Ischemia-reperfusion of the small intestine and hyperbaric oxygen treatment: a morphologic study in rats

Effect of hyperbaric oxygenation on random rat skin flaps vascularization

Purpose:

To evaluate the effect of hyperbaric oxygenation (HBO) on angiogenesis in random rat skin flaps, by immunoexpression of vascular endothelial growth factor A (VEGF-A).

Methods:

Forty adult rats were divided into four groups: GE) epilated; GE/HBO) epilated subjected to HBO; GER) epilated submitted to dorsal skin flap; GER/HBO) epilated subjected to dorsal skin flap + HBO. HBO was performed with rats inside a chamber under atmosphere close to 100% oxygen and pressure of 2.4 absolute atmospheres, 2h per day during seven consecutive days. GE and GER groups were placed in the hyperbaric chamber without HBO. Then, under anesthesia, skin flaps were removed and separated into three portions relative to pedicle fixation. The samples were fixed in formalin and processed for paraffin embedding. Histological sections were submitted to immunohistochemistry for VEGF-A detection. The number of immunostained-blood vessels were counted under light microscopy.

Results:

GE and GE/HBO groups showed normal and similar skin morphology in the three flap portions. A fibrin-leukocyte crust, along with denatured collagen and intense leukocyte infiltrate, was mainly observed in the dermis of the medial and distal flap portions of GER group. Meanwhile, the GER/HBO group presented more regions with intact collagen and small areas of leukocyte infiltrate in the three flap regions. VEGF-A-immunostained blood vessels were largely seen in all regions of GE and GE/HBO groups, whereas no significant differences were found between these groups. A decrease in vascularization was noticed in GER and GER/HBO groups, which was more evident in the most distal portion of the flaps. However, the number of VEGF-A-immunostained blood vessels in GER/HBO group was significantly higher when compared to GER group.

Conclusions:

Hyperbaric oxygenation was associated with increased angiogenesis and improved viability of rat skin flaps.

Hyperbaric Oxygen Increases Stem Cell Proliferation, Angiogenesis and Wound-Healing Ability of WJ-MSCs in Diabetic Mice

Hyperbaric oxygen therapy (HBOT) is effective for the medical treatment of diverse diseases, infections, and tissue injury. In fact, in recent years there is growing evidence on the beneficial effect of HBOT on non-healing ischemic wounds. However, there is still yet discussion on how this treatment could benefit from combination with regenerative medicine strategies. Here we analyzed the effects of HBOT on three specific aspects of tissue growth, maintenance, and regeneration: (i) modulation of adult rodent (Mus musculus) intestinal stem cell turnover rates; (ii) angiogenesis dynamics during the development of the chorio-allantoic membrane (CAM) in Gallus gallus embryos; (iii) and wound-healing in a spontaneous type II diabetic mouse model with a low capacity to regenerate skin. To analyze these aspects of tissue growth, maintenance, and regeneration, we used HBOT alone or in combination with cellular therapy. Specifically, Wharton Jelly Mesenchymal Stem cells (WJ-MSC) were embedded in a commercial collagen-scaffold. HBOT did not affect the metabolic rate of adult mice nor of chicken embryos. Notwithstanding, HBOT modified the proliferation rate of stem cells in the mice small intestinal crypts, increased angiogenesis in the CAM, and improved wound-healing and tissue repair in diabetic mice. Moreover, our study demonstrates that combining stem cell therapy and HBOT has a collaborative effect on wound-healing. In summary, our data underscore the importance of oxygen tension as a regulator of stem cell biology and support the potential use of oxygenation in clinical treatments.

Effect of different periods of hyperbaric oxygen on ischemia-reperfusion injury of rat small bowel

PURPOSE

To determine whether hyperbaric oxygen (HBO) could effectively protect the small intestine mucosa against an ischemic insult, according to different periods of application.

