The invention features a method for generating new tissue by obtaining a
liquid hydrogel-cell composition including a hydrogel and tissue
precursor cells; delivering the liquid hydrogel-cell composition into a
permeable, biocompatible support structure; and allowing the liquid
hydrogel-cell composition to solidify within the support structure and
the tissue precursor cells to grow and generate new tissue. The invention
also features a tissue forming structure including a permeable,
biocompatible support structure having a predetermined shape that
corresponds to the shape of desired tissue; and a hydrogel-cell
composition at least partially filling the support structure, wherein the
hydrogel-cell composition includes a hydrogel and tissue precursor cells.
The new tissue forming structure can be used in new methods to generate
various tissues (e.g., to treat defective tissue) including new bone,
cartilage, and nervous tissue such as spinal cord tissue. The invention
also new isolated nervous system stem cells.