Biochemical Sequences in the Transformation of Normal Fibroblasts in Adolescent Rats

TLDR

Alkaline phosphatase activity and radioactive sulfate, phosphate, and calcium incorporation were used as sensitive quantitative assays to detect cartilage and bone formation. Acid‑insoluble bone matrix powders rapidly converted fibroblasts into cartilage and bone with marrow, forming a fibroblast‑encapsulated plaque within 24 hr; the conversion to chondroblasts was unstable, whereas osteoblast formation was stable, and the process followed a rigid timetable of sequences.

Abstract

Coarse powders of acid-insoluble matrix of diaphysis and calvarial parietal bone rapidly and consistently transformed fibroblasts into masses of cartilage and bone containing hemopoietic marrow. The transformant was encapsulated by fibroblasts within 24 hr to form a plaque. Transformation was restricted to the central thicknesses of the plaque. Under the stated conditions the alteration of the phenotype, fibroblast to chondroblast, was an unstable transformation, whereas the phenotype change, fibroblast to osteoblast, was stable. The transformation occurred on a rigid timetable of sequences. Measurements of alkaline phosphatase activity and incorporation of radioactive sulfate, phosphate, and calcium were sensitive and quantitative assays for the appearance of the transformed products, cartilage and bone.