Decellularized ECM effects on human mesenchymal stem cell stemness and differentiation

Role of Hedgehog Signaling Pathways in Multipotent Mesenchymal Stem Cells Differentiation

Multipotent mesenchymal stem cells (MSCs) have high self-renewal and multi-lineage differentiation potentials and low immunogenicity, so they have attracted much attention in the field of regenerative medicine and have a promising clinical application. MSCs originate from the mesoderm and can differentiate not only into osteoblasts, cartilage, adipocytes, and muscle cells but also into ectodermal and endodermal cell lineages across embryonic layers. To design cell therapy for replacement of damaged tissues, it is essential to understand the signaling pathways, which have a major impact on MSC differentiation, as this will help to integrate the signaling inputs to initiate a specific lineage. Hedgehog (Hh) signaling plays a vital role in the development of various tissues and organs in the embryo. As a morphogen, Hh not only regulates the survival and proliferation of tissue progenitor and stem populations but also is a critical moderator of MSC differentiation, involving tri-lineage and across embryonic layer differentiation of MSCs. This review summarizes the role of Hh signaling pathway in the differentiation of MSCs to mesodermal, endodermal, and ectodermal cells.

Hypoxic Extracellular Matrix Preserves Its Competence after Expansion of Human MSCs under Physiological Hypoxia In Vitro

Tissue-relevant O2 levels are considered as an important tool for the preconditioning of multipotent mesenchymal stromal cells (MSCs) for regenerative medicine needs. The present study investigated the quality and functions of the extracellular matrix (ECM) of MSCs under low O2 levels. Human adipose tissue-derived MSCs were continuously expanded under normoxia (20% O2, N) or "physiological" hypoxia (5% O2, Hyp). Decellularized ECM (dcECM) was prepared. The structure of the dcECM was analyzed using confocal laser and scanning electron microscopy. Collagen, dcECM-N, and dcECM-Hyp were recellularized with MSC-N and further cultured at normoxia. The efficacy of adhesion, spreading, growth, osteogenic potential, and paracrine activity of recellularized MSC-N were evaluated. At low O2, the dcECM showed an increased alignment of fibrillar structures and provided accelerated spreading of MSC-N, indicating increased dcECM-Hyp stiffness. We described O2-dependent "ECM-education" of MSC-N when cultured on dcECM-Hyp. This was manifested as attenuated spontaneous osteo-commitment, increased susceptibility to osteo-induction, and a shift in the paracrine profile. It has been suggested that the ECM after physiological hypoxia is able to ensure the maintenance of a low-commitment state of MSCs. DcECM, which preserves the competence of the natural microenvironment of cells and is capable of "educating" others, appears to be a prospective tool for guiding cell modifications for cell therapy and tissue engineering.

Biodegradable and Non-Biodegradable Biomaterials and Their Effect on Cell Differentiation

Biomaterials for tissue scaffolds are key components in modern tissue engineering and regenerative medicine. Targeted reconstructive therapies require a proper choice of biomaterial and an adequate choice of cells to be seeded on it. The introduction of stem cells, and the transdifferentiation procedures, into regenerative medicine opened a new era and created new challenges for modern biomaterials. They must not only fulfill the mechanical functions of a scaffold for implanted cells and represent the expected mechanical strength of the artificial tissue, but furthermore, they should also assure their survival and, if possible, affect their desired way of differentiation. This paper aims to review how modern biomaterials, including synthetic (i.e., polylactic acid, polyurethane, polyvinyl alcohol, polyethylene terephthalate, ceramics) and natural (i.e., silk fibroin, decellularized scaffolds), both non-biodegradable and biodegradable, could influence (tissue) stem cells fate, regulate and direct their differentiation into desired target somatic cells.

Proteomic Analysis of Decellularized Extracellular Matrix: Achieving a Competent Biomaterial for Osteogenesis

Decellularized ECMs have been used as biological scaffolds for tissue repair due to their tissue-specific biochemical and mechanical composition, poorly simulated by other materials. It is used as patches and powders, and it could be further processed via enzymatic digestion under acidic conditions using pepsin. However, part of the bioactivity is lost during the digestion process due to protein denaturation. Here, stepwise digestion was developed to prepare a competent biomaterial for osteogenesis from three different ECM sources. In addition, three different proteases were compared to evaluate the most effective digestion protocol for specific cellular processes. GAGs and peptide quantification showed that the stepwise method yielded a higher concentration of bioactive residues. Circular dichroism analysis also showed that the stepwise approach preserved the secondary structures better. The protein profiles of the digested ECMs were analyzed, and it was found to be highly diverse and tissue-specific. The digestion of ECM from pericardium produced peptides originated from 94 different proteins, followed by 48 proteins in ECM from tendon and 35 proteins in ECM from bone. In addition, digested products from pericardium ECM yielded increased proliferation and differentiation of bone marrow mesenchymal stem cells to mature osteoblasts.

Mechanical and Biocompatibility Properties of Sintered Titanium Powder for Mimetic 3D-Printed Bone Scaffolds

A composite comprising Ti and NaCl powders was sintered similar to a three-dimensional (3D)-printed patient-customized artificial bone scaffold. Additionally, a proper microstructure of the mimetic scaffold and the optimum processing parameters for its development were analyzed. The mechanical properties of the metal-based porous-structured framework used as an artificial bone scaffold were an optimum replacement for the human bone. Thus, it was confirmed that patient-customized scaffolds could be manufactured via 3D printing. The 3D-printed mimetic specimens were fabricated by a powder-sintering method using Ti for the metal parts, NaCl as the pore former, and polylactic acid as the biodegradable binder. Scanning electron microscopy (SEM) images showed that pores were formed homogeneously, while X-ray computed tomography confirmed that open pores were generated. The porosity and pore size distribution were measured using a mercury porosimeter, while the flexural strength and flexural elastic modulus were calculated using the three-point bending test. Based on these measurements, a pore-former content of 15 vol % optimized the density and flexural strength to 2.52 g cm^-2 and 283 MPa, respectively, similar to those of the actual iliac bone. According to the 3D-printing production method, a selective laser-sintering process was applied for the fabrication of the mimetic specimen, and it was determined that the microstructure and properties similar to those of previous metal specimens could be achieved in the as-prepared specimen. Additionally, a decellularized extracellular matrix (dECM) was used to coat the surfaces and interiors of the specimens for evaluating their biocompatibilities. SEM image analysis indicated that the adipose-derived stem cells grew evenly inside the pores of the coated specimens, as compared with the bulky Ti specimens without the dECM coating. The doubling time at 65% was measured at 72, 75, and 83 h for specimens with pore-former contents of 5, 10, and 15 vol %, respectively. The doubling time without the pore former was 116 h. As compared with the specimens without the pore former (73 h), 15% of the dECM-coated specimens showed a doubling time of 64%, measured at 47 h.

Decellularized matrix could affect the proliferation and differentiation of periodontal ligament stem cells in vitro

OBJECTIVE AND BACKGROUND

Recently, decellularized matrix (DCM) is considered as a new biomaterial for tissue regeneration. To explore the possible application of DCM in periodontal regeneration, the effect of DCM from three different cells on the proliferation and differentiation of human periodontal ligament stem cells (PDLSCs) was investigated.

