Robert R. Pascal

Colonic Pericryptal Fibroblast Sheath: Replication, Migration, and Cytodifferentiation of a Mesenchymal Cell System in Adult Tissue: I. Autoradiographic studies of normal rabbit colon

Summary The normal colonic crypt of Lieberkiihn is surrounded by a mesenchymal sheath, a specialized part of the lamina propria, consisting of fibroblasts tightly applied to the epithelium and of collagen fibers oriented circumferentially to the crypt. Autoradiographic studies of rabbit colon after 3 H-thymidine injection demonstrate a steady state renewal of the pericryptal fibroblasts and migration to upper portions of the crypt in synchrony with the epithelial migration. This, to our knowledge, is the first detailed account of continuous fibroblast renewal and migration in adult, un-injured tissue. The fibroblast progenitor population, like that of the epithelium, is at the deep one-third of the crypt, where very little collagen is present. Under the absorptive, i.e., surface, epithelium, there is a relatively thick collagen table, suggesting, a functional maturation of the pericryptal fibroblast as it ascends the crypt wall. These studies, which elucidate the kinetics of a portion of normal colonic mucosa heretofore only occasionally alluded to, suggest that the pericryptal fibroblasts and the epithelium act as a unit to maintain the normal structure, maturation, and function of the crypt of Lieberkuhn.

Comparative Electron Microscopic Features of Normal, Hyperplastic, and Adenomatous Human Colonic Epithelium: Variations in cellular structure relative to the process of epithelial differentiation

Abstract Electron microscopic studies of the epithelium of normal human colonic mucosa, hyperplastic polyps, and adenomatous lesions confirm and extend our previous studies of these tissues. In this study the cytology of well defined examples of the three types of epithelium is compared at several crypt levels. The normal epithelium exhibits a regular pattern of differentiation as cells migrate from the base of the crypt to the free surface. Progressive maturation is seen from undifferentiated cells in the base of the crypt to intermediate and immature goblet and absorptive cells in the midcrypt and, finally, to fully mature and even senescent goblet and absorptive cells in the upper one-third of the crypt and at the free surface. The hyperplastic epithelium exhibits a similar progression, the primary difference being that most of the morphological features of maturing and mature cells are found either lower in the crypt or in exaggerated form at the same level of the crypt when compared with normal mucosa of the same colon. The adenomatous epithelium, however, rarely differentiates past the intermediate, partially differentiated cell stage, retaining both the morphological and replicative characteristics of this immature cell type.

Colonic Pericryptal Fibroblast Sheath: Replication, Migration, and Cytodifferentiation of a Mesenchymal Cell System in Adult Tissue: II. Fine structural aspects of normal rabbit and human colon

Summary The colonic pericryptal fibroblast sheath is a self-renewing population of mesenchymal cells which maintains intimate contact with the base of the epithelium as it and the epithelium. migrate synchronously from their germinative zones to the surface of the crypt. The fine structural appearance of the fibroblast changes during the migration from that of an undifferentiated cell at the lower part of the crypt to that of a mature fibrocyte engaged in protein synthesis at the upper part of the crypt. The change in functional appearance is correlated with the appearance of a wide collagen table under the surface epithelium. The shingling of the fibroblasts creates a complete sheath around the lower portion of each crypt. This cellular sheath is fenestrated under the free surface where only delicate, stellate processes of the fibrocytes maintain close contact with the epithelial basal lamina. The fenestrated appearance of the pericryptal fibrocyte processes in the zone of cellular differentiation, which subtends the fully differentiated absorptive epithelium, may shed some light on the nature of the epithelial basal complex and the role of the pericryptal sheath and the collagen table in fluid transport across colonic mucosa. The constant maintenance of intimate fibroblast-epithelial contact throughout the crypt is additional reason to suppose that a well ordered system of epithelial-mesenchymal interaction is involved in normal structure, renewal, and function of colonic mucosa.

Minute Adenomatous and Hyperplastic Polyps of the Colon: Divergent Patterns of Epithelial Growth with Specific Associated Mesenchymal Changes: Contrasting roles in the pathogenesis of carcinoma

Polypoid lesions of the colon and rectum under 3 mm in diameter were studied by light microscopy in an effort to determine their clinical significance, especially with regard to malignant potential. Examination of the epithelium and the subepithelial connective tissue sheath revealed the majority to be non-neoplastic, i. e., hyperplastic polyps . Less than 10% were true neoplasms, or adenomatous polyps . The former exhibited epithelial and mesenchymal characteristics of extremely differentiated tissue in contrast to the latter, which showed a consistently low level of cytodifferentiation. No transition from hyperplastic to adenomatous mucosa was encountered. The findings reinforce the view that only the adenomatous polyp is of possible significance in colonic carcinogenesis. Statistical analyses and cancer detection programs concerned with the role of polyps in carcinoma formation must recognize the fundamental biological difference between the two types of polyps. The morphological criteria for this distinction are set forth.

