Nanometric self-assembling peptide layers maintain adult hepatocyte phenotype in sandwich cultures

Programmable short peptides for modulating stem cell fate in tissue engineering and regenerative medicine

Recent advancements in tissue engineering and regenerative medicine have introduced promising strategies to address tissue and organ deficiencies. This review highlights the critical role of short peptides, particularly their ability to self-assemble into matrices that mimic the extracellular matrix (ECM). These low molecular weight peptides exhibit target-specific activities, modulate gene expression, and influence cell differentiation pathways. They are stable, programmable, non-cytotoxic, biocompatible, biodegradable, capable of crossing the cell membrane and easy to synthesize. This review underscores the importance of peptide structure and concentration in directing stem cell differentiation and explores their diverse biomedical applications. Peptides such as Aβ1-40, Aβ1-42, RADA16, A13 and KEDW are discussed for their roles in modulating stem cell differentiation into neuronal, glial, myocardial, osteogenic, hepatocyte and pancreatic lineages. Furthermore, this review delves into the underlying signaling mechanisms, the chemistry and design of short peptides and their potential for engineering biocompatible materials that mimic stem cell microenvironments. Short peptide-based biomaterials and scaffolds represent a promising avenue in stem cell therapy, tissue engineering, and regenerative medicine.

Chemically Modified Dipeptide Based Hydrogel Supports Three-Dimensional Growth and Functions of Primary Hepatocytes

A huge shortage of organ donors, particularly in the case of liver, has necessitated the development of alternative therapeutic strategies. Primary hepatocytes (pHCs) transplantation has made a considerable transition from bench to bedside, but the short-term viability and functionality of pHCs in in vitro limit their use for clinical applications. Different cell culture strategies are required to maintain the proliferation of pHCs for extended periods. Here, we described the formation of a hybrid scaffold based on a modified dipeptide for the culture of pHCs. First, the dipeptide (Dp), isoleucine-α,β-dehydrophenylalanine (IΔF) was synthesized, purified, and fully characterized. IΔF readily formed a highly stable hydrogel, which was also characterized by CD, TEM, and thioflavin T assay. The addition of soluble liver extracellular matrix (sLEM) to the dipeptide readily formed a hybrid scaffold that was characterized by TEM, and its mechanical strength was determined by rheology experiments. The hybrid scaffold was translucent, biocompatible, and proteolytically stable and, with its mechanical strength, closely mimicked that of the native liver. LEM1-Dp matrix exhibited high biocompatibility in the readily available adherent liver cell line Huh7 and primary rat hepatocyte cells (pHCs). pHCs cultured on LEM1-Dp matrix also maintained significantly higher cell viability and an escalated expression of markers related to the hepatocytes such as albumin as compared to that observed in cells cultured on collagen type I (Col I)-coated substrate plate (col-TCTP). Z-stacking of confocal laser microscopy's volume view clearly indicated pHCs seeded on top of the hydrogel matrix migrated toward the Z direction showing 3D growth. Our results indicated that low molecular weight dipeptide hydrogel along with sLEM can resemble biomimetic 3D-like microenvironments for improved pHCs proliferation, differentiation, and function. This hybrid scaffold is also easy to scale up, which makes it suitable for several downstream applications of hepatocytes, including drug development, pHCs transplantation, and liver regeneration.

Peptide-based scaffolds for the culture and maintenance of primary human hepatocytes

We report here the use of a nanofibrous hydrogel as a 3D scaffold for the culture and maintenance of functional primary human hepatocytes. The system is based on the cooperative assembly of a fiber-forming peptide component, fluorenylmethyloxycarbonyl-diphenylalanine (Fmoc-FF), and the integrin-binding functional peptide ligand, Fmoc-arginine-glycine-aspartic acid (Fmoc-RGD) into a nanofibrous gel at physiological pH. This Fmoc-FF/RGD hydrogel was formulated to provide a biomimetic microenvironment with some critical features such as mechanical properties and nanofiber morphology, which were optimized to support hepatocyte culture. The material was shown to support maintenance and function of encapsulated primary human hepatocytes as indicated by actin staining, qRT-PCR, and functional cytochrome P450 assays. The designed gel was shown to outperform Matrigel in cytochrome P450 functional assays. The hydrogel may prove useful for liver development and disease models, as well as providing insights into the design of future implantable scaffolds for the regeneration of liver tissue in patients with liver disease.

