An inverse approach for the mechanical characterisation of vascular tissues via a generalised rule of mixtures

Mechanical factors such as stresses and strains play a major role in the growth and remodelling of soft biological tissues. The main constituents of tissue undergo different processes reacting to mechanical stimulus. Thereby, the characterisation of growth and remodelling requires an accurate estimation of the stresses and strains of their main components. Many soft tissues can be considered as composite materials and can be analysed using an appropriate rule of mixtures. Particularly, arterial tissue can be modelled as an isotropic soft matrix reinforced with preferentially oriented collagen fibres. An inverse approach to obtain the mechanical characterisation of each main component is proposed in this work. The procedure is based on a rule of mixtures raised in a finite deformation framework and generalised to include kinematics and compatibility equations for serial–parallel behaviour. This methodology allows obtaining the stress–strain relationship of the components fitting experimental data.     

生物活性材料与牙周组织再生

生物活性材料是一类经由材料表面或界面产生特殊生物或化学反应,从而影响组织和材料间的结合、诱发细胞活性或引导组织再生的生物材料。近年来,生物活性材料已广泛应用于牙周组织再生。本文对不同类型生物活性材料的特点及其在牙周组织再生中的作用进行综述,为推动其在牙周组织再生领域中的应用提供参考。     

Dentin regeneration based on tooth tissue engineering: A review

Missing or damaged teeth due to caries, genetic disorders, oral cancer, or infection may contribute to physical and mental impairment that reduces the quality of life. Despite major progress in dental tissue repair and those replacing missing teeth with prostheses, clinical treatments are not yet entirely satisfactory, as they do not regenerate tissues with natural teeth features. Therefore, much of the focus has centered on tissue engineering (TE) based on dental stem/progenitor cells to create bioengineered dental tissues. Many in vitro and in vivo studies have shown the use of cells in regenerating sections of a tooth or a whole tooth. Tooth tissue engineering (TTE), as a promising method for dental tissue regeneration, can form durable biological substitutes for soft and mineralized dental tissues. The cell-based TE approach, which directly seeds cells and bioactive components onto the biodegradable scaffolds, is currently the most potential method. Three essential components of this strategy are cells, scaffolds, and growth factors (GFs). This study investigates dentin regeneration after an injury such as caries using TE and stem/progenitor cell-based strategies. We begin by discussing about the biological structure of a dentin and dentinogenesis. The engineering of teeth requires knowledge of the processes that underlie the growth of an organ or tissue. Then, the three fundamental requirements for dentin regeneration, namely cell sources, GFs, and scaffolds are covered in the current study, which may ultimately lead to new insights in this field.     

Direct noninvasive measurement and numerical modeling of depth-dependent strains in layered agarose constructs

Biomechanical factors play an important role in the growth, regulation, and maintenance of engineered biomaterials and tissues. While physical factors (e.g. applied mechanical strain) can accelerate regeneration, and knowledge of tissue properties often guide the design of custom materials with tailored functionality, the distribution of mechanical quantities (e.g. strain) throughout native and repair tissues is largely unknown. Here, we directly quantify distributions of strain using noninvasive magnetic resonance imaging (MRI) throughout layered agarose constructs, a model system for articular cartilage regeneration. Bulk mechanical testing, giving both instantaneous and equilibrium moduli, was incapable of differentiating between the layered constructs with defined amounts of 2% and 4% agarose. In contrast, MRI revealed complex distributions of strain, with strain transfer to softer (2%) agarose regions, resulting in amplified magnitudes. Comparative studies using finite element simulations and mixture (biphasic) theory confirmed strain distributions in the layered agarose. The results indicate that strain transfer to soft regions is possible in vivo as the biomaterial and tissue changes during regeneration and maturity. It is also possible to modulate locally the strain field that is applied to construct-embedded cells (e.g. chondrocytes) using stratified agarose constructs.     

