Collagenolytic activity in experimental intestinal anastomoses. Differences between small and large bowel and evidence for the presence of collagenase

The Colorectal Anastomosis: A Timeless Challenge

Colorectal anastomosis is a sophisticated problem that demands an elaborate discussion and an elegant solution. "Those who forget the past are condemned to repeat it." George Santayana, Life of Reason , 1905.

Initial Assessment of Mucosal Capture and Leak Pressure After Gastrointestinal Stapling in a Porcine Model

BACKGROUND

Anastomotic leak is a leading cause of morbidity and mortality in gastrointestinal surgery. The serosal aspect of staple lines is commonly observed for integrity, but the mucosal surface and state of mucosa after firing is less often inspected. We sought to assess the degree of mucosal capture when using stapling devices and determine whether incomplete capture influences staple line integrity.

METHODS

Porcine ileum was transected in vivo and staple lines were collected and rated for degree of mucosal capture on a 5-point scale from 1 (mucosa mainly captured on both sides) to 5 (majority of mucosa not captured). Mucosal capture was also assessed in ex vivo staple lines, and fluid leakage pressure and location of first leak was assessed. Stapling devices studied were Echelon Flex GST with 60-mm blue (GST60B) and green (GST60G) cartridges, and Medtronic EndoGIA Universal with Tri-Staple Technology™ with 60 mm medium (EGIA60AMT) reloads (purple).

RESULTS

GST60B and GST60G staple lines produced significantly better mucosal capture scores than the EGIA60AMT staple lines (p < 0.001, in all tests). Compared to EGIA60AMT, leak pressures were 39% higher for GST60B (p < 0.001) and 23% higher for GST60G (p = 0.022). Initial staple line leak site was associated with incomplete mucosal capture 78% of the time.

CONCLUSIONS

There are differences in degree of mucosal capture between commercial staplers, and the devices that produce better mucosal capture had significantly higher leak pressures. Further research is needed to determine the significance of these findings on staple line healing throughout the postoperative period.

Effect of Postoperative Diclofenac on Anastomotic Strength and Histologic Healing in Rabbit Small Intestine

In this experimental study, we investigated the effects of a 5-day postoperative treatment with the nonsteroidal anti-inflammatory drug (NSAID) diclofenac on anastomotic healing in rabbits. NSAIDs are widely used analgesics in today's “fast-track surgery,” raising concerns about their potential negative effects on healing in humans. A total of 33 New Zealand White female rabbits underwent laparotomy and 2 separate end-to-end anastomoses of the ileum.. The animals were randomized to receive subcutaneous diclofenac 4 mg/kg/d (17 experimental rabbits) or subcutaneous isotonic saline 0.1 mL/kg/d (16 control rabbits) postoperatively. On the fifth postoperative day, the animals were humanely killed, and anastomotic leakage, anastomotic breaking strength, and histopathologic changes were evaluated. Breaking strength in the diclofenac group was 21% lower than in the placebo group (P = 0.027). Anastomotic leakage was found in 4 rabbits in the diclofenac group (26.7%). The rabbits treated with diclofenac demonstrated a 16% lower collagen deposition compared with the placebo group (P = 0.008). In our study, postoperative treatment with diclofenac had a negative effect on the anastomotic healing and strength in the ileum of rabbits. Caution should be taken in the use of diclofenac after gastrointestinal surgery.

Expression and inhibition of matrix metalloproteinase (MMP)-8, MMP-9 and MMP-12 in early colonic anastomotic repair

PURPOSE

Submucosal collagen is paramount for colonic anastomotic integrity. Matrix metalloproteinases (MMPs) mediate collagen degradation that increases the risk of wound dehiscence. Although broad-spectrum MMP inhibitors are beneficial for anastomotic strength, they can cause adverse reactions. Knowledge of specific MMPs responsible for the weakening of anastomoses can be used to optimise MMP inhibition therapy. We aimed to quantify transcript and protein levels of multiple MMPs in colonic anastomoses and evaluate the effect of inhibiting the MMPs that displayed the highest expression levels on anastomotic repair.

