Effects of in Vitro α-particle Irradiation on Osteogenic Bone Marrow Cultures

Abstract

Murine bone marrow contains osteogenic precursor cells that undergo differentiation during in vitro cultivation. In vitro these cells are potential target cells for α-irradiation-induced bone tumour formation. Under defined tissue culture conditions these differentiating cells were directly exposed to α-particle irradiation from the radon daughter ²¹⁰Po. Po deposits in soft tissue and it was shown to be associated with marrow cells and with the extracellular marrow tissue formed in vitro. These differentiating marrow cultures showed high sensitivity to α-irradiation. Cell death was observed at ²¹⁰Po concentrations in tissue culture medium (TCM) > 7 Bq ²¹⁰Po/ml. At lower concentrations (between 1 and 5 Bq ²¹⁰Po per ml TCM) proliferation was enhanced as measured by uptake of ³H-thymidine, also differentation was stimulated as measured by alkaline phosphatase activity and incorporation of ³H-proline in newly synthesized collagen. At several times of culture, the association of ²¹⁰Po with the extracellular matrix and cells was measured. These retention data enabled us to calculate the daily α-particle fluence. At 1 Bq ²¹⁰Po present per ml tissue culture, a daily α-particle fluence as low as 3–6 per 1000 cells seemed very efficient in changing the expression of osteogenic differentiation of marrow cells.