Tissue Development, Repair, and Remodeling - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 687

Sonic Hedgehog

Sonic Hedgehog regulates the progression rather than initiation of airway
branching [ 1394 ]. It inhibits near-tip mesenchymal FGF10 synthesis, hence new
branching in non-allocated loci. Therefore, sonic Hedgehog contributes to the
structural reproducibility.

Wnt

Wnt morphogen uses its canonical pathway to reinforce FGFR2b expression in
epithelial cells [ 1394 ]. On the other hand, non-canonical Wnt5 signaling precludes
FGF10 synthesis.

11.4 Therapeutic Repair

Cell transplantation, gene delivery, and molecule administration are studied to treat
various disorders. In addition, therapeutic strategies are developed either to promote
revascularization of ischemic tissues and regenerate organs or inhibit angiogenesis
in some diseases.
Certain organs and tissues, such as liver and skin, regenerate, but most organs
lack regenerative capacity, hence being unable to repair aging, diseased, and injured
tissues. Heart has a limited intrinsic regenerative capacity. Somatic cells normally
cannot regenerate, except when adequately treated. Tissue stem cells generally have
limited capacity.
Various types of differentiated cell can be generated from embryonic (ESC) or
induced pluripotent stem (iPSC) cells. Moreover, these cell types can be used to
model diseases and optimize therapies. Regenerative medicine aims not only at
stopping progression of degenerative diseases of more or less known pathogenesis,
but also at reversing their course.
In addition to therapies based on stem cells and virus-injected genes, some
strategies rely on locally prolonged administration of growth factors. Intramy-
ocardial injection of self-assembling peptide nanofibers combined with VEGF can
create a microenvironment that can recruit myofibroblasts and cardiomyocyte-like
cells [ 1402 ]. Sustained VEGF release (14 d) improves postinfarct neovasculariza-
tioninrats.

11.4.1 Stem Cells and Regenerative Therapy

Tissue repair and regeneration involve cell interaction over a long time scale to
produce correct cell type, number, location, and function. A successful cell-based