Tissue remodeling is the reorganization or renovation of existing
tissues. Tissue remodeling can be either physiological or pathological. The process can either change the characteristics of a tissue such as in
blood vessel remodeling, or result in the
dynamic equilibrium of a tissue such as in
bone remodeling.
Macrophages repair wounds and remodel tissue by producing
extracellular matrix and
proteases to modify that specific matrix.[1]
A
myocardial infarction induces tissue remodeling of the heart in a three-phase process:
inflammation,
proliferation, and maturation. Inflammation is characterized by massive
necrosis in the infarcted area. Inflammatory cells clear the dead cells. In the proliferation phase, inflammatory cells die by
apoptosis, being replaced by
myofibroblasts which produce large amounts of
collagen. In the maturation phase, myofibroblast numbers are reduced by apoptosis, allowing for infiltration by
endothelial cells (for blood vessels) and
cardiomyocytes (heart tissue cells). Usually, however, much of the tissue remodeling is pathological, resulting in a large amount of
fibrous tissue.[2] By contrast,
aerobic exercise can produce beneficial cardiac tissue remodeling in those suffering from
left ventricular hypertrophy.[3]
In a brain
stroke the
penumbra area surrounding the
ischemic event initially undergoes a damaging remodeling, but later transitions to a tissue remodeling characterized by repair.[5]
Vascular remodeling refers to a compensatory change in blood vessel walls due to plaque growth. Vascular expansion is called positive remodeling, whereas vascular constriction is called negative remodeling.[6]
Tissue remodeling occurs in
adipose tissue with increased body fat.[7] In obese subjects, this remodeling is often pathological, characterized by excessive inflammation and fibrosis.[8]