Functional and morphological assessment of rat aorta stored in University of Wisconsin and Eurocollins solutions

Dendritic Cells Expressing Triggering Receptor Expressed on Myeloid Cells-1 Correlate with Plaque Stability in Symptomatic and Asymptomatic Patients with Carotid Stenosis

Atherosclerosis is a chronic inflammatory disease with atherosclerotic plaques containing inflammatory cells, including T-lymphocytes, dendritic cells (DCs) and macrophages that are responsible for progression and destabilization of atherosclerotic plaques. Stressed cells undergoing necrosis release molecules that act as endogenous danger signals to alert and activate innate immune cells. In atherosclerotic tissue the number of DCs increases with the progression of the lesion and produce several inflammatory cytokines and growth factors. Triggering receptor expressed on myeloid cells (TREM)-1 plays a crucial role in inflammation. However, relationship of DCs and the role of TREM-1 with the stability of atherosclerotic plaques have not been examined. In this study, we investigated the heterogeneity of the plaque DCs, myeloid (mDC1 and mDC2) and plasmacytoid (pDCs), and examined the expression of TREM-1 and their co-localization with DCs in the plaques from symptomatic (S) and asymptomatic (AS) patients with carotid stenosis. We found increased expression of HLA-DR, fascin, and TREM-1 and decreased expression of TREM-2 and α-smooth muscle actin in S compared to AS atherosclerotic carotid plaques. Both TREM-1 and fascin were co-localized suggesting increased expression of TREM-1 in plaque DCs of S compared to AS patients. These data were supported by increased mRNA transcripts of TREM-1 and decreased mRNA transcripts of TREM-2 in carotid plaques of S compared to AS patients. There was higher density of both CD1c+ mDC₁ and CD141+ mDC₂ in the carotid plaques from AS compared to S patients, where as the density of CD303+ pDCs were higher in the carotid plaques of S compared to AS patients. These findings suggest a potential role of pDCs and TREM-1 in atherosclerotic plaque vulnerability. Thus, newer therapies could be developed to selectively block TREM-1 for stabilizing atherosclerotic plaques.

Effects of acrylic resin monomers on porcine coronary artery reactivity

The purpose of the present investigation was to assess the reactivity of porcine coronary arteries under in vitro conditions following their exposure to methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) monomers. Confirming previous studies using rat aortas, both MMA and HEMA induced acute/direct relaxation of coronary ring preparations, which was partly dependent on the endothelium. With prolonged tissue exposure, both monomers caused time- and concentration-dependent inhibition of receptor-mediated contraction of the vascular smooth muscle caused by prostaglandin F2∝ (PGF2∝), with HEMA causing more inhibition than MMA. Hydroxyethyl methacrylate, but not MMA, also produced impairment of non-receptor-mediated contraction of the coronary smooth muscle induced by KCl. On the other hand, neither HEMA nor MMA altered relaxation of the smooth muscle produced by the direct-acting pharmacological agent, sodium nitroprusside (SNP). While exposure to HEMA impaired endothelium-dependent vasorelaxation caused by bradykinin (BK), MMA markedly enhanced this endothelial-mediated response of the arteries. The enhanced endothelial response produced by MMA was linked to nitric oxide (NO) release. In conclusion, with prolonged tissue exposure, MMA causes less pronounced effects/adverse consequences on coronary smooth muscle function relative to the effect of HEMA, while enhancing vasorelaxation associated with release of NO from the endothelium. Accordingly, MMA-containing resin materials appear to be safer for human applications than materials containing HEMA.

Regulation of cell cycle entry by PTEN in smooth muscle cell proliferation of human coronary artery bypass conduits

Proliferation of smooth muscle cells (SMCs) is the key event in the pathogenesis of intimal hyperplasia (IH) leading to coronary artery bypass graft (CABG) occlusion. The saphenous vein (SV) conduits are often affected by IH, while the internal mammary artery (IMA) conduits remain remarkably patent. SMC proliferation is mediated by the cell cycle, under the control of cyclin-dependent kinases (cdks), cdk-inhibitors and the retinoblastoma protein (Rb). Early passage of the SMCs through the cell cycle involves crossing the non-reversible G(1) checkpoint, the restriction (R) point. In this study, we investigated the effect of mitogenic insulin-like growth factor (IGF)-1 stimulation on the R-point and its relationship with the phosphorylation of Rb protein and the cdk inhibitors p21 and p27 in SV and IMA SMCs. We observed no change in the R-point following IGF-1 activation in either SV or IMA SMCs. However, Rb-phosphorylation occurred much earlier and was quantitatively greater in SV SMCs than IMA. Overexpression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in SV SMCs followed by IGF-1 activation significantly decreased the expression of cyclin E and pRb and induced p27 expression in SV SMCs, while, pRb levels were markedly decreased and p27 levels were significantly increased in IMA SMCs. Silencing the PTEN gene by siRNA transfection of IMA SMCs significantly induced the expression of pRb and inhibited p27 expression, while, the expression levels of cyclin E, pRb, p21 and p27 were unaffected by the silencing of PTEN in SV SMCs. These results demonstrate that the PTEN plays a critical role in regulating cell cycle entry. Therefore, overexpression of PTEN possibly by means of gene therapy could be a viable option in regulating the cell cycle in SV SMCs in the treatment of vein graft disease.

Temporal PTEN inactivation causes proliferation of saphenous vein smooth muscle cells of human CABG conduits

Internal mammary artery (IMA) coronary artery bypass grafts (CABG) are remarkably resistant to intimal hyperplasia (IH) as compared to saphenous vein (SV) grafts following aorto-coronary anastomosis. The reason behind this puzzling difference still remains an enigma. In this study, we examined the effects of IGF-1 stimulation on the PI3K-AKT/PKB pathway mediating proliferation of smooth muscle cells (SMCs) of IMA and SV origin and the specific contribution of phosphatase and tensin homologue (PTEN) in regulating the IGF-1-PI3K-AKT/PKB axis under these conditions. Mitogenic activation with IGF-1, time-dependently stimulated the phosphorylation of PI3K and AKT/PKB in the SV SMCs to a much greater extent than the IMA. Conversely, PTEN was found to be significantly more active in IMA SMCs. Transient overexpression of PTEN in SMCs of SV and IMA inhibited AKT/PKB activity and upstream of AKT/PKB, caused a reduction of IGF-1 receptors. Downstream, PTEN overexpression in SV SMCs induced the transactivation of tumour suppressor protein p53 by down-regulating the expression of its inhibitor MDM2. However, PTEN overexpression had no significant effect on MDM2 and p53 expression in IMA SMCs. PTEN overexpression inhibited IGF-1-induced SMC proliferation in both SV and IMA. PTEN suppression, induced by siRNA transfection of IMA SMCs diminished the negative regulation of PI3K-PKB signalling leading to greater proliferative response induced by IGF-1 stimulation. Thus, we show for the first time that early inactivation of PTEN in SV SMCs leads to temporally increased activity of the pro-hyperplasia PI3K-AKT/PKB pathway leading to IH-induced vein graft occlusion. Therefore, modulation of the PI3K-AKT/PKB pathway via PTEN might be a novel and effective strategy in combating SV graft failure following CABG.

