Intestinal Elongation Research Articles

Calcium wave dynamics in the embryonic mouse gut mesenchyme: impact on smooth muscle differentiation

Intestinal smooth muscle differentiation is a complex physico-biological process involving several different pathways. Here, we investigate the properties of Ca2+ waves in the developing intestinal mesenchyme using GCamp6f expressing mouse embryos and investigate their relationship with smooth muscle differentiation. We find that Ca2+ waves are absent in the pre-differentiation mesenchyme and start propagating immediately following α-SMA expression. Ca2+ waves are abrogated by CaV1.2 and gap-junction blockers, but are independent of the Rho pathway. The myosine light-chain kinase inhibitor ML-7 strongly disorganized or abolished Ca2+ waves, showing that perturbation of the contractile machinery at the myosine level also affected the upstream Ca2+ handling chain. Inhibiting Ca2+ waves and contractility with CaV1.2 blockers did not perturb circular smooth muscle differentiation at early stages. At later stages, CaV1.2 blockers abolished intestinal elongation and differentiation of the longitudinal smooth muscle, leading instead to the emergence of KIT-expressing interstitial cells of Cajal at the gut periphery. CaV1.2 blockers also drove apoptosis of already differentiated, CaV1.2-expressing smooth muscle and enteric neural cells. We provide fundamental new data on Ca2+ waves in the developing murine gut and their relation to myogenesis in this organ.

Developmental regulation of cellular metabolism is required for intestinal elongation and rotation.

Malrotation of the intestine is a prevalent birth anomaly, the etiology of which remains poorly understood. Here, we show that late-stage exposure of Xenopus embryos to atrazine, a widely used herbicide that targets electron transport chain (ETC) reactions, elicits intestinal malrotation at high frequency. Interestingly, atrazine specifically inhibits the cellular morphogenetic events required for gut tube elongation, including cell rearrangement, differentiation and proliferation; insufficient gut lengthening consequently reorients the direction of intestine rotation. Transcriptome analyses of atrazine-exposed intestines reveal misexpression of genes associated with glycolysis and oxidative stress, and metabolomics shows that atrazine depletes key glycolytic and tricarboxylic acid cycle metabolites. Moreover, cellular bioenergetics assays indicate that atrazine blocks a crucial developmental transition from glycolytic ATP production toward oxidative phosphorylation. Atrazine-induced defects are phenocopied by rotenone, a known ETC Complex I inhibitor, accompanied by elevated reactive oxygen species, and rescued by antioxidant supplementation, suggesting that malrotation may be at least partly attributable to redox imbalance. These studies reveal roles for metabolism in gut morphogenesis and implicate defective gut tube elongation and/or metabolic perturbations in the etiology of intestinal malrotation.

The IgSF Cell Adhesion Protein CLMP and Congenital Short Bowel Syndrome (CSBS).

The immunoglobulin-like cell adhesion molecule CLMP is a member of the CAR family of cell adhesion proteins and is implicated in human congenital short-bowel syndrome (CSBS). CSBS is a rare but very severe disease for which no cure is currently available. In this review, we compare data from human CSBS patients and a mouse knockout model. These data indicate that CSBS is characterized by a defect in intestinal elongation during embryonic development and impaired peristalsis. The latter is driven by uncoordinated calcium signaling via gap junctions, which is linked to a reduction in connexin43 and 45 levels in the circumferential smooth muscle layer of the intestine. Furthermore, we discuss how mutations in the CLMP gene affect other organs and tissues, including the ureter. Here, the absence of CLMP produces a severe bilateral hydronephrosis-also caused by a reduced level of connexin43 and associated uncoordinated calcium signaling via gap junctions.

Ingestible capsules carrying 3D printed springs: a possible future prospective for SBS treatment?

