Multi-functional osteoclasts in matrix-based tissue engineering bone.

The repair of bone defects, especially for the large segment of bone defects, has always been an urgent problem in orthopedic clinic and attracted researchers' attention. Nowadays, the application of tissue engineering bone in the repair of bone defects has become the research hotspot. With the rapid development of tissue engineering, the novel and functional scaffold materials for bone repair have emerged. In this review, we have summarized the multi-functional roles of osteoclasts in bone remodeling. The development of matrix-based tissue engineering bone has laid a theoretical foundation for further investigation about the novel bone regeneration materials which could perform high bioactivity. From the point of view on preserving pre-osteoclasts and targeting mature osteoclasts, this review introduced the novel matrix-based tissue engineering bone based on osteoclasts in the field of bone tissue engineering, which provides a potential direction for the development of novel scaffold materials for the treatment of bone defects.

Inhibitory effect of dihydroartemisinin on chondrogenic and hypertrophic differentiation of mesenchymal stem cells.

Chondrocytes located in hyaline cartilage may maintain phenotype while the chondrocytes situated in calcified cartilage differentiate into hypertrophy. Chondrogenic and hypertrophic differentiation of mesenchymal stem cells (MSCs) are two subsequent processes during endochondral ossification. However, it is necessary for chondrocytes to hold homeostasis and to inhibit hypertrophic differentiation in stem cell-based regenerated cartilage. Dihydroartemisinin (DHA) is derived from artemisia apiacea which has many biological functions such as anti-malarial and anti-tumor. Whereas the effects of DHA on chondrogenic and hypertrophic differentiation are poorly understand. In this study, the cytotoxicity of DHA was determined by CCK8 assay and the cell apoptosis was analyzed by flow cytometry. Additionally, the effects of DHA on chondrogenic and hypertrophic differentiation of MSCs are explored by RT-PCR, western blotting and immunohistochemistry. The results showed that DHA inhibited expression of chondrogenic markers including Sox9 and Col2a1 by activating Nrf2 and Notch signaling. After induced to chondrogenesis, cells were treated with hypertrophic induced medium with DHA. The results revealed that hypertrophic markers including Runx2 and Col10a1 were down-regulated following DHA treatment through Pax6/HOXA2 and Gli transcription factors. These findings indicate that DHA is negative to chondrogenesis and is protective against chondrocyte hypertrophy to improve chondrocytes stability. Therefore, DHA might be not suited for chondogenesis but be potential as a new therapeutic candidate to maintain the biological function of regenerated cartilage.

A novel axial-stress bioreactor system combined with a substance exchanger for tissue engineering of 3D constructs.

This study introduced a prototype of an axial-stress bioreactor system that supports long-term growth and development of engineered tissues. The main features of this bioreactor are an integrated substance exchanger and feedback control of pH and PO2. A 21-day study was conducted to validate the system's ability to maintain a stable environment, while remaining sterile. Our results showed that the pH, PO2, and nutrient (glucose) remained balanced at appropriate levels, while metabolic waste (lactic acid) was removed. No bacteria or fungi were detected in the system or tissue; thus, demonstrating that it was sterile. These data indicate the bioreactor's strong potential for long-term tissue culture. To explore this idea, the effect of dynamic culture, including cyclic compression and automatic substance exchange, on mouse bone-marrow mesenchymal stem cells (BMSCs) seeded in decalcified bone matrix was studied using the bioreactor prototype. Histological sections of the engineered tissues showed higher cell densities in scaffolds in dynamic culture compared to those in static culture, while cell cycle analysis showed that dynamic culture promoted BMSC proliferation (proliferation index, PI=34.02±1.77) more effectively than static culture (PI=26.66±1.81). The results from a methyl thiazolyl tetrazolium assay were consistent with the loading experimental data. Furthermore, elevated alkaline phosphatase activity and calcium content were observed in dynamic condition compared to static culture. In conclusion, this bioreactor system supplies a method of modulating the pH and PO2 in defined ranges with only small fluctuations; it can be used as a physiological or pathological analog. Automatic control of the environment is a practical solution for long-term, steady-state culture for future commercialization.

