Isotransplantation of microencapsulated parathyroid tissue in rats

Abstract

Permanent hypoparathyroidism is one of the most difficult of all endocrine disorders to treat medically. While autotransplantation of parathyroid tissue is clinically established, allotransplantation without immunosuppression is still at the level of animal experiments. Although persons affected by hypoparathyroidism are facing a clearly reduced quality of life, hypoparathyroidism rarely is a life threatening condition. Therefore, systemic immunosuppression for recipients of allotransplants is not justified. A conceptional alternative would be protecting the tissue to be transplanted from the immunologic response by coating it with a semipermeable membrane (microencapsulation). In 1994, we succeeded in iso-, allo- and xenotransplantation of microencapsulated parathyroid tissue in an animal model. Unfortunately, prior to the first clinical use, further analysis of the coating substance (alginate) demonstrated that it has mitogenic properties. Here, we report on the first successful transplantation of microencapsulated parathyroid tissue using a purified, non-mitogenic alginate which is suitable for clinical use.

Mikroenkapsüle edilen paratiroid hücrelerinin in-vitro optimizasyonu

“…İlerleyen yıllarda kalıcı hipoparatiroidizm hastalığı ile mücadele etmek için paratiroid hücrelerinin kapsüle edilerek etkilenmiş sıçanlara verilmesi denenmiştir. Bu amaçla kapsülasyonda kullanılan malzeme mitojenik özellikte olmayan baryum aljinat olarak seçilmiştir 26 . Özellikle immün sistemden kaçış aracı olarak kullanılan mikroenkapsülasyon tekniği 1998 senesinde, bu özelliğinin sınanması için zenotransplantasyon işlemi ile denenmiştir 27 .…”

Living-donor parathyroid allotransplantation for therapy-refractory postsurgical persistent hypoparathyroidism in a nontransplant recipient – three year results: a case report

“…While the transplants are isolated from the immune system nutrients and hormones may pass the semipermeable membrane of the microcapsule. Initial results were encouraging showing normal PTH levels from the third week after transplantation [ 22 ] or graft survival up to 8 months [ 23 ]. However, Bohrer et al recently could demonstrate that the promising results of microencapsulation of allogeneic parathyroid tissue are not due to the protection of the graft from the immune system, but rather derive from delaying immunization of the host [ 24 ].…”

Bacterial biosynthesis of alginates

“…Alginate has also been used for the controlled release of drugs; the drugs are trapped in alginate beads, from which the drug can by slowly released 91. A similar method has been applied to encapsulate functional cells to be transplanted in to a subject (iso‐, allo‐ or xenotransplantation) making the cells much less immunoreactive and thus less likely to be rejected by the subject, for example parathyroid tissue to treat hypoparathyroidism 92–96. Recently alginate encapsulation has been used successfully as a method to orally deliver DNA based vaccines 97.…”