Background Short Bowel Syndrome (SBS) is a malabsorption syndrome characterised by a severe reduction of the absorbent surface of the intestinal mucosa. Treatment of this condition needs multi-professional teams and different therapies, which are not always enough to ensure enteral autonomy. New techniques are being explored, particularly distraction enterogenesis, which can allow the lengthening of the residual intestines of these patients. This study aims to demonstrate the possibility of using biodegradable materials to design ingestible capsules which carry 3D-printed springs capable of reaching the patient’s intestine. These devices could be used as a slightly invasive distraction enterogenesis technique, stimulating cell proliferation and intestinal elongation without surgery. Materials and methods Capsules were realised with gelatin from pigskin type A from Sigma-Aldrich mixed with regenerated silk fibroin (RS) obtained by reverse engineering on Bombyx Mori cocoons. Springs are composed of a structure of regenerated silk (RS) modified with graphene nanoplatelets (GNP) externally covered with a biodegradable polyhydroxybutyrate-valerate (PHBV) shell. Springs were realised with 3D printing, through which, with an extruder, PHBV and RS compounds are deposited simultaneously in a 3D structure. The springs’ capsules were then analysed with solvents simulating the gastric and intestinal environment to verify their resistance to degradation. PBS (Phosphate Buffered Saline), composed of calcium chloride and magnesium chloride (CaCl 2 + MgCl 2 ), with a pH value of 7.4, was used as a degradative agent; for the gastric tract, we chose the acetic acid, CH 3 COOH, at 12% with a pH value of 2.3. Results While the gelatin-only capsules showed poor resistance to degradation in PBS, the new compound based on gelatin and regenerated silk showed excellent resistance in gastric and intestinal environments, allowing the pills to reach the intestine without dissolving. In addition, the results show variability in the release times of the springs as a function of the pH values and the elastic constants of the springs used: the latter determined that in acetic acid, the release time is increased at an increase of the elastic constant. In contrast, in PBS, an opposite trend was observed. Conclusions Our results confirm the possibility of using gelatin, silk fibroin and PHBV to design devices capable of transporting implantable endoluminal 3D structures, drugs, or growth factors, laying the foundations for a new approach to distraction enterogenesis in SBS patients.

The long Filamin-A isoform is required for intestinal development and motility: implications for chronic intestinal pseudo-obstruction.

Filamin A (FLNA) is a cytoplasmic actin binding protein, recently shown to be expressed as a long and short isoform. Mutations in FLNA are associated with a wide spectrum of disorders, including an X-linked form of chronic intestinal pseudo-obstruction (CIPO). However, the role of FLNA in intestinal development and function is largely unknown. In this study, we show that FLNA is expressed in the muscle layer of the small intestine from early human fetal stages. Expression of FLNA variants associated with CIPO, blocked expression of the long flna isoform and led to an overall reduction of RNA and protein levels. As a consequence, contractility of human intestinal smooth muscle cells was affected. Lastly, our transgenic zebrafish line showed that the flna long isoform is required for intestinal elongation and peristalsis. Histological analysis revealed structural and architectural changes in the intestinal smooth muscle of homozygous fish, likely triggered by the abnormal expression of intestinal smooth muscle markers. No defect in the localization or numbers of enteric neurons was observed. Taken together, our study demonstrates that the long FLNA isoform contributes to intestinal development and function. Since loss of the long FLNA isoform does not seem to affect the enteric nervous system, it likely results in a myopathic form of CIPO, bringing new insights to disease pathogenesis.

Hyaluronic acid promotes Lgr5+ stem cell proliferation and crypt fission through TLR4 and PGE2 transactivation of EGFR.

