Junchao Xing

A composite demineralized bone matrix--self assembling peptide scaffold for enhancing cell and growth factor activity in bone marrow.

The need for suitable bone grafts is high; however, there are limitations to all current graft sources, such as limited availability, the invasive harvest procedure, insufficient osteoinductive properties, poor biocompatibility, ethical problems, and degradation properties. The lack of osteoinductive properties is a common problem. As an allogenic bone graft, demineralized bone matrix (DBM) can overcome issues such as limited sources and comorbidities caused by invasive harvest; however, DBM is not sufficiently osteoinductive. Bone marrow has been known to magnify osteoinductive components for bone reconstruction because it contains osteogenic cells and factors. Mesenchymal stem cells (MSCs) derived from bone marrow are the gold standard for cell seeding in tissue-engineered biomaterials for bone repair, and these cells have demonstrated beneficial effects. However, the associated high cost and the complicated procedures limit the use of tissue-engineered bone constructs. To easily enrich more osteogenic cells and factors to DBM by selective cell retention technology, DBM is modified by a nanoscale self-assembling peptide (SAP) to form a composite DBM/SAP scaffold. By decreasing the pore size and increasing the charge interaction, DBM/SAP scaffolds possess a much higher enriching yield for osteogenic cells and factors compared with DBM alone scaffolds. At the same time, SAP can build a cellular microenvironment for cell adhesion, proliferation, and differentiation that promotes bone reconstruction. As a result, a suitable bone graft fabricated by DBM/SAP scaffolds and bone marrow represents a new strategy and product for bone transplantation in the clinic.

Establishment of a bilateral femoral large segmental bone defect mouse model potentially applicable to basic research in bone tissue engineering

BACKGROUND To understand the cellular mechanism underlying bone defect healing in the context of tissue engineering, a reliable, reproducible, and standardized load-bearing large segmental bone defect model in small animals is indispensable. The aim of this study was to establish and evaluate a bilateral femoral defect model in mice. MATERIALS AND METHODS Donor mouse bone marrow mesenchymal stem cells (mBMSCs) were obtained from six mice (FVB/N) and incorporated into partially demineralized bone matrix scaffolds to construct tissue-engineered bones. In total, 36 GFP(+) mice were used for modeling. Titanium fixation plates with locking steel wires were attached to the femurs for stabilization, and 2-mm-long segmental bone defects were created in the bilateral femoral midshafts. The defects in the left and right femurs were transplanted with tissue-engineered bones and control scaffolds, respectively. The healing process was monitored by x-ray radiography, microcomputed tomography, and histology. The capacity of the transplanted mBMSCs to recruit host CD31(+) cells was investigated by immunofluorescence and real-time polymerase chain reaction. RESULTS Postoperatively, no complication was observed, except that two mice died of unknown causes. Stable fixation of femurs and implants with full load bearing was achieved in all animals. The process of bone defect repair was significantly accelerated due to the introduction of mBMSCs. Moreover, the transplanted mBMSCs attracted more host CD31(+) endothelial progenitors into the grafts. CONCLUSIONS The present study established a feasible, reproducible, and clinically relevant bilateral femoral large segmental bone defect mouse model. This model is potentially suitable for basic research in the field of bone tissue engineering.

Inflammatory Microenvironment Changes the Secretory Profile of Mesenchymal Stem Cells to Recruit Mesenchymal Stem Cells