METHODS

Left-sided colonic anastomoses were made in male Sprague-Dawley rats. After 3 days when biomechanical strength is lowest, MMP mRNA and protein levels were measured by quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assays and gelatin zymography. The effects of the MMP-8, MMP-9 and MMP-12 synthetic inhibitor AZD3342 was also studied.

RESULTS

MMP-8, MMP-9 and MMP-12 gene and protein expression increased profoundly (p < 0.01), and MMP-13 mRNA and MMP-2 mRNA and protein modestly (p < 0.001) in the anastomoses. MMP-3 mRNA levels were not up-regulated significantly compared with adjacent uninjured colon. Increased anastomotic MMP-12 levels paralleled macrophage infiltration by immunohistochemical analyses. AZD3342 (50 mg/kg) treatment increased the anastomotic breaking strength by 29% (p = 0.015) day 3 compared with vehicle. Improved anastomotic strength was not accompanied with alterations of type I or type III procollagen mRNA but was possibly due to inhibition of the concerted digestive action on the existent submucosal collagens by the targeted MMPs.

CONCLUSION

The present findings justify the concept of selective MMP inhibition to enhance anastomotic strength in colon.

Influence of Pneumoperitoneum on Small Bowel Anastomoses: A Histological Analysis in the Rat Model

Laparoscopic techniques are increasingly applied for the treatment of diverse gastrointestinal diseases. With regard to reports of a pronounced decrease of intra-abdominal blood flow with increasing intra-abdominal pressure, the present study investigates the impact of pressure and gas type on ischemia in small bowel anastomoses in the rat model. Laparotomy and ileoileal anastomosis were performed in 39 male Sprague-Dawley rats. A CO2 or helium pneumoperitoneum of 3 mm Hg or of 6 mm Hg was maintained before and after anastomoses. Rats in the control group received no pneumoperitoneum. Animals were sacrificed after 5 d, and the anastomotic region was explanted for subsequent histopathological examinations. In hematoxylin and eosin (HE)-stained sections, the Chiu score, villi configuration, and number of goblet cells were analyzed. Proliferation (Ki67) and expression of a matrix metalloproteinase (MMP-8) were examined by immunohistochemistry. Mucosal damage according to the scoring system by Chiu, the number of goblet cells, the villus length, the proliferation (Ki67), and the submucosal expression of MMP-8 was similar in all groups. Our results suggest that within a certain range of pressures and time, laparoscopic assisted surgery using CO2 pneumoperitoneum can be performed safely. Helium gas offers no advantages over CO2.

Comparison of biofragmentable anastomosis ring and sutured anastomoses for subtotal colectomy in cats with idiopathic megacolon

OBJECTIVE

To report use of a biofragmentable anastomosis ring (BAR) device in cats with idiopathic megacolon (FIM) and compare outcome after subtotal colectomy with sutured colocolic anastomosis.

STUDY DESIGN

Retrospective study.

ANIMALS

Nineteen cats with megacolon.

METHODS

Medical records (January 1990-January 2004) of cats treated surgically for idiopathic megacolon with sutured (SUT) or BAR anastomosis were retrieved and reviewed. Operative, short- and long-term complications, and survival times were recorded and Kaplan-Meier survival analysis used to assess outcome.

RESULTS

There were 11 SUT and 8 BAR cats. One BAR cat had anastomotic dehiscence 36 hours after surgery. Mild serosal tearing during BAR insertion in 6 cats was corrected by suture reinforcement. One SUT cat developed anastomotic stricture at 32 days. Short-term complication rates at 3 and 7 days were 18% and 45% in the SUT group and 25% and 87.5% in the BAR group, respectively (P=.058). Two SUT cats had persistent loose stool consistency and were euthanatized 254 and 1661 days after surgery. One BAR cat had recurrence of constipation which was managed medically. Long-term complication rates were not significantly different between SUT and BAR (P=.61). The 1 and 4-year survival rates were 90% for SUT and 100% for BAR (P=.29).

