Expansion on extracellular matrix deposited by human bone marrow stromal cells facilitates stem cell proliferation and tissue-specific lineage potential

Decellularized extracellular matrix-decorated 3D nanofiber scaffolds enhance cellular responses and tissue regeneration

The use of decellularized extracellular matrix products in tissue regeneration is quite alluring yet practically challenging due to the limitations of its availability, harsh processing techniques, and host rejection. Scaffolds obtained by either incorporating extracellular matrix (ECM) material or coating the surface can resolve these challenges to some extent. However, these scaffolds lack the complex 3D network formed by proteins and growth factors observed in natural ECM. This study introduces an approach utilizing 3D nanofiber scaffolds decorated with dECM to enhance cellular responses and promote tissue regeneration. Notably, the dECM can be customized according to specific cellular requirements, offering a tailored environment for enhanced therapeutic outcomes. Two types of 3D expanded scaffolds, namely radially aligned scaffolds (RAS) and laterally expanded scaffolds (LES) fabricated by the gas-foaming expansion were utilized. To demonstrate the proof-of-concept, human dermal fibroblasts (HDFs) seeded on these scaffolds for up to 8 weeks, resulted in uniform and highly aligned cells which deposited ECM on the scaffolds. These cellular components were then removed from the scaffolds through decellularization (e.g., SDS treatment and freeze-thaw cycles). The dECM-decorated 3D expanded nanofiber scaffolds can direct and support cell alignment and proliferation along the underlying fibers upon recellularization. An in vitro inflammation assay indicates that dECM-decorated LES induces a lower immune response than dECM-decorated RAS. Further, subcutaneous implantation of dECM-decorated RAS and LES shows higher cell infiltration and angiogenesis within 7 and 14 days than RAS and LES without dECM decoration. Taken together, dECM-decorated 3D expanded nanofiber scaffolds hold great potential in tissue regeneration and tissue modeling. STATEMENT OF SIGNIFICANCE: Decellularized ECM scaffolds have attained widespread attention in biomedical applications due to their intricate 3D framework of proteins and growth factors. Mimicking such a complicated architecture is a clinical challenge. In this study, we developed natural ECM-decorated 3D electrospun nanofiber scaffolds with controlled alignments to mimic human tissue. Fibroblasts were cultured on these scaffolds for 8 weeks to deposit natural ECM and decellularized by either freeze-thawing or detergent to obtain decellularized ECM scaffolds. These scaffolds were tested in both in-vitro and in-vivo conditions. They displayed higher cellular attributes with lower immune response making them a good grafting tool in tissue regeneration.

MSCs-Derived Decellularised Matrix: Cellular Responses and Regenerative Dentistry

The decellularised extracellular matrix (dECM) of in vitro cell culture is a naturally derived biomaterial formed by the removal of cellular components. The compositions of molecules in the extracellular matrix (ECM) differ depending on various factors, including the culture conditions. Cell-derived ECM provides a 3-dimensional structure that has a complex influence on cell signalling, which in turn affects cell survival and differentiation. This review describes the effects of dECM derived from mesenchymal stem cells (MSCs) on cell responses, including cell migration, cell proliferation, and cell differentiation in vitro. Published articles were searched in the PubMed databases in 2005 to 2022, with assigned keywords (MSCs and decellularisation and cell culture). The 41 articles were reviewed, with the following criteria. (1) ECM was produced exclusively from MSCs; (2) decellularisation processes were performed; and (3) the dECM production was discussed in terms of culture systems and specific supplementations that are suitable for creating the dECM biomaterials. The dECM derived from MSCs supports cell adhesion, enhances cell proliferation, and promotes cell differentiation. Importantly, dECM derived from dental MSCs shows promise in regenerative dentistry applications. Therefore, the literature strongly supports cell-based dECMs as a promising option for innovative tissue engineering approaches for regenerative medicine.

Promotion of uterine reconstruction by a tissue-engineered uterus with biomimetic structure and extracellular matrix microenvironment

The recurrence rate for severe intrauterine adhesions is as high as 60%, and there is still lack of effective prevention and treatment. Inspired by the nature of uterus, we have developed a bilayer scaffold (ECM-SPS) with biomimetic heterogeneous features and extracellular matrix (ECM) microenvironment of the uterus. As proved by subtotal uterine reconstruction experiments, the mechanical and antiadhesion properties of the bilayer scaffold could meet the requirement for uterine repair. With the modification with tissue-specific cell-derived ECM, the ECM-SPS had the ECM microenvironment signatures of both the endometrium and myometrium and exhibited the property of inducing stem cell-directed differentiation. Furthermore, the ECM-SPS has recruited more endogenous stem cells to promote endometrial regeneration at the initial stage of repair, which was accompanied by more smooth muscle regeneration and a higher pregnancy rate. The reconstructed uterus could also sustain normal pregnancy and live birth. The ECM-SPS may thereby provide a potential treatment for women with severe intrauterine adhesions.

Immortalization Reversibility in the Context of Cell Therapy Biosafety

Immortalization (genetically induced prevention of replicative senescence) is a promising approach to obtain cellular material for cell therapy or for bio-artificial organs aimed at overcoming the problem of donor material shortage. Immortalization is reversed before cells are used in vivo to allow cell differentiation into the mature phenotype and avoid tumorigenic effects of unlimited cell proliferation. However, there is no certainty that the process of de-immortalization is 100% effective and that it does not cause unwanted changes in the cell. In this review, we discuss various approaches to reversible immortalization, emphasizing their advantages and disadvantages in terms of biosafety. We describe the most promising approaches in improving the biosafety of reversibly immortalized cells: CRISPR/Cas9-mediated immortogene insertion, tamoxifen-mediated self-recombination, tools for selection of successfully immortalized cells, using a decellularized extracellular matrix, and ensuring post-transplant safety with the use of suicide genes. The last process may be used as an add-on for previously existing reversible immortalized cell lines.

Managing the Heterogeneity of Mesenchymal Stem Cells for Cartilage Regenerative Therapy: A Review

Articular cartilage defects commonly result from trauma and are associated with significant morbidity. Since cartilage is an avascular, aneural, and alymphatic tissue with a poor intrinsic healing ability, the regeneration of functional hyaline cartilage remains a difficult clinical problem. Mesenchymal stem cells (MSCs) are multipotent cells with multilineage differentiation potential, including the ability to differentiate into chondrocytes. Due to their availability and ease of ex vivo expansion, clinicians are increasingly applying MSCs in the treatment of cartilage lesions. However, despite encouraging pre-clinical and clinical data, inconsistencies in MSC proliferative and chondrogenic potential depending on donor, tissue source, cell subset, culture conditions, and handling techniques remain a key barrier to widespread clinical application of MSC therapy in cartilage regeneration. In this review, we highlight the strategies to manage the heterogeneity of MSCs ex vivo for more effective cartilage repair, including reducing the MSC culture expansion period, and selecting MSCs with higher chondrogenic potential through specific genetic markers, surface markers, and biophysical attributes. The accomplishment of a less heterogeneous population of culture-expanded MSCs may improve the scalability, reproducibility, and standardisation of MSC therapy for clinical application in cartilage regeneration.