Hyaluronic acid (HA), a glycosaminoglycan in the extracellular matrix, binds to CD44 and Toll-like receptor 4 (TLR4). We previously demonstrated that both CD44 and TLR4, but predominately TLR4, mediated HA stimulation of Lgr5+ stem cell proliferation, crypt fission, and intestinal growth in postnatal mice. Here we address the questions of which cell type expresses the relevant TLR4 in driving intestinal growth and what are the downstream events from TLR4 activation. Studies were done in 14-day-old mice: wild type (WT), mice deficient in cyclooxygenase 2 (COX2), mice deficient in myeloid cell TLR4, and mice deficient in epithelial cell epidermal growth factor receptor (EGFR). Biological end points included crypt fission and Lgr5 cell proliferation. In WT mice, treatment with NS-398 (a COX2 inhibitor), clodronate (a macrophage-depleting agent), or tyrphostin (an EGFR inhibitor) resulted in 30% reductions in crypt fission and Lgr5+ stem cell proliferation compared with control mice. Mice deficient in COX2 or myeloid TLR4 or epithelial cell EGFR all had 30% reductions in crypt fission and Lgr5+ stem cell proliferation compared with WT mice. Administration of dimethyl PGE2, a stable PGE2 analog, increased crypt fission and Lgr5+ stem cell proliferation. Administration of dimethyl PGE2 reversed the effects of NS-398, clodronate, COX2 deficiency, and myeloid TLR4 deficiency but had no effect on mice treated with tyrphostin or mice deficient in epithelial cell EGFR. We conclude that, in postnatal mice, ~30% of intestinal growth as manifested by crypt fission and Lgr5+ stem cell proliferation is driven by a novel pathway: Extracellular HA binds TLR4 on pericryptal macrophages, inducing the production of PGE2 through COX2. PGE2 transactivates EGFR in Lgr5+ epithelial stem cells, resulting in Lgr5+ stem cell proliferation and crypt fission.NEW & NOTEWORTHY This study, in newborn mice, describes a novel molecular pathway regulating Lgr5+ epithelial stem cell proliferation and normal intestinal elongation, as assessed by crypt fission. In this pathway, endogenous extracellular hyaluronic acid binds to Toll-like receptor 4 on pericryptal macrophages releasing PGE2 which binds to epidermal growth factor receptor on Lgr5+ stem cells resulting in proliferation. Lgr5+ stem cell proliferation leads to crypt fission and intestinal elongation. The demonstration that normal growth requires microbial-independent Toll-like receptor activation is novel.

Glypican-6 stimulates intestinal elongation by simultaneously regulating Hedgehog and non-canonical Wnt signaling

We report here that Glypican-6 (GPC6)-null mice display at birth small intestines that are 75% shorter than those of normal littermates. Notably, we demonstrate that the role of GPC6 in intestinal elongation is mediated by both Hedgehog (Hh) and non-canonical Wnt signaling. Based on results from in vitro experiments, we had previously proposed that GPC6 stimulates Hh signaling by interacting with Hh and Patched1 (Ptc1), and facilitating/stabilizing their interaction. Here we provide strong support to this hypothesis by showing that GPC6 binds to Ptc1 in the mesenchymal layer of embryonic intestines. This study also provides experimental evidence that strongly suggests that GPC6 inhibits the activity of Wnt5a on the intestinal epithelium by binding to this growth factor, and reducing its release from the surrounding mesenchymal cells. Finally, we show that whereas the mesenchymal layer of GPC6-null intestines displays reduced cell proliferation and a thinner smooth muscle layer, epithelial cell differentiation is not altered in the mutant gut.

Morphological changes and habitat shifts with growth of endangered floodplain fish: Possible adaptations to fluctuating environments

AbstractAdaptations that maximise food intake are dependent on food and/or habitat types. However, there have been few studies on the ability of floodplain primary freshwater fish to rapidly change their morphology, especially the internal one, to maximise utilisation efficiency of food resources in response to environmental fluctuations during their life history. We investigated morphological changes of an Acheilognathinae species (Acheilognathus longipinnis) that inhabits creeks in Japan to determine whether body shape variation correlated with environmental characteristics, including water depth, current velocity, vegetation cover and food availability. When shifting from floodwater‐level to low‐water‐level season, the current velocity of the study area increased as the water level decreased, causing a significant increase in periphyton and a significant decline in zooplankton and phytoplankton. Concurrently, during the short period when A. longipinnis grow from the juvenile to the premature stage, changes in internal morphology, that is intestinal elongation, and changes in external morphology such as an increase of body depth were observed. In contrast, intestinal length significantly decreased in the adult stage. Our findings suggest that morphological changes between floodwater‐level and low‐water‐level seasons associated with juvenile to premature development are an adaptation to changes in food availability due to environmental fluctuations. Additionally, the shortening of the intestine from the premature to the adult stage may be an adaptive strategy for reproduction.

