Parenteral arginine impairs intestinal adaptation following massive small bowel resection in a rat model

The nitric oxide precursor L-arginine (ARG) has been shown to influence intestinal structure and absorptive function. It is also well known that the route of administration modulates the effects of ARG. The present study evaluated the effects of parenteral ARG on structural intestinal adaptation, cell proliferation, and apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and reanastomosis, SBS rats underwent a 75% small bowel resection, and SBS-ARG rats underwent a 75% small bowel resection and were treated with ARG given subcutaneously at a dose of 300 g/kg, once daily, from days 3 to 14. Parameters of intestinal adaptation, enterocyte proliferation, and enterocyte apoptosis were determined on day 15 following operation. The SBS rats demonstrated a significant increase in jejunal and ileal bowel and mucosal weight, villus height and crypt depth, and cell proliferation index compared with the sham group. The SBS-ARG animals demonstrated lower ileal bowel and mucosal weights, jejunal mucosal DNA and ileal mucosal protein, and jejunal and ileal villus height and crypt depth compared with SBS animals. The SBS-ARG rats also had a lower cell proliferation index in both jejunum and ileum and a greater enterocyte apoptotic index in ileum compared with the SBS-untreated group. In conclusion, in a rat model of SBS, parenteral arginine inhibits structural intestinal adaptation. Decreased cell proliferation and increased apoptosis are the main mechanisms responsible for decreased cell mass.     

Effect of subcutaneous insulin on intestinal adaptation in a rat model of short bowel syndrome

Insulin has been shown to influence intestinal structure and absorptive function. The purpose of the present study was to evaluate the effects of parenteral insulin on structural intestinal adaptation, cell proliferation, and apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent bowel transection and reanastomosis, SBS rats underwent a 75% small bowel resection, and SBS-INS rats underwent a 75% small bowel resection and were treated with insulin given subcutaneously at a dose of 1 U/kg, twice daily, from day 3 through day 14. Parameters of intestinal adaptation, enterocyte proliferation, and enterocyte apoptosis were determined on day 15 following operation. SBS rats demonstrated a significant increase in jejunal and ileal bowel and mucosal weight, villus height and crypt depth, and cell proliferation index compared with the sham group. SBS-INS animals demonstrated higher jejunal and ileal bowel and mucosal weights, jejunal and ileal mucosal DNA and protein, and jejunal and ileal crypt depth compared with SBS animals. SBS-INS rats also had a greater cell proliferation index in both jejunum and ileum and a trend toward a decrease in enterocyte apoptotic index in jejunum and ileum compared with the SBS untreated group. In conclusion, parenteral insulin stimulates structural intestinal adaptation in a rat model of SBS. Increased cell proliferation is the main mechanism responsible for increased cell mass.     

Oral arginine improves intestinal recovery following ischemia-reperfusion injury in rat

Arginine and nitric oxide are critical to the normal physiology of the gastrointestinal tract and maintain the mucosal integrity of the intestine in various intestinal disorders. In the present study, we evaluate the effects of oral arginine (ARG) supplementation on intestinal structural changes, enterocyte proliferation, and apoptosis following intestinal ischemia–reperfusion (IR) in the rat. Male Sprague–Dawley rats were divided into three experimental groups: sham rats underwent laparotomy and superior mesenteric artery mobilization, IR rats underwent superior mesenteric artery occlusion for 30 min following by 24 h of reperfusion, and IR-ARG rats were treated with enteral arginine given in drinking water (2%) 48 h before and following IR. Intestinal structural changes, enterocyte proliferation, and enterocyte apoptosis were determined 24 h following IR. A nonparametric Kruskal–Wallis ANOVA test was used for statistical analysis with p <0.05 considered statistically significant. IR rats demonstrated a significant decrease in bowel weight in duodenum and jejunum, mucosal weight in jejunum and ileum, and villus height in jejunum and ileum compared with control animals. IR rats also had a significantly lower cell proliferation index in jejunum and ileum and a higher apoptotic index in ileum compared with control rats. IR-ARG animals demonstrated greater duodenal and jejunal bowel weight; duodenal, jejunal, and ileal mucosal weight; and jejunal and ileal cell proliferation index compared with IR animals. In conclusion, oral ARG administration improves mucosal recovery following IR injury in the rat.     

