphi 1 day p.i. of which approximately 0.05% showed signs of reproductive infection. Depletion of pMphi on days 1-3 p.i. completely counteracted the accelerating effect of RCMV. INTERPRETATION: RCMV accelerates onset of diabetes without infecting pancreatic islets. pMphi might function as an carriage to disseminate virus to the pancreas where they enhance activation of autoreactive T cells resulting in accelerated onset of diabetes.

Cytomegalovirus infection modulates cellular immunity in an experimental model for autoimmune diabetes.

BACKGROUND: Viral infections are thought to play a role in the development of autoimmune diseases like type 1 diabetes. In this study we investigated the effect of Rat Cytomegalovirus (RCMV) infection on cellular immunity in a well-defined animal model for diabetes, the Biobreeding (BB) rat. METHODS: Diabetes prone (DP)- and Diabetes resistant (DR)-BB rats were infected with 2 x 10(6) plaque forming units (pfu) RCMV. Diabetes development was monitored by frequent blood-glucose analysis. Effects of RCMV on CD4+, CD8+ and Vbeta-TCR+ T-cell subsets were measured in vivo, and in vitro after restimulation with RCMV-infected fibroblasts. Proliferative capacity was determined by 3H-Thymidine incorporation. RESULTS: RCMV-infection resulted in a significant acceleration of diabetes onset in DP-BB rats (p = 0.003). Percentages CD4+ and CD8+ T-cells were not affected in vivo. In vitro, RCMV-restimulation resulted in a decreased CD4+/CD8+ blastoid T-cell ratio compared to ConA (p = 0.00028). Furthermore, RCMV-restimulation resulted in a strong RCMV-specific proliferation, which comprises about 50% of the response triggered by ConA. Vbeta-TCR percentages did not change upon RCMV-infection or RCMV-restimulation. INTERPRETATION: RCMV-restimulation of splenic T-cells in vitro resulted in a strong RCMV-specific proliferation, probably also including autoreactive T-cells. In vivo, this polyclonal response might be involved in the observed accelerated diabetes development in DP-BB rats upon RCMV-infection.

Temporary, but essential requirement of CD8+ T cells early in the pathogenesis of diabetes in BB rats as revealed by thymectomy and CD8 depletion.

Autoimmunity-prone BB rats demonstrate a T lymphocytopenia and abnormal T cell subset distribution. To test whether the life span of all T cells or only of certain subsets is reduced in BB rats, we thymectomised 8-week-old BB and PVG rats and subsequently assessed size and composition of the T cell population over a 6-week-period. In both strains, thymectomy (Tx) was followed by a decrease in peripheral T cell numbers, which was proportionally larger in BB rats. The decline of the Thy-1+ recent thymic migrant (RTM) T cell phenotype was similar in both strains. BB rats showed a rapid preferential loss of CD8+ and CD45RC+ T cells, whereas the relative loss of RT6+ T cells was proportional to that of all T cells and not significantly different from that in PVG rats. Tx at 8-week did not prevent diabetes. Tx of 4-week-old BB rats revealed essentially the same changes in peripheral T cell subset distribution as in 8-week-old animals. However, Tx at week 4 did prevent diabetes. Since this raised the possibility of a temporary requirement of CD8+ T cells for the development of diabetes, we performed CD8 depletions during different pre-diabetic intervals. We found that CD8 depletion from 4 to 8 and 4 to 14 weeks, but not from 8 to 14 weeks of age prevented diabetes. We conclude that the protective effect of early adult Tx is, at least in part, due to the rapid loss of CD8+ T cells, and that these cells are only required between 4 and 8 weeks of age for diabetes to develop in BB rats.

Timing of pentoxifylline treatment determines its protective effect on diabetes development in the Bio Breeding rat.

Diabetes-prone Bio Breeding (DP-BB) rats spontaneously develop diabetes between 60 and 120 days of age. Diabetes-resistant (DR)-BB rats can be induced to develop diabetes by poly(I:C) and anti-RT6. Here, we studied the effect of pentoxifylline, a potent anti-inflammatory agent, on diabetes development in both BB rat models of insulin-dependent diabetes mellitus and investigated whether these effects were related to differential modulation of tumour necrosis factor (TNF)-alpha and interleukin-10. When DP-BB rats received pentoxifylline from day 60 onwards, diabetes development was delayed and reduced. The other treatment protocols had no effect. In DR-BB rats, pentoxifylline treatment resulted only in a delay of diabetes development. In both BB rat models, in vivo pentoxifylline treatment potently suppressed TNF-alpha, but only moderately affected interleukin-10 production in vitro. These results show that timing of pentoxifylline treatment determines its protective effect on diabetes development in DP-BB rats. The observed pentoxifylline-induced increase of the interleukin-10/TNF-alpha ratio might be a mechanism for protection or delay of the diabetes development.

In vitro and in vivo antimicrobial activity of covalently coupled quaternary ammonium silane coatings on silicone rubber.

Biomaterial-centered infection is a dreaded complication associated with the use of biomedical implants. In this paper, the antimicrobial activity of silicone rubber with a covalently coupled 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride (QAS) coating was studied in vitro and in vivo. Gram-positive Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis HBH, 102, and Gram-negative Esherichia coli O2K2 and Pseudomonas aeruginos AK1 were seeded on silicone rubber with and without QAS-coating, in the absence or presence of adsorbed human plasma proteins. The viability of the adherent bacteria was determined using a live/dead fluorescent stain and a confocal laser scanning microscope. The coating reduced the viability of adherent staphylococci from 90% to 0%), and of Gram-negative bacteria from 90% to 25% while the presencc of adsorbed plasma proteins had little influence. The biomaterials were also subcutaneously implanted in rats for 3 or 7 days, while pre- or postoperatively seeded with S. aureus ATCC 12600. Preoperative seeding resulted in infection of 7 out of 8 silicone rubber implants against 1 out of 8 QAS-coated silicone rubber implants. Postoperative seeding resulted in similar infection incidences on both implant types, but the numbers of adhering bacteria were 70% lower on QAS-coated silicone rubber. In conclusion, QAS-coated silicone rubber shows antimicrobial properties against adhering bacteria, both in vitro and in vivo.