Three-dimensional culture and clinical drug responses of a highly metastatic human ovarian cancer HO-8910PM cells in nanofibrous microenvironments of three hydrogel biomaterials

Background

Ovarian cancer is a highly aggressive malignant disease in gynecologic cancer. It is an urgent task to develop three-dimensional (3D) cell models in vitro and dissect the cell progression-related drug resistance mechanisms in vivo. In the present study, RADA16-I peptide has the reticulated nanofiber scaffold networks in hydrogel, which is utilized to develop robust 3D cell culture of a high metastatic human ovarian cancer HO-8910PM cell line accompanied with the counterparts of Matrigel and collagen I.

Results

Consequently, HO-8910PM cells were successfully cultivated in three types of hydrogel biomaterials, such as RADA16-I hydrogel, Matrigel, and collagen I, according to 3D cell culture protocols. Designer RADA16-I peptide had well-defined nanofiber networks architecture in hydrogel, which provided nanofiber cell microenvironments analogous to Matrigel and collagen I. 3D-cultured HO-8910PM cells in RADA16-I hydrogel, Matrigel, and collagen I showed viable cell proliferation, proper cell growth, and diverse cell shapes in morphology at the desired time points. For a long 3D cell culture period, HO-8910PM cells showed distinct cell aggregate growth patterns in RADA16-I hydrogel, Matrigel, and collagen I, such as cell aggregates, cell colonies, cell clusters, cell strips, and multicellular tumor spheroids (MCTS). The cell distribution and alignment were described vigorously. Moreover, the molecular expression of integrin β1, E-cadherin and N-cadherin were quantitatively analyzed in 3D-cultured MCTS of HO-8910PM cells by immunohistochemistry and western blotting assays. The chemosensitivity assay for clinical drug responses in 3D context indicated that HO-8910PM cells in three types of hydrogels showed significantly higher chemoresistance to cisplatin and paclitaxel compared to 2D flat cell culture, including IC₅₀ values and inhibition rates.

Conclusion

Based on these results, RADA16-I hydrogel is a highly competent, high-profile, and proactive nanofiber scaffold to maintain viable cell proliferation and high cell vitality in 3D cell models, which may be particularly utilized to develop useful clinical drug screening platform in vitro.

Culture and Differentiation of Human Hair Follicle Dermal Papilla Cells in a Soft 3D Self-Assembling Peptide Scaffold

Hair follicle dermal papilla cells (HFDPC) are a specialized cell population located in the bulge of the hair follicle with unique characteristics such as aggregative behavior and the ability to induce new hair follicle formation. However, when expanded in conventional 2D monolayer culture, their hair inductive potency is rapidly lost. Different 3D culture techniques, including cell spheroid formation, have been described to restore, at least partially, their original phenotype, and therefore, their hair inductive ability once transplanted into a recipient skin. Moreover, hair follicle dermal papilla cells have been shown to differentiate into all mesenchymal lineages, but their differentiation potential has only been tested in 2D cultures. In the present work, we have cultured HFDPC in the 3D self-assembling peptide scaffold RAD16-I to test two different tissue engineering scenarios: restoration of HFDPC original phenotype after cell expansion and osteogenic and adipogenic differentiation. Experimental results showed that the 3D environment provided by RAD16-I allowed the restoration of HFDPC signature markers such as alkaline phosphatase, versican and corin. Moreover, RAD16-I supported, in the presence of chemical inductors, three-dimensional osteogenic and adipogenic differentiation. Altogether, this study suggests a potential 3D culture platform based on RAD16-I suitable for the culture, original phenotype recovery and differentiation of HFDPC.