Involvement of connexin 43 in angiotensin II-induced migration and proliferation of saphenous vein smooth muscle cells via the MAPK-AP-1 signaling pathway

Proliferation and migration of vascular smooth muscle cells (VSMCs) lead to intimal thickening and influence the long-term patency of venous graft post coronary arterial bypass graft. There is increasing evidence that connexins are involved in the development of intimal hyperplasia and restenosis. We assessed connexin 43 (Cx43) expression and its role in angiotensin II-induced proliferation and migration of smooth muscle cells and the signal pathways involved in human saphenous vein bypass conduits. Angiotensin II significantly increased gap junctional intercellular communication and induced the expression of Cx43 in human saphenous vein SMCs in a dose- and time-dependent manner through angiotensin II type 1 receptor. The effect of angiotensin II was blocked by siRNA of ERK 1/2, p38 MAPK and JNK, respectively. Overexpression of Cx43 markedly increased the proliferation of saphenous vein SMCs. However, siRNA for Cx43 inhibited angiotensin II-induced proliferation, cyclin E expression and migration of human saphenous vein SMCs. In dual-luciferase reporter assay, angiotensin II markedly activated AP-1 transcription factor, which was significantly attenuated by a dominant-negative AP-1 (A-Fos) with subsequent inhibition of angiotensin II-induced transcriptional expression of Cx43. These data demonstrate the role of Cx43 in the proliferation and migration of human saphenous vein SMCs and angiotensin II-induced Cx43 expression via mitogen-activated protein kinases (MAPK)-AP-1 signaling pathway.

Vascular reactivity changes in glucose-intolerant rat

The vascular effects of glucose-intolerance were investigated using the neonatal streptozotocin-treated (nSTZ) rat model. Glucose-intolerance was initiated by administration of STZ (90 mg/kg, IP) into 2-day-old male rats. Aortic reactivity was assessed in vitro at 3 and 6 months of age. Both the 3- and 6-month-old nSTZ rats displayed higher blood glucose levels in response to a glucose challenge. At 3 months of age, aortic responsiveness to both norepinephrine and acetylcholine was not altered. However, at 6 months of age, the responses of endothelium-denuded aortas from nSTZ rats to norepinephrine and serotonin were enhanced compared to controls. Endothelium-mediated relaxation of aortas from these animals to acetylcholine was also augmented, and this effect was linked to NO release. Although norepinephrine did not elicit enhancement of aortic contraction in calcium-free medium in 6-month-old nSTZ rats, the responses to both maximum and submaximum concentrations of the agonist after readdition of calcium were greater in these tissues than in control preparations. Pretreatment of aortas with calphostin C eliminated the difference in NE-induced contraction between the control and experimental groups. Although the concentration-response curves for phorbol 12,13-dibutyrate were not different between the 2 groups, the responses of the aortas from 6-month-old nSTZ rats to a submaximum concentration of the phorbol ester were enhanced relative to controls, and this enhancement was normalized with calphostin C. Overall, the data suggest that glucose-intolerance of sufficient duration causes increases in vascular reactivity to agonists. While these findings warrant further investigations, such vascular alterations during the prediabetes stage of glucose intolerance can be a predisposing factor for the eventual development of cardiovascular complications.

Mechanics of Fresh, Refrigerated, and Frozen Arterial Tissue

Arterial grafts and experimental soft tissues are commonly preserved using refrigeration and freezing. The present study was designed to investigate effects of common storage protocols on arterial mechanics. Porcine aortas were axially distracted to failure implementing fresh, refrigerated, and frozen storage conditions. Fresh tissues were tested within 24 h of sacrifice; refrigerated tissues were stored at +4 degrees C for 24 or 48 h prior to testing, and frozen tissues were stored at -20 or -80 degrees C for 3 months prior to testing. Blunt arterial injury experimentally occurred in distraction with intimal subfailure before ultimate failure in 82% of specimens. Subfailure stress decreased in refrigerated (0.59 +/- 0.19 MPa) compared to fresh (0.83 +/- 0.39 MPa) and frozen (0.99 +/- 0.41 MPa) specimens. Ultimate stress was also significantly decreased in refrigerated (0.83 +/- 0.19 MPa) compared to fresh (1.15 +/- 0.39 MPa) and frozen (1.32 +/- 0.31 MPa) specimens. Subfailure and ultimate strain were not significantly dependent upon storage technique. Young's modulus significantly decreased in refrigerated (1.89 +/- 0.63 MPa) compared to fresh (2.98 +/- 1.45 MPa) and frozen (3.49 +/- 1.32 MPa) specimens. Physiological, subfailure, and ultimate failure mechanics between fresh and frozen specimens were not significantly different. Clinically relevant intimal failures can be reproduced and injury mechanics determined while adhering to experimental protocols of freezing specimens before testing. However, short-term tissue refrigeration may affect mechanics.

