Rate Of Epithelial Cell Migration Research Articles

The Effect of Using Bone Marrow Mesenchymal Stem Cells Versus Platelet Rich Plasma on the Healing of Induced Oral Ulcer in Albino Rats.

Background and ObjectivesOral ulceration is one of the most common debilitating condition that affects the oral cavity. In this study, the effect of locally injected platelet rich plasma (PRP) and bone marrow-derived mesenchymal stem cells (BMSCs) on the healing of oral ulcer was investigated.Methods and ResultsAn ulcer was induced in buccal mucosa of rats by using 5mm biopsy punch followed by application of cotton swab soaked with formocresol for 60sec. The ulcer was left untreated in the control group, treated with intralesional injection of PRP, or isolated cultured BMSCs. Data were analyzed clinically, histologically and immunohistologically on day 3, 5, 7 and 10. BMSCs group showed smaller ulcer area throughout the whole experimental period than the other groups with complete resolution of the ulcer on day 10, unlike the control group. However, there was no significant difference with PRP, on day 5, 7 and 10, regarding clinical ulcer size. BMSCs group showed better histological results regarding the rate of epithelial cell migration, the number of inflammatory cells, thickness and organization of collagen fibres and the number of blood vessels, with complete re-epithelization on day 10. BMSCs group showed a greater number of anti-PCNA positive nuclei throughout the whole experimental period than the other groups except on day 5, PRP had higher mean numbers of anti-PCNA positive nuclei in both tissues.ConclusionsBoth PRP and BMSCs accelerate wound healing and enhance the quality of the healing tissue with the latter being slightly more effective and faster.

Development and Assessment of a Novel Canine Ex Vivo Corneal Model

ABSTRACTPurpose: To develop a novel ex vivo extended culture model of canine corneal epithelial cell wound healing.Materials and Methods: Canine corneoscleral rims (CSR) were obtained and, after preparation for culture, were placed on a nutating scaffold and incubated in physiological conditions. In experiment 1, eight CSR in a serum-containing antimicrobial-fortified medium were monitored for epithelial integrity and bacterial infection up to 28 days in culture. CSR were assessed histologically at the end of the culture period end points 0, 7, 14, and 28 days with accompanying scanning electron microscopic (SEM) and transmission electron microscopic (TEM) evaluation. Samples for microbial culture were obtained at days 0, 3, 7, 14, and 28. In experiment 2, uniform 8-mm-diameter superficial corneal epithelial wounds were created and monitored for re-epithelialization in the same culture conditions or in a serum-free protein equivalent medium, with four CSR per group. Standardized digital images were obtained with cobalt filter at the time of fluorescein staining and media change every six hours. Image J imaging software was used to measure the area of fluorescein retention. Re-epithelialization rates were calculated and CSR then fixed for immunohistochemistry (IHC).Results: All corneas survived to end points as described in experiment 1 with no evidence of contamination or compromised epithelial integrity. Histologically, a multilayered epithelium was maintained and corneal edema was not appreciated until day 14. SEM examination revealed epithelial cell layer confluence and migrating epithelial cells of normal cellular morphology with normal cell–cell interactions on TEM. In experiment 2, all eight corneas healed with a healing rate of 0.702 ± 0.130 mm2/h (1.25 mm/day epithelial cell migration rate) and were positive in IHC evaluation for markers of corneal fibrosis.Conclusion: This ex vivo canine corneal wound healing model is an appropriate and clinically relevant tool for assessment and modulation of epithelial wound healing.

Glucagon-Like Peptide-2 Requires a Full Complement of Bmi-1 for Its Proliferative Effects in the Murine Small Intestine.

