Application of bioactive hydrogels combined with dental pulp stem cells for the repair of large gap peripheral nerve injuries

Due to the limitations in autogenous nerve grafting or Schwann cell transplantation, large gap peripheral nerve injuries require a bridging strategy supported by nerve conduit. Cell based therapies provide a novel treatment for peripheral nerve injuries. In this study, we first experimented an optimal scaffold material synthesis protocol, from where we selected the 10% GFD formula (10% GelMA hydrogel, recombinant human basic fibroblast growth factor and dental pulp stem cells (DPSCs)) to fill a cellulose/soy protein isolate composite membrane (CSM) tube to construct a third generation of nerve regeneration conduit, CSM-GFD. Then this CSM-GFD conduit was applied to repair a 15-mm long defect of sciatic nerve in a rat model. After 12 week post implant surgery, at histologic level, we found CSM-GFD conduit could regenerate nerve tissue like neuron and Schwann like nerve cells and myelinated nerve fibers. At physical level, CSM-GFD achieved functional recovery assessed by a sciatic functional index study. In both levels, CSM-GFD performed like what gold standard, the nerve autograft, could do. Further, we unveiled that almost all newly formed nerve tissue at defect site was originated from the direct differentiation of exogeneous DPSCs in CSM-GFD. In conclusion, we claimed that this third-generation nerve regeneration conduit, CSM-GFD, could be a promising tissue engineering approach to replace the conventional nerve autograft to treat the large gap defect in peripheral nerve injuries.

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A novel 3^rd generation nerve conduit was successfully constructed and applied for repairing peripheral nerve injuries (PNI).

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Dental pulp stem cells (DPSCs) was optimized as an ideal seeding cells for nerve regeneration.

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A bioactive system combining GelMA with human bFGF and DPSCs could reconstruct the long gap PNI within 12 weeks in vivo.

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Our system could achieve the same outcome in nerve repair as that of autografting, a routine treatment for PNI.

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The proposed bioactive system may trigger an evolutional change into the current clinical practice in managing PNI.

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The majority of the regenerated nerve tissue was originated from the donor’s dental pulp stem cells.

Genetically engineered bi-functional silk material with improved cell proliferation and anti-inflammatory activity for medical application

Functional silk is a promising material for future medical applications. These include fabrication of diverse silk fiber and silk protein-regenerated biomaterials such as silk sutures, hydrogel, films, and 3D scaffolds for wound healing and tissue regeneration and reconstruction. Here, a novel bi-functional silk with improved cell proliferation and anti-inflammatory activities was created by co-expressing the human basic fibroblast growth factor (FGF2) and transforming growth factor-β1 (TGF_β1) genes in silkworm. First, both FGF2 and TGF_β1 genes were confirmed to be successfully expressed in silk thread. The characterization of silk properties by SEM, FTIR, and mechanical tests showed that this new silk (FT silk) had a similar diameter, inner molecular composition, and mechanical properties as those of normal silk. Additionally, expressed FGF2 and TGF_β1 proteins were continuously and slowly released from FT silk for one week. Most importantly, the FGF2 and TGF_β1 contained in FT silk not only promoted cell proliferation by activating the ERK pathway but also significantly reduced LPS-induced inflammation responses in macrophages by mediating the Smad pathway. Moreover, this FT silk had no apparent toxicity for cell growth and caused no cell inflammation. These properties suggest that it has a potential for medical applications. STATEMENT OF SIGNIFICANCE: Silk spun by domestic silkworm is a promising material for fabricating various silk protein regenerated biomaterials in medical area, since it owes good biocompatibility, biodegradability and low immunogenicity. Recently, fabricating various functional silk fibers and regenerated silk protein biomaterials which has ability of releasing functional protein factor is the hot point field. This study is a first time to create a novel bi-functional silk material with the improved cell proliferation and anti-inflammatory activity by genetic engineered technology. This novel silk has a great application potential as new and novel medical material, and this study also provides a new strategy to create various functional or multifunctional silk fiber materials in future.

Novel strategy for expression of authentic and bioactive human basic fibroblast growth factor in Bacillus subtilis

Inteins, also known as "protein introns," have been found to be present in many microbial species and widely employed for the expression and purification of recombinant proteins in Escherichia coli. However, interestingly, until now there has not been much information on the identification and application of inteins to protein expression in Bacillus subtilis. In this article, for the first time, despite the likelihood of absence of inteins in B. subtilis, this bacterium was shown to be able to facilitate auto-catalytic cleavages of fusions formed between inteins and recombinant proteins. Employing a construct expressing the intein, Ssp DnaB, (DnaB), which was fused at its N-terminus with the cellulose-binding domain (CellBD) of an endoglucanase encoded by the cenA gene of Cellulomonas fimi, the construct was demonstrated to be capable of mediating intracellular expression of basic fibroblast growth factor (bFGF), followed by auto-processing of the CellBD-DnaB-bFGF fusion to result in bFGF possessing the 146-residue authentic structure. The mentioned fusion was shown to result in a high yield of 84 mg l^-1 of biologically active bFGF. Future work in improving the growth of B. subtilis may enable the use of this bacterium, working in cooperation with inteins, to result in a new platform for efficient expression of valuable proteins.