Mesenchymal stem cell proliferation and differentiation on load-bearing trabecular Nitinol scaffolds

Bone tissue regeneration in load-bearing regions of the body requires high-strength porous scaffolds capable of supporting angiogenesis and osteogenesis. 70% porous Nitinol (NiTi) scaffolds with a regular 3-D architecture resembling trabecular bone were produced from Ni foams using an original reactive vapor infiltration technique. The “trabecular Nitinol” scaffolds possessed a high compressive strength of 79 MPa and high permeability of 6.9 × 10^?6 cm². The scaffolds were further modified to produce a near Ni-free surface layer and evaluated in terms of Ni ion release and human mesenchymal stem cell (hMSC) proliferation (AlamarBlue), differentiation (alkaline phosphatase activity, ALP) and mineralization (Alizarin Red S staining). Scanning electron microscopy was employed to qualitatively corroborate the results. hMSCs were able to adhere and proliferate on both as-produced and surface-modified trabecular NiTi scaffolds, to acquire an osteoblastic phenotype and produce a mineralized extracellular matrix. Both ALP activity and mineralization were increased on porous scaffolds compared to control polystyrene plates. Experiments in a model coculture system of microvascular endothelial cells and hMSCs demonstrated the formation of prevascular structures in trabecular NiTi scaffolds. These data suggest that load-bearing trabecular Nitinol scaffolds could be effective in regenerating damaged or lost bone tissue.     

Flow perfusion culture of human mesenchymal stem cells on coralline hydroxyapatite scaffolds with various pore sizes

Bone grafts are widely used in orthopaedic reconstructive surgery, but harvesting of autologous grafts is limited due to donor site complications. Bone tissue engineering is a possible alternative source for substitutes, and to date, mainly small scaffold sizes have been evaluated. The aim of this study was to obtain a clinically relevant substitute size using a direct perfusion culture system. Human bone marrowderived mesenchymal stem cells were seeded on coralline hydroxyapatite scaffolds with 200 μm or 500 μm pores, and resulting constructs were cultured in a perfusion bioreactor or in static culture for up to 21 days and analysed for cell distribution and osteogenic differentiation using histological stainings, alkaline phosphatase activity assay, and real-time RT-PCR on bone markers. We found that the number of cells was higher during static culture at most time points and that the final number of cells was higher in 500 μm constructs as compared with 200 μm constructs. Alkaline phosphatase enzyme activity assays and real time RT-PCR on seven osteogenic markers showed that differentiation occurred primarily and earlier in statically cultured constructs with 200 μm pores compared with 500 μm ones. Adhesion and proliferation of the cells was seen on both scaffold sizes, but the vitality and morphology of cells changed unfavorably during perfusion culture. In contrast to previous studies using spinner flask that show increased cellularity and osteogenic properties of cells when cultured dynamically, the perfusion culture in our study did not enhance the osteogenic properties of cell/scaffold constructs. The statically cultured constructs showed increasing cell numbers and abundant osteogenic differentiation probably because of weak initial cell adhesion due to the surface morphology of scaffolds. Our conclusion is that the specific scaffold surface microstructure and culturing system flow dynamics has a great impact on cell distribution and proliferation and on osteogenic differentiation, and the data presented warrant careful selection of in vitro culture settings to meet the specific requirements of the scaffolds and cells, especially when natural biomaterials with varying morphology are used.     

Effects of bone ingrowth on the strength and non-invasive assessment of a coralline hydroxyapatite material

The dependence of strength on the amount of bone growth into a hydroxyapatite material made from coral was investigated. Block and granular forms of the material were implanted into cortical and trabecular regions of the skeletons of 16 dogs. The results were examined after 4, 8, 12 and 16 wk, with four dogs in each experimental group. When implanted into cortical bone, the bending strength of the implant material was found to be highly correlated with the amount of pore space which had become occupied by bone (r = 0.92, P less than 0.005 for the block form; r = 0.84, P less than 0.005 for the granular form). Multiple regression analysis showed that six histomorphometric measures of ingrowth accounted for 96% of the variability in bending strength of the block material, and there were no significant differences between block and granular forms of the material. On the other hand, when implanted into trabecular bone, the block form of the material achieved greater compressive strength than the granular form. While both strength and ingrowth increased with time, there were poor correlations between these two variables. Finally, when the material is implanted into trabecular bone, it becomes stronger in compression than the surrounding bone; when implanted in cortical bone, linear modelling suggests that resorption and replacement of the implant would be required to approximate the bending strength of the surrounding bone.     