Mucosal expression of p21, p27, p53, Bcl-2, and bax after small bowel resection and autotransplantation in pigs

Massive small bowel resection increases ileal villus height as part of normal adaptation. However, despite no gut loss, autotransplantation of the entire small intestine also increases ileal villus height. Our aim was to test whether similar modulation of enterocyte proliferation and apoptosis underpin these comparable increases in villus height. Fifteen pigs were randomly assigned for laparotomy (n=5), 75% proximal small bowel resection (n=5), or jejunoileal autotransplantation (n=5). Eight weeks postoperatively, full-thickness small bowel sections underwent routine immunohistochemistry for cell cycle inhibitors (p53, p21, and p27), antiapoptotic Bcl-2, and proapoptotic bax. The specimens were analyzed semiquantitatively, and the number of intensively positive epithelial cells for each group was compared from 20 digital images (0.32 mm²/image). Compared with laparotomy, small bowel resection decreased the number of p27-positive enterocytes in both jejunum and ileum, increased the number of bax-expressing cells in ileum, but decreased the number of bax-expressing cells in jejunum. In contrast, compared with laparotomy, jejunoileal autotransplantation altered neither mucosal bax nor p27 expression. In all groups, Bcl-2 expression was similarly confined to inflammatory cells of the lamina propria, while both p53 and p21 were negative. We conclude that long-term alterations in the enterocytic expression of certain cell cycle and apoptosis markers (p27 and bax) accompany small bowel resection. These changes differ between the jejunum and the ileum and are not seen after whole small bowel autotransplantation. Therefore, increased ileal villus height after autotransplantation, despite resembling postresectional intestinal adaptation, is underpinned by different regulation of enterocyte proliferation and apoptosis.     

Lipopolysaccharide endotoxemia reduces cell proliferation and decreases enterocyte apopotosis during intestinal adaptation in a rat model of short-bowel syndrome

Sepsis is frequently associated with or complicates short-bowel syndrome (SBS). To investigate the effects of lipopolysaccharide (LPS) endotoxemia on enterocyte proliferation and death via apoptosis in a rat model of SBS, adult male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent bowel transection and reanastomosis; SBS rats underwent 75% small-bowel resection; and SBS-LPS rats underwent 75% bowel resection and were given intraperitoneal injections of LPS 10 mg/kg. Parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height, and crypt depth), enterocyte proliferation, and death via apoptosis were determined on day 15 after the operation. Statistical analysis was determined by Student's and ANOVA tests with a P less than 0.05 considered significant. SBS-LPS animals demonstrated a significant decrease (vs SBS rats) in duodenal (20%), jejunal (30%), and ileal (15%) overall weight, duodenal (20%), jejunal (27%), and ileal (18%) mucosal weight, jejunal (20%) and ileal (30%) mucosal DNA, jejunal (29%) and ileal (31%) villus height, and jejunal (14%) and ileal (29%) crypt depth. LPS endotoxemia led to reduced cell proliferation and enterocyte apoptosis compared to untreated SBS animals. Thus, in a rat model of SBS, LPS endotoxemia inhibits intestinal adaptation. A possible mechanism may be decreased cell proliferation. Decreased enterocyte loss via apoptosis may reflect a reduced number of enterocytes. Other mechanisms (necrosis) may be mainly responsible for cell death following LPS injection.     

The effect of leptin on intestinal recovery following ischemia-reperfusion injury in a rat

Recent evidence suggests that the adipose tissue derived cytokine leptin (LEP) is involved in the modulation of growth and differentiation of normal small intestine. The purpose of the present study was to examine the effect of leptin on enterocyte turnover and intestinal recovery after ischemia-reperfusion (IR) injury in a rat. Male Sprague–Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy, (2) IR-rats underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 24 h of reperfusion, and (3) IR-LEP rats underwent IR and were treated with leptin given subcutaneously at a dose of 50 μg/kg once a day for 48 h before and 24 h following IR. Intestinal structural changes, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. A non-parametric Kruskal–Wallis ANOVA test was used for statistical analysis with P < 0.05 considered statistically significant. Treatment with leptin resulted in a significant increase in bowel weight in ileum, mucosal weight in jejunum and ileum, mucosal DNA content in ileum, mucosal protein content in jejunum and ileum, villus height in jejunum and ileum, and crypt depth in jejunum compared to IR-animals. IR-LEP rats also had a significantly lower intestinal injury score as well as lower apoptotic index and higher cell proliferation index in jejunum and ileum compared to the IR-animals. In conclusion, pre-treatment with leptin prevents gut mucosal damage and improves intestinal rehabilitation following intestinal IR in a rat.     