An efficient metal-organic framework-based drug delivery platform for synergistic antibacterial activity and osteogenesis

Bone implants for clinical application should be endowed with antibacterial activity, biocompatibility, and even osteogenesis-promoting properties. In this work, metal-organic framework (MOF) based drug delivery platform was used to modify titanium implants for improved clinical applicability. Methyl Vanillate@Zeolitic Imidazolate Framework-8 (MV@ZIF-8) was immobilized on the polydopamine (PDA) modified titanium. The sustainable release of the Zn²⁺ and MV causes substantial oxidative damage to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The increased reactive oxygen species (ROS) significantly up-regulates the expression of oxidative stress and DNA damage response genes. Meanwhile, the structural disruption of lipid membranes caused by the ROS, the damage caused by Zinc active sites and the damage accelerated by the MV are both involved in inhibiting bacterial proliferation. The up-regulated expression of the osteogenic-related genes and proteins indicated that the MV@ZIF-8 could effectively promote the osteogenic differentiation of the human bone mesenchymal stem cells (hBMSCs). RNA sequencing and Western blotting analysis revealed that the MV@ZIF-8 coating activates the canonical Wnt/β-catenin signaling pathway through the regulation of tumor necrosis factor (TNF) pathway, thereby promoting the osteogenic differentiation of the hBMSCs. This work demonstrates a promising application of the MOF-based drug delivery platform in bone tissue engineering.

Macromolecular crowding in animal component-free, xeno-free and foetal bovine serum media for human bone marrow mesenchymal stromal cell expansion and differentiation

Background: Cell culture media containing undefined animal-derived components and prolonged in vitro culture periods in the absence of native extracellular matrix result in phenotypic drift of human bone marrow stromal cells (hBMSCs). Methods: Herein, we assessed whether animal component-free (ACF) or xeno-free (XF) media formulations maintain hBMSC phenotypic characteristics more effectively than foetal bovine serum (FBS)-based media. In addition, we assessed whether tissue-specific extracellular matrix, induced via macromolecular crowding (MMC) during expansion and/or differentiation, can more tightly control hBMSC fate. Results: Cells expanded in animal component-free media showed overall the highest phenotype maintenance, as judged by cluster of differentiation expression analysis. Contrary to FBS media, ACF and XF media increased cellularity over time in culture, as measured by total DNA concentration. While MMC with Ficoll™ increased collagen deposition of cells in FBS media, FBS media induced significantly lower collagen synthesis and/or deposition than the ACF and XF media. Cells expanded in FBS media showed higher adipogenic differentiation than ACF and XF media, which was augmented by MMC with Ficoll™ during expansion. Similarly, Ficoll™ crowding also increased chondrogenic differentiation. Of note, donor-to-donor variability was observed for collagen type I deposition and trilineage differentiation capacity of hBMSCs. Conclusion: Collectively, our data indicate that appropriate screening of donors, media and supplements, in this case MMC agent, should be conducted for the development of clinically relevant hBMSC medicines.

Intra-articular injection choice for osteoarthritis: making sense of cell source-an updated systematic review and dual network meta-analysis

BACKGROUND

Intra-articular injection is indicated for mild or moderate osteoarthritis (OA). However, the superiority of cell-based injection and the role of diverse cell sources are still unclear. This study aimed to compare the therapeutic effect of intra-articular injection with mesenchymal stem cells (MSCs) and cell-free methods for OA treatment.

METHODS

A literature search of published scientific data was carried out from PubMed, MEDLINE, Embase, Cochrane Library, Web of Science, and China National Knowledge Internet (CNKI). Randomized controlled trials (RCTs) compared the efficacy and safety of MSC and cell-free intra-articular injection treatments for OA with at least 6-month follow-up.

RESULTS

Dual network meta-analysis validated the therapeutic advantages of MSC treatments (VAS, Bayesian: 90% versus 10% and SUCRA: 94.9% versus 5.1%; WOMAC total, Bayesian: 83% versus 17% and SUCRA: 90.1% versus 9.9%) but also suggested a potential negative safety induced by cell injection (adverse events, Bayesian: 100% versus 0% and SUCRA: 98.2% versus 1.8%). For the MSC source aspect, adipose mesenchymal stem cells (ADMSCs) and umbilical cord mesenchymal stem cells (UBMSCs) showed a better curative effect on pain relief and function improvement compared with bone marrow mesenchymal stem cells (BMMSCs).

CONCLUSION

Intra-articular injection of MSCs is associated with more effective pain alleviation and function improvement than cell-free OA treatment. However, the potential complications induced by MSCs should be emphasized. A comparative analysis of the MSC sources showed that ADMSCs and UBMSCs exerted a better anti-arthritic efficacy than BMMSCs. Schematic illustration of MSC-based intra-articular injection for treating OA. Three major MSCs (UBMSCs, ADMSCs, and BMMSCs) are extracted and expanded in vitro. Subsequently, the amplified MSCs are concentrated and injected into the knee joint to treat OA.

Cryopreservation of porcine skin-derived stem cells using melatonin or trehalose maintains their ability to self-renew and differentiate

Porcine skin-derived stem cells (pSDSCs) are a type of adult stem cells (ASCs) that retain the ability to self-renew and differentiate. Currently, pSDSCs research has entered an intense period of development; however there has been no research regarding methods of cryopreservation. In this paper, we explored an efficient cryopreservation method for pSDSCs. Our results demonstrated that cryopreserving 50 μm diameter pSDSCs aggregates resulted in a lower apoptosis rate and a greater ability to proliferate to form larger spherical cell aggregates than during single-cell cryopreservation. To further optimize the cryopreservation method, we added different concentrations of melatonin (N-acetyl-5-methoxytryptamine, MLT) and trehalose (d-trehalose anhydrous, TRE) to act as cryoprotectants (CPAs) for the pSDSCs. After comparative experiments, we found that the cryopreservation efficiency of 50 mM TRE was superior. Further experiments demonstrated that the reason why 50 mM TRE improved cryopreservation efficiency was that it reduced the intracellular oxidative stress and mitochondrial damage caused by cryopreservation. Taken together, our results suggest that cryopreserving 50 μm diameter pSDSCs aggregates in F12 medium with 10% dimethyl sulfoxide (DMSO) and 50 mM TRE promotes the long-term storage of pSDSCs.