CONCLUSIONS

No difference was detected for short and long-term complication rates and survival times between SUT and BAR groups.

CLINICAL RELEVANCE

The BAR device can be used for colocolic anastomosis in cats with idiopathic megacolon. Serosal tearing during BAR insertion was a common intraoperative complication. Regardless of anastomotic technique, survival outcome after colonic resection is excellent for cats with FIM.

Action of matrix metalloproteinases at restricted sites in colon anastomosis repair: an immunohistochemical and biochemical study

BACKGROUND

Dehiscence of colon anastomosis is a common, serious and potentially life-threatening complication after colorectal operation. In experimental models, impaired biomechanic strength of colon anastomoses is preventable by general inhibitors of matrix metalloproteinases (MMPs) and associated with collagen loss, which indicates a possible link between MMP-mediated collagen degradation and dehiscence. The precise localization of collagen degradation within the anastomotic area and the specific MMPs responsible are unknown.

METHODS

We have analyzed distinct zones within anastomoses using a novel microdissection technique for collagen levels, collagenolytic activity exerted directly by endogenous proteinases, and MMP-8 and MMP-9 immunoreactivity and their collagenolytic activity.

RESULTS

The most pronounced collagen loss was observed in the suture-holding zone, showing a 29% drop compared with adjacent micro-areas of 3-day-old anastomoses. Only this specific tissue compartment underwent a dramatic and significant increase in collagenolysis, amounting to a loss of 10% of existing collagen molecules in 24 hours, and was abolished by metalloproteinase inhibitors. The tissue surrounding suture channels was heavily infiltrated with CD68-positive histiocytes that expressed MMP-8 and to a lesser extent MMP-9. The collagenolytic effect of the interstitial collagenase MMP-8 was synergistically potentiated by the gelatinase MMP-9 when added to colon biopsies incubated in vitro.

CONCLUSIONS

The unique finding of this study was that the specific tissue holding the sutures of a colon anastomosis lost the most collagen presumably through induction and activation of multiple MMPs that may explain the beneficial effects of treatment with non-selective MMP antagonists.

Effects of soluble fiber on matrix metalloproteinase-2 activity and healing of colon anastomosis in rats given radiotherapy

BACKGROUND AND AIMS

Soluble fiber is fermented by colonic microflora yielding short-chain fatty acids (SCFAs) in the colon. We aimed to investigate the effect of oral administration of soluble fiber on healing of anastomosis and matrix metalloproteinase-2 activity in radiotherapy received colonic anastomosis.

METHOD

Eighty-four Wistar rats were divided into six groups. All rats were performed a left colonic resection with end-to-end anastomosis. Group I received rat cow. Group II received soluble fiber orally for five consecutive days preoperatively as well as 3rd and 6th days postoperatively. Group III received SCFAs via rectum for five consecutive days preoperatively. Group IV received irradiation to the pelvis at a total dose of 24 Gy on the 10th and 5th days before the operation. Group V was exposed to irradiation like the rats in Group IV and oral treatment like the rats in Group II. Group VI received irradiation like the rats in Group IV and transrectal treatment like the rats in Group III. On the 3rd and 7th postoperative days, all the rats were anesthetized to evaluate the anastomosis healing clinically, histologically and biochemically.