Increased expression of inhibitor of apoptosis proteins in atherosclerotic plaques of symptomatic patients with carotid stenosis

Vascular remodeling and atheromatous lesion formation are determined in part by the balance between apoptosis and survival of vascular smooth muscle cells (VSMCs). In the chronic stages, apoptosis of VSMCs in the atherosclerotic plaques contributes to the weakening and potential rupture of the plaque causing pathologies such as acute coronary syndrome. The higher incidence of apoptosis in the plaques of symptomatic than in asymptomatic patients has been demonstrated, but the expression of survival proteins, including the inhibitor of apoptosis proteins (IAPs), has not been thoroughly examined. The aim of this study was to investigate the immunohistochemical expression of cellular inhibitor of apoptosis protein-2 (cIAP2), x-linked inhibitor of apoptosis protein (XIAP), and survivin in normal carotid arteries, and carotid endarterectomy specimens of symptomatic and asymptomatic patients with carotid stenosis. The results demonstrated stronger immunopositivity to smooth muscle myosin heavy chain antigen (SM-MHC) (sm2), proliferating cell nuclear antigen (PCNA), and p50 subunit of NF-kappabeta in the asymptomatic plaques than in symptomatic plaques. Furthermore, there was higher expression of cIAP2, XIAP, and survivin in the symptomatic than in the asymptomatic plaques and this paralleled caspase-3 expression. The increased expression of IAPs in symptomatic plaques could be due to endogenous defense mechanism to protect against the pro-apoptotic effect of the inflammatory stimuli that are released in the plaques. This could be involved in the stabilization of symptomatic atheromatous plaques and may prove a potential therapeutic target.

Roles of nitric oxide and prostacyclin in triethyleneglycol dimethacrylate (TEGDMA)-induced vasorelaxation

OBJECTIVES

Most dental resinous materials contain the diluent monomer triethyleneglycol dimethacrylate (TEGDMA), which has been reported to be bioactive. Previously, it was demonstrated that TEGDMA induces vasorelaxation. The present study examines the mechanism(s) of the TEGDMA-induced vasorelaxation by measuring vascular nitrite and prostacyclin levels.

METHODS

Nitrite and prostacyclin levels were assayed in rat aortic tissues in response to TEGDMA. The involvement of guanylyl and adenylyl cyclases in TEGDMA-induced aortic vasorelaxation was determined using the enzyme inhibitors 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (SQ22536), respectively.

RESULTS

TEGDMA enhanced the levels of nitrites in endothelium-intact and that of protacyclin in both endothelium-intact and denuded rat aortas. The increase in nitrites was associated with endothelium-dependent aortic relaxation mediated via the activation of guanylyl cyclase, while the increase in prostacyclin was associated with both endothelium-dependent and independent relaxation linked to adenylyl cyclase stimulation.

SIGNIFICANCE

Data from the present investigation can be relevant to dental practice employing materials containing TEGDMA by providing insights into the vasorelaxant effect of the monomer following placement of the materials in the oral cavity. Additional studies that are more relevant to the clinical situation are required to confirm these initial results and further explore their implications.

Vasorelaxant effect of resin-based, single-bottle dentin bonding systems

Single-bottle dentin bonding systems are currently in wide use. Because these materials are sometimes inadvertently placed on microscopic pulp exposures while at other times deliberately on frank exposures, their effects on pulpal soft tissues need to be evaluated. The present study assessed the vascular effects of 3M Single Bond (3MSB) and Prime & Bond NT (PBNT), using rat aortic ring preparations. It is hypothesized that these bonding agents induce relaxation of these preparations. Both 3MSB and PBNT caused endothelium-dependent and -independent relaxations in a concentration-dependent manner. The endothelium-dependent relaxation was associated with the release of nitric oxide. However, the responses to both agents did not involve the generation of prostanoids or KATP channel activation. At relatively low concentrations, the responses of endothelium-denuded tissues to 3MSB were greater than those to PBNT, indicating certain differences in the vascular action between these products. The data suggest that 3MSB and PBNT interfere with vascular function by causing vasorelaxation via mechanisms occurring in the smooth muscle and endothelium, including the release of nitric oxide. Among others, this effect may promote bleeding if these adhesives are placed on pulp exposures.

Effect of taurine deficiency on adenosine receptor-mediated relaxation of the rat aorta

We recently demonstrated that chronic taurine supplementation or deficiency causes alterations in reactivity of the rat aorta to several vasoactive agents. In the present investigation, we examined the effects beta-alanine-induced endogenous taurine deficiency on the mechanical responsiveness of the isolated rat aorta to adenosine receptor stimulation with 2-chloroadenosine (CAD), 5'-N-ethylcarboxyamidoadenosine (NECA), and N(6)-cyclopentyladenosine (CPA). The adenosine analogs produced concentration-dependent (1 x 10(-9)-3 x 10(-3) M) relaxations of aortas from both control and beta-alanine-treated rats with the rank order of potencies NECA>CAD>CPA, which was consistent with A(2) receptor identification. CAD and NECA induced both endothelium-dependent and -independent relaxations of the aortas. The endothelium-dependent responses to both agents and the independent responses to CAD were significantly attenuated by beta-alanine treatment. The relaxation responses of the aortas from control and taurine-deficient rats to CAD and NECA were markedly antagonized by ZM241385 (10(-5) M), suggesting the involvement of A(2A) adenosine receptors. Further, N-nitro-L-arginine methyl ester (L-NAME; 10(-5) M) significantly attenuated the endothelium-mediated relaxation produced by CAD and NECA in both groups. However, the inhibitory effect of L-NAME was less on the beta-alanine-treated tissues, providing evidence that the effect of taurine deficiency was linked to a reduction in nitric oxide generation. As in the aorta, CAD produced both endothelium-dependent and -independent relaxation responses in the rat superior mesenteric artery, and both responses were inhibited by chronic beta-alanine treatment, suggesting that not only similar responses can be generated by a given adenosine agonist in different vascular beds, but also beta-alanine treatment modulates these responses. On the other hand, while CPA elicited only endothelium-independent aortic relaxation, this response was not altered by taurine deficiency. The results indicate that endogenous taurine deficiency causes differential inhibitory effects on adenosine receptor-mediated vasorelaxation, depending upon the agonists used. Given the recognized role of adenosine in the vasculature, these alterations suggest taurine-mediated modulation of blood flow regulation.