Recombinant expression a novel fibronectin-collage fusion peptide modulating stem cell stemness via integrin β3

Abstract

Constructing bionic extracellular matrix (ECM) is an attractive proposition for tissue engineering and clinical regeneration therapy involving the stemness of stem cells. Here, a novel recombinant protein fibronectin-collagen peptide (FCP) was designed to modulate the function of ECM expressed by Picha. pastoris strain X33. This FCP promotes cell migration and adhesion and maintains rBMSC stemness by binding integrin β3. Its effects were blocked by both integrin β3 siRNA and the integrin β3 inhibitor Cilengitide. A template-independent ab initio prediction modeling approach is the best approach to construct a stable FCP protein model, which predicts the binding sites between FCP and integrin β3. FCP may be used in the in vitro culture and clinical regeneration of stem cells that highly express integrin β3, such as hematopoietic stem cells. The study provides information on the molecular structure of FCP and its bioactivity, which can be used to design new compounds.

Key points

• Design a novel recombinant fibronectin-collagen peptide biomimetic ECM.

• FCP promotes cell adhesion, migration, and proliferation.

• Predicted and verified FCP structure and affinity with integrin β3.

• FCP binds integrin β3 to maintain rBMSC stemness.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-11965-4.

Constructing a highly bioactive tendon-regenerative scaffold by surface modification of tissue-specific stem cell derived extracellular matrix

Developing highly bioactive scaffold materials to promote stem cell migration, proliferation and tissue-specific differentiation is a crucial requirement in current tissue engineering and regenerative medicine. Our previous work has demonstrated that the decellularized tendon slices (DTSs) are able to promote stem cell proliferation and tenogenic differentiation in vitro and show certain pro-regenerative capacity for rotator cuff tendon regeneration in vivo. In this study, we present a strategy to further improve the bioactivity of the DTSs for constructing a novel highly bioactive tendon-regenerative scaffold by surface modification of tendon-specific stem cell-derived extracellular matrix (tECM), which is expected to greatly enhance the capacity of scaffold material in regulating stem cell behavior, including migration, proliferation and tenogenic differentiation. We prove that the modification of tECM could change the highly aligned surface topographical cues of the DTSs, retain the surface stiffness of the DTSs and significantly increase the content of multiple ECM components in the tECM-DTSs. As a result, the tECM-DTSs dramatically enhance the migration, proliferation as well as tenogenic differentiation of rat bone marrow-derived stem cells compared with the DTSs. Collectively, this strategy would provide a new way for constructing ECM-based biomaterials with enhanced bioactivity for in situ tendon regeneration applications.

Decellularized extracellular matrix mediates tissue construction and regeneration

Contributing to organ formation and tissue regeneration, extracellular matrix (ECM) constituents provide tissue with three-dimensional (3D) structural integrity and cellular-function regulation. Containing the crucial traits of the cellular microenvironment, ECM substitutes mediate cell–matrix interactions to prompt stem-cell proliferation and differentiation for 3D organoid construction in vitro or tissue regeneration in vivo. However, these ECMs are often applied generically and have yet to be extensively developed for specific cell types in 3D cultures. Cultured cells also produce rich ECM, particularly stromal cells. Cellular ECM improves 3D culture development in vitro and tissue remodeling during wound healing after implantation into the host as well. Gaining better insight into ECM derived from either tissue or cells that regulate 3D tissue reconstruction or organ regeneration helps us to select, produce, and implant the most suitable ECM and thus promote 3D organoid culture and tissue remodeling for in vivo regeneration. Overall, the decellularization methodologies and tissue/cell-derived ECM as scaffolds or cellular-growth supplements used in cell propagation and differentiation for 3D tissue culture in vitro are discussed. Moreover, current preclinical applications by which ECM components modulate the wound-healing process are reviewed.

Stem cells immortalized by hTERT perform differently from those immortalized by SV40LT in proliferation, differentiation, and reconstruction of matrix microenvironment

Although matrix microenvironment has the potential to improve expanded stem cell proliferation and differentiation capacity, decellularized extracellular matrix (dECM) deposited by senescent cells does not contribute to the rejuvenation of adult stem cells, which has become a barrier to personalized stem cell therapy. Genetic modification is an effective strategy to protect cells from senescence but it carries the increased risk of malignant transformation and genetic instability. In this study, lentivirus carrying either human telomerase reverse transcriptase (hTERT) or simian virus 40 large T antigen (SV40LT) was used to transduce human infrapatellar fat pad-derived stem cells (IPFSCs). We found that virus transduction modified the proliferative, chondrogenic, and adipogenic abilities of IPFSCs. Interestingly, dECM deposited by immortalized cells significantly influenced replicative senescent IPFSCs in proliferation and differentiation preference, the effect of which is hinged on the approach of immortalization using either SV40LT or hTERT. Our findings indicate both dECM expansion and immortalization strategies can be used for replicative senescent adult stem cells' proliferation and lineage-specific differentiation, which benefits future stem cell-based tissue regeneration. This approach may also work for adult stem cells with premature senescence in elderly/aged patients, which needs further investigation. STATEMENT OF SIGNIFICANCE: Adult stem cells are a promising solution for autologous cell-based therapy. Unfortunately, cell senescence due to donor age and/or ex vivo expansion prevents clinical application. Recent progress with decellularized extracellular matrix provides a potential for the rejuvenation of senescent stem cells by improving their proliferation and differentiation capacities. Given the fact that the young matrix can provide a healthy and energetic microenvironment, in this study, two approaches using lentivirus transduction of hTERT and SV40LT were compared. The goal was to immortalize donor cells for deposition of decellularized extracellular matrix. The matrix was demonstrated to contribute diverging effects on the chondrogenic and adipogenic differentiation of expanded stem cells and exhibited proliferation benefits as well. These findings provide an invaluable asset for stem cell-based tissue regeneration.

Recent advancements in decellularized matrix technology for bone tissue engineering

The native extracellular matrix (ECM) provides a matrix to hold tissue/organ, defines the cellular fate and function, and retains growth factors. Such a matrix is considered as a most biomimetic scaffold for tissue engineering due to the biochemical and biological components, 3D hierarchical structure, and physicomechanical properties. Several attempts have been performed to decellularize allo- or xeno-graft tissues and used them for bone repairing and regeneration. Decellularized ECM (dECM) technology has been developed to create an in vivo-like microenvironment to promote cell adhesion, growth, and differentiation for tissue repair and regeneration. Decellularization is mediated through physical, chemical, and enzymatic methods. In this review, we describe the recent progress in bone decellularization and their applications as a scaffold, hydrogel, bioink, or particles in bone tissue engineering. Furthermore, we address the native dECM limitations and the potential of non-bone dECM, cell-based ECM, and engineered ECM (eECM) for in vitro osteogenic differentiation and in vivo bone regeneration.