Intestinal epithelial cell proliferation is dependent on the site of massive small bowel resection

Early intestinal adaptation after massive small bowel resection (SBR) is driven by increased epithelial cell (EC) proliferation. There is a clear clinical difference in the post-operative course of patients after the loss of proximal (P) compared to distal (D) small bowel. This study examined the effects of the site of SBR on post-resectional intestinal adaptation, and investigated the potential mechanisms involved. C57BL/6J mice (n = 7/group) underwent: (1) 60% P-SBR, (2) 60% D-SBR, (3) 60% mid (M)-SBR and (4) SHAM-operation (transection/reanastomosis). Mice were sacrificed at 7 days after surgery and ECs and adjacent mucosal lymphocytes (IELs) isolated. Adaptation was assessed in both jejunum and ileum by quantification of villus height, crypt depth, villus cell size, crypt cell size (microns), goblet cell number, and EC proliferation (%BrdU incorporation). Proliferation signalling pathways including keratinocyte growth factor (KGF)/KGFR₁, IL-7/IL-7R, and epidermal growth factor receptor (EGFR) were measured by RT-PCR. Expression of IL-7 was further analysed by immunofluorescence. Data were analyzed using ANOVA. All three SBR models led to significant increases in villus height, crypt depth, goblet cell numbers and EC proliferation rate when compared to respective SHAM groups. The strongest morphometric changes were found for jejunal segments after M-SBR and for ileal segments after P-SBR. Furthermore, morphometric analysis showed that at 1-week post-resection a tremendous increase in EC numbers occurred in jejunal villi (cell hyperplasia), whereas a significant increase in EC size predominated in ileal villi (cell hypertrophy). mRNA expression of KGF, KGFR₁, IL-7R, and EGFR showed a significant increase only after D-SBR, whereas IL-7 increased significantly after SBR in all investigated models, and this was confirmed by immunofluorescence studies. Early intestinal adaptation shows distinct differences depending on the site of SBR, and is predominately driven by cell hyperplasia in jejunal villi and cell hypertrophy in ileal villi. However, the exact mechanisms, which guide these signalling pathways are still unclear.     

Peptide YY induces enterocyte proliferation in a rat model with total enteral nutrition after distal bowel resection

The main reason why enterocyte proliferative effects of peptide YY (PYY) have not been detected in rats undergoing massive small intestinal resection after feeding may have been the background activity of markedly increased endogenous PYY released from L cells in the distal gut in response to the intraluminal nutrients. The purpose of the present study was to evaluate the effects of PYY on enterocyte proliferation in a rat model of distal bowel resection (DBR) with total enteral nutrition (TEN). Male, adult Sprague–Dawley rats were assigned into three experimental groups: sham rats underwent bowel transection and reanastomosis, DBR rats underwent the resection of 40 cm distal small intestine and colon, and DBR–PYY rats underwent distal bowel resection as above, and were treated with PYY_1–36 from day 2 to day 14 postoperatively. During days 2–14 postoperatively, all animals received isocaloric TEN. At the endpoints, plasma PYY levels and parameters of enterocyte proliferation were determined. Compared with the sham group, DBR rats demonstrated a significant decrease in plasma PYY levels, and a significant increase in intestinal bowel and mucosal weight, mucosal DNA and protein content, villus height and crypt depth, and crypt cell proliferation index. Administration of PYY (DBR-PYY group) led to a significant increase in plasma PYY levels, intestinal bowel and mucosal weight, mucosal DNA and protein content, villus height and crypt depth, and crypt cell proliferation index in comparison with the DBR untreated group. We conclude that administration of PYY increases the plasma PYY levels, and PYY induces enterocyte proliferation with TEN after distal bowel resection.     

Oral insulin stimulates intestinal epithelial cell turnover in correlation with insulin-receptor expression along the villus–crypt axis in a rat model of short bowel syndrome

Purpose

It has been reported that oral insulin (OI) has a trophic effect on intestinal mucosa. In the present study, we evaluated the effect of OI on enterocyte turnover and correlated it with insulin-receptor expression along the villus–crypt axis in a rat model of short bowel syndrome (SBS).