Taurine depletion alters vascular reactivity in rats

We recently showed that chronic taurine supplementation is associated with attenuation of contractile responses of rat aorta to norepinephrine and potassium chloride. However, the potential involvement of endogenous taurine in modulation of vascular reactivity is not known. Therefore, we examined the effect of β-alanine-induced taurine depletion on the in vitro reactivity of rat aorta to selected vasoactive agents. The data indicate that both norepinephrine- and potassium-chloride-induced maximum contractile responses of endothelium-denuded aortae were enhanced in taurine-depleted rats compared with control animals. However, taurine depletion did not affect tissue sensitivity to either norepinephrine or potassium chloride. By contrast, sensitivity of the endothelium-denuded aortae to sodium nitroprusside was attenuated by taurine depletion. Similarly, taurine deficiency reduced the relaxant responses of endothelium-intact aortic rings elicited by submaximal concentrations of acetylcholine, and this effect was associated with decreased nitric oxide production. Taken together, the data suggest that taurine depletion augments contractility but attenuates relaxation of vascular smooth muscle in a nonspecific manner. Impairment of endothelium-dependent responses, which is at least in part associated with reduced nitric oxide generation, may contribute to the attenuation of the vasorelaxant responses. These vascular alterations could be of potential consequence in pathological conditions associated with taurine deficiency.Key words: rat aorta, β-alanine, taurine depletion, vascular reactivity.

Preservation of vascular tissue under hypothermic conditions

BACKGROUND

Preservation of vascular tissue plays a crucial role in the success of organ transplantation. We investigated and compared the performance of 4 preservation solutions at preserving vascular tissue over 24, 48, and 72 h under hypothermic conditions.

MATERIALS AND METHODS

Rat aortic segments were stored in University of Wisconsin (UW), Modified University of Wisconsin (mUW), EuroCollins (EC), and Bretschneider Histidine-tryptophan-ketoglutarate (HTK) solutions at 4 degrees C for 24, 48, and 72 h. Functional assessment was performed by measuring smooth muscle cell contraction and endothelium-dependent relaxation after stimulation with phenylephrine and acetylcholine, respectively, in an organ bath.

RESULTS

UW and EC solutions were superior to the other solutions for endothelial cell preservation and were not statistically different from each other at any time (P < 0.05). Smooth muscle cell (i.e., contractile) preservation was best achieved with UW solution for up to 72 h. HTK appeared to function well at 24 h, but at 48 and 72 h, there was a major decline in contractile response and relaxation.

CONCLUSION

UW solution appears to be superior for the preservation of the functional integrity of vascular tissue stored under hypothermic conditions up to 72 h.

Vascular responsiveness to dimethylaminoethyl methacrylate and its degradation products

The increasing use of acrylate-based resins in dentistry has raised questions about the biocompatibility of these substances with oral tissues. The focus of the present investigation was to assess the responsiveness of blood vessels to the resin polymerization accelerating agent dimethylaminoethyl methacrylate (DMAEMA) and its degradation products dimethylethanolamine (DME) and methacrylic acid (MAA), using the rat aortic ring preparation as a tissue model. DMAEMA induced concentration-dependent relaxation of norepinephrine (NE)-contracted aortic rings with and without endothelium. N-nitro-L-arginine methyl ester (L-NAME) selectively inhibited the endothelium-dependent relaxation induced by DMAEMA, suggesting the release of nitric oxide from the endothelium by DMAEMA. Both indomethacin and glybenclamide attenuated the vasorelaxation elicited by DMAEMA in the presence as well as in the absence of endothelium, providing evidence for the role of vasorelaxant prostanoid(s) and K(ATP) channel activation in the responses observed. On the other hand, while MAA was without any apparent effect on the rat aorta, DMAEMA at high and DME at relatively low concentrations caused contraction of the tissues with and without endothelium in the absence of NE. The DME-induced contraction was inhibited by indomethacin, suggesting the involvement of contractile arachidonic acid metabolite(s) in the action of DME. This observation was supported by the findings of increased thromboxane A(2) (TXA(2)) production in aortic rings incubated with DME. Taken together, the data suggest that both DMAEMA and its degradation product, DME, are vasoactive, inducing vasorelaxation and contraction by various mechanisms that may involve the release of nitric oxide from the endothelium, the activation of smooth muscle K(ATP) channels, and the generation of vasorelaxant prostanoid(s) and TXA(2). These effects may play a role in tissue homeostasis and certain adverse conditions associated with the use of dental resin materials containing DMAEMA and/or DME.

The effect of perfusion with UW solution on the skeletal muscle and vascular endothelial exocrine function in rat hindlimbs

BACKGROUND

The effect of University of Wisconsin (UW) solution perfusion for extremity preservation is still unknown although it is widely used. The purpose of this study is to examine the effect of UW solution perfusion on skeletal muscle preservation in a rat model.

MATERIALS AND METHODS

Rat hindlimbs were amputated and either preserved with UW solution perfusion (UW perfusion group) or given no perfusion (no-perfusion group) for 5 h at 25 degrees C. They were then transplanted to other isogeneic rats. ATP in the muscle and serum creatine phosphokinase were measured after 24 h of reperfusion. The vascular endothelial function of the femoral artery rings was measured before and after 24 h of reperfusion in the presence or absence of indomethacin (cyclooxygenase inhibitor) and L-NMMA (nitric oxide synthase inhibitor). TEA (calcium-activated potassium channel inhibitor) was also used to verify the vasodilator function. Reperfusion blood flow was monitored during the first 2 h of reperfusion.

RESULTS

ATP in the UW perfusion group was significantly decreased after 24 h of reperfusion, while that in the no-perfusion group recovered. Reperfusion blood flow in the UW solution perfusion group was significantly lower than that in the no-perfusion group. Acetylcholine-induced relaxation in the UW perfusion group was significantly reduced before and after 24 h of reperfusion compared to that in the no-perfusion group and was mostly diminished by indomethacin and L-NMMA administration.

CONCLUSIONS

Skeletal muscle injury is augmented by UW solution perfusion, probably due to deterioration of the vascular endothelial function resulting in blood supply diminution.

Comparison of vascular smooth muscle cell apoptosis and fibrous cap morphology in symptomatic and asymptomatic carotid artery disease

The biological cascades that lead to carotid plaque disruptions and symptoms are largely unknown. Certain cellular events within the plaque might be responsible for destabilizing the plaque, though the popular belief is that the plaque size is directly related to symptoms. The aim of our study was to assess the morphology of the fibrous cap and apoptosis in the plaque and compare these two pathological features in symptomatic and asymptomatic carotid artery disease. Our work was carried out in plaques obtained following carotid endarterectomy performed for symptomatic disease (including hemispheric transient ischemic attacks, amaurosis fugax, or stroke) or asymptomatic high-grade severe stenosis. Scion images of Gomori's stained sections were used to measure fibrous cap thickness and area. TUNEL assay was performed to assess the extent of apoptosis. The results indicated that the area of the fibrous cap did not significantly correlate with the presence of symptoms. There was a higher percentage of apoptotic nuclei and the thinner fibrous cap in symptomatic plaques than in asymptomatic plaques. This finding suggests that these factors might be involved in destabilizing plaque, causing rupture and leading to symptomatic carotid disease.