Mesenchymal stem cell stimulation of tissue growth depends on differentiation state

The osteochondral microenvironment involves a complex milieu of cues that facilitate proper tissue development, homeostasis, and repair. This environment is disrupted in disease states such as osteoarthritis. Mesenchymal stem cells (MSCs) are under clinical investigation for the treatment of osteoarthritis given their capacity to differentiate into chondrocytes as well as to secrete a wide array of biologically active factors that support cell proliferation and tissue formation. In fact, the therapeutic action of these cells in many clinical applications is now thought to be at least partially dependent on their secretory capacity. Previous work demonstrated that MSCs were capable of stimulating chondrocyte growth and tissue production, whereas tissue-derived osteoblasts were not stimulatory. This study investigated the stimulatory capacity of MSCs during osteogenesis and the impact of MSC phenotype on cartilage stimulation. Cell interactions were examined in 3 coculture systems to confirm that trends were not dependent on material: traditional cell culture insert coculture, bilayered poly(ethylene glycol) gels, and a scaffold comprised of a layer of poly(ethylene glycol) polymerized onto a poly(lactic-co-glycolic) acid-based scaffold. Results demonstrated that MSCs predifferentiated toward an osteogenic phenotype for 3 days exhibited enhanced stimulation of chondrocyte extracellular matrix production, whereas longer periods of predifferentiation decreased the magnitude of observed stimulation. Further, tissue formation by the MSCs themselves showed greater dependence on the coculture system than the presence of other cells or length of predifferentiation.     

Comparing hydroxyapatite with osteogenic medium for the osteogenic differentiation of mesenchymal stem cells on PHBV nanofibrous scaffolds

Having advantageous biocompatibility and osteoconductive properties known to enhance the osteogenic differentiation of mesenchymal stem cells (MSCs), hydroxyapatite (HA) is a commonly used material for bone tissue engineering. What remains unclear, however, is whether HA holds a similar potential for stimulating the osteogenic differentiation of MSCs to that of a more frequently used osteogenic-inducing medium (OIM). To that end, we used PHBV electrospun nanofibrous scaffolds to directly compare the osteogenic capacities of HA with OIM over MSCs. Through the observation of cellular morphology, the staining of osteogenic markers, and the quantitative measuring of osteogenic-related genes, as well as microRNA analyses, we not only found that HA was as capable as OIM for differentiating MSCs down an osteogenic lineage; albeit, at a significantly slower rate, but also that numerous microRNAs are involved in the osteogenic differentiation of MSCs through multiple pathways involving the inhibition of cellular proliferation and stemness, chondrogenesis and adipogenesis, and the active promotion of osteogenesis. Taken together, we have shown for the first time that PHBV electrospun nanofibrous scaffolds combined with HA have a similar osteogenic-inducing potential as OIM and may therefore be used as a viable replacement for OIM for alternative in vivo-mimicking bone tissue engineering applications.     

间质干细胞、肿瘤干细胞和肿瘤

近来研究认为肿瘤来源于干细胞,提出了肿瘤中存在极少量肿瘤干细胞(CSC)的新学说.问质干细胞(MSC)作为间质细胞的来源,与肿瘤的关系尤为密切.本文就间质干细胞,肿瘤干细胞和肿瘤的发生,发展作一综述.     

