Histological changes during regression induced by retinoic acid in a transplantable rat chondrosarcoma.
Daily oral treatment with retinoic acid (100 mg/kg bodyweight) induced regression of a transplantable rat chondrosarcoma. In a previous biochemical investigation we have shown that the tissue breakdown is preceded by the loss of proteoglycan. The present study describes the histological changes induced by retinoic acid. A decrease in the intensity of metachromatic staining with toluidine blue was noted already after 1 day and the discoloration was almost complete after 4 days correlating with the loss of proteoglycan. Especially in the perichondrium there was a rapid proliferation of fibroblasts and monocytes. Osteoclast-like cells were missing, but tumor nodules were eroded and split up by penetrating perichondrium. After 4 days of treatment larger necrotic areas were found, initially in the center of tumor nodules only. In other areas the majority of tumorous chondroblasts survived. Tumor nodules appeared partly mesenchyma-like with some fibroblast-like cells suggesting a dedifferentiation of chondroblasts by retinoic acid. we believe that tumor regression induced by retinoic acid involved proteoglycan degradation by chondroblasts themselves and chondroclast-like activity of monocytes and fibroblasts.
D000818:Animals; D002813:Chondrosarcoma / Q000032:analysis / Q000473:pathology*; D005260:Female; D005347:Fibroblasts / Q000473:pathology; D009000:Monocytes / Q000473:pathology; D009336:Necrosis; D009368:Neoplasm Transplantation; D011509:Proteoglycans / Q000032:analysis; D051381:Rats; D012513:Sarcoma, Experimental / Q000032:analysis / Q000473:pathology; D013194:Staining and Labeling; D013997:Time Factors; D014212:Tretinoin / Q000494:pharmacology*
D011509:Proteoglycans; D014212:Tretinoin