The physiology of the transplanted small bowel: an overview with insight into graft function

Hypothermic machine perfusion alleviates ischemia-reperfusion injury of intestinal transplantation in pigs

Background

Intestinal transplantation (IT) has become an important procedure for the treatment of irreversible intestinal failure. However, IT is extremely vulnerable to ischemia-reperfusion injury (IRI). Due to the limitations of static cold storage (SCS), hypothermic machine perfusion (HMP) is rapidly gaining popularity. In this study, the intestinal HMP system is established and HMP is compared with SCS.

Methods

An intestinal HMP system was built. Ten miniature pigs were randomly divided into the HMP and SCS groups, and their intestines were perfused using the HMP device and SCS, respectively, followed by orthotopic auto-transplantation. Analysis was done on the grafts between the two groups.

Results

Operation success rates of the surgery were 100% in both groups. The 7-day survival rate was 100% in the HMP group, which was significantly higher than that of the SCS group (20%, P< 0.05). The pathological results showed that fewer injuries of grafts were in the HMP group. Endotoxin (ET), IL-1, IL-6, IFN-γ and TNF-α levels in the HMP group were significantly lower than in the SCS group (P<0.05), whereas IL-10 levels were significantly higher (P<0.05).The intestinal expression levels of ZO-1 and Occludin were higher in the HMP group compared to the SCS group, whereas Toll-like receptor 4 (TLR4), nuclear factor kappa B (NFκB), and caspase-3 were lower.

Conclusions

In this study, we established a stable intestinal HMP system and demonstrated that HMP could significantly alleviate intestinal IRI and improve the outcome after IT.

Function and expression of cystic fibrosis transmembrane conductance regulator after small intestinal transplantation in mice

The secretion function of intestinal graft is one of the most important factors for successful intestinal transplantation. Cystic fibrosis transmembrane conductance regulator (CFTR) mediates HCO₃^- and Cl^- secretions in intestinal epithelial cells. In this study, we made investigation on the expression and function of CFTR in an experimental model of murine small intestinal transplantation. Heterotopic intestinal transplantations were performed in syngeneic mice. The mRNA and protein expressions of CFTR were analyzed by real time PCR and western blot. Murine intestinal mucosal HCO₃^- and Cl^- secretions were examined in vitro in Ussing chambers by the pH stat and short circuit current (I_sc) techniques. The results showed that forskolin, an activator of CFTR, stimulated jejunal mucosal epithelial HCO₃^- and Cl^- secretions in mice, but forskolin-stimulated HCO₃^- and Cl^- secretions in donor and recipient jejunal mucosae of mice after heterotopic jejunal transplantation were markedly decreased, compared with controls (P<0.001). The mRNA and protein expression levels of CFTR in donor and recipient jejunal mucosae of mice were also markedly lower than those in controls (P<0.001), and the mRNA and protein expression levels of tumor necrosis factor α (TNFα) were markedly increased in donor jejunal mucosae of mice (P<0.001), compared with controls. Further experiments showed that TNFα down-regulated the expression of CFTR mRNA in murine jejunal mucosa. In conclusion, after intestinal transplantation, the function of CFTR was impaired, and its mRNA and protein expressions were down-regulated, which may be induced by TNFα.

[Apoptosis participation in the acute rejection of intestinal transplantation in rats]

BACKGROUND

Intestinal transplantation is a possible treatment for patients with short bowel syndrome, aiming the reintroduction of oral diet. However, the major obstacle in this procedure is the strong rejection. Delay in rejection diagnosis may be irreversible and lethal.

AIM

To define method for early diagnosis of rejection based on the apoptosis from intestinal allograft.

MATERIAL AND METHODS

Isogenic rats Brown-Norway (BN) and Lewis (LEW) were submitted to intestinal heterotopic allotransplantation and divided in two groups: LEW donor to LEW recipient isograft group C and BN donor to LEW recipient allograft group (Tx). According to the day of sacrifice, Tx group were subdivided in three subgroups with eight animals each as follow: Tx3-- sacrificed at third postoperative day (POD), Tx5 -- sacrificed at fifth POD and Tx7 -- sacrificed at seventh POD. Eight animals from control group were subdivided in three moments according to the time of biopsy from the graft as follow: C3 -- biopsy at third POD; C5 -- biopsy at fifth POD and C7 -- biopsy at seventh POD. All animals from control group were sacrificed at seventh POD. Rejection parameters were compared between the control groups (C3 vs C5, C3 vs C7 and C5 vs C7, and allograft group (Tx3 vs Tx5, Tx3 vs Tx7 and Tx5 vs Tx7). The same parameters were analyzed between the control group and allograft groups ( C3 vs Tx3, C5 vs Tx5 and C7 vs Tx7). In C group no statistical significant difference regarding the expression of the apoptotic cells were detected, while in Tx group, the presence of apoptotic cells were remarkable since the third postoperative day.

