John A. Barnard

The cell biology of transforming growth factor β

The TGF beta family of polypeptide growth factors regulates a remarkable diversity of cellular functions, many of which are not directly associated with cell growth. The present review has summarized many of the recent studies that have just begun to conceptually integrate this expanding array of TGF beta functions into the context of a three-dimensional, multicellular organ or tissue, be it normal or diseased. This fascinating research strongly implicates TGF beta as a key modulator of a wide variety of important physiologic and pathophysiologic processes.

Epidermal growth factor-related peptides and their relevance to gastrointestinal pathophysiology

Growth factor biology has been one of the most exciting areas of gastroenterological research in recent years. Although many fundamental questions about growth factors and their relevance to the gastrointestinal tract remain unanswered and unexplored, the available data point to major clinical significance in a large number of gastrointestinal disorders. This report reviews the biology and significance of the epidermal growth factor (EGF) family, with particular emphasis on understanding the integrated function of the family and the relationships between family members in the context of gastrointestinal physiology and pathophysiology.

Recurrent abdominal pain: A potential precursor of irritable bowel syndrome in adolescents and young adults

OBJECTIVES To assess symptoms of irritable bowel syndrome (IBS) in patients with recurrent abdominal pain (RAP) 5 years after their initial evaluation, to identify the relation of IBS symptoms to functional disability and health service use, and to determine the extent to which IBS symptoms are associated with life stress and poor psychosocial adjustment. METHODS Patients with RAP (n = 76) and control subjects (n = 49) completed a telephone interview; measures included the Bowel Disease Questionnaire, the Functional Disability Inventory, the Life Events Questionnaire, the Family Inventory of Life Events, the Center for Epidemiological Studies Depression Scale, the Self-Perception Profile for Adolescents, and the Health Resources Inventory. RESULTS Five years after the initial evaluation, patients with RAP reported significantly more episodes of abdominal pain than did control subjects, as well as significantly higher levels of functional disability, school absence, and clinic visits for abdominal distress. Female patients with RAP were more likely than female control subjects to meet the Manning criteria for IBS. Among patients with RAP, higher levels of IBS symptoms were associated with significantly greater functional disability, more clinic visits, more life stress, higher levels of depression, and lower academic and social competence. CONCLUSION Female patients with a history of RAP may be at increased risk of IBS during adolescence and young adulthood. Among adolescents and young adults with a history of RAP, IBS symptoms are likely to be associated with high levels of disability and health service use.

Localization of transforming growth factor alpha and its receptor in gastric mucosal cells. Implications for a regulatory role in acid secretion and mucosal renewal.

Transforming growth factor alpha (TGF alpha) shares with epidermal growth factor (EGF) structural homology (35%), a common cell-surface membrane receptor (TGF alpha/EGF receptor), and a nearly identical spectrum of biological activity, including inhibition of gastric acid secretion. Herein, we report expression of TGF alpha mRNA in normal gastric mucosa of the adult guinea pig, rat, and dog. TGF alpha mRNA was also detected in matched surgically resected gastric mucosa and adjacent gastric carcinoma from 10 patients, and in gastric mucosa adjacent to a benign ulcer from an additional patient. TGF alpha protein was quantitated by radioimmunoassay and was present in tumor and adjacent mucosa. TGF alpha/EGF receptor mRNA was also detected in gastric mucosa from all species studied. Localization of TGF alpha and TGF alpha/EGF receptor mRNA expression was examined in samples of unfractionated guinea pig gastric mucosa and from chief cell-enriched and parietal cell-enriched fractions. All samples exhibited TGF alpha and TGF alpha/EGF receptor expression. The TGF alpha signal was greatest in the parietal cell fraction (5.8-fold increase), but was also enhanced in the chief cell fraction (1.9-fold increase) relative to the unfractionated gastric mucosa. Like TGF alpha expression, TGF alpha/EGF receptor mRNA expression was most intense in the parietal cell-enriched fraction (7.8-fold increase), but was also increased in the chief cell-enriched fraction (2.7-fold increase) relative to the unfractionated guinea pig gastric mucosa. We conclude that TGF alpha and TGF alpha/EGF receptor genes are expressed in normal adult mammalian gastric mucosa. These findings, when interpreted in light of described actions of TGF alpha and EGF, provide evidence that local production of TGF alpha could play an important role in the regulation of acid secretion and mucosal renewal in the stomach.

