hE-cadherin-Fc fusion protein coated surface enhances the adhesion and proliferation of human mesenchymal stem cells.

A fusion protein consisting of human E-cadherin extracellular domain and the immunoglobulin G Fc region (hE-cadherin-Fc) was prepared and used as a cell-cell adhesion biomimicking matrix for the in vitro expansion of human mesenchymal stem cells (hMSCs) for use in regenerative medicine. The hE-cadherin-Fc was stably immobilized onto a polystyrene plate due to the hydrophobicity of the Fc domain, enhancing the surface wettability and topography of the plate. The hE-cadherin-Fc matrix markedly promoted the cell adhesion and proliferation of hMSCs compared with the tissue culture-treated plate (TC-PS) and the gelatin-coated plate. Furthermore, the expanded hMSCs on the hE-cadherin-Fc were positive for CD105, similar to those from the gelatin. Additionally, the expression of E-cadherin and ß-catenin in the hMSCs was improved on the hE-cadherin-Fc matrix, suggesting that the interactions of the hE-cadherin-Fc matrix with the hMSCs were substitutes for the cell-cell adhesion junctions during the initial culture stage in the absence of intercellular interactions. The hE-cadherin-Fc was shown to be a promising artificial ECM for the in vitro expansion of hMSCs.

Astaxanthin biosynthesis is enhanced by high carotenogenic gene expression and decrease of fatty acids and ergosterol in a Phaffia rhodozyma mutant strain.

An astaxanthin-overproducing (∼1000 µg g(-1)) strain of Phaffia rhodozyma, termed MK19, was established through 1-methyl-3-nitro-1-nitrosoguanidine and Co60 mutagenesis from wild-type JCM9042 (merely 35-67 µg g(-1)). The total fatty acid content of MK19 was much lower than that of the wild type. Possible causes of the astaxanthin increase were studied at the gene expression level. The expression of the carotenogenic genes crtE, crtI, pbs, and ast, which are responsible for astaxanthin biosynthesis from geranylgeranyl pyrophosphate, was highly induced at the mRNA level, leading to excessive astaxanthin accumulation. In contrast, transcription levels of the genes (hmgs, hmgr, idi, mvk, mpd, fps), responsible for the initial steps in the terpenoid pathway, were essentially the same in wild type and MK19. Although fatty acid and total ergosterol content were reduced by 40-70 mg g(-1) and 760.3 µg g(-1) , respectively, in MK19 as compared with the wild type, but the transcription levels of rate-limiting genes in fatty acid and ergosterol pathways such as acc and sqs were similar. Because fatty acids and ergosterol are two branch pathways of astaxanthin biosynthesis in P. rhodozyma, our findings indicate that enhancement of astaxanthin in MK19 results from decreased fatty acid and ergosterol biosynthesis, leading to precursor accumulation, and transfer to the astaxanthin pathway. Strengthening of the mevalonate pathway is suggested as a promising metabolic engineering approach for further astaxanthin enhancement in MK19.