Role of adipose-derived stromal cells in pedicle skin flap survival in experimental animal models

The use of skin flaps in reconstructive surgery is the first-line surgical treatment for the reconstruction of skin defects and is essentially considered the starting point of plastic surgery. Despite their excellent usability, their application includes general surgical risks or possible complications, the primary and most common is necrosis of the flap. To improve flap survival, researchers have used different methods, including the use of adiposederived stem cells, with significant positive results. In our research we will report the use of adipose-derived stem cells in pedicle skin flap survival based on current literature on various experimental models in animals.     

骨形成蛋白Ⅱ型突变受体基因转染对口腔鳞癌细胞增殖和凋亡的影响

目的探讨骨形成蛋白（BMPs）与口腔鳞癌的发生、发展的可能关系。方法将含有BMP-Ⅱ突变受体的真核表达载体转染入Tea8113舌癌细胞,筛选和鉴定后,构建稳定表达BMP-Ⅱ突变受体的细胞株tBRⅡ-Tea8113。对tBRⅡ—Tca8113细胞和Tca8113细胞分别进行MTT检测,流式细胞仪（FCM）分析、BrdU标记检测细胞的增殖活性及DNA合成;检测tBRⅡ-Tca8113细胞和Tea8113细胞的凋亡及细胞周期相关因子（CyclinD1,CDK-4,p27,p57）的表达。结果Tea8113细胞和tBRⅡ-Tea8113细胞的增殖指数MTT检测为0．47±0．01和0．35±0．008（t=22．953,P=0．000）,BrdU检测为12．0±3．4和23．0±1．9（f=6．918,P=0．000）,FCM检测为6.3和7．9;两组的凋亡指数为3．7±1．2和8．7±1．6（t=29．583,P=0．000）;细胞周期因子在Tca8113和tBRⅡ-ca8113细胞中的平均灰度测量值为CyclinD1（186．5±2．4和145．6±3．9,t=28．244,P=0．000）,CDK4（169．9±2．9和129．5±3．2,t=29．583,P=0．000）,p27（110．1±1．1和167．34-1．8,f=85．754,P=0．000）,p57（107．9±2．1和156．8±2．2,t=50．844,P=0．000）。结论BMPs及其受体可能在口腔上皮组织的恶变过程中有重要作用,研究结果为探讨BMPs信号在上皮性肿瘤中的作用提供了重要依据。tBRⅡ-Tea8113细胞的建立,进一步表明了BMPs及其受体在口腔上皮组织的恶变过程中有重要作用,并为进一步探讨BMP信号在上皮性肿瘤的恶变过程中的作用奠定了基础。     

CD271 as a marker to identify mesenchymal stem cells from diverse sources before culture

Mesenchymal stem cells, due to their characteristics are ideal candidates for cellular therapy. Currently, in culture these cells are defined by their adherence to plastic, specific surface antigen expression and multipotent differentiation potential. However, the in vivo identification of mesenchymal stem cells, before culture, is not so well established. Pre-culture identification markers would ensure higher purity than that obtained with selection based on adherence to plastic. Up until now, CD271 has been described as the most specific marker for the characterization andpurification of human bone marrow mesenchymal stem cells. This marker has been shown to be specifically expressed by these cells. Thus, CD271 has been proposed as a versatile marker to selectively isolated and expand multipotent mesenchymal stem cells with both immunosuppressive and lymphohematopoietic engraftment-promoting properties. This review focuses on this marker, specifically on identification of mesenchymal stem cells from different tissues. Literature revision suggests that CD271 should not be defined as a universal marker to identify mesenchymal stem cells before culture from different sources. In the case of bone marrow or adipose tissue, CD271 could be considered a quite suitable marker; however this marker seems to be inadequate for the isolation of mesenchymal stem cells from other tissues such as umbilical cord blood or wharton’s jelly among others.     