In vitro function of porcine carotid arteries preserved in UW, HTK and Celsior solutions

We compared the efficacy of histidine-tryptophan-ketoglutarate (HTK) and University of Wisconsin (UW) solution with Celsior solution using hypothermically-preserved porcine carotid arteries and studied the importance of different components of these solutions by preserving carotid arteries in modified HTK solutions. Excised carotid arteries were stored at 4 degrees C in 0.9% (w/v) NaCl, UW, HTK, Celsior, or a modified HTK solution for up to 14 days. Preservation-induced changes in smooth muscle cell and endothelial cell function were determined using an organ bath for isometric tension recording. Short-term preservation (1-3 days) in UW, HTK and Celsior did not significantly alter contractile and relaxation responses of arterial segments when compared to freshly-excised segments, but significantly impaired these responses in arterial segments stored in 0.9% (w/v) NaCl solution. Long-term hypothermic preservation of arterial segments (7 and 14 days) in 0.9% (w/v) NaCl and HTK solution almost completely abolished all responses, but only slightly reduced the responses of arterial segments stored in UW solution. Intermediate results were obtained for Celsior. Modifying HTK by replacement of chloride for sulfate and phosphate resulted in improved contractile and relaxation responses after long-term preservation. With respect to smooth muscle and endothelial function, UW is superior to HTK and Celsior and the absence of chloride or presence of sulfate and phosphate plays a relevant role in this in vitro model of hypothermic preservation of porcine carotid arteries.

Effect of hyperthermic preconditioning on cold preserved rat portal veins

BACKGROUND/AIMS

Little information is available regarding the effect of cold storage and hyperthermic preconditioning on the contractile responses of hepatic vessels. We then studied, after cold preservation, the in vitro contractile responses of rat portal veins (RPV) isolated from normal rats or from rats previously subjected to hyperthermia.

METHODS

Rats were or were not subjected to hyperthermia 24 h before the RPV isolation. Then, RPV were stored at 4 degrees C in Krebs-Henseleit bicarbonate (KHB) or University of Wisconsin solution or conserved at 20 degrees C in KHB solution. Control RPV were tested after rat sacrifice.

RESULTS

The contractile responses were importantly decreased in RPV conserved at room temperature. The morphology of the vessels was altered and the heat shock protein 70 (Hsp70) protein expression disappeared. These abnormalities were prevented by cold preservation. The type of preservation solution did not interfere with the beneficial effect. Hyperthermic preconditioning increased the expression of Hsp70 protein in freshly isolated and cold preserved RPV but decreased the contractile responses. In RPV conserved at room temperature, hyperthermic preconditioning further worsened the decreased contractile response.

CONCLUSIONS

Thus, hyperthermic preconditioning, which is beneficial in protecting hepatic injury following cold preservation, alters the contractile responses of RPV.

Effects of dental resin components on vascular reactivity

The frequent use of resins in dentistry has raised the question of their compatibility with oral tissues. The present study was undertaken to determine the effects of the resin components methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), and triethylene glycol dimethacrylate (TEGDMA) on the reactivity of blood vessels using the isolated rat aorta as a tissue model. MMA, HEMA, and TEGDMA caused endothelium-dependent and -independent relaxation of rat aortic rings in a concentration-related manner. The endothelium-dependent responses of the tissues to all the resins were significantly attenuated by N-nitro-L-arginine methyl ester (L-NAME), indicating the involvement of nitric oxide. The vasorelaxant effects of both MMA and TEGDMA on the intact and denuded aortae were markedly inhibited by indomethacin, providing evidence for the role of prostanoids in these responses. Glybenclamide selectively attenuated TEGDMA-induced relaxation of the tissues with and without endothelium to a similar extent, suggesting the activation of vascular smooth muscle K(ATP) channels by this resin. It is concluded that MMA, HEMA, and TEGDMA interfere with the function of blood vessels by inducing vasorelaxation via different mechanisms, which, depending upon the type of resin, may at least involve the release of nitric oxide and prostanoid(s), and the activation of smooth muscle K(ATP) channels. These phenomena may play a role in tissue homeostasis and certain pathophysiological conditions associated with the application of resin materials to the oral environment.

Cold storage preservation and warm ischaemic injury to isolated arterial segments: endothelial cell injury

Injury to endothelial cells is thought to be important to the development of the vascular lesion of chronic rejection. It was the aim of this study to develop a semiquantitative method to assess endothelial injury in arterial grafts and to document the injury produced by cold storage preservation and additional warm ischaemia. Twelve- and 24-h cold preservation of rat aortic segments, together with an additional 1 h of warm ischaemia, were assessed. Electron micrographs of representative endothelial cells were scored for cytoplasmic, nuclear and mitochondrial injury. The overall injury score was obtained by addition of the individual scores. Storage for up to 24 h in University of Wisconsin (UW) and Terasaki did not produce any injury. Twenty-four hours of storage in Euro-Collins resulted in endothelial cell death. Injury occurred after 12 h of storage in Ross, Collins and normal saline, and the injury increased following 24 h of storage. One hour of warm ischaemia did not increase the injury. Injury to endothelial cells varies with the preservation solution used and the time of cold storage, so that both the type of solution and the storage time should be taken into account in clinical studies looking at the influence of cold ischaemia time and graft outcome.

Endothelial damage during myocardial preservation and storage

Preservation and storage techniques represent two major issues in routine cardiac surgery and heart transplantation. Historically, these methods were conceived to prevent ischemic injury to myocardium after cardiac arrest during heart operations. Evidence shows that endothelium plays a critical role in the maintenance of normal heart function after cardiac operation, mainly by controlling the coronary circulation. Methods for preservation and storage, developed initially to protect cardiomyocyte function, may be deleterious for vascular endothelium and compromise myocardial protection. In this review article the present knowledge about endothelial injury secondary to preservation and storage techniques is discussed.