METHODS

DCM derived from human periodontal ligament cells (PDLCs), dental pulp cells (DPCs), and gingival fibroblasts (GFs) were fabricated using Triton X-100/NH₄ OH combined with DNase I. Allogeneic PDLSCs were cultured on PDLC-DCM, DPC-DCM, and GF-DCM, respectively. The proliferative capacity of PDLSCs was evaluated by PicoGreen assay kit. The expression of alkaline phosphatase (ALP), runt-related transcription factor-2 (RUNX2), osteocalcin (OCN), collagen I (COL1), periostin (POSTN), and cementum protein 1 (CEMP1) were detected by qRT-PCR and western blotting.

RESULTS

PDLC-DCM, DPC-DCM, and GF-DCM had similar and integrated networks of extracellular matrix, as well as significantly decreased DNA content. Compared with control group in which PDLSCs were directly seeded in culture plates, PDLC-DCM, DPC-DCM, and GF-DCM promoted the proliferation of re-seeded PDLSCs. Additionally, PDLSCs on DCM exhibited higher mRNA and protein expression levels of ALP, RUNX2, OCN, and COL1. The expression of POSTN in PDLC-DCM group was significantly higher than control group at both mRNA and protein levels.

CONCLUSIONS

PDLC-DCM, DPC-DCM, and GF-DCM could enhance the proliferation of PDLSCs. PDLC-DCM facilitated osteogenic differentiation and periodontal ligament differentiation of PDLSCs, while DPC-DCM and GF-DCM promoted osteogenic differentiation.

Current Strategies for Tracheal Replacement: A Review

Airway cancers have been increasing in recent years. Tracheal resection is commonly performed during surgery and is burdened from post-operative complications severely affecting quality of life. Tracheal resection is usually carried out in primary tracheal tumors or other neoplasms of the neck region. Regenerative medicine for tracheal replacement using bio-prosthesis is under current research. In recent years, attempts were made to replace and transplant human cadaver trachea. An effective vascular supply is fundamental for a successful tracheal transplantation. The use of biological scaffolds derived from decellularized tissues has the advantage of a three-dimensional structure based on the native extracellular matrix promoting the perfusion, vascularization, and differentiation of the seeded cell typologies. By appropriately modulating some experimental parameters, it is possible to change the characteristics of the surface. The obtained membranes could theoretically be affixed to a decellularized tissue, but, in practice, it needs to ensure adhesion to the biological substrate and/or glue adhesion with biocompatible glues. It is also known that many of the biocompatible glues can be toxic or poorly tolerated and induce inflammatory phenomena or rejection. In tissue and organ transplants, decellularized tissues must not produce adverse immunological reactions and lead to rejection phenomena; at the same time, the transplant tissue must retain the mechanical properties of the original tissue. This review describes the attempts so far developed and the current lines of research in the field of tracheal replacement.

Tunable Human Myocardium Derived Decellularized Extracellular Matrix for 3D Bioprinting and Cardiac Tissue Engineering

The generation of 3D tissue constructs with multiple cell types and matching mechanical properties remains a challenge in cardiac tissue engineering. Recently, 3D bioprinting has become a powerful tool to achieve these goals. Decellularized extracellular matrix (dECM) is a common scaffold material due to providing a native biochemical environment. Unfortunately, dECM's low mechanical stability prevents usage for bioprinting applications alone. In this study, we developed bioinks composed of decellularized human heart ECM (dhECM) with either gelatin methacryloyl (GelMA) or GelMA-methacrylated hyaluronic acid (MeHA) hydrogels dual crosslinked with UV light and microbial transglutaminase (mTGase). We characterized the bioinks' mechanical, rheological, swelling, printability, and biocompatibility properties. Composite GelMA-MeHA-dhECM (GME) hydrogels demonstrated improved mechanical properties by an order of magnitude compared to the GelMA-dhECM (GE) hydrogels. All hydrogels were extrudable and compatible with human induced pluripotent stem cell derived cardiomyocytes (iCMs) and human cardiac fibroblasts (hCFs). Tissue-like beating of the printed constructs with striated sarcomeric alpha-actinin and connexin 43 expression was observed. The order of magnitude difference between the elastic modulus of these hydrogel composites offers applications in in vitro modeling of the myocardial infarct boundary. Here, as a proof of concept, we created an infarct boundary region with control over the mechanical properties along with the cellular and macromolecular content through printing iCMs with GE bioink and hCFs with GME bioink.

Umbilical Cord Pericytes Provide a Viable Alternative to Mesenchymal Stem Cells for Neonatal Vascular Engineering

Reconstructive surgery of congenital heart disease (CHD) remains inadequate due to the inability of prosthetic grafts to match the somatic growth of pediatric patients. Functionalization of grafts with mesenchymal stem cells (MSCs) may provide a solution. However, MSCs represent a heterogeneous population characterized by wide diversity across different tissue sources. Here we investigated the suitability of umbilical cord pericytes (UCPs) in neonatal vascular engineering. Explant outgrowth followed by immunomagnetic sorting was used to isolate neural/glial antigen 2 (NG2)+/CD31- UCPs. Expanded NG2 UCPs showed consistent antigenic phenotype, including expression of mesenchymal and stemness markers, and high proliferation rate. They could be induced to a vascular smooth muscle cell-like phenotype after exposure to differentiation medium, as evidenced by the expression of transgelin and smooth muscle myosin heavy chain. Analysis of cell monolayers and conditioned medium revealed production of extracellular matrix proteins and the secretion of major angiocrine factors, which conferred UCPs with ability to promote endothelial cell migration and tube formation. Decellularized swine-derived grafts were functionalized using UCPs and cultured under static and dynamic flow conditions. UCPs were observed to integrate into the outer layer of the graft and modify the extracellular environment, resulting in improved elasticity and rupture strain in comparison with acellular grafts. These findings demonstrate that a homogeneous pericyte-like population can be efficiently isolated and expanded from human cords and integrated in acellular grafts currently used for repair of CHD. Functional assays suggest that NG2 UCPs may represent a viable option for neonatal tissue engineering applications.

Epithelial-Mesenchymal Transition (EMT) as a Therapeutic Target

Metastasis is the spread of cancer cells from the primary tumour to distant sites and organs throughout the body. It is the primary cause of cancer morbidity and mortality, and is estimated to account for 90% of cancer-related deaths. During the initial steps of the metastatic cascade, epithelial cancer cells undergo an epithelial-mesenchymal transition (EMT), and as a result become migratory and invasive mesenchymal-like cells while acquiring cancer stem cell properties and therapy resistance. As EMT is involved in such a broad range of processes associated with malignant transformation, it has become an increasingly interesting target for the development of novel therapeutic strategies. Anti-EMT therapeutic strategies could potentially not only prevent the invasion and dissemination of cancer cells, and as such prevent the formation of metastatic lesions, but also attenuate cancer stemness and increase the effectiveness of more classical chemotherapeutics. In this review, we give an overview about the pros and cons of therapies targeting EMT and discuss some already existing candidate drug targets and high-throughput screening tools to identify novel anti-EMT compounds.