Bone marrow microenvironment: The guardian of leukemia stem cells

Bone marrow microenvironment(BMM) is the main sanctuary of leukemic stem cells(LSCs) and protects these cells against conventional therapies. However, it may open up an opportunity to target LSCs by breaking the close connection between LSCs and the BMM. The elimination of LSCs is of high importance, since they follow cancer stem cell theory as a part of this population. Based on cancer stem cell theory, a cell with stem cell-like features stands at the apex of the hierarchy and produces a heterogeneous population and governs the disease.Secretion of cytokines, chemokines, and extracellular vesicles, whether through autocrine or paracrine mechanisms by activation of downstream signaling pathways in LSCs, favors their persistence and makes the BMM less hospitable for normal stem cells. While all details about the interactions of the BMM and LSCs remain to be elucidated, some clinical trials have been designed to limit these reciprocal interactions to cure leukemia more effectively. In this review, we focus on chronic myeloid leukemia and acute myeloid leukemia LSCs and their milieu in the bone marrow, how to segregate them from the normal compartment, and finally the possible ways to eliminate these cells.     

A comparative molecular dynamics study on BACE1 and BACE2 flap flexibility

Beta-amyloid precursor protein cleavage enzyme1 (BACE1) and beta-amyloid precursor protein cleavage enzyme2 (BACE2), members of aspartyl protease family, are close homologs and have high similarity in their protein crystal structures. However, their enzymatic properties are different, which leads to different clinical outcomes. In this study, we performed sequence analysis and all-atom molecular dynamic (MD) simulations for both enzymes in their ligand-free states in order to compare their dynamical flap behaviors. This is to enhance our understanding of the relationship between sequence, structure and the dynamics of this protein family. Sequence analysis shows that in BACE1 and BACE2, most of the ligand-binding sites are conserved, indicative of their enzymatic property as aspartyl protease members. The other conserved residues are more or less unsystematically localized throughout the structure. Herein, we proposed and applied different combined parameters to define the asymmetric flap motion; the distance, d₁, between the flap tip and the flexible region; the dihedral angle, φ, to account for the twisting motion and the TriCα angle, θ₂ and θ₁. All four combined parameters were found to appropriately define the observed “twisting” motion during the flaps different conformational states. Additional analysis of the parameters indicated that the flaps can exist in an ensemble of conformations, i.e. closed, semi-open and open conformations for both systems. However, the behavior of the flap tips during simulations is different between BACE1 and BACE2. The BACE1 active site cavity is more spacious as compared to that of BACE2. The analysis of 10S loop and 113S loop showed a similar trend to that of flaps, with the BACE1 loops being more flexible and less stable than those of BACE2. We believe that the results, methods and perspectives highlighted in this report would assist researchers in the discovery of BACE inhibitors as potential Alzheimer’s disease therapies.     

Bone phenotype of P2X4 receptor knockout mice: implication of a P2X7 receptor mutation?

Transgenic and knockout animal models are widely used to investigate the role of receptors, signaling pathways, and other peptides and proteins. Varying results are often published on the same model from different groups, and much effort has been put into understanding the underlying causes of these sometimes conflicting results. Recently, it has been shown that a P2X4R knockout model carries a so-called passenger mutation in the P2X7R gene, potentially affecting the interpretation of results from studies using this animal model. We therefore report this case to raise awareness about the potential pitfalls using genetically modified animal models, especially within P2 receptor research. Although purinergic signaling has been recognized as an important contributor to the regulation of bone remodeling, the process that maintains the bone quality during life, little is known about the role of the P2X4 receptor (P2X4R) in regulation of bone remodeling in health and disease. To address this, we analyzed the bone phenotype of P2rx4tm1Rass (C57BL/6J) knockout mice and corresponding wildtype using microCT and biomechanical testing. Overall, we found that the P2X4R knockout mice displayed improved bone microstructure and stronger bones in an age- and gender-dependent manner. While cortical BMD, trabecular BMD, and bone volume were higher in the 6-month-old females and 3-month-old males, this was not the case for the 3-month-old females and the 6-month-old males. Bone strength was only affected in the females. Moreover, we found that P2X4R KO mice carried the P2X7 receptor 451P wildtype allele, whereas the wildtype mice carried the 451L mutant allele. In conclusion, this study suggests that P2X4R could play a role in bone remodeling, but more importantly, it underlines the potential pitfalls when using knockout models and highlights the importance of interpreting results with great caution. Further studies are needed to verify any specific effects of P2X4R on bone metabolism.

