[Establishment of A Mixed Chimeric Mouse Model of Allogeneic Bone Marrow Transplantation and Its Influencing Factors].

OBJECTIVE: To establish a mouse mixed chimerism (MC) model of nonmyeloablative allogeneic bone marrow transplantation(allo-BMT) and explore its affecting factors. METHODS: The MC model was established by nonmyeloablative allo-BMT followed by high-dose post-transplant cyclophosphamide (PTCY). 123 mice in the experiments was retrospectively analyzed, and the factors related with the chimerism were explored with the univariate and multivariate logistic regression analysis. A multivariate linear regression was performed by R project to obtain a mathematical model for predicting the chimeric level with relevant affecting factors. RESULTS: The model presented mixed chimerism on day 14 after transplantation, and was characterized by a donor lymphocyte infusion (DLI) which significantly promoted donor engraftment on day 15, but transfplantation of PBS in control group was failed. Among 123 mice, 47 (38.21%) mice were MC, while 76 (61.79%) mice were non-MC in 123 mice, respectively; univariate analysis showed that the baseline body weight of mice (P=0.001, 17.84±1.19 g vs 18.50±0.94 g), total body irradiation(TBI，P=0.048) and the using of cyclophosphamide (P=0.16) were affected the chimeric state of mice, while the number of infusing cells and the time of detection showed no significant effects. Multivariate regression analysis showed that under certain conditions, the body weight of mice on day 0 was an independent factor affecting chimeric levels (OR=0.493, 95% CI 0.307-0.791, P=0.003). Through R project multiple linear regression, the math model was achieved, which was chimerism=6.09-12×weight(g)+80.03×TBI(Gy)-4.4×cell-counts (× 107) +0.38×CTX (mg/kg), R2=0.5841, P<0.001. CONCLUSION: The experiment presents a method for establishing a mixed chimeric mice model after non-myeloablative bone marrow transplantation and constructs a mathematical model with relevant factors affected chimerism status.

Characterization and Function of a Novel Welan Gum Lyase From Marine Sphingomonas sp. WG.

Welan gum, a kind of microbial exopolysaccharides, produced by the genus Sphingomonas, have great potential for application in many fields, such as the food industry, cement production, and enhanced oil recovery. But there are still challenges to reduce the cost, enhance the production and the quality. Herein, the bioinformatics analysis of WelR gene was preformed, and the characterization and function of WelR, welan gum lyase, from Sphingomonas sp. WG were investigated for the first time. The results indicated that 382nd (Asn), 383rd (Met), 494th (Asn), and 568th (Glu) were the key amino acid residues, and C-terminal amino acids were essential to keeping the stability of WelR. The optimal temperature and pH of the enzymatic activity were found to be 25°C and 7.4, respectively. And WelR was good low temperature resistance and alkali resistant. K+, Mg2+, Ca2+, Mn2+, and EDTA increased WelR activities, in contrast to Zn2+. Coupled with the change in glucose concentration and growth profile, the qRT-PCR results indicated that WelR may degrade welan gum existing in the culture to maintain bacterial metabolism when glucose was depleted. This work will lay a theoretical foundation to establish new strategies for the regulation of welan gum biosynthesis.