  We develop a microscopic biophysical model for self-organization and
reshaping of artificial tissue, that is co-driven by microscopic active forces
between cells and extracellular matrix (ECM), and macroscopic forces that
develop within the tissue, finding close agreement with experiment. Microscopic
active forces are stimulated by $\mu$m scale interactions between cells and the
ECM within which they exist, and when large numbers of cells act together these
forces drive, and are affected by, macroscopic-scale self-organization and
reshaping of tissues in a feedback loop. To understand this loop, there is a
need to: (1) construct microscopic biophysical models that can simulate these
processes for the very large number of cells found in tissues; (2) validate and
calibrate those models against experimental data; and (3) understand the active
feedback between cells and the extracellular matrix, and its relationship to
macroscopic self-organization and reshaping of tissue. Our microscopic
biophysical model consists of a contractile network representing the ECM, that
interacts with a large number of cells via dipole forces, to describe
macroscopic self-organization and reshaping of tissue. We solve the model using
simulated annealing, finding close agreement with experiments on artificial
neural tissue. We discuss calibration of model parameters. We conclude that
feedback between microscopic cell-ECM dipole interactions and tissue-scale
forces, is a key factor in driving macroscopic self-organization and reshaping
of tissue. We discuss application of the biophysical model to simulation and
rational design of artificial tissues.
