A method for the direct identification of differentiating muscle cells by a fluorescent mitochondrial dye

Identification of differentiating muscle cells generally requires fixation, antibodies directed against muscle specific proteins, and lengthy staining processes or, alternatively, transfection of muscle specific reporter genes driving GFP expression. In this study, we examined the possibility of using the robust mitochondrial network seen in maturing muscle cells as a marker of cellular differentiation. The mitochondrial fluorescent tracking dye, MitoTracker, which is a cell-permeable, low toxicity, fluorescent dye, allowed us to distinguish and track living differentiating muscle cells visually by epi-fluorescence microscopy. MitoTracker staining provides a robust and simple detection strategy for living differentiating cells in culture without the need for fixation or biochemical processing.

Identification of differentially regulated secretome components during skeletal myogenesis

Myogenesis is a well-characterized program of cellular differentiation that is exquisitely sensitive to the extracellular milieu. Systematic characterization of the myogenic secretome (i.e. the ensemble of secreted proteins) is, therefore, warranted for the identification of novel secretome components that regulate both the pluripotency of these progenitor mesenchymal cells, and also their commitment and passage through the differentiation program. Previously, we have successfully identified 26 secreted proteins in the mouse skeletal muscle cell line C2C12 (1). In an effort to attain a more comprehensive picture of the regulation of myogenesis by its extracellular milieu, quantitative profiling employing stable isotope labeling by amino acids in cell culture was implemented in conjunction with two parallel high throughput online reverse phase liquid chromatography-tandem mass spectrometry systems. In summary, 34 secreted proteins were quantified, 30 of which were shown to be differentially expressed during muscle development. Intriguingly, our analysis has revealed several novel up- and down-regulated secretome components that may have critical biological relevance for both the maintenance of pluripotency and the passage of cells through the differentiation program. In particular, the altered regulation of secretome components, including follistatin-like protein-1, osteoglycin, spondin-2, and cytokine-induced apoptosis inhibitor-1, along with constitutively expressed factors, such as fibulin-2, illustrate dynamic changes in the secretome that take place when differentiation to a specific lineage occurs.

Menin expression modulates mesenchymal cell commitment to the myogenic and osteogenic lineages

Menin plays an established role in the differentiation of mesenchymal cells to the osteogenic lineage. Conversely, whether Menin influences the commitment of mesenschymal cells to the myogenic lineage, despite expression in the developing somite was previously unclear. We observed that Menin is down-regulated in C2C12 and C3H10T1/2 mesenchymal cells when muscle differentiation is induced. Moreover, maintenance of Menin expression by constitutive ectopic expression inhibited muscle cell differentiation. Reduction of Menin expression by siRNA technology results in precocious muscle differentiation and concomitantly attenuates BMP-2 induced osteogenesis. Reduced Menin expression antagonizes BMP-2 and TGF-beta1 mediated inhibition of myogenesis. Furthermore, Menin was found to directly interact with and potentiate the transactivation properties of Smad3 in response to TGF-beta1. Finally in concert with these observations, tissue-specific inactivation of Men1 in Pax3-expressing somite precursor cells leads to a patterning defect of rib formation and increased muscle mass in the intercostal region. These data invoke a pivotal role for Menin in the competence of mesenchymal cells to respond to TGF-beta1 and BMP-2 signals. Thus, by modulating cytokine responsiveness Menin functions to alter the balance of multipotent mesenchymal cell commitment to the osteogenic or myogenic lineages.

