Two-way regulation between cells and aligned collagen fibrils: local 3D matrix formation and accelerated neural differentiation of human decidua parietalis placental stem cells

Localized trans-browning and pro-angiogenesis inductive self-assembled collagen resveratrol bio-matrix for tissue repair and regeneration in obese conditions

The present study probes into the complexities of wound management in obesity by proposing a novel biomaterial designed to reprogram the altered skin physiology prevalent in obese conditions. The strategy involves the development of a multifunctional biomaterial addressing issues such as excessive exudate, pressure ulcers, and reduced vascularity. The bio-matrix demonstrates the localized transformation of white adipocytes through trans-browning, coupled with the simultaneous induction of angiogenesis at obese wound sites, resulting in expedited wound closure. The collagen bio-matrices, stabilized with Resveratrol (Rsv), exhibit remarkable thermal, mechanical, and biological stability. The porous 3D microstructure of the Rsv-stabilized collagen bio-matrix closely resembled the natural extracellular matrix, facilitating effective cell adhesion. The bio-matrix exhibited the unique capability to induce localized thermogenesis in the subcutaneous fat layer while concurrently activating angiogenesis. In vivo wound healing studies conducted on DIO-C57BL6 mice demonstrated complete healing within 10 days, showcasing accelerated tissue regeneration, blood vessel formation, robust collagen deposition, and significant activation of browning in the subcutaneous adipose layer. This study introduces the concept of tailored regenerative biomaterials with the ability to reprogram the challenging wound environment associated with obesity. This innovative approach opens up new avenues for enhanced wound care strategies, particularly for bariatric patients.

Apigenin Self-Assembled Collagen Biomatrix for Reprogramming the Obese Wound Microenvironment for Its Management and Repair

Wound management in obesity is complicated by excessive exudates from wounded areas, pressure ulcerations due to stacking of the fat layer, and vascular rarefaction. The current study explored the development of biomaterials for reprogramming the altered wound microenvironment under obese conditions. Self-assembled collagen biomatrix with trans and de novo browning activator, apigenin, was fabricated as a soft tissue regenerative wound dressing material. The as-synthesized self-assembled collagen biomatrix exhibited excellent thermal, mechanical, and biological stability with a superior wound exudate absorption capacity. The apigenin self-assembled collagen biomatrix exhibited porous 3-D microstructure that mimicked the extracellular matrix that promoted cell adhesion and proliferation. The apigenin self-assembled collagen multifunctional biomatrix triggered adaptive localized thermogenesis in the subcutaneous fat layer, resulting in the activation of angiogenesis and fibroblast spreading and migration. The in vivo wound healing assay performed in DIO-C57BL6 mice showed faster tissue regeneration within 9 days, with well-defined neo-epidermis, blood vessel formation, thick collagen deposition, minimal inflammation, and significant activation of browning in the subcutaneous adipose layer. This study paves the way forward for the development of specialized regenerative biomatrices that reprogram the obese wound bed for faster tissue regeneration.

3D Bioprinting of Neurovascular Tissue Modeling with Collagen-Based Low-Viscosity Composites

In vitro neurovascular unit (NVU) models are valuable for investigating brain functions and developing drugs. However, it remains challenging to recapitulate the native architectural features and ultra-soft extracellular matrix (ECM) properties of the natural NVU. Cell-laden bioprinting is promising to prepare complex living tissues, but hard to balance the fidelity and cell growth. This study proposes a novel two-stage methodology for biomanufacturing functional 3D neurovascular constructs in vitro with low modulus of ECM. At the shaping stage, a low-viscosity alginate/collagen is printed through an embedded approach; at the culturing stage, the alginate is removed through targeted lysing. The low-viscosity and rapid crosslinking properties provide a printing resolution of ≈10 µm, and the lysis processing can decrease the hydrogels' modulus to ≈1 kPa and adjust the porosity of the microstructure, providing cells with an environment closing to the brain ECM. A 3D hollow coaxial neurovascular model is fabricated, in which the endothelial cells has expressed tight junction proteins and shown selective permeability, and the astrocytes outside of the endothelial layer are found to spread out with branches and directly interact with endothelial cells. The present study offers a promising modeling method for better understanding the NVU function and screening neuro-drugs.

