Diagnostic accuracy of laxative-free computed tomographic colonography for detection of adenomatous polyps in asymptomatic adults: a prospective evaluation.

BACKGROUND: Colon screening by optical colonoscopy (OC) or computed tomographic colonography (CTC) requires a laxative bowel preparation, which inhibits screening participation. OBJECTIVE: To assess the performance of detecting adenomas 6 mm or larger and patient experience of laxative-free, computer-aided CTC. DESIGN: Prospective test comparison of laxative-free CTC and OC. The CTC included electronic cleansing and computer-aided detection. Optical colonoscopy examinations were initially blinded to CTC results, which were subsequently revealed during colonoscope withdrawal; this method permitted reexamination to resolve discrepant findings. Unblinded OC served as a reference standard. (ClinicalTrials.gov registration number: NCT01200303) SETTING: Multicenter ambulatory imaging and endoscopy centers. PARTICIPANTS: 605 adults aged 50 to 85 years at average to moderate risk for colon cancer. MEASUREMENTS: Per-patient sensitivity and specificity of CTC and first-pass OC for detecting adenomas at thresholds of 10 mm or greater, 8 mm or greater, and 6 mm or greater; per-lesion sensitivity and survey data describing patient experience with preparations and examinations. RESULTS: For adenomas 10 mm or larger, per-patient sensitivity of CTC was 0.91 (95% CI, 0.71 to 0.99) and specificity was 0.85 (CI, 0.82 to 0.88); sensitivity of OC was 0.95 (CI, 0.77 to 1.00) and specificity was 0.89 (CI, 0.86 to 0.91). Sensitivity of CTC was 0.70 (CI, 0.53 to 0.83) for adenomas 8 mm or larger and 0.59 (CI, 0.47 to 0.70) for those 6 mm or larger; sensitivity of OC for adenomas 8 mm or larger was 0.88 (CI, 0.73 to 0.96) and 0.76 (CI, 0.64 to 0.85) for those 6 mm or larger. The specificity of OC at the threshold of 8 mm or larger was 0.91 and at 6 mm or larger was 0.94. Specificity for OC was greater than that for CTC, which was 0.86 at the threshold of 8 mm or larger and 0.88 at 6 mm or larger (P= 0.02). Reported participant experience for comfort and difficulty of examination preparation was better with CTC than OC. LIMITATIONS: There were 3 CTC readers. The survey instrument was not independently validated. CONCLUSION: Computed tomographic colonography was accurate in detecting adenomas 10 mm or larger but less so for smaller lesions. Patient experience was better with laxative-free CTC. These results suggest a possible role for laxative-free CTC as an alternate screening method.

Regulation of chondrocyte differentiation by actin-severing protein adseverin.

The importance of actin organization in controlling the chondrocyte phenotype is well established, but little is known about the cytoskeletal components regulating chondrocyte differentiation. Previously, we have observed up-regulation of an actin-binding gelsolin-like protein in hypertrophic chondrocytes. We have now identified it as adseverin (scinderin). Adseverin is drastically up-regulated during chondrocyte maturation, as shown by Northern blot analysis, in situ hybridization, and real-time RT-PCR. Its expression is positively regulated by PKC and MEK signaling as shown by inhibitory analyses. Over-expression of adseverin in non-hypertrophic chondrocytes causes rearrangement of the actin cytoskeleton, a change in cell morphology, a dramatic (3.5-fold) increase in cell volume, and up-regulation of Indian hedgehog (Ihh) and of collagen type X--all indicative of chondrocyte differentiation. These changes are mediated by ERK1/2 and p38 kinase pathways. Thus, adseverin-induced rearrangements of the actin cytoskeleton may mediate the PKC-dependent activation of p38 and Erk1/2 signaling pathways necessary for chondrocyte hypertrophy, as evidenced by changes in cell morphology, increase in cell size and expression of the chondrocyte maturation markers. These results demonstrate that interdependence of cytoskeletal organization and chondrogenic gene expression is regulated, at least in part, by actin-binding proteins such as adseverin.

Tagging-based, electronically cleansed CT colonography: evaluation of patient comfort and image readability.

