Nanotechnology in the Regeneration of Complex Tissues

Polyvinyl Alcohol Nanofibers Blends as Drug Delivery System in Tissue Regeneration

Nanofibers have shown promising clinical results in the process of tissue regeneration since they provide a similar structure to the extracellular matrix of different tissues, high surface-to-volume ratio and porosity, flexibility, and gas permeation, offering topographical features that stimulate cell adhesion and proliferation. Electrospinning is one of the most used techniques for manufacturing nanomaterials due to its simplicity and low cost. In this review, we highlight the use of nanofibers produced with polyvinyl alcohol and polymeric associations (PVA/blends) as a matrix for release capable of modifying the pharmacokinetic profile of different active ingredients in the regeneration of connective, epithelial, muscular, and nervous tissues. Articles were selected by three independent reviewers by analyzing the databases, such as Web of Science, PubMed, Science Direct, and Google Scholar (last 10 years). Descriptors used were "nanofibers", "poly (vinyl alcohol)", "muscle tissue", "connective tissue", "epithelial tissue", and "neural tissue engineering". The guiding question was: How do different compositions of polyvinyl alcohol polymeric nanofibers modify the pharmacokinetics of active ingredients in different tissue regeneration processes? The results demonstrated the versatility of the production of PVA nanofibers by solution blow technique with different actives (lipo/hydrophilic) and with pore sizes varying between 60 and 450 nm depending on the polymers used in the mixture, which influences the drug release that can be controlled for hours or days. The tissue regeneration showed better cellular organization and greater cell proliferation compared to the treatment with the control group, regardless of the tissue analyzed. We highlight that, among all blends, the combinations PVA/PCL and PVA/CS showed good compatibility and slow degradation, indicating their use in prolonged times of biodegradation, thus benefiting tissue regeneration in bone and cartilage connective tissues, acting as a physical barrier that results in guided regeneration, and preventing the invasion of cells from other tissues with increased proliferation rate.

Nano-material utilization in stem cells for regenerative medicine

The utilization of nanotechnology in regenerative medicine has been globally proven to be the main solution to many issues faced with tissue engineering today, and the theoretical and empirical investigations of the association of nanomaterials with stem cells have made significant progress as well. For their ability to self-renew and differentiate into a variety of cell types, stem cells have become popular candidates for cell treatment in recent years, particularly in cartilage and Ocular regeneration. However, there are still several challenges to overcome before it may be used in a wide range of therapeutic contexts. This review paper provides a review of the various implications of nanomaterials in tissue and cell regeneration, the stem cell and scaffold application in novel treatments, and the basic developments in stem cell-based therapies, as well as the hurdles that must be solved for nanotechnology to be used in its full potential. Due to the increased interest in the continuously developing field of nanotechnology, demonstrating, and pinpointing the most recognized and used applications of nanotechnology in regenerative medicine became imperative to provide students, researchers, etc. who are interested.

Extrinsically Conductive Nanomaterials for Cardiac Tissue Engineering Applications

Myocardial infarction (MI) is the consequence of coronary artery thrombosis resulting in ischemia and necrosis of the myocardium. As a result, billions of contractile cardiomyocytes are lost with poor innate regeneration capability. This degenerated tissue is replaced by collagen-rich fibrotic scar tissue as the usual body response to quickly repair the injury. The non-conductive nature of this tissue results in arrhythmias and asynchronous beating leading to total heart failure in the long run due to ventricular remodelling. Traditional pharmacological and assistive device approaches have failed to meet the utmost need for tissue regeneration to repair MI injuries. Engineered heart tissues (EHTs) seem promising alternatives, but their non-conductive nature could not resolve problems such as arrhythmias and asynchronous beating for long term in-vivo applications. The ability of nanotechnology to mimic the nano-bioarchitecture of the extracellular matrix and the potential of cardiac tissue engineering to engineer heart-like tissues makes it a unique combination to develop conductive constructs. Biomaterials blended with conductive nanomaterials could yield conductive constructs (referred to as extrinsically conductive). These cell-laden conductive constructs can alleviate cardiac functions when implanted in-vivo. A succinct review of the most promising applications of nanomaterials in cardiac tissue engineering to repair MI injuries is presented with a focus on extrinsically conductive nanomaterials.