脂肪干细胞在再生医学中的应用

再生医学是一门研究如何促进创伤与组织再生及功能重建的新兴学科,主要通过研究干细胞分化、机体等正常组织创伤修复与再生等机制来维持、修复、再生或改善损伤组织和器官功能。脂肪干细胞（adipose-derived stem cells,ASCs）是近年来从脂肪组织中分离得到的一种具有多向分化潜能的干细胞,是一种足量的、可用于实际的、有一定吸引力的自体细胞代替的供体资源,并能够广泛的用于组织修复、再生、发育的可塑性及细胞治疗等研究中。阐述了脂肪干细胞在旁分泌、软组织重建及损伤修复、骨骼肌重建、心血管重建、神经系统重建及癌症转移与入侵方面的作用模式,概括总结了目前利用脂肪干细胞参与的临床治疗方法,以期对脂肪干细胞在再生医学中应用研究提供参考。     

Orthobiologics in the treatment of hip disorders

Orthobiologics are biological materials that are intended for the regeneration or healing of bone,cartilage and soft tissues.In this review we discuss the use of orthobiologics for hip disorders providing an update.The orthobiologics included in this article are hyaluronic acid,platelet rich plasma,bone marrow,adipose tissue and expanded mesenchymal stem cells.We explain the concepts and definitions of each orthobiological product,and the literature regarding its use in the hip joint.The paucity of guidelines for the production and characterization of the biological products leads to uneven results across the literature.Each biologic therapy has indications and benefits;however,noteworthy are the characterization of the orthobiologics,the application method and outcome analysis for further improvement of each technique.     

Enhancement of adipose tissue formation by implantation of adipogenic-differentiated preadipocytes

Engineered adipose tissue could be used for the reconstruction or augmentation of soft tissues lost due to mastectomy or lumpectomy in plastic and reconstructive surgery. Preadipocytes are a feasible cell source for adipose tissue regeneration. However, the enhancement of the in vivo adipogenic conversion of preadipocytes remains a major task. In vitro, the adipogenic differentiation of preadipocytes prior to implantation might enhance the adipose tissue regeneration. In the present study, we investigated whether implantation of adipogenic-differentiated preadipocytes enhances the adipose tissue formation compared with implantation of undifferentiated preadipocytes. We also investigated whether basic fibroblast growth factor (bFGF) further enhances the adipose tissue formation mediated by the implantation of adipogenic-differentiated preadipocytes. A fibrin matrix containing human preadipocytes cultured in adipogenic differentiation-inducing conditions with (group 1) or without (group 2) bFGF was injected into the subcutaneous spaces of athymic mice. Fibrin matrices containing undifferentiated human preadipocytes with (group 3) or without (group 4) bFGF were also implanted. Six weeks after implantation, the implanted cells formed new tissues in all groups. Importantly, the implantation of adipogenic-differentiated preadipocytes resulted in more extensive adipogenesis than the implantation of undifferentiated preadipocytes, as evaluated by adipose tissue area and human adipocyte-specific gene expression in the newly formed tissues. In addition, bFGF enhanced neovascularization in the newly formed tissues and further enhanced the adipogenesis mediated by the adipogenic-differentiated preadipocytes. The present study demonstrates that the implantation of adipogenic-differentiated preadipocytes enhances adipose tissue regeneration, as compared with the implantation of undifferentiated preadipocytes, and that cell transplantation-mediated adipogenesis can be further enhanced by the delivery of bFGF.     

A review of histomorphometric analysis techniques for assessing implant-soft tissue interface

Abstract

The success of dental implant treatment depends on the healing of both hard and soft tissues. While osseointegration provides initial success, the biological seal of the peri-implant soft tissue is crucial for maintaining the long term success of implants. Most studies of the biological seal of peri-implant tissues are based on animal or monolayer cell culture models. To understand the mechanisms of soft tissue attachment and the factors affecting the integrity of the soft tissue around the implants, it is essential to obtain good quality histological sections for microscopic examination. The nature of the specimens, however, which consist of both metal implant and soft peri-implant tissues, poses difficulties in preparing the specimens for histomorphometric analysis of the implant-soft tissue interface. We review various methods that have been used for the implant-tissue interface investigation with particular focus on the soft tissue. The different methods are classified and the advantages and limitations of the different techniques are highlighted.     

