Bone tissue engineering bioreactors: a role in the clinic?

Tissue engineered bone grafts have the potential to be used to treat large bone defects due to congenital abnormalities, cancer resections, or traumatic incidents. Recent studies have shown that perfusion bioreactors can be used to generate grafts of clinically relevant sizes and shapes. Despite these scientific and technological successes, there is uncertainty regarding the translational utility of bioreactor-based approaches due to the perceived high costs associated with these procedures. In fact, experiences over the past two decades have demonstrated that the widespread application of cell-based therapies is heavily dependent on the commercial viability. In this article, we directly address the question of whether bioreactors used to create bone grafts have the potential to be implemented in clinical approaches to bone repair and regeneration. We provide a brief review of tissue engineering approaches to bone repair, clinical trials that have employed cell-based methods, and advances in bioreactor technologies over the past two decades. These analyses are combined to provide a perspective on what is missing from the scientific literature that would enable an objective baseline for weighing the benefit of extended in vitro cultivation of cells into functional bone grafts against the cost of additional cultivation. In our estimation, the cost of bioreactor-based bone grafts may range from $10,000 to $15,000, placing it within the range of other widely used cell-based therapies. Therefore, in situations where a clear advantage can be established for engineered grafts comprising patient-specific, autologous cells, engineered bone grafts may be a clinically feasible option.     

Multi-cellularity in cardiac tissue engineering,how close are we to native heart tissue?

Journal of Muscle Research and Cell Motility - Tissue engineering is a complex field where the elements of biology and engineering are combined in an attempt to recapitulate the native environment...     

The origins of western obesity: a role for animal protein?

A reduced propensity to oxidize fat, as indicated by a relatively high fasting respiratory quotient, is a major risk factor for weight gain. Increased insulin secretion works in various ways to impede fat oxidation and promote fat storage. The substantial 'spontaneous' weight loss often seen with very-low-fat dietary regimens may reflect not only a reduced rate of fat ingestion, but also an improved insulin sensitivity of skeletal muscle that down-regulates insulin secretion. Reduction of diurnal insulin secretion may also play a role in the fat loss often achieved with exercise training, low-glycemic-index diets, supplementation with soluble fiber or chromium, low-carbohydrate regimens, and biguanide therapy. The exceptional leanness of vegan cultures may reflect an additional factor - the absence of animal protein. Although dietary protein by itself provokes relatively little insulin release, it can markedly potentiate the insulin response to co-ingested carbohydrate; Western meals typically unite starchy foods with an animal protein-based main course. Thus, postprandial insulin secretion may be reduced by either avoiding animal protein, or segregating it in low-carbohydrate meals; the latter practice is a feature of fad diets stressing 'food combining'. Vegan diets tend to be relatively low in protein, legume protein may be slowly absorbed, and, as compared to animal protein, isolated soy protein provokes a greater release of glucagon, an enhancer of fat oxidation. The low insulin response to rice may mirror its low protein content. Minimizing diurnal insulin secretion in the context of a low fat intake may represent an effective strategy for achieving and maintaining leanness.     

The role of T-cell receptor α and β genes in MHC-restricted antigen recognition

T cells use α- and β-chain genes, which are organized and diversified by somatic DNA rearrangements much like the immunoglobulin genes, to encode clonally distributed receptor molecules which confer specificity for MHC and antigen. Here Zlatko Dembic and his colleagues summarize recent mutagenesis and gene transfection experiments indicating that α- and β-chain genes are necessary and sufficient for T-cell specificity.     