Electrospun Silk Fibroin-CNT Composite Fibers: Characterization and Application in Mediating Fibroblast Stimulation

Electrospinning is a simple, low-cost, and highly efficient technique to generate desirable nano/microfibers from polymer solutions. Silk fibroin (SF), a biopolymer found in Bombyx mori cocoons, has attracted attention for various biomedical applications. In this study, functionalized CNT was incorporated in SF to generate biocomposite fibers by electrospinning. The electrospun (E-spun) fibers were well aligned with morphology mimicking the locally oriented ECM proteins in connective tissues. While as-spun fibers dissolved in water in just two minutes, ethanol vapor post-treatment promoted β-sheet formation leading to improved fiber stability in an aqueous environment (>14 days). The addition of a minute amount of CNT effectively improved the E-spun fiber alignment and mechanical strength while retained high biocompatibility and biodegradability. The fibers’ electrical conductivity increased by 13.7 folds and 21.8 folds, respectively, in the presence of 0.1 w% and 0.2 w% CNT in SF fibers. With aligned SF-CNT 0.1 % fibers as a cell culture matrix, we found electrical stimulation effectively activated fibroblasts from patients of pelvic organ prolapse (POP), a connective tissue disorder. The stimulation boosted the fibroblasts’ productivity of collagen III (COLIII) and collagen I (COLI) by 74 folds and 58 folds, respectively, and reduced the COLI to COLIII ratio favorable for tissue repair. The developed material and method offer a simple, direct, and effective way to remedy the dysfunctional fibroblasts of patients for personalized cell therapeutic treatment of diseases and health conditions associated with collagen disorder.

Distinctive structure, composition and biomechanics of collagen fibrils in vaginal wall connective tissues associated with pelvic organ prolapse

Collagen is the predominant structural protein within connective tissues. Pelvic organ prolapse (POP) is characterized by weakening of the pelvic floor connective tissues and loss of support for pelvic organs. In this study, we examined the multiscale structure, molecular composition and biomechanics of native collagen fibrils in connective tissues of the posterior vaginal fornix collected from healthy women and POP patients, and established the correlation of these properties with clinical POP quantification (POP-Q) scores. The collagen characteristics, including collagen amount, ratio of Collagen I and Collagen III, collagen fibril d-period, alignment and stiffness, were found to change progressively with the increase of the clinical measurement of Point C, a measure of uterine descent and apical prolapse. The results imply that a severe prolapse is associated with stiffer collagen fibrils, reduced collagen d-period, increased fibril alignment and imbalanced collagen synthesis, degradation and deposition. Additionally, prolapse progression appears to be synchronized with deterioration of the collagen matrix, suggesting that a POP-Q score obtained via a non-invasive clinical test can be potentially used to quantitatively assess collagen abnormality of a patient's local tissue. STATEMENT OF SIGNIFICANCE: Abnormal collagen metabolism and deposition are known to associate with connective tissue disorders, such as pelvic organ prolapse. Quantitative correlation of the biochemical and biophysical characteristics of collagen in a prolapse patient's tissue with the clinical diagnostic measurements is unexplored and unestablished. This study fills the knowledge gap between clinical prolapse quantification and the individual's cellular and molecular disorders leading to connective tissue failure, thus, provides the basis for clinicians to employ personalized treatment that can best manage the patient's condition and to alert pre-symptomatic patients for early management to avoid unwanted surgery.

Construction and Application of Hepatocyte Model Based on Microfluidic Chip Technique in Evaluating Emodin

The current cytological evaluation technique of health food raw materials does not entirely meet the needs of evaluating health food. Our study adopted the microfluidic chip technique for the first time to construct a hepatocyte model of evaluating emodin, which was composed of a human hepatocellular carcinoma cell (HepG2) and microfluidic chip. The mixed glue of a model with rat tail collagen type I (1.3 mg/mL) + gelatin (7.5%) was used to simulate the microenvironment of a cell. The validity of this model was evaluated by cell proliferation activity and cell staining, and the toxicity of emodin was evaluated by a series of metabolic indicators on this model. The results indicated that the repeatability of the constructed hepatocyte model was favorable, with a coefficient of variation (CV) of 2.8%. After emodin continuously was exposed for 48 h, the cell inhibition was obvious at 100 and 200 μM, and the number of dead cells gradually increased with the increasing of emodin concentration, and the difference of BUN was significant between the emodin group and blank group (p < 0.05). The constructed model has a favorable applicability in evaluating emodin. This study provides an important platform and a potential in vitro alternative model for assessing and predicting the health effects of health food.