METHODS

The gut of 32 male rats was subjected to 60-min ischemia (clamping the mesenteric artery and vein); After they were further reperfused upon clamp opening during 60 min. Animal groups were as follows. GII = placed on HBO during the ischemia period; GIII = placed on HBO during reperfusion; GIV = treated with HBO throughout the ischemia-reperfusion period. Some animals (GI) did not receive HBO treatment at all and served as reference of ischemia-reperfusion injury (IR). HBO was carried out in a cylindrical acrylic chamber (2.0 ATA). Samples of small bowel were prepared for H.E staining for histological evaluations.

RESULTS

The histological injury of mucosa was significantly less when HBO was administered during the ischemia period (17.6 +/- 0.6) as compared with the IR (21.3 +/- 1.8). HBO was not effective when applied during reperfusion (23.1 +/- 2.1) or during the ischemia plus reperfusion period (18.7 +/- 1.9). The thickness of the mucosa was preserved by HBO in ischemia (327.50 +/- 30.23 microm) in comparison with the IR (172.79 +/- 5.95 microm). In the periods of reperfusion (162.50 +/- 6.05 microm) and ischemia plus reperfusion (296.49 +/- 20.01 microm) the mucosa revealed a structural injury.

CONCLUSION

Hyperbaric oxygen affects the ischemic insult of small bowel, being the favorable effect obtained when hyperbaric oxygen was administered early in the ischemic period.

A proposal of multiplace hyperbaric chamber for animal experimentation and veterinary use

PURPOSE: To develop a project of hyperbaric chamber that allows its safe and reliable use in veterinary and animal experimentation. METHODS: Based on the technical specifications for the construction of hyperbaric chambers for human beings, it has been developed a design of a chamber with dimensions and characteristics for the use of a midsize animal, (dog or pig), as well as a multiple chamber for the use in small animals (mice, rats, hamsters, rabbits or cats). The technical specifications allowed that the chamber could be used both for veterinary use and for use in experiments on Health Sciences. RESULTS: A chamber with the following characteristics was built: ASTM A36 steel for the manufacture of the master cylinder and rear cover; front door built in 5052 aluminum; internal diameter of 50.5 cm and 83.0 cm in length; weight 160Kg and internal area of 150cm³; internal space to accommodate 2 acrylic baskets; 150mm high, 280mm wide and 690mm in length. It was capable of supporting a maximum of hydrostatic pressure test of 3.0 to 4.0 BAR ACT and maximum working pressure of 2.0 BAR or 3.0 ACT; equipped with security devices and valves that triggers with load of 2.2 BAR or 3.2 ACT. Tests for engineering and biological use on animals showed the effectiveness of the device. CONCLUSION: The development of the project enabled the construction of a hyperbaric chamber with security features and reliability comparable to those required by the legal and technical specifications of a hyperbaric chamber human use.

Strategies for improving the outcomes of small-for-size grafts in adult-to-adult living-donor liver transplantation

Living-donor liver transplantation (LDLT) has been refined and accepted as a valuable treatment for patients with end-stage liver disease in order to overcome the shortage of organs and mortality on the waiting list. However, graft size problems, especially small-for-size (SFS) grafts, remain the greatest limiting factor for the expansion of LDLT, especially in adult-to-adult transplantation. Various attempts have been made to overcome the problems regarding SFS grafts, such as increasing the graft liver volume and/or controlling excessive portal inflow to a small graft, with considerable positive outcomes. Recent innovations in basic studies have also contributed to the treatment of SFS syndrome. Herein, we review the literature and assess our current knowledge of the pathogenesis and treatment strategies for the use of SFS grafts in adult-to-adult LDLT.

Hyperbaric Oxygen Therapy Attenuates Renal Ischemia/Reperfusion Injury in Rats

OBJECTIVE

Renal ischemia/reperfusion (I/R) injury occurs in both native and transplanted kidneys. Hyperbaric oxygen (HBO) has been shown to prevent I/R injury in different tissues. The aim of this study was to evaluate the effect of HBO on renal I/R injury in rats.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly assigned to one of three groups. The Control group (n = 6) received right nephrectomy. The I/R (n = 6) and I/R+HBO groups (n = 6) received 30 min left renal ischemia followed by 24 h of reperfusion after right nephrectomy. The I/R+HBO group (n = 6) received additional HBO therapy for 60 min at 2.5 absolute atmospheres starting at the initial 15th minute of reperfusion.