     

Effects of growth on residual stress distribution along the radial depth of cortical cylinders from bovine femurs

Residual stress is defined as the stress that remains in bone tissue without any external forces. This study investigated the effects of growth on residual stress distributions from the surface to deeper regions of cortical cylinders obtained from less-than-one-month-old (Group Y) and two-year-old (Group M) bovine femurs. In these experiments, five diaphysis specimens from each group were used. Residual stress was measured using a high-energy synchrotron white X-ray beam to penetrate X-rays into the deeper region of the bone specimens. The measurements in the cortical cylinders from Groups Y and M were performed at 0.5- and 1-mm intervals, respectively, from the outer surface to the deeper region of the diaphysis specimens at four positions: anterior, posterior, lateral, and medial. The residual stress was calculated on the basis of variation in the interplanar spacing of hydroxyapatite crystals in the bone tissue. According to the results, the diaphysis specimens from Group Y were not subjected to large residual stresses (average −1.2 MPa and 2.4 MPa at the surface region and 1.5 mm depth, respectively). In Group M, the surface region of the diaphysis specimens was subjected to tensile residual stresses (average 6.7 MPa) and the deeper region was subjected to compressive stresses (average −8.2 MPa at 3 mm depth). There was a strong significant difference between both these regions. The value of residual stresses at the surface region of the diaphysis specimens in both the groups had a positive statistical correlation with the cortical thickness at the measured locations.     

DNA repair mechanisms in dividing and non-dividing cells

DNA damage created by endogenous or exogenous genotoxic agents can exist in multiple forms, and if allowed to persist, can promote genome instability and directly lead to various human diseases, particularly cancer, neurological abnormalities, immunodeficiency and premature aging. To avoid such deleterious outcomes, cells have evolved an array of DNA repair pathways, which carry out what is typically a multiple-step process to resolve specific DNA lesions and maintain genome integrity. To fully appreciate the biological contributions of the different DNA repair systems, one must keep in mind the cellular context within which they operate. For example, the human body is composed of non-dividing and dividing cell types, including, in the brain, neurons and glial cells. We describe herein the molecular mechanisms of the different DNA repair pathways, and review their roles in non-dividing and dividing cells, with an eye toward how these pathways may regulate the development of neurological disease.     

老年男性教师骨密度的调查

目的 为了解老年性骨质疏松情况,用超声骨密度仪对150例老年男性教师做跟骨超振幅衰减值的测试研究。方法：用DMS公怀UBIS5000型骨密度超声仪检查跟骨,研究受检者的年龄、体重、身高和巳患病咎与测得超声振幅衰减值（BUA）,声速（SOS）,骨硬度（STI）和相对骨折危险性（RRF）等参数之间的关系。结果：本仪器输出3种结果供医师参考：1.一幅灰阶图,2.一幅彩色图和曲线图,3.感兴趣区所测得的参数,受检者的平均BUA为63.87dB/MHz,SOS为1485.21m/s,本文数据经Statpal软件处理,得出回归公式：体重=189.1417 0.2062BUA-0.0224SOS,R=0.0466,P值有显著意义。结论：BUA值为主要参数,SOS为补充参数,作为评估老年男性教师的骨密度情况,假如BUA值突然下降则提示近期可能发生骨质疏松。     

Bridging the regeneration gap: stem cells, biomaterials and clinical translation in bone tissue engineering

Advances in our understanding of skeletal stem cells and their role in bone development and repair, offer the potential to open new frontiers in bone regeneration. Tissue engineering seeks to harness the regenerative capacity innate to bone for the replacement of tissue lost or damaged through a broad range of conditions associated with an increasingly aged population. The strategy entails ex vivo expansion of multipotential populations followed by delivery to the site of damage on dynamically durable-biodegradable three-dimensional structures which provide the requisite extracellular microenvironment for stem cell driven tissue development. This review will examine bone stem cell biology, and current advances in skeletal tissue engineering through the enhancement and marrying of biologically informed and clinically relevant strategies.