Nanoengineering in Cardiac Regeneration: Looking Back and Going Forward

To deliver on the promise of cardiac regeneration, an integration process between an emerging field, nanomedicine, and a more consolidated one, tissue engineering, has begun. Our work aims at summarizing some of the most relevant prevailing cases of nanotechnological approaches applied to tissue engineering with a specific interest in cardiac regenerative medicine, as well as delineating some of the most compelling forthcoming orientations. Specifically, this review starts with a brief statement on the relevant clinical need, and then debates how nanotechnology can be combined with tissue engineering in the scope of mimicking a complex tissue like the myocardium and its natural extracellular matrix (ECM). The interaction of relevant stem, precursor, and differentiated cardiac cells with nanoengineered scaffolds is thoroughly presented. Another correspondingly relevant area of experimental study enclosing both nanotechnology and cardiac regeneration, e.g., nanoparticle applications in cardiac tissue engineering, is also discussed.

A review of using green chemistry methods for biomaterials in tissue engineering

Although environmentally safe, or green, technologies have revolutionized other fields (such as consumables, automobiles, etc.), its use in biomaterials is still at its infancy. However, in the few cases in which safe manufacturing technology and materials have been implemented to prevent postpollution and reduce the consumption of synthesized scaffold (such as bone, cartilage, blood cell, nerve, skin, and muscle) has had a significant impact on different applications of tissue engineering. In the present research, we report the use of biological materials as templates for preparing different kinds of tissues and the application of safe green methods in tissue engineering technology. These include green methods for bone and tissue engineering-based biomaterials, which have received the greatest amount of citations in recent years. Thoughts on what is needed for this field to grow are also critically included. In this paper, the impending applications of safe, ecofriendly materials and green methods in tissue engineering have been detailed.

Immunohistochemical evaluation after Sr-enriched biphasic ceramic implantation in rabbits femoral neck: comparison of seven different bone conditions

Strontium (Sr) has shown effectiveness for stimulating bone remodeling. Nevertheless, the exact therapeutic values are not established yet. Authors hypothesized that local application of Sr-enriched ceramics would enhance bone remodeling in constant osteoporosis of rabbits' femoral neck bone. Seven different bone conditions were analyzed: ten healthy rabbits composed a control group, while other twenty underwent ovariectomy and were divided into three groups. Bone defect was filled with hydroxyapatite 30% (HAP) and tricalcium phosphate 70% (TCP) granules in 7 rabbits, 5% of Sr-enriched HAP/TCP granules in 7, but sham defect was left unfilled in 6 rabbits. Bone samples were obtained from operated and non-operated legs 12 weeks after surgery and analyzed by histomorphometry and immunohistochemistry (IMH). Mean trabecular bone area in control group was 0.393 mm2, in HAP/TCP - 0.226 mm2, in HAP/TCP/Sr - 0.234 mm2 and after sham surgery - 0.242 mm2. IMH revealed that HAP/TCP/Sr induced most noticeable increase of nuclear factor kappa beta 105 (NFkB 105), osteoprotegerin (OPG), osteocalcin (OC), bone morphogenetic protein 2/4 (BMP 2/4), collagen type 1α (COL-1α), interleukin 1 (IL-1) with comparison to intact leg; NFkB 105 and OPG rather than pure HAP/TCP or sham bone. We concluded that Sr-enriched biomaterials induce higher potential to improve bone regeneration than pure bioceramics in constant osteoporosis of femoral neck bone. Further studies on bigger osteoporotic animals using Sr-substituted orthopedic implants for femoral neck fixation should be performed to confirm valuable role in local treatment of osteoporotic femoral neck fractures in humans.