The intestinal hormone, glucagon-like peptide-2 (GLP-2), stimulates growth, survival, and function of the intestinal epithelium through increased crypt cell proliferation, and a long-acting analog has recently been approved to enhance intestinal capacity in patients with short bowel syndrome. The goal of the present study was to determine whether GLP-2-induced crypt cell proliferation requires a full complement of B-cell lymphoma Moloney murine leukemia virus insertion region-1 homolog (Bmi-1), using the Bmi-1(eGFP/+) mouse model in comparison with age- and sex-matched Bmi-1(+/+) littermates. Bmi-1 is a member of the polycomb-repressive complex family that promotes stem cell proliferation and self-renewal and is expressed by both stem cells and transit-amplifying (TA) cells in the crypt. The acute (6 h) and chronic (11 d) proliferative responses to long-acting human (Gly(2))GLP-2 in the crypt TA zone, but not in the active or reserve stem cell zones, were both impaired by Bmi-1 haploinsufficiency. Similarly, GLP-2-induced crypt regeneration after 10-Gy irradiation was reduced in the Bmi-1(eGFP/+) animals. Despite these findings, chronic GLP-2 treatment enhanced overall intestinal growth in the Bmi-1(eGFP/+) mice, as demonstrated by increases in small intestinal weight per body weight and in the length of the crypt-villus axis, in association with decreased apoptosis and an adaptive increase in crypt epithelial cell migration rate. The results of these studies therefore demonstrate that a full complement of Bmi-1 is required for the intestinal proliferative effects of GLP-2 in both the physiological and pathological setting, and mediates, at least in part, the proliferation kinetics of cells in the TA zone.

This Month in Gastroenterology

This Month in Gastroenterology

BALB/c and C57BL6 mouse strains vary in their ability to heal corneal epithelial debridement wounds

Genetically engineered mice are usually produced on a mixed genetic background and can be derived from several mouse strains including 129SvJ, C57BL6, and BALB/c. To determine whether differences in recurrent corneal epithelial erosions (RCEEs), corneal epithelial stem cell deficiency (CESCD), and cell migration rate vary between two different mouse strains (BALB/c and C57BL6), 8-week mice were subjected to 1.5 (small) or 2.8 mm (large) manual debridement wounds and allowed to heal for 4 weeks. Syndecan-1 (sdc-1) null mice backcrossed seven generations onto a BALB/c genetic background were also included in the RCEE and CESCD studies to permit comparisons between genotypes within a single strain. After sacrifice, corneas were assessed for the presence of recurrent erosions; no fewer than 15 corneas were used for each strain or genotype studied. Data show that the frequency of recurrent erosions after small wounds was 81 +/− 9% in the C57BL6 mice, 73 +/− 2% in the BALB/c mice, and 32 +/− 6% in sdc-1 null mice. Neither strain developed CESCD after small wounds. The frequency of erosions after large wounds was greater (88 +/− 8%) in the C57BL6 mice compared to BALB/c (60 +/− 2%), and sdc-1 null mice (32 +/− 5%). Four weeks after the large wounds, fixed, flat mounted corneas were assessed for evidence of CESCD with antibodies against the conjunctival keratin K8 and the goblet cell marker, the mucin Muc5AC. The frequency of CESCD 4 weeks after the large wounds was significantly greater in the C57BL6 mice than in the BALB/c or sdc-1 null mice. To assess cell migration rates, corneas were subjected to 1.5 mm wounds and allowed to heal for 12, 15, 18, 21, and 24 h. After sacrifice, corneas were stained with Richardson stain (BALB/c) or propidium iodide (C57BL6) to assess reepithelialization rates. While reepithelialization rates were similar for the early times after wounding, by 24 h the C57BL6 corneas had healed faster: 16 of 30 corneas from the C57BL6 mice were closed compared to 9 of 30 of the BALB/c wounds. BALB/c corneas appeared larger overall compared to C57BL6 corneas; measurements of the overall mass of the enucleated eyes and diameters of the flat-mounted corneas confirmed that C57BL6 eyes and corneas were 6.8% and 4.4% smaller respectively than those of BALB/c mice even though the masses of the two mouse strains at 8 weeks of age were identical. Using BrdU to label dividing cells, we found that 18 h after wounding, C57BL6 and BALB/c corneal epithelia showed similar numbers of proliferating cells. To determine if the enhanced corneal epithelial cell migration rate seen in the C57BL6 mice was specific to the cornea, we conducted time-lapse studies to assess random cell migration rates in vitro using primary cultures of mouse epidermal keratinocytes. Consistent with the in vivo data, epidermal keratinocytes derived from BALB/c mice migrated 60% slower than C57BL6 cells. These data prove that strain-specific differences in cell migration rate in vivo are present in the cornea and are accompanied by differences in the frequencies of recurrent erosions and corneal epithelial stem cell deficiency.