Improving linking interface between collagen-based hydrogels and bone-like substrates

Regenerative medicine requires the use of heterogeneous scaffolds when the tissue that needs to be repaired presents a gradient in its properties and cannot be replaced by a homogeneous graft. Then, an intimate contact between the different layers is critical to guarantee the optimal performance of the construct. This work presents a procedure that allows the immobilization of collagen-based hydrogels by self-assembly onto any desired substrate, by means of a pentafluorophenyl methacrylate (PFM) coating obtained by plasma enhanced chemical vapor deposition and a collagen monolayer. The latter is attached onto the PFM-coated substrate thanks to its high reactivity towards amines and it will act as anchoring point for the subsequent collagen fibrillation and hydrogel formation. The interaction between collagen and PFM-coated substrates has been evaluated using the quartz crystal microbalance with dissipation (QCM-D) technique. In addition, QCM-D has been used to design and monitor the collagen fibril formation process. A correlation between QCM-D data and optical microscopy has been established, and fibril formation has been confirmed by atomic force microscopy (AFM).

A microfluidic 3D hepatocyte chip for hepatotoxicity testing of nanoparticles

Aim: To develop a practical microfluidic 3D hepatocyte chip for hepatotoxicity testing of nanoparticles using proof of concept studies providing first results of the potential hepatotoxicity of superparamagnetic iron oxide nanoparticles (SPION) under microfluidic conditions. Methods: A microfluidic 3D hepatocyte chip with three material layers, which contains primary rat hepatocytes, has been fabricated and tested using different concentrations (50, 100 and 200 μg/ml) of SPION in 3-day (short-term) and 1-week (long-term) cultures. Results: Compared with standard well plates, the hepatocyte chip with flow provided comparable viability and significantly higher liver-specific functions, up to 1 week. In addition, the chip recapitulates the key physiological responses in the hepatotoxicity of SPION. Conclusion: Thus, the developed 3D hepatocyte chip is a robust and highly sensitive platform for investigating hepatotoxicity profiles of nanoparticles.

High sensitive and selective electrochemical biosensor: Label-free detection of human norovirus using affinity peptide as molecular binder

Norovirus is known as the major cause of highly infection for gastrointestinal tracts. In this study, robust and highly sensitive biosensors for detecting human norovirus by employing a recognition affinity peptide-based electrochemical platform were described. A series of amino acid-substituted and cysteine-incorporated recognition peptides isolated from evolutionary phage display technique was chemically synthesized and immobilized to a gold sensor layer, the detection performance of the gold-immobilized synthetic peptide-based sensor system was assessed using QCM, CV and EIS. Using EIS, the limit of detection with Noro-1 as a molecular binder was found to be 99.8nM for recombinant noroviral capsid proteins (rP2) and 7.8copies/mL for human norovirus, thereby demonstrating a high degree of sensitivity for their corresponding targets. These results suggest that a biosensor which consists of affinity peptides as a molecular binder and miniaturized microdevices as diagnostic tool could be served as a new type of biosensing platform for point-of-care testing.

Chondroitin Sulfate- and Decorin-Based Self-Assembling Scaffolds for Cartilage Tissue Engineering

Cartilage injury and degenerative tissue progression remain poorly understood by the medical community. Therefore, various tissue engineering strategies aim to recover areas of damaged cartilage by using non-traditional approaches. To this end, the use of biomimetic scaffolds for recreating the complex in vivo cartilage microenvironment has become of increasing interest in the field. In the present study, we report the development of two novel biomaterials for cartilage tissue engineering (CTE) with bioactive motifs, aiming to emulate the native cartilage extracellular matrix (ECM). We employed a simple mixture of the self-assembling peptide RAD16-I with either Chondroitin Sulfate (CS) or Decorin molecules, taking advantage of the versatility of RAD16-I. After evaluating the structural stability of the bi-component scaffolds at a physiological pH, we characterized these materials using two different in vitro assessments: re-differentiation of human articular chondrocytes (AC) and induction of human adipose derived stem cells (ADSC) to a chondrogenic commitment. Interestingly, differences in cellular morphology and viability were observed between cell types and culture conditions (control and chondrogenic). In addition, both cell types underwent a chondrogenic commitment under inductive media conditions, and this did not occur under control conditions. Remarkably, the synthesis of important ECM constituents of mature cartilage, such as type II collagen and proteoglycans, was confirmed by gene and protein expression analyses and toluidine blue staining. Furthermore, the viscoelastic behavior of ADSC constructs after 4 weeks of culture was more similar to that of native articular cartilage than to that of AC constructs. Altogether, this comparative study between two cell types demonstrates the versatility of our novel biomaterials and suggests a potential 3D culture system suitable for promoting chondrogenic differentiation.