In-situ gelling xyloglucan formulations as 3D artificial niche for adipose stem cell spheroids

Three-dimensional spheroidal cell aggregates of adipose stem cells (SASCs) are a distinct upstream population of stem cells present in adipose tissue, with enhanced regeneration properties in vivo. The preservation of the 3D structure of the cells, from extraction to administration, can be a promising strategy to ensure optimal conditions for cell viability and maintenance of stemness potential. With this aim, an artificial niche was created by incorporating the spheroids into an injectable, in-situ gelling solution of partially degalactosylated xyloglucan (dXG) and an ad hoc formulated culture medium for the preservation of stem cell spheroid features. The evolution of the mechanical properties and the morphological structure of this artificial niche was investigated by small amplitude rheological analysis and scanning electron microscopy, respectively. Comparatively, systems produced with the same polymer and the typical culture medium (DMEM) used for adipose stem cell (ASC) growth in adherent cell culture conditions were also characterised. Cell viability of both SASCs and ASCs incorporated inside the hydrogel or seeded on top of the hydrogel were investigated as well as the preservation of SASC stemness conditions when embedded in the hydrogel.

Mesenchymal Stromal Cell-Produced Components of Extracellular Matrix Potentiate Multipotent Stem Cell Response to Differentiation Stimuli

Extracellular matrix (ECM) provides both structural support and dynamic microenvironment for cells regulating their behavior and fate. As a critical component of stem cell niche ECM maintains stem cells and activates their proliferation and differentiation under specific stimuli. Mesenchymal stem/stromal cells (MSCs) regulate tissue-specific stem cell functions locating in their immediate microenvironment and producing various bioactive factors, including ECM components. We evaluated the ability of MSC-produced ECM to restore stem and progenitor cell microenvironment in vitro and analyzed the possible mechanisms of its effects. Human MSC cell sheets were decellularized by different agents (detergents, enzymes, and apoptosis inductors) to select the optimized combination (CHAPS and DNAse I) based on the conservation of decellularized ECM (dECM) structure and effectiveness of DNA removal. Prepared dECM was non-immunogenic, supported MSC proliferation and formation of larger colonies in colony-forming unit-assay. Decellularized ECM effectively promoted MSC trilineage differentiation (adipogenic, osteogenic, and chondrogenic) compared to plastic or plastic covered by selected ECM components (collagen, fibronectin, laminin). Interestingly, dECM produced by human fibroblasts could not enhance MSC differentiation like MSC-produced dECM, indicating cell-specific functionality of dECM. We demonstrated the significant integrin contribution in dECM-cell interaction by blocking the stimulatory effects of dECM with RGD peptide and suggested the involvement of key intracellular signaling pathways activation (pERK/ERK and pFAK/FAK axes, pYAP/YAP and beta-catenin) in the observed processes based on the results of inhibitory analysis. Taken together, we suppose that MSC-produced dECM may mimic stem cell niche components in vitro and maintain multipotent progenitor cells to insure their effective response to external differentiating stimuli upon activation. The obtained data provide more insights into the possible role of MSC-produced ECM in stem and progenitor cell regulation within their niches. Our results are also useful for the developing of dECM-based cell-free products for regenerative medicine.

Next-Generation Biomaterials for Culture and Manipulation of Stem Cells

Stem cell fate decisions are informed by physical and chemical cues presented within and by the extracellular matrix. Despite the generally attributed importance of extracellular cues in governing self-renewal, differentiation, and collective behavior, knowledge gaps persist with regard to the individual, synergistic, and competing effects that specific physiochemical signals have on cell function. To better understand basic stem cell biology, as well as to expand opportunities in regenerative medicine and tissue engineering, a growing suite of customizable biomaterials has been developed. These next-generation cell culture materials offer user-defined biochemical and biomechanical properties, increasingly in a manner that can be controlled in time and 3D space. This review highlights recent innovations in this regard, focusing on advances to culture and maintain stemness, direct fate, and to detect stem cell function using biomaterial-based strategies.

Decellularized adipose matrix provides an inductive microenvironment for stem cells in tissue regeneration

Stem cells play a key role in tissue regeneration due to their self-renewal and multidirectional differentiation, which are continuously regulated by signals from the extracellular matrix (ECM) microenvironment. Therefore, the unique biological and physical characteristics of the ECM are important determinants of stem cell behavior. Although the acellular ECM of specific tissues and organs (such as the skin, heart, cartilage, and lung) can mimic the natural microenvironment required for stem cell differentiation, the lack of donor sources restricts their development. With the rapid development of adipose tissue engineering, decellularized adipose matrix (DAM) has attracted much attention due to its wide range of sources and good regeneration capacity. Protocols for DAM preparation involve various physical, chemical, and biological methods. Different combinations of these methods may have different impacts on the structure and composition of DAM, which in turn interfere with the growth and differentiation of stem cells. This is a narrative review about DAM. We summarize the methods for decellularizing and sterilizing adipose tissue, and the impact of these methods on the biological and physical properties of DAM. In addition, we also analyze the application of different forms of DAM with or without stem cells in tissue regeneration (such as adipose tissue), repair (such as wounds, cartilage, bone, and nerves), in vitro bionic systems, clinical trials, and other disease research.

Young at Heart: Combining Strategies to Rejuvenate Endogenous Mechanisms of Cardiac Repair

True cardiac regeneration of the injured heart has been broadly described in lower vertebrates by active replacement of lost cardiomyocytes to functionally and structurally restore the myocardial tissue. On the contrary, following severe injury (i.e., myocardial infarction) the adult mammalian heart is endowed with an impaired reparative response by means of meager wound healing program and detrimental remodeling, which can lead over time to cardiomyopathy and heart failure. Lately, a growing body of basic, translational and clinical studies have supported the therapeutic use of stem cells to provide myocardial regeneration, with the working hypothesis that stem cells delivered to the cardiac tissue could result into new cardiovascular cells to replenish the lost ones. Nevertheless, multiple independent evidences have demonstrated that injected stem cells are more likely to modulate the cardiac tissue via beneficial paracrine effects, which can enhance cardiac repair and reinstate the embryonic program and cell cycle activity of endogenous cardiac stromal cells and resident cardiomyocytes. Therefore, increasing interest has been addressed to the therapeutic profiling of the stem cell-derived secretome (namely the total of cell-secreted soluble factors), with specific attention to cell-released extracellular vesicles, including exosomes, carrying cardioprotective and regenerative RNA molecules. In addition, the use of cardiac decellularized extracellular matrix has been recently suggested as promising biomaterial to develop novel therapeutic strategies for myocardial repair, as either source of molecular cues for regeneration, biological scaffold for cardiac tissue engineering or biomaterial platform for the functional release of factors. In this review, we will specifically address the translational relevance of these two approaches with ad hoc interest in their feasibility to rejuvenate endogenous mechanisms of cardiac repair up to functional regeneration.