RESULTS

Third and 7th day bursting pressures of the rats that were fed with a normal diet and exposed to radiotherapy were significantly decreased (P<0.001). Bursting pressures of Groups V and VI on the 7th day were significantly higher than the control group's bursting pressures (P<0.05). Hydroxyproline levels of Group IV were significantly decreased (P<0.001). Following oral soluble fiber and transrectal administration of SCFAs, these low levels reached to the levels of control radiotherapy group. Matrix metalloproteinase-2 activity of all the rats that were exposed to radiotherapy was higher than the control group (P<0.001). Matrix metalloproteinase-2 enzyme levels in the Groups V and VI were lower than the ones in the Group IV (P<0.001). The histologic parameters of anastomotic healing such as epithelial regeneration, exudate, necrosis, and fibroblast levels were significantly improved by the use of oral soluble fiber and transrectal SCFAs treatment.

CONCLUSION

Undesirable effects of preoperative radiotherapy on mechanical, histological and biochemical parameters can be overcome by oral soluble fiber. Oral soluble fiber administration has similar positive effects like the transrectal administration of the SCFA's.

Colonic anastomotic strength and matrix metalloproteinase activity in an experimental model of bacterial peritonitis

BACKGROUND

Clinical studies report conflicting results on the safety of primary intestinal anastomoses in the presence of peritonitis, and comprehensive experimental data are lacking. The present study investigated whether the strength of experimental colonic anastomoses is affected if surgery is performed in the presence of pre-existing bacterial peritonitis.

METHODS

Colonic anastomoses were constructed in Wistar rats 24 h after caecal ligation and puncture or a sham procedure. Anastomotic strength was assessed by measuring breaking strength and bursting pressure during the first 5 days after operation. Anastomotic hydroxyproline levels were measured and matrix metalloproteinase (MMP) activity was analysed by quantitative gelatin zymography.

RESULTS

Anastomotic strength was lowered in the presence of bacterial peritonitis but in a minor and transient way. The breaking strength was lower only immediately after construction of the anastomosis (- 15 per cent, P = 0.011) and the bursting pressure only on the third postoperative day (- 33 per cent, P = 0.038); no anastomotic dehiscence was observed. At 3 days after operation increased levels of MMP activity were observed but anastomotic hydroxyproline content was not affected by bacterial peritonitis.

CONCLUSION

The influence of bacterial peritonitis on the development of anastomotic strength is limited. This experimental finding lends support to recent clinical studies that have demonstrated the feasibility of constructing a primary anastomosis under these conditions.

Doxycycline improves wound strength after intestinal anastomosis in the rat

BACKGROUND

The strength of intestinal anastomoses is relatively low in the first days after operation, possibly as a result of localized degradation of the supporting matrix by enzymes from the matrix metalloproteinase (MMP) family. The aim of this study was to examine whether doxycycline, a drug known to inhibit MMP activity, could enhance anastomotic strength.

METHODS

Male Wistar rats received anastomoses in both ileum and colon. From the day before operation onwards, animals were treated daily with doxycycline (orally or subcutaneously) in a dose of 10 mg/day or with saline only. Rats were killed 1, 3, or 5 days after operation, and anastomotic bursting pressure and breaking strength were measured. At day 3, anastomotic hydroxyproline levels were measured, MMP (gelatinase) activity was analyzed by gelatin zymography, and anastomotic histology was examined.

RESULTS

Doxycycline enhanced wound strength, but only at day 3, when it was at its lowest. Subcutaneous administration of 10 mg/day increased median colonic and ileal breaking strength by 27% (P =.0019) and 104% (P =.0376), respectively. Colonic bursting pressure was increased by 93% (P =.0002). Wound histology was similar in experimental and control groups.

CONCLUSIONS

Administration of doxycycline enhances anastomotic strength and should be investigated further as a means to preserve anastomotic integrity.

Inhibition of matrix metalloproteinases enhances breaking strength of colonic anastomoses in an experimental model

BACKGROUND

The breaking strength of colonic anastomoses declines after operation to a minimum at days 3-4, with a subsequent risk of anastomotic dehiscence. The mechanism is thought to be collagen degradation by matrix metalloproteinases (MMPs). This study examined the pathogenic role of MMPs on the mechanical strength of colonic anastomoses by giving the synthetic broad-spectrum MMP inhibitor BB-1101 systemically.