Biodegradation and in vivo biocompatibility of a degradable, polar/hydrophobic/ionic polyurethane for tissue engineering applications

A degradable, polar/hydrophobic/ionic polyurethane (D-PHI) scaffold was optimized in in vitro studies to yield mechanical properties appropriate to replicate vascular graft tissue while eliciting a more wound-healing phenotype macrophage when compared to established materials. The objectives of this study were to characterize the biodegradation (in vitro and in vivo) and assess the in vivo biocompatibility of D-PHI, comparing it to a well-established, commercially-available scaffold biomaterial, polylactic glycolic acid (PLGA), recognized as being degradable, non-cytotoxic, and showing good biocompatibility. PLGA and D-PHI were formed into 6 mm diameter disk-shaped scaffolds (2 mm thick) of similar porosity (～82%) and implanted subcutaneously in rats. Both PLGA and D-PHI scaffolds were well-tolerated at the 7 d time point in vivo. In vitro D-PHI scaffolds degraded slowly (only 12 wt% in PBS in vitro after 120 d at 37 °C). In vivo, D-PHI scaffolds degraded at a more controlled rate (7 wt% loss over the acute 7 d implant phase and subsequently a linear profile of degradation leading to a 21 wt% mass loss by 100 d (chronic period)) than PLGA scaffolds which showed an initial more rapid degradation (14 wt% over 7 d), followed by minimal change between 7 and 30 d, and then a very rapid breakdown of the scaffold over the next 60 d. Histological examination of D-PHI scaffolds showed tissue ingrowth into the pores increased with time whereas PLGA scaffolds excluded cells/tissue from its porous structure as it degraded. The results of this study suggest that D-PHI has promising qualities for use as an elastomeric scaffold material for soft TE applications yielding well integrated tissue within the scaffold and a controlled rate of degradation stabilizing the form and shape of the implant.     

Research progress of gene therapy for vascularization of tissue engineering北大核心

BACKGROUND: The rapid formation of functional vascular system in large-scale engineered graft is the basic prerequisite for its successful survival in the host. The vascularization of tissue engineering by genetic engineering technology has the advantages of good therapeutic effect, low cost and high safety. It is of great significance to carry out the research on gene therapy for vascularization of tissue engineering for long-term effective tissue repair. OBJECTIVE: To summarize the current research status and main problems of seed cells, target genes and gene vectors of gene therapy in tissue engineering vascularization so as to further explore the application prospect of gene therapy in tissue engineering vascularization,. METHODS: The literature retrieval was conducted on PubMed, Web of Science, and CNKI with the key words of “tissue engineering; vascularization; gene therapy; seed cells; target genes; vectors” in Chinese and English, and 61 articles closely related to this study were selected for the review. RESULTS AND CONCLUSION: Mesenchymal stem cells, vascular endothelial cells and endothelial progenitor cells are the most potential seed cells for vascularization of tissue engineering using gene therapy. They not only have good vascular induction, but also benefit the introduction of many virus and non-viral vectors and the expression of vascularization target genes. Vascular endothelial growth factor, angiopoietin-1, basic fibroblast growth factor, bone morphogenetic protein-2, hypoxia inducible factor-1 α and other vascularization target genes are mainly used to construct efficient and stable vascular network in engineering grafts by means of combination of double/multiple gene, coupling of osteogenesis and angiogenesis, and regulation of upstream gene. Since different viral and non-viral vectors have their own advantages and disadvantages, suitable vectors should be selected according to the efficiency of gene transfection, biological safety, and cost in application. At present, although great progress has been made in the application of gene therapy in tissue engineering vascularization, there are still many key technologies to be broken through for clinical application, such as how to improve the targeted release of target growth factors and reduce the safety risk, which is also the research direction and hot spot of tissue engineering vascularization based on gene therapy in the future. © 2022, Publishing House of Chinese Journal of Tissue Engineering Research. All rights reserved.     