Cardiotrophin-1 maintains the undifferentiated state in skeletal myoblasts

Skeletal myogenesis is potently regulated by the extracellular milieu of growth factors and cytokines. We observed that cardiotrophin-1 (CT-1), a member of the interleukin-6 (IL-6) family of cytokines, is a potent regulator of skeletal muscle differentiation. The normal up-regulation of myogenic marker genes, myosin heavy chain (MyHC), myogenic regulatory factors (MRFs), and myocyte enhancer factor 2s (MEF2s) were inhibited by CT-1 treatment. CT-1 also represses myogenin (MyoG) promoter activation. CT-1 activated two signaling pathways: signal transducer and activator of transcription 3 (STAT3), and mitogen-activated protein kinase kinase (MEK), a component of the extracellular signal-regulated MAPK (ERK) pathway. In view of the known connection between CT-1 and STAT3 activation, we surprisingly found that pharmacological blockade of STAT3 activity had no effect on the inhibition of myogenesis by CT-1 suggesting that STAT3 signaling is dispensable for myogenic repression. Conversely, MEK inhibition potently reversed the inhibition of myotube formation and attenuated the repression of MRF transcriptional activity mediated by CT-1. Taken together, these data indicate that CT-1 represses skeletal myogenesis through interference with MRF activity by activation of MEK/ERK signaling. In agreement with these in vitro observations, exogenous systemic expression of CT-1 mediated by adenoviral vector delivery increased the number of myonuclei in normal post-natal mouse skeletal muscle and also delayed skeletal muscle regeneration induced by cardiotoxin injection. The expression pattern of CT-1 in embryonic and post-natal skeletal muscle and in vivo effects of CT-1 on myogenesis implicate CT-1 in the maintenance of the undifferentiated state in muscle progenitor cells.

Protein kinase A-regulated assembly of a MEF2{middle dot}HDAC4 repressor complex controls c-Jun expression in vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs) maintain the ability to modulate their phenotype in response to changing environmental stimuli. This phenotype modulation plays a critical role in the development of most vascular disease states. In these studies, stimulation of cultured vascular smooth muscle cells with platelet-derived growth factor resulted in marked induction of c-jun expression, which was attenuated by protein kinase Cdelta and calcium/calmodulin-dependent protein kinase inhibition. Given that these signaling pathways have been shown to relieve the repressive effects of class II histone deacetylases (HDACs) on myocyte enhancer factor (MEF) 2 proteins, we ectopically expressed HDAC4 and observed repression of c-jun expression. Congruently, suppression of HDAC4 by RNA interference resulted in enhanced c-jun expression. Consistent with these findings, mutation of the MEF2 cis-element in the c-jun promoter resulted in promoter activation during quiescent conditions, suggesting that the MEF2 cis-element functions as a repressor in this context. Furthermore, we demonstrate that protein kinase A attenuates c-Jun expression by promoting the formation of a MEF2.HDAC4 repressor complex by inhibiting salt-inducible kinase 1. Finally, we document a physical interaction between c-Jun and myocardin, and we document that forced expression of c-Jun represses the ability of myocardin to activate smooth muscle gene expression. Thus, MEF2 and HDAC4 act to repress c-Jun expression in quiescent VSMCs, protein kinase A enhances this repression, and platelet-derived growth factor derepresses c-Jun expression through calcium/calmodulin-dependent protein kinases and novel protein kinase Cs. Regulation of this molecular "switch" on the c-jun promoter may thus prove critical for toggling between the activated and quiescent VSMC phenotypes.

Hepatic neuroendocrine metastases: chemo- or bland embolization?

INTRODUCTION

Aggressive management of hepatic neuroendocrine (NE) metastases improves symptoms and prolongs survival. Because of the rarity of these tumors, however, the best method for hepatic artery embolization has not been established. We hypothesized that in patients with hepatic NE metastases, hepatic artery chemoembolization (HACE) would result in better symptom improvement and survival compared to bland embolization (HAE).

METHODS

Retrospective review identified all patients with NE hepatic metastases managed by HACE or HAE at three institutions from January 1996 through December 2007.