The effects of soluble growth factors on embryonic stem cell differentiation inside of fibrin scaffolds

The goal of this research was to determine the effects of different growth factors on the survival and differentiation of murine embryonic stem cell-derived neural progenitor cells (ESNPCs) seeded inside of fibrin scaffolds. Embryoid bodies were cultured for 8 days in suspension, retinoic acid was applied for the final 4 days to induce ESNPC formation, and then the EBs were seeded inside of three-dimensional fibrin scaffolds. Scaffolds were cultured in the presence of media containing different doses of the following growth factors: neurotrophin-3 (NT-3), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF)-AA, ciliary neurotrophic factor, and sonic hedgehog (Shh). The cell phenotypes were characterized using fluorescence-activated cell sorting and immunohistochemistry after 14 days of culture. Cell viability was also assessed at this time point. Shh (10 ng/ml) and NT-3 (25 ng/ml) produced the largest fractions of neurons and oligodendrocytes, whereas PDGF (2 and 10 ng/ml) and bFGF (10 ng/ml) produced an increase in cell viability after 14 days of culture. Combinations of growth factors were tested based on the results of the individual growth factor studies to determine their effect on cell differentiation. The incorporation of ESNPCs and growth factors into fibrin scaffolds may serve as potential treatment for spinal cord injury.     

Mesenchymal stem cell differentiation to neuronal cells on electrospun nanofibrous substrates for nerve tissue engineering

Bone marrow Mesenchymal stem cells capable of differentiating into neuronal cells on engineered nanofibrous scaffolds have great potential for bionanomaterial–cell transplantation therapy of neurodegenerative diseases and injuries of the nervous system. MSCs have been the highlight of many tissue engineering studies mainly because of their multipotential properties. We investigated the potential of human bone marrow derived Mesenchymal stem cells (MSCs) for neuronal differentiation in vitro on poly(l-lactic acid)-co-poly-(3-caprolactone)/Collagen (PLCL/Coll) nanofibrous scaffolds. PLCL and PLCL/Coll nanofibrous scaffolds were fabricated by electrospinning process and their chemical and mechanical characterizations were carried out using SEM, contact angle, FTIR, and tensile instrument. The differentiation of MSCs was carried out using neuronal inducing factors including β-mercaptoethanol, epidermal growth factor, nerve growth factor and brain derived growth factor in DMEM/F12 media. The proliferations of MSCs evaluated by MTS assay showed that the cells grown on PLCL/Coll nanofibrous scaffolds were comparatively higher (80%) than those on PLCL. Scanning electron microscopy results showed that MSCs differentiated on PLCL/Coll nanofibrous scaffolds showed neuronal morphology, with multipolar elongations and expressed neurofilament and nestin protein by immuno-fluorescent microscopy. Our studies on the differentiation of MSCs to neuronal cells on nanofibrous scaffolds suggest their potential application towards nerve regeneration.     

Endothelial cell migration and morphogenesis on silk fibroin scaffolds containing hydroxyapatite electret

The purpose of this study was to evaluate the effects of composite wound dressing films made of silk fibroin (SF) containing hydroxyapatite (HA) or polarized HA (pHA) powders on endothelial cell (EC) behaviors that have important roles in the wound-healing process. XRD revealed the SF films to be semicrystalline, with a broad peak centered at about 20.7° which is characteristic of β-sheets embedded within an amorphous matrix. The SF composite films with 0.6 (w/v)% in concentration of HA powder (HA/SF) or pHA powder (pHA/SF) contained HA crystals of amorphous and silk II crystalline structures. SEM observation showed that there were differences in SF morphology between HA/SF and pHA/SF. The pHA/SF exhibited a furry texture around the pHA crystals, most likely due to the stored charged and zeta potentials. The HA/SF and pHA/SF films enhanced EC migration compared with that on the SF film. The number of migrated cells on the HA/SF and pHA/SF was ~1.5 times larger than that on the SF. The quantitative analysis of the endothelial morphogenesis indicated that the pHA/SF film enhanced the formation of capillary-like structures compared with SF and HA/SF. Thus, pHA/SF may potentially stimulate and contribute to the enhancement of angiogenesis in the wound-healing process.     