Piezoelectric PU/PVDF electrospun scaffolds for wound healing applications.

Previous studies have shown that piezoelectric materials may be used to prepare bioactive electrically charged surfaces. In the current study, polyurethane/polyvinylidene fluoride (PU/PVDF) scaffolds were prepared by electrospinning. The mechanical property and piezoelectric property of the scaffolds were evaluated. The crystalline phase of PVDF in the scaffolds was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). In vitro cell culture was performed to investigate cytocompatibility of the scaffolds. Wound-healing assay, cell-adhesion assay, quantitative RT-PCR and Western blot analyses were performed to investigate piezoelectric effect of the scaffolds on fibroblast activities. Further, the scaffolds were subcutaneously implanted in Sprague-Dawley (SD) rats to investigate their biocompatibility and the piezoelectric effect on fibrosis in vivo. The results indicated that the electrospinning process had changed PVDF crystalline phase from the nonpiezoelectric α phase to the piezoelectric ß phase. The fibroblasts cultured on the scaffolds showed normal morphology and proliferation. The fibroblasts cultured on the piezoelectric-excited scaffolds showed enhanced migration, adhesion and secretion. The scaffolds that were subcutaneously implanted in SD rats showed higher fibrosis level due to the piezoelectrical stimulation, which was caused by random animal movements followed by mechanical deformation of the scaffolds. The scaffolds are potential candidates for wound healing applications.

Synergy of tendon stem cells and platelet-rich plasma in tendon healing.

Injured rat Achilles tendons were treated with botulism toxin to create a mechanically unloaded condition (unloaded) or left untreated (loaded), and then treated with phosphate-buffered saline (PBS), platelet-rich plasma (PRP), tendon stem cells (TSCs), or a combination (TSCs + PRP). mRNA and protein expression of collagen I, collagen III, tenascin C, and Smad 8 were determined by real time PCR and immunostaining, respectively. Loaded tendons treated with PBS, PRP, or TSCs for 3 or 14 days had higher collagen I mRNA expression than unloaded tendons. Loaded tendons treated with PBS for 3 or 14 days or with PRP for 3 days had higher collagen I protein levels than unloaded tendons. Loaded tendons treated for 3 days with PBS, for 14 days with PRP or TSCs or TSCs + PRP for 3 or 14 days had higher collagen III protein levels than unloaded tendons. Collagen I mRNA levels were higher in TSCs + PRP-treated loaded tendons compared to PBS-treated loaded tendons on day 3 of treatment. Based on changes in the expression of tendon-healing genes, our data suggest that the combination of TSCs and PRP has synergistic effects on tendon healing under both loaded and unloaded conditions, and loaded conditions improve tendon healing.

[Effects of different cyclic mechanical stretching loads on human tenocytic cytoskeleton in vitro].

OBJECTIVE: To investigate the human tenocyte cytoskeleton under different in vitro stretching conditions and analyze the relations between the changes of tenocytic cytoskeleton and different stretching loads. METHODS: Human tenocytes, cultivated for 5 -7 passages, were stretched under 4%, 8% and 12% cyclic mechanical stretching with a duration of 2, 4, 8, 12, 24 hours and a frequency of 0.5 and 1.0 Hz. Laser scanning confocal microscope was used to examine the changes of F-actin and nucleus after immunofluorescent staining at different cyclic mechanical stretching loads on human tenocyte. The uni-cell average fluorescence intensity was measured with an image analysis system by the photos of human tenocyte cytoskeleton and analyzed by the single factor analysis of variance. RESULTS: After cyclic stretching under 4% stretching with a duration of 2 hours at 0.5 Hz, the microfilament of human tenocyte had an irregular and dim alignment. F-actin was thicker and ruptured under 4% stretching with a duration of 4 hours. Under 8% stretching with a duration of 4 hours at 0.5 Hz, all actin microfilaments ruptured, but part of membrane microfilament remained intact. There was a rising trend of actin filament fracturing under 12% stretching with a duration of 2, 4, 8, 12, 24 hours at 1.0 Hz. And all actin filaments fractured at 24 hours. In the control group, the fluorescent intensity of F-actin was at the highest and the filament remained intact. Under the same stretching frequency, the fluorescent intensity of F-actin had a declining trend and significant differences existed under different stretching loads with different durations (P < 0.05). The fluorescent intensity of F-actin increased in all experimental groups, but it was lower than that of the control group with a duration of 8 hours. The expression of F-actin decreased with a longer duration and reached its lowest at 24 hours. The most obvious phenomenon of nuclear condensation and apoptotic body formation was observed under 4% stretching with a duration of 4 hours at 0.5 Hz. CONCLUSION: Different cyclic mechanical stretching may cause the in vitro breakage and depolymerization of human tenocytic F-actin. Such an effect correlates with stretching force and its duration.