RESULTS

In the I/R group, blood urea nitrogen (BUN) and creatinine levels increased significantly compared with the Control and I/R+HBO groups (p < 0.05). BUN and creatinine levels were similar in the Control and I/R+HBO groups. Kidney samples from I/R group rats revealed severe tubular damage and neutrophil infiltration at histopathological examination. The animals treated with HBO showed markedly improved lesions and less neutrophil infiltration compared with the I/R group (p < 0.05).

CONCLUSIONS

HBO exhibited marked protection against I/R injury in this study as measured using BUN and creatinine levels and renal histopathology. However, further studies are needed to clarify the renoprotective effect of HBO on I/R injury.

Preoperative and postoperative administration of hyperbaric oxygen improves biochemical and mechanical parameters on ischemic and normal colonic anastomoses

Colonic anastomotic leaks are a major postoperative complication, causing increased mortality and morbidity. Tissue ischemia is one of the most important factors that disrupt anastomotic healing. It is possible to reverse inadequate tissue oxygenation by using increased atmospheric pressure and hyperoxia, which are obtained from hyperbaric oxygen treatment (HBO). Our aim was to investigate the effects of preoperative and postoperative HBO treatment on normal and ischemic colonic anastomoses in rats. Eighty male Wistar Albino rats, weighing between 180 and 240 g, were divided into 8 equal groups. A 1-cm segment of left colon was resected 3 cm proximal to the peritoneal reflection in all groups and colonic anastomosis was performed. In groups 2, 4, 6 and 8, colonic ischemia was established by ligating 2 cm of mesocolon on either side of the anastomosis. Control groups (1 and 2) received no HBO. HBO treatment was given preoperatively in groups 3 and 4, postoperatively in groups 5 and 6, and both preoperatively and postoperatively in groups 7 and 8. HBO treatment was applied for 2 days in the preoperative period and 4 days in the postoperative period. Relaparotomy was performed on postoperative day 5 and a perianastomotic colon segment 2 cm in length was excised for detection of biochemical and mechanical parameters of anastomotic healing and histopathological evaluation. HBO treatment increased tissue hydroxyproline levels in all groups, and this difference was significant in normal anastomosis groups receiving preoperative HBO compared to controls (p = .013 for group 1 vs. group 3; p = .023 for group 1 vs. group 5). This improvement was more evident in ischemic and normal groups treated by administration of combined pre- and postoperative HBO (p = .021 and p = .013). HBO treatment also increased the mean bursting pressure values in all groups, and again, a statistically significant increase was noted in the ischemic groups compared to controls (p = .002 for group 2 vs. group 6; p = .001 for group 2 vs. group 8). Histopathological evaluation of anastomotic line fibrosis was not found to show significant differences between the groups. Adequate tissue oxygenation is the main factor in wound and anastomosis healing. HBO treatment has a positive effect on biochemical and mechanical parameters of ischemic and normal colon anastomoses in rats. It is possible to see this effect more clearly with combined HBO treatment applied before and after ischemic anastomosis.

Use of Hyperbaric Oxygenation in Small Bowel Preservation for Transplant

INTRODUCTION

The aim of this work was to study the effects of hyperbaric oxygenation as a preservation technique for small bowel transplantation.

METHODS

Twenty 2-month-old male Wistar rats weighting 250 g were divided into two groups: group A (n = 10) in which the small bowel was preserved for 12 hours, and group B (n = 10) in which the small bowel was preserved for 24 hours. After vascular and intraluminal perfusion, 3-cm segments were maintained in Ringer's solution at temperatures between 2 degrees C to 4 degrees C and in normobaric O2 conditions (groups A1, B1) or conditioned in an hyperbaric O2 metal chamber (100% oxygen at 5.5 absolute atmospheres) (groups A2, B2). After this preservation time, we studied intestinal tissue injury and morphometric analysis of the villi.