Freeform fabricated scaffolds with roughened struts that enhance both stem cell proliferation and differentiation by controlling cell shape

We demonstrate that freeform fabricated (FFF) scaffolds with a roughened surface topography can support hBMSC proliferation, while also inducing osteogenic differentiation, for maximized generation of calcified, bone-like tissue. Previously, hBMSCs rapidly proliferated, without osteogenic differentiation, during culture in FFF scaffolds. In contrast, hBMSCs underwent osteogenic differentiation, with slow proliferation, during culture in nanofiber scaffolds. Analysis of cell morphology showed that the topography presented by the nanofiber scaffolds drove hBMSC differentiation by guiding them into a morphology that induced osteogenic differentiation. Herein, we hypothesized that using the high-surface area architecture of FFF scaffolds to present a surface roughness that drives hBMSCs into a morphology that induces osteogenic differentiation would yield a maximum amount differentiated hBMSCs and bone-like tissue. Thus, a solvent etching method was developed that imparted a 5-fold increase in roughness to the surface of the struts of poly(ε-caprolactone) (PCL) FFF scaffolds. The etched scaffolds induced osteogenic differentiation of the hBMSCs while un-etched scaffolds did not. The etched scaffolds also supported the same high levels of hBMSC proliferation that un-etched scaffolds supported. Finally, hBMSCs on un-etched scaffolds had a large spread area, while hBMSCs on etched scaffolds has a smaller area and were more rounded, indicating that the surface roughness from the etched scaffolds dictated the morphology of the hBMSCs. The results demonstrate that FFF scaffolds with surface roughness can support hBMSC proliferation, while also inducing osteogenic differentiation, to maximize generation of calcified tissue. This work validates a rational approach to scaffold fabrication where the structure of the scaffold was designed to optimize stem cell function by controlling cell morphology.     

Mesenchymal stem cells enhance wound healing through differentiation and angiogenesis

Although chronic wounds are common, treatment for these disabling conditions remains limited and largely ineffective. In this study, we examined the benefit of bone marrow-derived mesenchymal stem cells (BM-MSCs) in wound healing. Using an excisional wound splinting model, we showed that injection around the wound and application to the wound bed of green fluorescence protein (GFP)(+) allogeneic BM-MSCs significantly enhanced wound healing in normal and diabetic mice compared with that of allogeneic neonatal dermal fibroblasts or vehicle control medium. Fluorescence-activated cell sorting analysis of cells derived from the wound for GFP-expressing BM-MSCs indicated engraftments of 27% at 7 days, 7.6% at 14 days, and 2.5% at 28 days of total BM-MSCs administered. BM-MSC-treated wounds exhibited significantly accelerated wound closure, with increased re-epithelialization, cellularity, and angiogenesis. Notably, BM-MSCs, but not CD34(+) bone marrow cells in the wound, expressed the keratinocyte-specific protein keratin and formed glandular structures, suggesting a direct contribution of BM-MSCs to cutaneous regeneration. Moreover, BM-MSC-conditioned medium promoted endothelial cell tube formation. Real-time polymerase chain reaction and Western blot analysis revealed high levels of vascular endothelial growth factor and angiopoietin-1 in BM-MSCs and significantly greater amounts of the proteins in BM-MSC-treated wounds. Thus, our data suggest that BM-MSCs promote wound healing through differentiation and release of proangiogenic factors. Disclosure of potential conflicts of interest is found at the end of this article.     