Control of stem cell differentiation by using extrinsic photobiomodulation in conjunction with cell adhesion pattern

The induction and direction of stem cell differentiation into needed cell phenotypes is the central pillar of tissue engineering for repairing damaged tissues or organs. Conventionally, a special recipe of chemical factors is formulated to achieve this purpose for each specific target cell type. In this work, it is demonstrated that the combination of extrinsic photobiomodulation and collagen-covered microislands could be used to induce differentiation of Wharton’s jelly mesenchymal stem cells (WJ-MSCs) with the differentiation direction dictated by the specific island topography without use of chemical factors. Both neurogenic differentiation and adipogenic differentiation could be attained with a rate surpassing that using chemical factors. Application of this method to other cell types is possible by utilizing microislands with a pattern tailored particularly for each specific cell type, rendering it a versatile modality for initiating and guiding stem cell differentiation.

A 3-Dimensional In Vitro Model of Zonally Organized Extracellular Matrix

OBJECTIVE

Functional cartilage repair requires the new formation of organized hyaline cartilaginous matrix to avoid the generation of fibrous repair tissue. The potential of mesenchymal progenitors was used to assemble a 3-dimensional structure in vitro, reflecting the zonation of collagen matrix in hyaline articular cartilage.

DESIGN

The 3-dimensional architecture of collagen alignment in pellet cultures of chondroprogenitors (CPs) was assessed with Picrosirius red staining analyzed under polarized light. In parallel assays, the trilineage capability was confirmed by calcium deposition during osteogenesis by alizarin S staining and alkaline phosphatase staining. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), mRNA levels of ALP, RUNX2, and BGLAP were assessed after 21 days of osteoinduction. Lipid droplets were stained with oil red O and adipogenic differentiation was confirmed by RT-qPCR analysis of PPARG and LPL gene expression.

RESULTS

Under conditions promoting the chondrogenic signature in self-assembling constructs, CPs formed an aligned extracellular matrix, positive for glycosaminoglycans and collagen type II, showing developing zonation of birefringent collagen fibers along the cross section of pellets, which reflect the distribution of collagen fibers in hyaline cartilage. Induced osteogenic and adipogenic differentiation confirmed the trilineage potential of CPs.

CONCLUSION

This model promotes the differentiation and self-organization of postnatal chondroprogenitors, resulting in the formation of zonally organized engineered hyaline cartilage comparable to the 3 zones of native cartilage.

3D hydrogel models of the neurovascular unit to investigate blood-brain barrier dysfunction

The neurovascular unit (NVU), consisting of neurons, glial cells, vascular cells (endothelial cells, pericytes and vascular smooth muscle cells (VSMCs)) together with the surrounding extracellular matrix (ECM), is an important interface between the peripheral blood and the brain parenchyma. Disruption of the NVU impacts on blood-brain barrier (BBB) regulation and underlies the development and pathology of multiple neurological disorders, including stroke and Alzheimer's disease (AD). The ability to differentiate induced pluripotent stem cells (iPSCs) into the different cell types of the NVU and incorporate them into physical models provides a reverse engineering approach to generate human NVU models to study BBB function. To recapitulate the in vivo situation such NVU models must also incorporate the ECM to provide a 3D environment with appropriate mechanical and biochemical cues for the cells of the NVU. In this review, we provide an overview of the cells of the NVU and the surrounding ECM, before discussing the characteristics (stiffness, functionality and porosity) required of hydrogels to mimic the ECM when incorporated into in vitro NVU models. We summarise the approaches available to measure BBB functionality and present the techniques in use to develop robust and translatable models of the NVU, including transwell models, hydrogel models, 3D-bioprinting, microfluidic models and organoids. The incorporation of iPSCs either without or with disease-specific genetic mutations into these NVU models provides a platform in which to study normal and disease mechanisms, test BBB permeability to drugs, screen for new therapeutic targets and drugs or to design cell-based therapies.