Feed Withdrawal Alters Small-Intestinal Morphology and Mucus of Broilers

In an effort to reduce carcass contamination and consequent reprocessing, market-age broilers are often subjected to feed withdrawal (FW) before processing to reduce intestinal content and intestinal ruptures during processing. However, little is known regarding the effects of FW on mucus content and intestinal morphology. Therefore, 2 experiments were conducted to determine the effects of FW on intestinal characteristics. Male broilers were raised in floor pens on standard industry diets to 42 and 39 d of age for Experiments (Exp.) 1 and 2, respectively. In Exp. 1, feed was removed 24, 12, 8, and 0 h before sampling, respectively (n = 5 birds/time). Birds remained on litter with access to water for the first 4 h of the FW period and were then placed in crates. Body weights, left pectoralis major weights, and distal ileal and jejunal segments were collected for determination of morphological characteristics. For Exp. 2, birds (n = 8 birds/time) were subjected to 0, 12, and 24 h of FW. Birds were injected with 5-bromo-2′-deoxyuridine and thymidine at 24 and 21 h, respectively, before sampling to determine epithelial cell migration rates. One-centimeter distal ileal segments were collected for mucus quantification at 0, 12, and 24 h. In Exp. 1, ileal villi heights were unaffected by FW, but villus width and crypt depth decreased with increasing FW time (P ≤ 0.05). Jejunal villus height increased as FW progressed. Jejunal crypt depths increased until 12 h of FW and then declined at 24 h. Mucus content decreased linearly and was reduced by 46% from 0 to 24 h FW (P < 0.05). The intestinal morphology alterations and the depletion of intestinal mucus that occur during a short-term FW may reduce the integrity of the intestine.

Increased Apoptosis and Abnormal Wound-Healing Responses in the HeterozygousPax6+/−Mouse Cornea

Corneal wound healing involves a cascade of interactions between the epithelium and stroma. Pax6 is upregulated, and early events include epithelial cell migration and apoptosis of superficial keratocytes. The mouse heterozygous Pax6 (Pax6+/-) corneal phenotype mimics human aniridia-related keratopathy (ARK), and some aspects of wound healing have been shown to be abnormal, including matrix metalloproteinase (MMP)-9 expression. The purpose of this study was to test whether the Pax6+/- genotype affects corneal wound-healing responses, including stromal cell apoptosis, epithelial cell migration rate, and MMP secretion in culture. Pax6+/- and wild-type (Pax6+/+) mice were killed and their corneas wounded by epithelial debridement. Whole eyes were cultured in organ culture and corneal epithelial healing rates and keratocyte apoptosis were quantified by topical fluorescein staining and TUNEL, respectively. Dissociated corneal epithelial cells from Pax6+/- and wild-type mice were cultured, and the activities of secreted MMP-9 were determined by zymography. Wound-healing rates during the first 6 hours were significantly faster for larger wounds and for Pax6+/- corneas. Compared with wild-type, wounded Pax6+/- eyes showed significantly more stromal cell apoptosis, and cultured Pax6+/- corneal epithelial cells produced lower MMP-9 activity. The cumulative effect of abnormal wound-healing responses, characterized by increased stromal cell apoptosis and reduced levels of MMP-9 secretion may contribute to the corneal changes in the Pax6+/- mice. Possible contributions of elevated stromal cell apoptosis and other abnormal wound-healing responses to ARK are discussed.

UTP and diadenosine tetraphosphate accelerate wound healing in the rabbit cornea.

Nucleotides are naturally occurring substances present in tear film that can stimulate tear secretion in animals and humans. We investigated whether certain nucleotides can affect the rate of wound healing in the cornea of white rabbits. In the absence of any added compound, the rate of healing was 72.4 +/- 2.2 microm h(-1). Of all the tested nucleotides, UTP and Ap(4)A were the most active ones, maximally increasing the rate of healing to 121.6 +/- 3.7 and 93.7 +/- 3.2 microm h(-1), respectively. Responses to UTP were dose dependent. UTP had a pD(2) value of 8.9 +/- 0.1 (EC(50): 1.25 nM). P2 purinoceptor antagonists such as suramin and reactive blue-2, inhibited the effect of UTP indicating the involvement of P2Y receptors. Mitogen-activated protein kinase (MAPK) cascade inhibitors also abolished the effects of UTP, suggesting that P2Y receptors are coupled to the MAPK cascade, and that this is involved in controlling the rate of epithelial cell migration.