Comparison of percentage of CD90-positive cells and osteogenic differentiation potential between mesenchymal stem cells grown on dish and nonwoven fabric

Although nonwoven fabric (NWF) has been reported to be a candidate scaffold for the large-scale expansion of mesenchymal stem cells (MSCs), the quality of cells grown in NWF has not been well clarified. In this report, MSCs grown in an NWF disc for 3 weeks showed higher osteogenic differentiation potential and percentage of CD90 (+) cells than MSCs grown on the bottom surface of dish. The amount of the extracellular matrix (ECM) per unit surface area of fibers was larger than that on the bottom surface of the dish in the first 2 weeks of culture. The osteogenic differentiation potential of MSCs inoculated onto cell-free ECM increased with increasing amount of ECM. The higher percentage of CD90 (+) cells and osteogenic differentiation potential of cells grown in an NWF disc than of cells grown on a dish might, at least in part, be due to the higher amount of ECM.

In Vitro Evaluation of a Novel Osteo-Inductive Scaffold for Osteogenic Differentiation of Bone-Marrow Mesenchymal Stem Cells

BACKGROUND

Demineralized bone matrices (DBMs) were demonstrated to be a promising candidate for bone regeneration by previous studies. However, the limited osteoinductivity of DBMs was insufficient for a better repairing of bone defect. Osteoblasts (OBs), the major cellular component of bone tissues, play an important role in the formation of new bone. The extracellular matrix (ECM) of OB is one of the main components of bone formation niche.

OBJECTIVE

To combine the DBMs with the ECM of OBs to construct a novel scaffold that could be used for bone reconstruction.

METHODS

In this study, OBs were cultured on the surface of DBMs for 10 days and removed by Triton X-100 and ammonium hydroxide to prepare the OBs-ECM-DBMs (OEDBMs). A series of material features such as residues of OBs and ECM, cytotoxity, and osteoinductive capability of OEDBMs were evaluated.

RESULTS

Low cell residues and low content of DNA were observed in OEDBMs. Compared with DBMs, OEDBMs possessed more bone tissues organic matrix proteins, such as osteocalcin, osteopontin, and collagen I. Rat bone marrow mesenchymal stem cells (rBMSCs) presented a good viability when cultured on both 2 materials. The significant upregulations of osteogenic genes and proteins of rBMSCs were observed in OEDBMs group compared with DBMs group.

CONCLUSION

Taken together, these findings suggested that the OB-secreted ECM may be qualified as an ideal modification method for enhancing the performance of engineered bone scaffold.

Decellularized and solubilized pancreatic stroma promotes the in vitro proliferation, migration and differentiation of BMSCs into IPCs

Bone marrow-derived mesenchymal stem cells (BMSCs) have the ability to differentiate into insulin-producing cells (IPCs). Bio-scaffolds derived from decellularized organs can act as a carrier for seed cells and may have broad applications in regenerative medicine. This study investigated the effect of native pancreatic stroma obtained from decellularized pancreas on the proliferation, migration and differentiation of BMSCs into IPCs, and explored the potential underlying molecular mechanism. The decellularized pancreas bio-scaffold was obtained by perfusion with Triton X-100/ammonium hydroxide, followed by digestion with a mixture of pepsin and hydrochloric acid to prepare the stroma solution. Islet-like cells were differentiated from BMSCs by a three-step induction method. The differences on the cytological behavior with or without stroma were evaluated by morphological observation, insulin release assay, qRT-PCR assay and western blot analysis. Our results showed that, stroma derived from decellularized pancreas could promote the proliferation and migration of BMSCs. Furthermore, the formation of IPCs could also be promoted, which possessed similar morphology to endogenous islets. During the induced differentiation process, the presence of stroma significantly increased the expression of insulin 1, insulin 2 and Pdx-1, as well as insulin release. This was accompanied by an increase in the phosphorylation of Akt and ERK in third stage cell clusters, which was prevented by the addition of the inhibitors PD98059 and LY294002, respectively. In summary, decellularized pancreatic stroma could promote the proliferation, migration and differentiation of BMSCs into IPCs, and this involved the activation of Akt and ERK signal pathways.

Quantified forces between HepG2 hepatocarcinoma and WA07 pluripotent stem cells with natural biomaterials correlate with in vitro cell behavior

In vitro cell culture or tissue models that mimic in vivo cellular response have potential in tissue engineering and regenerative medicine, and are a more economical and accurate option for drug toxicity tests than animal experimentation. The design of in vivo-like cell culture models should take into account how the cells interact with the surrounding materials and how these interactions affect the cell behavior. Cell-material interactions are furthermore important in cancer metastasis and tumor progression, so deeper understanding of them can support the development of new cancer treatments. Herein, the colloidal probe microscopy technique was used to quantify the interactions of two cell lines (human pluripotent stem cell line WA07 and human hepatocellular carcinoma cell line HepG2) with natural, xeno-free biomaterials of different chemistry, morphology, and origin. Key components of extracellular matrices -human collagens I and IV, and human recombinant laminin-521-, as well as wood-derived, cellulose nanofibrils -with evidenced potential for 3D cell culture and tissue engineering- were analysed. Both strength of adhesion and force curve profiles depended on biomaterial nature and cell characteristics. The successful growth of the cells on a particular biomaterial required cell-biomaterial adhesion energies above 0.23 nJ/m. The information obtained in this work supports the development of new materials or hybrid scaffolds with tuned cell adhesion properties for tissue engineering, and provides a better understanding of the interactions of normal and cancerous cells with biomaterials in the human body.

Structural characterization of four different naturally occurring porcine collagen membranes suitable for medical applications

Collagen is the main structural element of connective tissues, and its favorable properties make it an ideal biomaterial for regenerative medicine. In dental medicine, collagen barrier membranes fabricated from naturally occurring tissues are used for guided bone regeneration. Since the morphological characteristics of collagen membranes play a crucial role in their mechanical properties and affect the cellular behavior at the defect site, in-depth knowledge of the structure is key. As a base for the development of novel collagen membranes, an extensive morphological analysis of four porcine membranes, including centrum tendineum, pericardium, plica venae cavae and small intestinal submucosa, was performed. Native membranes were analyzed in terms of their thickness. Second harmonic generation and two-photon excitation microscopy of the native membranes showed the 3D architecture of the collagen and elastic fibers, as well as a volumetric index of these two membrane components. The surface morphology, fiber arrangement, collagen fibril diameter and D-periodicity of decellularized membranes were investigated by scanning electron microscopy. All the membrane types showed significant differences in thickness. In general, undulating collagen fibers were arranged in stacked layers, which were parallel to the membrane surface. Multiphoton microscopy revealed a conspicuous superficial elastic fiber network, while the elastin content in deeper layers varied. The elastin/collagen volumetric index was very similar in the investigated membranes and indicated that the collagen content was clearly higher than the elastin content. The surface of both the pericardium and plica venae cavae and the cranial surface of the centrum tendineum revealed a smooth, tightly arranged and crumpled morphology. On the caudal face of the centrum tendineum, a compact collagen arrangement was interrupted by clusters of circular discontinuities. In contrast, both surfaces of the small intestinal submucosa were fibrous, fuzzy and irregular. All the membranes consisted of largely uniform fibrils displaying the characteristic D-banding. This study reveals similarities and relevant differences among the investigated porcine membranes, suggesting that each membrane represents a unique biomaterial suitable for specific applications.