Functional assessment of rat aorta after cold storage in different media

Cold storage is frequently used to store isolated blood vessels for a limited period of time. However preservation of vascular smooth muscle and endothelial functions is time and medium-dependent. The present study was designed to compare the reactivity of rat aorta before and after cold storage for 24 and 48 h in one of four different solutions consisting of Hepes-buffered Krebs solution, Belzer solution, Krebs solution, and Eurocollins solution. Smooth muscle and endothelial functions of the rat aorta were assessed using in vitro isometric tension measurement. The results obtained for vessels preserved for 24 and 48 h were compared with those for vessels studied immediately after harvesting. Sensitivity and maximum contraction to KCl and norepinephrine were not altered in rat aorta preserved up to 48 h in Hepes-Krebs and Belzer solutions. In contrast, the amplitude of contraction elicited by KCl was significantly reduced by 50% and 77% in aorta stored for 24 and 48 h in Krebs solution and by 77% and 96% in those stored in Eurocollins solutions. Similarly, the maximal contraction elicited by norepinephrine was significantly reduced by 60% and 45% in arteries stored for 24 and 48 h in Krebs solution and by 34% and 86% in those stored in Eurocollins solution. In contrast, cold storage in the different media did not alter the relaxations elicited by sodium nitroprusside and forskolin. The endothelium-dependent relaxations in response to acetylcholine were not statistically modified after preservation up to 48 h in Hepes-Krebs solution. In contrast, the maximal relaxations to acetylcholine were significantly decreased after storage for 24 and 48 h in Belzer, Krebs and Eurocollins solutions. These results suggest that among the four media studied, Hepes-Krebs solution is the most suitable medium for the storage of blood vessels under hypothermic conditions.

Ultrastructural analysis of human endothelial cells after hypothermic storage in organ preservation solutions

BACKGROUND

Protection of vascular endothelium is a critical factor in organ preservation for transplantation. This study aims at a morphological assessment of endothelial cell injury in a comparison of storage solutions, using a cell culture model of cold preservation and rewarming.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVEC) were cultured in monolayer and exposed to hypothermic storage in University of Wisconsin (UW), histidine-tryptophane-ketoglutarate (HTK), and EuroCollins solutions for 6 h and subsequent rewarming for 30 min or 6 h. Alterations of subcellular structures and cell-cell contacts were analyzed by transmission electron microscopy (TEM) and light microscopic assessment after actin and nuclear staining.

RESULTS

Structural alterations of mitochondria, endoplasmic reticulum, nuclei, and cytoskeletal fibers as well as disruption of intercellular contacts were found after cold storage in HTK and EuroCollins solutions. In contrast, storage in UW solution resulted in minimum changes of stress fibers only. A rapid rearrangement of structural alterations was achieved during rewarming in cell culture medium in all experimental groups.

CONCLUSIONS

Preservation of endothelial cell structure is best achieved by UW solution. Ultrastructural cell damage is a direct consequence of hypothermic storage and is fully reversible during rewarming after short storage times.

Functional assessment of human femoral arteries after cryopreservation

PURPOSE

An established method of cryostorage that might preserve the vascular and endothelial responses of human femoral arteries (HFAs) to be transplanted as allografts was studied.

METHODS

HFAs were harvested from multiorgan donors and stored at 4 degrees C in Belzer solution before cryostorage. One hundred eleven HFA rings were isolated and randomly assigned to 1 control group of unfrozen HFAs and 2 groups of HFAs cryopreserved for 7 and 30 days, respectively. Cryopreservation was performed in Elohes solution containing dimethyl sulfoxide (1.8 mmol/L), and the rate of cooling was 1.6 degrees C/min, until -141 degrees C was reached. The contractile and relaxant responses of unfrozen and frozen/thawed arteries were assessed in organ bath by measurement of isometric force generated by the HFAs.

RESULTS

After thawing, the maximal contractile responses to all the contracting agonists tested (KCl, U46619 [a thromboxane A2-mimetic], norepinephrine, serotonin, and endothelin-1) were in the range of 7% to 34% of the responses in unfrozen HFAs. The endothelium-independent relaxant responses to forskolin and verapamil were weakly altered, whereas the endothelium-independent relaxant responses to sodium nitroprusside were markedly reduced. Cryostorage of HFAs also resulted in a loss of the endothelium-dependent relaxant response to acetylcholine. The vascular and endothelial responses were similarly altered in the HFAs cryopreserved for 7 and 30 days.

CONCLUSION

The cryopreservation method used provided a limited preservation of HFAs contractility, a good preservation of the endothelium-independent relaxant responses, but no apparent preservation of the endothelium-dependent relaxation. It is possible that further refinements of the cryopreservation protocol, such as a slower rate of cooling and a more controlled stepwise addition of dimethyl sulfoxide, might allow better post-thaw functional recovery of HFAs.

Deuterium oxide-based University of Wisconsin solution improves viability of hypothermically stored vascular tissue

BACKGROUND

Preservation of vascular function largely determines the outcome of transplantation. We have investigated replacing the water (H2O) in University of Wisconsin (UW) solution with deuterium oxide (D2O) in an attempt to improve vascular function after hypothermic storage.

METHODS

Rat aortic segments were stored in UW solutions based on 100% H2O, 25% D2O, 50% D2O, and 100% D2O at 4 degrees C for 24, 48, or 72 hr. Vascular function was measured via contraction and endothelium-dependent relaxation after stimulation with phenylephrine and acetylcholine.

RESULTS

UW solution with 25% D2O gave a significant (P<0.05) improvement of contraction and relaxation in comparison with H2O-based UW solution and other concentrations of D2O.

CONCLUSIONS

Low concentrations (25%) of D2O-UW solution are significantly superior to the H2O-based (i.e., commonly used) equivalent at up to 72 hr. These results suggest that low concentrations of D2O-UW solution can improve the quality of hypothermic storage.