基底膜基质/壳聚糖诱导骨髓间充质干细胞成软骨分化

背景：课题组前期研究发现基底膜基质能够定向诱导骨髓间充质干细胞向软骨方向分化,但其力学性能与实际应用有较大差距,还需要进一步研究。 目的：制备兼具适宜力学性能和优异生物相容性的壳聚糖/基底膜基质水凝胶支架用于软骨修复。 方法：以京尼平为交联剂,将壳聚糖溶液与基底膜基质按2︰1,1︰1,1︰3比例混合制成水凝胶,接种大鼠骨髓间充质干细胞,培养14 d。经材料力学测试、细胞增殖、活细胞染色、酶联免疫吸附测试以及阿尔新蓝染色等方法评价材料诱导细胞成软骨分化能力。 结果与结论：在基底膜基质内添加壳聚糖后,材料力学性能从0.48 kPa上升到1.78 kPa。标志性蛋白分泌结果显示,纯壳聚糖组早期诱导成软骨活性高于其他组,但后期诱导能力减弱,而含基底膜基质各组在后期能够保持较好的诱导活性,其中壳聚糖/基底膜基质=1︰1组材料具有一定的力学强度,且Ⅱ型胶原和Ⅹ型胶原的表达量在14 d较其他组高。结果表明实验制备的壳聚糖/基底膜基质水凝胶具有良好的力学性能,并能够促进骨髓间充质干细胞向软骨方向分化,可用于软骨组织工程研究。 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

Neurotrophin-induced differentiation of human embryonic stem cells on three-dimensional polymeric scaffolds

Human embryonic stem (hES) cells have the potential to form various cell types, including neural cells for the treatment of diseases such as Parkinson's, spinal cord injury, and glaucoma. Here, we have investigated the neuronal differentiation of hES cells on three-dimensional scaffolds fabricated from degradable poly(alpha-hydroxy esters) including poly(lactic-co-glycolic acid) and poly(L-lactic acid). When cultured in vitro, neural rosette-like structures developed throughout the scaffolds with differentiation dependent on factors in the medium (e.g., retinoic acid [RA], nerve growth factor [NGF], and neurotrophin 3 [NT-3]) and the differentiation stage of the cells. Specifically, enhanced numbers of neural structures and staining of nestin (a marker of neural precursors) and beta(III)-tubulin (indicative of neural differentiation) were observed with hES cell-seeded polymer scaffolds when cultured with both NGF and NT-3 when compared with control medium. In addition, vascular structures were found throughout the engineered tissues when cultured with the neurotrophins, but not in the presence of RA.     

Optical control of cell differentiation on synthetic collagen-like scaffolds

Abstract

We have developed biocompatible scaffolds that enable cell fate control with visible light. The scaffolds are based on synthetic collagen-like polypeptide, poly(prolyl-hydroxyprolyl-glycyl) {poly(Pro-Hyp-Gly)} which has been used for cosmetics and other healthcare applications. Bioactive peptides were conjugated to the scaffolds via photoactivation reaction utilizing 488?nm visible light. In addition, the use of a photocleavable crosslinker enables dissociation of chemical moieties by 405?nm laser irradiation. The synthesis scheme enables optical control to attach and detach functional peptides in pre-patterned shapes. Using bone forming peptide (BFP), we demonstrate that calcium deposition by rat bone stromal cells can be directed on the scaffold. Using other signaling molecules and three-dimensional scaffolds, controlled differentiation of stem cells can be achieved by spatio-temporally specific irradiation of confocal microscope laser.     

增强型绿色荧光蛋白标记骨髓间充质干细胞与表面置换珊瑚人工骨的培养

目的通过增强型绿色荧光蛋白（eGFP）标记的人骨髓间充质干细胞（MSC）与表面置换珊瑚羟基磷灰石（SCHA）培养．研究SCHA与细胞黏附、增殖的情况。方法将海南天然滨珊瑚在特定温度和压力下部分水热反应,制成SCHA。将SCHA薄片（SCHA组）和盖玻片（玻片组）分别与eGFP标记的人骨髓MSC体外培养,分别于4、8、12、16d进行死活细胞染色和Alamar Blue实验,用荧光显微镜观察细胞活性,荧光分光光度计测量细胞增殖。结果人骨髓MSC在SCHA的表面和孔道内生长良好,第8天、第16天与玻片组达同样水平,之后超过玻片组并保持稳定状态。结论SCHA无细胞毒性,具有较好的细胞相容性,是一种良好的骨组织工程支架材料。     

