Collagen changes around intestinal anastomoses in germ-free rats

Immune activation by microbiome shapes the colon mucosa: Comparison between healthy rat mucosa under conventional and germ-free conditions

Germ-free animals (GF) are those without a microbiome since birth. This particular biological model has become one of special interest with the growing evidence of importance of the microbiome in the life, development, adaptation, and immunity of humans and animals in the environments in which they live. Anatomical differences observed in GF compared with conventionally-reared animals (CV) has given rise to the question of the influence of commensal microflora on the development of structure and function (even immunological) of the bowel. Only recently, thanks to achievements in microscopy and associated methods, structural differences can be better evaluated and put in perspective with the immunological characteristics of GF vs. CV animals. This study, using a GF rat model, describes for the first time the possible influence that the presence of commensal microflora, continuously stimulating mucosal immunity, has on the collagen scaffold organization of the colon mucosa. Significant differences were found between CV and GF mucosa structure with higher complexity in the CV rats associated to a more activated immune environment. The immunological data suggest that, in response to the presence of a microbiome, an effective homeostatic regulation in developed by the CV rats in healthy conditions to avoid inflammation and maintain cytokine levels near the spontaneous production found in the GF animals. The results indicated that collagen scaffold adapted to the immune microenvironment; therefore, it is apparent that the microbiome was able to condition the structure of the colon mucosa.

EFFECT OF SUPPLEMENTATION WITH PROBIOTICS ON COLONIC ANASTOMOSES IN RATS: MORPHOLOGICAL AND TENSIOMETRIC STUDY

Background:

The use of probiotics positively modifies the composition and function of intestinal flora, improving the quality of intestinal anastomosis.

Aim:

To evaluate the impact of probiotic use on intestinal anastomosis of rats.

Method:

Thirty-six adult male Wistar rats (Rattus norvegicus albinus, Rodentia Mammalia) were used, with body weight ranging from 220-320 g. The animals were housed and acclimated individually in boxes receiving water and ration ad libitum. After initial acclimatization, the control group received perioperative ration ad libitum for 12 days (seven preoperatively and five postoperatively) associated with the maltodextrin formula at a dose of 250 mg/day in isocaloric and isovolumetric form. Likewise, the probiotic group received oral supplementation of probiotics dose of 250 mg/day, associated with isocaloric and isovolumetric diet. The probiotic chosen for this study was composed of strains (doses 1x10⁹ CFU/g)¹²Lactobacillus paracasei LPC-37, Bifidobacterium lactis HN0019, Lactobacillus rhamnosus HN001 and Lactobacillus acidophilus NCFM. Probiotics or placebo were administered orally with the aid of a dosimeter spatula. Both groups underwent two colostomies, one in the right colon and the second in rectosigmoid, followed by reanastomosis with eight separate 6-0 mononylon stitches. The sacrifice took place on the fifth day. The parameters evaluated included tensile strength, histology and collagen densitometry.

Results:

The rate of intestinal fistula for the control and probiotic groups were, respectively, 22.22% and 11.11% (p=0.6581).Perioperative supplementation with probiotics increased collagen deposition of types I and III (p<0.0001), improved maximum traction force and maximum rupture force, p=0.0250 and p=0.0116 respectively, fibrosis area (p<0.0001), and area of the inflammatory infiltrate (p=0.0115).

Conclusions:

The use of probiotics had a positive impact on the quality of intestinal anastomosis.

Intestinal anastomotic injury alters spatially defined microbiome composition and function

BACKGROUND

When diseased intestine (i.e., from colon cancer, diverticulitis) requires resection, its reconnection (termed anastomosis) can be complicated by non-healing of the newly joined intestine resulting in spillage of intestinal contents into the abdominal cavity (termed anastomotic leakage). While it is suspected that the intestinal microbiota have the capacity to both accelerate and complicate anastomotic healing, the associated genotypes and functions have not been characterized.

