Self‐Assembled Peptide‐Based Hydrogels as Scaffolds for Proliferation and Multi‐Differentiation of Mesenchymal Stem Cells

Fluorenyl‐9‐methoxycarbonyl (Fmoc)‐diphenylalanine (Fmoc‐FF) and Fmoc‐arginine‐glycine‐­aspartate (Fmoc‐RGD) peptides self‐assemble to form a 3D network of supramolecular hydrogel (Fmoc‐FF/Fmoc‐RGD), which provides a nanofibrous network that uniquely presents bioactive ligands at the fiber surface for cell attachment. In the present study, mesenchymal stem cells (MSCs) in Fmoc‐FF/Fmoc‐RGD hydrogel increase in proliferation and survival compared to those in Fmoc‐FF/Fmoc‐RGE hydrogel. Moreover, MSCs encapsulated in Fmoc‐FF/Fmoc‐RGD hydrogel and induced in each defined induction medium undergo in vitro osteogenic, adipogenic, and chondrogenic differentiation. For in vivo differentiation, MSCs encapsulated in hydrogel are induced in each defined medium for one week, followed by injection into gelatin sponges and transplantation into immunodeficient mice for four weeks. MSCs in Fmoc‐FF/Fmoc‐RGD hydrogel increase in differentiation into osteogenic, adipogenic, and chondrogenic differentiation, compared to those in Fmoc‐FF/Fmoc‐RGE hydrogel. This study concludes that nanofibers formed by the self‐assembly of Fmoc‐FF and Fmoc‐RGD are suitable for the attachment, proliferation, and multi‐differentiation of MSCs, and can be applied in musculoskeletal tissue engineering.

     

Incorporation of carboxylation multiwalled carbon nanotubes into biodegradable poly(lactic-co-glycolic acid) for bone tissue engineering

Biodegradable poly(lactic-co-glycolic acid) (PLGA)/carboxyl-functionalized multi-walled carbon nanotube (c-MWCNT) nanocomposites were successfully prepared via solvent casting technique. Rat bone marrow-derived mesenchymal stem cells (MSCs) were employed to assess the biocompatibility of the nanocomposites in vitro. Scanning electron microscopy (SEM) observations revealed that c-MWCNTs gave a better dispersion than unmodified MWCNTs in the PLGA matrix. Surface properties were determined by means of static contact angle, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis. The presence of c-MWCNTs increased the mechanical properties of the nanocomposites. Seven-week period in vitro degradation test showed the addition of c-MWCNTs accelerated the hydrolytic degradation of PLGA. In addition, SEM proved that the cells could adhere to and spread on films via cytoplasmic processes. Compared with control groups, MSCs cultured onto PLGA/c-MWCNT nanocomposites exhibited better adhesion and viability and also displayed significantly higher production levels of alkaline phosphatase (ALP) over 21 days culture. These results demonstrated that c-MWCNTs modified PLGA films were beneficial for promoting cell growth and inducing MSCs to differentiate into osteoblasts. This work presented here had potential applications in the development of 3-D scaffolds for bone tissue engineering.     

The use of poly(L-lactide-co-caprolactone) as a scaffold for adipose stem cells in bone tissue engineering: application in a spinal fusion model

Since the early 1990s, tissue engineering has been heralded as a strategy that may solve problems associated with bone grafting procedures. The original concept of growing bone in the laboratory, however, has proven illusive due to biological, logistic, and regulatory problems. Fat-derived stem cells and synthetic polymers open new, more practicable routes for bone tissue engineering. In this paper, we highlight the potential of poly(L-lactide-co-caprolactone) (PLCL) to serve as a radiolucent scaffold in bone tissue engineering. It appears that PLCL quickly and preferentially binds adipose stem cells (ASCs), which proliferate rapidly and eventually differentiate into the osteogenic phenotype. An in vivo spinal fusion study in a goat model provides a preclinical proof-of-concept for a one-step surgical procedure with ASCs in bone tissue engineering.     

The influence of patterned nanofiber meshes on human mesenchymal stem cell osteogenesis

A specially designed electroconductive collector enables the electrospinning of P-NFM composed of areas of parallel/uniaxially aligned fibers and areas of random/orthogonal nanofiber distribution. The biological relevance of P-NFM is demonstrated using hBMSCs as an autologous cell source. The structures induce cell orientation along the uniaxially aligned fibers, mainly during earlier culturing periods under basal and osteogenic differentiation conditions. The microtopography of the P-NFM also controls the deposition of mineralized extracellular matrix along the pre-defined fiber direction. Genotypic characterization confirms the successful differentiation into the osteogenic lineage.     