RESULTS

We identified 100 patients managed by HACE (n = 49) or HAE (n = 51) that were similar with respect to age, gender, and primary tumor type. The percentage of patients experiencing morbidity, 30-day mortality, and symptom improvement were similar between the two groups (HACE vs. HAE: 2.4% vs. 6.6%; 0.8% vs. 1.8%; and 88% vs. 83%, respectively.) No differences in the median overall survival were observed between HACE and HAE from the time of the first embolization procedure (25.5 vs. 25.7 months, p = 0.79). Multivariate analysis revealed that resection of the primary tumor predicted survival (73.8 vs. 19.4 months, p < 0.04).

CONCLUSIONS

These data suggest that morbidity, mortality, symptom improvement, and overall survival are similar in patients with hepatic neuroendocrine metastases managed by chemo- or bland hepatic artery embolization.

Transforming growth factor-beta and myostatin signaling in skeletal muscle

The superfamily of transforming growth factor-beta (TGF-beta) cytokines has been shown to have profound effects on cellular proliferation, differentiation, and growth. Recently, there have been major advances in our understanding of the signaling pathway(s) conveying TGF-beta signals to the nucleus to ultimately control gene expression. One tissue that is potently influenced by TGF-beta superfamily signaling is skeletal muscle. Skeletal muscle ontogeny and postnatal physiology have proven to be exquisitely sensitive to the TGF-beta superfamily cytokine milieu in various animal systems from mice to humans. Recently, major strides have been made in understanding the role of TGF-beta and its closely related family member, myostatin, in these processes. In this overview, we will review recent advances in our understanding of the TGF-beta and myostatin signaling pathways and, in particular, focus on the implications of this signaling pathway for skeletal muscle development, physiology, and pathology.

Regulation of SOCS-3 expression by leptin and its co-localization with insulin receptor in rat skeletal muscle cells

Obesity is a well-defined risk factor for the development of insulin resistance in target tissues, such as skeletal muscle, and thus type 2 diabetes. This may occur due to endocrine effects mediated by adipokines including leptin, the product of the obese (ob) gene, whose circulating levels positively correlate with body mass index. Induction of suppressor of cytokine-3 (SOCS-3) protein expression has been implicated as a possible mechanism of leptin-induced insulin resistance. Here, we show that treatment of rat skeletal muscle cells with leptin activated the SOCS-3 gene promoter and caused a time-dependent increase in both SOCS-3 mRNA and protein content. Confocal microscopy demonstrated increased co-localization of SOCS-3 with insulin receptor in leptin-treated cells and we confirmed a direct interaction between these two proteins by showing increased coimmunoprecipitation of SOCS-3 and insulin receptor after exposure of cells to leptin. However, the expected functional consequences were not observed, as we saw no change in basal or insulin-stimulated glucose uptake and phosphorylation of GSK3beta, Akt (T308 and S473) or ERK1/2. In summary, leptin induced SOCS-3 expression and its association with the insulin receptor in rat skeletal muscle cells but functional significance of this increase was not apparent upon measuring glucose uptake.

Identification of secreted proteins during skeletal muscle development

The differentiation program of skeletal muscle cells is exquisitely sensitive to secreted proteins. We developed a strategy to maximize the discovery of secreted proteins, using mass spectrometry-based proteomics, from cultured muscle cells, C2C12, grown in a serum-free medium. This strategy led to the identification of 80 nonredundant proteins, of which 27 were secretory proteins that were identified with a minimum of two tryptic peptides. A number of the identified secretory proteins are involved in extracellular matrix remodeling, cellular proliferation, migration, and signaling. A putative network of proteins involving matrix metalloproteinase 2, SPARC, and cystatin C that all interact with TGFbeta signaling has been postulated to contribute toward a functional role in the myogenic differentiation program.

Metastatic neuroendocrine hepatic tumors: resection improves survival

BACKGROUND

The optimal treatment for hepatic metastases from neuroendocrine tumors remains controversial because of the often indolent nature of these tumors. We sought to determine the effect of 3 major treatment modalities including medical therapy, hepatic artery embolization, and surgical resection, ablation, or both in patients with liver-only neuroendocrine metastases, with the hypothesis that surgical treatment is associated with improvement in survival.

