Fetal Pituitary Transplantation

1. Fetal Pituitary Transplantation Viability and Functionality of Human Fetal Pituitary Cells Transplanted into Hypophysectomized Rats Reza Jarrahy, M.D. Hrayr K. Shahinian, M.D. Department of Surgery, Division of Skull Base Surgery Cedars-Sinai Medical Center Los Angeles, California

2. Abstract • Human fetal pituitary cells were transplanted into twenty three hypophysectomized rats via a transauricular approach. Baseline serum human growth hormone levels (hGH) were measured prior to intervention and then at one week intervals following transplantation. Rats receiving pituitary cell transplants demonstrated hGH levels that were maximal one week following transplantation and that gradually tapered off in the subsequent weeks. These results offer preliminary evidence that human fetal pituitary cells are able to survive and retain functionality after transplantation into rats.

3. Background • Pituitary transplant models: historical perspectives • Early work: design • species: rodent (isograft/homograft/allograft) • substrate: neonatal and adult rodent pituitary tissue • site: renal, ocular, intracerebral (“immunologic privilege”: thalamus; ventricles; corpus callosum; temporal lobe;) • endpoints: end organ weights & histology

4. Background • Pituitary transplant models: historical perspectives • Early work: outcomes • pituitary function could be restored to hypophysectomized rats following transplantation of rat pituitary gland tissue • most complete restitution seen in transplants to the median eminence (“hypophysiotropic area”)

5. Background • Pituitary transplant models: historical perspectives • Later work: design • species: rodent xenografts (mouse pituitary to rat); (human striatum to rat) • substrate: fetal tissue; cell cultures • site: median eminence • endpoints: serum hormone levels; immunohistochemistry; electron microscopy

6. Background • On substrate: fetal tissues • less immunogenic • durable grafts: • “There is no question that fetal tissue is superior to adult tissue as a source of graft material both because of its resistance to trauma and anoxia and because of its ability to proliferate. Fetal tissue may also elaborate a variety of trophic factors that may be beneficial to the host.” • Tulipan N: Brain transplants. Neur Clin 1988;6:405-420.

7. Background • On substrate: cell culture • less immunogenic • durable grafts • “Theoretical consideration regarding diffusion of nutrients to the center of grafts and development of a new blood supply [render] a theoretical advantage to using suspensions of tissue in which most cells are bathed in nutrient medium prior to transplantation… In addition, it is known that cultured cells often lose their histocompatibility antigenicity and might therefore not be prone to rejection.” --Tulipan N: Brain transplants. Neur Clin 1988;6:405-420.

8. Background • Pituitary transplant models: historical perspectives • Later work: outcomes • “Research into CNS transplantation has documented the ability of transplanted CNS tissues to survive, develop processes, elongate, organize into anatomically correct configurations, and establish electrophysiologically and secretorily functional synaptic connections with host tissue.” • --Wilberger JE: Transplantation of Central Nervous Tissue. • Neurosurgery 1983;13:90-94.

9. Background • Pituitary transplant models: historical perspectives • Later work: outcomes • “The pituitary gland itself may be transplanted to the median eminence of hypophysectomized rats with survival of pituitary tissue and resultant correction of hormonal abnormalities.” • Tulipan N: Brain transplants. Neur Clin 1988;6:405-420.

10. Background • Pituitary transplant models: historical perspectives • Later work: outcomes • reaffirmation of earlier studies with more conclusive evidence • documentation of successful inter-species human to rat CNS transplants (Parkinsonian models) • successful use of fetal tissue

11. Central question: • Can pituitary function be reconstituted in hypophysectomized rats after transplantation of human fetal pituitary cells?

