Control of In Vitro Regeneration of Individual Reproductive and Vegetative Organs in Dracaena fragrans cv. massangeana Hort. Regularities of the Direct Regenerationof Individual Organs In Vitro

Various individual organs (tepal, flower bud, inflorescence branch, inflorescence, adult vegetative bud and juvenile vegetative bud) were directly regenerated respectively by callus in Dracaena fragrans cv. massangeana Hort. During the regeneration of these individual organs some regularity phenomena were observed. Firstly, the kind range of the individual organs, which are directly regenerated in vitro, is in close relationship to the differentiated stages of the organs used for explant excision during plant ontogeny. The explants excised from the epigeous organ that is differentiated at some stage (stage A) during plant ontogeny must be able to separately regenerate all of those individual epigeous organs: ones differentiated slightly later than the stage A, ones differentiated at the stage A and all ones differentiated earlier than the stage A. Secondly, within this range which kind of organ is regenerated depends on the exogenous auxin concentrations in medium. With the gradual increase of 2,4-D concentration from 0.005 mg/L to 0.5 mg/L, the kinds of regenerated organs will change by the order as follows: vegetative bud, inflorescence, inflorescence branch, flower bud, tepal. These regularities will be able to be used for inducing the direct regeneration of a given epigeous organ in angiosperms.

A Review on the 3D Printing of Functional Structures for Medical Phantoms and Regenerated Tissue and Organ Applications

Medical models, or ＂phantoms,＂ have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification and validation, and medical devices development. Such new applications demand high-fidelity, patient-specific, tissue-mimicking medical phantoms that can not only closely emulate the geometric structures of human organs, but also possess the properties and functions of the organ structure. With the rapid advancement of three-dimensional （3D） printing and 3D bioprinting technologies, many researchers have explored the use of these additive manufacturing techniques to fabricate functional medical phantoms for various applications. This paper reviews the applications of these 3D printing and 3D bioprinting technologies for the fabrication of functional medical phantoms and bio-structures. This review specifically discusses the state of the art along with new developments and trends in 3D printed functional medical phantoms （i.e., tissue-mimicking medical phantoms, radiologically relevant medical phantoms, and physiological medical phantoms） and 3D bio-printed structures （i.e., hybrid scaffolding materials, convertible scaffolds, and integrated sensors） for regenerated tissues and organs.

Harnessing mesenchymal aggregation for engineered organ-level regeneration:Recent progress and perspective

Stem cells,especially mesenchymal progenitors or mesenchymal stem cells(MSCs),possess an intrinsic property to form compact spheroid-like assemblies,a phenomenon known as cell aggregation.In recent years,a growing body of researches have uncovered that this is a cross-species conserved developmental event essential for initiating organogenesis in a variety of organs.Moreover,the self-assembly property also contributes to the regenerative capacities of MSC aggregates in vivo with broad range of applications in tissue engineering.In this review,the principles of self-assembled mesenchymal aggregation and its involvement in physiological organogenesis,as well as the construction approaches of engineering MSC aggregates and its application for organ regeneration are discussed.The authors aim to provide a speculative overview of the current understanding and the recent findings of cell aggregation,from both the developmental and the engineering perspectives,and thus offer insights into the understanding of stem cell biology and the establishment of novel organ regeneration strategies.

Using zebrafish as the model organism to understand organ regeneration

The limited regenerative capacity of several organs, such as central nervous system(CNS), heart and limb in mammals makes related major diseases quite difficult to recover. Therefore, dissection of the cellular and molecular mechanisms underlying organ regeneration is of great scientific and clinical interests. Tremendous progression has already been made after extensive investigations using several model organisms for decades. Unfortunately, distance to the final achievement of the goal still remains. Recently, zebrafish became a popular model organism for the deep understanding of regeneration based on its powerful regenerative capacity, in particular the organs that are limitedly regenerated in mammals. Additionally, zebrafish are endowed with other advantages good for the study of organ regeneration. This review summarizes the recent progress in the study of zebrafish organ regeneration, in particular regeneration of fin, heart, CNS, and liver as the representatives. We also discuss reasons of the reduced regenerative capacity in higher vertebrate, the roles of inflammation during regeneration, and the difference between organogenesis and regeneration.