Dedifferentiated Human Articular Chondrocytes Redifferentiate to a Cartilage-Like Tissue Phenotype in a Poly(ε-Caprolactone)/Self-Assembling Peptide Composite Scaffold

Adult articular cartilage has a limited capacity for growth and regeneration and, with injury, new cellular or biomaterial-based therapeutic platforms are required to promote repair. Tissue engineering aims to produce cartilage-like tissues that recreate the complex mechanical and biological properties found in vivo. In this study, a unique composite scaffold was developed by infiltrating a three-dimensional (3D) woven microfiber poly (ε-caprolactone) (PCL) scaffold with the RAD16-I self-assembling nanofibers to obtain multi-scale functional and biomimetic tissue-engineered constructs. The scaffold was seeded with expanded dedifferentiated human articular chondrocytes and cultured for four weeks in control and chondrogenic growth conditions. The composite constructs were compared to control constructs obtained by culturing cells with 3D woven PCL scaffolds or RAD16-I independently. High viability and homogeneous cell distribution were observed in all three scaffolds used during the term of the culture. Moreover, gene and protein expression profiles revealed that chondrogenic markers were favored in the presence of RAD16-I peptide (PCL/RAD composite or alone) under chondrogenic induction conditions. Further, constructs displayed positive staining for toluidine blue, indicating the presence of synthesized proteoglycans. Finally, mechanical testing showed that constructs containing the PCL scaffold maintained the initial shape and viscoelastic behavior throughout the culture period, while constructs with RAD16-I scaffold alone contracted during culture time into a stiffer and compacted structure. Altogether, these results suggest that this new composite scaffold provides important mechanical requirements for a cartilage replacement, while providing a biomimetic microenvironment to re-establish the chondrogenic phenotype of human expanded articular chondrocytes.

Self-assembling peptide-based delivery of therapeutics for myocardial infarction

Cardiovascular disease, including myocardial infarction, is the number one cause of death. Current treatments are palliative and slow the progression toward heart failure, but to not regenerate healthy tissue. Self-assembling peptides are biomimietic, readily produced, non-immunogenic and non-cytotoxic. They do not assemble into hydrogels until triggered, allowing them to be injected into the myocardium and providing opportunities for minimally invasive therapies. The ability to tune the mechanical and bioactive properties of self-assembling peptides will continue to make them readily adaptable for mimicking natural microenvironments. To date, a variety of growth factors and signaling moieties have been incorporated into self-assembling peptide hydrogels, enhancing cell behavior and tissue function. Furthermore, the hydrogels serve as delivery vehicles for cells in vivo and platforms for improved cell culture. In addition to a brief review of self-assembling peptides, we will discuss a variety of their approaches for myocardial infarction therapy. Moreover, we will assess approaches taken in other tissue and discuss how these could benefit therapies for myocardial infarction.

A three-dimensional collagen-sponge-based culture system coated with simplified recombinant fibronectin improves the function of a hepatocyte cell line

Hepatocytes are widely used in pharmaceutical drug discovery tests, but their hepatic functions decrease rapidly during in vitro culture. Many culture systems have been devised to address this problem. We here report that a three-dimensional (3D) collagen-based scaffold coated with simplified recombinant fibronectin (FN) enhanced the function of a hepatocyte cell line. The developed culture system uses a honeycomb collagen sponge coated with collagen-binding domain (CBD)-cell attachment site (CAS), a chimeric protein comprising the CBD and CAS of FN. The function of HepG2 cells grown on honeycomb collagen sponge coated with CBD-CAS was investigated by determining the messenger RNA (mRNA) expression levels of several genes. The mRNA expression level of albumin increased 3.25 times in cells grown on CBD-CAS-coated honeycomb collagen sponge for 3 days; the expression level of CCAAT/enhancer binding protein (C/EBPα) increased 40-fold after 1 d and up to 150-fold after 3 d. These results suggested that CBD-CAS-coated honeycomb collagen sponge could improve the functions of hepatocytes by inducing C/EBPα expression. The activation of cytochrome P450 (CYP) enzymes in HepG2 cells grown on CBD-CAS-coated honeycomb collagen sponge was measured at the mRNA level and was found to increase between two and six times compared to cells grown without the CBD-CAS coating, showing that this culture system induced CYP gene expression and thus may be useful in drug metabolism assays.

