  The mechanisms by which organs acquire their functional structure and realize
its maintenance (or homeostasis) over time are still largely unknown. In this
paper, we investigate this question on adipose tissue. Adipose tissue can
represent 20 to 50% of the body weight. Its investigation is key to overcome a
large array of metabolic disorders that heavily strike populations worldwide.
Adipose tissue consists of lobular clusters of adipocytes surrounded by an
organized collagen fiber network. By supplying substrates needed for
adipogenesis, vasculature was believed to induce the regroupment of adipocytes
near capillary extremities. This paper shows that the emergence of these
structures could be explained by simple mechanical interactions between the
adipocytes and the collagen fibers. Our assumption is that the fiber network
resists the pressure induced by the growing adipocytes and forces them to
regroup into clusters. Reciprocally, cell clusters force the fibers to merge
into a well-organized network. We validate this hypothesis by means of a
two-dimensional Individual Based Model (IBM) of interacting adipocytes and
extra-cellular-matrix fiber elements. The model produces structures that
compare quantitatively well to the experimental observations. Our model seems
to indicate that cell clusters could spontaneously emerge as a result of simple
mechanical interactions between cells and fibers and surprisingly, vasculature
is not directly needed for these structures to emerge.
