Jianheng Liu

Synthesis and Properties of Hemostatic and Bacteria-Responsive in Situ Hydrogels for Emergency Treatment in Critical Situations

Immediate hemorrhage control and infection prevention are pivotal for saving lives in critical situations such as battlefields, natural disasters, traffic accidents, and so on. In situ hydrogels are promising candidates, but their mechanical strength is often not strong enough for use in critical situations. In this study, we constructed three hydrogels with different amounts of Schiff-base moieties from 4-arm-PEG-NH2, 4-arm-PEG-NHS, and 4-arm-PEG-CHO in which vancomycin was incorporated as an antimicrobial agent. The hydrogels possess porous structures, excellent mechanical strength, and high swelling ratio. The cytotoxicity studies indicated that the composite hydrogel systems possess good biocompatibility. The Schiff bases incorporated improve the adhesiveness and endow the hydrogels with bacteria-sensitivity. The in vivo hemostatic and antimicrobial experiments on rabbits and pigs demonstrated that the hydrogels are able to aid in rapid hemorrhage control and infection prevention. In summary, vancomycin-loaded hydrogels may be excellent candidates as hemostatic and antibacterial materials for first aid treatment of the wounded in critical situations.

A Systematic Review and Meta-Analysis of Ilizarov Methods in the Treatment of Infected Nonunion of Tibia and Femur.

Background Infected nonunion of tibia and femur are common in clinical practice, however, the treatment of these diseases has still been a challenge for orthopaedic surgeons. Ilizarov methods can eradicate infection, compensate bone defects and promote the bone union through progressive bone histogenesis. The objective of this systematic review was to review current available studies reporting on Ilizarov methods in the treatment of infected nonunion of tibia and femur, and to perform meta-analysis of bone and functional results and complications to evaluate the efficacy of Ilizarov methods. Methods A comprehensive literature search was performed from the SCI, PubMed, Cochrane Library; and Embase between January 1995 and August 2015. Some major data were statistically analyzed using weighted means based on the sample size in each study by SPSS 13.0, including number of patients, mean age, mean previous surgical procedures, mean bone defects, mean length of follow-up, bone union, complications per patient, external fixation time, and external fixation index(EFI). Bone results (excellent, good, fair and poor rate), functional results (excellent, good, fair and poor rate) and complications were analyzed by Stata 9.0. Findings A total of 590 patients from 24 studies were included in this systematic review. The average of bone union rate was 97.26% in all included studies. The poor rate in bone results and functional results was 8% (95%CI, 0.04–0.12; I2 = 44.1%, P = 0.065) and 10% (95%CI, 0.05–0.14; I2 = 34.7%, P = 0.121) in patients with infected nonunion of tibia and femur treated by Ilizarov methods. The rate of refracture, malunion, infectious recurrence, knee stiffness, amputation, limb edema and peroneal nerve palsy was respectively 4%, 7%, 5%, 12%, 4%, 13% and 13%. Conclusions Our systematic review showed that the patients with infected nonunion of tibia and femur treated by Ilizarov methods had a low rate of poor bone and functional results. Therefore, Ilizarov methods may be a good choice for the treatment of infected nonunion of tibia and femur.

Injectable Biocomposites for Bone Healing in Rabbit Femoral Condyle Defects

A novel biomimetic bone scaffold was successfully prepared in this study, which was composed of calcium sulfate hemihydrate (CSH), collagen and nano-hydroxyapatite (nHAC). CSH/nHAC was prepared and observed with scanning electron microscope and rhBMP-2 was introduced into CSH/nHAC. The released protein content from the scaffold was detected using high performance liquid chromatography at predetermined time interval. In vivo bone formation capacity was investigated by means of implanting the scaffolds with rhBMP-2 or without rhBMP-2 respectively into a critical size defect model in the femoral condyle of rabbit. The releasing character of rhBMP-2 was that an initial burst release (37.5%) was observed in the first day, followed by a sustained release and reached 100% at the end of day 20. The CSH/nHAC showed a gradual decrease in degradation with the content of nHAC increase. The results of X-rays, Micro CT and histological observation indicated that more new bone was formed in rhBMP-2 group. The results implied that this new injectable bone scaffold should be very promising for bone repair and has a great potential in bone tissue engineering.