DESIGN

Retrospective study.

SETTING

Tertiary care center.

PATIENTS

Patients with metastatic liver-only neuroendocrine tumors were identified from hospital records.

INTERVENTIONS

Patients were subdivided into those receiving medical therapy, hepatic artery embolization, or surgical management.

MAIN OUTCOME MEASURES

Effect of treatment on survival and palliation of symptoms was analyzed.

RESULTS

From January 1996 through May 2004, 48 patients with liver-only neuroendocrine metastases were identified (median follow-up, 20 months), including 36 carcinoid and 12 islet cell tumors. Seventeen patients were treated conservatively, which consisted of octreotide (n = 7), observation (n = 6), or systemic chemotherapy (n = 4). Hepatic artery embolization was performed in 18 patients. Thirteen patients underwent surgical therapy, including anatomical liver resection (n = 6), ablation (n = 4), or combined resection and ablation (n = 3). No difference was noted in the percentage of liver involved with tumor between the 3 groups. An association of improved survival was noted in patients treated surgically, with a 3-year survival of 83% for patients treated by surgical resection, compared with 31% in patients treated with medical therapy or embolization (P = .01). No difference in palliation of symptoms was noted among the 3 treatment groups (P = .2).

CONCLUSION

In patients with liver-only neuroendocrine metastases, surgical therapy using resection, ablation, or both is associated with improved survival.

Smad7 promotes and enhances skeletal muscle differentiation

Transforming growth factor beta1 (TGF-beta1) and myostatin signaling, mediated by the same Smad downstream effectors, potently repress skeletal muscle cell differentiation. Smad7 inhibits these cytokine signaling pathways. The role of Smad7 during skeletal muscle cell differentiation was assessed. In these studies, we document that increased expression of Smad7 abrogates myostatin- but not TGF-beta1-mediated repression of myogenesis. Further, constitutive expression of exogenous Smad7 potently enhanced skeletal muscle differentiation and cellular hypertrophy. Conversely, targeting of endogenous Smad7 by small interfering RNA inhibited C2C12 muscle cell differentiation, indicating an essential role for Smad7 during myogenesis. Congruent with a role for Smad7 in myogenesis, we observed that the muscle regulatory factor (MyoD) binds to and transactivates the Smad7 proximal promoter region. Finally, we document that Smad7 directly interacts with MyoD and enhances MyoD transcriptional activity. Thus, Smad7 cooperates with MyoD, creating a positive loop to induce Smad7 expression and to promote MyoD driven myogenesis. Taken together, these data implicate Smad7 as a fundamental regulator of differentiation in skeletal muscle cells.

Regulation of vertebrate myotome development by the p38 MAP kinase-MEF2 signaling pathway

Biochemical and cell culture studies have characterized the myocyte enhancer factor 2 (MEF2) transcriptional regulatory proteins as obligatory partners for the myogenic regulatory factors (MRFs) in the differentiation of myogenic cells in culture. However, the role of MEF2 activation in somitic myogenesis has not been fully characterized. Here, we report a critical interaction between the p38 mitogen-activated protein kinase (p38 MAPK) and MEF2 in the developing somite myotome. We document expression of MEF2A and p38 MAPK proteins in the somite of 9.5 dpc mouse embryos concurrent with Myf 5 protein expression. We also observed that abrogation of p38 MAPK signaling blocks MEF2 activation using a MEF2 transgenic 'sensor' mouse. Inhibition of p38 MAPK signaling concurrently inhibited myogenic differentiation in somite cultures and in embryos in vivo using transplacental injection of a p38 inhibitor (SB203580). Finally, we document that commitment to the myogenic lineage is not appreciably affected by p38 MAPK inhibition since the activation of an early marker of myogenic commitment (Myf 5) occurs normally when p38 MAPK signaling is inhibited. Thus, we present novel evidence indicating a crucial role for p38 MAPK signaling to the MEF2 transcriptional regulators during early mammalian somite development and myotome formation.

