A: a–j: Effects of IGF-1 or/and PDGF-bb on IL-1β-induced apoptosis and cellular degeneration in chondrocytes.


<p>Transmission electron microscopy was performed to study the effects of IGF-1 or/and PDGF-bb on IL-1β-stimulated primary chondrocytes. Untreated control cultures consist of vital, active cells containing a well-developed rough endoplasmic reticulum, mitochondria and a well-organized cytoplasm after 24 or 48 h in culture (a and b). In contrast, stimulation with IL-1β for 24 h led to degenerative changes including condensation of heterochromatin, swelling of the rough endoplasmic reticulum and mitochondria (c). Longer exposure (48 h) to IL-1β resulted in more severe degenerative features including formation of apoptotic bodies and cell lysis (d). Pre-treatment of IL-1β-stimulated chondrocytes with IGF-1 or/and PDGF-bb for 24 or 48 h inhibited the degenerative effects of IL-1β (e–j). After 48 h (f, h and j), chondrocytes exhibited as large, viable and flattened cells with numerous tiny cytoplasmic processes, mitochondria, rough endoplasmic reticulum and other cytoplasmic organelles compared to control chondrocytes. <b>B: a–e: Redifferentiation of IL-1β-treated chondrocytes in high-density culture by IGF-1 or/and PDGF-bb.</b> Primary chondrocytes were either left untreated (a) or were treated with 10 ng/ml IL-1β (b), pre-treated with 10 ng/ml IGF-1 (c), 10 ng/ml PDGF-bb (d) or 5 ng/ml PDGF-bb and 5 ng/ml IGF-1 (e) for 12 h and then stimulated with IL-1β for another 24 h. The cells were transferred to high-density culture for seven days. Ultrastructural morphology was evaluated by electron microscopy. Control cultures showed characteristic features, including chondrocytes (c) embedded in a well-developed ECM (m) (<b>a</b>). Treatment with IL-1β for 24 h led to matrix breakdown and cell lysis (<b>b</b>). Pre-treatment with IGF-1 (<b>c</b>), PDGF-bb (<b>d</b>) or both growth factors in combination (<b>e</b>) resulted in a marked improvement of chondrocyte phenotype and the formation of cartilage nodules. The formation of a dense ECM (m) surrounding well-developed chondrocytes (c) was observed. ×5000; Bars: 1 µm.</p

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