Enrichment of cancer stem cells by agarose multi-well dishes and 3D spheroid culture

As the theory of cancer stem cells (CSCs) is maturing, CSC-targeted therapy is emerging as an important therapeutic strategy and seeking the ideal method for rapid enrichment and purification of CSCs has become crucial. So far, based on the known CSC phenotypes and biological characteristics, the methods for enrichment CSCs mainly include low adhesion culture, low oxygen culture, chemotherapy drug stimulation and side population (SP) sorting but these methods cannot realize quick enrichment of the desired CSCs. Herein, we adopt a novel method that efficiently enriches a certain amount of CSCs through agarose multi-well dishes using rubber micro-molds to make cancer cells into cell spheroids (3D). These 3D cancer cell spheroids in the proportions of expression of CSC biomarkers (single stain of CD44, CD44v6 and CD133 or double stain of both CD44 and CD133) were significantly higher than those of the conventional adherent culture (2D) using flow cytometry analysis. In addition, the expression levels of stemness transcription factors such as OCT4, NANOG and SOX2 in 3D were also significantly higher than that in 2D through Western blot (WB) and quantitative polymerase chain reaction (qPCR) assays. In addition, the CSCs in 3D could form colonies with different sizes in soft agar. In conclusion, we developed a new method to enrich some kinds of CSCs, which might be a benefit for future CSC-targeted therapy studies and anti-CSC drug screening applications.

Type I collagen induces mesenchymal cell differentiation into myofibroblasts through YAP-induced TGF-β1 activation

In organ fibrosis, mechanical stress and transforming growth factor beta-1 (TGF-β1) promote differentiation into myofibroblast from mesenchymal cells, leading to extracellular matrix (ECM) remodeling or active synthesis, deposition or degradation of ECM components. A major component of ECM, type I collagen (col I) triple helical molecules assemble into fibrils or are denatured to gelatin without triple-helicity in remodeling. However, whether changes of ECM components in remodeling have influence on mesenchymal cell differentiation remains elusive. This study adopted three states of collagen I existing in ECM remodeling: molecular collagen, fibrillar collagen and gelatin to see what are characteristics in the effects on two cell lines of mesenchymal origin, murine 3T3-L1 embryonic fibroblast and murine C2C12 myoblasts. The results showed that all three forms of collagen I were capable of inducing these two cells to differentiate into myofibroblasts characterized by increased expression of alpha-smooth muscle actin (α-SMA) mRNA. The expression of α-SMA is positively regulated by TGF-β1. Nuclear translocation of Yes-associated protein (YAP) is involved in this process. Focal adhesion kinase (FAK) is activated in the cells cultured on molecular collagen-coated plates, contributing to YAP activation. On the other hand, in the cells cultured on fibrillar collagen gel or gelatin-coated plates, oxidative stress but not FAK induce YAP activation. In conclusion, the three physicochemically distinct forms of col I induce the differentiation of mesenchymal cells into myofibroblasts through different pathways.

Direct Control of Stem Cell Behavior Using Biomaterials and Genetic Factors

Stem cells have recently emerged as an important candidate for cell therapy. However, some major limitations still exist such as a small quantity of cell supply, senescence, and insufficient differentiation efficiency. Therefore, there is an unmet need to control stem cell behavior for better clinical performance. Since native microenvironment factors including stem cell niche, genetic factors, and growth factors direct stem cell fate cooperatively, user-specified in vitro settings are required to understand the regulatory roles and effects of each factor, thereby applying the factors for improved cell therapy. Among others, various types of biomaterials and transfection method have been employed as key tools for development of the in vitro settings. This review focuses on the current strategies to improve stemness maintenance, direct differentiation, and reprogramming using biomaterials and genetic factors without any aids from additional biochemicals and growth factors.

Transferable Matrixes Produced from Decellularized Extracellular Matrix Promote Proliferation and Osteogenic Differentiation of Mesenchymal Stem Cells and Facilitate Scale-Up

Decellularized extracellular matrixes (dECM) derived from mesenchymal stem cell (MSC) cultures have recently emerged as cell culture substrates that improve the proliferation, differentiation, and maintenance of MSC phenotype during ex vivo expansion. These biomaterials have considerable potential in the fields of stem cell biology, tissue engineering, and regenerative medicine. Processing the dECMs into concentrated solutions of biomolecules that enable the useful properties of the native dECM to be transferred to a new surface via a simple adsorption step would greatly increase the usefulness and impact of this technology. The development of such solutions, hereafter referred to as transferable matrixes, is the focus of this article. In this work, we produced transferable matrixes from dECM derived from two human placental MSC cell lines (DMSC23 and CMSC29) using pepsin digestion (P-ECM), urea extraction (U-ECM), and mechanical homogenization in acetic acid (AA-ECM). Native dECMs improved primary DMSC proliferation as well as osteogenic and adipogenic differentiation, compared with traditional expansion procedures. Interestingly, tissue culture plastic coated with P-ECM was able to replicate the proliferative effects of native dECM, while U-ECM was able to replicate osteogenic differentiation. These data illustrate the feasibility of producing dECM-derived transferable matrixes that replicate key features of the native matrixes and show that different processing techniques produce transferable matrixes with varying bioactivities. Additionally, these transferable matrixes are able to coat 1.3-5.2 times the surface area covered by the native dECM, facilitating scale-up of this technology.

Cell-Sheet-Derived ECM Coatings and Their Effects on BMSCs Responses

Extracellular matrix (ECM) provides a dynamic and complex environment to determine the fate of stem cells. In this work, light harvested cell sheets were treated with paraformaldehyde or ethanol, which eventually become ECM. Such ECM was then immobilized on titanium substrates via polydopamine chemistry. Their effects on bone marrow mesenchymal stromal cells (BMSCs) behaviors were investigated. It was found that paraformaldehyde-treated ECM coating (PT-ECM) showed a well-maintained microstructure, whereas that of ethanol-treated (ET-ECM) was completely changed. As a result, different amide structures and distributions of ECM components, such as laminin and collagen I, were exhibited. Alkaline phosphatase activity, osteocalcin secretion, related gene expression, and mineral deposition were evaluated for BMSCs cultured on both ECM coatings. PT-ECM was demonstrated to promote osteogenic differentiation much more efficiently than that of ET-ECM. That is ascribed to the preservation of native ECM milieu of PT-ECM. Such ECM acquirement and immobilization method could establish surfaces being able to direct stem cell responses on various materials. That shows promising potential in bone tissue engineering and other related biomedical applications.

