Project Details
Abstract
Composite tissue allotransplantation (CTA), which refers to the en bloc
transplantation of neurovascularised functional anatomical units containing
heterogenous tissues, such as a hand or the larynx, holds great potential for
reconstructive surgery. However CTA recipients currently require lifelong
immunosuppressive therapy and may suffer from the associated wide-ranging and
sometimes severe side effects. Even in the presence of immunosuppressive therapy,
chronic rejection of allotransplants still occurs. The induction of immunologic
unresponsiveness (or tolerance) in recipients to donor tissues is one approach that may
overcome these obstacles in transplantation. Immune tolerance to donor tissues can
be achieved through inducing a state of chimerism by using bone marrow
transplantation (BMT), but it may not be an acceptable tolerance protocol for CTA
because of total body irradiation-induced toxic effects. It has recently been
increasingly demonstrated that oral administration of antigens or donor splenocytes
can modulate the immune response in experimental autoimmune diseases in animals
and humans, and prolong the survival of allografts such as heart and kidney.
Combination therapy using delayed low-dose cyclosporine A (CsA) or donor
hepatocytes appears more capable of prolonging allograft survival. Several
investigators suggest that CD4+CD25+ T cells, which release suppressive cytokines
such as interleukin (IL)-4, IL-10, and transforming growth factor beta (TGFβ), are
involved in the induction of immune tolerance through oral administration of donor
splenocytes. The route of administration of donor splenocytes may be critical for its
efficacy. Ishido et al demonstrated that intrajejunal administration of donor
splenocytes significantly increased heart allograft survival in comparison to oral
administration. Although the administration of donor splenocytes appears to prolong
solid organ allograft survival, the effect of intrajejunal administration of donor
splenocytes on CTA survival and the possible underlying mechanisms have not been
elucidated. In order to answer these questions, we will use the well-characterised
major histocompatibility complex (MHC)-mismatched rat model in which
Brown-Norway (BN) rats are used as donors and Lewis (LEW) rats are used as
recipients. Firstly, a gastrojejunostomy will be sited, using biomedical silicone tubing,
and subcutaneously tunneled to reside on the dorsum of the neck of recipient Lewis
rats. After a one-week recovery period, these rats will receive a groin flap containing
skin and subcutaneous tissue from BN rats. Recipient rats will be treated with delayed,
low-dose, subtherapeutic CsA (2.5 PROBABLY 4 mg/kg/day) from day 3 after the
transplantation. In the first-year of study, we will establish four different experimental
groups (Table I) to investigate that whether the intrajejunal administration of a
mixture of donor splenocytes and hepatocytes is more effective in prolonging groin
flap survival in comparison to monocellular (splenocytes or hepatocytes)
administration. If successful, the donor specificity of tolerance will be assessed
using third party groin skin flap from an irrelevant inbred strain such as ACI rats, a
cross between the August and Copenhagen-Irish strain.
Table I. Allotransplant LEW rats with or without intrajejunal feeding
of splenocytes and/or hepatocytes
In the second-year of study we will divided animals into two groups (Table II) to
investigate whether CD4+CD25+ T cells play an important role in prolonging CTA
survival when using the intrajejunal route to administer ※donor cells. (The donor cells
can be splenocyte alone, hepatocyte alone or mixture of splenocyte and hepatocyte
depending on the result of the first year study.)
Table II. Allotransplant LEW rats with or without intrajejunal feeding
of donor cells
If there is a positive correlation between the generation of CD4+CD25+ T cells and the
prolongation of CTAs, in the third-year of study we will establish three more groups
(Table III) to investigate whether this primed population of CD4+CD25+ T cells can
transfer donor specific immune tolerance from intrajejunally treated Lewis rats
(※using donor BN splenocytes and/or hepatocytes depending on the result of the first
year study) to naive LEW rats.
Table III. Allotransplant LEW rats with intravenous administration of
CD4+CD25+ T cells isolated from naive or treated LEW rats
Our preliminary results using the in vitro mixed lymphocyte reaction assay have
shown that the responsiveness of the recipient T cell population to alloantigen is
reduced in LEW rats which have been treated by intrajejunal donor BN splenocytes
for 6 consecutive days. Since T cell activation to alloantigen is critical to allograft
rejection, our preliminary results encourage further studies. The results from the
above studies should provide valuable information regarding the effects of intrajejunal
administration of donor splenocytes (and/or hepatocytes) in combination with delayed
low-dose CsA on the prolongation of CTA survival, as well as the role of CD4+CD25+
T cells in the establishment of tolerance by intrajejunal administration of donor cells.
Project IDs
Project ID:PC9708-0074
External Project ID:NSC95-2314-B182-019-MY3
External Project ID:NSC95-2314-B182-019-MY3
Status | Finished |
---|---|
Effective start/end date | 01/08/07 → 31/07/08 |
Fingerprint
Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.