Bone marrow mesenchymal stem cells can be mobilized into peripheral blood by G-CSF in vivo and integrate into traumatically injured cerebral tissue.

The efficacy of granulocyte colony-stimulating factor (G-CSF) in mobilizing mesenchymal stem cells (MSCs) into peripheral blood (PB) and the ability of PB-MSCs incorporated into injured brain were tested. Colony forming, cell phenotype and differentiation potential of mouse MSCs mobilized by G-CSF (40 µg/kg) were evaluated. Mortality and pathological changes in mice with serious craniocerebral trauma plus G-CSF treatment (40 µg/kg) were investigated. Bone marrow (BM) cells derived from GFP mice were fractionated into MSCs, hematopoietic stem cells (HSCs), and non-MSC/HSCs using magnetic beads and adherent culture. The resultant cell populations were transplanted into injured mice. The in vivo integration and differentiation of the transplanted cells were detected immunocytochemically. The expression of SDF-1 in injured area of brain was tested by Western blot. G-CSF was able to mobilize MSCs into PB (fourfold increase). PB-MSCs possessed similar characteristics as BM-MSCs in terms of colony formation, the expression pattern of CD73, 44, 90, 106, 31 and 45, and multipotential of differentiation. Accumulative total mice mortality was lower in TG group (5/14) than that in T group (7/14). It was MSCs, not HSCs or non-MSC/HSC cells integrated into the damaged cerebral tissue and differentiated into cells expressing neural markers. Increased SDF-1 expression in injured area of brain was confirmed, which could facilitate the homing of MSCs to brain. G-CSF can mobilize MSCs into PB and MSCs in PB can integrate into injured cerebral tissue and transdifferentiated into neural cells and may benefit the repair of trauma.

Effect of hBD2 genetically modified dermal multipotent stem cells on repair of infected irradiated wounds.

Deficiencies in repair cells and infection are two of the main factors that can hinder the process of wound healing. In the present study, we investigated the ability of human beta-defensin-2 (hBD2) genetically modified dermal multipotent stem cells (dMSCs) to accelerate the healing irradiated wounds complicated by infections. An hBD2 adenovirus expression vector (Adv-hBD2) was firstly constructed and used to infect dMSCs. The antibacterial activity of the supernatant was determined by Kirby-Bauer method and macrodilution broth assay. Time to complete wound healing, residual percentage of wound area, and the number of bacteria under the scar were measured to assess the effects of Adv-hBD2-infected dMSC transplantation on the healing of irradiated wounds complicated by Pseudomonas aeruginosa infection. Results showed that the supernatant from Adv-hBD2-infected dMSCs had obvious antibacterial effects. Transplantation of Adv-hBD2-infected dMSCs killed bacteria in the wound. The complete wound healing time was 19.8 ± 0.45 days, which was significantly shorter than in the control groups (P < 0.05). From 14 days after transplantation, the residual wound area was smaller in the experimental group than in the control groups (P < 0.05). In conclusion, we found that transplantation of hBD2 genetically modified dMSCs accelerated the healing of wounds complicated by P. aeruginosa infection in whole body irradiated rats.

Bone regeneration using an acellular extracellular matrix and bone marrow mesenchymal stem cells expressing Cbfa1.