RESULTS

Mucosal injury was significantly greater among group A1 compared to group A2 animals. The grade of the lesions was greater among group B1 compared to group B2 animals. Group A1 showed no difference from Group B1. For lesion grade, the range was smaller in group A2 and group B2 animals. The villi height was significantly smaller in groups A1 and B1 compared to the other groups; whereas it was higher in group A2 as compared with B2.

CONCLUSION

Hyperbaric oxygenation may play a role as a preservation technique. Further research is necessary.

Therapeutic Effect of Hyperbaric Oxygen in Hepatic Artery Thrombosis and Functional Cholestasis After Orthotopic Liver Transplantation

Among the postoperative complications, hepatic artery thrombosis can occur in up to 10% of adult orthotopic liver transplants and intervention is indicated when this occurs within 30 days by retransplantation. Primary graft dysfunction, which can occur in up to 30% of the cases and is another potential complication, although reversible, has a relatively high mortality rate. Hyperbaric therapy, an efficient mode of tissue oxygenation, is being used in an increasing number of clinical situations. We report here two cases where hyperbaric oxygen therapy greatly benefited patients with complications after orthotopic liver transplantation: one with hepatic artery thrombosis and the other with primary graft dysfunction. Both patients showed rapid clinical recovery with gradual reduction of liver and canalicular enzymes soon after commencing hyperbaric oxygen therapy.

A Novel System for Organ and Tissues Preservation: The Refrigerating Hyperbaric Chamber

This study was designed to investigate the feasibility of building a simple and inexpensive device to preserve organs or tissues in hyperbaric and hypothermic conditions.

METHODS

The device was built on a 40-cm wide, 28-cm long, and 23-cm deep stainless steel chassis. The pressure vessel was built by a 7.8-cm bore stainless steel cylinder put inside another 12-cm cylinder welded together and closed by a steel plate on the top and bottom. The inferior plate was welded, and the superior one was fixed by manual clasp nut. The cooling system is made up of air compressor, condenser, expansion area, and cooling worm that is located between the cylinders. The temperature-controlling device is a computer processor contained in an integrated-circuit chip, with a on-off system to maintain the chamber temperature between 2 degrees to 4 degrees C. The compression of the chamber is performed by lateral coupling with the oxygen cylinder and is maintained at 5.5 absolute atmospheres and controlled by air pressure gauge. The maximal work pressure was evaluated by spreadsheet. Temperature or pressure changes were evaluated by 12- and 24-hour assays.

RESULTS

The maximal work pressure permitted was 6.5 absolute atmospheres. Thus, the container was free from danger. The temperature inside the chamber was kept between 2 degrees and 4 degrees C. The production costs of the prototype was US$1000.

DISCUSSION

The manufacture of the refrigerating hyperbaric chamber is viable, simple, and inexpensive.

Apoptosis and Nuclear Proliferation in Rat Small Bowel Submitted to Hypothermic Hyperbaric Oxygenation for Preservation

This study was conducted to assess apoptosis and nuclear proliferation in rat small bowel submitted to hypothermic hyperbaric oxygenation for preservation.

METHODS

Twenty two-month-old, male Wistar rats, weighing 250 g were divided into two groups: group I (n = 10), in which the small bowel was preserved for 12 hours, and group II (n = 10) in which the small bowel was preserved for 24 hours. After vascular and intraluminal perfusion, 3-cm segments were maintained in Ringer's solution at 2 degrees to 4 degrees C under normobaric conditions (groups Ia and IIa) or conditioned in a small hyperbaric metal chamber with 100% oxygen at 5.5 absolute atmospheres (groups Ib and IIb). After 12 or 24 hours, apoptotic and mitotic indices were evaluated by immunohistochemical methods.

RESULTS

The apoptotic index was significantly higher in small bowel segments in groups Ia and IIa compared with groups Ib and IIb. The mitotic index was significantly higher among group IIb.

CONCLUSION

Hypothermic hyperbaric oxygenation reduced intestinal epithelial apoptosis and increased nuclear proliferation during rat small bowel preservation.