RESULTS

Using 16S rRNA amplicon sequencing of samples collected on the day of surgery (postoperative day 0 (POD0)) and the 6th day following surgery (postoperative day 0 (POD6)), we analyzed the changes in luminal versus tissue-associated microbiota at anastomotic sites created in the colon of rats. Results indicated that anastomotic injury induced significant changes in the anastomotic tissue-associated microbiota with minimal differences in the luminal microbiota. The most striking difference was a 500-fold and 200-fold increase in the relative abundance of Enterococcus and Escherichia/Shigella, respectively. Functional profiling predicted the predominance of bacterial virulence-associated pathways in post-anastomotic tissues, including production of hemolysin, cytolethal toxins, fimbriae, invasins, cytotoxic necrotizing factors, and coccolysin.

CONCLUSION

Taken together, our results suggest that compositional and functional changes accompany anastomotic tissues and may potentially accelerate or complicate anastomotic healing.

Efeito da suplementação oral de vitamina C na resistência anastomótica intestinal

OBJETIVO: Comparar a resistência cicatricial de anastomoses e de segmentos íntegros jejunais de ratos, submetidos à administração de vitamina C, em distintos períodos pós-operatórios. MÉTODOS: Foram estudados 50 ratos Wistar, submetidos a enterotomia seguida de anastomose término-terminal de segmento jejunal, a 10 cm da flexura duodenojejunal. Os animais foram distribuídos em dois grupos (n=25): Grupo I - controle; Grupo II - administração de vitamina C oral 100 mg/kg. Avaliaram-se as pressões de ruptura anastomótica e do segmento íntegro jejunal nos 3º, 5º, 7º, 21º E 28º dias do pós-peratório. RESULTADOS: Os ratos que receberam vitamina C apresentaram pressão de ruptura anastomótica maior nos 5º, 7º, e 28º dias pós-operatórios. O mesmo ocorreu com as pressões de ruptura do segmento íntegro jejunal dos ratos. CONCLUSÃO: A vitamina C aumentou a resistência das anastomoses jejunais dos ratos, tanto no pós-operatório imediato quanto no tardio. Além disso, a resistência final dos segmentos jejunais íntegros dos ratos submetidos à administração de vitamina C foi significativamente maior do que no Grupo Controle.

Transient perioperative pharmacologic inhibition of muscularis macrophages as a target for prophylaxis of postoperative ileus does not affect anastomotic healing in mice

BACKGROUND

Postoperative ileus is mediated through a severe inflammation of the tunica muscularis. Inhibition of initially involved muscularis macrophages could be a promising clinical approach to prevent postoperative ileus. The aim of this study was to investigate whether pharmacologic or genetic depletion of these inflammatory cells influences anastomotic healing.

METHODS

Standardized ileal anastomoses were performed and the mice were randomized into 4 groups: (1) wild type; (2) pharmacologically depleted and inactivated, by means of chlodronate liposomes and gadolinium chloride; (3) heterozygous osteopetrosis littermates; (4) genetically depleted osteopetrosis mutant mice. Tissues from the anastomoses were removed 2, 5, and 14 days after surgery and used for molecular (collagen 1 and 3, matrix metalloproteinases 2, 9, and 13 expressions), histochemical (anastomotic healing score, cross polarization microscopy) and functional (anastomotic bursting pressure) investigations.

RESULTS

RT-PCR measurements demonstrated that the investigated genetic events were similar between controls and macrophage-depleted groups. Comparison of histologic healing scores and bursting pressure values showed no significant differences between the groups. Finally, cross polarization microscopy on picrosirius-red stained sections revealed no obvious disturbance in production and deposition of collagen.

CONCLUSION

In our current model we demonstrate that transient perioperative pharmacologic and genetic muscularis macrophage inhibition does not affect intestinal anastomotic healing. These results call for further investigations to establish a pharmacologic prophylaxis for the prevention of postoperative ileus.

Do low-molecular-weight heparins influence the healing process in colon anastomosis?