Targeted inactivation of the mouse guanylin gene results in altered dynamics of colonic epithelial proliferation.

Heat-stable enterotoxin (STa), elaborated by enterotoxigenic Echerichia coli, is a worldwide cause of secretory diarrhea in infants and travelers. Both STa and guanylin, a peptide structurally similar to STa, increase intracellular cGMP levels after binding to the same intestinal receptor, guanylate cyclase C (GC-C). Distinct from its role as an intestinal secretagogue, guanylin may also have a role in intestinal proliferation, as guanylin expression is lost in intestinal adenomas. To determine the function of guanylin in intestinal epithelia, guanylin null mice were generated using a Cre/loxP-based targeting vector. Guanylin null mice grew normally, were fertile and showed no signs of malabsorption. However, the levels of cGMP in colonic mucosa of guanylin null mice were significantly reduced. The colonic epithelial cell migration rate was increased and increased numbers of colonocytes expressing proliferating cell nuclear antigen (PCNA) were present in crypts of guanylin null mice as well. The apoptotic index was similar in guanylin null mice and littermate controls. We conclude from these studies that loss of guanylin results in increased proliferation of colonic epithelia. We speculate that the increase in colonocyte number is related to decreased levels of cGMP and that this increase in proliferation plays a role in susceptibility to intestinal adenoma formation and/or progression.

Foxl1 controls the Wnt/beta-catenin pathway by modulating the expression of proteoglycans in the gut.

Foxl1 is a winged helix transcription factor expressed in the mesenchyme of the gastrointestinal tract. Foxl1 null mice display severe structural defects in the epithelia of the stomach, duodenum, and jejunum. Here we addressed the molecular mechanisms by which Foxl1 controls gastrointestinal differentiation. First we showed that the abnormalities found in the epithelia of the null mice are the result of an increase in the number of proliferating cells and not a change in the rate of cell migration. Next we investigated the regulatory circuits affected by Foxl1. We focused on the Wnt/beta-catenin signaling pathway as a possible target of Foxl1 as it has been shown to play a central role in gastrointestinal proliferation. We demonstrated that Foxl1 activates the Wnt/beta-catenin pathway by increasing extracellular proteoglycans, which act as co-receptors for Wnt. Thus we establish that Foxl1 is involved in the regulation of the Wnt/beta-catenin pathway, providing a novel link in mesenchymal/epithelial cross-talk in the gut. Moreover, we provide the first example implicating proteoglycans in the regulation of cellular proliferation in the gastrointestinal tract.

Epithelial and mast cell products differentially modulate migration of epithelial cells in wounded monolayers

In vivo, mucosal epithelial cells are capable of rapidly resealing an injured epithelial lining by migrating into the denuded area (restitution). Since mucosal injury is associated with epithelial cell destruction and mast cell degranulation, we used an in vitro model of restitution to assess the effects of epithelial and mast cell products on the rate of epithelial cell migration. Confluent monolayers of IEC-18 cells were wounded by scratching with a razor blade and the number of migrating cells entering the denuded area were quantitated. Sonicates of IEC cells stimulated epithelial cell migration. An antibody against epidermal growth factor (EGF) inhibited the promigratory effects of the IEC sonicates. By contrast, RBL (mast cells) sonicates inhibited epithelial cell migration. Protamine sulfate (an heparin antagonist) and heparinase I (a heparin degrading enzyme) reversed the inhibitory effects of the RBL sonicates. Our findings suggest that epithelial cells destroyed during mucosal injury release substances which promote epithelial restitution, most likely, EGF or EGF-like peptides. By contrast, degranulation of mast cells during mucosal injury inhibits epithelial cell migration, an effect most likely attributable to mast cell-derived heparin.