From Chemotherapy to Combined Targeted Therapeutics: In Vitro and in Vivo Models to Decipher Intra-tumor Heterogeneity

Recent advances in next-generation sequencing and other omics technologies capable to map cell fate provide increasing evidence on the crucial role of intra-tumor heterogeneity (ITH) for cancer progression. The different facets of ITH, from genomic to microenvironmental heterogeneity and the hierarchical cellular architecture originating from the cancer stem cell compartment, contribute to the range of tumor phenotypes. Decoding these complex data resulting from the analysis of tumor tissue complexity poses a challenge for developing novel therapeutic strategies that can counteract tumor evolution and cellular plasticity. To achieve this aim, the development of in vitro and in vivo cancer models that resemble the complexity of ITH is crucial in understanding the interplay of cells and their (micro)environment and, consequently, in testing the efficacy of new targeted treatments and novel strategies of tailoring combinations of treatments to the individual composition of the tumor. This challenging approach may be an important cornerstone in overcoming the development of pharmaco-resistances during multiple lines of treatment. In this paper, we report the latest advances in patient-derived 3D (PD3D) cell cultures and patient-derived tumor xenografts (PDX) as in vitro and in vivo models that can retain the genetic and phenotypic heterogeneity of the tumor tissue.

Profiling lung adenocarcinoma by liquid biopsy: can one size fit all?

Background

Cancer is first and foremost a disease of the genome. Specific genetic signatures within a tumour are prognostic of disease outcome, reflect subclonal architecture and intratumour heterogeneity, inform treatment choices and predict the emergence of resistance to targeted therapies. Minimally invasive liquid biopsies can give temporal resolution to a tumour’s genetic profile and allow the monitoring of treatment response through levels of circulating tumour DNA (ctDNA). However, the detection of ctDNA in repeated liquid biopsies is currently limited by economic and time constraints associated with targeted sequencing.

Methods

Here we bioinformatically profile the mutational and copy number spectrum of The Cancer Genome Network’s lung adenocarcinoma dataset to uncover recurrently mutated genomic loci.

Results

We build a panel of 400 hotspot mutations and show that the coverage extends to more than 80% of the dataset at a median depth of 8 mutations per patient. Additionally, we uncover several novel single-nucleotide variants present in more than 5% of patients, often in genes not commonly associated with lung adenocarcinoma.

Conclusion

With further optimisation, this hotspot panel could allow molecular diagnostics laboratories to build curated primer banks for ‘off-the-shelf’ monitoring of ctDNA by droplet-based digital PCR or similar techniques, in a time- and cost-effective manner.

Patient-derived tumour xenografts for breast cancer drug discovery

Despite remarkable advances in our understanding of the drivers of human malignancies, new targeted therapies often fail to show sufficient efficacy in clinical trials. Indeed, the cost of bringing a new agent to market has risen substantially in the last several decades, in part fuelled by extensive reliance on preclinical models that fail to accurately reflect tumour heterogeneity. To halt unsustainable rates of attrition in the drug discovery process, we must develop a new generation of preclinical models capable of reflecting the heterogeneity of varying degrees of complexity found in human cancers. Patient-derived tumour xenograft (PDTX) models prevail as arguably the most powerful in this regard because they capture cancer's heterogeneous nature. Herein, we review current breast cancer models and their use in the drug discovery process, before discussing best practices for developing a highly annotated cohort of PDTX models. We describe the importance of extensive multidimensional molecular and functional characterisation of models and combination drug-drug screens to identify complex biomarkers of drug resistance and response. We reflect on our own experiences and propose the use of a cost-effective intermediate pharmacogenomic platform (the PDTX-PDTC platform) for breast cancer drug and biomarker discovery. We discuss the limitations and unanswered questions of PDTX models; yet, still strongly envision that their use in basic and translational research will dramatically change our understanding of breast cancer biology and how to more effectively treat it.

Three-Dimensional Graphene: A Biocompatible and Biodegradable Scaffold with Enhanced Oxygenation

Owing to its high porosity, specific surface area and three-dimensional structure, three-dimensional graphene (3D-C) is a promising scaffold material for tissue engineering, regenerative medicine as well as providing a more biologically relevant platform for living organisms in vivo studies. Recently, its differentiation effects on cells growth and anti-inflammation properties have also been demonstrated. Here, we report a complete study of 3D-C as a fully adequate scaffold for tissue engineering and systematically analyze its biocompatibility and biodegradation mechanism. The metabolic activities of liver cells (HepG2 hepatocarcinoma cells) on 3D-C are studied and our findings show that cell growth on 3D-C has high cell viability (> 90%), low lactate production (reduced by 300%) and its porous structure also provides an excellent oxygenation platform. 3D-C is also biodegradable via a 2-step oxidative biodegradation process by first, disruption of domains and lift off of smaller graphitic particles from the surface of the 3D-C and subsequently, the decomposition of these graphitic flakes. In addition, the speed of the biodegradation can be tuned with pretreatment of O2 plasma.