Localization of transforming growth factor β isoforms in the normal murine small intestine and colon

BACKGROUND The transforming growth factor beta (TGF-beta) proteins are key regulators of cellular growth and differentiation. Previous studies have shown that TGF-beta 1 is a potent growth inhibitor of cultured jejunal epithelial cells. The reported distribution of TGF-beta 1 messenger RNA (mRNA) expression along the intestinal villus has been controversial. The purpose of the current study is to determine the loci of TGF-beta protein expression in the normal small intestine and colon. METHODS Intestinal localization of TGF-beta isoform mRNA and protein was examined by Northern blot analysis and immunohistochemistry using isoform specific reagents. RESULTS TGF-beta 1, TGF-beta 2, and TGF-beta 3 mRNA were found in homogenates from the intact mouse jejunum and colon. The three isoforms colocalized in these tissues. Expression in the small intestinal epithelium was most prominent in cells located on the villus tip, and no staining was detected in the crypt. Occasional lymphocytes in the lamina propria were immunopositive, and all layers of the muscularis were moderately stained. This pattern was seen in all regions of the small intestine. The surface epithelium of the colon was intensely immunopositive, whereas cells in the glands were only weakly stained. CONCLUSIONS TGF-beta molecules may serve overlapping functions in the intestinal tract, and expression in the epithelium may function to arrest growth of cells emerging from the crypt and induce or maintain the terminally differentiated state.

Histopathology of Ulcerative Colitis in Initial Rectal Biopsy in Children

Definitive histologic diagnosis of ulcerative colitis relies upon mucosal architectural distortion and inflammation in the appropriate clinical setting. Although crypt branching, atrophy, and loss are usually present in first biopsies from adults with ulcerative colitis, it has been our impression that features of chronicity are often lacking in first biopsies from children. To test this hypothesis, initial rectal biopsies and follow-up biopsies and/or colonic resections from 53 children (age 15 months to 17 years) and 38 adults (age 21–76 years) with ulcerative colitis were examined in a blinded fashion for villiform surface, crypt atrophy, branching crypts, lamina propria inflammation, crypt abscesses, cryptitis, and basal plasma cells. Mucosal architecture was classified as normal, focally abnormal, or diffusely abnormal. Medical records were reviewed for confirmatory evidence of ulcerative colitis and for duration of symptoms before biopsy. In 87 of 91 biopsies, the lamina propria contained a mixed inflammatory infiltrate. Crypt abscesses and cryptitis were common in both groups. Initial biopsies from children were less likely to show diffuse architectural abnormalities (17 of 53, 32.1%) compared with biopsies from adults (22 of 38, 57.9% p <0.05). Duration of symptoms before diagnosis was significantly shorter in children (mean 17.5 weeks) compared with adults (mean 54.9 weeks). In summary, initial rectal biopsies from children with ulcerative colitis are less likely to show diagnostic mucosal architectural distortion than biopsies from adults. This difference may be related to a shorter duration of symptoms before biopsy.

Pharmacological inhibition of Ras-transformed epithelial cell growth is linked to down-regulation of epidermal growth factor–related peptides