WNT5A Encodes Two Isoforms with Distinct Functions in Cancers

WNT5A, a member of the WNT family of secreted lipid-modified glycoproteins, is a critical regulator of a host of developmental processes, including limb formation, lung morphogenesis, intestinal elongation and mammary gland development. Altered WNT5A expression has been associated with a number of cancers. Interestingly, in certain types of cancers, such as hematological malignancies and colorectal carcinoma, WNT5A is inactivated and exerts a tumor suppressive function, while in other cancers, such as melanoma and gastric carcinoma, WNT5A is overexpressed and promotes tumor progression. The mechanism by which WNT5A achieves these distinct activities in cancers is poorly understood. Here, we provide evidence that the WNT5A gene produces two protein isoforms, WNT5A-long (WNT5A-L) and WNT5A-short (WNT5A-S). Amino-terminal sequencing and a WNT5A-L specific antibody demonstrate that the mature and secreted isoforms are distinct, with WNT5A-L carrying an additional 18 N-terminal amino acids. Biochemical analysis indicates that both purified proteins are similar with respect to their stability, hydrophobicity and WNT/β-catenin signaling activity. Nonetheless, modulation of these two WNT5A isoforms, either through ectopic expression or knockdown, demonstrates that they exert distinct activities in cancer cell lines: while WNT5A-L inhibits proliferation of tumor cell lines, WNT5A-S promotes their growth. Finally, we show that expression of these two WNT5A isoforms is altered in breast and cervix carcinomas, as well as in the most aggressive neuroblastoma tumors. In these cancers, WNT5A-L is frequently down-regulated, whereas WNT5A-S is found overexpressed in a significant fraction of tumors. Altogether, our study provides evidence that the distinct activities of WNT5A in cancer can be attributed to the production of two WNT5A isoforms.

Induced Wnt5a expression perturbs embryonic outgrowth and intestinal elongation, but is well-tolerated in adult mice

Wnt5a is essential during embryonic development, as indicated by mouse Wnt5a knockout embryos displaying outgrowth defects of multiple structures including the gut. The dynamics of Wnt5a involvement in these processes is unclear, and perinatal lethality of Wnt5a knockout embryos has hampered investigation of Wnt5a during postnatal stages in vivo. Although in vitro studies have suggested a relevant role for Wnt5a postnatally, solid evidence for a significant impact of Wnt5a within the complexity of an adult organism is lacking. We generated a tightly-regulated inducible Wnt5a transgenic mouse model and investigated the effects of Wnt5a induction during different time-frames of embryonic development and in adult mice, focusing on the gastrointestinal tract. When induced in embryos from 10.5dpc onwards, Wnt5a expression led to severe outgrowth defects affecting the gastrointestinal tracts, limbs, facial structures and tails, closely resembling the defects observed in Wnt5a knockout mice. However, Wnt5a induction from 13.5dpc onwards did not cause this phenotype, indicating that the most critical period for Wnt5a in embryonic development is prior to 13.5dpc. In adult mice, induced Wnt5a expression did not reveal abnormalities, providing the first in vivo evidence that Wnt5a has no major impact on mouse intestinal homeostasis postnatally. Protein expression of Wnt5a receptor Ror2 was strongly reduced in adult intestine compared to embryonic stages. Moreover, we uncovered a regulatory process where induction of Wnt5a causes downregulation of its receptor Ror2. Taken together, our results indicate a role for Wnt5a during a restricted time-frame of embryonic development, but suggest no impact during homeostatic postnatal stages.

