Osteoblastic cell responses to zoledronate treatment in-vitro: A systematic review

BACKGROUND: Zoledronate (ZOL), a potent nitrogen-containing bisphosphonate (BP), is widely prescribed for osteoporosis and metastatic bone disease. While osteoclast inhibition is central to ZOL's therapeutic action and to the pathophysiology of medication-related osteonecrosis of the jaw (MRONJ), less is known about its direct effects on osteoblasts. Understanding dose- and time-dependent osteoblastic responses is essential for improving in-vitro modelling and informing regenerative strategies. METHODS: We performed a systematic review of in-vitro studies reporting osteoblastic responses to ZOL, adhering to PRISMA guidelines (protocol registered, DOI:10.17605/OSF.IO/GWDP5). Web of Science and Scopus searches identified 606 records, of which 77 met inclusion criteria. Data were extracted for proliferation, metabolic activity, apoptosis, alkaline phosphatase (ALP), biomineralisation, collagen formation, and angiogenesis. Statistical comparisons assessed dose- and time-dependent effects. RESULTS: Across 2057 datapoints, undesirable outcomes (reduced metabolic activity or proliferation, increased apoptosis) occurred at median [ZOL] of 10 μM, significantly higher (p≤0.0001) than concentrations associated with no effect (1 μM) or beneficial responses (0.75 μM). Desirable nanomolar-dose outcomes were infrequent and inconsistent across studies. ALP and biomineralisation were dose-dependently impaired, whereas collagen synthesis was unaffected. At 48-71 h, osteoblasts tolerated higher ZOL concentrations compared to later timepoints (p≤0.05). Media composition influenced responses, with higher calcium (≥1.8 mM) media protective of negative effects, likely due to ZOL-Ca complex formation. CONCLUSION: ZOL exerts direct, dose-dependent inhibitory effects on osteoblasts in-vitro, with outcomes influenced by exposure time and media composition. This review highlights the need for standardised protocols and provides quantitative guidance for modelling MRONJ and testing regenerative interventions.