Aligned Collagen-CNT Nanofibrils and the Modulation Effect on Ovarian Cancer Cells

Fibrillar collagen is a one-dimensional biopolymer and is the most abundant structural protein in the extracellular matrix (ECM) of connective tissues. Due to the unique properties of carbon nanotubes (CNTs), considerable attention has been given to the application of CNTs in developing biocomposite materials for tissue engineering and drug delivery. When introduced to tissues, CNTs inevitably interact and integrate with collagen and impose a discernible effect on cells in the vicinity. The positive effect of the collagen-CNT (COL-CNT) matrix in tissue regeneration and the cytotoxicity of free CNTs have been investigated extensively. In this study, we aimed to examine the effect of COL-CNT on mediating the interaction between the matrix and SKOV3 ovarian cancer cells. We generated unidirectionally aligned collagen and COL-CNT nanofibrils, mimicking the structure and dimension of collagen fibrils in native tissues. AFM analysis revealed that the one-dimensional structure, high stiffness, and low adhesion of COL-CNT greatly facilitated the polarization of SKOV3 cells by regulating the β−1 integrin-mediated cell–matrix interaction, cytoskeleton rearrangement, and cell migration. Protein and gene level analyses implied that both collagen and COL-CNT matrices induced the epithelial–mesenchymal transition (EMT), and the COL-CNT matrix prompted a higher level of cell transformation. However, the induced cells expressed CD44 at a reduced level and MMP2 at an increased level, and they were responsive to the chemotherapy drug gemcitabine. The results suggested that the COL-CNT matrix induced the transdifferentiation of the epithelial cancer cells to mature, less aggressive, and less potent cells, which are inapt for tumor metastasis and chemoresistance. Thus, the presence of CNT in a collagen matrix is unlikely to cause an adverse effect on cancer patients if a controlled dose of CNT is used for drug delivery or tissue regeneration.

Distinctive roles of fibrillar collagen I and collagen III in mediating fibroblast-matrix interaction: A nanoscopic study

One major goal in tissue engineering is to create functional materials, mimicking scaffolds in native tissues, to modulate cell function for tissue repair. Collagen is the most abundant structural protein in human body. Though collagen I (COLI) and collagen III (COLIII) are the predominant collagen types in connective tissues and they form stable hybrid fibrils at varied ratios, cell responses to the hybrid matrices are underinvestigated. In this work, we aim to explicate the distinctive roles of COLI and COLIII in fibroblast activation. Unidirectionally aligned COLI, COLIII and COLI-COLIII hybrid nanofibrils were generated via epitaxial growth of collagen on mica. AFM analyses revealed that, with the increase of COLI/COLIII ratio, the fibril width and stiffness increased and the binding affinity of cells to the matrix decreased. A hybrid matrix was found to activate fibroblasts the most effectively, characterized by extensive cell polarization with rigid stress fiber bundles and high α-SMA expression, and by the highest-level of collagen synthesis. It is ascribed to the fine balance between biochemical and biophysical cues achieved on the hybrid matrix. Thus, matrices of aligned COLI-COLIII hybrid fibrils and their derived multifunctional composites can be good candidates of implantation scaffolds for tissue regeneration.

Marangoni flows drive the alignment of fibrillar cell-laden hydrogels

When a sessile droplet containing a solute in a volatile solvent evaporates, flow in the droplet can transport and assemble solute particles into complex patterns. Transport in evaporating sessile droplets has largely been examined in solvents that undergo complete evaporation. Here, we demonstrate that flow in evaporating aqueous sessile droplets containing type I collagen-a self-assembling polymer-can be harnessed to engineer hydrated networks of aligned collagen fibers. We find that Marangoni flows direct collagen fiber assembly over millimeter-scale areas in a manner that depends on the rate of self-assembly, the relative humidity of the surrounding environment, and the geometry of the droplet. Skeletal muscle cells that are incorporated into and cultured within these evaporating droplets collectively orient and subsequently differentiate into myotubes in response to aligned networks of collagen. Our findings demonstrate a simple, tunable, and high-throughput approach to engineer aligned fibrillar hydrogels and cell-laden biomimetic materials.

Silk-CNT Mediated Fibroblast Stimulation toward Chronic Wound Repair

Background

Diabetic patients suffer from chronic wounds partly due to altered function of fibroblasts. Fibroblasts of diabetic patients synthesize collagen I (COLI) at a much higher level than collagen III (COLIII), resulting in delayed tissue granulation and, consequently, a delay in the overall wound healing process.