BACKGROUND & AIMS Posttranslational farnesylation is required for Ras activation. Farnesyl transferase inhibitors (FTIs) selectively block protein farnesylation and reduce the growth of many Ras-transformed cells in vitro and in vivo. Activated Ras transforms rat intestinal epithelial (RIE-1) cells by a mechanism distinct from NIH 3T3 fibroblasts in that an epidermal growth factor receptor (EGFR) autocrine loop contributes significantly to the Ras-transformed RIE-1 phenotype. METHODS The ability of FTIs to block growth of Ras-transformed RIE-1 cells was evaluated, and these results were correlated with decreased EGFR ligand production. RESULTS FTI L744,832 caused a selective, dose-dependent, reversible blockade in proliferation of H-Ras-transformed RIE-1 cells, whereas control cell lines, K-Ras-transformed cells, and activated raf-transfected RIE cells were unaffected. The growth-inhibitory effects of L744,832 correlated with loss of farnesylated H-Ras protein and a marked reduction in transforming growth factor (TGF)-alpha and amphiregulin expression. Inhibition of proliferation of H-Ras RIE-1 cells by L744,832 was overcome by exogenous TGF-alpha, and enhanced growth inhibition was achieved by EGFR blockade in combination with L744,832. + CONCLUSIONS These data suggest that one mechanism by which FTIs inhibit growth of H-Ras-transformed epithelial cells is by reducing Ras-induced EGFR ligand production.

Transforming Growth Factor β in the Control of Epidermal Proliferation

Transforming growth factor beta is a polypeptide growth factor with a multiplicity of diverse biologic effects. Increasingly, data support a role for TGF beta in the autocrine regulation of normal epithelial cell growth (Figure 1). Definition of the normal pathways for growth stimulation and inhibition of epithelial cell growth by autocrine peptides like TGF beta and TGF alpha undoubtedly will increase understanding of normal growth and development, embryogenesis, wound repair, and tumorigenesis.

Early proliferative events following intestinal resection in the rat.

Partial resection of the small intestine results in compensatory proliferation and adaptation in the remaining small intestinal mucosa. The molecular mechanisms governing the proliferative response are not known, nor has the timing of events associated with proliferation been adequately defined, particularly during the period just after resection. We designed experiments to characterize early (within 24 h) proliferative events associated with proximal intestinal resection and sought to determine the cell type that first responds to proliferative stimuli. Twenty-one day old male Sprague-Dawley rats underwent a 70% proximal intestinal resection or transection (control). Poly(A) RNA was isolated from the distal (ileal) remnants. Northern blots showed a marked induction of the immediate early genes zif-268, nup-475, and c-myc 1-3 h following resection, but not following transection. Immunohistochemical analysis of c-myc expression in ileal crypt epithelial cells showed a biphasic induction that was most marked 6 h after resection and less prominent 24 h after resection. Immunostaining with 5-bromodeoxyuridine (5-BrdU) was restricted to ileal crypt nuclei and was maximal 24 h after resection. All these events were observed in the absence of nutrient intake. Taken together, these data show that a potent nutrient-independent stimulus for intestinal epithelial cell proliferation occurs within minutes of partial small intestinal resection and that the first targets of this stimulus are crypt epithelial cells in the residual intestine.

Safety of pediatric percutaneous liver biopsy performed by interventional radiologists.

Objective: National data suggest that pediatric percutaneous liver biopsy is increasingly being performed by interventional radiologists rather than pediatric gastroenterologists. The objective of the present report is to describe the safety and effectiveness of percutaneous liver biopsy performed by interventional radiologists in a large cohort of children and to compare the results with the existing literature on biopsies performed by pediatric gastroenterologists. Patients and Methods: The medical records of 249 children undergoing ultrasound-guided percutaneous liver biopsy by interventional radiologists were reviewed for adverse events and success of obtaining tissue. Two hundred ninety-four biopsies were reviewed. Results: There were no deaths. There were 2 instances of a 2-g or greater drop in hemoglobin following biopsy, neither of which was associated with clinical signs of hemorrhage. A small, asymptomatic pneumothorax quickly resolved without treatment. One patient developed Klebsiella sepsis 48 hours after biopsy. In all but 1 case, an adequate sample size was obtained. This low incidence of adverse events compares favorably with existing published reports of morbidity and mortality following percutaneous liver biopsy performed by pediatric gastroenterologists. Conclusions: Ultrasound-guided percutaneous liver biopsy performed by experienced pediatric interventional radiologists in a childrens hospital setting is as safe and effective as biopsy performed by pediatric gastroenterologists.