ECM remodeling in stem cell culture: a potential target for regulating stem cell function

Stem cells (SCs) hold great potential for regenerative medicine, tissue engineering and cell therapy. The clinical applications of SCs require both high quality and quantity of transplantable cells. However, during conventional in vitro expansion, SCs tend to lose properties that make them amenable for cell therapies. Extracellular matrix (ECM) serves an essential regulatory part in the growth, differentiation and homeostasis of all cells in vivo. when signals transmitted to cells, they do not respond passively. Many cell types can remodel pericellular matrix to meet their specific needs. This reciprocal cell-ECM interaction is crucial for the conservation of cell and tissue functions and homeostasis. In vitro ECM remodeling also plays a key role in regulating the lineage fate of SCs. A deeper understanding of in vitro ECM remodeling may provide new perspectives for the maintenance of SC function. In this review, we critically examined three ways that cells can be used to influence the pericellular matrix: (i) exerting tensile force on the ECM, (ii) secreting a variety of ECM proteins, and (iii) degrading the surrounding matrix, and its impact on SC lineage fate. Finally, we describe the deficiencies of current studies and what needs to be done next to further understand the role of ECM remodeling in ex vivo SC cultures.

Periosteal Tissue Engineering: Current Developments and Perspectives

Periosteum, a highly vascularized bilayer connective tissue membrane plays an indispensable role in the repair and regeneration of bone defects. It is involved in blood supply and delivery of progenitor cells and bioactive molecules in the defect area. However, sources of natural periosteum are limited, therefore, there is a need to develop tissue-engineered periosteum (TEP) mimicking the composition, structure, and function of natural periosteum. This review explores TEP construction strategies from the following perspectives: i) different materials for constructing TEP scaffolds; ii) mechanical properties and surface topography in TEP; iii) cell-based strategies for TEP construction; and iv) TEP combined with growth factors. In addition, current challenges and future perspectives for development of TEP are discussed.

Matrix reverses immortalization-mediated stem cell fate determination

Primary cell culture in vitro suffers from cellular senescence. We hypothesized that expansion on decellularized extracellular matrix (dECM) deposited by simian virus 40 large T antigen (SV40LT) transduced autologous infrapatellar fat pad stem cells (IPFSCs) could rejuvenate high-passage IPFSCs in both proliferation and chondrogenic differentiation. In the study, we found that SV40LT transduced IPFSCs exhibited increased proliferation and adipogenic potential but decreased chondrogenic potential. Expansion on dECMs deposited by passage 5 IPFSCs yielded IPFSCs with dramatically increased proliferation and chondrogenic differentiation capacity; however, this enhanced capacity diminished if IPFSCs were grown on dECM deposited by passage 15 IPFSCs. Interestingly, expansion on dECM deposited by SV40LT transduced IPFSCs yielded IPFSCs with enhanced proliferation and chondrogenic capacity but decreased adipogenic potential, particularly for the dECM group derived from SV40LT transduced passage 15 cells. Our immunofluorescence staining and proteomics data identify matrix components such as basement membrane proteins as top candidates for matrix mediated IPFSC rejuvenation. Both cell proliferation and differentiation were endorsed by transcripts measured by RNASeq during the process. This study provides a promising model for in-depth investigation of the matrix protein influence on surrounding stem cell differentiation.

Mesenchymal stem cell-derived extracellular matrix (mECM): a bioactive and versatile scaffold for musculoskeletal tissue engineering

Mesenchymal stem cell-derived extracellular matrix (mECM) has received increased attention in the fields of tissue engineering and scaffold-assisted regeneration. mECM exhibits many unique characteristics, such as robust bioactivity, biocompatibility, ease of use, and the potential for autologous tissue engineering. As the use of mECM has increased in musculoskeletal tissue engineering, it should be noted that mECM generated from current methods has inherited insufficiencies, such as low mechanical properties and lack of internal architecture. In this review, we first summarize the development and use of mECM as a scaffold for musculoskeletal tissue regeneration and highlight our current progress on moving this technology toward clinical application. Then we review recent methods to improve the properties of mECM that will overcome current weaknesses. Lastly, we propose future studies that will pave the road for mECM application in regenerating tissues in humans.

Cell-Derived Extracellular Matrix for Tissue Engineering and Regenerative Medicine

Cell-derived extracellular matrices (CD-ECMs) captured increasing attention since the first studies in the 1980s. The biological resemblance of CD-ECMs to their in vivo counterparts and natural complexity provide them with a prevailing bioactivity. CD-ECMs offer the opportunity to produce microenvironments with costumizable biological and biophysical properties in a controlled setting. As a result, CD-ECMs can improve cellular functions such as stemness or be employed as a platform to study cellular niches in health and disease. Either on their own or integrated with other materials, CD-ECMs can also be utilized as biomaterials to engineer tissues de novo or facilitate endogenous healing and regeneration. This review provides a brief overview over the methodologies used to facilitate CD-ECM deposition and manufacturing. It explores the versatile uses of CD-ECM in fundamental research and therapeutic approaches, while highlighting innovative strategies. Furthermore, current challenges are identified and it is accentuated that advancements in methodologies, as well as innovative interdisciplinary approaches are needed to take CD-ECM-based research to the next level.

Computational Modeling of Human Mesenchymal Stromal Cell Proliferation and Extra-Cellular Matrix Production in 3D Porous Scaffolds in a Perfusion Bioreactor: The Effect of Growth Factors

Stem cell expansion on 3D porous scaffolds cultured in bioreactor systems has been shown to be beneficial for maintenance of the original cell functionality in tissue engineering strategies (TE). However, the production of extracellular matrix (ECM) makes harvesting the progenitor cell population from 3D scaffolds a challenge. Medium composition plays a role in stimulating cell proliferation over extracellular matrix (ECM) production. In this regard, a computational model describing tissue growth inside 3D scaffolds can be a great tool in designing optimal experimental conditions. In this study, a computational model describing cell and ECM growth in a perfusion bioreactor is developed, including a description of the effect of a (generic) growth factor on the biological processes taking place inside the 3D scaffold. In the model, the speed of cell and ECM growth depends on the flow-induced shear stress, curvature and the concentrations of oxygen, glucose, lactate, and growth factor. The effect of the simulated growth factor is to differentially enhance cell proliferation over ECM production. After model calibration with historic in-house data, a multi-objective optimization procedure is executed aiming to minimize the total experimental cost whilst maximizing cell growth during culture. The obtained results indicate there are multiple optimum points for the medium refreshment regime and the initial growth factor concentration where a trade-off is made between the final amount of cells and the culture cost. Finally, the model is applied to experiments reported in the literature studying the effects of perfusion-based cell culture and/or growth factor supplementation on cell expansion. The qualitative similarities between the simulation and experimental results, even in the absence of proper model calibration, reinforces the generic character of the proposed modeling framework. The model proposed in this study can contribute to the cost efficient production of cell-based TE products, ultimately contributing to their affordability and accessibility.

