Didier Plissonnier

In situ allograft replacement of infected infrarenal aortic prosthetic grafts: Results in forty-three patients *

PURPOSEnDissatisfaction with conventional methods of treatment of infected infrarenal aortic prosthetic grafts and excellent long-term results reported by heart surgeons after allograft replacement for management of infections involving the ascending aorta have prompted us to investigate allograft replacement in the management of arterial infections.nnnMETHODSnFrom October 1988 to April 1992, 43 consecutive patients with infected infrarenal aortic prosthetic grafts underwent in situ replacement with preserved allografts obtained from cadavers as part of a program to retrieve multiorgan transplant tissue. Thirty-four patients had isolated prosthetic infections, whereas nine had aortoenteric fistulas. One patient had a concomitant below-knee amputation for septic arthritis of the ankle as a result of septic emboli. Nineteen patients had nonvascular-associated procedures, including 17 intestinal procedures.nnnRESULTSnFive patients (12%) died after operation: four of general causes and one of rupture of the native aorta as a result of persistent infection. Three patients successfully underwent repeat operation for allograft-related complications (one case each of occlusion, septic rupture, and graft-enteric fistula). All surviving patients were discharged after control angiography showed patent allografts. Two patients were unavailable for follow-up. The other 36 patients have been monitored with serial duplex and computed tomography scanning for a mean follow-up of 13.8 months (range 1 to 42 months). There were four late deaths: three were unrelated to the vascular operation, and one may have been caused by late persistent or recurrent infection. Nine patients (26%) have had pathologic changes in the allograft, with three (9%) requiring repeat operation. There were no early or late postoperative amputations in the entire series.nnnCONCLUSIONSnAlthough complete protection against persistent or recurrent infection has not been achieved and late deterioration may be expected, in situ allograft replacement seems to be a major advance in the management of infected infrarenal aortic prosthetic grafts.

Allograft-induced arterial wall injury and response in normotensive and spontaneously hypertensive rats.

The role of genetically determined immune attack and blood pressure in graft rejection-induced arterial wall injury and response was assessed by studying the compliance and changes in wall structure of aortic isografts and allografts in normotensive (Wistar-Kyoto [WKY]) and hypertensive (spontaneously hypertensive [SHR]) rats. Six groups of 8-week-old rats were compared: sham-operated in both strains, isografts, and allografts between the two strains (SHR aortas grafted in WKYs, designated SWs; WKY aortas grafted in SHRs, designated WSs; isografts in SHRs, designated SSs; and isografts in WKYs, designated WWs). Each arterial graft was studied 8 weeks after transplantation for volume and compliance (pressures of 75-175 mm Hg) under basal conditions. The amounts of collagen, elastin, and nuclei in the media and intima of the walls of control and grafted aortas were quantified morphometrically. Isografts and controls had the same mechanical characteristics under basal conditions: the arterial volume and arterial compliance of hypertensive rats were lower than those of normotensive rats (p less than 0.001). Allografts had a greater initial volume (p less than 0.001) and a lower compliance (p less than 0.001) than did isografts. Allografts in SHRs (SSs) were initially dilated, whereas allografted WKYs (WWs) were not. There was intimal proliferation in hypertensive isografts (14 +/- 0.77 microns) and in both types of allografts (WS, 69 +/- 1.55 microns; SW, 44 +/- 1.81 microns); nucleus density was higher in hypertensive allografts (WS) than in normotensive allografts (SW); and collagen density was also higher in SW than in WS allografts. Allografts had decreased medial thickness and decreased smooth muscle cell density.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct and Indirect Effects of Alloantibodies Link Neointimal and Medial Remodeling in Graft Arteriosclerosis

Objective—Chronic vascular rejection, the main cause of allograft failure, is characterized by the destruction of smooth muscle cells (SMCs) in the media concomitantly with the proliferation of SMCs in the adjacent neointima. We hypothesized that alloantibodies might be responsible for these 2 opposite but coordinated events. Methods and Results—We used the rat aortic interposition model of chronic vascular rejection. During the rejection process, a neointima composed of proliferating SMCs from the recipient developed, whereas the SMCs in the media, all of donor origin, underwent apoptosis. Alloantibody deposition was detected only in the media. Using in vitro cultures experiments, we observed that alloantibody binding to donor SMCs exerts (1) a rapid upregulation of the transcription of growth factors genes, followed by (2) the induction of apoptosis after 24 hours. The transient production of growth factors by donor SMCs in response to the binding of alloantibodies induced the proliferation of recipient SMCs in culture supernatant transfer experiments. Additional data suggest that among the repertoire of alloantibodies, those directed against major histocompatibility complex I might carry the remodeling effect. Conclusions—Our data suggest that during chronic vascular rejection, alloantibody binding to donor medial SMCs is a crucial event that links neointimal and medial remodeling.