Recent advances in ceramic implants as drug delivery systems for biomedical applications

Research in the development of new bioceramics with local drug delivery capability for bone regeneration technologies is receiving great interest by the scientific biomedical community. Among bioceramics, silica-based ordered mesoporous materials are excellent candidates as bone implants due to two main reasons: first, the bioactive behavior of such materials in contact with simulated body fluids, ie, a carbonate hydroxyapatite similar to the mineral phase of bone is formed onto the materials surfaces. Second, their capability of acting as delivery systems of a large variety of biologically active molecules, including drugs to treat bone infection, inflammation or diseases, and molecules that promote bone tissue regeneration, such as peptides, proteins, growth factors, and other osteogenic agents. The recent chemical and technological advances in the nanometer scale has allowed the design of mesoporous silicas with tailored structural and textural properties aimed at achieving a better control over molecule loading and release kinetics. Moreover organic modification of mesoporous silica walls has been revealed as a key strategy to modulate molecule adsorption and delivery rates.     

Native-mimicking in vitro microenvironment: an elusive and seductive future for tumor modeling and tissue engineering

Human connective tissues are complex physiological microenvironments favorable for optimal survival, function, growth, proliferation, differentiation, migration, and death of tissue cells. Mimicking native tissue microenvironment using various three-dimensional (3D) tissue culture systems in vitro has been explored for decades, with great advances being achieved recently at material, design and application levels. These achievements are based on improved understandings about the functionalities of various tissue cells, the biocompatibility and biodegradability of scaffolding materials, the biologically functional factors within native tissues, and the pathophysiological conditions of native tissue microenvironments. Here we discuss these continuously evolving physical aspects of tissue microenvironment important for human disease modeling, with a focus on tumors, as well as for tissue repair and regeneration. The combined information about human tissue spaces reflects the necessities of considerations when configuring spatial microenvironments in vitro with native fidelity to culture cells and regenerate tissues that are beyond the formats of 2D and 3D cultures. It is important to associate tissue-specific cells with specific tissues and microenvironments therein for a better understanding of human biology and disease conditions and for the development of novel approaches to treat human diseases.     

嫁接接合部维管组织分化的激素调节

利用黄瓜（ ＣｕｃｕｍｉｓｓａｔｉｖｕｓＬｉｎｎ．） 试管苗离体茎段自体嫁接系统, 研究ＩＡＡ和ＺＴ对砧木和接穗维管组织分化的影响, 发现外源ＩＡＡ 和ＺＴ 是砧木和接穗间维管束桥分化的必要条件。培养基中外源激素的浓度和种类通过调控维管束桥形成时间和数目以及贯通砧木和接穗的管状分子数来调节嫁接体发育。接合部维管组织分化是生长素和细胞分裂素共同作用的结果。离体茎段自体嫁接系统是一个理想的研究植物维管组织分化的新系统。     

Preparation and characterization of poly (lactic-co-glycolic acid) nanofibers containing simvastatin coated with hyaluronic acid for using in periodontal tissue engineering

Periodontal diseases can lead to soft tissue defects. Tissue engineering can provide functional replacements for damaged tissues. Recently, electrospun nanofibers have attracted great interest for tissue engineering and drug delivery applications. This has been revealed that statins exhibit positive impacts on the proliferation and regeneration of periodontal tissues. Electrospun simvastatin loaded poly (lactic-co-glycolic acid) (SIM-PLGA-NF) were prepared using electrospinning technique. Optimal conditions for preparation of SIM-PLGA-NF (PLGA concentration of 30 wt%, voltage of 15 kV, and flow rate of 1.5 ml h⁻¹) were identified using a 2³ factorial design. The optimized SIM-PLGA-NFs (diameter of 640.2 ± 32.5 nm and simvastatin entrapment efficacy of 99.6 ± 1.5%) were surface modified with 1% w/v hyaluronic acid solution (1%HA- SIM-PLGA-NF) to improve their compatibility with fibroblasts and potential application as a periodontal tissue engineering scaffold. HA-SIM-PLGA NFs were analyzed using SEM, FTIR, and XRD. 1%HA-SIM-PLGA-NF had uniform, bead-free and interwoven morphology, which is similar to the extracellular matrix. The mechanical performance of SIM-PLGA-NFs and release profile of simvastatin from these nanofibers have been also greatly improved after coating with HA. In vitro cellular tests showed that the proliferation, adhesion, and differentiation of fibroblast cells positively enhanced on the surface of 1%HA- SIM-PLGA-NF. These results demonstrate the potential application of 1%HA-SIM-PLGA-NFs as a scaffold for periodontal tissue engineering.     