Prompt peripheral nerve regeneration induced by a hierarchically aligned fibrin nanofiber hydrogel

Fibrin plays a crucial role in peripheral nerve regeneration, which could occur spontaneously in the format of longitudinally oriented fibrin cables during the initial stage of nerve regeneration. This fibrin cable can direct migration and proliferation of Schwann cells and axonal regrowth, which is very important to nerve regeneration. In the present study, we prepared a three-dimensional hierarchically aligned fibrin nanofiber hydrogel (AFG) through electrospinning and molecular self-assembly to resemble the architecture and biological function of the native fibrin cable. The AFG displayed a hierarchically aligned topography as well as low elasticity (∼1.5kPa) that were similar to nerve extracellular matrix (ECM) and the native fibrin cable. Rapid, directional cell adhesion and migration of Schwann cells (SCs) and dorsal root ganglions were observed in vitro. The AFG was then used as a potential intraluminal substrate in a bioengineered chitosan tube to bridge a 10-mm-long sciatic nerve gap in rats. We found that the AFG served as a beneficial microenvironment to support SCs cable formation and axonal regrowth within 2weeks. Further histological and morphological analyses as well as electrophysiological and functional examinations were performed after AFG implantation for up to 12weeks. The results from morphological analysis and electrophysiological examination indicated that regenerative outcomes achieved by our developed graft were close to those by an autologous nerve graft, but superior to those by hollow chitosan tubes (hCST) and random fibrin nanofiber hydrogel (RFG). Our results demonstrate that the AFG creates an instructive microenvironment by mimicking the native fibrin cable as well as the oriented and soft features of nerve ECM to accelerate axonal regrowth, thus showing great promising potential for applications in neural regeneration. STATEMENT OF SIGNIFICANCE In peripheral nervous system defect repair, a wide variety of strategies have been proposed for preparing functionalized nerve guidance conduits (NGC) with more complex configurations to obtain optimal repair effects. Longitudinally oriented fibrin cables were reported to form spontaneously during the initial stages of peripheral nerve regeneration in an empty NGC, which can direct the migration and proliferation of Schwann cells and promote axonal regrowth. Therefore, based on the biomimetic idea, we prepared a three-dimensional hierarchically aligned fibrin nanofiber hydrogel (AFG) through electrospinning and molecular self-assembly, resembling the architecture and biological function of the native fibrin cable and serving as an intraluminal filling to accelerate axon regeneration. We found that the AFG was a beneficial microenvironment to support SCs cable formation and accelerate axonal regrowth with improved motor functional recovery.

Multilevel 3D Printing Implant for Reconstructing Cervical Spine With Metastatic Papillary Thyroid Carcinoma

Study Design. A unique case report. Objective. A three-dimensional (3D) printing technology is proposed for reconstructing multilevel cervical spine (C2–C4) after resection of metastatic papillary thyroid carcinoma in a middle-age female patient. Summary of Background Data. Papillary thyroid carcinoma is a malignant neoplasm with a relatively favorable prognosis. A metastatic lesion in multilevel cervical spine (C2–C4) destroys neurological functions and causes local instability. Radical excision of the metastasis and reconstruction of the cervical vertebrae sequence conforms with therapeutic principles, whereas the special-shaped multilevel upper-cervical spine requires personalized implants. 3D printing is an additive manufacturing technology that produces personalized products by accurately layering material under digital model control via a computer. Reporting of this recent technology for reconstructing multilevel cervical spine (C2–C4) is rare in the literature. Methods. Anterior-posterior surgery was performed in one stage. Radical resection of the metastatic lesion (C2–C4) and thyroid gland, along with insertion of a personalized implant manufactured by 3D printing technology, were performed to rebuild the cervical spine sequences. The porous implant was printed in Ti6AL4V with perfect physicochemical properties and biological performance, such as biocompatibility and osteogenic activity. Finally, lateral mass screw fixation was performed via a posterior approach. Results. Patient neurological function gradually improved after the surgery. The patient received 11/17 on the Japanese Orthopedic Association scale and ambulated with a personalized skull-neck-thorax orthosis on postoperative day 11. She received radioiodine I131 therapy. The plane x-rays and computed tomography revealed no implant displacement or subsidence at the 12-month follow-up mark. Conclusion. The presented case substantiates the use of 3D printing technology, which enables the personalization of products to solve unconventional problems in spinal surgery. Level of Evidence: 5

Localized and sustained delivery of erythropoietin from PLGA microspheres promotes functional recovery and nerve regeneration in peripheral nerve injury.

Erythropoietin (EPO) has been demonstrated to exert neuroprotective effects on peripheral nerve injury recovery. Though daily intraperitoneal injection of EPO during a long period of time was effective, it was a tedious procedure. In addition, only limited amount of EPO could reach the injury sites by general administration, and free EPO is easily degraded in vivo. In this study, we encapsulated EPO in poly(lactide-co-glycolide) (PLGA) microspheres. Both in vitro and in vivo release assays showed that the EPO-PLGA microspheres allowed sustained release of EPO within a period of two weeks. After administration of such EPO-PLGA microspheres, the peripheral nerve injured rats had significantly better recovery compared with those which received daily intraperitoneal injection of EPO, empty PLGA microspheres, or saline treatments. This was supported by the functional, electrophysiological, and histological evaluations of the recovery done at week 8 postoperatively. We conclude that sustained delivery of EPO could be achieved by using EPO-PLGA microspheres, and such delivery method could further enhance the recovery function of EPO in nerve injury recovery.