Induction of albumin expression in HepG2 cells using immobilized simplified recombinant fibronectin protein

Optimization of the extracellular environment is very important for hepatocyte function in vitro. We expressed new chimeric proteins of the collagen-binding domain (CBD) with cell attachment site (CAS) of fibronectin to enhance hepatocyte function, and the CBD-CAS proteins were immobilized on collagen-coated plates. We hypothesized that the high density of CAS would increase activity of the integrin-dependent intracellular signaling pathway, thus inducing hepatocyte function. Expression of albumin in the human hepatocyte cell line HepG2 was assessed on CBD-CAS-immobilized dishes. The results indicated that the CBD-CAS-immobilized plates induced albumin expression. Immobilized CBD-CAS induced activation of focal adhesion kinase and integrin-ligand clustering on the cell membrane. These results suggest that immobilized CBD-CAS improves the function of HepG2 cells. This system could therefore be applied to drug metabolism assay in the development of new drugs.

Self-assembling functionalized nanopeptides for immediate hemostasis and accelerative liver tissue regeneration

Traumatic injury or surgery may trigger extensive bleeding. However, conventional hemostatic methods have limited efficacy and may cause surrounding tissue damage. In this study, we use self-assembling peptides (SAPs) and specifically extend fragments of functional motifs derived from fibronectin and laminin to evaluate the capability of these functionalized SAPs in the effect of hemostasis and liver tissue regeneration. From the results, these peptides can self-assemble into nanofibrous network structure and gelate into hydrogel with pH adjustment. In animal studies, the efficacy of hemostasis is achieved immediately within seconds in a rat liver model. The histological analyses by hematoxylin-eosin stain and immunohistochemistry reveal that SAPs with these functionalized motifs significantly enhance liver tissue regeneration. In brief, these SAPs may have potential as pharmacological tools to extensively advance clinical therapeutic applications in hemostasis and tissue regeneration in the field of regenerative medicine.

Development of a three-dimensional bone-like construct in a soft self-assembling peptide matrix

This work describes the development of a three-dimensional (3D) model of osteogenesis using mouse preosteoblastic MC3T3-E1 cells and a soft synthetic matrix made out of self-assembling peptide nanofibers. By adjusting the matrix stiffness to very low values (around 120 Pa), cells were found to migrate within the matrix, interact forming a cell-cell network, and create a contracted and stiffer structure. Interestingly, during this process, cells spontaneously upregulate the expression of bone-related proteins such as collagen type I, bone sialoprotein, and osteocalcin, indicating that the 3D environment enhances their osteogenic potential. However, unlike MC3T3-E1 cultures in 2D, the addition of dexamethasone is required to acquire a final mature phenotype characterized by features such as matrix mineralization. Moreover, a slight increase in the hydrogel stiffness (threefold) or the addition of a cell contractility inhibitor (Rho kinase inhibitor) abrogates cell elongation, migration, and 3D culture contraction. However, this mechanical inhibition does not seem to noticeably affect the osteogenic process, at least at early culture times. This 3D bone model intends to emphasize cell-cell interactions, which have a critical role during tissue formation, by using a compliant unrestricted synthetic matrix.