Methods

Male rats were divided into three groups: Sham rats underwent bowel transection, SBS rats underwent a 75% bowel resection, and SBS–OI rats underwent bowel resection and were treated with OI given in drinking water (1 U/ml) from the fourth postoperative day. Parameters of intestinal adaptation, enterocyte proliferation and apoptosis were determined on day 15. Real-time PCR was used to determine the level of insulin receptor-beta (IRB) mRNA. Insulin-receptor expression along the villus–crypt axis (villus tips, lateral villi and crypts) was assessed by immunohistochemistry. The effect of OI on cell turnover for each compartment was evaluated in correlation with the receptor expression. Statistical analysis was performed using the one-way ANOVA test, with P < 0.05 considered statistically significant.

Results

Treatment with OI resulted in a significant increase in all parameters of intestinal adaptation. Insulin-receptor expression in crypts significantly increased in SBS rats (vs. Sham rats) and was accompanied by a significant increase in enterocyte proliferation following OI administration. A significant increase in insulin-receptor expression at the tip of the villous and in the lateral villous in SBS rats (vs. Sham) was accompanied by decreased cell apoptosis in these compartments following treatment with OI.

Conclusions

In a rat model of SBS, OI enhances enterocyte turnover and stimulates intestinal adaptation. The stimulating effect of insulin on enterocyte turnover correlates with insulin-receptor expression along the villus–crypt axis.     

Effects of intrinsic denervation on intestinal morphology in rats with short-bowel syndrome

When benzalkonium chloride solution (BACs) is locally applied, to the serosal surface of the intestine, it causes intrinsic denervation (ID) of the myenteric plexus (MP), changes intestinal morphology, and slows intestinal passage by prolonging small-bowel transit time. These effects of ID suggest that chemically-induced bowel denervation may be useful in the treatment of short-bowel syndrome (SBS). How ID affects intestinal morphology in rats with SBS has not previously been investigated. A 75%–80% mid-small-bowel resection was performed in 20 rats with mean body weight 247 ± 30 g. The proximal and distal 2 cm of the resected bowel were examined histologically. After intestinal continuity was maintained by end-to-end anastomosis, a 2-cm jejunal segment was marked with silk sutures to form the test segment. BACs 0.1% was applied to 10 of the 20 test segments according to the modified Fox method, resulting in MP destruction (G1). Saline solution was applied to the other 10 test segments to form the control group (G2). Three months later, the rats were killed and the jejunal, ileal, and test segments were evaluated morphologically. Results were expressed as mean ± standard deviation. The Wilcoxon parametric test was performed to compare the groups during the operation and after death, while the Mann–Whitney U-test was used to compare the data in G1 and G2. No intestinal obstruction was observed in either group. In G1, the body weight increased by 19.1% and the total small-intestinal lengthening was 62.2% (P < 0.05). In the test segment of G1, 75% of the ganglia in the MP were destroyed and villus height, crypt depth, intestinal muscle thickness, number of enterocytes, and villus density increased compared to G2. In the ileal segments of G1, there was an increase of 28.8% in intestinal diameter, 14% in muscle thickness, and 15% in villus density (P < 0.05). No change was observed in the untreated jejunal segments of G1 and G2. Thus, ID of the MP after segmental BACs application of the jejunal level: (1) does not cause intestinal obstruction after 3 months; (2) the increase in bowel diameter in the test and ileal segments increases the absorptive surface of the mucosa; (3) the morphologic changes in the test and ileal segments verify an increase in intestinal adaptation; and (4) BACs application in rats with SBS is an easy procedure with no morbidity or mortality, and can be used to increase intestinal adaptation in rats with SBS. Accepted: 1 February 2000     

Responsiveness of intestinal epithelial cell turnover to TGF-α after bowel resection in a rat is correlated with EGF receptor expression along the villus–crypt axis