Anastomosis leakage is one of the most serious complications of colorectal surgery. A role for extracellular matrix remodelling in the healing process of the colon wall has been recently postulated. Changes in matrix metalloproteinase (MMP) activity in the intestinal wall occurring prior to elective resection and primary anastomosis appear to be responsible for dehiscence leading to anastomosis. Thrombophylaxis using low-molecular-weight heparins is routinely administered to all patients during the perioperative period. However, adverse antiproliferative and proapoptotic effects such as limitation of bioavailability of growth factors and angiogenesis inhibition have been characterized in various cell types as a result of heparin administration. It is also likely that relationships exist between extracellular matrix homeostasis and the coagulation/fibrinolysis system. We hypothesize that subcutaneous administration of LMWHs (low-molecular-weight heparins) may influence matrix metalloproteinase activity in the colon wall and increase the risk of postoperative leakage.

Mycophenolate mofetil impairs healing of left-sided colon anastomoses

INTRODUCTION

Inadequate healing and consequent leakage from bowel anastomoses are a significant cause of postoperative morbidity and mortality. Immunosuppressive drugs are known to disturb healing processes and to impair the mechanical stability of bowel anastomosis. Mycophenolate mofetil (MMF) is an immunosuppressive agent that selectively inhibits the proliferation of T and B lymphocytes and has been shown to be effective in preventing allograft rejection after organ transplantation. Adverse effects are few; however, nothing is known in regard to possible adverse effects of MMF administration on the healing of bowel anastomosis. The aim of the present study was to evaluate the effect of systemic MMF administration on the healing of colon anastomoses in rats.

METHODS

Rats underwent laparotomy, division of the left colon, and sigmoidostomy. MMF (25 mg/kg) or vehicle was administered intraperitoneally in two groups (n=21 per group) 3 days before surgery and then once daily until euthanization (7 animals per group; 2, 4, and 6 days after surgery). Bursting pressure measurements, histologic evaluation, morphometric analysis, mucin and collagen staining, and BrdU immunohistochemistry of the anastomotic site were performed. Furthermore, matrix protein expression at the anastomotic site was determined by collagen I and fibronectin Western blots.

RESULTS

Administration of MMF significantly decreased anastomotic bursting pressure postoperatively. Accordingly, histology, mucin staining, and BrdU immunohistochemistry and measurements of the colonic crypt depth showed more extended inflammation, a significantly lower proliferation rate, and a significantly thinned mucosal layer in the MMF-treated groups when compared to control animals, whereas matrix synthesis at the anastomotic site was not different.

CONCLUSIONS

The administration of the immunosuppressive agent MMF significantly impairs healing and mechanical stability of colon anastomosis in rats during the early postoperative period. MMF act to disturb host reparative processes mainly by impairment of reparative colonic epithelium proliferation and less by a disturbance of matrix synthesis.

[Influence of ascorbic acid on anastomosis and in jejunal loop in rat]

BACKGROUND

The effects of vitamin C on anastomotic healing process are controversial.

OBJECTIVE

To compare the jejunal anastomotic tension and in the upright segment in different postoperative periods.

METHOD

Fifty male rats weighing 250 to 400 grams were submitted to laparotomy. The jejunum was transversally cut 10 cm from the duodenojejunal flexure, and subsequently anastomosed. The rats were divided into two groups (n = 25). Group I--control, Group II--oral administration of vitamin C (100 mg/kg). The anastomotic and the upright segment resistance was determined by using bursting pressure test on the 3rd, 5th, 7th, 21st and 28th postoperative days.

RESULTS

The rats submitted to oral administration of ascorbic acid show higher bursting pressure on the 5th, 7th and 28th postoperative days. The bursting resistances of the upright segment was higher on the rats submitted to vitamin C ingestion.

CONCLUSIONS

Vitamin C enhances the anastomotic and jejunal resistances. Moreover, the final resistance on the upright jejunal segment was significant higher than in the control group.