Developmental aspects of spinal cord and limb regeneration

The ability of birds and mammals to regenerate tissues is limited. By contrast, urodele amphibians can regenerate a variety of injured tissues such as intestine, cardiac muscle, lens and neural retina, as well as entire structures such as limbs, tail and lower jaw. This regenerative capacity is associated with the ability to form masses of mesenchyme cells (blastemas) that differentiate into the missing tissues or parts. Understanding the mechanisms that underlie blastema formation in urodeles will provide valuable tools with which to achieve the goal of stimulating regeneration in mammalian tissues that do not naturally regenerate. Here we discuss an example of tissue regeneration (spinal cord) and an example of epimorphic appendage regeneration (limb) in the axolotl Ambystoma mexicanum , emphasizing analysis of the processes that produce the regeneration blastema and of the tissue interactions and blastemal products that contribute to the regeneration-promoting environment.     

Development of hydrogels for regenerative engineering

The aim of regenerative engineering is to restore complex tissues and biological systems through convergence in the fields of advanced biomaterials, stem cell science, and developmental biology. Hydrogels are one of the most attractive biomaterials for regenerative engineering, since they can be engineered into tissue mimetic 3D scaffolds to support cell growth due to their similarity to native extracellular matrix. Advanced nano‐ and micro‐technologies have dramatically increased the ability to control properties and functionalities of hydrogel materials by facilitating biomimetic fabrication of more sophisticated compositions and architectures, thus extending our understanding of cell‐matrix interactions at the nanoscale. With this perspective, this review discusses the most commonly used hydrogel materials and their fabrication strategies for regenerative engineering. We highlight the physical, chemical, and functional modulation of hydrogels to design and engineer biomimetic tissues based on recent achievements in nano‐ and micro‐technologies. In addition, current hydrogel‐based regenerative engineering strategies for treating multiple tissues, such as musculoskeletal, nervous and cardiac tissue, are also covered in this review. The interaction of multiple disciplines including materials science, cell biology, and chemistry, will further play an important role in the design of functional hydrogels for the regeneration of complex tissues.     

The influence of ethylene in plant tissue culture

Ethylene produced by plant tissues grown in vitro may accumulate in large quantities in the culture vessels, particularly from rapidly growing non-differentiated callus or suspension cultures, and hence is likely to influence growth and development in such systems. Research into this aspect of tissue culture has been sparse, although it has grown recently with the increasing importance of in vitro regeneration. This review deals with the measurement and relevance of the accumulated ethylene, and the influence of both exogenous and endogenous ethylene in the different types of tissue culture systems. The relationships between ethylene and other growth regulators in tissue culture growth and development are also discussed. Although in some cases its influence seems negligible, in many types of tissue culture ethylene may act either as a promoter or inhibitor depending on the species used. Thus ethylene has an important influence on many aspects of in vitro regeneration, but it is also clear that we cannot at present describe a specific role or roles for ethylene in tissue culture which can be applied at a general, species-wide level. If its effects are to be enhanced or diminished in order to improve the efficiency and range of plant tissue culture, then more research is needed to clarify what its fundamental role might be in in vitro growth and development.Abbreviations ABA abscisic acid - ACC 1-aminocyclopropane-1-carboxylic acid - AOA aminooxyacetic acid - ASA acetylsalicyclic acid - AVG aminoethoxyvinylglycine - BA N⁶ benzylaminopurine; 2,4-D, 2,4-dichlorophenoxyacetic acid - DNP 2,4-dinitrophenol - GA gibberellin - IAA indole-3-acetic acid - IBA indole-3-butyric acid - NAA naphthaleneacetic acid - SAM S-adenosylmethionine - STS silver thiosulphate - TIBA 2,3,5-triidobenzoic acid     