Recent evidence suggests that transforming growth factor alpha (TGF-alpha) enhances enterocyte proliferation and stimulates intestinal adaptation after massive bowel resection. In the present study, we evaluated the effects of TGF-alpha on enterocyte turnover and correlated it with epidermal-growth factor (EGF) receptor expression along the villus-crypt axis in a rat model of short bowel syndrome (SBS). Male rats were divided into three groups, sham rats underwent bowel transection (group A); SBS rats underwent a 75% bowel resection (group B); and SBS/TGF-alpha rats underwent bowel resection and were treated with TGF-alpha (75 microg/kg) (group C) from the seventh postoperative day. Parameters of intestinal adaptation, enterocyte proliferation and apoptosis were determined on day 15. Villus tips, lateral villi and crypts were separated using laser capture microdissection. EGF receptor expression for each compartment was assessed by quantitative real-time PCR (Taqman). Statistical analysis was performed using one-way ANOVA test, with P < 0.05 considered statistically significant. Treatment with TGF-alpha resulted in a significant increase in all parameters of intestinal adaptation. EGF receptor expression in crypts significantly increased in SBS rats (vs sham rats) (0.035 +/- 0.013 vs 0.010 +/- 0.002 Log ng Total RNA/18 s) and was accompanied by a significant increase in enterocyte proliferation (169 +/- 8 vs 138 +/- 5 BrdU positive cells/per 10 crypts, P < 0.05) and decreased apoptosis following TGF-alpha administration (group C). A significant decrease in EGF receptor expression at the tip of the villus (0.005 +/- 0.002 vs 0.029 +/- 0.014 Log ng Total RNA/18 s) and in the lateral villus (0.003 +/- 0.001 vs 0.028 +/- 0.006 Log ng Total RNA/18 s) in SBS (group B) rats (vs sham, group A) was accompanied by increased cell apoptosis in these compartments following treatment with TGF-alpha (group C). In a rat model of SBS, TGF-alpha increased enterocyte proliferation and stimulated intestinal adaptation. The effect of TGF-alpha on enterocyte turnover is correlated with EGF receptor expression along the villus-crypt axis.     

Effect of 100% oxygen on E-selectin expression, recruitment of neutrophils and enterocyte apoptosis following intestinal ischemia-reperfusion in a rat

Recent evidence suggests that neutrophil recruitment may initiate cell apoptosis in ischemic tissues. We have recently shown that enterocyte apoptosis is increased following intestinal ischemia-reperfusion (IR) injury. The purpose of the present study was to examine the effect of hyperoxia on E-selectin expression, neutrophil recruitment and enterocyte apoptosis following intestinal IR in a rat. Male Sprague-Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy without vascular occlusion and were ventilated with air (Sham) (2) IR rats underwent occlusion of both the superior mesenteric artery and portal vein for 30 min and were ventilated with air (IR), and (3) IR-O₂ rats underwent IR and were ventilated with 100% started 10 min before reperfusion and continued for 6 h (IR-O₂). Intestinal structural changes were determined 24 h following IR. Immunohistochemistry for E-selectin (using E-selectin cleaved concentrated polyclonal antibody) was performed to identify E-selectin immunoreactivity localized to the endothelium of venules. The recruitment of neutrophils was calculated per 100 venules. Immunohistochemistry for Caspase-3 was performed for identification of apoptotic cells. Non-parametric one-way ANOVA test was used for statistical analysis with p less than 0.05 considered statistically significant. A significant increase in E-selectin expression in the jejunum (6.1 ± 2.2 vs. 2.5 ± 1.0 E-selectin positive vessels/100 vessels, p < 0.05) and ileum (12.1 ± 2.7 vs. 3.3 ± 1.2 E-selectin positive vessels/100 vessels, p < 0.05) and a concomitant increase in neutrophil recruitment in the ileum (5.5 ± 1.6 vs. 1.3 ± 0.6 adhered PMN’s per 100 venules) were observed in IR rats compared to sham animals and were accompanied by increased cell apoptosis (p < 0.05). Treatment with 100% oxygen resulted in a significant attenuation in E-selectin expression in the ileum (2.7 ± 1.1 vs. 12.1 ± 2.7 E-selectin positive vessels/100 vessels, p < 0.05), and neutrophil recruitment in the jejunum (2.5 ± 1.4 vs. 7.7 ± 1.9 adhered PMN’s per 100 venules, p < 0.05) and ileum (1.5 ± 0.7 vs. 5.5 ± 1.6 adhered PMN’s per 100 venules, p < 0.05) compared to IR animals, and was accompanied by decreased cell apoptosis (p < 0.05). Hyperoxia inhibits enterocyte apoptosis following intestinal ischemia-reperfusion. Down-regulation of E-selectin expression with subsequent decrease in neutrophil recruitment may be responsible for this effect.     

