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Different types of human cells which normally grow as monolayers or suspension cultures were tested for their capacity to form and grow as spheroids. Sixteen out of the 27 tested tumour cell lines formed spheroids. Nearly all of these spheroids also grew. With only two exceptions the doubling times were longer when the tumour cells grew as spheroids than when they grew in conventional mass culture. Eleven out of 13 tested human non-tumour cells formed small spheroids but of these only the spheroids of lymphoid origin could grow. These lymphoid cells grew faster when aggregated to spheroids than when in single-cell suspension culture. None of the other non-tumour cells, which normally grew as monolayers, could grow as spheroids. The normally monolayer-cultured tumour cells formed symmetrical spheroids with smooth surfaces while the normally suspension-cultured cells formed irregular spheroids with rough surfaces. All large spheroids had a necrotic centre surrounded by a shell of viable cells. The thickness of the viable cell layer varied depending on cell type. The shape and organization of cells within the spheroids also varied largely. The results show that many types of human cells can be cultured as spheroids and that a wide spectrum of morphological appearances and growth rates can be obtained.

By using biotin-labeled proteoglycan core protein and an avidin-enzyme system, hyaluronic acid (HA) was visualized in the lungs of rats at different times (4, 10, and 20 days) after bleomycin injury. Four days after an intratracheal injection of bleomycin, HA was accumulated in the edematous alveolar septa of the focal areas with lung tissue injury. An interstitial cellular infiltrate of mainly lymphocytes was present. In normal rat lung, HA was not seen in the alveolar tissue but confined to peribronchial and perivascular spaces. Ten and twenty days after bleomycin administration, increasing numbers of macrophages were apparent in the alveolar space. Proliferating fibroblasts and deposition of collagen in the alveolar tissue were observed while the diffuse HA accumulation was becoming less prominent in the alveolar interstitial tissue. HA was more distinctly located in the surroundings of proliferating fibroblasts. A few scattered alveolar macrophages showed a positive staining for HA. An increased water content of the lung was most apparent 4 days after bleomycin administration. The accumulation of HA, a glycosaminoglycan with unique qualities to immobilize water, in the alveolar interstitium suggests a role for HA in the alveolar interstitial edema. The appearance of HA in alveolar macrophages might indicate that macrophage phagocytosis contributes to the elimination of HA from inflamed lung tissue.

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