PATHOPHYSIOLOGICAL ROLE OF THE VASCULAR SMOOTH MUSCLE CELL

The vascular smooth muscle cell of the arterial media plays a predominant role in functional and structural alterations of the arterial wall in pathophysiological processes such as arterial hypertension, atheroma, or normal aging. The observed alterations are related to the three activities of the vascular smooth muscle cell, namely contractility, secretion of proteins from the extracellular matrix, and proliferation and migration. In arterial hypertension, vascular smooth muscle cells are functionally more contracted and structurally hypertrophie, and more collagen is secreted than under normal conditions. Similar structural changes are observed in the normal aging process. With respect to vascular smooth muscle cells, atheroma is characterized by their subintimal migration and proliferation, and by excessive excretion of collagen associated with other phenotypic modifications that are expressed in their regression to a myofibroblastic state. Regardless of the pathophysiological context, these phenotypic modifications of the vascular smooth muscle cell are always linked to an activation of the phosphoinositol pathways and to calcium accumulation. The activation of the phosphoinositol pathways seems to be a common feature of the different types of arterial hypertension. This activation can be associated with an increase in vasoactive peptides such as angiotensin II, vasopressin, or endothelin as in the secondary types of hypertension or directly related to an increase in vasoconstriction; or, as an exception, it can be spontaneously active in vivo and in vitro, as in the model of cultured vascular smooth muscle cells of the spontaneously hypertensive rat (SHR). This activation of the phosphoinositol pathways is implied not only in cellular contraction, but also in the changes in protein biosynthesis leading to hypertrophy or even to hyperplasia of the cells and, in a less clear manner, in the increase in collagen release. As for experimental aging, no studies on the activation of phosphoinositol pathways have been performed as yet. For atheroma, it has been found that LDLs activate these second messengers. In tissue, both the intracellular and extracellular calcium fractions increase. In addition to playing a crucial and physiological role in contraction mechanisms and cell proliferation, calcium can have toxic effects if gradually accumulated (aging) or due to the action of vasopressive hormones or increased vascular tone. It thus disturbs the energy balance between consumption and production of the substrate. Accumulation of extracellular calcium can also have a detrimental effect on the arterial structure by making the elastic lamellae more fragile, which can induce an intramedial inflammatory reaction and thus lead to aneurysmal dilatations. Vasodilator drugs such as converting enzyme inhibitors (CEIs) or calcium antagonists, by reducing vasoconstriction and interfering directly with the phosphoinositol pathways (as for CEIs) or the inward flux of calcium (as for calcium antagonists), certainly have a beneficial effect on the pathophysiological modifications of the arterial wall in arterial hypertension, normal aging, and atheroma.

Effect of perindopril on the immune arterial wall remodeling in the rat model of arterial graft rejection

A model of arterial graft arteriosclerosis is described in which arterial wall immune injury was induced by grafting segments of abdominal aorta between two histologically incompatible strains of rats. The effect of hypertension and its treatment with the angiotensin-converting enzyme (ACE) inhibitor perindopril was tested using inbred spontaneously hypertensive rats (SHR) and their normotensive controls (Wistar-Kyoto [WKY]). Each of the grafted hypertensive and normotensive rats was randomly allocated to placebo treatment (10 SHR, 10 WKY) and perindopril treatment (2 mg/kg/day) (10 SHR, 10 WKY). The immune injury and the arterial wall response were quantified morphometrically 2 months after the grafting using specific stains for collagen, elastin, and nuclei. Hypertension was associated with a significant increase in intimal thickness. Treatment with perindopril greatly reduced intimal proliferation, decreasing the intimal thickness and the collagen content within the intimal layer. In contrast, hypertension and ACE inhibition had little effect on the arterial wall injury. We conclude that hypertension and its treatment with perindopril significantly affect graft arteriosclerosis. These effects seem to be independent of their effects on arterial wall injury, but not independent of blood pressure.