Tissue engineering innovations to enhance osseointegration in immediate dental implant loading: A narrative review

The demand for efficient and accelerated osseointegration in dental implantology has led to the exploration of innovative tissue engineering strategies. Immediate implant loading reduces treatment duration and necessitates robust osseointegration to ensure long-term implant success. This review article discusses the current studies of tissue engineering innovations for enhancing osseointegration in immediate dental implant loading in the recent decade. Keywords “tissue engineering,” “osseointegration,” “immediate implant loading,” and related terms were systematically searched. The review highlights the potential of bioactive materials and growth factor delivery systems in promoting osteogenic activity and accelerating bone regeneration. The in vivo experiment demonstrates significantly improved osseointegration in the experimental group compared to traditional immediate loading techniques, as evidenced by histological analyses and biomechanical assessments. It is possible to revolutionize the treatment outcomes and patient satisfaction in dental implants by integrating bioactive materials and growth factors.     

不同山茶种质组培条件下染色体倍性的维持与变化

植物染色体的倍性维持和变化受环境因素影响,组培再生过程由于培养条件等因素往往导致染色体的结构和倍性变化。为探索组培条件下山茶种质的倍性变化,该研究利用山茶种质的愈伤组织诱导体系,通过流式细胞仪分析倍性变化情况,并结合秋水仙素处理对组培再生条件下倍性的稳定性和变化进行分析。结果表明:(1)10个山茶种质中6个为二倍体,2个为四倍体,1个为六倍体和1个为十倍体,在组培诱导愈伤及再生过程中不同倍性的种质材料能够保持稳定的倍性。(2)获得了秋水仙素处理的最适诱导条件,即培养基配方为秋水仙素浓度20 mg·L^-1,愈伤增殖培养10 d。(3)对56个独立组织样品(含愈伤和芽)开展了倍性检测发现,有38个组织样品的倍性在1.5～2.5倍之间,11个组织样品产生了低于1.5倍性的特异现象。该研究结果进一步探索了不同山茶种质之间的倍性关系,为山茶属植物的倍性调控和多倍体诱导提供了理论基础。     

Analyzing acoustoelastic effect of shear wave elastography data for perfused and hydrated soft tissues using a macromolecular network inspired model

Shear wave elastography (SWE) has enhanced our ability to non-invasively make in vivo measurements of tissue elastic properties of animal and human tissues. Recently, researchers have taken advantages of acoustoelasticity in SWE to extract nonlinear elastic properties from soft biological tissues. However, most investigations of the acoustoelastic effects of SWE data (AE-SWE) rely on classic hyperelastic models for rubber-like (dry) materials. In this paper, we focus solely on understanding acoustoelasticity in soft hydrated tissues using SWE data and propose a straightforward approach to modeling the constitutive behavior of soft tissue that has a direct microstructural/macromolecular interpretation. Our approach incorporates two constitutive features relevant to biological tissues into AE-SWE: static dilation of the medium associated with nonstructural components (e.g. tissue hydration and perfusion) and finite extensibility derived from an ideal network of biological filaments. We evaluated the proposed method using data from an in-house tissue-mimicking phantom experiment, and ex vivo and in vivo AE-SWE data available in the SWE literature. In conclusion, predictions made by our approach agreed well with measurements obtained from phantom, ex vivo and in vivo tissue experiments.     

Tooth regeneration: Implications for the use of bioengineered organs in first-wave organ replacement

Experiments with animal models have shown that the tooth crown structure can be regenerated using tissue engineering techniques that combine tooth bud cells and biodegradable materials, or by using embryonic tissue and adult stem cells. Moreover, tooth roots and periodontal tissues have been reconstructed by grafting dental stem cells, which leads to the recovery of tooth function, suggesting that tooth regeneration will become possible in humans in the near future. The present article reviews current research on tooth regeneration, discusses a model of tooth replacement that could be used clinically, and proposes a new tooth regeneration approach that overcomes the difficulties associated with the tooth replacement model. Tooth regeneration is an important stepping stone in the establishment of engineered organ transplantation, which is one of the ultimate goals of regenerative therapies.