Restoring the biophysical properties of decellularized patches through recellularization

Various extracellular matrix (ECM) scaffolds, isolated through decellularization, were suggested as ideal biomimetic materials for 'Functional tissue engineering' (FTE). The decellularization process comprises a compromise between damaging and preserving the ultrastructure and composition of ECM-previously shown to affect cell survival, proliferation, migration, organization, differentiation and maturation. Inversely, the effects of cells on the ECM constructs' biophysical properties, under physiological-like conditions, remain still largely unknown. We hypothesized that by re-cellularizing porcine cardiac ECM (pcECM, as a model scaffold) some of the original biophysical properties of the myocardial tissue can be restored, which are related to the scaffold's surface and the bulk modifications consequent to cellularization. We performed a systematic biophysical assessment of pcECM scaffolds seeded with human mesenchymal stem cells (MSCs), a common multipotent cell source in cardiac regenerative medicine. We report a new type of FTE study in which cell interactions with a composite-scaffold were evaluated from the perspective of their contribution to the biophysical properties of the construct surface (FTIR, WETSEM™) and bulk (DSC, TGA, and mechanical testing). The results obtained were compared with acellular pcECM and native ventricular tissue serving as negative and positive controls, respectively. MSC recellularization resulted in an inter-fiber plasticization effect, increased protein density, masking of acylated glycosaminoglycans (GAGs) and active pcECM remodelling which further stabilized the reseeded construct and increased its denaturation resistance. The systematic approach presented herein, therefore, identifies cells as "biological plasticizers" and yields important methodologies, understanding, and data serving both as a reference as well as possible 'design criteria' for future studies in FTE.

Mesenchymal stem cell-derived extracellular matrix enhances chondrogenic phenotype of and cartilage formation by encapsulated chondrocytes in vitro and in vivo

Mesenchymal stem cell derived extracellular matrix (MSC-ECM) is a natural biomaterial with robust bioactivity and good biocompatibility, and has been studied as a scaffold for tissue engineering. In this investigation, we tested the applicability of using decellularized human bone marrow derived MSC-ECM (hBMSC-ECM) as a culture substrate for chondrocyte expansion in vitro, as well as a scaffold for chondrocyte-based cartilage repair. hBMSC-ECM deposited by hBMSCs cultured on tissue culture plastic (TCP) was harvested, and then subjected to a decellularization process to remove hBMSCs. Compared with chondrocytes grown on TCP, chondrocytes seeded onto hBMSC-ECM exhibited significantly increased proliferation rate, and maintained better chondrocytic phenotype than TCP group. After being expanded to the same cell number and placed in high-density micromass cultures, chondrocytes from the ECM group showed better chondrogenic differentiation profile than those from the TCP group. To test cartilage formation ability, composites of hBMSC-ECM impregnated with chondrocytes were subjected to brief trypsin treatment to allow cell-mediated contraction, and folded to form 3-dimensional chondrocyte-impregnated hBMSC-ECM (Cell/ECM constructs). Upon culture in vitro in chondrogenic medium for 21 days, robust cartilage formation was observed in the Cell/ECM constructs. Similarly prepared Cell/ECM constructs were tested in vivo by subcutaneous implantation into SCID mice. Prominent cartilage formation was observed in the implanted Cell/ECM constructs 14 days post-implantation, with higher sGAG deposition compared to controls consisting of chondrocyte cell sheets. Taken together, these findings demonstrate that hBMSC-ECM is a superior culture substrate for chondrocyte expansion and a bioactive matrix potentially applicable for cartilage regeneration in vivo.

STATEMENT OF SIGNIFICANCE

Current cell-based treatments for focal cartilage defects face challenges, including chondrocyte dedifferentiation, need for xenogenic scaffolds, and suboptimal cartilage formation. We present here a novel technique that utilizes adult stem cell-derived extracellular matrix, as a culture substrate and/or encapsulation scaffold for human adult chondrocytes, for the repair of cartilage defects. Chondrocytes cultured in stem cell-derived matrix showed higher proliferation, better chondrocytic phenotype, and improved redifferentiation ability upon in vitro culture expansion. Most importantly, 3-dimensional constructs formed from chondrocytes folded within stem cell matrix manifested excellent cartilage formation both in vitro and in vivo. These findings demonstrate the suitability of stem cell-derived extracellular matrix as a culture substrate for chondrocyte expansion as well as a candidate bioactive matrix for cartilage regeneration.

Natural Sources of Extracellular Matrix for Cardiac Repair

Tissue engineering and regenerative medicine have adopted the use of extracellular matrix (ECM) as a cell delivery device and bioactive regenerative agent. To this end, many ECMs have been investigated for cardiac tissue engineering and regenerative medicine applications with variable success. Many sources of natural ECMs have been tested for cardiac applications. Typically, natural ECMs have been made from decellularized organs or tissues and processed into either sheets or injectable hydrogels. This chapter will review natural sources of ECM materials that have been tested as therapeutic agents in models of heart failure.

Directing osteogenic differentiation of BMSCs by cell-secreted decellularized extracellular matrixes from different cell types

Cell-secreted decellularized extracellular matrixes (D-ECM) are promising for conferring bioactivity and directing cell fate to facilitate tissue regeneration.

Hyperbranched poly(ϵ-lysine) substrate presenting the laminin sequence YIGSR induces the formation of spheroids in adult bone marrow stem cells

Unlike the fibroblast-like cells formed upon monolayer culture of human mesenchymal stem cells, the natural stem cell niche of the bone marrow and other types of tissues favours the formation of 3-dimensional (3D) cell clusters. The structuring and biological activity of these clusters are regulated by the contacts established by cells with both the basement membrane and neighbour cells and results in their asymmetric division and the consequent maintenance of both a stem population and a committed progeny. The present work demonstrates the potential of a synthetic substrate to mimic the stem cell niche in vitro. The side amino groups of a linear Poly-L-lysine were modified with hyperbranched poly-(ϵ-lysine) peptides, named as dendrons, tethered with the laminin-mimicking sequence, YIGSR. These dendrons presented the YIGSR sequence at the uppermost molecular branching ensuring a controlled spacing of the bioligand. When used to coat the surface of tissue culture plates in a serum-free in vitro cell culture system, the substrate was able to mimic the most relevant features of the basement membrane of the stem cell niche, i.e. the mesh structure of Collagen Type IV and the availability of laminin bioligands relevant to integrin biorecognition. The substrate biomimetic properties were tested for their ability to support the formation of human bone marrow mesenchymal stem cells (hMSCs) 3D spheroids similar to those observed in the natural stem cell niches and their ability to maintain stem cell pluripotency markers. These features were related to the substrate-specific expression and localisation of (i) cell adhesion receptors (i.e. β-integrin and N-cadherin), (ii) transcription factors of pluripotency markers and cytoskeleton protein and (iii) regulators of cell migration throughout cell culture passages 2 to 4. The results clearly demonstrate the formation of 3D spheroids starting from the asymmetric division of substrate-adhering spread cells, the clustering of relevant integrins and the expression of specific intracellular pathways controlling cytoskeleton formation suggesting their potential use as a substrate for the handling of stem cells prior to transplantation procedures.