Multiple reaction monitoring as a method for identifying protein posttranslational modifications

The activity of many transcriptional regulators is significantly altered by posttranslational modifications of specific sites. For example, the activity of the muscle-restricted transcription factor family myocyte enhancer factor 2 (MEF2) is tightly controlled by phosphorylation. This modification is responsible for either an increase or a decrease in transcriptional activity, depending on the specific amino acid residues that are phosphorylated by signal-dependent kinases. Although mass spectrometry-based methods, such as precursor ion and neutral loss scans, are extremely useful for identifying unknown phosphopeptides from a complex mixture, they do not take advantage of any prior knowledge about the protein being investigated. Quite often a significant amount of information is available. This may include the primary sequence, type of phosphorylation (serine/threonine vs. tyrosine), or predicted phosphoacceptor sites (consensus peptide that is targeted by a kinase). This information can be used to predict precursor and fragment ion m/z values for a multiple reaction monitoring (MRM) experiment. By using these highly sensitive MRM experiments to trigger dependent product ion scans on a hybrid quadrupole linear ion-trap instrument, we were able to identify low levels of phosphorylation of MEF2A (a member of the MEF2 family), and alpha-casein. This method of monitoring protein phosphorylation at specific phosphoacceptor sites may prove useful in understanding the physiological regulation of protein function.

Phosphorylation motifs regulating the stability and function of myocyte enhancer factor 2A

The phosphorylation status of the myocyte enhancer factor 2 (MEF2) transcriptional regulator is a critical determinant of its tissue-specific functions. However, due to the complexity of its phosphorylation pattern in vivo, a systematic inventory of MEF2A phosphorylation sites in mammalian cells has been difficult to obtain. We employed modern affinity purification techniques, combined with mass spectrometry, to identify several novel MEF2 phosphoacceptor sites. These include an evolutionarily conserved KSP motif, which we show is important in regulating the stability and function of MEF2A. Also, an indirect pathway in which a protein kinase casein kinase 2 phosphoacceptor site is phosphorylated by activation of p38 MAPK signaling was documented. Together, these findings identify several novel aspects of MEF2 regulation that may prove important in the control of gene expression in neuronal and muscle cells.

Composition and function of AP-1 transcription complexes during muscle cell differentiation

The role of activating protein-1 (AP-1) in muscle cells is currently equivocal. While some studies propose that AP-1 is inhibitory for myogenesis, others implicate a positive role in this process. We tested whether this variation may be due to different properties of the AP-1 subunit composition in differentiating cells. Using Western analysis we show that c-Jun, Fra-2, and JunD are expressed throughout the time course of differentiation. Phosphatase assays indicate that JunD and Fra-2 are phosphorylated in muscle cells and that at least two isoforms of each are expressed in muscle cells. Electrophoretic mobility shift assays combined with antibody supershifts indicate the appearance of Fra-2 as a major component of the AP-1 DNA binding complex in differentiating cells. In this context it appears that Fra-2 heterodimerizes with c-Jun and JunD. Studying the c-jun enhancer in reporter gene assays we observed that the muscle transcription factors MEF2A and MyoD can contribute to robust transcriptional activation of the c-jun enhancer. In differentiating muscle cells mutation of the MEF2 site reduces transactivation of the c-jun enhancer and MEF2A is the predominant MEF2 isoform binding to this cis element. Transcriptional activation of an AP-1 site containing reporter gene (TRE-Luc) is enhanced under differentiation conditions compared with growth conditions in C2C12 muscle cells. Further studies indicate that Fra-2 containing AP-1 complexes can transactivate the MyoD enhancer/promoter. Thus, an AP-1 complex containing Fra-2 and c-Jun or JunD is consistent with muscle differentiation, indicating that AP-1 function during myogenesis is dependent on its subunit composition.

