Progranulin is essential for bone homeostasis and immunology

Intercellular communication or crosstalk between immune and skeletal cells is considered a crucial element in bone homeostasis modulation. Progranulin (PGRN) is an autocrine growth factor that is structured as beads-on-a-string and participates in multiple pathophysiological processes, including atherosclerosis, arthritis, neurodegenerative pathologies, cancer, and wound repair. PGRN functions as a competitor that binds to tumor necrosis factor receptor 1 (TNFR1), thereby blocking the TNF-α pathway. PGRN is regarded as an agonist of chondrogenesis and osteogenesis, delaying the progression of inflammation through the TNFR2 pathway. The exploitation of PGRN may bring benefits for inflammatory bone diseases and the stabilization of bone homeostasis. The PGRN-modified analog Atsttrin possesses three TNFR-binding fragments and thereby exerts superior therapeutic effects on multiple preclinical animal models compared to PGRN. In this review, we highlight the emerging roles of PGRN in bone formation, as well as in physiological and TNF-α-mediated inflammatory conditions revealed in recent discoveries. We address potential therapies for the treatment of inflammatory bone conditions, such as periodontitis, by the use of PGRN and its derivative Atsttrin.