Laminins in osteogenic differentiation and pluripotency maintenance

Extracellular matrix (ECM) plays an integral role in different developmental stages and in multiple systems. However, due to ECM being composed of various extracellular components (growth factors, cytokines, and hormones), its innate complexity and the lack of any efficient purification techniques limit further research into the detailed mechanisms of its role in cellular activities. Laminin (LN), a synthetic recombinant basement membrane protein, can solve the above problems as it is a critical component of ECM and can be completely and reproducibly chemically defined. This article summarizes the functions and mechanisms of LN during osteogenic differentiation and stemness maintenance. LN-111 enhances osteogenic differentiation of mesenchymal stem cells (MSCs) and bone marrow progenitor cells (BMPCs) via the ECM receptor integrin-α1, αV, α6, and β1. LN-332 stimulates osteogenic differentiation of MSCs and bone-marrow-derived MSCs (BMSCs) by α3β1/α3β3 integrin-mediated activation of the focal adhesion kinase (FAK)/extracellular-signal-regulated kinase (ERK), Wnt5a, and bone morphogenic proteins (BMP) signaling pathways. Moreover, LN-111, LN-211, and LN-332 regulate the osteogenic differentiation of dental follicle cells (DFCs) via the integrin-α2/β1 and FAK/ERK signaling pathways. LN-511 and LN-521 can preserve the pluripotency of pluripotent stem cells (PSCs) and human embryonic stem cells (hESCs) via the integrin-α6β1/αVβ1 and the PI3k/Akt pathways. In addition, a variety of laminin fragments such as iMatrix-411; iMatrix-511; bioactive peptide sequences of LN-α2, PPFEGCIWN, and DLTIDDSYWYRI; and LN-332 large globular 3 (LG3), were confirmed to induce osteogenic differentiation. LN511-E8, LN332-E8 fragments, and the laminin-mimicking sequence YIGSR sustain stemness. LN may have potential applications in surface gene markers, xeno-free cultures, and enhancing the expression of osteogenic factors.