Influência da vitamina C e da hidrocortisona sobre a tensão anastomótica jejunal em ratos

O efeito da vitamina C e da hidrocortisona sobre os processos cicatriciais anastomóticos apresenta resultados conflitantes na literatura. Dessa forma, o presente trabalho teve o objetivo de comparar a resistência cicatricial de anastomoses jejunais em ratos, submetidos à administração de vitamina C e de hidrocortisona, em distintos períodos pós-operatórios. Foram estudados 40 ratos Wistar, submetidos a secção e subseqüente anastomose término-terminal de segmento jejunal, a 10 cm da flexura duodenojejunal. Os animais foram divididos em quatro grupos (n=10): Grupo I - controle; Grupo II - administração de vitamina C oral 100 mg/kg; Grupo III - administração de hidrocortisona intraperitoneal 10 mg/kg; Grupo IV - administração de vitamina C mais hidrocortisona nas doses e vias de administração acima. Avaliaram-se as pressões de ruptura anastomótica nos 5 º e 21º dias pós-operatórios. Os ratos que receberam vitamina C isolada ou associada a hidrocortisona tenderam a uma pressão de ruptura maior do que os demais grupos, tanto no 5º quanto no 21º dias pós-operatórios. Os resultados deste trabalho sugerem que a vitamina C contribui para aumentar a resistência das anastomoses jejunais dos ratos durante os primeiros 5 dias pós-operatórios. A resistência das anastomoses jejunais murinas foi pouco influenciada pela administração de corticóide intraperitoneal.

Influência da peritonite sobre a síntese de colágeno em anastomoses do cólon distal: estudo experimental em ratos

Com o objetivo de verificar a relação entre a concentração de colágeno e a capacidade de suportar pressão em anastomoses de cólon quando existe peritonite, utilizaram-se 40 ratos machos, Wistar-TECPAR, com idade média de 120 dias e peso médio de 302 g, os quais foram divididos em 2 lotes de 20 animais que compuseram os grupos controle e peritonite. Sob anestesia inalatória e submetidos à laparotomia os ratos do grupo peritonite tiveram infecção induzida pelo método de Wichterman e col. e os do grupo controle laparotomia com manipulação dos segmentos intestinais envolvidos no experimento. Após 24 horas eram relaparotomizados, sofriam colotomia transversa total esquerda à 2,0 cm da reflexão peritoneal e anastomose em plano único, extra-mucoso. As aferições foram realizadas nop tereciro e sétimo dias de pós-operatório. Ressecava-se 4,0 cm do cólon esquerdo contendo a anastomose e media-se a pressão de ruptura. Realizou-se estudo histopatológico, empregando-se a coloração do Sirius-red e análise da concentração de colágeno através de método computadorizado. Verificou-se que a capacidade de suportar pressão aumentou com o tempo de evolução de forma semelhante nos dois grupos. A concentração de colágeno foi menor no grupo com peritonite no terceiro dia (p = 0,000168) e no sétimo dia (p = 0,0020). Os percentuais de colágeno I e III foram semelhantes no terceiro dia. Já no sétimo dia, no grupo peritonite predominou o colágeno tipo III ( p = 0,000079). Os resultados analisados demonstram que existe diminuição da concentração e da maturação do colágeno nas anastomoses colo-cólicas realizadas quando existe peritonite porém esta alteração não interfere na capacidade da anastomose suportar pressão.

Keratinocyte growth factor promotes healing of left-sided colon anastomoses

BACKGROUND

Inadequate healing and consequent leakage from bowel anastomoses are a significant cause of postoperative morbidity and mortality. Systemic application of keratinocyte growth factor (KGF) has been shown to promote mucosal healing in models of colitis in rats and mice. The aim of the present study was to evaluate the effect of systemic KGF administration on healing of colonic anastomoses in rats.

