Influence of Bisphosphonates on HUVEC, Osteoblasts and Fibroblasts in-vitro

Objectives: Different frequencies of bisphosphonate-associated-osteonecrosis-of-the-jaw in relation to the applied bisphosphonate might be associated with the varying degrees of influence on the different cells in the oral cavity. The aim was to evaluate the viability of different cell-types under bisphosphonate-influence in-vitro.

Methods: In an in-vitro study bisphosphonates were added in increasing concentrations (0µmol, 5µmol, 50µmol, 100µmol, 200µmol and 500µmol) to cell-cultures of HUVEC (human-umbilical-vein-endothelial-cells), osteoblasts and fibroblasts. The bisphosphonates used were nitrogen containing bisphosphonates (N-BP): zoledronic acid, pamidronate and ibandronate, as well as the non-nitrogen containing clodronate. After incubation of 2 days for HUVEC and 7 days for osteoblasts and fibroblasts, the MTT-test, a cytotoxicity test, was conducted and the extinction values of the product formazan were measured.

Results: The viability of HUVEC with zoledronate and pamidroante was reduced. All bisphosphonates reduced the viability of osteoblasts. N-BP reduced the viability of fibroblasts. Only very high concentrations of non-nitrogen containing bisphosphonates influenced viability.

concentration [µmol]		0	5	50	100	200	500
HUVEC
	clodronate	1.5	1.4	1.6	1.6	1.5	1.6
	ibandronate	1.5	1.5	1.3	1.4	1.2	1.3
	pamidronate	1.5	1.6	1.1	0.7	0.4	0.6
	zoledronate	1.6	1.4	1.4	1.1	1.1	0.9
fibroblast
	clodronate	1.2	1.1	1.1	1.1	0.9	0.6
	ibandronate	0.9	0.8	0.2	0.03	0.02	0.01
	pamidronate	1.1	0.2	0.03	0.02	0.02	0.01
	zoledroante	1.1	0.9	0.01	0.01	0.01	0.01
osteoblast
	clodronate	0.6	0.5	0.4	0.3	0.2	0.1
	ibandronate	0.6	0.5	0.2	0.1	0.06	0.05
	pamidronate	0.6	0.5	0.1	0.06	0.06	0.06
	zoledronate	0.6	0.3	0.1	0.05	0.01	0.01

Conclusion: Clodronate has a weaker influence on vessel-cells, osteoblasts and fibroblasts. Among the N-BPs, ibandronate has the weakest effect on HUVEC. This might explain that the regeneration after injury is affected in varying degrees depending on the kind of bisphosphonate.