For example, osteobridging protein (OPN) research has shown that OPN can facilitate cell adhesion, migration, and survival in human optic nerve head astrocytes by interacting with cell surface receptors like Integrin αV, Integrin β3, Integrin β5, and the non-integrin receptor CD44. These findings imply that OPN may play a significant neuroprotective role in glaucoma development (Neumann et al., 2014). Here, CD44 is linked to glaucoma.