Villus Epithelial Cell Migration is Delayed in Hypothyroid C.RF/hyt Mice • 579

The intestinal epithelium is established and maintained by continuous production of new cells, their migration along the villi and extrusion at the villus tip. In newborn mice replicating and differentiating cells are located throughout the intervillus epithelium, and mature cells slowly traverse the length of the villi. During the suckling period the proliferative epithelium becomes organized and confined to developing crypts. As crypts mature near weaning the replicating cell populations expand, and villus cell migration accelerates eventually reaching rates in adults that are 4-5X greater than in newborns. Glucocorticoid and thyroid hormones mediate changes in digestive enzyme expression during the suckling-weaning transition period, but mechanisms regulating epithelial renewal kinetics during development are not known. Our prior studies show glucocorticoids exert little effect on cell migration and epithelial renewal rates. This study examines thyroid hormone effects on villus epithelial cell migration in C.RF/hyt mice, a strain with primary hypothyroidism, undetectable serum T4 and normal corticosterone production. Proliferating cells were labeled with the thymidine analog, BrdUrd, on day of life 2, 5, 9, 14 or 18, or adults, and migration examined at intervals after labeling using immunohistochemical staining. Migration rates in C.RF/hyt and control euthyroid, Balb/cJ, mice are comparable in the first week of life when endogenous T4 levels are normally low. As T4 rises in the second week, migration rates accelerate rapidly in Balb/cJ mice. In contrast, migration rates in C.RF/hyt mice increase only gradually through weaning and remain delayed in adult animals. In all regions of the small bowel, villus epithelial cell migration rates in adult C.RF/hyt mice reach only 50% of the rates attained in adult euthyroid mice. Correction of hypothyroidism with dietary supplementation adequate to establish fertility and normal serum T4 results in more rapid epithelial cell migration and renewal rates approaching those observed in euthyroid mice. These studies show normal acceleration of villus epithelial cell migration rates during intestinal development are regulated by the physiologic rise in thyroid hormone levels during the suckling period.

VILLUS EPITHELIAL CELL MIGRATION RATE FOLLOWING RADIATION INJURY IS DEVELOPMENTALLY DETERMINED. • 705

The small intestinal epithelium is continuously renewed by proliferation of cells within the crypts, migration of these cells along the villus and their eventual extrusion at the villus tip. Epithelial cell migration and villus epithelial renewal rates are 4-5X slower in newborn than adult mice and increase progressively through the suckling period. To determine if developmental differences in the dynamics of epithelial renewal alter patterns of epithelial injury and repair, we have examined villus morphology and epithelial cell migration rates in newborn and adult mice following radiation injury. Proliferating cells were labeled with the thymidine analog, BrdUrd, either before or after exposure to 12 Gy gamma-irradiation and examined at intervals following injury using immunohistochemical staining. Epithelial cell migration rates at days of life 5, 8, 14 and adult were compared to age-matched, non-irradiated controls. Replicating cell populations in both adults and newborns decrease for the first 2 days after injury followed by regeneration of the proliferative epithelium. In adult mice the villi progressively shorten and are lost by day 4; however, in newborns the villus epithelium is maintained and villi do not shorten throughout injury-repair. Villus epithelial cells labeled before irradiation continue migration along the villus at normal rates in both adults and newborns. In contrast, regenerative epithelial cells produced 3 days after irradiation in adults migrate 40% slower than controls; while in newborn and suckling mice both cell migration and villus epithelial renewal rates accelerate following injury. From these studies we conclude that: (1) patterns of epithelial injury and repair are different in adult and newborn mice following radiation injury, and(2) the accelerated cell migration rates following irradiation may contribute to maintenance of the villi in newborn animals.

Caecal and colonic tissue structure and proliferation as influenced by adaptation period and indigestible polysaccharides

Growing rats were fed experimental diets differing in the type of polysaccharide, for adaptation periods of either 9, 19, 33, 47, or 61 days. The experimental diets contained 8% of either cellulose (CEL), guar gum (GG), pectin (PEC), or resistant starch (RS). A fibre-free diet (FF), containing normal corn starch only, acted as a control diet. Caecal and colonic proliferation activities, in terms of labelling indexes, were significantly higher at the initiation of the experiment (day 0) than observed after the respective adaptation periods. Differences between the adaptation periods were small and inconsistent. Epithelial structure and cellular proliferation depended on the diet and diet effects appeared to be most pronounced in the caecum and least in the distal colon. Epithelial cell migration rates were increased by diet RS and to some extent by diet GG as compared to diet CEL. The more fermentable diets (diets GG and PEC) increased the labelling indexes in the caecum, proximal colon and, to some extent, the distal colon compared to the diet with microbially inert fibre (diet CEL). In the caecum, the increased labelling index was associated with an expansion of the proliferation zones. The expansion of the proliferation zone appeared to take place towards the crypt base rather than towards the crypt mouth. Only small changes in epithelial structure and proliferation were observed after day 9, indicating that adaptation to the experimental diets persisted for as long as the rats received the diets.