Liver Kinase B1 Fine-Tunes Lineage Commitment of Human Fetal Synovium-Derived Stem Cells

Liver kinase B1 (LKB1), a serine/threonine protein, is a key regulator in stem cell function and energy metabolism. Herein, we describe the role of LKB1 in modulating the differentiation of synovium-derived stem cells (SDSCs) toward chondrogenic, adipogenic, and osteogenic lineages. Human fetal SDSCs were transduced with CRISPR associated protein 9 (Cas9)-single-guide RNA vectors to knockout or lentiviral vectors to overexpress the LKB1 gene. Analyses including ICE (Inference of CRISPR Edits) data from Sanger sequencing and quantitative polymerase chain reaction (qPCR) as well as Western blot demonstrated successful knockout (KO) or overexpression (OE) of LKB1 in human fetal SDSCs without any detectable side effects in morphology, proliferation rate, and cell cycle. LKB1 KO increased CD146 expression; interestingly, LKB1 OE increased SSEA4 level. The qPCR data showed that LKB1 KO upregulated the levels of SOX2 and NANOG while LKB1 OE lowered the expression of POU5F1 and KLF4. Furthermore, LKB1 KO enhanced, and LKB1 OE inhibited, chondrogenic and adipogenic differentiation potential. However, perhaps due to the inherent inability to achieve osteogenesis, LKB1 did not obviously affect osteogenic differentiation. These data demonstrate that LKB1 plays a significant role in determining human SDSCs' adipogenic and chondrogenic differentiation, which might provide an approach for fine-tuning the direction of stem cell differentiation in tissue engineering and regeneration. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:258-268, 2020.

An insight into cell-laden 3D-printed constructs for bone tissue engineering

In this review, we have spotlighted various combinations of bioinks to optimize the biofabrication of 3D bone constructs.

Impact of Fibronectin Knockout on Proliferation and Differentiation of Human Infrapatellar Fat Pad-Derived Stem Cells

Fibronectin plays an essential role in tissue development and regeneration. However, the effects of fibronectin knockout (FN1-KO) on stem cells' proliferation and differentiation remain unknown. In this study, CRISPR/Cas9 generated FN1-KO in human infrapatellar fat pad-derived stem cells (IPFSCs) was evaluated for proliferation ability including cell cycle and surface markers as well as stemness gene expression and for differentiation capacity including chondrogenic and adipogenic differentiation. High passage IPFSCs were also evaluated for proliferation and differentiation capacity after expansion on decellularized ECM (dECM) deposited by FN1-KO cells. Successful FN1-KO in IPFSCs was confirmed by Sanger sequencing and Inference of CRISPR Edits analysis (ICE) as well as immunostaining for fibronectin expression. Compared to the GFP control, FN1-KO cells showed an increase in cell growth, percentage of cells in the S and G2 phases, and CD105 and CD146 expression but a decrease in expression of stemness markers CD73, CD90, SSEA4, and mesenchymal condensation marker CDH2 gene. FN1-KO decreased both chondrogenic and adipogenic differentiation capacity. Interestingly, IPFSCs grown on dECMs deposited by FN1-KO cells exhibited a decrease in cell proliferation along with a decline in CDH2 expression. After induction, IPFSCs plated on dECMs deposited by FN1-KO cells also displayed decreased expression of both chondrogenic and adipogenic capacity. We concluded that FN1-KO increased human IPFSCs' proliferation capacity; however, this capacity was reversed after expansion on dECM deposited by FN1-KO cells. Significance of fibronectin in chondrogenic and adipogenic differentiation was demonstrated in both FN1-KO IPFSCs and FN(-) matrix microenvironment.

Mesenchymal Stem Cells Coated by the Extracellular Matrix Promote Wound Healing in Diabetic Rats

OBJECTIVE

To investigate the effects of mesenchymal stem cells (MSCs) coated by the extracellular matrix (ECM) on wound healing in diabetic rats.

METHODS

Mesenchymal stem cells were cocultured with ECM. Cell viabilities were evaluated using MTT assay. The diabetes model was established using both STZ and high-glucose/fat methods in SD rats. A wound area was made on the middle of the rats' back. MSCs or ECM-MSCs were used to treat the rats. HE staining and CD31 immunohistochemistry were used to detect the skin thickness and angiogenesis. Western blotting and qRT-PCR were conducted to determine the level of VEGF-α, PDGF, and EGF.

RESULTS

It was observed that treatment of ECM had no significant effects on the cell viability of ECM-MSCs. Wound area assay showed that both MSCs and ECM-MSCs could enhance the wound healing of diabetic rats and ECM-MSCs could further promote the effects. Both MSCs and ECM-MSCs could enhance angiogenesis and epithelialization of the wounds, as well as the expression of VEGF-α, PDGF, and EGF in wound tissues, while ECM-MSC treatment showed more obvious effects.

CONCLUSION

Mesenchymal stem cells coated by the extracellular matrix could promote wound healing in diabetic rats. Our study may offer a novel therapeutic method for impaired diabetic wound healing.

A prospect of cell immortalization combined with matrix microenvironmental optimization strategy for tissue engineering and regeneration

Cellular senescence is a major hurdle for primary cell-based tissue engineering and regenerative medicine. Telomere erosion, oxidative stress, the expression of oncogenes and the loss of tumor suppressor genes all may account for the cellular senescence process with the involvement of various signaling pathways. To establish immortalized cell lines for research and clinical use, strategies have been applied including internal genomic or external matrix microenvironment modification. Considering the potential risks of malignant transformation and tumorigenesis of genetic manipulation, environmental modification methods, especially the decellularized cell-deposited extracellular matrix (dECM)-based preconditioning strategy, appear to be promising for tissue engineering-aimed cell immortalization. Due to few review articles focusing on this topic, this review provides a summary of cell senescence and immortalization and discusses advantages and limitations of tissue engineering and regeneration with the use of immortalized cells as well as a potential rejuvenation strategy through combination with the dECM approach.

Functionality of decellularized matrix in cartilage regeneration: A comparison of tissue versus cell sources

Increasing evidence indicates that decellularized extracellular matrices (dECMs) derived from cartilage tissues (T-dECMs) or chondrocytes/stem cells (C-dECMs) can support proliferation and chondrogenic differentiation of cartilage-forming cells. However, few review papers compare the differences between these dECMs when they serve as substrates for cartilage regeneration. In this review, after an introduction of cartilage immunogenicity and decellularization methods to prepare T-dECMs and C-dECMs, a comprehensive comparison focuses on the effects of T-dECMs and C-dECMs on proliferation and chondrogenic differentiation of chondrocytes/stem cells in vitro and in vivo. Key factors within dECMs, consisting of microarchitecture characteristics and micromechanical properties as well as retained insoluble and soluble matrix components, are discussed in-depth for potential mechanisms underlying the functionality of these dECMs in regulating chondrogenesis. With this information, we hope to benefit dECM based cartilage engineering and tissue regeneration for future clinical application.

STATEMENT OF SIGNIFICANCE

The use of decellularized extracellular matrix (dECM) is becoming a promising approach for tissue engineering and regeneration. Compared to dECM derived from cartilage tissue, recently reported dECM from cell sources exhibits a distinct role in cell based cartilage regeneration. In this review paper, for the first time, tissue and cell based dECMs are comprehensively compared for their functionality in cartilage regeneration. This information is expected to provide an update for dECM based cartilage regeneration.