Mo1978 Induced WNT5A Expression is Well-Tolerated in Adult Mice, but Perturbs Outgrowth and Intestinal Elongation in Embryos

Mo1978 Induced WNT5A Expression is Well-Tolerated in Adult Mice, but Perturbs Outgrowth and Intestinal Elongation in Embryos

274 Antioxidant Supplementation Improves Inflammatory Nitrergic Dysfunction in Diabetic Biobreeding Prone Rats

Introduction: Loss of intestinal nitrergic motor control has been reported in Biobreeding diabetes-prone (BBDP) rats (Zandecki 2008). We previously demonstrated that loss of jejunal neuronal nitric oxide synthase (nNOS) mRNA expression occurs in the BBDP, which is related to transient intestinal inflammation (myeloperoxidase: MPO activity) and inducible nitric oxide synthase (iNOS) expression, and which is independent from the development of hyperglycemia (Kindt DDW 2009). Studies in enteric neuron cultures suggest that iNOS overexpression downregulates nNOS expression through oxidative stress (Zandecki 2006). Moreover, aminoguanidine an iNOS inhibitor, counteracts the inflammation-induced nitrergic dysfunction and prevents intestinal elongation and dilatation caused by a 3cm H2O pressure stimulus in normoglycemic BBDP (Masaoka DDW 2011). Aim: To investigate the pathophysiological role of oxidative stress in inflammatory nitrergic dysfunction, we designed a controlled antioxidant supplementation study. Methods: BBDP were fed chow supplemented with 2% vitamin E (α-tocopherol) and 2g/l vitamin C (ascorbic acid) in the drinking water from 21days onwards. After onset of diabetes, 1% vitamin E and 1g/l vitamin C were supplemented to compensate for polyphagia and polydypsia. All rats were sacrificed at 220days. Jejunal inflammation, spontaneous intestinal motility, nitrergic neuron number and nNOS mRNA expression were analyzed respectively by MPO measurements, organ bath (37°C) video analysis, NADPH-diaphorase staining and realtime PCR, both in antioxidant supplemented animals and in a control group of age-matched non-supplemented diabetic animals. Results: Compared with controls (n=7), MPO activity decreased significantly in the antioxidant supplemented group (n=6) (9.9±3.9 vs. 2.1±1.4 U/mg, p 0.05) of a 5-cm jejunum segment in response to intraluminal pressure rise In Vitro. Conclusion: Antioxidant supplementation improves inflammation-induced nitrergic dysfunction and partially prevents intestinal dysmotility in diabetic BBDP.

A rat decellularized small bowel scaffold that preserves villus-crypt architecture for intestinal regeneration

Management of intestinal failure remains a clinical challenge and total parenteral nutrition, intestinal elongation and/or transplantation are partial solutions. In this study, using a detergent-enzymatic treatment (DET), we optimize in rats a new protocol that creates a natural intestinal scaffold, as a base for developing functional intestinal tissue. After 1 cycle of DET, histological examination and SEM and TEM analyses showed removal of cellular elements with preservation of the native architecture and connective tissue components. Maintenance of biomechanical, adhesion and angiogenic properties were also demonstrated strengthen the idea that matrices obtained using DET may represent a valid support for intestinal regeneration.

Intestinal failure-associated liver disease in surgical infants requiring long-term parenteral nutrition

PurposeOur aim was to determine incidence, severity, and outcome, as well as predisposing factors and underlying diagnoses, of intestinal failure-associated liver disease (IFALD) in surgical infants requiring long-term parenteral nutrition (PN). MethodsWe retrospectively studied surgical infants receiving PN for at least 28 days for congenital or acquired intestinal anomalies over a 5-year period (January 2006 to December 2010). Intestinal failure-associated liver disease was defined as type 1 (early)—persistent elevation of alkaline phosphatase for 6 weeks or longer; type 2 (established)—additional elevated total bilirubin (≥50 μmol/L); and type 3 (late)—additional clinical signs of end-stage liver disease. ResultsEighty-seven infants required PN for at least 28 days. Intestinal failure-associated liver disease occurred in 29 infants (33%). Intestinal failure-associated liver disease was managed medically in all but 2 patients who underwent intestinal elongation. None were referred for intestinal or liver transplant. Intestinal failure-associated liver disease has been reversed in 17 (59%) of cases to date. Sixty-one children receiving long-term PN (70%) have achieved enteral autonomy, whereas 12 (14%) require home PN. Severity of IFALD was significantly associated with duration of PN and female sex. ConclusionIntestinal failure-associated liver disease remains a fairly common but rarely life-threatening complication of intestinal failure in surgical infants. Intestinal failure-associated liver disease can be reversed in more than half of these children, and enteral autonomy was achieved in more than two thirds, even with minimal use of intestinal elongation. This is the first study to demonstrate an association between the severity of IFALD in surgical infants and female sex.