Methods

We aimed to revive the matrix protein productivity of diabetic fibroblasts by employing aligned, electrically conductive and biocompatible spider silk-CNT fibers as a cell culture matrix to mediate the electrical stimulation of fibroblasts to induce cell polarization and activation.

Results

A 5.2 and 42.7 fold increase in COLI and COLIII production was induced in diabetic fibroblasts. The stimulated cells synthesized a substantially high level of COLIII to reduce the abnormally high COLI/COLIII ratio, and the matrix metalloproteinases expression was markedly suppressed. The protein expression profile was consistent with favorable wound healing. The modulation effect was also demonstrated in normal fibroblasts of healthy individuals, suggesting that the developed method can be utilized generally for connective tissue repair. Silkworm silk-CNT fibers corroborated similar effects on restoring the function of diabetic fibroblasts.

Conclusions

The approach of using an engineered biopolymer matrix to remedy dysfunctional fibroblasts of patients offers the opportunity of developing personalized cell therapy for noninvasive treatments and inspires the design of multi-functional biometrics for effective tissue regeneration.

Comparing the effects of uncoated nanostructured surfaces on primary neurons and astrocytes

The long-term application of central nervous system implants is currently limited by the negative response of the brain tissue, affecting both the performance of the device and the survival of nearby cells. Topographical modification of implant surfaces mimicking the structure and dimensions of the extracellular matrix may provide a solution to this negative tissue response and has been shown to affect the attachment and behavior of both neurons and astrocytes. In our study, commonly used neural implant materials, silicon, and platinum were tested with or without nanoscale surface modifications. No biological coatings were used in order to only examine the effect of the nanostructuring. We seeded primary mouse astrocytes and hippocampal neurons onto four different surfaces: flat polysilicon, nanostructured polysilicon, and platinum-coated versions of these surfaces. Fluorescent wide-field, confocal, and scanning electron microscopy were used to characterize the attachment, spreading and proliferation of these cell types. In case of astrocytes, we found that both cell number and average cell spreading was significantly larger on platinum, compared to silicon surfaces, while silicon surfaces impeded glial proliferation. Nanostructuring did not have a significant effect on either parameter in astrocytes but influenced the orientation of actin filaments and glial fibrillary acidic protein fibers. Neuronal soma attachment was impaired on metal surfaces while nanostructuring seemed to influence neuronal growth cone morphology, regardless of surface material. Taken together, the type of metals tested had a profound influence on cellular responses, which was only slightly modified by nanopatterning.

Electrospun protein-CNT composite fibers and the application in fibroblast stimulation

Functional biopolymer scaffolds are in high demand for tissue regeneration. In this study, we incorporated functionalized CNT in collagen or silk protein solution to generate biocomposite fibers by electrospinning. The addition of CNT reinforced the strength of the scaffolds and rendered the fibers electrical conductivity to not only facilitate the E-spun fiber formation but also grant the fibers an additional functionality that can be utilized for cell stimulation. Considering fiber dimension, alignment, mechanical strength, electrical conductivity and biocompatibility, silk-CNT fibers containing a minute amount of CNT (0.05%) outperformed other fiber types. The modulation effect of these fibers was examined by their application in inducing polarization and activation of fibroblasts with cellular deficit. While the fibroblasts on both collagen-CNT and silk-CNT fibers synthesized a substantially higher level of collagen type III (COLIII) than cells on pure protein fibers to reduce the abnormally high COLI/COLIII ratio, electrical stimulation boosted the collagen productivity by 20 folds in cells on silk-CNT than on collagen-CNT due to silk-CNT's high electrical conductivity. The developed approach can be potentially utilized to remedy the dysfunctional fibroblasts for therapeutic treatment of diseases and health conditions associated with collagen disorder.