12. Method • Species (recipient): • Harlan/Sprague Dawley male hypophysectomized rats • age 20 weeks; weight 170-240 g • Substrate: • human fetal pituitary cell culture • derived from fetuses of 20 week gestation • Site: • transauricular approach to medial basal hypothalamus • Endpoints: • serum levels of human hormone (human GH, ACTH) • endocrine organ histology

13. Method human pituitary cell suspension hypophysectomized rat serum hGH serum hACTH

14. Results: hormone levels • serum hGH (ng/ml) specimen

15. Results: hormone levels • serum hACTH (pg/ml) * rodent ACTH

16. Results: hormone levels • serum hACTH (pg/ml) specimen

17. Results: histology • In animals 1, 2, 3, and 5 (recent data), the endocrine glands were normal and did not exhibit histological signs of involution, indicating that they were exposed to the necessary quantities of adenohypophyseal hormones.

18. Results: histology • In animals 4 and Control the abnormal histology of the testes, adrenals, and thyroids indicated that the endocrine glands were not under the influence of adenohypophyseal hormones.

19. Conclusions • Human fetal pituitary cells transplanted into the hypophysiotropic area of the hypophysectomized rat can remain viable and retain secretory function

20. Conclusions • Human fetal pituitary cells transplanted into the hypophysiotropic area of the hypophysectomized rat may, at least partially, reconstitute a normal hypothalamic-pituitary-end organ axis and regulate normal maturation and function of endocrine organs (thyroid, adrenals, gonads)

21. Future directives • Series with larger numbers of animals (greater statistical power) and both hypox and normal controls (underway) • Immunosuppressive therapy trials (underway) • Refined transplantation method • Histology of skull base/sella/cerebral tissue

22. References • Akalan N, et al: Fetal pituitary transplants into the hypothalamic area of hypophysectomized rats. Surg Neurol 1988;30:342-349. • Asa S, Kovacs K: Functional morphology of the human fetal pituitary. Pathol Ann 1984;19:275-315. • Csernus V, Lengvari I, Halasz B: Further studies on ACTH secretion from pituitary grafts in the hypophysiotropic area. Neuroendocrin 1975;17:18-26. • Das GD, Hallas BH, Das KG: Transplantation of brain tissue in the brain of rat. I. Growth characteristics of neocortical transplants from embryos of different ages. Am J Anat 1980;158:135-145. Flament-Durand J: Observations on pituitary transplants into the hypothalamus of the rat. Endocrinology 1965;77:446-454. • Falconi G, Rossi GL: Transauricular hypophysectomy in rats and mice. Endocrinology 1964;74:301-303.

23. References • Frodl EM, et al: Human embryonic dopamine neurons xenografted to the rat: effects of cryoprecipitation and varying regional source of donor cells on transplant survival, morphology and function. Brain Res 1994;647:286-298. • Geny C, et al: Microglial chimaerism in human xenografts to the rat brain. Brain Res Bull 1995;38:383-391. • Halasz B, Pupp L, Uhlarik S: Hypophysiotropic area in the hypothalamus. J Endocrin 1962;25:147-154. • Martini L, et al: Functional and morphological observations on the rat pituitary grafted into the anterior chamber of the eye. J Endocrin 1959;19:164-173. • Nikitovitch-Winer M, Everett JW: Functional restitution of pituitary grafts re-transplanted from the kidney to the median eminence. Endocrinology 1958;63:916-930.

24. References • Pundt LL: Localization of dopamine receptors and associated mRNA in transplants of human fetal tissue in rodents with experimental Huntington’s Disease. Neurosci Res 1997;27:305-315. • Pundt LL, et al: Organization and histochemical phenotype of human fetal cerebellar cells following transplantation into the cerebellum of nude mice. Cell Transplant 1997;6:479-489. • Scheinberg LC, Edelman FL, Levy WA: Is the brain “an immunologically privileged site”? Arch Neurol 1964;11:248-264. • Tulipan NB: Brain transplants. Neur Clin 1988;6:405-420. • Tulipan NB, Huang S, Allen GS: Pituitary transplantation: cyclosporine enables transplantation across a minor histocompatibility barrier. Neurosurgery 1986;18:316-320. • Wilberger JE: Transplantation of Central Nervous Tissue. Neurosurgery 1983;13:90-94.