Octreotide in the treatment of small intestinal dysfunction after a model of jejunoileal autotransplantation in the pig

Enteric denervation and ischemic injury contribute to dysmotility and malabsorption following intestinal transplantation. We hypothesized that, by prolonging bowel transit and by ameliorating dysmotility, octreotide (OT) may improve cholesterol and bile acid absorption after jejunoileal autotransplantation. Seventeen pigs with fixed food intake underwent either jejunal transection (n = 6), or jejunoileal autotransplantation, which includes extrinsic autonomic denervation, lymphatic interruption, and in situ cold ischemia (n = 11). Five randomly chosen autotransplanted animals received intramuscular long-acting OT (10 mg) once a month. After 8 weeks, weight gain, intestinal transit time, fecal excretion of bile acids and cholesterol, and fractional cholesterol absorption were determined. Jejunal and ileal specimens were collected for histochemical analyses. Plasma cholestenol and campesterol, respective markers of cholesterol synthesis and absorption, were measured after 2 and 8 weeks. Following jejunoileal autotransplantation, octreotide treatment significantly increased the median intestinal transit time from 22.8 to 24.8 h and the median body weight gain from 166 to 187%. Jejunoileal autotransplantation significantly increased fecal bile acid excretion, plasma cholestenol, and bacterially modified fecal neutral sterols, and decreased absorption of cholesterol, plasma campesterol, and biliary cholesterol secretion. These changes were not significantly modified by OT treatment. Bowel wall and mucosal structure, mucosal proliferation, and weight or microvilli showed no statistically significant differences between autotransplanted animals with or without OT treatment. Findings of the present study suggest that octreotide prolongs intestinal transit time and improves weight gain after jejunoileal autotransplantation, but has no effect on malabsorption of cholesterol and bile acids.

Growth hormone selectively improves intestinal cholesterol absorption after jejunoileal autotransplantation in pigs

BACKGROUND/PURPOSE

Small bowel transplantation impairs enteric function and causes malabsorption of cholesterol and bile acids. Growth hormone stimulates intestinal absorptive function. The authors hypothesized that long-term growth hormone therapy could improve absorption of bile acids and cholesterol after autotransplantation of the jejunoileum.

METHODS

Sixteen pigs with similar food, cholesterol, and fat intake underwent either sham laparotomy or a model of jejunoileal autotransplantation, including extrinsic autonomic denervation, lymphatic interruption, and in situ cold ischemia. Five randomly chosen autotransplanted animals received daily growth hormone treatment for 8 weeks. Serum lipids, absorption, and excretion of cholesterol, bile acids, and fat were determined after 8 weeks. Mucosal morphometrics, proliferation, and enzyme activities were determined. Plasma cholesterol precursors and plant sterols, respective markers of cholesterol synthesis and absorption, were measured after 2 and 8 weeks.

RESULTS

After jejunoileal autotransplantation, growth hormone treatment significantly increased body weight gain, cholesterol absorption efficiency from 45.1% to 62.1%, plasma campesterol to cholesterol proportions, and biliary secretion of cholesterol. With or without growth hormone treatment, autotransplantation significantly increased fecal bile acid excretion, plasma cholesterol precursors, fecal bacterially modified neutral sterols, mucosal thickness of the ileum (but not jejunum), and intestinal transit time when compared with sham-operated animals. Crypt cell proliferation, mucosal enzyme activities, and microvilli showed no differences between the groups.

CONCLUSIONS

These findings suggest that growth hormone treatment selectively improves cholesterol, but not bile acid absorption, after autotransplantation of the jejunoileum.

Effects of ileum transplantation and chronic rejection on absorption and synthesis of cholesterol in pigs

We investigated the effects of ileum allotransplantation and chronic graft rejection on the synthesis and absorption of cholesterol. Twenty pigs underwent intestinal transection or ileum transplantation, in which the distal half of the jejunoileum was replaced with an ileal autograft or allograft. Conventional triple therapy with cyclosporine (10 mg/kg per day), azathioprine and methylprednisolone was tapered to cyclosporine (5 mg/kg per day) after 10 weeks. Serum lathosterol and campesterol, respective markers of cholesterol synthesis and absorption, were determined and related to graft histology. When compared to transected controls, auto- and allotransplantation of ileum similarly increased ( P<0.05) lathosterol and decreased ( P<0.01) campesterol for 12 weeks, despite normal graft histology. Chronic graft rejection progressed between 12 and 18 weeks, when a further increase in lathosterol (+104%) and decrease in campesterol (-67%) was observed. Obliteration of mesenterial arteries in chronically rejecting grafts was associated with high cholesterol synthesis ( R=0.975, P=0.0512). Auto- and allotransplantation of the ileum similarly modulate synthesis and absorption of cholesterol in pigs with non-rejecting grafts. Chronic rejection of the ileal graft appears to markedly increase cholesterol synthesis, which may primarily result from impaired ileal reabsorption of bile acids due to gradual obliteration of mesenterial arteries (chronic rejection). Serial measurements of cholesterol synthesis and bile acid absorption may prove to be a useful tool in the diagnosis of chronic rejection-associated small intestinal graft dysfunction.