Additive and synergistic effects of a low-molecular-weight, heparin-like molecule and low doses of cyclosporin in preventing arterial graft rejection in rats.

Arteriosclerotic intimal proliferation is one of the main long-term complications of organ transplantation. Low-molecular-weight, heparin-like molecules prevent myointimal proliferation in arterial wall injury and limit rejection in skin allografts. Cyclosporin limits rejection but has no major effect on intimal proliferation. Therefore, an experimental protocol was designed to test whether heparin-like molecules interacted with low doses of cyclosporin to prevent arterial wall immune system injury and response in a model of arterial graft rejection in normotensive and hypertensive rats. Aortic allografts were performed in spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) normotensive control rats. Four groups of 10 allografted (SHR and WKY) rats were used: one group was treated with placebo, one with low doses of cyclosporin (2 mg/kg body wt per day), one with low-molecular-weight, heparin-like molecule (1 mg/kg body wt per hour), and one with low doses of cyclosporin plus low-molecular-weight, heparin-like molecule. Ten SHRs and 10 WKYs were isografted and served as the control groups. All rats were killed 8 weeks after aortic grafting. Structural parameters of the grafted segment were measured by morphometric analysis on formalin-fixed sections with specific stains. The classical signs of immune system injury and response were present in the untreated allografts in SHRs and WKYs: inflammatory infiltration of the adventitia, medial injury, and intimal proliferative response. Low doses of cyclosporin had a significant beneficial effect on immune medial injury by increasing medial thickness and the number of remaining smooth muscle cells and decreasing the extracellular matrix injury. Cyclosporin had no protective effect on intimal proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative Factors Affecting Renal Outcome After Open Repair of Suprarenal Aortic Aneurysms

BACKGROUNDnThe open repair of suprarenal aortic aneurysm requires supraceliac aortic cross-clamping and separate renal artery reconstruction. The aim of this study was to determine the intraoperative factors responsible for postoperative renal dysfunction.nnnMETHODSnBetween January 1, 2000 and May 31, 2010, 54 suprarenal aortic aneurysms were repaired at our center (mean age of the patients, 66 ± 8 years). All cases were operated through a left retroperitoneal approach without left renal vein division. Acute kidney injury was defined as a 50% increase of serum creatinine level from the preoperative baseline concentration. Perioperative variables were tested to be correlated with renal dysfunction (Spearman rank).nnnRESULTSnThe ischemic time was 28 ± 8 minutes for the mesentery and the right kidney and 63 ± 16 minutes for the left kidney. The total aortic clamping time was 115 ± 27 minutes. The volume of autologous transfusion was 957 ± 479 mL, allogeneic transfusion was 936 ± 473 mL, and colloids and crystalloids was 7,194 ± 2,201 mL. Two patients died. Acute kidney injury occurred in 15 patients, with complete recovery at discharge. The autologous blood transfusion volume (P = 0.009, r = 0.36) and the total aortic clamping time (P = 0.04, r = 0.30) were correlated with renal dysfunction.nnnCONCLUSIONnPostoperative renal dysfunction based on the variation in creatinine serum level was transient and requires further investigation using sensitive biomarkers for tubular ischemia.

Syngeneic Bone Marrow Cell Therapy Prevents Intimal Proliferation in Allogeneic Vascular Transplantation

BACKGROUNDnTransplant arteriosclerosis is characterized by intraluminal obstructive proliferation occurring in response to immune-mediated arterial wall injury. Cell therapy with vascular progenitor cells have been suggested to repair intimal lesions following endothelial injury. The aim of the current study was to assess the effects of autologous bone marrow cell direct transfer and of Fucan-mobilization bone marrow-derived progenitor cells on intimal thickening in vascular grafts.nnnMETHODSnAortic allografts were performed in Brown Norway (BN) and Lewis (LEW) rats. Cell therapy was performed by injection of two doses of 10 million LEW bone marrow mononuclear cells to recipient LEW following aortic grafting. Fucan, a low molecular weight sulfated polysaccharide (LMWF) was used to mobilize bone marrow-derived progenitor cells. Five groups of 10 rats included: untreated isografts (BN to BN), untreated allografts, and three allografted groups, respectively, treated by fucan therapy, cell therapy, or cell and fucan therapy. Aorta were studied by morphometric analysis at 30 d.nnnRESULTSnIn the absence of treatment, intimal thickening was greater in allograft than in isograft groups (299±50 versus 3.5±1.7 μm, P<0.001). Cell therapy alone, fucan therapy alone, and the combined treatment were shown to prevent intimal thickening in allografts (5.1±1.7, 6.1±2.3, 4.1±2.5, versus 299±50 μm respectively, P<0.001). In the three treated groups, the intimal lining was a single layer of endothelial cells expressing CD34 positive, endothelial nitric oxide synthase (eNOS) positive, and Ox3 specific-recipient monoclonal antibody positive.nnnCONCLUSIONnThese results provide the proof of concept of recipient syngenic bone-marrow cell therapy for the prevention of chronic vasculopathy.