METHODS

Forty-eight male Sprague-Dawley rats were treated daily for 7 days with BB-1101 30 mg/kg or vehicle alone (control) starting 2 days before operation. The breaking strength of standardized left-sided colonic anastomoses was measured on postoperative days 1, 3 and 7.

RESULTS

Serum BB-1101 levels were increased at 100 nmol/l in BB-1101-treated rats. The anastomotic breaking strength was 48 per cent higher (P = 0.02) in BB-1101-treated animals compared with controls on postoperative day 3. Neither collagen accumulation nor infiltration of neutrophils in the anastomotic area was influenced by BB-1101 treatment. Net deposition of new collagen in subcutaneous sponges was unaffected by the BB-1101.

CONCLUSION

The enhanced breaking strength of colonic anastomoses during the critical early postoperative phase found after administration of a broad-spectrum MMP inhibitor implies that MMPs might increase the risk of anastomotic dehiscence. Presented in part to the third joint meeting of the European Tissue Repair Society and the Wound Healing Society in Bordeaux, France, 24-28 August 1999, and published in abstract form in Wound Repair Regen 1999; 7: A321

Quantitation of angiogenesis in healing anastomoses of the rat colon

An accurate and reliable quantitation of angiogenesis is an essential requirement for a detailed study of new blood vessel growth during healing of colon anastomoses. In the present study we applied a computer-based digital image processing system for quantitative analysis of the anastomotic vascularization and perfusion. Rats underwent colonic resection (1 cm) followed by construction of an end-to-end anastomosis. The animals were killed 3 or 7 days after operation. The vascularization and perfusion were analysed in cyrostat sections using an anti-collagen type IV antibody and the fluorescent marker bisbenzimide H 33342, respectively. If compared with 3-day-old anastomoses, a significant increase in the median vascular and perfusion areas was found 7 days after operation. Within the same anastomosis, the vessel density and perfusion were lower in the central region than in the peripheral region of the wound. The present computerized digital image analysis system is a reliable technique that is suited for quantitative measurements of microvascular changes occurring in colon anastomoses during the first postoperative week.

Divergent patterns of matrix metalloproteinase activity during wound healing in ileum and colon of rats

BACKGROUND

Uncontrolled and increased extracellular matrix degradation during early anastomotic repair in the intestine may reduce wound strength increasing the risk of anastomotic dehiscence.

AIMS

To characterise the metalloproteinases present in intact and anastomosed ileum and colon to study their role in matrix degradation after surgery.

SUBJECTS

Tissue extracts of uninjured, and of anastomosed rat ileum and colon at postoperative days 1, 2, 3, 7, and 90, were used.

METHODS

Metalloproteinases were identified by gelatin and casein zymography. Aminophenylmercuric acetate (APMA) treatment was used to activate latent metalloproteinases.

RESULTS

Both uninjured ileum and colon contained a 60 and 67 kDa activity, but a 54 and 72 kDa gelatinase was present in ileum only, and a 51 kDa activity in colon only. APMA treatment converted the 60 kDa protease to 54 and 51 kDa forms and the 72 kDa protease to the 67 kDa form. These gelatinases may correspond to latent and active forms of MMP 1 and MMP 2, respectively. Additional metalloproteinases were observed after anastomotic construction. Both ileum and colon contained 95 and 230 kDa gelatinases, which were converted to 83 and 76 kDa forms by APMA. They may be the latent and active forms of MMP 9, respectively. Gelatinolytic activities of 25 and 28 kDa were only found in anastomosed ileum. Caseinolytic activities were only found in ileum extracts and those were most prominent at day 1, 2, and 3 after surgery.

CONCLUSIONS

The metalloproteinase pattern in ileum and colon differ considerably suggesting that matrix degradation after anastomotic construction may also vary.