Neural stem cell differentiation into mature neurons: Mechanisms of regulation and biotechnological applications

The abilities of stem cells to self-renew and form different mature cells expand the possibilities of applications in cell-based therapies such as tissue recomposition in regenerative medicine, drug screening, and treatment of neurodegenerative diseases. In addition to stem cells found in the embryo, various adult organs and tissues have niches of stem cells in an undifferentiated state. In the central nervous system of adult mammals, neurogenesis occurs in two regions: the subventricular zone and the dentate gyrus in the hippocampus. The generation of the different neural lines originates in adult neural stem cells that can self-renew or differentiate into astrocytes, oligodendrocytes, or neurons in response to specific stimuli. The regulation of the fate of neural stem cells is a finely controlled process relying on a complex regulatory network that extends from the epigenetic to the translational level and involves extracellular matrix components. Thus, a better understanding of the mechanisms underlying how the process of neurogenesis is induced, regulated, and maintained will provide elues for development of novel for strategies for neurodegenerative therapies. In this review, we focus on describing the mechanisms underlying the regulation of the neuronal differentiation process by transcription factors, microRNAs, and extracellular matrix components.

Controlling human corneal stromal stem cell contraction to mediate rapid cell and matrix organization of real architecture for 3-dimensional tissue equivalents

The architecture of the human corneal stroma consists of a highly organized extracellular matrix (ECM) interspersed with keratocytes. Their progenitor cells; corneal stromal stem cells (CSSC) are located at the periphery, in the limbal stroma. A highly organized corneal ECM is critical for effective transmission of light but this structure may be compromised during injury or disease, resulting in loss of vision. Re-creating normal organization in engineered tissue equivalents for transplantation often involves lengthy culture times that are inappropriate for clinical use or utilisation of synthetic substrates that bring complications such as corneal melting. CSSC have great therapeutic potential owing to their ability to reorganize a disorganized matrix, restoring transparency in scarred corneas. We examined CSSC contractile behavior to assess whether this property could be exploited to rapidly generate cell and ECM organization in Real Architecture For 3D Tissues (RAFT) tissue equivalents (TE) for transplantation. Free-floating collagen gels were characterized to assess contractile behavior of CSSC and establish optimum cell density and culture times. To mediate cell and collagen organization, tethered collagen gels seeded with CSSC were cultured and subsequently stabilized with the RAFT process. We demonstrated rapid creation of biomimetic RAFT TE with tunable structural properties. These displayed three distinct regions of varying degrees of cellular and collagen organization. Interestingly, increased organization coincided with a dramatic loss of PAX6 expression in CSSC, indicating rapid differentiation into keratocytes. The organized RAFT TE system could be a useful bioengineering tool to rapidly create an organized ECM while simultaneously controlling cell phenotype.

STATEMENT OF SIGNIFICANCE

For the first time, we have demonstrated that human CSSC exhibit the phenomenon of cellular self-alignment in tethered collagen gels. We found this mediated rapid co-alignment of collagen fibrils and thus subsequently exploited this property in vitro to improve the architecture of engineered RAFT tissue equivalents of the corneal stroma. Existing techniques are extremely lengthy and carry significant risk and cost for GMP manufacture. This rapid and tunable technique takes just 8 h of culture and is therefore ideal for clinical manufacture, creating biomimetic tissue equivalents with both cellular and ECM organization. Thus, cellular self-alignment can be a useful bioengineering tool for the development of organized tissue equivalents in a variety of applications.

Bioengineering of the Human Neural Stem Cell Niche: A Regulatory Environment for Cell Fate and Potential Target for Neurotoxicity

Human neural stem/progenitor cells of the developing and adult organisms are surrounded by the microenvironment, so-called neurogenic niche. The developmental processes of stem cells, such as survival, proliferation, differentiation, and fate decisions, are controlled by the mutual interactions between cells and the niche components. Such interactions are tissue specific and determined by the biochemical and biophysical properties of the niche constituencies and the presence of other cell types. This dynamic approach of the stem cell niche, when translated into in vitro settings, requires building up "biomimetic" microenvironments resembling natural conditions, where the stem/progenitor cell is provided with diverse extracellular signals exerted by soluble and structural cues, mimicking those found in vivo. The neural stem cell niche is characterized by a unique composition of soluble components including neurotransmitters and trophic factors as well as insoluble extracellular matrix proteins and proteoglycans. Biotechnological innovations provide tools such as a new generation of tunable biomaterials capable of releasing specific signals in a spatially and temporally controlled manner, thus creating in vitro nature-like conditions and, when combined with stem cell-derived tissue specific progenitors, producing differentiated neuronal tissue structures. In addition, substantial progress has been made on the protocols to obtain stem cell-derived cell aggregates such as neurospheres and self-assembled organoids.In this chapter, we have assessed the application of bioengineered human neural stem cell microenvironments to produce in vitro models of different levels of biological complexity for the efficient control of stem cell fate. Examples of biomaterial-supported two-dimensional and three-dimensional (2D and 3D) complex culture systems that provide artificial neural stem cell niches are discussed in the context of their application for basic research and neurotoxicity testing.

