Osteogenic Effects of IL-12 on Bone Marrow Mesenchymal Stem Cells Facilitates Its Irradiation Hematopoiesis Recovery

Background Impaired osteogenesis differentiation of bone marrow mesenchymal stem cells (BM-MSCs) results inefficient physical supporting of hematopoietic niche and further counts against hematopoiesis recovery in radiotherapy. Interleukin-12 (IL-12) holds facilitations on acute irradiation hematopoietic recovery, but the mechanisms remain to be clarifiedAim To investigated the osteogenic effects of IL-12 on BM-MSCs and the relationship between IL-12’s osteogenic effects of BM-MSCs and its hematopoietic supportive role.Methold The osteogenic effects of IL-12 in vivo were investigated by estimating the osteoblasts in femurs of Balb/c mice after 5 Gy 60 Co-γ irradiation, and the osteogenic effects of IL-12 in vitro were investigated by analyzing the osteogentic genes and calcium mineral deposits formations in BM-MSCs after 9 Gy 60 Co-γirradaition at different times of co-culturing with IL-12 in osteogenic induction medium. For the latter, the special siRNA of IL-12 receptor 1 (IL-12Rβ1), tyrosine kinase 2 (TYK2) and the inhibitor of signal transducer and activator of transcription3 (STAT3) were used to explore the possible mechanism. The bone marrow hematopoietic supportive role of cells co-cultured with IL-12 were also investigated by analyzing the clone-forming of hematopoietic progenitor/ stem cells (HSPCs).Results Interleukin-12 (IL-12) holds facilitaties on acute irradiation-induced hematopoietic and osteogenesis damages in Balb/c mice. IL-12 also promoted osteogenesis differentiation of irradiated BM-MSCs, and for that, especially during early period after irradiation, the IL-12 receptor 1 (IL-12Rβ1)/ tyrosine kinase 2 (TYK2)/ signal transducer and activator of transcription3 (STAT3) signaling played a crucial role. That was reflected by obvious synchronicity between the upregulation time of IL-12Rβ1 and the time of the better IL-12 induced osteogenesis of BM-MSCs. The more osteogenic genes expressions and more calcium mineral deposits formations in BM-MSCs were obtained in cells co-cultured with IL-12 within 1 hour after irradiation; Beside that IL-12 increased the phosphotyrosine of STAT 3 (p-STAT3) which along with IL-12 induced osteogenesis promotions were abrogated by using IL-12Rβ1 and Tyk2 silencing RNA (siRNA) or inhibitor of STAT3. Further, the clone-forming of hematopoietic progenitor/ stem cells (HSPCs) showed much better in IL-12-BM-MSCs transplanted femurs of irradiated mice than that of BM-MSCs, even cells were co-cultured with IL-12 for only 24 hours.Conclusion IL-12 may assist hematopoiesis recovery through its early osteogenic differentiation promotion of BM-MSCs after irradiation, which suggested potential therapeutic targets of bone marrow hematopoietic damages after radiotherapy.