PURPOSE: To prospectively compare the homogeneity, adequacy, and patient acceptance of nonionic iodine-based regimens with those of a barium-based regimen for computed tomographic (CT) colonography with electronic subtraction cleansing. MATERIALS AND METHODS: After institutional review board approval and informed consent were obtained, 68 subjects (41 men (60%) men, 27 (40%) women; mean age, 60 years +/- 6 [standard deviation]) with average or moderate risk factors for development of colorectal carcinoma were recruited and placed into three study groups. Group 1 (n = 25) ingested 150-mL aliquots of 2% barium sulfate suspension with meals and snacks for 48 hours prior to imaging, without other diet modification or a cathartic. Group 2 (n = 21) ingested 10-mL aliquots of nonionic iodinated contrast material (iopromide) with a concentration of 300 mg per milliliter with meals and snacks for 2 days before imaging, without diet modification or a cathartic. Group 3 (n = 22) ingested nonionic iodinated contrast material (iohexol) with a concentration of 300 mg per milliliter with meals and snacks for 2 days before imaging and ingested 34 g of magnesium citrate the evening prior to imaging. CT colonography was also performed on 10 control subjects who ingested polyethylene glycol electrolyte solution prior to imaging. Subjective and numerical measures of bowel preparation quality, homogeneity, and patient comfort among the noncathartic and cathartic cohorts were compared with nonparametric analysis of variance, the Fisher exact test, and the F test, as appropriate. The study was HIPAA compliant. RESULTS: Study subjects who received tagging preparations reported significantly improved discomfort scores when compared with those of the control subjects (P < .05, each comparison). There was no significant difference in discomfort scores among groups 1, 2, and 3. For each reader, scores of subtracted image readability were highest for group 3. Dichotomized rates of preparation "success" were also greatest for group 3. CONCLUSION: In this series, the patient discomfort scores were significantly improved with tagging preparations for CT colonography. Nonionic iodinated contrast material in conjunction with a hyperosmotic laxative (magnesium citrate) was associated with the best subjective and numerical indices of readability.

Polyp size at CT colonography after electronic subtraction cleansing in an anthropomorphic colon phantom.

PURPOSE: To evaluate the effect of various bowel contrast material concentrations and subtraction software on size measurements of well-defined polyp lesions in a colon phantom at CT colonography. MATERIALS AND METHODS: Repeated scanning and a precise reference standard required the use of a colon phantom in which 21 polyps were randomly distributed. Two readers who had each reviewed computed tomographic (CT) colonographic images from more than 100 cases evaluated polyp size on images obtained when the phantom was partially filled with varying concentrations of contrast material, scanned by using CT colonography, and subjected to electronic subtraction cleansing. The single largest dimension was recorded for each reader for a randomized series of polyps. These measurements were compared with a reference standard that was based on a combination of the manufacturer's polyp size specifications and the subsequent verification of these sizes by an independent consensus panel. Six weeks after initial observations, readers evaluated images of the phantom scanned without the presence of contrast material. Polyp size estimations for the two readers for each series were compared with the reference standard to obtain a mean absolute measurement error for each reader for each series. Data for each reader were compared by using a nonparametric Kruskal-Wallis analysis of variance test. A pair-wise comparison of the experimental and control series was then performed by using the Dunn post hoc test. RESULTS: Contrast material dilutions resulting in an average attenuation of less than 500 HU resulted in complete subtraction and the absence of streak artifacts. There was no statistically significant difference between the average measurement error for contrast attenuations between 300 and 500 HU when compared with that of control. Streak artifact was noticeable for the highest dilution (mean, 840 HU). No statistically significant differences were observed for series in which cleansing software was used in the absence of bowel contrast material. CONCLUSION: The combination of electronic cleansing and bowel contrast enhancement in the range of 300-500 HU results in no substantial change in readers' estimations of polyp size at CT colonography.

SP3/SP1 transcription activity regulates specific expression of collagen type X in hypertrophic chondrocytes.

Previously, we have shown that two non-canonical specificity protein (SP)-binding sites within the proximal promoter (nucleotide (nt) -139 to +5) of the chicken Col10a1 gene are involved in conferring tissue-specific expression of type X collagen to hypertrophic chondrocytes. In the present study, we examined the role of SP3/SP1 transcription factors in the regulation of the Col10a1 promoter. The SP3/SP1 ratio is higher in hypertrophic versus non-hypertrophic chondrocytes, due to the significant decrease in SP1 in hypertrophic cells detected by real-time PCR and Western blot analyses. Functional analyses by transfection-mediated overexpression of SP1 and SP3 suggest that SP1 inhibits the Col10a1 promoter. This effect is negated by an interaction with SP3 in hypertrophic chondrocytes. Additionally, mutation analysis showed that the 40-bp intervening sequence (nt -115 to -75) is required for expression of the Col10a1 gene. In this sequence, a binding site for Dlx5/6 transcription factors (nt -99 to -87) retards a protein specific for hypertrophic chondrocytes in electrophoretic mobility shift assay. Endogenous levels of Dlx5 are 3-fold higher in hypertrophic versus non-hypertrophic cells by real-time PCR analysis, and overexpression of Dlx5 in non-hypertrophic chondrocytes activates the proximal Col10a1 promoter 3-fold. These results indicate that the SP3/SP1 ratio and Dlx5 are important regulators of the proximal Col10a1 promoter in hypertrophic cartilage and suggest that interactions between SP3 and SP1 regulate expression of different types of collagen during chondrocyte differentiation.