Background/Aims: Human bone-marrow mesenchymal stem cells (hBMSCs) are widely transplanted into inflammatory microenvironment to accelerate tissue regeneration. Transplanted hBMSCs recruit host hBMSCs through a poorly understood mechanism. This study was aimed to determine whether and how inflammatory microenvironment influenced the host-hBMSCs-recruiting capability of transplanted hBMSCs. Methods: Pro-inflammatory factors, including IL-1β, IL-6 and TNF-α, were utilized to mimic inflammatory microenvironment. hBMSCs were cultured and conditioned media (CM) were collected. The effects of inflammatory microenvironment on the host-hBMSCs-recruiting capability of cultured hBMSCs were revealed by transwell migration assays. Employing semi-quantitative and quantitative cytokine antibody assays, we examined the secretory profile of cultured hBMSCs. Results: CM from cultured hBMSCs exerted excellent host-hBMSCs-recruiting capability, which was significantly promoted by exposure to inflammatory microenvironment. Within inflammatory microenvironment, hBMSCs secreted more chemokines related to cell migration. Finally, 21 cytokines were verified as potential factors accounting for the enhanced host-hBMSCs-recruiting capability of cultured hBMSCs exposed to inflammatory microenvironment. Conclusion: These results strongly suggested that in clinic, inflammatory microenvironment might promote the host-hBMSCs-recruiting capacity of transplanted hBMSCs by increasing chemokines secretion. Modulation of such characteristics of hBMSCs might provide novel therapeutic ideas in the context of hBMSCs.

A nano-scaled and multi-layered recombinant fibronectin/cadherin chimera composite selectively concentrates osteogenesis-related cells and factors to aid bone repair

Easily accessible and effective bone grafts are in urgent need in clinic. The selective cell retention (SCR) strategy, by which osteogenesis-related cells and factors are enriched from bone marrow into bio-scaffolds, holds great promise. However, the retention efficacy is limited by the relatively low densities of osteogenesis-related cells and factors in marrow; in addition, a lack of satisfactory surface modifiers for scaffolds further exacerbates the dilemma. To address this issue, a multi-layered construct consisting of a recombinant fibronectin/cadherin chimera was established via a layer-by-layer self-assembly technique (LBL-rFN/CDH) and used to modify demineralised bone matrix (DBM) scaffolds. The modification was proven stable and effective. By the mechanisms of physical interception and more importantly, chemical recognition (fibronectin/integrins), the LBL-rFN/CDH modification significantly improved the retention efficacy and selectivity for osteogenesis-related cells, e.g., monocytes, mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs), and bioactive factors, e.g., bFGF, BMP-2 and SDF-1α. Moreover, the resulting composite (designated as DBM-LBL-rFN/CDH) not only exhibited a strong MSC-recruiting capacity after SCR, but also provided favourable microenvironments for the proliferation and osteogenic differentiation of MSCs. Eventually, bone repair was evidently improved. Collectively, DBM-LBL-rFN/CDH presented a suitable biomaterial for SCR and a promising solution for tremendous need for bone grafts. STATEMENT OF SIGNIFICANCE There is an urgent need for effective bone grafts. With the potential of integrating osteogenicity, osteoinductivity and osteoconductivity, selective cell retention (SCR) technology brings hope for developing ideal grafts. However, it is constrained by low efficacy and selectivity. Thus, we modified demineralized bone matrix with nano-scaled and multi-layered recombinant fibronectin/cadherin chimera (DBM-rFN/CDH-LBL), and evaluate its effects on SCR and bone repair. DBM-rFN/CDH-LBL significantly improved the efficacy and selectivity of SCR via physical interception and chemical recognition. The post-enriched DBM-rFN/CDH-LBL provided favourable microenvironments to facilitate the migration, proliferation and osteogenic differentiation of MSCs, thus accelerating bone repair. Conclusively, DBM-rFN/CDH-LBL presents a novel biomaterial with advantages including high cost-effectiveness, more convenience for storage and transport and can be rapidly constructed intraoperatively.

Tissue-engineered bone treating simple bone cyst-a new strategy.