Effect of ozone on intestinal recovery following intestinal ischemia–reperfusion injury in a rat

Background

Growing evidence suggests that ozone (O₃) protects the host against pathological conditions mediated by reactive oxygen species by increasing the activity of antioxidant enzymes. The purpose of the present study was to examine the effect of O₃ on intestinal recovery and enterocyte turnover after intestinal ischemia–reperfusion (IR) injury in rats.

Methods

Male Sprague–Dawley rats were divided into four experimental groups: (1) sham rats underwent laparotomy; (2) sham-O₃ rats underwent laparotomy and were treated with an ozone/oxygen mixture intraperitoneally and intraluminally (50 %/50 %); (3) IR rats underwent occlusion of both superior mesenteric artery and portal vein for 20 min followed by 48 h of reperfusion, and (4) IR-O₃ rats underwent IR and were treated with an ozone/oxygen mixture similar to group 2. Intestinal structural changes, Park’s injury score, enterocyte proliferation and enterocyte apoptosis were determined 48 h following IR. Western blot was used to determine ERK and Bax protein levels. A non-parametric Kruskal–Wallis ANOVA test was used for statistical analysis with p < 0.05 considered statistically significant.

Results

Treatment of IR rats with O₃ resulted in a significant increase in mucosal weight in jejunum (70 %) and ileum (32 %), mucosal DNA (twofold increase) and protein (35 %) in ileum, villus height and crypt depth in jejunum (61 and 16 %, correspondingly) and ileum (31 and 43 %, correspondingly) compared to IR animals. IR-O₃ rats also had a significantly lower intestinal injury score as well as a lower apoptotic index in jejunum and ileum compared and IR animals. A significant increase in cell proliferation rates in IR-O₃ animals was accompanied by increased levels of p-ERK protein.

Conclusions

Treatment with ozone prevents intestinal mucosal damage, stimulates cell proliferation and inhibits programmed cell death following intestinal IR in a rat.     

Does ileal reverse segment in rats with short bowel syndrome change intestinal morphology?

BACKGROUND: The primary goal of surgical therapy for short bowel syndrome is to increase intestinal absorptive capacity. Many surgical procedures have been described for this purpose. One of these is ileal reverse-segment procedure. This procedure after massive small-bowel resection is an alternative way to treat short bowel syndrome, but how it affects intestinal morphology in short bowel syndrome has not been investigated. The aim of this study is to investigate macroscopic and microscopic effects of reverse-segment procedure on the short bowel. METHODS: Twenty rats underwent resection of 80% of the small bowel. The rats were separated into two groups (n = 10). In the first group (reverse group), a reverse segment was formed by twisting a 2-cm ileal segment 180 degrees, without damaging its vascularity. In the second group (control group), a 2-cm ileal segment was resected, preserving its mesentery, and end-to-end anastomosis was performed to maintain the intestinal passage. The segment was not twisted 180 degrees. The 2-cm proximal (jejunal) and distal (ileal) segments of the resected bowel were reserved for histologic investigation. Two months later, the rats were killed and the jejunal and ileal segments were evaluated morphologically. RESULTS: In the reverse group, body weight and total intestinal length significantly increased (14% more than in the control group). The diameter of both proximal (jejunal) and distal (ileal) segments in the reverse group also increased 53.8% and 22.8%, respectively ( P < 0.05). Histologically, crypt depth and villus height of the ileal segment in the reverse group increased 15.2% and 18.2% more than in the control group ( P < 0.05). No histologic change was observed at the jejunal level except for intestinal muscle thickness. CONCLUSIONS: Ileal reverse-segment procedure in rats with short bowel syndrome 1) does not cause intestinal obstruction, 2) increases total bowel length and body weight, 3) increases the diameter of both jejunal and ileal segments, and 4) increases villus height and crypt depth only at the ileal level. For this reason, reverse-segment procedure positively affects intestinal adaptation.     