Protective effects of ischemic preconditioning on the intestinal mucosal microcirculation following ischemia-reperfusion of the intestine

OBJECTIVE

The small bowel villi are extremely sensitive to ischemia-reperfusion (IR) injury and a range of microcirculatory disturbances contribute to structural and functional changes. The aim of this study was to determine the protective effects of ischemic preconditioning (IPC) of the intestine on the mucosal villous microcirculation during IR injury of the intestine and whether heme oxygenase (HO) is involved in the protection.

METHODS

Rats were allocated into 4 groups: (1) sham, (2) IR consisting of 30 min of ischemia followed by 2 h of reperfusion, (3) IPC, as in IR group, but preceded by 10 min of ischemia and 10 min of reperfusion, and (4) with administration of zinc protoporphyrin, an HO inhibitor before IPC and IR. The mucosa of an exteriorized segment of ileum was visualized. Mucosal perfusion index (MPI), red blood cell (RBC) velocity and leukocyte-endothelial interactions during reperfusion were assessed continuously using in vivo fluorescence microscopy. HO activity in the ileum was assessed at the end of the reperfusion period.

RESULTS

IPC improved the MPI by 26% and the RBC velocity by 29% on comparison to IR. IR led to a 52% increase in leukocyte-endothelial interactions on comparison to IPC. The administration of zinc protoporphyrin reversed the beneficial effects of IPC. There was a two fold increase of HO activity in IPC compared to IR, whereas zinc protoporphyrin significantly reduced the HO activity.

CONCLUSIONS

IPC conferred a protective effect on the villous microcirculation possibly via HO and might prove to be an effective strategy for the amelioration of IR injury.

Oxigenoterapia hiperbárica em lesões actínicas de colo de ratos: aspectos morfológicos e morfométricos

Objetivo: Avaliar a ação da oxigenação hiperbárica em lesões actínicas provocadas por radiação ionizante no colo distal de ratas. Métodos: Foram utilizadas 32 ratas adultas distribuídas em quatro grupos. I - sham; II - oxigenoterapia hiperbárica (OHT); III - radioterapia (RT), e IV - radioterapia e oxigenoterapia hiperbárica (da mesma maneira que nos grupos II e III). Segmentos de colo distal foram fixados em formol a 10% e processados para avaliação histológica e morfométrica. Resultados: Os resultados do experimento mostraram lesão das glândulas intestinais, vasodilatação e infiltrado leucocitário na lâmina própria e submucosa no colo dos animais pertencentes ao grupo RT que diminuiu acentudadamente após a oxigenioterapia hiperbárica. Conclusão: A oxigenitoterapia hiperbárica atenua as alterações morfológicas da mucosa e submucosa do cólon distal de ratas com enterite induzida por radiação ionizante.

Aspectos ultra-estruturais das vilosidades intestinais após o clampeamento do pedículo hepático de ratos

OBJETIVO: Estudar a ultra-estrutura das vilosidades intestinais de ratos após diferentes tempos de clampeamento total do pedículo hepático. MÉTODOS: Foram utilizados 40 ratos, machos, divididos em quatro grupos de 10 animais cada um. O grupo Sham não foi submetido a isquemia. Os grupos E1, E2 e E3 sofreram isquemia de 10, 20 e 30 minutos, respectivamente. Ao final do experimento, fragmentos do intestino delgado (íleo) foram retirados e processados para microscopia eletrônica de transmissão. RESULTADOS: Nos grupos E1 e E2 observou-se infiltração de leucócitos, dilatação vascular e áreas eletrolúcidas na lâmina própria das vilosidades. Já no grupo E3 observou-se desprendimento do revestimento epitelial, desintegração das microvilosidades e núcleos em apoptose. Na lâmina própria notamos áreas hemorrágicas, vasos sangüíneos e linfáticos dilatados e inúmeros leucócitos. CONCLUSÕES: o clampeamento do pedículo hepático hepático provoca congestão esplâncnica, tempo dependente, sendo que aos 30 minutos se nota desprendimento das células epiteliais, apoptose e hemorragia.