METHODS

Rats underwent laparotomy, division of the left colon, and sigmoido-sigmoidostomy. KGF (5 mg/kg) or vehicle were administered intraperitoneally in two groups (n = 30 per group) 12 hours prior to surgery, and then once daily until sacrifice (6 animals per group; 2, 4, 7, 12, and 21 days after surgery). Bursting pressure measurements, histologic evaluation, morphometric analysis, mucin and collagen staining, and hydroxyproline measurements of the anastomotic site were performed.

RESULTS

Administration of KGF significantly increased anastomotic bursting pressure on postoperative days 2, 4, and 7 by 34%, 49%, and 19%, respectively. Histology, mucin staining, and measurements of the colonic crypt depth showed markedly less extended inflammation with an increased acidic mucin content and a significantly thickened mucosal layer in the KGF treated group when compared with vehicle-treated animals.

CONCLUSIONS

KGF promotes healing of colonic anastomoses in rats during a 1-week postoperative period following large bowel surgery. KGF may be acting to accelerate host reparative processes as well as to enhance protection of the anastomotic wound bed by increased colonic epithelium proliferation, increased mucus production, and reduction of the inflammatory activity at the anastomotic site.

The influence of intestinal flora on wound healing in mice

The wound healing process was analyzed using male ICR germ-free (Gf) mice and their conventionalized (Cvz) counterparts to determine whether intestinal flora has any influence on the wound healing of a host. A longitudinal skin incision of about 35 mm was made in the dorsum of each mouse, and six interrupted sutures with 5-0 monofilament nylon thread laid for wound closure. Mice from both groups were killed on the 3rd, 7th, and 14th postoperative days, and the tensile strength of the healing wound and hydroxyproline (HP) concentration in the biologically active zone were measured as parameters of wound healing. The daily nitrogen balance and urinary creatinine excretion were also measured for 8 days. The Cvz mice showed greater tensile strength of the wound on the 3rd and 7th postoperative days, and a higher ratio of HP concentration, being wound tissue/control tissue, than their counterparts. The Cvz mice also thrived more prominently than the Gf mice, showing a positive nitrogen balance with limited urinary creatinine excretion. These results suggest the enhancing effect of normal intestinal flora on wound healing, probably through the beneficial nutritional effects supplied by the bacteria.

Timing and method of reversal of Hartmann's procedure

The outcome of 145 patients undergoing Hartmann's resection between 1973 and 1989 has been reviewed. The mortality rate of the primary procedure was 8 per cent. Eighty patients proceeded to reanastomosis. Multifactorial analysis of these patients was undertaken to determine the risk involved. The interval between the primary and secondary procedures was found to be the most important factor. Six of 12 patients had clinical evidence of a leak when this interval was < 3 months, compared with seven of 28 for 3-6 months, and none of 40 when the second operation was delayed for > 6 months. All deaths (three patients) and clinical septicaemia (four) occurred in the two 'early' groups. All colovaginal fistulae (three patients) and strictures (three) were associated with stapled anastomoses. No association was found between the complication rate following reanastomosis and the initial pathology or grade of surgeon undertaking the secondary operation.

Effect of antibiotics in fibrin sealant on healing colonic anastomoses in the rat

In 90 rats a colonic anastomosis was constructed with 12 interrupted 7/0 polypropylene sutures. Group 1 (n = 30) served as a control group. In group 2 (n = 30) the anastomosis was sealed with fibrin adhesive and in group 3 (n = 30) a mixture of fibrin, clindamycin and cefotaxime was used. On days 2, 4 and 7, ten animals in each group were killed. Adhesion formation was significantly increased in groups 2 and 3 compared with the control group. On day 2 the anastomosis was significantly stronger after sealing with antibiotic-fibrin mixture. On day 4 the bursting pressure in group 2 was significantly lower than in groups 1 and 3. At the same time the concentration of hydroxyproline was significantly reduced in group 2, but not in group 3. The addition of antibiotics prevents the negative effect of fibrin adhesive on the healing colonic anastomosis and contributes to a stronger anastomosis on day 2 after operation.

