A Serum-Free System for Primary Cultures of Human Pituitary Adenomas

We report the successful use of a serum-free culture system for primary cultures of human pituitary adenomas. The system utilizes histiotypic suspension culture with low protein-binding membrane inserts that enable cells to retain their three-dimensional tissue configuration, closely mimicking the growth pattern in vivo. A serum-free defined medium was developed with CMRL-1969 (Connaught, Willowdale, Ontario, Canada) supplemented with 0.375% albumin bovine Fraction V, 5 μg/mL insulin, 5 μg/mL transferrin, 5 ng/mL sodium selenite, 30 μg/mL putrescine, 6.85 × 10⁻¹¹ M hydrocortisone, and 3.7 × 10⁻¹¹ M tri-iodothyronine (T₃). We analyzed eight surgically resected human pituitary adenomas. Basal pituitary hormone secretion measured by radioimmunoassay of pituitary hormones was compared with hormone hypersecretion in vivo and with control cells of the same tumors cultured in CMRL-1969 with 10% fetal calf serum. The light microscopic, immunocytochemical, and ultrastructural morphology of cells cultured in this serum-free histiotypic system was compared with cells cultured in serum-supplemented media and with cells cultured on collagen-coated plastic; all cultured cells were compared with the morphology of surgically resected tissues of the same specimens. Basal pituitary hormone secretion during 24-hour incubations correlated with the clinical patterns of hormone excess; the data were similar in serum-enriched and serum-free cultures, however, hormone secretion decreased less rapidly in the serum-free cultures. Cells maintained in the histiotypic culture system closely resembled the corresponding surgically resected tumor using the morphologic parameters and were better preserved than those plated in collagen-coated plastic wells. This comparative study indicates that this serum-free histiotypic culture system provides an ideal method of examining pituitary adenomas in vitro without altering the profile of hormone secretion and cell morphology documented in vivo. This system can be used to examine the production and effects of a wide range of hormones and growth factors that have been implicated as causative agents in pituitary tumorigenesis.