Formation of Sertoli cell-enriched tissue constructs utilizing simulated microgravity technology.

Cell transplantation therapy for diabetes and Parkinson's disease offers hope for long-term alleviation of symptoms. However, successful protocols remain elusive due to obstacles, including rejection and lack of tropic support for the graft. To enhance engraftment, testis-derived postmitotic Sertoli cells have been cotransplanted with islets in the diabetic rat (Db) and neurons in the Parkinsonian rat (PD). Sertoli cell tropic, regulatory, and nutritive factors that nourish and stimulate germ cells also support isolated neurons and islets in vitro. Likewise, immunosuppressive properties of Sertoli cells, extant in the testis, are expressed by extratesticular Sertoli cells evidenced by allo- and xenograft immunoprotection of grafts in both the CNS (in the PD model) and the periphery (in the Db model). On this basis, we have created Sertoli islet cell aggregates (SICA) and Sertoli neuron aggregated cells (SNAC) using simulated microgravity culture technology developed by NASA. Isolated rat and pig Sertoli cells were cocultured with neonatal pig islets (SICA) and with immortalized N-Terra-2 (NT2) neurons (SNAC) in the HARV biochamber. Formed aggregates were assayed for desirable functional and structural characteristics. Cell viability in SICA and SNAC exceeded 90% and FasL immunopositive Sertoli cells were present in both. Sertoli cells did not interfere with insulin secretion by SICA and promoted differentiation of NT2 cells to the dopaminergic hNT cell type in SNAC. Addition of Matrigel resulted in structural reorganization of the aggregates and enhanced insulin secretion. We conclude that SICA, SNAC, and Matrigel-induced islet- and neuron-filled "Sertoli cell biochambers" are suitable for long-term transplantation treatment of Db and PD.

A unique cytoplasmic marker for extratesticular Sertoli cells.

In the absence of a definitive cell marker for testis-derived Sertoli cells, their identification in cell culture or in Sertoli cell-facilitated cell transplantation protocols is difficult and limits the creditable evaluation of experimental results. However, the production by prepubertal Sertoli cells of Mullerian inhibiting substance (MIS) presents the possibility of specifically identifying extratesticular Sertoli cells as well as Sertoli cells in situ, by the immunodection of this unique glycoprotein. This study was designed to determine if isolated rat Sertoli cells could be identified by routine immunocytochemistry utilizing an antibody raised against MIS. Sertoli cells immunostained for MIS included Sertoli cells in situ and freshly isolated, cultured and cocultured Sertoli cells, and Sertoli cells structurally integrated with NT2 cells in simulated microgravity. Detection of MIS was also determined by Western blot analysis.

Formation and structure of transplantable tissue constructs generated in simulated microgravity from Sertoli cells and neuron precursors.

Cell transplantation therapy for Parkinson's disease (PD) has received much attention as a potential treatment protocol for this neurodegenerative condition. Although there have been promising successes with this approach, it remains problematic, especially regarding the inability to provide immediate trophic support to the newly grafted cells and the inability to prevent acute and/or long-term graft rejection by the host. To address these issues of cell graftability, we have created a novel tissue construct from isolated rat Sertoli cells (SC) and the NTerra-2 immortalized human neuron precursor cell line (NT2) utilizing NASA-developed simulated microgravity technology. The two cell types were cocultured at a 1:4 (SC/NT2) ratio in the High Aspect Rotating Vessel (HARV) biochamber for 3 days, after which a disc-shaped aggregate (1-4 mm diameter) was formed. Sertoli neuron aggregated cells (SNAC) were collected by gravity sedimentation and processed either for light and electron microscopy or for fluorescent immunocytochemistry. Intra-SNAC clusters of SC and NT2 cells were identified by anti-human mitochondrial protein (huMT--specific for NT2 cells) and cholera toxin subunit B (CTb--specific for SC). There was little evidence of cell death throughout the aggregate and the absence of central necrosis, as might be expected in such a large aggregate in vitro. Ultrastructurally, SC did not express junctional modifications with NT2 cells nor with adjacent SC as is typical of SC in vivo and, in some protocols, in vitro. NT2 cells, however, showed distinct intercellular junction-like densities with adjacent NT2 cells, often defining canaliculi-like channels between the microvillus borders of the cells. The results show that the use of simulated microgravity coculture provides a culture environment suitable for the formation of a unique and viable Sertoli-NT2 (i.e., SNAC) tissue construct displaying intra-aggregate cellular organization. The structural integration of SC with NT2 cells provides a novel transplantable tissue source, which can be tested to determine if SC will suppress rejection of the grafted NT2 cells and provide for their short- and long-term trophic support in situ in the treatment of experimental PD.

Formation of insulin-secreting, Sertoli-enriched tissue constructs by microgravity coculture of isolated pig islets and rat Sertoli cells.

Pancreatic islets, isolated from neonatal pigs, and Sertoli cells, isolated from prepubertal rats, were cocultured in simulated microgravity utilizing the NASA-developed highly accelerating, rotating vessel (HARV) biochamber. Following 5 d of incubation, three-dimensional Sertoli-islet cell aggregates (SICA) retained the ability to secrete insulin when exposed to elevated glucose. SICA contained FasL-positive Sertoli cells and insulin-positive beta-cells randomly organized within the spherical construct. The addition of 1% Matrigel induced the reorganization of aggregates (SICAs formed in the presence of Matrigel [SICAmgs]) showing the peripherialization and epithelialization of Sertoli cells and the centralization of islets in association with lumen-like spaces. The Sertoli cells, but not Matrigel, aided in preserving the structural integrity of HARV-incubated islets. Neither Matrigel nor Sertoli cells appeared to interfere with the ability of SICA or SICA mg to secrete insulin and express FasL.