Volume 161 Number 5 blood flow on electrocortical activity, breathing and skel- etal muscle activity in fetal sheep. AM] OBSTET GYNECOL 1986; 154:655-62. 11. Cloete ]HL. Prenatal growth in the Merino sheep. On- derstepoort] Vet Sci Anim Ind 1939;13:417. 12. Hyman PE. Enhanced urinary immunoreactive throm- boxane in neonatal NEC. Am] Dis Child 1987;141:686- 89. 13. Makila V-M,]ouppila P, Kirkinen P, et al. Placental thom- boxane and prostacyclin in the regulation of placental blood flow. Obstet Gynecol 1986;68:537-40. Thromboxane synthetase inhibition on homeostasis 14. Walsh SW. Preeclampsia: an imbalance in placental pros- tacyclin and thromboxane production. AM] OBSTET Gy- NECOL 1985;152:335-40. IS. Wallenburg HCS, Dekker GA, Makovltz ]W, Rotmans P. Low-dose aspirin prevents pregnancy-induced hyperten- sion and preeclampsia in angiotensin-sensitive primigrav- idae. Lancet I: 1-3, 1986. 16. Van Assche FA, Spitz B. Thromboxane synthetase inhi- bition in pregnancy-induced hypertension. AM] OBSTET GYNECOL 1988;159:1015-6. Human uterus-derived growth substances for rat bone cells and fibroblasts Michael Koutsilieris, MD, PhD Quebec, Quebec, Canada The effects of extracts from normal human uteri on tritiated thymidine incorporation and cell number were studied in primary cultures of isolated fetal rat calvarial osteoblasts and fetal rat skin fibroblasts. In this study crude uterine extracts were shown to stimulate tritiated thymidine incorporation into cellular deoxyribonucleic acid in osteoblast-like and fibroblast-like cell cultures above controls levels. This effect, which began after 6 hours, was maximal after 24 hours of inCUbation. In addition, the number of osteoblast-like and fibroblast-like cells increased above control levels after 1, 3, and 5 days of incubation. The above effects were dose-dependent, and maximal stimulation of uterine extracts was comparable with the stimulation achieved by 10% fetal bovine serum. The degree of stimulation by uterine extracts, expressed as percent above controls, was not dependent on the concentration of fetal bovine serum in cell culture medium. The above results are consistent with the view that uterine extracts contain mitogen(s) for bone cells and fibroblasts. These mitogens could play an important role in bone physiology and uterine pathophysiology. (AM J OBSTET GYNECOL 1989;161 :1313-7.) Key words: Growth factors, uterus, osteoblasts, fibroblasts The presence of mitogenic andlor chemotactic ac- tivity in the extracts of various female genital organs, including rat, porcine, bovine, and human tissues, for endothelial and fibroblast-like cells, has been well doc- umented. I - 7 In addition, extracts from mouse uteri have the capacity to facilitate the metastatic process of a syn- geneic teratocarcinoma cell line to distant lymph nodes in mice. 8 Recently, the angiogenic growth factor present in extracts of corpus luteum was purified and found to be identical to fibroblast growth factor. 7 Although the presence of growth factors in extracts of various female genital tissues for endothelial and fibroblast-like cells From the Department ofObstetncs and Gynecology, Laval Umversity, and the Endocrine Research Unit, Research Center, St-Fran,olS d'Assise Hospital. Received for publication January 19, 1989; revISed July 3, 1989; accepted July 10, 1989. Reprint requests: Dr. Mtchael Koutszitens, Research Center, St-Fran,olS d'AsslSe Hospttal, Quebec, Quebec, Canada G1 L 3L5. 611115147 has been examined, 1-7,9,10 the presence of mitogens for osteoblast-like cells has not yet been tested. In this study evidence is presented for the presence of growth substances extracted from normal human uteri, which are capable of stimulating the proliferation of cells of the osteoblast and fibroblast phenotype. Material and methods Tissue specimens were obtained at autopsy from healthy young women who had died accidentally (31.6 ± 3.8 years old, mean ± SEM; n = 3). Tissues were washed with Hanks' balanced salt solution, pH 7.4, and kept frozen at -70 0 C. Representative tissue specimens underwent routine pathologic examination. In all instances specimens were reported normal and consisted of myometrial and endometrial elements. Tissue was first homogenized at 4 0 C in acetone (30 mil gm). The insoluble precipitate was then homoge- nized in n-hexane (30 mil gm) and the insoluble ma- terial from this procedure was homogenized again in 1313