Subpopulations of dermal skin fibroblasts secrete distinct extracellular matrix: implications for using skin substitutes in the clinic

Background

While several commercial dermoepidermal scaffolds can promote wound healing of the skin, the achievement of complete skin regeneration still represents a major challenge.

Objectives

To perform biological characterization of self‐assembled extracellular matrices (ECMs) from three different subpopulations of fibroblasts found in human skin: papillary fibroblasts (Pfi), reticular fibroblasts (Rfi) and dermal papilla fibroblasts (DPfi).

Methods

Fibroblast subpopulations were cultured with ascorbic acid to promote cell‐assembled matrix production for 10 days. Subsequently, cells were removed and the remaining matrices characterized. Additionally, in another experiment, keratinocytes were seeded on the top of cell‐depleted ECMs to generate epidermal‐only skin constructs.

Results

We found that the ECM self‐assembled by Pfi exhibited randomly oriented fibres associated with the highest interfibrillar space, reflecting ECM characteristics that are physiologically present within the papillary dermis. Mass spectrometry followed by validation with immunofluorescence analysis showed that thrombospondin 1 is preferentially expressed within the DPfi‐derived matrix. Moreover, we observed that epidermal constructs grown on DPfi or Pfi matrices exhibited normal basement membrane formation, whereas Rfi matrices were unable to support membrane formation.

Conclusions

We argue that inspiration can be taken from these different ECMs, to improve the design of therapeutic biomaterials in skin engineering applications.

What's already known about this topic?

There are several types of skin fibroblasts within the dermis that can be defined by their spatial location: papillary fibroblasts (Pfi), reticular fibroblasts (Rfi) and dermal papilla fibroblasts (DPfi).

Extracellular matrix (ECM) composition is distinct with regard to composition and architecture within the papillary, reticular and hair follicle dermis in vivo.

When skin is injured, dermal replacement substitutes used for tissue repair do not reflect the heterogeneity observed within the skin dermis.

What does this study add?

Self‐assembled ECMs from different subpopulations of skin fibroblasts can be generated in vitro.

Cell‐assembled ECMs made in vitro from Pfi, Rfi and DPfi reflect dermal heterogeneity seen in vivo and are morphologically, functionally and compositionally distinct from one another.

Inspiration should be taken from cell‐assembled ECMs from distinct fibroblast subpopulations, to improve the design of therapeutic biomaterials in skin engineering applications.

What is the translational message?

Cell‐assembled ECMs from DPfi and Pfi, but not Rfi, can support formation of a basement membrane in adjacent keratinocytes in vitro.

Inspiration should be taken from cell‐assembled ECMs from distinct fibroblast subpopulations, to improve the design of therapeutic biomaterials in skin engineering applications.

Linked Comment: https://doi.org/10.1111/bjd.16773.

https://doi.org/10.1111/bjd.16946 available online

https://goo.gl/Uqv3dl

Inhibition of osteoclastogenesis by stem cell-derived extracellular matrix through modulation of intracellular reactive oxygen species

Decellularized extracellular matrix (ECM) derived from stem cells has been shown as a promising biomaterial for bone regeneration because of the promotion effect on osteogenesis in mesenchymal stem cells (MSCs). However, bone regeneration is also influenced by bone resorption and little is known about the effect of cell-derived ECM on osteoclast differentiation. In this study, ECM was deposited by MSCs and, after decellularization, the effect of ECM on osteoclastogenesis of bone marrow monocytes (BMMs) was investigated in comparison to standard tissue culture polystyrene. Our results showed that cell-derived ECM improved BMM proliferation but potently inhibited osteoclast differentiation, evidenced by down-regulation of multinucleated tartrate-resistant acid phosphatase (TRAP)-positive cells, areas of actin rings, and osteoclast-specific gene expression. ECM-mediated attenuation of intracellular reactive oxygen species (ROS) was suggested to play a rival role in the inhibition of osteoclastogenesis, because exogenous hydrogen peroxide supplementation partially rescued the ECM-inhibited osteoclastogenesis. Furthermore, rather than collagen type I, fibronectin in the ECM contributed to ECM-mediated anti-osteoclastogenesis. In conclusion, stem cell-derived decellularized ECM significantly suppressed osteoclastogenesis via the attenuation of intracellular ROS. The anti-osteoclastogenic property of cell-derived ECM may benefit its clinical use for modulating bone remodeling and promoting bone tissue engineering.

STATEMENT OF SIGNIFICANCE

Decellularized extracellular matrix (ECM) derived from stem cells has been shown as a promising biomaterial for bone regeneration; however, bone remodeling is influenced by bone resorption and little is known about the effect of cell-derived ECM on osteoclast differentiation. Cell-derived ECM improved BMM proliferation but potently inhibited osteoclast differentiation. ECM-mediated attenuation of intracellular reactive oxygen species was suggested to play a rival role in osteoclastogenesis. Fibronectin in cell-derived ECM also contributed to ECM-mediated anti-osteoclastogenesis. The anti-osteoclastogenic property of cell-derived ECM may benefit clinically for modulating bone remodeling and promoting bone tissue engineering.

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.

Fibroblast Growth Factor Ligand Dependent Proliferation and Chondrogenic Differentiation of Synovium-Derived Stem Cells and Concomitant Adaptation of Wnt/Mitogen-Activated Protein Kinase Signals

Cell expansion techniques commonly utilize exogenous factors to increase cell proliferation and create a larger cell population for use in cell-based therapies. One strategy for cartilage regenerative therapies is autologous stem cell expansion and fibroblast growth factor (FGF) supplementation during cell expansion, particularly FGF-2. However, it is unknown whether FGF-10, another FGF implicated in limb and skeletal development, can elicit the same rejuvenation responses in terms of proliferation and differentiation of human synovium-derived stem cells (SDSCs). In this study, we expanded SDSCs in either FGF-2 or FGF-10 for 7 days; a control group had no treatment. FGF-2 and FGF-10 supplementation was also exclusively tested during the differentiation phase. Expanded SDSCs were evaluated for their ability to successfully engage in chondrogenic and osteogenic differentiation. We found that FGF-2 supplementation during proliferation, but not differentiation, was able to increase glycosaminoglycan deposition, pellet size, and chondrogenic gene expression following chondrogenic induction, as well as increased calcium deposition, alkaline phosphatase activity, and expression of vital osteogenic differentiation genes following osteogenic induction. FGF-10 did not elicit a similar preconditioning effect. We also observed changes of both Wnt signals and mitogen-activated protein kinase expression during SDSC chondrogenesis, which occurred in a manner dependent upon the supplementation phase of FGF-2 administration. These results indicated that FGF-2, but not FGF-10, may be supplemented during stem cell expansion to prime cells for successful chondrogenesis and osteogenesis.

