Department of Anatomy and Cellular Biology, Tufts University School of Medicine, Boston, Massachusetts.
J Biomed Mater Res A. 2012 Nov;100(11):2905-12. doi: 10.1002/jbm.a.34227. Epub 2012 Jun 14.
Collagen-based gels have been widely used to determine the factors that regulate branching morphogenesis in the mammary gland. The patterns of biomechanical gradients and collagen reorganization influence the shape and orientation of epithelial structures in three-dimensional (3D) conditions. We explored in greater detail whether collagen type I fibers with distinct biomechanical and fiber-assembling properties, isolated from either bovine or rat tail tendon, differentially affected the epithelial phenotype in a tissue culture model of the human breast. Rat tail collagen fibers were densely packed into significantly longer and thicker bundles compared to those of the bovine type (average fascicle length 7.35 and 2.29 μm, respectively; p = 0.0001), indicating increased fiber alignment and biomechanical enablement in the former. MCF10A epithelial cells formed elaborated branched tubular structures in bovine but only nonbranched ducts and acini in rat tail collagen matrices. Ductal branching in bovine collagen was associated with interactions between neighboring structures mediated through packed collagen fibers; these fiber-mediated interactions were absent in rat tail collagen gels. Normal breast fibroblasts increased the final size and number of ducts only in rat tail collagen gels while not affecting branching. Our results suggest that the species of origin of collagen used in organotypic cultures may influence epithelial differentiation into alveolar or ductal structures and the patterns of epithelial branching. These observations underscore the importance of considering the species of origin and fiber alignment properties of collagen when engineering branching organs in 3D matrices and interpreting their role in the tissue phenotype.
胶原基凝胶已被广泛用于确定调节乳腺分支形态发生的因素。生物力学梯度和胶原重组的模式影响三维（3D）条件下上皮结构的形状和方向。我们更详细地探讨了从牛或大鼠尾巴肌腱中分离出的具有不同生物力学和纤维组装特性的 I 型胶原纤维是否会在人乳腺组织培养模型中对上皮表型产生不同影响。与牛型胶原纤维相比，大鼠尾巴胶原纤维密集地排列成更长、更厚的束（平均束长度分别为 7.35 和 2.29 μm；p = 0.0001），这表明前者的纤维排列和生物力学性能得到了提高。MCF10A 上皮细胞在牛型胶原中形成了精细的分支管状结构，但在大鼠尾巴胶原基质中只形成了非分支的导管和腺泡。牛型胶原中的导管分支与相邻结构之间通过密集的胶原纤维介导的相互作用有关；在大鼠尾巴胶原凝胶中不存在这种纤维介导的相互作用。正常乳腺成纤维细胞仅在大鼠尾巴胶原凝胶中增加导管的最终大小和数量，而不影响分支。我们的结果表明，在器官型培养中使用的胶原的种属来源可能会影响上皮细胞分化为肺泡或导管结构以及上皮分支的模式。这些观察结果强调了在 3D 基质中构建分支器官和解释其在组织表型中的作用时，考虑胶原的种属来源和纤维排列特性的重要性。
