Primary Radiation Stress, Inflammatory Reaction and the Mechanism of Early Postradiation Reparative Processes in Irradiated Tissues

The products of radiolysis released from cellular compartment under the influence of ionizing radiation: highly mobile groups of proteins, damaged nuclear and mitochondrial DNA, extracellular ATP and oxidized low density lipoproteins, cause stress activation in irradiated tissues through a pattern of the receptors with start of the cascade r53 and NF-κB of pro-inflammatory ways conducting to an expression of pro-inflammatory genes stimulating synthesis of cytokines of the IL-1 family. Excessive activation of pro-inflammatory way under the influence of a radioactive stress is limited to synthesis, anti-inflammatory cytokines: IL-4, IL-10, IL-11, IL-13 and also antagonists of IL-1 receptor and TGF-β. G-CSF and MG-CSF induced by action of pro-inflammatory cytokines have anti-inflammatory and anti-apoptotic properties decreasing level of pro-inflammatory cytokines IL-6 and TNF. Glucocorticoids participate in regulation of primary radioactive stress, suppressing an excessive expression of genes of pro-inflammatory cytokines. Increased IL-1 level stimulates secretion of corticosteroids through mechanism of feedback. Adrenergic stimulation is capable to raise a gene IL-1β expression. The mechanism of radiation apoptosis of stem cells is implemented through p53-Puma way which blocks interaction anti-apoptotic proteins of Bcl-2 with pro-apoptotic proteins of Bax and Bak. After release from mitochondrion of cytochrome C and apoptosis-inducing factor there is an activation of effector caspases: caspases 3, 6 and 7 through caspase 9, and final cell destruction. Wnt way is crucial for post-radiation repair. Potential of the regenerative response of hemopoietic tissue to radiation injury depends on catenin and ability of Wnt way to stimulate post-radiation bone marrow reparation. Mesenchymal stem cells of bone marrow play a large role in post-radiation regeneration of hemopoietic tissue. Their main action is carried out through TLR2 and TLR4 receptors. Mobilization of hemopoietic stem cells is bound to release proteases from bone marrow, including neutrophil elastase and cathepsin G, and a matrix metalproteinase-9. Radioprotective properties of exogenous IL-1 aren’t limited only by induction of raised G-CSF and GM-CSF production. The larger role in radiation protection is played by the reaction induced by IL-1 in the form of feedback with production anti-apoptotic and anti-inflammatory factors. Primary radioactive stress limits time of radiomitigable effect of IL-1 by 1-2 h after its application after radiation.

Preparation of HA-Coated Mg-4.0Zn-1.0Ca-0.6Zr(wt%) Alloy and its Biodegradation Behaviors

Magnesium and magnesium alloys, as biomaterials, possess many properties that are superior to those of other metals. However, magnesium and magnesium alloys have strong chemical activity and porous and brittle surface oxide film, as degradable implantation materials, their degradation rates are too fast. Hydroxyapatite (HA) has good biocompatibility and biological activity and has become one of the replacement materials of biomedical stiff hemopoietic tissue, but the application of HA biomaterial is hindered because HA is brittle and has low strength. Integrating good mechanical properties of metallic materials with excellent biological performance of HA, the composite obtained by coating HA to the surface of metallic matrix is ideal rehabilitation material of bone tissue. In the present study, a new Mg-4.0Zn-1.0Ca-0.6Zr (wt%) was designed according to the requirements of biocompatibility. The microstructures and the mechanical properties of the new alloy were investigated by experiment. The excellent mechanical properties fully meet the service requirements of human bone tissue for mechanical property. Flat and dense hydroxyapatite coating was prepared on the surface of magnesium alloy matrix by preceding alkali heat treatment, electrodeposition and post alkali heat treatment. The Structure and constituent of HA coating and the biodegradation behavior of HA-coated Mg-4.0Zn-1.0Ca-0.6Zr (wt%) alloy were evaluated. Resuls showed that the degradation rate of HA-coated Mg-4.0Zn-1.0Ca-0.6Zr (wt%) alloy in SBF biomimetic solution decreased obviously and tended to be stable after 10 days. As degradable implantation materials, HA-coated Mg-4.0Zn-1.0Ca-0.6Zr (wt%) alloy fully meets the service requirements of human bone tissue.

Lumbar nerve root compression due to extramedullary hemopoiesis in a patient with thalassemia: complete clinical regression with radiation therapy

✓The authors describe the case of a 24-year-old woman who had a history of β-thalassemia and presented with severe symptoms of lumbar nerve root compression due to extramedullary hemopoiesis in the intervertebral foramen. Radiation therapy (2000 cGy in six fractions) was delivered to the mass. The patient’s neurological symptoms completely resolved following treatment. Follow-up images showed a reduction in lesion size. The results of this unique case supported by a review of the literature suggest that radiation therapy alone is an effective modality in the treatment of patients with compression of neural structures due to extramedullary hemopoietic tissue.