Functional and morphological evaluation of canine veins following preservation in different storage media

Injuries of endothelial and smooth muscle cells of autologous vein due to preservation in standard storage media may be responsible for graft failure. The effects of vein preservation with University of Wisconsin solution (UWs) on endothelial and smooth muscle cell function and morphology were compared to the effects of preservation with autologous whole blood (AWB) and normal saline (NS), which are frequently used in cardiovascular surgery. Canine external jugular and common femoral vein segments were preserved in the different solutions at 4 degrees C for 45 min and 24 hr. Rings (4-5 mm in length) from control and preserved veins were evaluated by isometric tension studies at 37 degrees C and by scanning and transmission electron microscopy. Differences between groups were evaluated by Student's t test or Mann-Whitney U test and by analysis of the variance, and considered to be significant at P < 0.05. Sensitivities to norepinephrine (NE) showed that a 45-min vein storage in AWB (5.7 +/- 0.2 mumol/L) but not in NS (5.8 +/- 0.2 mumol/L) or UWs (6.5 +/- 0.2 mumol/L) had a deleterious effect on function of smooth muscle (P < 0.05) when compared to control veins (6.6 +/- 0.2 mumol/L). Maximum contractile responses and sensitivities to NE were significantly altered (P < 0.05) after 24-hr vein storage in AWB (0.09 +/- 0.02 g/mm2 and 5.4 +/- 0.07 mumol/L) and NS (0.12 +/- 0.03 g/mm2 and 5.6 +/- 0.08 mumol/L) but not in UWs (0.36 +/- 0.06 g/mm2 and 6.4 +/- 0.07 mumol/L). With both storage times, acetylcholine-induced endothelium-dependent maximum relaxations and sensitivities were significantly reduced (P < 0.05) in veins stored in AWB and NS, but not in UWs, compared with controls. Similarly, transmission electron microscopy revealed marked neutrophil migration beneath the intimal surface of vessels and extensive separation and desquamation of endothelial cells with exposure of subendothelial structures in veins stored in AWB and NS. The results suggest that UWs is a suitable storage medium when compared to AWB and NS.

Addition of calcium to Euro-Collins solution is essential for 24-hour preservation of the vasculature

BACKGROUND

Genuine Euro-Collins solution is calcium free. The aim of this study was to investigate whether the addition of calcium would improve its capacity to preserve the vasculature.

METHODS

The infrarenal aorta of Sprague-Dawley rats was investigated in organ baths: as fresh controls, after 24 hours of cold (4 degrees C) storage in Euro-Collins solution, or in Euro-Collins solution with the addition of calcium in amounts ranging from 0.05 to 1.5 mmol/L. The thromboxane analogue U-46619 was used to investigate contractility. Endothelium-dependent relaxation was tested by cumulative addition of acetylcholine. Papaverine was used to elicit endothelium-independent relaxation. Investigation by transmission electron microscopy was also performed.

RESULTS

Storage of rat aorta for 24 hours in genuine Euro-Collins solution almost abolished smooth muscle function, and severe edema was found in the endothelial cells. However, if calcium was added, the rat aorta could be stored for 24 hours without affecting smooth muscle function, and endothelium-dependent relaxation was only slightly reduced. Furthermore, only slight edema could be demonstrated in the endothelial cells.

CONCLUSIONS

If calcium is added to Euro-Collins solution in amounts ranging from 0.4 to 1.5 mmol/L, it allows good preservation of rat aorta for 24 hours. Without calcium, this solution destroys both the function and morphology of the vessels.

Short-term preservation of autogenous vein grafts: effectiveness of University of Wisconsin solution

BACKGROUND

Suboptimal preservation of autologous veins in storage solutions causes endothelial cell damage that can contribute to graft failure. The purpose of this study was to compare the effects of short-term storage of veins in autologous whole blood (AWB), 0.9% normal saline solution (NS), and University of Wisconsin solution (UWs) on vein structure and function after grafting.

METHODS

Autogenous jugular and femoral veins were atraumatically harvested from mongrel dogs. One vein segment was immediately implanted to serve as a control, and the other segments were stored for 45 minutes in AWB, NS, or UWs. The veins were implanted as reversed interposition graft in the carotid or femoral arteries. After 6 weeks light and scanning electron microscopy and isometric tension studies were performed on explanted vein grafts.

RESULTS

Morphologic studies revealed an intact endothelium that stained positively for factor VIII. Intimal thickness was similar between controls (48 +/- 12 microns) and veins stored in UWs (53 +/- 8 microns) (p = not significant), but it was significantly increased in veins stored in AWB (151 +/- 29 microns) and NS (149 +/- 18 microns) (p < 0.05). Sensitivity and maximum contraction to norepinephrine were not altered in veins preserved in UWs (6.0 +/- 0.1 mumol/L and 0.19 +/- 0.02 gm/mm2) but were significantly reduced (p < 0.05) in those stored in AWB (7.2 +/- 0.1 mumol/L and 0.08 +/- 0.02 gm/mm2) and NS (7.0 +/- 0.3 mumol/L and 0.09 +/- 0.02 gm/mm2) compared with controls (5.9 +/- 0.2 mumol/L and 0.20 +/- 0.02 gm/mm2). The sensitivity and maximum relaxation to acetylcholine and sodium nitroprusside of veins preserved in AWB, NS, and UWs were similar to controls (p = not significant).

CONCLUSIONS

Vein storage in UWs preserves smooth muscle cell function compared with veins stored in NS or AWB. Therefore UWs is a more suitable medium for short-term preservation of veins in cardiovascular operation.

Viscoelastic properties of human arteries. Methodology and preliminary results

In order to study the biomechanical properties of the arterial wall and to compare arteries with different histologic structures, we designed a device that allows testing of arterial segments under near-physiologic conditions. A hydrodynamic generator simulates systolo-diastolic pressures in an open loop. An intraarterial pressure sensor and a sonomicrometer connected to two piezoelectric crystals placed in diametric opposition on the arterial wall allow computer calculation of compliance, stiffness, midwall radial arterial stress, Young modulus, and incremental modulus for a given arterial segment at a given pressure setting. Seven healthy common carotid artery (CCA) segments and seven healthy (superficial) femoral artery (FA) segments were studied immediately after removal from brain-dead donors between the ages of 18 and 35 years. Histologic examination was performed to determine the density of elastic fibers in the arterial wall. Hysteresis was observed in all segments regardless of pressure settings. Compliance was greater and modulus values and stiffness were lower in CCA than in FA. No evidence of structural change was noted after testing in the circulation loop. These preliminary results open the way to a wide variety of applications for our hydrodynamic circulation loop. Experiments will be undertaken to compare the mechanical properties of arteries before and after cryopreservation.