BMP2/BMPR1A is linked to tumour progression in dedifferentiated liposarcomas

Bone Morphogenic Protein 2 (BMP2) is a multipurpose cytokine, important in the development of bone and cartilage, and with a role in tumour initiation and progression. BMP2 signal transduction is dependent on two distinct classes of serine/threonine kinase known as the type I and type II receptors. Although the type I receptors (BMPR1A and BMPR1B) are largely thought to have overlapping functions, we find tissue and cellular compartment specific patterns of expression, suggesting potential for distinct BMP2 signalling outcomes dependent on tissue type. Herein, we utilise large publicly available datasets from The Cancer Genome Atlas (TCGA) and Protein Atlas to define a novel role for BMP2 in the progression of dedifferentiated liposarcomas. Using disease free survival as our primary endpoint, we find that BMP2 confers poor prognosis only within the context of high BMPR1A expression. Through further annotation of the TCGA sarcoma dataset, we localise this effect to dedifferentiated liposarcomas but find overall BMP2/BMP receptor expression is equal across subsets. Finally, through gene set enrichment analysis we link the BMP2/BMPR1A axis to increased transcriptional activity of the matrisome and general extracellular matrix remodelling. Our study highlights the importance of continued research into the tumorigenic properties of BMP2 and the potential disadvantages of recombinant human BMP2 (rhBMP2) use in orthopaedic surgery. For the first time, we identify high BMP2 expression within the context of high BMPR1A expression as a biomarker of disease relapse in dedifferentiated liposarcomas.

Maintaining Tumor Heterogeneity in Patient-Derived Tumor Xenografts

Preclinical models often fail to capture the diverse heterogeneity of human malignancies and as such lack clinical predictive power. Patient-derived tumor xenografts (PDX) have emerged as a powerful technology: capable of retaining the molecular heterogeneity of their originating sample. However, heterogeneity within a tumor is governed by both cell-autonomous (e.g., genetic and epigenetic heterogeneity) and non-cell-autonomous (e.g., stromal heterogeneity) drivers. Although PDXs can largely recapitulate the polygenomic architecture of human tumors, they do not fully account for heterogeneity in the tumor microenvironment. Hence, these models have substantial utility in basic and translational research in cancer biology; however, study of stromal or immune drivers of malignant progression may be limited. Similarly, PDX models offer the ability to conduct patient-specific in vivo and ex vivo drug screens, but stromal contributions to treatment responses may be under-represented. This review discusses the sources and consequences of intratumor heterogeneity and how these are recapitulated in the PDX model. Limitations of the current generation of PDXs are discussed and strategies to improve several aspects of the model with respect to preserving heterogeneity are proposed.

Multi stimuli-responsive hydrogel microfibers containing magnetite nanoparticles prepared using microcapillary devices

Extensive research efforts have been devoted to the development of hydrogel microfibers for tissue engineering, because the vascular structure is related to the transport of nutrients and oxygen as well as the control of metabolic and mechanical functions in the human body. Even though stimuli-responsive properties would enhance the potential applicability of hydrogel microfibers for artificial tissue architectures, previous studies of their fabrication have not considered changes in the microfibers in response to external stimuli. In this work, we prepared temperature-responsive poly(N-isopropylacrylamide) (PNIPAm) microfibers with controlled shapes and sizes by the in situ photo-polymerization of aqueous monomers loaded in calcium alginate templates generated from microcapillary devices. We found that the shape and size of the hydrogel microfibers could be controlled by adjusting the injection positions of the solutions and varying the diameters of the inner capillary, respectively. We further fabricated light-responsive materials by incorporating photothermal magnetite nanoparticles (MNPs) within the temperature-responsive PNIPAm hydrogel microfibers. Because the MNPs incorporated into the PNIPAm microfibers generated heat upon the absorption of visible light, we could demonstrate volume changes in the microfibers triggered by both visible light irradiation and temperature.