Differentiation of Fibroblasts in Tissue Culture,as Determined by Mucopolysaccharide Production. ∗

Summary

1. Cultures of human synovia and rat subcutaneum have continued to produce, over a period of months, substances forming a characteristic mucin clot. Mucin clots have also been produced in culture media from beef embryo bone, from human embryo skin, bone, tendon, epiphysis, aorta and pericardium, and from chick embryonic bone and heart. 2. The mucopolysaccharide nature of the substances produced is attested to by the inhibition of mucin clot production by testicular and bacterial hyaluronidase. 3. Large mucin clots produced in the media of tissue cultures correspond generally to large amounts of turbidimetrically determined mucopolysaccharides produced by living cells in tissue culture. 4. Production of a mucin clot in the medium of cultures of fibroblasts from various tissues (or even a single roller tube culture) can be used as a method for preliminary orientation in determining differentiation of various types of fibroblasts, and for studying factors influencing such differentiation.