Recruited CD68^(+)CD206^(+)macrophages orchestrate graft immune tolerance to prompt xenogeneic-dentin matrix-based tooth root regeneration

Successful regenerative medicine strategies of xenogeneic extracellular matrix need a synergistic balance among inflammation,fibrosis,and remodeling process.Adaptive macrophage subsets have been identified to modulate inflammation and orchestrate the repair of neighboring parenchymal tissues.This study fabricated PPARγ-primed CD68+CD206+M2 phenotype(M2γ),and firstly verified their anti-inflammatory and tissue-regenerating roles in xenogeneic bioengineered organ regeneration.Our results showed that Th1-type CD3^(+)CD8^(+)T cell response to xenogeneic-dentin matrix-based bioengineered root complex(xeno-complex)was significantly inhibited by M2γmacrophage in vitro.PPARγactivation also timely recruited CD68^(+)CD206^(+)tissue macrophage polarization to xeno-complex in vivo.These subsets alleviated proinflammatory cytokines(TNF-α,IFN-γ)at the inflammation site and decreased CD3^(+)CD8^(+)T lymphocytes in the periphery system.When translated to an orthotopic nonhuman primate model,PPARγ-primed M2 macrophages immunosuppressed IL-1β,IL-6,TNF-α,MMPs to enable xeno-complex to effectively escape immune-mediated rejection and initiate graft-host synergistic integrity.These collective activities promoted the differentiation of odontoblast-like and periodontal-like cells to guide pulp-dentin and cementum-PDLs-bone regeneration and rescued partially injured odontogenesis such as DSPP and periostin expression.Finally,the regenerated root showed structure-biomechanical and functional equivalency to the native tooth.The timely conversion of M1-to-M2 macrophage mainly orchestrated odontogenesis,fibrogenesis,and osteogenesis,which represents a potential modulator for intact parenchymal-stromal tissue regeneration of targeted organs.

Emerging delivery systems based on aqueous two-phase systems:A review

The aqueous two-phase system(ATPS)is an all-aqueous system fabricated from two immiscible aqueous phases.It is spontaneously assembled through physical liquid-liquid phase separation(LLPS)and can create suitable templates like the multicompartment of the intracellular environment.Delicate structures containing multiple compartments make it possible to endow materials with advanced functions.Due to the properties of ATPSs,ATPS-based drug delivery systems exhibit excellent biocompatibility,extraordinary loading efficiency,and intelligently controlled content release,which are particularly advantageous for delivering drugs in vivo.Therefore,we will systematically review and evaluate ATPSs as an ideal drug delivery system.Based on the basic mechanisms and influencing factors in forming ATPSs,the transformation of ATPSs into valuable biomaterials is described.Afterward,we concentrate on the most recent cutting-edge research on ATPS-based delivery systems.Finally,the potential for further collaborations between ATPS-based drug-carrying biomaterials and disease diagnosis and treatment is also explored.

An Overview on Materials and Techniques in 3D Bioprinting Toward Biomedical Application

Three-dimensional(3D)bioprinting,an additive manufacturing based technique of biomaterials fabrication,is an innovative and auspicious strategy in medical and pharmaceutical fields.The ability of producing regenerative tissues and organs has made this technology a pioneer to the creation of artificial multi-cellular tissues/organs.A broad variety of biomaterials is currently being utilized in 3D bioprinting as well as multiple techniques employed by researchers.In this review,we demonstrate the most common and novel biomaterials in 3D bioprinting technology further with introducing the related techniques that are commonly taking into account by researchers.In addition,an attempt has been accomplished to hand over the most relevant application of 3D bioprinting techniques such as tissue regeneration,cancer investigations,etc.by presenting the most important works.The main aim of this review paper is to emphasis on strengths and limitations of existence biomaterials and 3D bioprinting techniques in order to carry out a comparison through them.

Pattern analysis of stem cell differentiation during in vitro Arabidopsis organogenesis

Plant somatic cells have the capability to switch their cell fates from differentiated to undifferen-tiated status under proper culture conditions,which is designated as totipotency.As a result,plant cells can easily regenerate new tissues or organs from a wide variety of explants.However,the mechanism by which plant cells have such remarkable regeneration ability is still largely unknown.In this study,we used a set of meristem-specific marker genes to analyze the patterns of stem cell differentiation in the processes of somatic embryogenesis as well as shoot or root organogenesis in vitro.Our studies furnish preliminary and important information on the patterns of the de novo stem cell differentiation during various types of in vitro organogenesis.