Effects of transection and extrinsic denervation and a model of autotransplantation of the porcine jejunoileum on cholesterol biodynamics

BACKGROUND/PURPOSE

Small bowel transplantation impairs enteric function, necessitating transection, extrinsic denervation, and ischemia-reperfusion of the small intestine. The authors investigated how each of these nonimmunologic insides of the transplantation procedure modulates biodynamics of cholesterol and absorption of lipids.

METHODS

Twenty-three pigs with similar food, cholesterol, and fat intake underwent sham laparotomy (group 1), transection (group 2), extrinsic jejunoileal denervation (group 3), or a model of autotransplantation, including extrinsic jejunoileal denervation with in situ ischemia-reperfusion (group 4). Serum lipids, absorption, and excretion of cholesterol, bile acids, and fat were determined after 8 weeks. Plasma cholesterol precursors and plant sterols, respective markers of cholesterol synthesis, and absorption, were measured after 2 and 8 weeks.

RESULTS

When compared with sham laparotomy and transection groups, denervation and autotransplantation significantly decreased weight gain and increased plasma cholesterol precursors and fecal excretion of bile acids. In relation to sham operated animals, transection alone modestly increased plasma plant sterols at 2 weeks and biliary secretion and mass absorption of cholesterol. The latter changes were not observed after denervation or autotransplantation, ie, fractional and total absorption of cholesterol were significantly decreased in autotransplanted pigs when compared with transected controls. As compared with all the other groups, autotransplantation significantly increased bacterial metabolites of neutral sterols in feces and net fecal elimination of cholesterol, mainly as bile acids.

CONCLUSIONS

Extrinsic autonomic denervation of the jejunoileum, with or without synchronous ischemia-reperfusion, results in increased cholesterol synthesis, bile acid malabsorption, and decreased weight gain. Cholesterol malabsorption may develop gradually after intestinal autotransplantation, and even a short period of ischemia further impairs absorptive function of the denervated jejunoileum, resulting in increased fecal elimination of cholesterol mainly as bile acids.

Transplante de intestino delgado

RACIONAL: Avanços da biotecnologia e o desenvolvimento de novas drogas imunossupressoras melhoraram os resultados do transplante de intestino delgado. Esse transplante é atualmente indicado para casos especiais da falência intestinal. OBJETIVO: A presente revisão realça os recentes desenvolvimentos na área do transplante de intestino delgado. MATERIAL E MÉTODO: Mais de 600 publicações de transplante de intestino delgado foram revisadas. O desenvolvimento da pesquisa, novas estratégias de imunossupressão, monitorização do enxerto e do receptor, e avanços na técnica cirúrgica são discutidos. RESULTADOS: Realizaram-se cerca de 700 transplante de intestino delgado em 55 centros: 44% intestino-fígado, 41% enxerto intestinal isolado e 15% transplante multivisceral. Rejeição e infecção são as principais limitações desse transplante. Sobrevida de 5 anos na experiência internacional é de 46% para o transplante de intestino isolado, 43% para o intestino-fígado e de cerca de 30% para o transplante multivisceral. Sobrevidas prolongadas são mais freqüentes nos centros com maior experiência. Em série de 165 transplantes intestinais na Universidade de Pittsburgh, PA, EUA, foi relatada sobrevida do paciente maior do que 75% no primeiro ano, 54% em 5 anos e 42% em 10 anos. Mais de 90% desses pacientes assumem dieta oral irrestrita. CONCLUSÃO: O transplante de intestino delgado evoluiu de estratégia experimental para uma alternativa viável no tratamento da falência intestinal permanente. Promover o refinamento da terapia imunossupressora, do manejo e prevenção de infecções, da técnica cirúrgica e da indicação e seleção adequada dos pacientes é crucial para melhorar a sobrevida desse transplante.

Combined small bowel and reduced auxiliary liver transplantation: Case report

AIM: To present a case of combined small bowel and reduced auxiliary liver transplantation.

METHODS: A 55-year-old patient with short bowel syndrome and TPN-related liver dysfunction received small bowel transplantation combined with a reduced auxiliary liver graft. A liver was added to restore the patient's liver function and to protect the intestinal allograft from rejection. His own liver was not removed.

RESULTS: Without donor pretreatment and by conventional immunosuppresive therapy following transplantation, the patient experienced had only one episode of mild intestinal rejection, which was easily reversed by treatment with Methylprednisolone. No liver rejection occurred. Unfortunately, the patient died of heart and lung failure 30 d after transplantation, despite successful graft replacement. Histopathologic examination of specimens after death demonstrated normal structure in both intestinal and liver grafts.

CONCLUSION: The auxiliary liver graft might play a role in preventing intestinal allograft rejection. However, the observation period in this case is short. Further study is needed to determine the risks, effect on the protecting the small-bowel from rejection, and feasibility of general application of this procedure.