Transforming growth factor-alpha stimulates enterocyte proliferation and accelerates intestinal recovery following methotrexate-induced intestinal mucositis in a rat and a cell culture model

Purpose  Recent evidence suggests that transforming growth factor-alpha (TGF-α) enhances enterocyte proliferation and exerts a gut trophic effect. The purpose of the present study was to evaluate the effect of TGF-α on enterocyte proliferation and intestinal recovery following methotrexate (MTX)-induced intestinal mucositis in rats and in Caco-2 cells. Methods  Nonpretreated Caco-2 cells and those pretreated with MTX were incubated with increasing concentrations of TGF-α. Cell proliferation was determined by FACS cytometry. Adult rats were divided into three groups: control rats treated with vehicle, MTX rats treated with one dose (20 μg/kg) of MTX given intraperitoneally, and MTX-TGF-α rats treated with one dose of MTX followed by two doses of TGF-α (75 μg/kg a day). Three days after MTX injection, rats were sacrificed. Intestinal mucosal damage (Park’s score), mucosal structural changes, and enterocyte proliferation were measured at sacrifice. Western blotting was used to determine the level of extracellular signal-related kinase (ERK) protein, a marker of cell proliferation. A nonparametric Kruskal–Wallis ANOVA test was used for statistical analysis with P value less than 0.05 considered statistically significant. Results  The in vitro experiment demonstrated that treatment with TGF-α of Caco-2 cells resulted in a significant stimulation of cell proliferation in a dose-dependent manner. The in vivo experiment showed that treatment with TGF-α resulted in a significant increase in bowel and mucosal weight, DNA and protein content in jejunum and ileum, villus height in jejunum and ileum, crypt depth in ileum, and increased cell proliferation in jejunum and ileum compared to the MTX group. MTX-TGF-α rats also had a significantly lower intestinal injury score in ileum when compared to MTX animals. The increase in levels of cell proliferation in MTX-TGF-α rats corresponded with the increase in ERK protein levels in intestinal mucosa. Conclusion  Treatment with TGF-α prevents mucosal injury, enhances ERK-induced enterocyte proliferation, and improves intestinal recovery following MTX-induced intestinal mucositis in rats. These findings correlated with the observation that TGF-α also caused a significant stimulation of cell proliferation in a Caco-2 cell culture model treated with MTX. These observations may have significant implications for the treatment of patients on chemotherapy who develop severe mucositis.     

Effect of simvastatin on intestinal recovery following gut ischemia–reperfusion injury in a rat

Background

Pleiotropic (lipid lowering-independent) effects of statins are attributed to their antiinflammatory, antioxidant, and/or vascular actions. Extensive studies in various experimental models have established that pretreatment with simvastatin significantly protects heart and kidney injured by ischemia–reperfusion (IR). The purpose of the present study was to examine the effect of simvastatin on intestinal recovery and enterocyte turnover after intestinal IR injury in rats.

Methods

Male Sprague–Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy, (2) IR-rats underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 48 h of reperfusion, and (3) IR-SIM rats underwent IR and were treated with oral simvastatin (10 mg/kg) given by gavage immediately before and 24 h after operation. Intestinal structural changes, Park’s injury score, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. A non-parametric Kruskal–Wallis ANOVA test was used for statistical analysis with P less than 0.05 considered statistically significant.

Results

Treatment with simvastatin resulted in a significant increase in bowel and mucosal weight in ileum, villus height and crypt depth in jejunum and ileum compared to IR animals. IR-SIM rats had also a significantly lower intestinal injury score as well as lower apoptotic index in jejunum and ileum compared to IR animals.

Conclusions

Treatment with simvastatin prevents gut mucosal damage and inhibits programmed cell death following intestinal IR in a rat.     

Effect of dietary fat on early morphological intestinal adaptation in a rat with short bowel syndrome

Among factors promoting mucosal hyperplasia after bowel resection, long-chain fatty acids may have a special role. The purpose of the present study was to evaluate the effects of high-fat diet (HFD) on early intestinal adaptation in rats with short bowel syndrome (SBS). Male Sprague-Dawley rats underwent either a bowel transection with re-anastomosis (Sham rats) or 75% small bowel resection (SBS rats). Animals were randomly assigned to one of three groups: Sham rats fed normal chow (Sham-NC); SBS rats fed NC (SBS-NC); and SBS rats fed HFD (SBS-HFD). Rats were killed on days 3 or 14. Body weight and parameters of intestinal adaptation (overall bowel and mucosal weight, mucosal DNA and protein, villus height, and crypt depth) were determined at time of killing. By day 3, SBS-HFD rats demonstrated higher duodenal and jejunal bowel and mucosal weights and ileal villus height and jejunal crypt depth vs SBS-NC rats. By day 14 SBS-HFD rats continued to demonstrate increased duodenal and jejunal bowel weight and duodenal mucosal weight vs SBS-NC animals. We conclude that early exposure to HFD both augmented and accelerated structural bowel adaptation in a rat model of SBS.