A murine model of allogeneic adrenocortical cell transplantation: perspectives for the treatment of Addison's disease in humans

Future directions for adrenal insufficiency: cellular transplantation and genetic therapies

Primary adrenal insufficiency occurs in 1 in 5-7000 adults. Leading aetiologies are autoimmune adrenalitis in adults and congenital adrenal hyperplasia (CAH) in children. Oral replacement of cortisol is lifesaving, but poor quality of life, repeated adrenal crises and dosing uncertainty related to lack of a validated biomarker for glucocorticoid sufficiency, persists. Adrenocortical cell therapy and gene therapy may obviate many of the shortcomings of adrenal hormone replacement. Physiological cortisol secretion regulated by pituitary adrenocorticotropin, could be achieved through allogeneic adrenocortical cell transplantation, production of adrenal-like steroidogenic cells from either stem cells or lineage conversion of differentiated cells, or for CAH, gene therapy to replace or repair a defective gene. The adrenal cortex is a high turnover organ and thus failure to incorporate progenitor cells within a transplant will ultimately result in graft exhaustion. Identification of adrenocortical progenitor cells is equally important in gene therapy where new genetic material must be specifically integrated into the genome of progenitors to ensure a durable effect. Delivery of gene editing machinery and a donor template, allowing targeted correction of the 21-hydroxylase gene, has the potential to achieve this. This review describes advances in adrenal cell transplants and gene therapy that may allow physiological cortisol production for children and adults with primary adrenal insufficiency.

Outcome of adrenal tissue fragments allotransplantation: the impact of cryopreservation

Cryopreservation is thought to have the potential to preserve tissue for transplantation. In addition, it can also be used for decreasing tissue immunogenicity, which might be important for prolonging allograft survival. In the present study we examined the impact of cryopreservation at various cooling rates on the outcome of allotransplantation of murine adrenal tissue fragments (ATFr). ATFr were cryopreserved with a cooling rate at 1; 10; 40 and more than 100 °C/min. After thawing it was found that the number of the cells expressing markers of dendritic cells (CD11c) and macrophages (CD11b) in the suspension obtained from ATFr decreased with increasing cooling rate. After allotransplantation the survival rates of adrenalectomized mice and the blood serum levels of corticosterone were higher in recipients of cryopreserved ATFr. By immunohistochemistry, cryopreserved allografts displayed a decreased infiltration by CD4+ and CD8+ T-lymphocytes as compared to fresh grafts. These findings suggest that cryopreserved allografts cause a less severe rejection by decreasing graft immunogenicity.

Allogeneic adrenocortical transplantation: glucocorticosteroid-independent immunomodulatory properties of adrenal cortex cells

BACKGROUND

Hormone substitution for the treatment of adrenocortical insufficiency does not adequately substitute the physiologic circadian secretion of corticosteroids and leads to long-term sequelae and reduced quality of life. The lack of adaptation to physical and psychologic stress situations may lead to life-threatening Addison's crises. Allogeneic transplantation of adrenal cortex could offer an intriguing alternative. Adrenocortical grafts were demonstrated to proliferate and produce corticosteroids in physiologic concentrations after transplantation.

METHODS

K -transgenic murine lymphocytes and allogeneic adrenal cortex cells were cocultured in mixed lymphocyte reactions to examine the alloimmune response; lymphocytes from T-cell receptor transgenic mice and normal mice, respectively, served as responder cells. The effects of corticosteroids secreted by adrenocortical cells were antagonized by the steroid receptor antagonist mifepristone, whereas the impact of cell-cell interactions was differentiated with transwell culture systems.

RESULTS

Coculture of adrenal cortex cells in mixed lymphocyte reactions markedly suppressed lymphocyte proliferation. Transwell cultures demonstrated that adrenocortical cells exerted their effects by a soluble factor that was only partially antagonized by mifepristone.

CONCLUSION

In vitro, the presence of adrenocortical cells potently suppressed allogeneic immune responses. This effect was not exclusively the result of the secretion of corticosteroids, indicating an additional immunomodulatory property of adrenocortical cells.