BACKGROUND The pathological fracture is a most important complication during bone cyst and can be prevented by early focus clearance and bone grafting. Tissue-engineered bone (TEB) with outstanding osteogenesis is a better choice for bone repair. Here, we firstly reported that TEB was used to heal bone cyst. MATERIALS AND METHODS The clinical data were collected from 23 patients who received bone defect repair separately with TEB or allogeneic bone (Allo-B) after erasion during 2004-2008. Allo-B had been as a control. The healing time and healing quality, the incidence of complications, the safety, and the bone grafting failure rate were compared. RESULTS In TEB group, the follow-up time was 28 ± 15.48 months; nine cases were confirmed healed (3.45 ± 2.01 months), one case was cyst healing with defect, and one case had relapse. In Allo-B, 12 patients were followed up for 28.58 ± 20.44 months; seven cases were confirmed healed (6.75 ± 3.31 mo), four cases were cyst healing with defect, and one case had relapse. After operation, no statistically significant differences in bone healing and incidence of complications were observed between two groups, but the difference in bone healing time was statistically significant (P < 0.05). There was no else tumorigenesis in both groups. CONCLUSIONS In treating simple bone cyst, Allo-B and TEB have considerable efficacy and safety; TEB is superior to Allo-B in respect of healing time; there is no rejection after TEB grafting but certain rejection after Allo-B grafting.

Sustained release of bioactive protein from a lyophilized tissue-engineered construct promotes the osteogenic potential of mesenchymal stem cells.

Tissue‐engineered constructs (TECs) seeded with mesenchymal stem cells (MSCs) represent a therapy for large bone defects. However, massive cell death in TECs in the early postimplantation period prompted us to investigate the osteoinductive mechanism of TECs. Previous studies demonstrated that stem cell extracts retained equivalent levels of bioactive proteins and exhibited an osteoinductive nature similar to that of intact cells. These data led us to hypothesize that despite the massive cell death in TECs, devitalized MSC‐derived proteins remain on the scaffolds and are released to improve cell function. Here, TECs were prepared using demineralized bone matrix seeded with human umbilical cord Whartons jelly‐derived MSCs (hWJMSCs), and the cells seeded in TECs were devitalized by lyophilizing the TECs. Scanning electron microscopy, BCA protein assays, quantitative cytokine array analysis and immunofluorescent staining indicated that approximately 3 mg/cm3 of total protein and 49 types of cytokines derived from hWJMSCs were preserved in the lyophilized TECs (LTECs). The sustainable release of total protein and cytokines from LTECs lasted for more than 2 weeks. The released protein improved the osteogenic behavior of and gene expression in MSCs. Furthermore, the lyophilized hWJMSC‐derived proteins had immunoregulatory properties similar to those of live MSCs in mixed lymphocyte reactions. Collectively, we present a novel perspective on the osteoinductive mechanism of TECs and introduce LTECs as new systems for delivering multiple cytokines to enhance MSC behavior.

Umbilical cord Wharton's jelly repeated culture system: a new device and method for obtaining abundant mesenchymal stem cells for bone tissue engineering.

To date, various types of cells for seeding regenerative scaffolds have been used for bone tissue engineering. Among seed cells, the mesenchymal stem cells derived from human umbilical cord Wharton’s jelly (hUCMSCs) represent a promising candidate and hold potential for bone tissue engineering due to the the lack of ethical controversies, accessibility, sourced by non-invasive procedures for donors, a reduced risk of contamination, osteogenic differentiation capacities, and higher immunomodulatory capacity. However, the current culture methods are somewhat complicated and inefficient and often fail to make the best use of the umbilical cord (UC) tissues. Moreover, these culture processes cannot be performed on a large scale and under strict quality control. As a result, only a small quantity of cells can be harvested using the current culture methods. To solve these problems, we designed and evaluated an UC Wharton’s jelly repeated culture device. Using this device, hUCMSCs were obtained from the repeated cultures and their quantities and biological characteristics were compared. We found that using our culture device, which retained all tissue blocks on the bottom of the dish, the total number of obtained cells increased 15–20 times, and the time required for the primary passage was reduced. Moreover, cells harvested from the repeated cultures exhibited no significant difference in their immunophenotype, potential for multilineage differentiation, or proliferative, osteoinductive capacities, and final osteogenesis. The application of the repeated culture frame (RCF) not only made full use of the Wharton’s jelly but also simplified and specified the culture process, and thus, the culture efficiency was significantly improved. In summary, abundant hUCMSCs of dependable quality can be acquired using the RCF.