Melatonin protects bone marrow mesenchymal stem cells against iron overload-induced aberrant differentiation and senescence

Bone marrow mesenchymal stem cells (BMSCs) are an expandable population of stem cells which can differentiate into osteoblasts, chondrocytes and adipocytes. Dysfunction of BMSCs in response to pathological stimuli contributes to bone diseases. Melatonin, a hormone secreted from pineal gland, has been proved to be an important mediator in bone formation and mineralization. The aim of this study was to investigate whether melatonin protected against iron overload-induced dysfunction of BMSCs and its underlying mechanisms. Here, we found that iron overload induced by ferric ammonium citrate (FAC) caused irregularly morphological changes and markedly reduced the viability in BMSCs. Consistently, osteogenic differentiation of BMSCs was significantly inhibited by iron overload, but melatonin treatment rescued osteogenic differentiation of BMSCs. Furthermore, exposure to FAC led to the senescence in BMSCs, which was attenuated by melatonin as well. Meanwhile, melatonin was able to counter the reduction in cell proliferation by iron overload in BMSCs. In addition, protective effects of melatonin on iron overload-induced dysfunction of BMSCs were abolished by its inhibitor luzindole. Also, melatonin protected BMSCs against iron overload-induced ROS accumulation and membrane potential depolarization. Further study uncovered that melatonin inhibited the upregulation of p53, ERK and p38 protein expressions in BMSCs with iron overload. Collectively, melatonin plays a protective role in iron overload-induced osteogenic differentiation dysfunction and senescence through blocking ROS accumulation and p53/ERK/p38 activation.

Cell-derived micro-environment helps dental pulp stem cells promote dental pulp regeneration

OBJECTIVES

The function of the dental pulp is closely connected to the extracellular matrix (ECM) structure, and ECM has received significant attention due to its biological functions for regulating cells. As such, the interaction between the ECM niche and cells is worth exploring for potential clinical uses.

MATERIALS AND METHODS

In this study, dental pulp stem cell (DPSC)-derived ECM (DPM) was prepared through cell culture and decellularization to function as the cell niche, and changes in DPSC behaviour and histological analysis of dental pulp tissue regeneration were evaluated following the DPM culture. DPM promoted the replication of DPSCs and exhibited retention of their mineralization. Then, the DPM-based culture strategy under odontogenic culture medium was further investigated, and the mineralization-related markers showed that DPSCs were regulated towards odontogenic differentiation. Dental pulp-like tissue with well-arranged ECM was harvested after a 2-month subcutaneous implantation in nude mice with DPM application. Additionally, DPSCs cultured on the plastic culture surface showed the up-regulation of mineralization makers in vitro, but there was a disorder in matrix formation and mineralization when the cells were cultured in vivo.

RESULTS AND CONCLUSIONS

DPM-based cultivation could serve as a cell niche and modulate DPSC behaviour, and this method also provided an alternative to harvest tissue-specific ECM and provided a strategy for ECM-cell interaction.

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.

Meniscus, articular cartilage and nucleus pulposus: a comparative review of cartilage-like tissues in anatomy, development and function

The degradation of cartilage in the human body is impacted by aging, disease, genetic predisposition and continued insults resulting from daily activity. The burden of cartilage defects (osteoarthritis, rheumatoid arthritis, intervertebral disc damage, knee replacement surgeries, etc.) is daunting in light of substantial economic and social stresses. This review strives to broaden the scope of regenerative medicine and tissue engineering approaches used for cartilage repair by comparing and contrasting the anatomical and functional nature of the meniscus, articular cartilage (AC) and nucleus pulposus (NP). Many review papers have provided detailed evaluations of these cartilages and cartilage-like tissues individually but none have comprehensively examined the parallels and inconsistencies in signaling, genetic expression and extracellular matrix composition between tissues. For the first time, this review outlines the importance of understanding these three tissues as unique entities, providing a comparative analysis of anatomy, ultrastructure, biochemistry and function for each tissue. This novel approach highlights the similarities and differences between tissues, progressing research toward an understanding of what defines each tissue as distinctive. The goal of this paper is to provide researchers with the fundamental knowledge to correctly engineer the meniscus, AC and NP without inadvertently developing the wrong tissue function or biochemistry.

A novel culture platform for fast proliferation of human annulus fibrosus cells

Tissue engineering provides a promising approach to treat degenerative disc disease, which usually requires a large quantity of seed cells. A simple and reliable in vitro culture system to expand seed cells in a timely fashion is necessary to implement the application clinically. Here, we sought to establish a cost-effective culture system for expanding human annulus fibrosus cells using extracellular matrix (ECM) proteins as culture substrates. Cells were cultured onto a plastic surface coated with various types of ECMs, including fibronectin, vitronectin, collagen type I, gelatin and cell-free matrix deposited by human nucleus pulposus cells. AF cell morphology, growth, adhesion and phenotype (anabolic and catabolic markers) were assessed by microscopy, real-time RT-PCR, western blotting, zymography, immunofluorescence staining and biochemical assays. Fibronectin, collagen and gelatin promoted cell proliferation and adhesion in a dose-dependent manner. Fibronectin elevated mRNA expression of proteoglycan and enhanced glycosaminoglycan production. Both collagen and gelatin increased protein expression of type II collagen. Consistent with increased cell adhesion, collagen and fibronectin promoted formation of focal adhesion complexes in the cell-matrix junction, suggesting enhanced binding of the actin network with both ECM substrates. On the other hand, fibronectin, collagen and gelatin decreased expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 in media. Finally, a mixture of fibronectin (1.7 μg/mL) and collagen (1.3 μg/mL) was identified as the most promising in vitro culture substrate system in promoting proliferation and maintaining anabolic-catabolic balance. Our method provides a simple and cost-effective platform for tissue engineering applications in intervertebral disc research.

Hydrophilic cell-derived extracellular matrix as a niche to promote adhesion and differentiation of neural progenitor cells

Cell-derived extracellular matrix exhibits excellent adhesion performance for neural progenitor cell anchoring and residency, resulting in promoted proliferation of the stem cells to basal forebrain cholinergic neurons.

A Protocol to Prepare Decellularized Stem Cell Matrix for Rejuvenation of Cell Expansion and Cartilage Regeneration

Traditional ex vivo expansion of adult stem cells yields an insufficient quantity of less potent cells. Here we describe the fabrication of decellularized matrix deposited by synovium-derived stem cells (SDSCs). This matrix could serve as a three-dimensional expansion system to rejuvenate cells for proliferation and tissue-specific differentiation potential, which could benefit cartilage regeneration. The decellularized stem cell matrix (DSCM) might be a powerful system for tissue engineering and regeneration.

Environmental preconditioning rejuvenates adult stem cells' proliferation and chondrogenic potential

Adult stem cells are a promising cell source for cartilage regeneration. Unfortunately, due to donor age and ex vivo expansion, stem cell senescence becomes a huge hurdle for these cells to be used clinically. Increasing evidence indicates that environmental preconditioning is a powerful approach in promoting stem cells' ability to resist a harsh environment post-engraftment, such as hypoxia and inflammation. However, few reports organize and evaluate the literature regarding the rejuvenation effect of environmental preconditioning on stem cell proliferation and chondrogenic differentiation capacity, which are important variables for stem cell based tissue regeneration. This report aims to identify several critical environmental factors such as oxygen concentration, growth factors, and extracellular matrix and to discuss their preconditioning influence on stem cells' rejuvenation including proliferation and chondrogenic potential as well as underlying molecular mechanisms. We believe that environmental preconditioning based rejuvenation is a simpler and safer strategy to program pre-engraftment stem cells for better survival and enhanced proliferation and differentiation capacity without the undesired effects of some treatments, such as genetic manipulation.

