Dissertation (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Introduction
Despite advances in insulin therapy, the side effects associated with diabetes mellitus still
remain. Pancreas transplantation has benefited diabetics with end-stage renal failure by
reversing the diabetic state and preventing or reversing the progression of diabetes associated
diseases. Currently the side effects associated with lifelong immunosuppression preclude
pancreas transplantation as a viable treatment option for both type I and II diabetics.
In the laboratory, transplanted rat foetal pancreata have been shown to be able to reverse the
clinical signs of streptozotocin-induced diabetes in an isogeneic model. Reversal of diabetes
by allogeneic foetal rat pancreas transplantation, although possible has proved to be more
difficult due to fierce rejection of the grafts and the diabetogenic effects of conventional
immunosuppressants.
Aims
One of the goals, focus and intentions of this laboratory study in rodents, is to contribute new
information to the scientific literature. The potential to “reverse” the diabetic state by
allogeneic foetal pancreatic transplantation, was the main stimulus for this study.
Methods
Foetal pancreata of 16-18 days gestation were transplanted into a surgically prepared renal
subcapsular space. Immunosuppressive protocols used to prevent rejection of the allogeneic
foetal rat pancreata included donor specific transfusion (DST), cyclosporine [a calcineurin
inhibitor (CsA)], mycophenolate mofetil [a purine syntase inhibitor (MMF)], and a mouse
anti-rat CD4 monoclonal antibody (W3/25). Immunosuppressants were used as
monotherapies and in combination. Results
Isogeneic foetal rat pancreas transplantation resulted in the growth and development of
mature insulin producing islets of Langerhans at the site of engraftment. Allogeneic foetal
pancreatic transplantation without immunosuppression resulted in complete rejection of the
grafts at 14 days post-transplantation.
Histological assessment of allografts at 14 and 30 days post-transplantation showed that CsA
was able to prevent acute rejection in our rat models although graft scores and survival were
improved if CsA was combined with MMF. Intraperitoneal anti-CD4 monoclonal injections
were well tolerated, and if given daily effectively prolonged graft survival up to 30 days.
Combining DST with anti-CD4 and CsA induction therapy provided long-term graft survival
without daily immunosuppression. This combination, together with allogeneic foetal rat
pancreas transplantation, was effective in reversing the clinical signs of experimentally
induced diabetes. To my knowledge these are the first published results in which reversal of
streptozotocin induced diabetes was achieved by fully MHC mismatched foetal rat pancreatic
transplantation.
Conclusion
Foetal rat pancreatic transplantation is a potential source of endocrine replacement, which,
with effective immunosuppression allows for the development of functional islets able to
reverse the clinical signs of experimentally induced diabetes in an allogeneic rat model. An
unique immunosuppressive protocol, with potential clinical relevance in the human,
combines anti-CD4 mAb, CsA and DST induction therapy, which alleviates the burden of
daily immunosuppression and associated side effects. / AFRIKAANSE OPSOMMING: Inleiding
Ten spyte van die vordering met modeme insulienterapie bly die newe-effekte, waarmee
diabetes mellitus geassosieer is, steeds ‘n probleem vir diabete. Diabetiese pasiente met
eindstadium nierversaking trek geweldig voordeel uit nier-pankreasoorplantings wat die
diabetes omkeer en die progressie van diabetesverwantesiektes voorkom of selfs omkeer.
Die newe-effekte van lewenslange immuunonderdrukking skakel pankreasoorplanting uit as
‘n lewensvatbare behandelingsopsie vir tipe I of II diabete.
In ‘n streptozotosien-gei'nduseerde diabetiese rotmodel kan isogenei'ese fetale
pankreasoorplanting die kliniese tekens van diabetes omkeer. Die omkering van
streptozotosien-gei'nduseerde diabetes deur allogeneiese fetale pankreasoorplanting behoort
moontlik te wees indien verwerping en die diabetogeniese newe-effekte van konvensionele
immuunonderdrukkers oorkom word.
Doelstellings
Een van die mikpunte, fokusse en oogmerke van hierdie laboratorium studie in knaagdiere, is
om ‘n betekenisvolle bydrae tot nuwe kennis in die wetenskaplike literatuur, te maak. Die
potensiaal om die diabetiese toestand deur allogeneiese fetale pankeasoorplanting om te keer,
was die hoof stimulus vir die studie.
Metodes
Fetale rotpankreata van 16-18 dae gestasie was in ‘n chirurgies voorbereide spasie onder die
nierkapsel oorgeplant. Immuunonderdrukkende protokolle, vir die voorkomming van
verwerping van die allogeneiese fetale pankreasoorplantings, het donorspesifiekeoortappings
(DST), siklosporien [‘n kalsineurien inhibitor (CsA)], mikofenolaat mofetiel [‘n purien sintase inhibitor (MMF)] en ‘n anti-rot CD4 monoklonale antiliggaam (W3/25) ingesluit. Die
immuunonderdrukkers is as mono- of as kombinasieterapie gebruik.
Resultate
IsogeneTese fetale rotpankreasoorplanting het tot die ontwikkeling van volwasse
insulienproduseerende eilande van Langerhans gelei, wat die kliniese tekens van
streptozotosien-gei'nduseerde diabetes kon omkeer.
Allogenei'ese fetale rotpankreasoorplanting sonder immuunonderdrukking het tot algehele
verwerping van die oorplanting binnel4 dae na oorplanting gelei.
Histologiese beoordeling van die oorplantings 14 en 30 dae na oorplanting het getoon dat
CsA akute verwerping van fetale pankreasoorplantings in die rotmodelle voorkom. Indien
CsA met MMF gekombineer word, word die oorplantings-telling en oorlewing verbeter.
Intraperitoneale anti-CD4 monoklonale inspuitings was goed verdra, en indien daagliks
toegedien, het dit die oorlewing van die pankreasoorplantings effektief tot 30 dae verleng.
Die kombinasie van DST, anti-CD4 en CsA induksieterapie het tot langtermyn oorlewing van
die pankreasoorplantings gelei sonder verdere daaglikse immuunonderdrukking. Die
induksieterapie in kombinasie met allogenei'ese fetale pankreasoorplanting was effektief in
die omkering van die kliniese tekens van streptozotosien-gei'nduseerde diabetes in die rot.
Hierdie is, sover ek weet, die eerste keer dat omkering van streptozotosien-gei'nduseerde
diabetes suksesvol met ‘n volledige MHC onverenigbare allogenei'ese fetale
pankreasoorplanting behaal is.
Gevolgtrekkings
Fetale rotpankreasoorplanting is ‘n potensiele bron vir endokrien vervangingsterapie, wat met
effektiewe immuunonderdrukking tot die ontwikkeling van funksionele eilande van
Langerhans lei, wat die vermoe het om die kliniese tekens van experimenteel-ge'induseerde diabetes in ‘n allogeneiese rotmodel om te keer. ‘n Unieke immuunonderdrukkingsprotokol,
met kliniese relevansie, kombineer DST met anti-CD4 mAb en CsA induksieterapie wat die
las van daaglikse immuunonderdrukking en die geassosieerde newe-effekte van
konvensionele immuunonderdrukking verlig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50064 |
| Date | 12 1900 |
| Creators | Muller, Christo John Frederick |
| Contributors | Du Toit, D. F., Bouic, P. J., Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Anatomy and Histology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 327p. : ill. |
| Rights | Stellenbosch University |
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