1,25(OH)2D3 inhibited Th17 cells differentiation via regulating the NF-κB activity and expression of IL-17

The role of vitamin D (VD) in innate and adaptive immune responses to tuberculosis is still unclear. Our research was aimed to uncover the effect of VD on Th17 cells and elucidate potential molecular mechanism.

The osteogenetic efficacy of goat bone marrow-enriched self-assembly peptide/demineralized bone matrix in vitro and in vivo.

In clinical practice, the prolonged duration, high cost, critical technique requirements, and ethical issues make the classical construction method of tissue-engineered bones difficult to apply widely. The major essentials in tissue engineering strategies include seed cells, growth factors, and scaffolds. This study aimed to incorporate these factors in a rapid and cost-effective manner. A self-assembly peptide/demineralized bone matrix (SAP/DBM) composite was artificially established and used for bone marrow enrichment via a selective cell retention approach. Then, goat mesenchymal stem cells (gMSCs) were seeded onto the SAP/DBM or DBM. The proliferation status of gMSCs in different scaffolds was analyzed, and the osteogenetic efficacy was evaluated after osteogenic induction. Bilateral critical-sized femoral defects (20-mm in length) were created in goats, and then the defects were implanted with the postenriched composite or DBM. Then, bone scan imaging, micro-computed tomography (CT) analysis and histological examination were performed to assess the reparative effects of the different implants. Compared with the DBM scaffolds, the growth of gMSCs in the postenriched SAP/DBM composite was faster and the expression levels of the osteo-specific genes (i.e., alkaline phosphatase, osteocalcin, osteopontin, and runt-related transcription factor 2) were significantly higher after 14 days of osteogenic induction. More importantly, the postenriched SAP/DBM composite significantly enhanced bone metabolic activity in the defect area compared with DBM at 2 and 4 weeks postoperation. Moreover, bone reconstruction was complete in marrow-enriched SAP/DBM composite, but not in the DBM. In addition, all of the osteo-related parameters, including the ratio of bone volume to total bone volume, bone mineral density, new trabecular number, and new trabecular thickness, were significantly higher in the marrow-enriched SAP/DBM than those in the DBM. These results indicated that the SAP/DBM composite held great potential for clinical applications; immediate implantation after marrow enrichment could be a new and effective strategy for treating bone defect.

Alendronate induces osteoclast precursor apoptosis via peroxisomal dysfunction mediated ER stress

Nitrogen‐containing bisphosphonates including alendronate (ALN) are the current first line antiresorptive drug in treating osteoporosis. In our study, we found that ALN administration impaired the secretion of platelet derived growth factor‐BB (PDGF‐BB), the most important angiogenic cytokines produced by preosteoclast (POC), in both sham and ovariectomized (OVX) mice. To further understand this phenomenon, we induced bone marrow macrophages (BMMs) to POCs in vitro and detected the effects of ALN particularly in POCs. The proapoptotic effect of ALN in POCs was confirmed by flow cytometry. On the molecular level, we found that farnesyl diphosphate synthase (FDPS) inhibition of ALN led to peroxisomal dysfunction and up regulation of cytoprotective protein glucose‐regulated protein (GRP) 78. Peroxisomal dysfunction further induced endoplasmic reticulum (ER) stress in POCs and finally resulted in cell apoptosis marked by reduced expression of B‐cell lymphoma 2 (Bcl‐2) and increased expressions of CCAAT/enhancer binding protein homologous protein (CHOP), Bcl2 associated X (Bax), and cleaved caspase‐3. We concluded that ALN has no selectivity in inhibiting POC and mature osteoclast. For POCs, ALN inhibition of FDPS leads to peroxisomal dysfunction, which further mediates ER stress and finally causes cell apoptosis. Considering that decreased angiogenesis is also an important issue in treating osteoporosis, how to preserve pro‐angiogenic POCs while depleting mature osteoclasts is a problem worthy to be solved.