Experimental Studies in Metaplastic Ossification

Abstract

Huggins^1-4 has discovered that transplanted epithelium of bladder, ureter, or kidney pelvis induces ossification of the connective tissue of muscle or muscle sheath in the dog. He further found that this epithelium possesses the same potency in fascia lata, subcutaneous tissue or synovial membrane, but not in kidney, liver or spleen. These experiments, successful in the dog, failed (except for one case) in the rabbit, despite the administration of viosterol and parathormone. Dragstedt and Kearns 5 and the author were able to reproduce his results. The former succeeded also in demonstrating ossification about a bit of fascia used to close a surgically produced defect in the bladder walls of dogs.

Sacerdotti and Frattin 6 found that if the vessels of one kidney of a cat, or one renal vein of a rabbit, were tied off, bone would be produced in the organ. It has been shown by Jaffe 7 and others that elementary phosphorus is a stimulus to osteosclerosis. Barth 8 reported ossification in the cat's omentum in response to the implantation of burned bone.

To study the mechanism involved more easily and on a larger scale, albino rats of both sexes and from 105 to 385 g in weight were selected. Under amytal anesthesia pieces measuring several mm in diameter were excised from the bladder and implanted into one or more pockets in the rectus muscle or elsewhere as mentioned. Variations of this and other procedures were employed as indicated in Table I. After a period of time varying from 3 1/2 to 7 weeks, the animals were sacrificed, unless found dead. The experimental areas, when identifiable, were removed for microscopic section. Cysts resulted from the transplantations. They were lined by epithelium of the lower urinary type, varying markedly in thickness, and had many branching pockets. Besides the cysts, solid or almost solid clusters of epithelial cells often appeared.