Fabrication of strontium Eucommia ulmoides polysaccharides and in vitro evaluation of their osteoimmunomodulatory property.

The osteoimmune environment plays indispensable roles in bone regeneration because it determines subsequent osteogenesis and osseointegration. Eucommia ulmoides polysaccharide (EUP) was proved to be an effective biomaterial that has immunomodulatory effects for improving the biomechanical quality of bone. Strontium is a trace element that inhibits inflammation and promotes bone growth. To develop a novel EUP-based osteoimmunomodulatory biomaterial with potentially enhanced bone regeneration, we synthesized strontium Eucommia ulmoides polysaccharides (EUP-Sr) and evaluated its morphology, structure and thermal stability. The materials characterization results confirmed that strontium was successfully introduced into the EUP and formed a new complex with thermal-stable property. The cytocompatibility evaluation of different concentrations of EUP-Sr by CCK8 assay suggested that EUP-Sr is beneficial to the macrophages proliferation. We further evaluated the gene expressions of RAW 264.7 cells treated with EUP-Sr. It was found that EUP-Sr could suppress inflammatory factors and osteoclastogenesis, and enhance the expressions of osteogenic factors of RAW 264.7 cells. Therefore, EUP-Sr should be a promising bioactive compound with the capability to create a positive pro-regenerative environment for skeleton tissue engineering.

Elastic modulus and migration capability of drug treated leukemia cells K562.

Leukemia is a commonly seen disease caused by abnormal differentiation of hematopoietic stem cells and blasting in bone marrow. Despite drugs are used to treat the disease clinically, the influence of these drugs on leukemia cells' biomechanical properties, which are closely related to complications like leukostasis or infiltration, is still unclear. Due to non-adherent and viscoelastic nature of leukemia cells, accurate measurement of their elastic modulus is still a challenging issue. In this study, we adopted rate-jump method together with optical tweezers indentation to accurately measure elastic modulus of leukemia cells K562 after phorbol 12-myristate 13-acetate (PMA), all-trans retinoic acid (ATRA), Cytoxan (CTX), and Dexamethasone (DEX) treatment, respectively. We found that compared to control sample, K562 cells treated by PMA showed nearly a threefold increase in elastic modulus. Transwell experiment results suggested that the K562 cells treated with PMA have the lowest migration capability. Besides, it was shown that the cytoskeleton protein gene α-tubulin and vimentin have a significant increase in expression after PMA treatment by qPCR. The results indicate that PMA has a significant influence on protein expression, stiffness, and migration ability of the leukemia cell K562, and may also play an important role in the leukostasis in leukemia.