Application of acellular dermal matrix for intestinal elongation in animal models

To investigate the efficacy of acellular dermal matrix (ADM) for intestinal elongation in animal models. Japanese white big-ear rabbits (n = 9) and Wuzhishan miniature pigs (n = 5) were used in the study. Home-made and commercial ADM materials were used as grafts, respectively. A 3-cm long graft was interposed in continuity with the small bowel and a side-to-side anastomosis, distal to the graft about 3-4 cm, was performed. The animals were sacrificed at 2 wk, 4 wk, 8 wk and 3 mo after surgery and the histological changes were evaluated under light microscope and electron microscope. The animals survived after the operation with no evidence of peritonitis and sepsis. Severe adhesions were found between the graft and surrounding intestine. The grafts were completely absorbed within postoperative two or three months except one. Histological observation showed inflammation in the grafts with fibrinoid necroses, infiltration of a large amount of neutrophils and leukomonocytes, and the degree varied in different stages. The neointestine with well-formed structures was not observed in the study. It is not suitable to use acellular dermal matrix alone as a scaffold for the intestinal elongation in animal models.

α-Lactalbumin Hydrolysate Stimulates Glucagon-Like Peptide-2 Secretion and Small Intestinal Growth in Suckling Rats ,

We investigated whether bovine milk constituents influenced glucagon-like peptide (GLP)-2 secretion and intestinal growth in suckling rats. Male Sprague-Dawley rats (14 d old) received i.g. infusions of a milk protein fraction, a lactose solution, or the cream fraction of milk. The serum concentration of GLP-2, but not GLP-1, markedly increased in rats administered milk protein compared with those given the lactose solution or the cream fraction from 60 to 120 min after administration. In another experiment, both casein (CN) and whey protein isolate stimulated GLP-2 secretion at 120 min after administration, but soy protein and ovalbumin did not. Stimulation of GLP-2 secretion by several milk proteins was similar, including α-CN, α-lactalbumin (α-La), and β-lactoglobulin, in a separate experiment. A hydrolysate of α-La obtained by incubation with protease A extracted from Aspergillus oryzae (LaHPA) caused almost twice the GLP-2 release due to intact α-La and other α-La hydrolysates. Free amino acid concentrations and molecular size distributions did not differ among α-La hydrolysates, including LaHPA. In rat pups reared with milk formulae containing α-La or LaHPA, LaHPA significantly promoted small intestinal elongation and increased the number of crypt epithelial cells compared with a formula containing intact α-La. LaHPA administration also increased the maltase:lactase activity ratio, a marker of maturation of the intestinal mucosa. In conclusion, milk proteins stimulate GLP-2 secretion and contribute to growth and maturation of the small intestine in suckling rats.

Wnt5a is essential for intestinal elongation in mice

Morphogenesis of the mammalian small intestine entails extensive elongation and folding of the primitive gut into a tightly coiled digestive tube. Surprisingly, little is known about the cellular and molecular mechanisms that mediate the morphological aspects of small intestine formation. Here, we demonstrate that Wnt5a, a member of the Wnt family of secreted proteins, is essential for the development and elongation of the small intestine from the midgut region. We found that the small intestine in mice lacking Wnt5a was dramatically shortened and duplicated, forming a bifurcated lumen instead of a single tube. In addition, cell proliferation was reduced and re-intercalation of post-mitotic cells into the elongating gut tube epithelium was disrupted. Thus, our study demonstrates that Wnt5a functions as a critical regulator of midgut formation and morphogenesis in mammals.

