Quadruple immunosuppression in a pig model of small bowel transplantation

White paper on guidelines concerning enteric nervous system stem cell therapy for enteric neuropathies

Over the last 20 years, there has been increasing focus on the development of novel stem cell based therapies for the treatment of disorders and diseases affecting the enteric nervous system (ENS) of the gastrointestinal tract (so-called enteric neuropathies). Here, the idea is that ENS progenitor/stem cells could be transplanted into the gut wall to replace the damaged or absent neurons and glia of the ENS. This White Paper sets out experts' views on the commonly used methods and approaches to identify, isolate, purify, expand and optimize ENS stem cells, transplant them into the bowel, and assess transplant success, including restoration of gut function. We also highlight obstacles that must be overcome in order to progress from successful preclinical studies in animal models to ENS stem cell therapies in the clinic.

Drug delivery system using microspheres that contain tacrolimus in porcine small bowel transplantation

Rejection remains a major barrier to successful bowel transplantation, in spite of improved immunosuppressive techniques. Therefore, new, more effective, immunosuppressants, with fewer side effects, are needed. Biodegradable microspheres containing tacrolimus (FK506) were used in an experimental porcine small bowel transplantation. Twenty pigs underwent transplantation and were divided into four groups according to the immunosuppressive regimen. Group A (n = 5): no immunosuppression; group B (n = 6): 0.2 mg/kg per day of FK506; group C (n = 3): 1.0 mg/kg per day of FK506; group D (n = 6): 0.04 mg/kg per day of FK506 contained in biodegradable microspheres. Rejection was diagnosed macroscopically by endoscopic examination and histologically by biopsy specimen analysis. The mean survival time and standard deviation (SD) were 8.8+/-3.5, 11.0+/-1.4, 9.7+/-2.5 and 28.6+/-22.5 days for groups A, B, C, and D, respectively, with a statistically significant difference found between group D, on the one hand, and groups A, B and C, on the other. The mean trough blood concentration of FK506 was 10.5+/-2.2, 27.9+/-6.0 and 10.5+/-3.5 ng/ml in groups B, C and D, respectively. In groups A and B, all pigs died of rejection, without infection. In group C, all died of infection, without rejection. In contrast, none of the pigs in group D developed rejection or infection. Our results clearly show that the drug delivery system using biodegradable microspheres that contain FK506 is effective for controlling rejection with fewer side effects in the porcine small bowel transplantation.

Auxiliary en-bloc liver-small bowel transplantation with partial pancreas preservation in pigs

AIM

The aim of this study was to describe an auxiliary combined liver-small bowel transplantation model with the preservation of duodenum, head of pancreas and hepatic biliary system in pigs. The technique, feasibility, security and immunosuppression were commented.

METHODS

Forty outbred long-white pigs were randomized into two groups, and the auxiliary composite liver/small bowel allotransplantations were undertaken in 10 long-white pigs in each group with the recipient liver preserved. Group A was not treated with immunosuppressive drugs while group B was treated with cyclosporine A and methylprednisolone after operation. The hemodynamic changes and amylase of body fluid (including blood, urine and abdominal drain) were analyzed.

RESULTS

The average survival time of the animals was 10+/-1.929 d (6 to 25 d) in group A while more than 30 d in group B. The pigs could tolerate the hemodynamic fluctuation during operation and the hemodynamic parameters recovered to normal 2 h after blood reperfusion. The transient high amylase level was decreased to normal one week after operation and autopsy showed no pancreatitis.

CONCLUSION

Auxiliary en-bloc liver-small bowel transplantation with partial pancreas preservation is a feasible and safe model with simplified surgical techniques for composite liver/small bowel transplantation. This model may be used as a preclinical training model for clinical transplantation method, clinical liver-small bowel transplantation related complication research, basic research including immunosuppressive treatment, organ preservation, acute rejection, chronic rejection, immuno-tolerance and xenotransplantation.

Recipient preconditioning and donor-specific bone marrow infusion in a pig model of total bowel transplantation

BACKGROUND

In an outbred pig model of total bowel transplantation, we previously showed that simultaneous donor-specific bone marrow infusion (DSBMI), rather than promoting engraftment, sensitizes recipients and causes rejection; it also aggravates the risk of generalized graft-versus-host disease (GVHD) and infection, and tends to reduce recipient and graft survival. Small and large animal models of bone marrow-induced transplant tolerance suggest that some form of recipient preconditioning (RPC) may facilitate engraftment of co-transplanted bone marrow cells and fully expose their tolerogenic potential.

METHODS

In a preclinical model, we prospectively studied the effect of RPC on simultaneous DSBMI and total (i.e., small and large) bowel transplantation. RPC consisted of whole body irradiation with 400 R (day 0); some recipients additionally received horse anti-pig antithymocyte globulin (days -2, -1, and 0). We studied six groups of outbred pigs, all of which underwent at least a total bowel transplant: group 1, nonimmunosuppressed control pigs (n=5); group 2, nonimmunosuppressed DSBMI pigs (n=13); group 3, tacrolimus pigs (n=7); group 4, DSBMI+tacrolimus pigs (n=15); group 5, RPC+nonimmunosuppressed DSBMI pigs (n=11); and group 6, RPC+DSBMI+tacrolimus pigs (n=14).