Characterization of zinc-releasing three-dimensional bioactive glass scaffolds and their effect on human adipose stem cell proliferation and osteogenic differentiation

While the addition of zinc ions to bioactive ceramics has been shown to enhance the proliferation and osteogenic differentiation of osteoblast-like cells, contradictory results have been found. Therefore, the effect of zinc-releasing ceramics on cell proliferation and differentiation into osteogenic lineages requires further clarification. The aim of this study was to evaluate the effects of zinc addition on the degradation profile of three-dimensional bioactive glass scaffold, and on the proliferation and osteogenesis of human adipose stem cells (hASCs) in these scaffolds. Bioactive glass scaffolds containing Na₂O, K₂O, MgO, CaO, B₂O₃, TiO₂, P₂O₅ and SiO₂ were prepared. The degradation was evaluated by weight loss measurement, scanning electron microscopy and elemental analysis. The degradation profile of bioactive glass was shown to slow down with the addition of zinc. Qualitative live/dead staining showed that zinc addition to bioactive glass inhibits cell spreading and proliferation of hASCs. However, zinc addition had no significant effect on DNA content, alkaline phosphatase activity and osteopontin concentration of hASCs when measured quantitatively. Our results suggest that the possible stimulatory effect of addition of zinc on hASC proliferation and osteogenesis was not detected because addition of zinc slowed down the degradation rate of the studied bioactive glass scaffolds.     

MicroCT analysis of hydroxyapatite bone repair scaffolds created via three-dimensional printing for evaluating the effects of scaffold architecture on bone ingrowth

Recent studies have shown that it is now possible to construct tissue-engineered bone repair scaffolds with tight pore size distributions and controlled geometries using 3-D Printing techniques (3DP). This study evaluated two hydroxyapatite (HA) 8-mm diameter discs with controlled architectures in a rabbit trephine defect at 8 and 16 weeks using a 2 x 2 factorial design. Input parameters were time and scaffold void volume at two levels. Three output variables were extracted from MicroCT data: bone volume ingrowth with respect to total region of interest, bone volume ingrowth with respect to available ingrowth volume, and soft tissue volume. The experiment measured two groups--Group 1: 500-microm x 500-microm channels parallel to the scaffold's long axis and penetrating up 3-mm from the bottom. Group 2: 800-microm x 800-microm struts spaced 500 microm apart set perpendicularly to each other in each printed layer. Rendered 3-dimensional MicroCT scans and undecalcified histological slides of implants revealed good integration with the surrounding tissue, and a sizeable amount of bone ingrowth into the device. Factorial analysis revealed that the effects of time were the greatest determinant of soft tissue ingrowth, while time and its interaction with void volume were the greatest determinants of bone volume ingrowth with respect to both total and available volume.     

3D打印钛合金孔隙支架骨长入影响因素的分析

BACKGROUND: With the development of three-dimensional (3D) printing technology, 3D printed porous titanium scaffolds as bone substitutes have become a research hotspot. OBJECTIVE: To introduce and discuss the effects of each parameter of 3D printed porous titanium scaffolds on bone ingrowth, and to sum out the optimal parameters for bone ingrowth. METHODS: The first author retrieved PubMed, Springerlink and Medline databases with “three-dimensional (3D) printing, scaffold, titanium, bone ingrowth” as keywords for relevant articles published from 2006 to 2016. 125 articles were retrieved initially, and finally 42 eligible articles were included for analysis. RESULTS AND CONCLUSION: Pore size, porosity, pore structures and surface modifications of 3D printed porous titanium scaffolds all make effects on bone ingrowth or osteoblasts in scaffolds. Scaffolds with appropriate pore size and porosity can promote the vascularization and provide adequate nutrition and oxygen supplement, to ensure high cell viability. Regulations of cell performances, such as cell attachment, proliferation and differentiation, are also affected by pore structures and nano-scale surface modification. Herein, a detailed combination of the parameters, as mentioned above, can create a better porous scaffold for better bone ingrowth. Hence, the high-stability interface between bone and scaffolds may be obtained through the parameter adjustment.