The role of AlkB protein in repair of 1,N⁶-ethenoadenine in Escherichia coli cells

Etheno (ε) DNA adducts, including 1,N(6)-ethenoadenine (εA), are formed by various bifunctional agents of exogenous and endogenous origin. The AT→TA transversion, the most frequent mutation provoked by the presence of εA in DNA, is very common in critical codons of the TP53 and RAS genes in tumours induced by exposure to carcinogenic vinyl compounds. Here, using a method that allows examination of the mutagenic potency of a metabolite of vinyl chloride, chloroacetaldehyde (CAA), but eliminates its cytotoxicity, we studied the participation of alkA, alkB and mug gene products in the repair of εA in Escherichia coli cells. The test system used comprised the pIF105 plasmid bearing the lactose operon of CC105 origin, which allowed monitoring of Lac(+) revertants that arose by AT→TA substitutions due to the modification of adenine by CAA. The plasmid was CAA-modified in vitro and replicated in E.coli of various genetic backgrounds (wt, alkA, alkB, mug, alkAalkB, alkAmug and alkBmug). To modify the levels of the AlkA and AlkB proteins, mutagenesis was studied in E.coli cells induced or not in adaptive response to alkylating agents. Considering the levels of CAA-induced Lac(+) revertants in strains harbouring the CAA-modified pIF105 plasmid and induced or not in adaptive response, we conclude that the AlkB dioxygenase plays a major role in decreasing the level of AT→TA mutations, thus in the repair of εA in E.coli cells. The observed differences of mutation frequencies in the various mutant strains assayed indicate that Mug glycosylase is also engaged in the repair of εA, whereas the role the AlkA glycosylase in this repair is negligible.     

A role for epithelial γδ T cells in tissue repair

My colleagues and I have a long-term interest in interactions between intraepithelial γδ T cells and neighboring epithelial cells. We have focused our studies on interactions in the thymus, skin, and intestine, and are investigating the development, specificity, and function of these γδ T cells. Our results have defined unique properties of these cells and support a specialized role for epithelial γδ T cells in immune surveillance, wound repair, inflammation, and protection from malignancy.     

The 65kDa antigen of mycobacteria—a common bacterial protein?

The 65 kilodalton antigen of Mycobacterium tuberculosis and M. leprae is a well-characterized, strongly immunogenic protein eliciting antibody and T-cell responses in infected patients. Recent studies have disclosed regions of cross-reactivity between the 65kDa antigen and proteins in many other bacterial species. These include the product of the ams gene in E. coli which is involved in the processing of RNA. Here Douglas Young and his colleagues discuss these observations, the significance of the 65kDa antigen and its possible role in the pathogenesis of mycobacterial and other diseases.     

Fabrication and characterization of chitosan–collagen crosslinked membranes for corneal tissue engineering

This article describes a chitosan–collagen composite membrane as corneal tissue-engineering biomaterials. The membrane was prepared by dissolving the chitosan into collagen with the weight ratio of 0, 15, 30, 45, 60, and 100%, followed by crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. Mechanical properties, contact angles, and optical transmittance were determined and compared between chitosan membrane and crosslinking composite membrane. As a result, the optical transparency and mechanical strength of the chitosan–collagen membranes were significantly better than that of the sample of chitosan. In addition, in vitro cell culture studies revealed that the collagen has no negative effect on the cell morphology, viability, and proliferation and possess good biocompatibility. Overall, the dendrimer crosslinked chitosan–collagen composite membranes showed promising properties that suggest that these might be suitable biomaterials for corneal tissue-engineering applications.     

Electrospinning of gelatin for tissue engineering – molecular conformation as one of the overlooked problems

Gelatin is one of the most promising materials in tissue engineering as a scaffold component. This biopolymer indicates biocompatibility and bioactivity caused by the existence of specific amino acid sequences, being preferred sites for interactions with cells, with high similarity to natural extracellular matrix. The present paper does not aspire to be a full review of electrospinning of gelatin and gelatin containing nanofibers as scaffolds in tissue engineering. It is focused on the still open question of the role of the higher order structures of gelatin in scaffold’s bioactivity/functionality. Gelatin molecules can adopt various conformations depending on temperature, solvent, pH, etc. Our review indicates the potential ways for formation of α-helix conformation during electrospinning and the methods of further structure stabilization. It is intuitively expected that the native α-helix conformation appearing as a result of partial renaturation of gelatin can be beneficial from the viewpoint of bioactivity of scaffolds, providing thus a much cheaper alternative approach as opposed to expensive electrospinning of native collagen.     