The Colonic Pericryptal Fibroblast Sheath: Replication, Migration, and Cytodifferentiation of a Mesenchymal Cell System in Adult Tissue: III. Replication and differentiation in human hyperplastic and adenomatous polyps

Electron microscopic and autoradiographic studies of the pericryptal fibroblast sheath of human hyperplastic and adenomatous colonic polyps confirm the suggestion of Lane et al. (Lane N, Kaplan H, Pascal RR: Minute adenomatous and hyperplastic polyps of the colon: divergent patterns of epithelial growth with specific associated mesenchymal changes. Contrasting roles in the pathogenesis of carcinoma. Gastroenterology 60:537–551, 1971) that these two lesions may represent divergent extremes of the normal differentiation of the colonic mucosa. The sheath of the hyperplastic mucosa is fully differentiated and excessively developed, paralleling precisely the differentiation and development of the overlying epithelium. Conversely, the immaturity of the sheath of the adenomatous epithelium, demonstrated by continued fibroblast division at all levels, failure of morphological maturation of the fibroblasts, and failure of the fibroblasts to secrete their normal extracellular products, collagen and mucopolysaccharides, parallels the degree of immaturity of the overlying adenomatous epithelium. The clinical significance of these findings is discussed.

A Simple Method for Determining Epithelial Cell Turnover in Small Intestine: Studies in Young and Aging Rat Gut

Epithelial cell migration in animal gut classically is measured by autoradiography after systemic administration of tritiated thymidine. A migration rate is calculated from observations of the leading edge of villus epithelial cells containing labeled nuclei at varying time periods after tritiated thymidine injection. This method is very accurate, but laborious, time consuming, and costly. A new, simplified method for measuring epithelial cell measurement of [3H] deoxyribonucleic acid specific activity in frozen sections of intestine cryostat-cut from villus tip to crypt base. The leading edge of [3H]deoxyribonucleic acid can be detected reproducibly (coefficient of variation 11.25%). Autoradiographic and chemical methods for determining the leading edge of labeled cells compared favorable (r=0.848). Epithelial cell migration rates in barrier-reared Fisher 344 aging (27 mo) and young control (4-5 mo) rats were compared and no differences were detected in duodenum, jejunum, or ileum. Labeled epithelial cells reached the villus tip sooner in the ileum than in duodenum or jejunum. However, crypt-villus column heights were greater in duodenum and jejunum and the calculated epithelial cell migration rate was faster in upper intestine than in the ileum. Although ileal epithelial cells are shed from the villus sooner than cells in the upper intestine, the rate of cell migration in ileum is slower.

Adenomatous epithelium, intraepithelial anaplasia, and invasive carcinoma in ulcerative colitis

A retrospective study of 328 biopsy and colectomy specimens from patients with ulcerative colitis revealed the presence of adenomatous lesions and intraepithelial anaplasia with respective frequencies 7 times and 1 1/2 times that of invasive carcinoma in the same series. The patients in whom invasive carcinoma or intraepithelial anaplasia was encountered usually had adenomatous lesions as well. The duration of ulcerative colitis prior to surgery was directly proportional to the severity of the neoplastic change. It is suggested that the origin of some carcinomas in ulcerative colitis is similar to the origin of colorectal cancer in the general population, that is, from adenomatous epithelium.

Adenocarcinoma of the small intestine arising in crohn's disease: Demonstration of a tumor-associated antigen in invasive and intraepithelial components

A segment of small intestine surgically removed from a man with intestinal obstruction was found to have coexisting regional enteritis and an invasive adenocarcinoma associated with an area of intraepithelial neoplasia. The cells of the adenocarcinoma and the intraepithelial neoplasia contained a tumor‐associated surface antigen capable of reacting with an antiserum prepared against a colonic carcinoma. The importance of thorough sampling of specimens of regional enteritis in accurate reporting of the incidence of carcinoma is stressed, as is the use of immunohistologic techniques as an adjunct to the morphologic diagnosis of preinvasive neoplasia.

Pathologic Quiz Case Refractory Hiccups in a Man After Liver Transplantation for Hepatitis C

T patient was a 61-year-old Vietnamese man who had undergone orthotopic liver transplantation on August 12, 1999, for end-stage liver disease secondary to hepatitis C. In the period following the transplantation, the patient experienced no acute cellular rejection. However, increasingly abnormal liver function test results led to a liver biopsy on October 31, 1999, which showed portal triaditis consistent with recurrent hepatitis C infection. The patient’s course was stable until August 2000, when he complained of hiccups for the past week, excessive somnolence for the past 2 months, and a rash on the left side of his back for several days. In addition, he had polydipsia and polyuria in the preceding 2 weeks. The patient’s medical history was remarkable only for the chronic hepatitis C, which lead to his liver transplantation. Current medications included interferon alfa-2b recombinant, ribavirin, famotidine, and tacrolimus. He had no known drug allergies, and his only surgery was the liver transplantation. Results of the physical examination were unremarkable, but his blood glucose level was 696 mg/dL (38.6 mmol/L) (normal, 65–110 mg/dL [3.6–6.1 mmol/L]). He was admitted with diabetic ketoacidosis and was treated with intravenous fluid and insulin. The blood glucose level dropped to 8 mg/dL (0.4 mmol/L)