Chondrocyte-derived transglutaminase promotes maturation of preosteoblasts in periosteal bone.

During endochondral development, elongation of the bone collar occurs coordinately with growth of the underlying cartilaginous growth plate. Transglutaminases (TGases) are upregulated in hypertrophic chondrocytes, and correlative evidence suggests a relationship between these enzymes and mineralization. To examine whether TGases are involved in regulating mineralization/osteogenesis during bone development, we devised a coculture system in which one cellular component (characterized as preosteoblastic) is derived from the nonmineralized region of the bone, and the other cellular component is hypertrophic chondrocytes. In these cocultures, mineralization is extensive, with the preosteoblasts producing the mineralized matrix, and the chondrocytes regulating this process. Secreted regulators are involved, as conditioned medium from chondrocytes induces mineralization in preosteoblasts, but not vice versa. One factor is TGase. In the cocultures, inhibition of TGase reduces mineralization, and addition of the enzyme enhances it. Exogenous TGase also induces markers of osteoblastic differentiation (i.e., bone sialoprotein and osteocalcin) in the preosteoblasts, suggesting their differentiation into osteoblasts. Two possible signaling pathways may be affected by TGase and result in increased mineralization (i.e., TGF-beta and protein kinase A pathways). Addition of exogenous TGF-beta2 to the cocultures increases mineralization; though, when mineralization is induced by TGase, there is no detectible elevation of TGF-beta, suggesting that these two factors stimulate osteogenesis by different pathways. However, an interrelationship seems to exist between TGase and PKA-dependent signaling. When mineralization of the cocultures is stimulated through the addition of TGase, a concomitant reduction (50%) in PKA activity occurs. Consistent with this observation, addition of an activator of PKA (cyclic AMP) to the cultures inhibits matrix mineralization, while known inhibitors of PKA (H-89 and a peptide inhibitor) cause an increase in mineralization. Thus, at least one mechanism of TGase stimulation probably involves inhibition of the PKA-mediated signaling.

Transglutaminase factor XIIIA in the cartilage of developing avian long bones.

Previously, we showed that mRNA for transglutaminase factor XIIIA (FXIIIA) is up-regulated in the hypertrophic zone of the growth plate of the chicken tibiotarsus, a well-characterized model of long bone development. In the present study, we have studied the distribution of the FXIIIA protein and of transglutaminase enzymatic activity in this growth plate, as well as in the cartilage of the epiphysis, which includes that of the articular surface. By immunohistochemical analysis, the protein is detected in the zone of maturation, where it is mostly intracellular, and in the hypertrophic zone, where it is present both intracellularly and in the extracellular matrix. The intracellular enzyme is mostly a zymogen, as determined with an antibody specific for the activation peptide. Externalization of FXIIIA is accompanied by enzyme activation. To study the pattern of transglutaminase activity, a synthetic transglutaminase substrate, rhodamine-conjugated tetrapeptide (Pro-Val-Lys-Gly), was used for pulse labeling in organ cultures. Intensive incorporation of the fluorescent substrate was observed throughout the hypertrophic zone and in the cells surrounding the forming blood vessels. The patterns of FXIIIA immunostaining and substrate incorporation overlap almost completely. The cartilaginous factor XIIIA is different from the plasma form in that, both intracellularly and extracellularly, it exists as a monomer, as determined by Western analysis, whereas the plasma form of FXIII is a tetrameric complex composed of both A and B subunits. We also identified FXIIIA and transglutaminase activity within the articular and condylar regions of the tarsus, suggesting a possible involvement of mechanical pressure and/or stress in the production of the molecule and subsequent cross-linking of the cartilage matrix. Thus, transglutaminases, in particular FXIIIA, are involved in the formation of long bones through its activity both in the hypertrophic region of the growth plate and in the formation of articular/epiphyseal cartilages.