Effects of Human Fibroblast-Derived Extracellular Matrix on Mesenchymal Stem Cells

Stem cell fate is largely determined by the microenvironment called niche. The extracellular matrix (ECM), as a key component in the niche, is responsible for maintaining structural stability and regulating cell proliferation, differentiation, migration and other cellular activities. Each tissue has a unique ECM composition for its needs. Here we investigated the effect of a bioengineered human dermal fibroblast-derived ECM (hECM) on the regulation of human mesenchymal stem cell (hMSC) proliferation and multilineage differentiation. Human MSCs were maintained on hECM for two passages followed by the analysis of mRNA expression levels of potency- and lineage-specific markers to determine the capacity of MSC stemness and differentiation, respectively. Mesenchymal stem cells pre-cultured with or without hECM were then induced and analyzed for osteogenesis, adipogenesis and chondrogenesis. Our results showed that compared to MSCs maintained on control culture plates without hECM coating, cells on hECM-coated plates proliferated more rapidly with a higher percentage of cells in S phase of the cell cycle, resulting in an increase in the CD90⁺/CD105⁺/CD73⁺/CD45^- subpopulation. In addition, hECM downregulated osteogenesis and adipogenesis of hMSCs but significantly upregulated chondrogenesis with increased production of collagen type 2. In sum, our findings suggest that hECM may be used to culture hMSCs for the application of cartilage tissue engineering.

Decellularized matrix of adipose-derived mesenchymal stromal cells enhanced retinal progenitor cell proliferation via the Akt/Erk pathway and neuronal differentiation

BACKGROUND AIMS

Retinal progenitor cells (RPCs) are a promising cell therapy treatment for retinal degenerative diseases. However, problems with limited proliferation ability and differentiation preference toward glia rather than neurons restrict the clinical application of these RPCs. The extracellular matrix (ECM) has been recognized to provide an appropriate microenvironment to support stem cell adhesion and direct cell behaviors, such as self-renewal and differentiation.

METHODS

In this study, decellularized matrix of adipose-derived mesenchymal stromal cells (DMA) was manufactured using a chemical agent method (0.5% ammonium hydroxide Triton + 20 mmol/L NH4OH) in combination with a biological agent method (DNase solution), and the resulting DMA were evaluated by scanning electron microscopy (SEM) and immunocytochemistry. The effect of DMA on RPC proliferation and differentiation was evaluated by quantitative polymerase chain reaction, Western blot and immunocytochemistry analysis.

RESULTS

DMA was successfully fabricated, as demonstrated by SEM and immunocytochemistry. Compared with tissue culture plates, DMA may effectively enhance the proliferation of RPCs by activating Akt and Erk phosphorylation; when the two pathways were blocked, the promoting effect was reversed. Moreover, DMA promoted the differentiation of RPCs toward retinal neurons, especially rhodopsin- and recoverin-positive photoreceptors, which is the most interesting class of cells for retinal degeneration treatment.

CONCLUSIONS

These results indicate that DMA has important roles in governing RPC proliferation and differentiation and may contribute to the application of RPCs in treating retinal degenerative diseases.

Xeno-Free Strategies for Safe Human Mesenchymal Stem/Stromal Cell Expansion: Supplements and Coatings

Human mesenchymal stem/stromal cells (hMSCs) have generated great interest in regenerative medicine mainly due to their multidifferentiation potential and immunomodulatory role. Although hMSC can be obtained from different tissues, the number of available cells is always low for clinical applications, thus requiring in vitro expansion. Most of the current protocols for hMSC expansion make use of fetal bovine serum (FBS) as a nutrient-rich supplement. However, regulatory guidelines encourage novel xeno-free alternatives to define safer and standardized protocols for hMSC expansion that preserve their intrinsic therapeutic potential. Since hMSCs are adherent cells, the attachment surface and cell-adhesive components also play a crucial role on their successful expansion. This review focuses on the advantages/disadvantages of FBS-free media and surfaces/coatings that avoid the use of animal serum, overcoming ethical issues and improving the expansion of hMSC for clinical applications in a safe and reproducible way.

Native and solubilized decellularized extracellular matrix: A critical assessment of their potential for improving the expansion of mesenchymal stem cells

Capturing the promise of mesenchymal stem cell (MSC)-based treatments is currently limited by inefficient production of cells needed for clinical therapies. During conventional ex vivo expansion, a large portion of MSCs lose the properties that make them attractive for use in cell therapies. Decellularized extracellular matrix (dECM) has recently emerged as a promising substrate for the improved expansion of MSCs. MSCs cultured on these surfaces exhibit improved proliferation capacity, maintenance of phenotype, and increased differentiation potential. Additionally, these dECMs can be solubilized and used to coat new cell culture surfaces, imparting key biological properties of the native matrices to other surfaces such as tissue engineering scaffolds. Although this technology is still developing, there is potential for an impact in the fields of MSC biology, biomaterials, tissue engineering, and therapeutics. In this article, we review the role of dECM in MSC expansion by first detailing the decellularization methods that have been used to produce the dECM substrates; discussing the shortcomings of current decellularization methods; describing the improved MSC characteristics obtained when the cells are cultured on these surfaces; and considering the effect of the passage number, age of donor, and dECM preparation method on the quality of the dECM. Finally we describe the critical roadblocks that must be addressed before this technology can fulfil its potential, including elucidating the mechanism by which the dECMs improve the expansion of primary MSCs and the identification of a readily available source of dECM.

STATEMENT OF SIGNIFICANCE

Current mesenchymal stem cell (MSC) culture methods result in premature cellular senescence or loss of differentiation potential. This creates a major bottleneck in their clinical application, as prolonged expansion is necessary to achieve clinically relevant numbers of cells. Recently, decellularized extracellular matrix (dECM) produced by primary MSC has emerged as an attractive substrate for the improved expansion of MSC; cells cultured on these surfaces retain their desired stem cell characteristics for prolonged times during culture. This review article describes the inception and development of this dECM-based technology, points out existing challenges that must be addressed, and suggests future directions of research. To our knowledge, this is the first review written on the use of dECM for improved mesenchymal stem cell expansion.

Decellularized extracellular matrices produced from immortal cell lines derived from different parts of the placenta support primary mesenchymal stem cell expansion

Mesenchymal stem/stromal cells (MSCs) exhibit undesired phenotypic changes during ex vivo expansion, limiting production of the large quantities of high quality primary MSCs needed for both basic research and cell therapies. Primary MSCs retain many desired MSC properties including proliferative capacity and differentiation potential when expanded on decellularized extracellular matrix (dECM) prepared from primary MSCs. However, the need to use low passage number primary MSCs (passage 3 or lower) to produce the dECM drastically limits the utility and impact of this technology. Here, we report that primary MSCs expanded on dECM prepared from high passage number (passage 25) human telomerase reverse transcriptase (hTERT) transduced immortal MSC cell lines also exhibit increased proliferation and osteogenic differentiation. Two hTERT-transduced placenta-derived MSC cell lines, CMSC29 and DMSC23 [derived from placental chorionic villi (CMSCs) and decidua basalis (DMSCs), respectively], were used to prepare dECM-coated substrates. These dECM substrates showed structural and biochemical differences. Primary DMSCs cultured on dECM-DMSC23 showed a three-fold increase in cell number after 14 days expansion in culture and increased osteogenic differentiation compared with controls. Primary CMSCs cultured on the dECM-DMSC23 exhibited a two-fold increase in cell number and increased osteogenic differentiation. We conclude that immortal MSC cell lines derived from different parts of the placenta produce dECM with varying abilities for supporting increased primary MSC expansion while maintaining important primary MSC properties. Additionally, this is the first demonstration of using high passage number cells to produce dECM that can promote primary MSC expansion, and this advancement greatly increases the feasibility and applicability of dECM-based technologies.