The influence of NSAIDs on experimental intestinal anastomoses

Limiting degradation of collagen during the initial phase of wound healing is expected to improve postoperative intestinal strength and thereby decrease chances for anastomotic dehiscence. We studied the influence of four nonsteroid anti-inflammatory drugs on the healing of intestinal anastomoses in rats, with special regard to changes of collagen levels around the anastomoses. Four experimental groups of 20 rats each received daily oral doses of piroxicam, ibuprofen, aspirin, or indomethacin and were compared with a control group. Animals were sacrificed 3 or 7 days after operation. Both morbidity and mortality rate in the experimental groups were high. Collagen, measured as hydroxyproline, levels in anastomotic and adjoining 1-cm intestinal segments were compared with concentrations in control segments resected during operation. After an initial decrease on day 3, hydroxyproline concentrations increased on day 7. In the colon the lowering of hydroxyproline concentrations, which was more pronounced than in the ileum, was significantly reduced by administration of piroxicam and ibuprofen, both in the anastomosis and its proximal segment. On day 7, the increase of hydroxyproline concentrations in the ileum was inhibited by administration of anti-inflammatory drugs. It is concluded that nonsteroidal anti-inflammatory drugs may limit postoperative degradation of collagen in colonic anastomoses, but at the same time may increase the rat's susceptibility to surgical infections.

Effect of fibrin sealant on the healing colonic anastomosis in the rat

Fibrin adhesives have been advocated as a protective seal in colonic anastomosis to prevent leakage. In order to assess the effect of fibrin glue sealing we compared the healing of sutured colonic anastomosis in the rat (group 1) with the addition of human-derived fibrin sealant (group 2). As a control for a possible reaction to foreign protein, in group 3 the sutured anastomosis was sealed with specially prepared rat fibrin adhesive. On days 2, 4 and 7, ten animals in each group were killed. Adhesion formation was scored and the in situ bursting pressure was measured. The collagen concentration and degradation were estimated by measuring hydroxyproline. Adhesion formation was significantly increased in groups 2 and 3 compared with the control group. On days 2 and 7 the bursting pressure was not different between the groups. On day 4 the bursting pressure in groups 2 and 3 was significantly lower than in group 1 (P less than 0.001). These findings correspond with the results of collagen measurements. On day 4 the concentration of hydroxyproline was significantly reduced in groups 2 and 3. Histological examination showed infiltration of neutrophilic granulocytes into the sealant on days 2 and 4; on day 7 the sealant had vanished. From these results it is concluded that fibrin sealing of the colonic anastomosis in the rat does not improve healing, as demonstrated by bursting pressure and hydroxyproline concentration. On the contrary, it seems to have a negative influence.

Healing of experimental intestinal anastomoses. Parameters for repair

Anastomotic dehiscence remains a major complication in surgery of the large bowel, and studies on the healing sequence of experimental anastomoses are necessary to define underlying mechanisms and find ways to improve surgical outcome, particularly in high-risk situations. For the quantitative description of anastomotic repair, both mechanical and biochemical parameters are employed, each with their own limitations. Mechanical parameters, either bursting pressure or breaking strength, only reflect growing anastomotic strength as long as disruption occurs within the anastomotic area, which is less than one week after surgery for the bursting pressure and probably up to two weeks for the breaking strength. The biochemical description of anastomotic repair has been limited to behavior of collagen, as represented by its rather unique constituent amino acid hydroxyproline. Conclusions based on collagen concentrations--per unit weight--should be considered with caution since they may change as a consequence of changes in noncollagenous substances. In this respect, collagen content, per unit length, is probably a better parameter to describe anastomotic collagen levels. Few investigations have addressed the quality of collagen (e.g., crosslinking or type). Since, at this time, no distinct correlations have been demonstrated between development of mechanical strength or occurrence of leakage and collagen levels in the healing anastomosis, attention should not be restricted to a description of the quantity of collagen present: the quality of anastomotic collagen should be investigated, perhaps even more so.