POSS-modified PEG Adhesives for Wound Closure

PEG-related adhesives are limited in clinical use because they are easy to swell and cannot support the cell growth. In this study, we produced a series of POSS-modified PEG adhesives with high adhesive strength. Introduction of inorganic hydrophobic POSS units decreased the swelling of the adhesives and enhanced cell adhesion and growth. The in vitro cytotoxicity and in vivo inflammatory response experiments clearly demonstrated that the adhesives were nontoxic and possessed excellent biocompatibility. Compared with the sutured wounds, the adhesive-treated wounds showed an accelerated healing process in wounded skin model of the Bama miniature pig, demonstrating that the POSS-modified PEG adhesive is a promising candidate for wound closure.

Synergistic Effects of BMP9 and miR-548d-5p on Promoting Osteogenic Differentiation of Mesenchymal Stem Cells.

Various stimulators have been reported to promote MSC osteogenic differentiation via different pathways such as bone morphogenetic protein 9 (BMP9) through influencing COX-2 and miR-548d-5p through targeting peroxisome proliferator-activated receptor-γ (PPARγ). Whether synergistic effects between BMP9 and miR-548d-5p existed in promoting osteogenesis from MSCs was unclear. In the study, the potential synergistic effects of BMP9 and miR-548d-5p on human MSC differentiation were investigated. Osteogenic differentiation of MSCs treated with BMP9 or miR-548d-5p was detected with multimodality of methods. The results demonstrated that BMP9 and miR-548d-5p significantly influenced COX-2 and PPARγ, respectively. BMP9 also influenced the expression of PPARγ, but no significant effect of miR-548d-5p on COX-2 was observed. When BMP9 and miR-548d-5p were combined, more potent effects on both COX-2 and PPARγ were observed than BMP9 or miR-548d-5p alone. Consistently, osteogenic analysis at different timepoints demonstrated that osteogenic genes, ALP activity, calcium deposition, OPN protein, and matrix mineralization were remarkably upregulated by BMP9/miR-548d-5p compared with BMP9 or miR-548d-5p alone, indicating the synergetic effects of BMP9 and miR-548d-5p on osteogenic differentiation of MSCs. Our study demonstrated that regulating different osteogenic regulators may be an effective strategy to promote bone tissue regeneration for bone defects.

Establishment of a rat model of chronic thoracolumbar cord compression with a flat plastic screw

Previous studies of animal models of chronic mechanical compression of the spinal cord have mainly focused on cervical and thoracic lesions, but few studies have investigated thoracolumbar injury. The specific pathophysiological mechanism of chronic thoracolumbar cord injury has not yet been elucidated. The purpose of this study was to improve animal models of chronic thoracolumbar cord compression using the progressive screw. A custom-designed flat plastic screw was implanted in the spinal cord between thoracic vertebrae 12 and lumbar 1 of rats. The screw was tightened one complete turn (0.5 mm) every 7 days for 4 weeks to create different levels of chronic spinal cord compression. Following insertion of the screw, there was a significant decline in motor function of the hind limbs, and severe stenosis of micro-computed tomography parameters in the spinal cord. Cortical somatosensory evoked potential amplitudes were reduced remarkably, and latencies were prolonged at 30 minutes after surgery. The loss of motor neurons in the gray matter was marked. Demyelination and cavitation were observed in the white matter. An appropriate rat model of chronic thoracolumbar cord compression was successfully created using the progressive screw compression method, which simulated spinal cord compression injury.

Ipsilateral fibula transport for the treatment of massive tibial bone defects

OBJECTIVE The objective of the study was to evaluate the effectiveness of the treatment of massive tibial bone defects by ipsilateral fibula transport. MATERIALS AND METHODS Nine patients with massive tibial bone defects were retrospectively reviewed. There were 7 males and 2 females with an average age of 32.22 years. The mean length of bone defect was 15.67cm (range 13-25cm). RESULTS All patients were followed up and the mean time of follow up was 40.11 months (range 26-60 months). All the patients achieved bone union and the average external fixation time was 11.67 months (range 9-14 months). The mean degrees of knee extension were 2.2°(range 0-5°) and the mean degrees of knee flexion were 131.7° (range 120-140°). The mean degrees of ankle dorsiflexion were 8.9° (range 0-15°) and the mean degrees of ankle plantar flexion were 30° (range 20-40°). CONCLUSION Our study suggested that ipsilateral fibula transport in the treatment of massive tibial bone defects acquired satisfying functional results. It may be a better choice for the patients without suitable proximal or distal tibia remnant to transport.