Decellularized extracellular matrix of human umbilical vein endothelial cells promotes endothelial differentiation of stem cells from exfoliated deciduous teeth

Dental stem cells can serve as a potential source of functional endothelial cells for tissue engineering applications, but the endothelial-lineage differentiation efficiency is rather low even with growth factors and mechanical stimuli, which greatly limits their clinical applications. This is partly due to the deficiency of standard two-dimensional (2-D) culture systems, which is unable to recapitulate the three-dimensional (3-D) in vivo milieu that is rich in extracellular matrix. Hence, we extracted decellularized extracellular matrix from human umbilical vein endothelial cells (HUVECs-DECM) to provide a bioactive substratum conducive to the endothelial differentiation of dental stem cells. Compared to cells plated on tissue culture polystyrene (TCP), stem cells from exfoliated deciduous teeth (SHED) cultured on the HUVECs-DECM demonstrated more regular arrangement and elongated morphology. HUVECs-DECM significantly enhanced the rapid adhesion and proliferation rates of SHED, as demonstrated by WST-8 assay and immunocytochemistry indicating higher expression levels of vinculin by newly adherent SHED on HUVECs-DECM versus TCP. In addition, there was twofold to fivefold higher mRNA expression levels of endothelial-specific markers CD31 and VEGFR-2 in SHED after seven days of culture on DECM versus TCP. Functional testing with in vitro matrigel angiogenesis assay identified more capillary-like structure formation with significantly higher tubule length in SHED induced by DECM versus TCP. Hence, the results of this study provide a better understanding of the unique characteristics of cell-specific ECM and demonstrated the potential use of HUVECs-DECM as a culture substratum conducive for stimulating the endothelial differentiation of SHED for therapeutic angiogenic applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1083-1093, 2017.

Heterogeneous Differentiation of Human Mesenchymal Stem Cells in 3D Extracellular Matrix Composites

Extracellular matrix (ECM) proteins are structural elements of tissue and also potent signaling molecules. Previously, our laboratory showed that ECM of 2D coatings can trigger differentiation of bone marrow-derived mesenchymal stem cells (MSCs) into mesodermal lineages in an ECM-specific manner over 14 days, in some cases comparable to chemical induction. To test whether a similar effect was possible in a 3D, tissue-like environment, we designed a synthetic-natural biomaterial composite. The composite can present whole-molecule ECM proteins to cells, even those that do not spontaneously form hydrogels ex vivo, in 3D. To this end, we entrapped collagen type I, laminin-111, or fibronectin in ECM composites with MSCs and directly compared markers of mesodermal differentiation including cardiomyogenic (ACTC1), osteogenic (SPP1), adipogenic (PPARG), and chondrogenic (SOX9) in 2D versus 3D. We found the 3D condition largely mimicked the 2D condition such that the addition of type I collagen was the most potent inducer of differentiation to all lineages tested. One notable difference between 2D and 3D was pronounced adipogenic differentiation in 3D especially in the presence of exogenous collagen type I. In particular, PPARG gene expression was significantly increased ∼16-fold relative to chemical induction, in 3D and not in 2D. Unexpectedly, 3D engagement of ECM proteins also altered immunomodulatory function of MSCs in that expression of IL-6 gene was elevated relative to basal levels in 2D. In fact, levels of IL-6 gene expression in 3D composites containing exogenously supplied collagen type I or fibronectin were statistically similar to levels attained in 2D with tumor necrosis factor-α (TNF-α) stimulation and these levels were sustained over a 2-week period. Thus, this novel biomaterial platform allowed us to compare the biochemical impact of whole-molecule ECM proteins in 2D versus 3D indicating enhanced adipogenic differentiation and IL-6 expression of MSC in the 3D context. Exploiting the biochemical impact of ECM proteins on MSC differentiation and immunomodulation could augment the therapeutic utility of MSCs.

Effects of decellularized matrices derived from periodontal ligament stem cells and SHED on the adhesion, proliferation and osteogenic differentiation of human dental pulp stem cells in vitro

A major bottleneck to the therapeutic applications of dental pulp stem cells (DPSC) are their limited proliferative capacity ex vivo and tendency to undergo senescence. This may be partly due to the sub-optimal in vitro culture milieu, which could be improved by an appropriate extracellular matrix substratum. This study therefore examined decellularized matrix (DECM) from stem cells derived from human exfoliated deciduous teeth (SHED) and periodontal ligament stem cells (PDLSC), as potential substrata for DPSC culture. Both SHED-DECM and PDLSC-DECM promoted rapid adhesion and spreading of newly-seeded DPSC compared to bare polystyrene (TCPS), with vinculin immunocytochemistry showing expression of more focal adhesions by newly-adherent DPSC cultured on DECM versus TCPS. Culture of DPSC on SHED-DECM and PDLSC-DECM yielded higher proliferation of cell numbers compared to TCPS. The qRT-PCR data showed significantly higher expression of nestin by DPSC cultured on DECM versus the TCPS control. Osteogenic differentiation of DPSC was enhanced by culturing on PDLSC-DECM and SHED-DECM versus TCPS, as demonstrated by alizarin red S staining for mineralized calcium deposition, alkaline phosphatase assay and qRT-PCR analysis of key osteogenic marker expression. Hence, both SHED-DECM and PDLSC-DECM could enhance the ex vivo culture of DPSC under both non-inducing and osteogenic-inducing conditions.

Generating and characterizing the mechanical properties of cell-derived matrices using atomic force microscopy

Mechanical interaction between cells and their surrounding extracellular matrix (ECM) controls key processes such as proliferation, differentiation and motility. For many years, two-dimensional (2D) models were used to better understand the interactions between cells and their surrounding ECM. More recently, variation of the mechanical properties of tissues has been reported to play a major role in physiological and pathological scenarios such as cancer progression. The 3D architecture of the ECM finely tunes cellular behavior to perform physiologically relevant tasks. Technical limitations prevented scientists from obtaining accurate assessment of the mechanical properties of physiologically realistic matrices. There is therefore a need for combining the production of high-quality cell-derived 3D matrices (CDMs) and the characterization of their topographical and mechanical properties. Here, we describe methods that allow to accurately measure the young modulus of matrices produced by various cellular types. In the first part, we will describe and review several protocols for generating CDMs matrices from endothelial, epithelial, fibroblastic, muscle and mesenchymal stem cells. We will discuss tools allowing the characterization of the topographical details as well as of the protein content of such CDMs. In a second part, we will report the methodologies that can be used, based on atomic force microscopy, to accurately evaluate the stiffness properties of the CDMs through the quantification of their young modulus. Altogether, such methodologies allow characterizing the stiffness and topography of matrices deposited by the cells, which is key for the understanding of cellular behavior in physiological conditions.