Intermittent induction of LEA peptide by lactose enhances the expression of insecticidal proteins in Bacillus thuringiensis

Cry toxins from Bacillus thuringiensis (Bt) have been extensively applied in agriculture to substitute the use of chemical insecticides. We have previously reported the use of a coexpression system in which late embryogenesis abundant (LEA) peptides under the control of the lac promoter increase the expression of insecticidal proteins in Bt. The use of lactose to induce the expression of LEA peptides may be a desirable alternative to isopropyl β‐D‐thiogalactopyranoside, the most frequently used inducer for recombinant protein expression. In this study we investigated the use of lactose as an inducer for optimal protein expression. We observed enhanced insecticidal Cry protein expression by applying a simple technique based on intermittent induction, and then optimized concentration and the point of induction time from the 11^th h to the 15^th h. Our data suggest that intermittent induction of lactose might be a new technique for the enhancement of bacterial protein expression.

Differentiation of adipose-derived stem cells into Schwann cell-like cells through intermittent induction: potential advantage of cellular transient memory function

Background

Peripheral nerve injury (PNI) is a worldwide issue associated with severe social and economic burden. Autologous nerve grafting, the gold standard treatment for peripheral nerve defects, still has a number of technical limitations. Tissue engineering technology is a novel therapeutic strategy, and mesenchymal stromal cells (MSCs) are promising seed cells for nerve tissue engineering. However, the efficiency of traditional methods for inducing the differentiation of MSCs to Schwann cell-like cells (SCLCs) remains unsatisfactory.

Methods

Here, we propose an intermittent induction method with alternate use of complete and incomplete induction medium to induce differentiation of adipose-derived stem cells (ASCs) to SCLCs. The time dependence of traditional induction methods and the efficiency of the intermittent induction method and traditional induction methods were evaluated and compared using immunocytochemistry, quantitative reverse transcription polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), and co-culture with the dorsal root ganglion (DRG) in vitro. Cell transplantation was used to compare the effects of the traditional induction method and the intermittent induction method in repairing sciatic nerve defects in vivo.

Results

The results of the present study indicated that the intermittent induction method is more efficient than traditional methods for inducing ASCs to differentiate into SCLCs. In addition, SCLCs induced by this method were closer to mature myelinating Schwann cells and were capable of secreting neurotrophins and promoting DRG axon regeneration in vitro. Furthermore, SCLCs induced by the intermittent induction method could repair sciatic nerve defects in rats by cell transplantation in vivo more effectively than those produced by traditional methods.

Conclusion

Intermittent induction represents a novel strategy for obtaining seed cells for use in nerve tissue engineering.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0884-3) contains supplementary material, which is available to authorized users.