Parents – child role reversal in trilogue play: Case studies of trajectories from pregnancy to toddlerhood

Abstract

Role reversal, whereby a child attempts to meet her parent's adult needs for parenting, intimacy, or companionship, has been identified as a risk factor for developmental disturbances. It has been defined from diverse perspectives as a child attachment strategy, a parent – toddler relational disturbance, and a boundary disturbance between parents and child. The recently discovered infant's triangular capacity, namely the sharing of her attention and affects with both parents, allows one to analyse the infant's contribution to early family dynamics. Role reversal was detected in 4 out of 45 father – mother – infant interactions observed in trilogue play from pregnancy to toddlerhood. The developmental trajectories towards role reversal are explored by means of case analyses. Results are compared with cases of problematic triangulation encountered in the same sample. In role reversal, family interactions are rigidly organized around a “two against one” coalition, whereby the normative hierarchy between parents and child is reversed. The child's triangular capacity is overactivated, controlling the tension between her parents by provocation – animation strategies.     

Characterization of the RstB2 protein,the DNA-binding protein of CTXϕ phage from Vibrio cholerae

The low abundant protein RstB2, encoded in the RS2 region of CTX?, is essential for prophage formation. However, the only biochemical activity so far described is the single/double-stranded DNA-binding capacity of that protein. In this paper, a recombinant RstB2 (rRstB2) protein was overexpressed in E. coli with a yield of 58.4 mg l^?1 in shaken cultures, LB broth. The protein, purified to homogeneity, showed an identity with rRstB2 by peptide mass fingerprinting. The apparent molecular weight of the RstB2 native protein suggests that occurs mostly as a monomer in solution. The monomers were able of reacting immediately upon exposure to DNA molecules. After a year of storage at ?20 °C, the protein remains biologically active. Bioinformatics analysis of the amino acid sequence of RstB2 predicts the C-end of this protein to be disordered and highly flexible, like in many other single-stranded DNA-binding proteins. When compared with the gVp of M13, conserved amino acids are found at structurally or functionally important relative positions. These results pave the way for additional studies of structure and molecular function of RstB2 for the biology of CTX?.     

The role of activating reagents on adsorption properties of Anti-hepatitis B surface antigen monoclonal antibody immunoadsorbents

HBs Ag wasfound by Blumberg,Alterand Visuich in 1 96 5and was confirmed tohave close relationship to acute Hepatitis B,which damaged human s health serious-ly without any effective medicines and treatments.　　 Immunoadsorbents were a kind of specific ads…     

Injectable in situ forming biodegradable chitosan–hyaluronic acid based hydrogels for cartilage tissue engineering

Injectable, biodegradable scaffolds are important biomaterials for tissue engineering and drug delivery. Hydrogels derived from natural polysaccharides are ideal scaffolds as they resemble the extracellular matrices of tissues comprised of various glycosaminoglycans (GAGs). Here, we report a new class of biocompatible and biodegradable composite hydrogels derived from water-soluble chitosan and oxidized hyaluronic acid upon mixing, without the addition of a chemical crosslinking agent. The gelation is attributed to the Schiff base reaction between amino and aldehyde groups of polysaccharide derivatives. In the current work, N-succinyl-chitosan (S-CS) and aldehyde hyaluronic acid (A-HA) were synthesized for preparation of the composite hydrogels. The polysaccharide derivatives and composite hydrogels were characterized by FTIR spectroscopy. The effect of the ratio of S-CS and A-HA on the gelation time, microstructure, surface morphology, equilibrium swelling, compressive modulus, and in vitro degradation of composite hydrogels was examined. The potential of the composite hydrogel as an injectable scaffold was demonstrated by the encapsulation of bovine articular chondrocytes within the composite hydrogel matrix in vitro. The results demonstrated that the composite hydrogel supported cell survival and the cells retained chondrocytic morphology. These characteristics provide a potential opportunity to use the injectable, composite hydrogels in tissue engineering applications.