Covalent growth factor immobilization strategies for tissue repair and regeneration

Growth factors play a critical role in regulating processes involved in cellular differentiation and tissue regeneration, and are therefore considered essential elements in many tissue engineering strategies. The covalent immobilization of growth factors to biomaterial matrices addresses many of the challenges associated with delivering freely-diffusible growth factors and has thus emerged as a promising method of achieving localized and sustained growth factor delivery. This Feature Article discusses methods that have been used to immobilize growth factors to substrates, followed by an overview of several tissue repair and regeneration applications in which immobilized growth factors have been used.     

高效液相色谱法检测紫苏梗提取物活性成分及抗氧化效果

用乙酸乙酯、 氯仿、 正丁醇等有机试剂和水分别提取中草药紫苏梗的有效成分, 得到有机酸类、 三萜类和黄酮类化合物, 并研究其抗氧化效果. 结果表明: 紫苏梗正丁醇相中没食子酸的质量比为0.6 g/kg; 氯仿相中三萜类化合物齐墩果酸的质量比为0.9 g/kg; 紫苏梗提取物中黄铜类化合物质量比相对较高, 在乙酸乙酯相中为1.2 g/kg, 氯仿相中为1.1 g/kg; 紫苏梗各提取物对·OH自由基、 超氧自由基(·O-2)和DPPH·均有一定的清除能力, 其中1 mg/mL的乙酸乙酯相和氯仿相的清除能力最强, 分别为79%和73%、 62%和59%、 83%和80%, 对·OH自由基和DPPH·的清除能力相对较强, 即紫苏梗各提取物均具有显著的抗氧化效果.     

The biological characteristics of different generation mesenchymal stem cells cultured in vitro and cocultured with vascular scaffold

Mesenchymal stem cells (MSCs) were used widely as seed cells in tissue engineering blood vessel construction. However, the biological characteristics difference of different generation MSCs in vitro culture is unknown, which laid a foundation for appropriate generation seeded cells selection for tissue engineering blood vessel construction. In this report, MSCs were isolated from SD rat bone marrow and identified by flow cytometry; cell growth curve test, cell surface antigen expression rate detection, cryopreservation resuscitation rate test, CD31 expression rate test, cell cycle analysis, and adhesion difference on vascular scaffold test were performed. The research results indicated that the MSCs shape was spindle and uniform with vigorous growth. CD105 and CD90 factor expression rate reached 82.5 and 84.9%, respectively, and the expression rate of CD45 was only 7.3%. The proliferation capacity of the fourth generation MSCs were more exuberant, with proliferation index as 20.3%; the cell proliferation index of the eighth generation decreased to only 9.1%. The cryopreservation resuscitation rate of the second generation and fourth generation MSCs were both higher than 80%, and the cryopreservation resuscitation rate of the eighth generation MSCs was only about 60%. After the induction for 5 days, MSCs had weak CD31 expression, and with the prolonged induction time, expression increased. All generation MSCs expressed CD31 after being induced for 10 days; however, the CD31 positive expression rate of the second generation, fourth generation, and sixth generation MSCs had significant difference with the eighth generation MSCs. Adhesion rate of MSCs before sixth generation was around 40%, but the adhesion rate of eighth generation MSCs was only about 27%. In all, biological characteristics of different generation MSCs existed certain differences, and especially the eighth generation MSCs aged seriously, whose cell activity decreased significantly. The researchers believed that the MSCs before the sixth generation can maintain excellent properties of MSCs, and can be used as seed cells for vascular tissue engineering.     

外来种喜旱莲子草的克隆生长特性

通过对外来种喜旱莲子草（Alternanthera philoxeroides（Mart．）Griseb）生长指标的测定和分析，研究了它的克隆生长规律，并探讨丁它的觅食行为．在一个生长季节内，喜旱莲子草生物量增加了近30倍，一级葡萄茎分株数增加了近50倍，最长的一级葡萄茎长度增长了近40倍，一级葡萄茎总长度增长了近13倍；一、二、三级葡萄茎上的总分株数增加了近130倍，3个级别匍匍苇总长度增长了近28倍．通过各级葡萄茎个数，葡萄茎总长度和葡萄茎总分株数比较发现，二级葡萄茎比一、二级葡萄苇生长的都要快，而一级葡萄茎的间隔物平均长度远远大于二级和三级葡萄茎．克隆植物的觅食行为与它的克隆生长紧密相连，从觅食行为来看，喜旱莲子草克隆构型随生长季节的变化说明了它对生长季节具有很强的适应性．这种快速克隆生长的特性和对生长季节的适应性有利于喜旱莲子成功入侵新的生境。     

考虑死亡风险下权益指数年金的定价

权益指数年金(Equity Indexed Annuities)是欧美市场近十年发展起来的一类新型年金产品,有最小收益保证,在最小保证基础上与预先设定好的某类股指收益相关联．本文在考虑死亡风险情况下,对简单点对点和年度重设两种指数计算方法下权益指数年金的定价问题作了研究,给出了定价公式并对参与率作了敏感性分析．