Organization of the crypt-villus axis and evolution of its stem cell hierarchy during intestinal development.

The small intestinal crypt of the adult mouse represents a model system for studying cell renewal. One or more functionally equivalent stem cells located within the crypt fuel a continuous regeneration of the gut's four principal epithelial cell lineages. These lineages differentiate during a geographically well-organized migration along the crypt-villus axis. This axis does not complete its morphogenetic program until the third postnatal week. We examined the organization of the crypt-villus axis and its stem cell hierarchy in postnatal day 1 (P1) to P28 transgenic mice. These mice contained transcriptional regulatory elements from the liver fatty acid binding protein gene linked to a human growth hormone (hGH) reporter. Adult male and female animals exhibit a striped pattern of hGH accumulation in their villus-associated epithelial cells: vertical coherent bands of wholly hGH-positive epithelial cells derived from a monoclonal crypt and vertical coherent stripes of wholly hGH-negative epithelial cells derived from an adjacent crypt extend to the apical extrusion zone of their common villus. Villus striping develops in a proximal-to-distal wave that extends from the duodenum to the jejunum by P7 and to the ileum by P14. Striping occurs as a result of a loss in the ability to support transgene expression. The decision appears to affect all cells within a stripe, irrespective of their position along the basilar-to-apical axis of a villus, suggesting that it is programmed by the nascent crypt's multipotent stem cell(s). Suppression of transgene expression traverses the crypt-villus axis more rapidly than the rate of epithelial cell migration. The boundary between stripes is very sharp and does not contain cells with transitional levels of the hGH reporter, indicating that the epithelial components of the crypt-villus axis have a higher degree of organization at this stage of development than appreciated previously.

Effect of dietary copper on intestinal mucosa enzyme activity, morphology, and turnover rates in weanling pigs.

Twenty-four pigs from four litters weaned at 21 d of age (6.6 kg of BW) were used to evaluate the influence of 250 ppm of dietary Cu on intestinal mucosa glucose-6-phosphatase (GP), alkaline phosphatase (AP), and adenosine triphosphatase (ATPase) activity; mucosal morphology; and the turnover rate of the intestinal mucosa throughout the gastrointestinal tract. Pigs were allotted into four pens of six pigs each based on sex, litter, and weight. Pens were then assigned to one of two treatments: 1) corn-soybean meal-whey diet with no antimicrobials (CO), or 2) CO + 250 ppm of Cu. Pigs were fed twice daily an amount approximately equal to ad libitum intake for 14 d. On d 14, pigs were injected i.p. with [3H]thymidine (50 microCi/kg of BW) 10 h after the morning meal. One pig from each pen was euthanatized at 1, 6, 12, 20, 32, and 44 h postinjection, and intestinal tissue was collected from the duodenum, two jejunum sites (upper and lower), ileum, cecum, and colon. The activity of GP and AP in the lower jejunum tended to decrease in pigs fed Cu (P less than .11, P less than .08, respectively). The ATPase activity was not affected by treatment (P greater than .10). Crypt death, villus height, or epithelial cell size (P greater than .10) were not affected by feeding Cu. Migration rate of epithelial cells up the villus was also not affected by treatment (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

The Development of the Gastrointestinal System in Fetal Sheep in the Absence of Ingested Fluid

Our aim was to determine the effects of preventing the passage of ingested fluid on the development of the digestive tract in fetal sheep. The esophagus was fistulated and ligated in six fetuses at 90 days of gestation (term = 145 days); vascular catheters were implanted at day 120. Six control fetuses had vascular catheters implanted at day 120. At autopsy (day 135), although fetal body weights were similar in both groups, the abdominal girth and weights of the gastrointestinal tract, liver, and pancreas were reduced in experimental fetuses. In the gastric (abomasal) fundus and antrum, there was evidence of altered mucus composition in epithelial cells, a decrease in thickness of the muscularis externa, and an increase in thickness of the mucosa and its components. In the duodenum, there were significant changes in the thickness of most components of the wall; Brunner's glands were greatly reduced in size of were absent. Glandular cells contained less mucus in comparison to controls. In the proximal small intestine, there were significant reductions in the thickness of most components of the wall, and epithelial cell migration was retarded, resulting in a longer renewal time for villous cells. In the distal small intestine, the diameter of the intestine and submucosal and epithelial cell migration rate were significantly decreased in the experimental group. In summary, the absence of the passage of ingested fluid in fetal sheep restricts the growth and development of the gastrointestinal tract, liver, and pancreas.

