Effect Of Radiation On Collagen Type Ⅰ MRNA Expressions In Mouse Osteoblast In Vitro And The Influence Of Irradiation-damaged Osteoblasts On Osteoclasts

Plenty of studies proved that bone tissue is very sensitive to radiation and radiation cause bone damage. This research explored the effect of radiation on Collagen type I mRNA expressions in mouse osteoblasts in vitro and the influence of irradiated osteoblasts on osteoclasts in molecular biology.We studied the changes of expression of collagen type Ⅰ in osteoblasts after radiation. Mouse bone marrows were isolated and bone marrow stromal cells were induced into osteoblasts in Vitro. The characterization was indentified. For example, the observation of cell phenotype、ALP staining, and so on. The result showed that bone marrow stromal cells were differentiated into osteoblasts under the effect of the induced medium. Osteoblasts were divided into the early and the late osteoblasts according to culture stages. RNA was isolated from osteoblast, reverse-transcribed into cDNA, and qPCR was used to analyze the expression of Collagen type Ⅰ in early and late osteoblasts, which were irradiated by1-4Gy. From above, we revealed the effect of radiation on the osteoblasts’capacity to secret Collagen type Ⅰ.The result demonstrated that compared to contronl group, gene expression of Collagen type Ⅰ increased in the early ostoblast after1-3Gy radiation (P<0.05) and decreased in the late osteoblast that cultured10days; Collagen type Ⅰ gene expressions in the late ostoblast after4Gy irradiation greatly higher than in the early osteoblast (P<0.01). Taken together, after1-3Gy irradiation, the early osteoblast enhanced collagen type I expression and the ability of bone formation. The late osteoblast exposure of1-3Gy decreased collagen type Ⅰ expression and weakened the ability of bone formation. The result of collagen type I high expression in late osteoblast after4Gy irradiation may be manifestation of compensatory function.At the same time, we also explored the effect of irradiation-damaged osteoblasts on the growth and function of osteoclasts in later experiment. Under normal circumstances, the process of bone turnover relies on the interaction between osteoblasts and osteoclasts, leading to the balance between bone absorption and formation. The disbalance of function and numbers in osteoclasts and osteoblasts will lead to abnormalities of skeletal shape and structure in bone. We have done pilot observation on the regulation of irradiated osteoblasts on the function of osteoclasts.RAW264.7cell line was adopted as osteoclast precursors. RAW264.7cells were cultured by the supernate of irradiated osteoblasts. RAW264.7cells clones were analyzed to estimate the ability of proliferation in RAW264.7cells. Real-time polymerase chain reaction was adopted to test the expression of TRAP、RANK as well as Notch-2.Our result showed RAW264.7cells, which was cultured by supernate of irradiation-injured osteoblasts, formed less number of clones with the increase of the radiation dose imposed on osteobalsts; Compared with control group, the expression of varied genes in RAW264.7cells decreased significantly (p<0.01). Therefore, it is likely that the supernate of irradiation-damaged osteoblasts has an inhibitory effect on the growth and differentiation of osteoclast precursors through several signal pathways.In conclusion, this research helps us with understanding the regulating mechnism of osteoblasts to osteoclasts under radiation. Making us further understand that bone formation and resorption play critical role in bone remodeling.