Fgf9 signaling regulates small intestinal elongation and mesenchymal development

Short bowel syndrome is an acquired condition in which the length of the small intestine is insufficient to perform its normal absorptive function. Current therapies are limited as the developmental mechanisms that normally regulate elongation of the small intestine are poorly understood. Here, we identify Fgf9 as an important epithelial-to-mesenchymal signal required for proper small intestinal morphogenesis. Mouse embryos that lack either Fgf9 or the mesenchymal receptors for Fgf9 contained a disproportionately shortened small intestine, decreased mesenchymal proliferation, premature differentiation of fibroblasts into myofibroblasts and significantly elevated Tgfbeta signaling. These findings suggest that Fgf9 normally functions to repress Tgfbeta signaling in these cells. In vivo, a small subset of mesenchymal cells expressed phospho-Erk and the secreted Tgfbeta inhibitors Fst and Fstl1 in an Fgf9-dependent fashion. The p-Erk/Fst/Fstl1-expressing cells were most consistent with intestinal mesenchymal stem cells (iMSCs). We found that isolated iMSCs expressed p-Erk, Fst and Fstl1, and could repress the differentiation of intestinal myofibroblasts in co-culture. These data suggest a model in which epithelial-derived Fgf9 stimulates iMSCs that in turn regulate underlying mesenchymal fibroblast proliferation and differentiation at least in part through inhibition of Tgfbeta signaling in the mesenchyme. Taken together, the interaction of FGF and TGFbeta signaling pathways in the intestinal mesenchyme could represent novel targets for future short bowel syndrome therapies.

A Novel Approach for Intestinal Elongation Using Acellular Dermal Matrix: An Experimental Study in Rats

We tested the hypothesis that an anatomic scaffold placed in continuity with viable bowel might allow intestinal growth. Male ACI rats were used for the study. Acellular human dermis in the form of tubular scaffolds with an intraluminal diameter of approximately 0.3 cm was oriented with the luminal basement membrane and serosal dermal surface. The small bowel was transected approximately 2 cm distal to the ligament of Treitz. The graft was then anastomosed in continuity in group A ( n = 5) or as a blind-ended pouch to a defunctionalized jejunal limb in group B ( n = 8). The animals were sacrificed at various time points. Histology and immunohistochemistry were used to evaluate structural changes. Animals in group A developed peritonitis and were all sacrificed within the first week postoperatively. However, all animals in group B survived, increasing their body weight similarly to age-matched rats. Tissue samples obtained at sacrifice showed a progressively increasing amount of cellular infiltrate over time in the matrix. Epithelial regeneration, angioneogenesis, and myofibroblast infiltrate were seen at 2 weeks, while well-formed branching crypts were seen at 4 weeks. Intact mucosa extended across the anastomosis to the grafts at 6 months. This study demonstrated an anatomic scaffold of acellular matrix allowed mucosal regeneration from viable bowel placed in continuity. These findings set the basis for new intestinal elongation techniques.

Retinoic Acid and Intestinal Wound Healing in Intra-operatively Irradiated Rat

Aim: This study was undertaken to assess the effect of intra-operative radiotherapy on intestinal wound healing and prevention of its side effects by retinoic acid.Materials and methods: Thirty Spraque-Dawley rats were divided into 3 groups of (n = 10). All the groups had laparotomies and terminal ileum exteriorization. Group I was the control group with no irradiation and no anastomosis; group II had both irradiation and anastomosis and group III rats had peroral retinoic acid conditioning and irradiation + anastomosis. On the seventh postoperative day, tensile strength and intestinal elongation measurements were to evaluate the effect of retinoic acid on wound healing.Results: Compared to the non-retinoic acid conditioned group, the retinoic acid conditioned group had statistically significant higher tensile strength and lower intestinal elongation values, revealing better wound healing. Conclusion: Peroral retinoic acid supplement administration has a preventive effect on radiation-induced wound-healing inhibition in intra-operative abdominopelvic irradiation and anastomoses.