Summary. Total protein, collagen (hydroxyproline) and glycoproteins (hexosamine) content of control and myelofibrosis (MF) bone marrow samples was determined using a sequential extraction procedure. MF marrow extracts contained higher amounts of collagen than control extracts. The collagen content appeared to increase with the duration of the disease. In more recent MF cases (<2 years) at least 60% of the total collagen was extracted in 0.5 m NaCl. this proportion decreases to 33% in older cases (> 4 years), indicating a progressive insolubilization (crosslinking) of collagen.

The hexosamine content of the extracts decreased in MF as compared to controls reflecting a decrease in glycosaminoglycans (and possibly of structural glycoproteins). The reticulin content of the same bone marrows was estimated by a quantiative morphometric procedure. There was a positive correlation between the morphometrically estimated reticulin surface and the total hydroxyproline content of the marrow samples. The slopes of the least square lines correlating increase of reticulin surface to hydroxyproline content were, however, significantly different in control and MF marrows, indicating a 44% higher increase in histochemically detectable reticulin per unit increase in hydroxyproline content than in the control marrows. This result may indicate a more efficient fibrogenetic process in MF marrow than in normal bone marrow.

The above results confirm the collagenous nature of the fibrous reticulin like material deposited in MF marrows and suggests a correlation between the progression of the disease and the rate of synthesis and deposition of collagen fibres.