A Selective Cell Population from Dermis Strengthens Bone Regeneration

Finding appropriate seed cells for bone tissue engineering remains a significant challenge. Considering that skin is the largest organ, we hypothesized that human bone morphogenetic protein receptor type IB (BmprIB)+ dermal cells could have enhanced osteogenic capacity in the healing of critical-sized calvarial defects in an immunodeficient mouse model. In this study, immunohistochemical staining revealed that BmprIB was expressed throughout reticular dermal cells; the positive expression rate of BmprIB was 3.5% ± 0.4% in freshly separated dermal cells, by flow cytometry. Furthermore, in vitro osteogenic capacity of BmprIB+ cells was confirmed by osteogenic-related staining and marker gene expression compared with unsorted dermal cells. In vivo osteogenic capacity was demonstrated by implantation of human BmprIB+ cell/coral constructs in the treatment of 4-mm diameter calvarial defects in an immunodeficient mouse model compared with implantation of unsorted cell/coral constructs and coral scaffold alone. These results indicate that the selective cell population BmprIB from human dermis is a promising osteogenic progenitor cell that can be a large-quantity and high-quality cell source for bone tissue engineering and regeneration. Stem Cells Translational Medicine 2017;6:306-315.

Culturing on decellularized extracellular matrix enhances antioxidant properties of human umbilical cord-derived mesenchymal stem cells

Human umbilical cord-derived mesenchymal stem cells (UC-MSCs) have attracted great interest in clinical application because of their regenerative potential and their lack of ethical issues. Our previous studies showed that decellularized cell-deposited extracellular matrix (ECM) provided an in vivo-mimicking microenvironment for MSCs and facilitated in vitro cell expansion. This study was conducted to analyze the cellular response of UC-MSCs when culturing on the ECM, including reactive oxygen species (ROS), intracellular antioxidative enzymes, and the resistance to exogenous oxidative stress. After decellularization, the architecture of cell-deposited ECM was characterized as nanofibrous, collagen fibrils and the matrix components were identified as type I and III collagens, fibronectin, and laminin. Compared to tissue culture polystyrene (TCPS) plates, culturing on ECM yielded a 2-fold increase of UC-MSC proliferation and improved the percentage of cells in the S phase by 2.4-fold. The levels of intracellular ROS and hydrogen peroxide (H2O2) in ECM-cultured cells were reduced by 41.7% and 82.9%, respectively. More importantly, ECM-cultured UC-MSCs showed enhanced expression and activity of intracellular antioxidative enzymes such as superoxide dismutase and catalase, up-regulated expression of silent information regulator type 1, and suppressed phosphorylation of p38 mitogen-activated protein kinase. Furthermore, a continuous treatment with exogenous 100μM H2O2 dramatically inhibited osteogenic differentiation of UC-MSCs cultured on TCPS, but culturing on ECM retained the differentiation capacity for matrix mineralization and osteoblast-specific marker gene expression. Collectively, by providing sufficient cell amounts and enhancing antioxidant capacity, decellularized ECM can be a promising cell culture platform for in vitro expansion of UC-MSCs.

Combined effects of engineered tendon matrix and GDF-6 on bone marrow mesenchymal stem cell-based tendon regeneration

OBJECTIVES

To examine whether an engineered tendon matrix (ETM) environment and growth and differentiation factor-6 (GDF-6) have synergistic effects on the tenogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and the quality of tendon repair.

RESULTS

ETM and GDF-6 promote tenogenic differentiation of BMSCs in vitro. Implantation of GDF-6-incorporated ETM containing BMSCs into a tendon injury model significantly improved the histological and mechanical properties of the repaired tendon.

CONCLUSIONS

GDF-6-incorporated ETM containing BMSCs represents a promising strategy for tendon injury repair.

Nascent osteoblast matrix inhibits osteogenesis of human mesenchymal stem cells in vitro

INTRODUCTION

Adult mesenchymal stem cells (MSCs) are considered promising candidates for cell-based therapies. Their potential utility derives primarily from their immunomodulatory activity, multi-lineage differentiation potential, and likely progenitor cell function in wound healing and repair of connective tissues. However, in vitro, MSCs often senesce and spontaneously differentiate into osteoblasts after prolonged expansion, likely because of lack of regulatory microenvironmental signals. In vivo, osteoblasts that line the endosteal bone marrow surface are in close proximity to MSCs in the marrow stroma and thus may help to regulate MSC fate.

METHODS

We examined here how osteogenic differentiation of MSCs in vitro is affected by exposure to osteoblastic cells (OBCs). Human bone marrow MSCs were exposed to OBCs, derived by induced osteogenic differentiation of MSCs, either directly in contact co-cultures, or indirectly to OBC-conditioned medium or decellularized OBC extracellular matrix (ECM).

RESULTS

Our results showed that OBCs can act as negative regulators of MSC osteogenesis. mRNA expression profiling revealed that OBCs did not affect MSC osteogenesis in direct contact cultures or via secreted factors. However, seeding MSCs on decellularized OBC ECM significantly decreased expression of several osteogenic genes and maintained their fibroblastic morphologies. Proteomic analysis identified some of the candidate protein regulators of MSC osteogenesis.

CONCLUSIONS

These findings provide the basis for future studies to elucidate the signaling mechanisms responsible for osteoblast matrix-mediated regulation of MSC osteogenesis and to better manipulate MSC fate in vitro to minimize their spontaneous differentiation.

Impact of tissue-specific stem cells on lineage-specific differentiation: a focus on the musculoskeletal system

Tissue-specific stem cells are found throughout the body and, with proper intervention and environmental cues, these stem cells exercise their capabilities for differentiation into several lineages to form cartilage, bone, muscle, and adipose tissue in vitro and in vivo. Interestingly, it has been widely demonstrated that they do not differentiate with the same efficacy during lineage-specific differentiation studies, as the tissue-specific stem cells are generally more effective when differentiating toward the tissues from which they were derived. This review focuses on four mesodermal lineages for tissue-specific stem cell differentiation: adipogenesis, chondrogenesis, myogenesis, and osteogenesis. It is intended to give insight into current multilineage differentiation and comparative research, highlight and contrast known trends regarding differentiation, and introduce supporting evidence which demonstrates particular tissue-specific stem cells' superiority in lineage-specific differentiation, along with their resident tissue origins and natural roles. In addition, some epigenetic and transcriptomic differences between stem cells which may explain the observed trends are discussed.