To treat bone defects, tissue-engineering methods combine an appropriate scaffold with cells and osteogenic signals to stimulate bone repair. Mesenchymal stem cells (MSCs) derived from adult bone marrow are an ideal source of cells for tissue engineering, in particular for applications in skeletal and hard tissue repair. Core binding factor alpha1 (Cbfa1) is an essential transcription factor for osteoblast differentiation. However, the effects of Cbfa1 on MSCs in vitro and in vivo have not been well characterized. In this study, we found that MSCs modified genetically to express Cbfa1 promoted the healing of segmental defects of the radius in rabbits. First, osteogenic differentiation of MSCs transfected with an adenovirus encoding Cbfa1 was demonstrated. Expression of mRNA from a number of osteoblastic marker genes, including osteocalcin, osteopontin, and type I collagen, was detected. In addition, alkaline phosphatase activity and increased osteocalcin content were observed. The cells expressing the Cbfa1 gene were then combined with acellular bone extracellular matrix in a flow perfusion culture system. Finally, the cell-matrix constructs were implanted into radius defects in the rabbit model. After 12 weeks, radiographic, histological, and biomechanical analyses showed that MSCs modified with the Cbfa1 gene resulted in a significantly higher amount of newly-formed bone and rebuilding of the marrow cavity than control cell-matrix constructs. This study indicates that MSCs modified with the Cbfa1 gene can act as suitable seed cells for the regeneration of bone defects.

CXCR4 gene transfer enhances the distribution of dermal multipotent stem cells to bone marrow in sublethally irradiated rats.

Our previous study indicated that systemically transplanted dermal multipotent cells (DMCs) were recruited more frequently to bone morrow (BM) of rats with sublethal irradiation than that of normal rats, and the interactions between stromal-derived factor (SDF-1) and its receptor (CXC chemokine receptor 4, CXCR4) played an important role in this process. In the present study, we aimed to investigate whether CXCR4 gene transfer could promote the distribution of DMCs into irradiated BM and accelerate its function recovery. Firstly, adenovirus vector of CXCR4 (Adv-CXCR4) and green fluorescent protein (Adv-GFP) were constructed. Then male DMCs infected by Adv-CXCR4 (group A), or infected by Adv-GFP (group B), and non-infected DMCs (group C) were transplanted into irradiated female rats, and real-time polymerase chain reaction for the sex-determining region of Y chromosome was employed to determined the amount of DMCs in BM. The functional recovery of BM was examined by hematopoietic progenitor colonies assay. The results showed that the amount of DMCs in BM of group A was greater than that in group B and group C from day 5 after injury (P < 0.05), and the amount of CFU-F, CFU-E and CFU-GM were greater than that in group B and group C from day 14 after injury (P < 0.05). These findings suggest that DMCs infected by Adv-CXCR4 distributed more frequently to the bone marrow of sublethally irradiated rats and could accelerate hematopoiesis function recovery.

An anatomic and histologic study of the coracohumeral ligament.

Although the anatomy and histology of the coracohumeral ligament (CHL) play an important role in the diagnosis and treatment of frozen shoulder, they remain unclear. Our objective was to study the anatomic features of the CHL and analyze its histology. Twenty-six fresh-frozen, normal cadaveric shoulders were used to examine the position and morphology of the CHL and their relationship with the superior glenohumeral ligament and to determine the CHL's histologic features in comparison with the joint capsule and coracoacromial ligament. The CHLs were all located in the rotator interval, with an irregular trapezoidal structure. The subacromial bursa was above the CHL, and the subcoracoid bursa was below the it. The CHLs in all shoulders originated from the lateral aspect of the base of the coracoid process. In 11 shoulders, it inserted into the supraspinatus tendon, whereas in 11 other shoulders, it inserted into the rotator interval. In 3 shoulders, the CHLs were split and inserted into both the supraspinatus and subscapularis tendons, respectively. Finally, the CHL in 1 shoulder only inserted into the subscapularis tendon. We also observed that the pectoralis minor tendons in 4 shoulders passed over the coracoid process top and inserted into the CHLs. In 11 shoulders, a complex of the CHL and the superior glenohumeral ligament was formed. Histologically, the CHL was found to be similar to the joint capsule without any ligament features. The position, morphology, and origin of the CHL did not change much, but its insertion varied greatly. In addition, the CHL had the histologic feature of a capsule, not a ligament.

