Comparison of the degradation behavior of PLGA scaffolds in micro-channel, shaking, and static conditions.

Degradation of scaffolds is an important problem in tissue regeneration management. This paper reports a comparative study on degradation of the printed 3D poly (lactic-co-glycolic acid) scaffold under three conditions, namely, micro-channel, incubator static, and incubator shaking in the phosphate buffer saline (PBS) solution. In the case of the micro-channel condition, the solution was circulated. The following attributes of the scaffold and the solution were measured, including the mass or weight loss, water uptake, morphological and structural changes, and porosity change of the scaffold and the pH value of the PBS solution. In addition, shear stress in the scaffold under the micro-channel condition at the initial time was calculated with Computational Fluid Dynamics (CFD) to see how the shear stress factor may affect the morphological change of the scaffold. The results showed that the aforementioned attributes in the condition of the micro-channel were significantly different from the other two conditions. The mechanisms that account for the results were proposed. The reasons behind the results were explored. The main contributions of the study were (1) new observations of the degradation behavior of the scaffold under the micro-channel condition compared with the conditions of incubator static and incubator shaking along with underlying reasons, (2) new understanding of the role of the shear stress in the scaffold under the condition of the micro-channel to the morphological change of the scaffold, and (3) new understanding of interactions among the attributes pertinent to scaffold degradation, such as weight loss, water uptake, pH value, porosity change, and morphological change. This study sheds important light on the scaffold degradation to be controlled more precisely.

Tyrosinase-doped bioink for 3D bioprinting of living skin constructs.

Three-dimensional bioprinting is an emerging technology for fabricating living 3D constructs, and it has shown great promise in tissue engineering. Bioinks are scaffold materials mixed with cells used by 3D bioprinting to form a required cell-laden structure. In this paper, a novel bioink made of gelatin methacrylamide (GelMA) and collagen (Col) doped with tyrosinase (Ty) is presented for the 3D bioprinting of living skin tissues. Ty has the dual function of being an essential bioactive compound in the skin regeneration process and also as an enzyme to facilitate the crosslink of Col and GelMA. Further, enzyme crosslinking together with photocrosslinking can enhance the mechanical strength of the bioink. The experimental results show that the bioink is able to form stable 3D living constructs using the 3D bioprinting process. The cell culture shows that three major cell lines: human melanocytes (HEM), human keratinocytes (HaCat) and human dermal fibroblasts (HDF) exhibit high cell viabilities. The viability of these three cell lines is above 90%. The proliferation and scratching test show that Ty can enhance the proliferation of HEM, inhibit the growth and migration of HDF and not affect HaCat significantly. Animal tests show that the doped bioinks for 3D bioprinting can help form an epidermis and dermis, and thus have high potential as a skin bioink.

Association of apolipoprotein A5 gene polymorphisms and serum lipid levels.

BACKGROUND AND AIMS: Apolipoprotein (APO) A5 gene polymorphisms have been associated with increased plasma triglyceride (TG), but the results are inconsistent. The present study was undertaken to detect the APOA5 gene polymorphisms and their associations with lipid profiles in the Guangxi Hei Yi Zhuang and Han populations. METHODS AND RESULTS: Genotyping of the APOA5 -1131T>C, c.553G>T and c.457G>A was performed in 490 subjects of Hei Yi Zhuang and 540 participants of Han Chinese aged 15-89 years. The -1131C allele frequency was higher in high total cholesterol (TC) than in normal TC subgroups in both the ethnic groups (P<0.05). The c.553T allele frequency was higher in high TG than in normal TG subgroups (P<0.01), in high APOB than in normal APOB subgroups in Hei Yi Zhuang (P<0.05), or in females than in males in Han (P<0.01). The c.457A allele frequency in Han was higher in high TG than in normal TG subgroups, in low APOA1 than in normal APOA1 subgroups, in males than in females, or in normal APOB than in high APOB subgroups (P<0.05-0.01). The levels of TC, low-density lipoprotein cholesterol and APOB in Hei Yi Zhuang were correlated with -1131T>C genotype or allele, and the levels of TG were associated with c.553G>T genotype (P<0.05). The levels of TG, APOA1 and APOB in Han were correlated with c.457G>A genotype or allele, and the levels of TC were associated with -1131T>C allele (P<0.05). CONCLUSIONS: The differences in the lipid profiles between the two ethnic groups might partly result from different APOA5 gene-environmental interactions.