RESULTS

RPC did not prolong overall survival at 7, 14, 21, and 28 days after transplant. Survival rates were 100%, 100%, 86%, and 71% in group 3; 71%, 43%, 29%, and 29% in group 6; 55%, 9%, 0%, and 0% in group 5; and 60%, 0%, 0%, and 0% in Group 1. Moreover, RPC (groups 5 and 6) increased the incidence of death from rejection, GVHD, and infection when compared with group 3. Survival was significantly higher for RPC+DSBMI+tacrolimus pigs (group 6), compared with RPC+nonimmunosuppressed DSBMI pigs (group 5). Survival greater than 28 days was noted only in pigs that received tacrolimus after transplant: 71% in group 3 versus 29% in group 6. With both RPC and DSBMI (groups 5 and 6), rejection, GVHD, and infection were not mutually exclusive events. In groups 5 and 6, at autopsy, the incidence of rejection and GVHD was 17%; rejection and infection, 17%; and GVHD and infection, 45%. A combination of all three immunologic events was noted in 14%.

CONCLUSIONS

RPC, combined with DSBMI, and with or without posttransplant immunosuppression, does not prolong survival after total bowel transplantation. Rather, it increases the incidence of death from rejection, GVHD, infection, or a combination of these three immunologic events. According to this preclinical study, RPC and unmodified DSBMI do not improve patient and graft outcome after total bowel transplantation and need to be refined before being applied clinically.

Combined transplantation of small and large bowel. FK506 versus cyclosporine A in a porcine model

Clinically, FK506 is superior to CsA after solitary small bowel transplantation (SBTx). Development of diarrhea after SBTx has been the rationale for adding the colon to small bowel grafts. However, the additional lymphoid and bacterial content transferred with total small plus large bowel transplants (TBTx) might aggravate the alloimmune response-rejection and graft-versus-host disease (GVHD)-and increase the risk of infection. We studied the incidence of rejection, GVHD, and infection after TBTx and the impact of CsA versus FK506. We performed orthotopic TBTx with portal drainage after total enterectomy in outbred Yorkshire Landrace pigs, divided into 3 groups: control pigs (n=6) received no immunosuppression; CsA pigs (n= 14) received CsA (5 mg/kg), antilymphocyte globulin (10 mg/kg for 10 days), prednisone (2 mg/kg), and AZA (2.5 mgtkg); and FK506 pigs (n=9) received FK506 (0.2 mg/kg) and prednisone (2 mg/kg). Trough CsA whole blood levels were >400 ng/ml for the first 7 days and >200 ng/ml thereafter. FK506 levels were > 15 ng/ml. We excluded from further analysis 5 early deaths (<3 days) due to anesthesiologic (n=2) or technical reasons (n=3). Median survival of control pigs was 9.5 days (range, 4-13). Cyclosporine did not extend survival: median, 9 days (range, 5-31) (P=0.6). FK506 prolonged survival: median, 37 days (range, 21-49) (P<0.001 vs. control and CsA pigs). Of FK506 pigs, 60% gained weight (+75 g/day), whereas 100% of controls and 75% of CsA pigs lost weight (-550 g/day and -300 g/day, respectively). All control pigs died of rejection within 2 weeks versus none of the FK506 pigs. However, 36% of CsA pigs died of rejection. Groupwise comparison showed less rejection in FK506 versus control pigs (P<0.001) and in FK506 versus CsA pigs (P<0.03), but no difference between CsA and control pigs. None of the control pigs died of GVHD versus 18% of CsA pigs (by day 31) and 37% of FK506 pigs (by day 49). Groupwise comparison showed increased GVHD in FK506 versus control pigs (P<0.001) and a tendency toward increased GVHD in FK506 versus CsA pigs (P=0.08). None of the control pigs died of infection alone versus 22% of CsA pigs (by day 31) and 67% of FK506 pigs (by day 49). Groupwise comparison showed increased infection in FK506 versus control pigs (P<0.001). We detected significant endotoxemia early and late postoperatively. But we saw no specific correlation between endotoxemia, rejection, GVHD, or infection. Based on this study, we have drawn several conclusions: (1) In untreated pigs, TBTx provokes a severe rejection response, but no lethal GVHD. (2) Cyclosporine and particularly FK506 pigs have a high incidence of infection and lethal GVHD, a complication that we had not seen after solitary SBTx. (3) FK506 is superior to CsA in controlling rejection and in prolonging graft and recipient survival; FK506, however, does not reduce GVHD, but rather tends to augment it. (4) TBTx causes endotoxemia. As with solitary SBTx, FK506 is superior to CsA after TBTx. However, longterm survival is difficult to achieve on FK506 recipients because of the development of GVHD and infection.