Effect of temperature in long-term preservation of vascular endothelial and smooth muscle function

BACKGROUND

In clinical transplantation the donor organ is perfused with a cold preservation solution to obtain quick core cooling and a suitable environment for the tissue cells. Without good preservation of the vasculature, progressive deterioration of the blood flow during reperfusion may ultimately lead to the no-reflow phenomenon, even though the function of the other cells in the organ may be adequately preserved. The aim of this study was to find the optimal storage temperature for preservation of the vasculature.

METHODS

The infrarenal aorta of 126 Sprague-Dawley rats were studied in organ baths: as fresh controls, after 36 hours of storage at 0.5 degrees C, 4 degrees C, 8.5 degrees C, and 22 degrees C in University of Wisconsin solution, and after 36-hour storage followed by transplantation and a lapse of 2 hours, 24 hours, and 7 days. The thromboxane analogue U-46619 was used to test contractility. Acetylcholine was used to elicit endothelium-dependent relaxation (EDR), and papaverine to elicit endothelium-independent relaxation.

RESULTS

Storing the vessels at 0.5 degree C proved best regarding preservation of contractility, with a nonsignificant decrease, whereas storage at 4 degrees C and 8.5 degrees C resulted in a significant decrease after 36 hours. The contractility did not recover within 24 hours of in vivo reperfusion, but full recovery was seen after 7 days. Regardless of the preservation temperature used, a significant impairment in EDR was seen after 36 hours of storage. Two hours after transplantation, vessels stored at 4 degrees C and 8.5 degrees C showed no significant impairment in EDR, whereas those stored at 0.5 degrees C demonstrated a significant loss of EDR. After 24 hours and after 7 days, EDR was normal in all groups.

CONCLUSIONS

Endothelium-dependent relaxing factor function is best preserved at 4 degrees C and 8.5 degrees C, whereas preservation of vascular smooth muscle function is best preserved at 0.5 degrees C.

Importance of calcium in long-term preservation of the vasculature

BACKGROUND

The aim was to investigate the effect of calcium in organ preservation solutions with respect to 36-hour preservation of vascular smooth muscle function and endothelium-dependent relaxation.

METHODS

The infrarenal aortas of 60 Sprague-Dawley rats were studied in organ baths as fresh controls and after 36 hours of cold (4 degrees C) storage in different preservation solutions with and without calcium. The thromboxane A2 analogue U-46619 was used to study contractility. Endothelium-dependent relaxation was tested by the cumulative addition of acetylcholine. Papaverine hydrochloride was used to elicit endothelium-independent relaxation.

RESULTS

Krebs solution was the only solution able to fully preserve contractility. Krebs solution without calcium gave poor preservation. After the addition of 1.5 mmol/L of calcium to University of Wisconsin solution and to Perfadex, both these solutions became fully able to preserve contractility. None of the solutions (with or without calcium) were fully able to preserve endothelium-dependent relaxation, although University of Wisconsin solution gave good preservation and Perfadex, fair preservation. Euro-Collins solution and K+ (124 mmol/L)-enriched Krebs solution were not able to preserve smooth muscle function or endothelium-dependent relaxation.

CONCLUSIONS

Calcium is essential for long-term preservation of vascular smooth muscle function but not for long-term preservation of endothelium-dependent relaxation.

Perfadex is superior to Euro-Collins solution regarding 24-hour preservation of vascular function

BACKGROUND

The aim of this study was to compare Perfadex with Euro-Collins solution regarding 24-hour preservation of endothelium-dependent relaxation and vascular smooth muscle function.

METHODS

The infrarenal aorta of 72 isogenic rats was studied in organ baths as fresh controls, after 24 hours of cold (4 degrees C) storage, and after 24-hour storage followed by transplantation and examination after 7 or 30 days. The thromboxane A2 analogue U-46619 was used to test contractility. Acetylcholine chloride was used to elicit endothelium-dependent relaxation and papaverine hydrochloride, to elicit endothelium-independent relaxation.

RESULTS

With both solutions, all grafts were patent after 7 and 30 days. Vessels preserved in Euro-Collins solution for 24 hours lost 95% (p < 0.001) of their contractility compared with fresh controls; 7 days after transplantation, they had regained 40% of initial contractility, and after 30 days, there was no significant decrease in contractility. Vessels preserved in Perfadex manifested no significant decrease in contractility at any time. Endothelium-dependent relaxation could not be evaluated in vessels stored for 24 hours in Euro-Collins solution because they had lost almost all contractility; 7 days after transplantation, endothelium-dependent relaxation was reduced by 65% (p < 0.001), but at 30 days after transplantation, there was no significant decrease in endothelium-dependent relaxation. Vessels preserved in Perfadex for 24 hours lost 17% (p < 0.05) of endothelium-dependent relaxation, but 7 and 30 days after transplantation, there was no significant decrease in endothelium-dependent relaxation.

CONCLUSIONS

Perfadex, but not Euro-Collins solution, has the capacity to preserve vascular function after 24 hours of storage followed by in vivo reperfusion.

Long-term preservation of vascular endothelium and smooth muscle

This study was performed in organ baths on 400 ring segments of infrarenal aorta taken from 40 Sprague-Dawley rats that had been randomized into five groups. Contractility was tested with the thromboxane analogue U-46619. Acetylcholine was used to elicit endothelium-dependent relaxing factor (EDRF). The results obtained from vessels preserved at 4 degrees C for 6, 12, 24, and 36 hours were compared with those from autologous vessels studied immediately after harvesting. Vessels preserved in Euro-Collins solution showed a 46% (p < 0.01) decrease in contractility after 12 hours of storage; after 24 hours only weak contractions could be elicited, and after 36 hours they had lost their ability to contract. The EDRF function was slightly reduced after 12 hours and could not be investigated after 24 and 36 hours. With the University of Wisconsin solution (UW) and the low-potassium-dextran-glucose solution Perfadex no decrease in contractility was seen in the first 24 hours, but at 36 hours the vessels preserved in UW had lost 40% (p < 0.01) and those preserved in Perfadex 30% (p < 0.05) of their contractility. The EDRF function was significantly reduced by about 15% after 6, 12, and 24 hours in both the UW and the Perfadex groups. At 36 hours, vessels stored in Perfadex had lost 41% (p < 0.001) and those stored in UW 17% (p < 0.01) of their EDRF function.(ABSTRACT TRUNCATED AT 250 WORDS)