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Updated: Sep 3, 2026
Scanning Electron Microscopy of Macerated Tissue to Visualize the Extracellular Matrix
Published on: June 14, 2016
Histochemical and ultrastructural studies in fibrodysplasia ossificans progressiva (myositis ossificans progressiva)
Abstract:
By light microscopy the subdermal nodule of a patient with fibrodysplasia ossificans progressiva (FOP) had a fibromatoid histologic appearance. The cytoplasm of the cells stained strongly for mannose-rich glycoprotein with the concanavalin A-horseradish peroxidase (con A-HRP) method. The tumors also exhibited abundant hyaluronidase-digestible mucopolysaccharide in the interstitium with various basic staining reagents. This material appeared to consist principally of hyaluronic acid or chondroitin sulfate with few or mainly masked sulfate esters. At the ultrastructural level, cells interpreted as the tumor cells in the subdermal nodule from the patient displayed extremely hyperplastic granular reticulum and well-developed Golgi elements and appeared very active in synthesis and secretion of protein. The material in the dilated cisternae of the granular reticulum stained for glycoprotein with the con-A-HRP method. Macrophages which comprised the other main cell type in the nodules commonly contacted the tumor cells and occasionally evidenced engulfment of these cells. The intercellular matrix of the nonossified subdermal nodule exhibited greatly increased mucosubstance and, by electron microscopy, showed an unusual network of dialyzed iron-reactive acid muco-substance in the interstitium.
Insights
Fibrodysplasia ossificans progressiva (FOP) subdermal nodules show fibromatoid cells actively synthesizing glycoproteins. Macrophages interact with these cells, engulfing them amidst abundant interstitial mucosubstances.
Area of Science:
- Histopathology
- Cell Biology
- Biochemistry
Background:
- Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by progressive heterotopic ossification.
- Subdermal nodules are a common manifestation, but their precise cellular and molecular composition remains incompletely understood.
Observation:
- Light microscopy revealed fibromatoid histologic features in FOP subdermal nodules.
- Cells within the nodules stained positively for mannose-rich glycoproteins using concanavalin A-horseradish peroxidase (con A-HRP).
- Abundant hyaluronidase-digestible mucopolysaccharides, primarily hyaluronic acid or chondroitin sulfate, were present in the interstitium.
Findings:
- Ultrastructural analysis indicated tumor cells with hyperplastic granular reticulum and well-developed Golgi, suggesting high protein synthesis and secretion activity.
- Glycoproteins were identified within the dilated cisternae of the granular reticulum.
- Macrophages were observed interacting with and occasionally engulfing tumor cells, and the intercellular matrix showed increased acid mucosubstance.
Implications:
- These findings highlight the active synthetic capabilities of cells within FOP nodules, particularly in glycoprotein and mucosubstance production.
- The cellular interactions and matrix composition may provide insights into the pathogenesis of heterotopic ossification in FOP.
- Further research into these cellular and molecular mechanisms could inform therapeutic strategies for FOP.
