Research Progress on Stem Cell Therapies for Articular Cartilage Regeneration

Figure 1

Two theories of articular cartilage regeneration involving stem cells. (a) Stem cell differentiation theory. Stem cells are affected by the microenvironment and directly differentiate into chondrocytes. (b) Paracrine theory of stem cells. Stem cells are affected by the microenvironment and secrete various derivatives, including growth factors, EVs, and ECM. These derivatives have been proven to induce homing of endogenous stem cells, promote the differentiation of endogenous stem cells into chondrocytes, promote the proliferation of chondrocytes, induce macrophages to polarize to the M2 type, and regulate the level of inflammatory factors to exert anti-inflammatory effects. EVs: extracellular vesicles; ECM: extracellular matrix.