Recruitment of transplanted dermal multipotent stem cells to sites of injury in rats with combined radiation and wound injury by interaction of SDF-1 and CXCR4.

Systemic transplantation of dermal multipotent stem cells has been shown to accelerate both hematopoietic recovery and wound healing in rats with combined radiation and wound injury. In the present study, we explored the mechanisms governing the recruitment of dermal multipotent stem cells to the sites of injury in rats with combined injury. Male dermal multipotent stem cells were transplanted into female rats, and using quantitative real-time PCR for the sex-determining region of Y chromosome, it was found that the amounts of dermal multipotent stem cells in irradiated bone marrow and wounded skin were far greater than those in normal bone marrow and skin (P < 0.01). However, incubation of dermal multipotent stem cells with AMD3100 before transplantation, which specifically blocks binding of stromal cell-derived factor 1 (SDF-1) to its receptor CXCR4, diminished the recruitment of dermal multipotent stem cells to the irradiated bone marrow and wounded skin by 58 +/- 4% and 60 +/- 4%, respectively (P < 0.05). In addition, it was confirmed that the expression of SDF-1 in irradiated bone marrow and wounded skin was up-regulated compared to that in their normal counterparts, and in vitro analysis revealed that irradiated bone marrow and wounded skin extracts had a strong chemotactic effect on dermal multipotent stem cells but that the effect decreased significantly when dermal multipotent stem cells were preincubated with AMD3100 (P < 0.05). These data suggest that transplanted dermal multipotent stem cells were recruited more frequently to the irradiated bone marrow and wounded skin than normal bone marrow and skin and that the interactions of SDF-1 and CXCR4 played a crucial role in this process.

Effects of peritoneal lavage fluid from radiation or/and burn injured rats on the growth of hematopoietic progenitor cells.

PURPOSE: To evaluate the effects of peritoneal lavage fluids from radiation injury, burn injury and combined radiation-burn injury on the growth of hematopoietic progenitor cells (HPC). MATERIALS AND METHODS: Rats were divided into four groups: A radiation group (RG), a burn group (BG), a combined radiation-burn group (CRBG) and normal control group (NG). RG and CRBG rats were irradiated with 12 Gy, and burns of 30% total body surface area were generated in group BG and group CRBG. Peritoneal lavage fluids were collected and tested for their effects on the growth of erythrocyte progenitor cells or granulocyte-macrophage progenitor cells of BALB/c mice in vitro. RESULTS: The numbers of colony forming units-erythroid (CFU-E), burst forming units-erythroid (BFU-E) and colony-forming units-granulocyte-macrophage (CFU-GM) formed after treatment with lavage fluids from BG or CRBG were significantly higher than those from NG. However, fewer CFU-E, BFU-E or CFU-GM colonies were found after treatment with lavage fluid from the RG. In lavage fluid from BG and CRBG, the concentration of interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor alpha (TNFalpha) was increased in comparison to NG and RG. Treatment with these cytokines had similar promoting effects on the growth of hematopoietic colonies and neutralizing antibodies inhibited these effects significantly. CONCLUSIONS: Burns increase the responsiveness of the system and help the proliferation of hematipoietic progenitor cells, while radiation decreases all these responses relative to both the controls and the burn plus radiation group.

The zinc finger protein A20 protects endothelial cells from burns serum injury.

Burn injuries as well as skin damages are often associated with immune suppression and often cause multiple organ failures. The monolayer endothelium is vulnerable to injuries from circulating factors resulting from remote wounds. Endothelial cell activation and apoptosis can alter microvascular permeability and intensify organ damage. A20, as a physiological cytoprotective gene is essential for preventing spontaneous innate immune cell-mediated inflammation and tissue destruction. It is not known whether A20 has the function to protect endothelial cells from the effect of burns serum challenge on endothelial function in vitro. This study shows that A20 can express in endothelial cells after burns serum stimulation and inhibit endothelial cell activation and apoptosis induced by burns serum. These results suggest that A20 may be beneficial in limiting the response to burn injuries.