New experimental models of the blood-brain barrier for CNS drug discovery

INTRODUCTION

The blood-brain barrier (BBB) is a dynamic biological interface which actively controls the passage of substances between the blood and the central nervous system (CNS). From a biological and functional standpoint, the BBB plays a crucial role in maintaining brain homeostasis inasmuch that deterioration of BBB functions are prodromal to many CNS disorders. Conversely, the BBB hinders the delivery of drugs targeting the brain to treat a variety of neurological diseases. Area covered: This article reviews recent technological improvements and innovation in the field of BBB modeling including static and dynamic cell-based platforms, microfluidic systems and the use of stem cells and 3D printing technologies. Additionally, the authors laid out a roadmap for the integration of microfluidics and stem cell biology as a holistic approach for the development of novel in vitro BBB platforms. Expert opinion: Development of effective CNS drugs has been hindered by the lack of reliable strategies to mimic the BBB and cerebrovascular impairments in vitro. Technological advancements in BBB modeling have fostered the development of highly integrative and quasi- physiological in vitro platforms to support the process of drug discovery. These advanced in vitro tools are likely to further current understanding of the cerebrovascular modulatory mechanisms.

Biocompatibility of Novel Type I Collagen Purified from Tilapia Fish Scale: An In Vitro Comparative Study

Type I collagen (COL-1) is the prevailing component of the extracellular matrix in a number of tissues including skin, ligament, cartilage, bone, and dentin. It is the most widely used tissue-derived natural polymer. Currently, mammalian animals, including pig, cow, and rat, are the three major sources for purification of COL-1. To reduce the risk of zoonotic infectious diseases transmission, minimize the possibility of immunogenic reaction, and avoid problems related to religious issues, exploration of new sources (other than mammalian animals) for the purification of type I collagen is highly desirable. Hence, the purpose of the current study was to investigate the in vitro responses of MDPC-23 to type I collagen isolated from tilapia scale in terms of cellular proliferation, differentiation, and mineralization. The results suggested that tilapia scale collagen exhibited comparable biocompatibility to porcine skin collagen, indicating it might be a potential alternative to type I collagen from mammals in the application for tissue regeneration in oral-maxillofacial area.

E-spun composite fibers of collagen and dragline silk protein: fiber mechanics, biocompatibility, and application in stem cell differentiation

Biocomposite matrices with high mechanical strength, high stability, and the ability to direct matrix-specific stem cell differentiation are essential for the reconstruction of lesioned tissues in tissue engineering and cell therapeutics. Toward this end, we used the electrospinning technique to fabricate well-aligned composite fibers from collagen and spider dragline silk protein, obtained from the milk of transgenic goats, mimicking the native extracellular matrix (ECM) on a similar scale. Collagen and the dragline silk proteins were found to mix homogeneously at all ratios in the electrospun (E-spun) fibers. As a result, the ultimate tensile strength and elasticity of the fibers increased monotonically with silk percentage, whereas the stretchability was slightly reduced. Strikingly, we found that the incorporation of silk proteins to collagen dramatically increased the matrix stability against excessive fiber swelling and shape deformation in cell culture medium. When human decidua parietalis placental stem cells (hdpPSCs) were seeded on the collagen–silk matrices, the matrices were found to support cell proliferation at a similar rate as that of the pure collagen matrix, but they provided cell adhesion with reduced strengths and induced cell polarization at varied levels. Matrices containing 15 and 30 wt % silk in collagen (CS15, CS30) were found to induce a level of neural differentiation comparable to that of pure collagen. In particular, CS15 matrix induced the highest extent of cell polarization and promoted the development of extended 1D neural filaments strictly in-line with the aligned fibers. Taking the increased mechanical strength and fiber stability into consideration, CS15 and CS30 E-spun fibers offer better alternatives to pure collagen fibers as scaffolds that can be potentially utilized in neural tissue repair and the development of future nanobiodevices.