Sequencing of argentinated peptides by means of matrix-assisted laser desorption/ionization tandem mass spectrometry

Argentinated peptide ions are formed in abundance under matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) conditions in the presence of Ag+ ions. These argentinated peptide ions are fragmented facilely under MALDI-MS/MS conditions to yield [b(n) + OH + Ag]+, [b(n) - H + Ag]+ and [a(n) - H + Ag]+ ions that are indicative of the C-terminal sequence. These observations parallel those made earlier under electrospray MS conditions (Chu, I. K; Guo, X.; Lau, T.-C.; Siu, K W. M. Anal. Chem. 1999, 71, 2364-2372). A mixed protonated and argentinated tryptic peptide map was generated from 37 fmol of bovine serum albumin (BSA) using MALDI-MS. MALDI-MS/MS data from four argentinated peptides at a protein amount of 350 fmol unambiguously identified the protein as BSA. Sequence-tag analysis of two argentinated tryptic peptides was used to identify unambiguously myocyte enhancer factor 2A, which had been recombinantly expressed in a bacterial cell line.

Effect of MR angiography on the diagnosis and treatment of patients with suspected renovascular disease

PURPOSE

Although the diagnostic accuracy of renal magnetic resonance (MR) angiography is established, its effect on referring physicians is unknown. The authors prospectively measured the effect of MR angiography results on referring physicians' diagnosis and treatment (plans) of patients with suspected renovascular disease.

MATERIALS AND METHODS

Referring physicians prospectively completed questionnaires before and after MR angiography was performed during evaluation of their patients with suspected renovascular disease. The questionnaires asked them to estimate the probability (0%-100%) of their most likely diagnosis before and after receiving the imaging information. They were also asked for their anticipated and final treatment plans. The authors calculated the mean gain in diagnostic percentage confidence and the proportion of patients with changed initial diagnoses or anticipated management. A paired t-test was used to assess significance of the gains in diagnostic percentage confidence.

RESULTS

Physicians prospectively completed pre- and post-MR-angiography questionnaires for 30 patients. MR angiography improved mean diagnostic certainty by 35% (P < .0001). MR angiography changed physicians' initial diagnoses in 12 patients (40%). Anticipated treatment plans were changed in 20 patients (67%). Invasive procedures were avoided in eight patients (27%).

CONCLUSION

MR angiography has a substantial effect on the diagnostic and therapeutic decision-making of physicians managing patients with suspected renovascular disease.

Smad proteins function as co-modulators for MEF2 transcriptional regulatory proteins

An emerging theme in transforming growth factor-ss (TGF-ss) signalling is the association of the Smad proteins with diverse groups of transcriptional regulatory proteins. Several Smad cofactors have been identified to date but the diversity of TGF-ss effects on gene transcription suggests that interactions with other co-regulators must occur. In these studies we addressed the possible interaction of Smad proteins with the myocyte enhancer-binding factor 2 (MEF2) transcriptional regulators. Our studies indicate that Smad2 and 4 (Smad2/4) complexes cooperate with MEF2 regulatory proteins in a GAL4-based one-hybrid reporter gene assay. We have also observed in vivo interactions between Smad2 and MEF2A using co-immunoprecipitation assays. This interaction is confirmed by glutathione S:-transferase pull-down analysis. Immunofluorescence studies in C2C12 myotubes show that Smad2 and MEF2A co-localise in the nucleus of multinuclear myotubes during differentiation. Interestingly, phospho-acceptor site mutations of MEF2 that render it unresponsive to p38 MAP kinase signalling abrogate the cooperativity with the Smads suggesting that p38 MAP Kinase-catalysed phosphorylation of MEF2 is a prerequisite for the Smad-MEF2 interaction. Thus, the association between Smad2 and MEF2A may subserve a physical link between TGF-ss signalling and a diverse array of genes controlled by the MEF2 cis element.