Primary hepatocyte cultures for pharmaco-toxicological studies: at the busy crossroad of various anti-dedifferentiation strategies

Continuously increasing understanding of the molecular triggers responsible for the onset of diseases, paralleled by an equally dynamic evolution of chemical synthesis and screening methods, offers an abundance of pharmacological agents with a potential to become new successful drugs. However, before patients can benefit of newly developed pharmaceuticals, stringent safety filters need to be applied to weed out unfavourable drug candidates. Cost effectiveness and the need to identify compound liabilities, without exposing humans to unnecessary risks, has stimulated the shift of the safety studies to the earliest stages of drug discovery and development. In this regard, in vivo relevant organotypic in vitro models have high potential to revolutionize the preclinical safety testing. They can enable automation of the process, to match the requirements of high-throughput screening approaches, while satisfying ethical considerations. Cultures of primary hepatocytes became already an inherent part of the preclinical pharmaco-toxicological testing battery, yet their routine use, particularly for long-term assays, is limited by the progressive deterioration of liver-specific features. The availability of suitable hepatic and other organ-specific in vitro models is, however, of paramount importance in the light of changing European legal regulations in the field of chemical compounds of different origin, which gradually restrict the use of animal studies for safety assessment, as currently witnessed in cosmetic industry. Fortunately, research groups worldwide spare no effort to establish hepatic in vitro systems. In the present review, both classical and innovative methodologies to stabilize the in vivo-like hepatocyte phenotype in culture of primary hepatocytes are presented and discussed.

Cells and materials for liver tissue engineering

Liver transplantation is currently the most efficacious treatment for end-stage liver diseases. However, one main problem with liver transplantation is the limited number of donor organs that are available. Therefore, liver tissue engineering based on cell transplantation that combines materials to mimic the liver is under investigation with the goal of restoring normal liver functions. Tissue engineering aims to mimic the interactions among cells with a scaffold. Particular materials or a matrix serve as a scaffold and provide a three-dimensional environment for cell proliferation and interaction. Moreover, the scaffold plays a role in regulating cell maturation and function via these interactions. In cultures of hepatic lineage cells, regulation of cell proliferation and specific function using biocompatible synthetic, biodegradable bioderived matrices, protein-coated materials, surface-modified nanofibers, and decellularized biomatrix has been demonstrated. Furthermore, beneficial effects of addition of growth factor cocktails to a flow bioreactor or coculture system on cell viability and function have been observed. In addition, a system for growing stem cells, liver progenitor cells, and primary hepatocytes for transplantation into animal models was developed, which produces hepatic lineage cells that are functional and that show long-term proliferation following transplantation. The major limitation of cells proliferated with matrix-based transplantation systems is the high initial cell loss and dysfunction, which may be due to the absence of blood flow and the changes in nutrients. Thus, the development of vascular-like scaffold structures, the formation of functional bile ducts, and the maintenance of complex metabolic functions remain as major problems in hepatic tissue engineering and will need to be addressed to enable further advances toward clinical applications.

Engineering membrane scaffolds with both physical and biomolecular signaling

We report on the combination of a top-down and bottom-up approach to develop thin bioactive membrane scaffolds based on functional elastin-like polymers (ELPs). Our strategy combines ELP cross-linking and assembly, and a variety of standard and novel micro/nanofabrication techniques to create self-supporting membranes down to ∼500 nm thick that incorporate both physical and biomolecular signals, which can be easily tailored for a specific application. In this study we used an ELP that included the cell-binding motif arginine-glycine-aspartic acid-serine (RGDS). Furthermore, fabrication processes were developed to create membranes that exhibited topographical patterns with features down to 200 nm in lateral dimensions and up to 10 μm in height on either one or both sides, uniform and well-defined pores, or multiple ELP layers. A variety of processing parameters were tested in order to optimize membrane fabrication, including ELP and cross-linker concentration, temperature, reaction time and ambient humidity. Membrane micro/nanopatterning, swelling and stiffness were characterized by atomic force microscopy, nanoindentation tests and scanning electron microscopy. Upon immersion in phosphate-buffered saline and an increase in temperature from 25 to 40°C, membranes exhibited a significant increase in surface stiffness, with the reduced Young's modulus increasing with temperature. Finally, rat mesenchymal stem cells were cultured on thin RGDS-containing membranes, which allowed cell adhesion, qualitatively enhanced spreading compared to membranes without RGDS epitopes and permitted proliferation. Furthermore, cell morphology was drastically affected by topographical patterns on the surface of the membranes.

WITHDRAWN: The effect of molecular design on the physical and biological properties of complementary self-assembling peptides

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.