A kinetic study of SDF-1, VEGF and MCP-1 blood and tissue levels after aortic transplantation in mice

Vascular rejection is characterized by intimal proliferation and perivascular inflammation. We hypothesize that recipient stem cell therapy could prevent or ameliorate the development of the obliterative lesion. We studied the kinetic expression of three cytokines (SDF-1, MCP-1, VEGF) implicated in mobilization, homing and differentiation of progenitor cells during vascular aggression. An aortic allograft mouse model was used (BALBc donor-C57BL6/j recipient). Ten mice were sacrificed at Day 0, D1, D3, D6, D9, D12, and D20. Cytokine rates were measured in blood and in graft tissue by an ELISA technique. Results showed that in the allograft, SDF-1 and VEGF tissue levels were significantly increased at D12 as compared to the isograft (SDF-1: 22.16 ng/mg vs. 5.69 ng/mg, t=3.38; VEGF: 28.3 pg/mg vs. 9.3 pg/mg, t=3.06). In allografted and isografted groups, MCP-1 tissue levels were higher at D0 as compared to the other time points, without any difference between the two groups. These results prompt us to consider cell therapy at D0 and D12 in this mouse model of aortic graft.

A015 Étude de la cinétique de SDF1, VEGF et MCP1 dans le rejet vasculaire : modèle de greffe aortique chez la souris

Objectif Le rejet vasculaire entraine une ischemie chronique de l’organe transplante. Il se caracterise par un phenomene d’agression — reponse de la paroi arterielle qui aboutit a une obliteration des vaisseaux. L’hypothese de notre travail etait qu’une therapie cellulaire autologue au receveur previendrait la reponse obliterative de la paroi arterielle. L’objectif de ce projet etait de mettre en evidence la cinetique d’expression intra tissulaire de trois cytokines (SDF1, MCP1 et VEGF) ayant un role dans la mobilisation et la captation des cellules progenitrices afin de pouvoir proposer une therapie cellulaire au moment le plus opportun. Materiel et methode 1) Le modele etait une allogreffe aortique (n=35) chez la souris BALBC donneuse / C57BL6 receveuse. Trois souris etaient sacrifiees a J0, J1, J3, J6, J9, J12, J20. A chaque temps, 2 isogreffes (C57BL6 sur C57BL6) etaient realisees. 2) Les concentrations des cytokines SDF-1, VEGF et MCP-1 etaient dosees pour chaque souris sacrifiee par methode ELISA dans le sang d’une part et sur le greffon aortique preleve d’autre part. Resultats Dans le groupe allogreffe, la concentration tissulaire en SDF-1 et en VEGF etait plus importante a J12 qu’aux autres temps (SDF-1: 22,16xa0ng/mg, par exemple txa0=xa02,75 pour J0; VEGF: 28,3xa0pg/mg, par exemple txa0=xa03,27 pour J9). A J12 la concentration tissulaire en SDF-1 et en VEGF etait plus importante en allogreffe qu’en isogreffe. SDF-1 (22,16xa0ng/mg vs 5,69xa0ng/mg, txa0=xa03,38), VEGF (28,3xa0pg/mg vs 9,3xa0pg/mg, txa0=xa03,06) La concentration tissulaire et serique de MCP-1 etait plus importante a J0 qu’aux autres temps en allogreffe (tissulaire 222xa0pg/mg vs 32,7xa0ng/mg a J9, txa0=xa06,24). Il n’y avait pas de difference avec les isogreffes. Conclusion Malgre l’absence de donnee objective sur les mecanismes de production des cytokines, ces resultats etaient en faveur d’une therapie cellulaire centree sur l’expression a J12 de SDF-1, VEGF, plus specifiques que MCP-1.