RÉSUMÉ
BACKGROUND:Tendinopathy is a musculoskeletal disorder characterized by pain and decreased mobility,with pathological changes of disturbed collagen and hyperplasia of the vasculature.Tendinopathy tends to occur in athletes,physical workers,and the elderly.One of the mechanisms of tendinopathy is the"failed healing response",and part of what causes the failed healing response is the erroneous differentiation of tendon stem/progenitor cells. OBJECTIVE:By reviewing the relevant literature,we introduce the characteristics of tendon stem/progenitor cells,summarize the factors that affect the differentiation of tendon stem/progenitor cells to tendon cells and those that lead to mis-differentiation of tendon stem/progenitor cells(differentiation to adipocytes,osteocytes and chondrocytes),and also describe the limitations of tendon stem/progenitor cells in clinical applications. METHODS:PubMed and Web of Science databases were searched for the terms"tendon stem/progenitor cells,tendinopathy,tendon injury,differentiation".The relevant literature was screened by reading and 109 articles were included for the analysis of the results. RESULTS AND CONCLUSION:(1)Tendon stem/progenitor cells are a type of stem cells that can spontaneously differentiate into tendons and have the ability to self-renew,clone,and multi-differentiate.Various external conditions acting on tendon stem/progenitor cells can lead them to differentiate in diverse directions.The specific factors that regulate the fate of tendon stem/progenitor cells are not known with certainty.When stem cell renewal and differentiation in tendons becomes abnormal,it can lead to failure of tendon healing and consequently to tendinopathy.(2)Aging,changes in extracellular matrix composition,excessive mechanical stimulation,prostaglandin E2 and interleukin-6 as well as interleukin-10 and some systemic diseases may be important in regulating the mis-differentiation of tendon stem/progenitor cells.(3)Possible favorable factors that promote the differentiation of tendon stem/progenitor cells to tenocytes are:some growth factors and cytokines,moderate mechanical stimulation and topography of the extracellular matrix,low oxygen tension,drugs,and several transcriptional genes and proteins.(4)The most desirable therapeutic tools are the regulation of endogenous tendon stem/progenitor cells or the stimulation of endogenous tendon stem/progenitor cell proliferation and differentiation by exogenous tendon stem/progenitor cells.(5)Understanding the factors that regulate mis-differentiation of tendon stem/progenitor cells may provide insight into the pathogenesis of tendinopathy and identify therapeutic targets.Elaborating on the induction of tendon stem/progenitor cell differentiation into tendons could facilitate their use in tissue engineering.
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Objective:To analyze the effects of a novel type of polydopamine (PDA)-coated porous titanium alloy scaffolds loaded with zoledronic acid-gelatin nanoparticles (ZOL-GNPs) for topical sustained drug release on osteoclasts in vitro. Methods:After porous titanium alloy scaffolds were fabricated using electron beam melting technique and ZOL-GNPs with different ZOL concentrations (0, 1, 10, 50, 100, 500 μmol/L) were prepared by desolvation method, PDA-coated porous titanium alloy scaffolds loaded with ZOL-GNPs were constructed by combining the two. The characteristics of the scaffolds were analyzed. The biomechanics of 3 different scaffolds (bare porous titanium alloy scaffolds, PDA-coated porous titanium alloy scaffolds, and PDA-coated porous titanium alloy scaffolds loaded with ZOL-GNPs) were investigated. Drug release detection was carried out by high performance liquid chromatography on the 1st, 4th, 7th, 14th, 21st, and 28th days respectively. The osteoclasts were inoculated into the novel scaffolds with different ZOL concentrations. The expression of osteoclast-related genes was detected by real-time quantitative (RT)-polymerase chain reaction (PCR); the expression of osteoclast-related proteins was detected by Western-blot.Results:The PDA-coated porous titanium alloy scaffolds loaded with ZOL-GNPs were successfully constructed. Electron microscope scanning showed that the GNPs were well spheroidized, smooth in surface, and uniformly dispersed, with a particle size of (243.6±63.4) nm. The ZOL-GNPs were uniformly compounded on the surface and in the pores of the scaffolds, and the spheres were regular in shape with no adhesion. The biomechanical experiments showed that the elastic moduli of the porous titanium alloy scaffolds under 3 different conditions were (1.81±0.12) GPa, (1.80±0.23) GPa and (1.81±0.15) GPa, showing no significant difference ( P> 0.05). The drug release percentage in the porous titanium alloy scaffolds was obviously high on the first day, and increased gradually and slowly in the subsequent 27 days. In the scaffolds with a low concentration ZOL, more osteoclasts adhered and proliferated; in the 50 μmol/L scaffolds, spheroid cells appeared; the spheroid cells increased and even apoptosis occurred with an increase in the ZOL concentration. RT-PCR showed that the expression of Ctsk gene and TRAP gene increased with the increased ZOL concentration, peaked in the 50 μmol/L scaffolds, and then decreased with the increased concentration, showing statistically significant differences ( P < 0.05). Western-blot showed that the expression pattern of Ctsk and TRAP was similar to that of their related genes. Conclusions:The novel PDA-coated porous titanium alloy scaffolds loaded with ZOL-GNPs demonstrate good mechanical properties and an anti-osteoporosis effect via their topical sustained drug release. The scaffolds with a ZOL concentration of 50 μmol/L may exert the best effect on inhibition of osteoclasts.
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Objective To optimize the helicopter pilot helmet with mounted display in order to enhance wearing comfort.Methods The problems of the helmet were analyzed,and the trends of the helmet were discussed in foreign countries and China,and then optimization was carried out from the aspects of function,structure,design,material and etc.Results Optimization measures were proposed from the aspects of safety protection,ergonomics,platform display,night vision,tracking and positioning,material and industrial art to improve the designs of all functional modules of the helmet.Theoretical references were provided for the design of lightweight and tailored helmet.Conclusion Aviation ergonomics has to be considered to enhance wearing comfort and reliability when designing new-type helicopter pilot helmet with mounted display.