The Development of the Gastrointestinal System in Fetal Sheep in the Absence of Ingested Fluid

SummaryOur aim was to determine the effects of preventing the passage of ingested fluid on the development of the digestive tract in fetal sheep. The esophagus was fistulated and ligated in six fetuses at 90 days of gestation (term = 145 days); vascular catheters were implanted at day 120. Six control fetuses had vascular catheters implanted at day 120. At autopsy (day 135), although fetal body weights were similar in both groups, the abdominal girth and weights of the gastrointestinal tract, liver, and pancreas were reduced in experimental fetuses. In the gastric (abomasal) fundus and antrum, there was evidence of altered mucus composition in epithelial cells, a decrease in thickness of the muscularis externa, and an increase in thickness of the mucosa and its components. In the duodenum, there were significant changes in the thickness of most components of the wall; Brunner's glands were greatly reduced in size or were absent. Glandular cells contained less mucus in comparison to controls. In the proximal small intestine, there were significant reductions in the thickness of most components of the wall, and epithelial cell migration was retarded, resulting in a longer renewal time for villous cells. In the distal small intestine, the diameter of the intestine and submucosal and epithelial cell migration rate were significantly decreased in the experimental group. In summary, the absence of the passage of ingested fluid in fetal sheep restricts the growth and development of the gastrointestinal tract, liver, and pancreas.

Trichostrongylus colubriformis: Epithelial cell migration in the proximal and distal small intestine of infected rabbits

In Trichostrongylus colubriformis-infected rabbits, epithelial cell migration rates and cell transit times along the villi were compared by radioautography on histological slides to normal values from noninfected small intestine. Regions of gut with high (upper jejunum) and low (ileum) burdens of worms were both examined. In the control rabbits, the estimated values for the cell migration rates in the proximal and distal parts of gut were respectively 5.8 and 2.8 μm/hr. Seventy-two hours after the thymidine injection, the labeled epithelial cells were near the tip of the villi in the jejunum whereas only 60% of the villous length was labeled in the ileum. In the infected rabbits, the presence of T. colubriformis was associated with a two-fold increase of the cell velocity, in the main site of infection. Although less prominent than in the proximal region, a significant acceleration in the cell migration was also noticed in the ileum. The cell transit time was markedly reduced in the parasitized jejunum, but no variation of this parameter was found in the distal part of gut. These changes in the dynamics of epithelial cells in both regions of the gut appeared to underlie the morphological and enzymological changes of the parasitized mucosa. They particularly contribute to create an adaptative region in the small intestine beyond the main site of infection.

Effect of urogastrone on intestinal regeneration is dose-dependent.

Urogastrone (UG) increases the rate of intestinal regeneration in intestinal defects patched with adjacent serosal surfaces by increasing the rate of epithelial cell migration and proliferation. It also inhibits contraction of the patched intestinal defect. The purpose of this study was to determine the effect of the dose of UG on these processes. Twenty male New Zealand white rabbits (1.9-2.9 kg) had 2 x 5 cm ileal defects patched with adjacent caecal serosal surface. Group I (n = 6) served as the control group. Group II (n = 5), Group III (n = 5) and Group IV (n = 4) received UG 0.15, 1.5 and 4.5 micrograms/kg/h i.v. via mini-osmotic pumps. Seven days after patching, both epithelialization of the patched defect and neomucosal surface area were significantly increased by UG and the increases were dose-dependent. Contraction was not inhibited by the lowest dose of UG but was diminished by 1.5 micrograms/kg/h. Proliferative activity in both neomucosa and adjacent normal mucosa were increased in UG-treated animals with the greatest increase in rabbits receiving 1.5 and 4.5 micrograms/kg/h UG. The effect of UG on both epithelialization and contraction of patched intestinal defects is dose-dependent. Since the lowest dose of urogastrone increased epithelialization without increasing proliferative activity, stimulated cell migration appears to be the earliest effect of UG.