Cleared Fat Pads Research Articles

Primary Culture of Rat Mammary Epithelial Cells. I. Effect of Plating Density, Hormones, and Serum on DNA Synthesis<xref ref-type="fn" rid="FN2">2</xref><xref ref-type="fn" rid="FN3">3</xref>

Methods for the primary culture of rat mammary epithelial cells and the response of these cells to various hormones and culture parameters are described. In addition, the techniques for subsequent retransplantation of cultured cells into cleared fat pads of isogenic hosts as a test for normalcy of cultured tissue are detailed. A characteristic and reproducible course of the culture was followed for 2 weeks, after which rat mammary epithelial cells ceased to proliferate and were eventually overgrown by fibroblast-like cells. During the initial 2 weeks in culture, mammary cells and contaminating fibroblast-like cells were responsive to polypeptide and steroid hormones and the percentage of proliferating mammary cells could be enhanced with insulin, prolactin, estradiol, progesterone, and hydrocortisone.

Hormone-dependent mammary tumors in strain GR/A mice. IV. Origin and progression.

Two types of hormone-dependent mammary tumors that occur in strain GR/A mice, i.e., those that appear during pregnancy [pregnancy-dependent mammary tumors (PrDT)] and those induced by treatment with progesterone (P) and estrogen (E) [P + E-dependent mammary tumors (P + E-DT)], were compared in terms of serial transplantation, response to pregnancy, and histology. Both types originated as ductal hyperplasias. When the P + E-induced ductal hyperplasias were transplanted into the parenchyma-free mammary fat pad, they displayed behavior similar to that of pregnancy-induced tumors. P + E-induced ductal hyperplasias gave rise to ductal outgrowths in the virgin host and to PrDT in the pregnant host; this evidence indicated that the ductal hyperplasias are preneoplastic lesions in strain GR mice. In a separate study, attempts to induce progression of tumor occurrence toward pregnancy independence were made because no spontaneous progression had occurred after 8-9 serial transplant generations in PrDT lines. In contrast to nontransplanted PrDT, which usually require 3-5 forced breedings of mice to induce pregnancy independence, 6-8 matings were needed to induce progression to pregnancy independence in the transplanted lines. Results suggested that serial transplantation in the cleared fat pad may select for less neoplastic variants.

An Experimental Animal Model for the Study of Human Scirrhous Carcinoma 2

Scirrhous-like carcinomas were induced by the inoculation of cloned mouse mammary carcinoma cells into the cleared fat pads of BALB/c mice. The inoculated cells induced palpable tumors in 100% of the animals within 60 days. The epithelial cells in vivo grew in rows and clusters and were attached by short developing desmosomes. Microvilli and organelles were scarce; intracisternal type A particles were observed in all the epithelial cells. Carcinoma cells invaded the dermis and muscle. The stroma was formed by morphologically normal fibroblasts and large masses of collagen. No virus particles were observed budding from the epithelial cell surface or in the stromal fibroblasts. The similarities between the scirrhous-like carcinoma in BLAB/c mice and the juman scirrhous carcinoma suggest this animal system as a model for the study of the human disease.

Immunologic methods for the identification of cell types. I. Specific antibodies that distinguish between mammary gland epithelial cells and fibroblasts.

Antibodies were produced against intact mouse mammary epithelial cells and cleared fat pad fibroblasts; after appropriate absorption, two specific antibody preparations were obtained. The antimammary epithelial cell preparation did not appear to be strain- or species-specific. The antimammary fibroblast preparation recognized both mammary and fetal fibroblasts. These findings suggested that each cell type possessed distinct immunogenic components. These components were characteristic of each cell type and could be used to identify the respective cells by an immunofluorescence technique. Characterization of the antigenic component of mouse mammary epithelial cells demonstrated that this antigen was released during enzymatic cell dissociation and was regenerated underin vitro culture.