Ureteral injury during laparoscopy-assisted anterior lumbar fusion

STUDY DESIGN

A case report of ureteral injury as a complication incurred during a laparoscopy-assisted lumbar fusion.

OBJECTIVE

To alert orthopedic surgeons to this injury, which may occur during such surgery.

SUMMARY OF BACKGROUND DATA

Laparoscopy-assisted lumbar fusion is a minimally invasive surgical technique to accomplish lumbar fusion with excellent patient satisfaction, reduced hospital stay, and decreased rehabilitative time.

METHOD AND RESULTS

A case report is presented detailing ureteral injury as a complication of laparoscopy-assisted lumbar fusion and the subsequent treatment of the injury.

CONCLUSION

Laparoscopy-assisted lumbar fusion is a new, less invasive technique with excellent patient satisfaction; however, ureteral injury may occur, and the surgeon should keep this in mind if a postoperative fluid collection occurs in the pelvis.

Cell signaling and the regulation of muscle-specific gene expression by myocyte enhancer-binding factor 2

Skeletal muscle is an extremely adaptable tissue. Underlying the biochemical adaptation invoked by changes in activity or during development are dramatic alterations in gene expression. Recent advances in our understanding of the molecular machinery that regulates gene expression in muscle is allowing insight into the pathways that control muscle growth and differentiation. We review developments concerning how cellular signaling pathways induce genetic reprogramming in skeletal muscle.

Peripheral vascular disease and renal transplant artery stenosis: a reappraisal of transplant renovascular disease

BACKGROUND

Renal transplant artery stenosis (RTAS) continues to be a problematic, but potentially correctable, cause of post-transplant hypertension and graft dysfunction. Older transplant recipients, prone to peripheral vascular disease (PVD), may have pseudoRTAS with PVD involving their iliac system.

METHODS

We retrospectively analyzed 819 patients who underwent kidney transplantation between 1993 and 1997 to determine the contribution of pseudoRTAS to renal transplant renovascular disease. Univariate analyses were performed for donor and recipient variables, including age, weight, gender, race, renal disease, cholesterol and creatinine values, human leukocyte antigen (HLA) matching, cytomegalovirus (CMV) infection, and immunosuppressive medications. Significant variables were then analyzed by a Cox proportional hazards model.

RESULTS

Ninety-two patients (11.2%) underwent renal transplant arteriogram (Agram) or magnetic resonance angiography (MRA) for suspected RTAS. RTAS or pseudoRTAS, defined as one or more hemodynamically significant lesions in the transplant artery or iliac system, was evident in 44 patients (5.4%). Variables significantly associated with RTAS by univariate analysis were weight at the time of transplant (p = 0.0258), male gender (p = 0.034), discharge serum creatinine > 2 mg/dL (p = 0.0041), and donor age (p = 0.0062). Variables significantly associated with pseudoRTAS by univariate analysis were weight at the time of transplant (p = 0.0285), recipient age (p = 0.0049), insulin-dependent diabetes mellitus (IDDM; p = 0.0042), panel reactive antibody (PRA) at transplant (p = 0.018), and body mass index (p = 0.04). Weight at transplant and donor age remained significantly associated with an increased risk for RTAS in a multivariate stepwise Cox proportional hazards model. IDDM, transplant PRA, weight at transplant, and donor age were significantly associated with an increased risk for pseudoRTAS in a multivariate stepwise Cox proportional hazards model. Importantly, both RTAS and pseudoRTAS were associated with poorer graft survival (p < 0.007 for each).

CONCLUSIONS

Renal transplant renovascular disease encompasses pre-existing PVD acting as pseudoRTAS, as well as classical RTAS. Efforts to identify and correct renal transplant renovascular disease of either nature are important, given its negative impact on graft survival.