Native extracellular matrix preserves mesenchymal stem cell "stemness" and differentiation potential under serum-free culture conditions

Promotion of quiescence and maintenance of function of mesenchymal stem cells on substrates with surface potential

The widespread use of human mesenchymal stem cells(hMSCs) is impeded by functional loss during prolonged expansion. Although multiple approaches have been attempted to preserve hMSCs stemness, a suitable culture system remains to be modified. The interaction between electrical signals and stem cells is expected to better maintain the function of stem cells. However, it remains unclear whether the surface potential of substrates has the potential to preserve stem cell function during in vitro expansion. In our study, hMSCs cultured on materials with different surface potentials could be induced into a reversible quiescent state, and we demonstrated that quiescent hMSCs could be reactivated and transitioned back into the proliferation cell cycle. hMSCs cultured under appropriate potential displayed superior differentiation and proliferation abilities within the same generation compared to conventional conditions. These findings underscore the importance of surface potential as a critical physical factor regulating hMSCs stemness. Manipulating the surface potential of hMSCs culture substrates holds promise for optimising preservation and culture conditions, thereby enhancing their application in tissue repair and regeneration engineering.

Decellularized extracellular matrix derived from dental pulp stem cells promotes gingival fibroblast adhesion and migration

BACKGROUND

Decellularized extracellular matrix (dECM) has been proposed as a useful source of biomimetic materials for regenerative medicine due to its biological properties that regulate cell behaviors. The present study aimed to investigate the influence of decellularized ECM derived from dental pulp stem cells (DPSCs) on gingival fibroblast (GF) cell behaviors. Cells were isolated from dental pulp and gingival tissues. ECM was derived from culturing dental pulp stem cells in growth medium supplemented with ascorbic acid. A bioinformatic database of the extracellular matrix was constructed using Metascape. GFs were reseeded onto dECM, and their adhesion, spreading, and organization were subsequently observed. The migration ability of the cells was determined using a scratch assay. Protein expression was evaluated using immunofluorescence staining.

RESULTS

Type 1 collagen and fibronectin were detected on the ECM and dECM derived from DPSCs. Negative phalloidin and nuclei were noted in the dECM. The proteomic database revealed enrichment of several proteins involved in ECM organization, ECM-receptor interaction, and focal adhesion. Compared with those on the controls, the GFs on the dECM exhibited more organized stress fibers. Furthermore, cultured GFs on dECM exhibited significantly enhanced migration and proliferation abilities. Interestingly, GFs seeded on dECM showed upregulation of FN1, ITGB3, and CTNNB1 mRNA levels.

CONCLUSIONS

ECM derived from DSPCs generates a crucial microenvironment for regulating GF adhesion, migration and proliferation. Therefore, decellularized ECM from DPSCs could serve as a matrix for oral tissue repair.

Decellularized extracellular matrix coupled with polycaprolactone/laponite to construct a biomimetic barrier membrane for bone defect repair

Barrier membranes play a prominent role in guided bone regeneration (GBR), and polycaprolactone (PCL) is an attractive biomaterial for the fabrication of barrier membranes. However, these nanofiber membranes (NFMs) require modification to improve their biological activity. PCL-NFMs incorporating with laponite (LAP) achieve biofunctional modification. Decellularized extracellular matrix (dECM) could modulate cell behaviour. The present study combined dECM with PCL/LAP-NFMs to generate a promising strategy for bone tissue regeneration. Bone marrow mesenchymal stem cells (BMSCs) were cultured on NFMs and deposited with an abundant extracellular matrix (ECM), which was subsequently decellularized to obtain dECM-modified PCL/LAP-NFMs (PCL/LAP-dECM-NFMs). The biological functions of the membranes were evaluated by reseeding MC3T3-E1 cells in vitro and transplanting them into rat calvarial defects in vivo. These results indicate that PCL/LAP-dECM-NFMs were successfully constructed. The presence of dECM slightly improved the mechanical properties of the NFMs, which exhibited a Young's modulus of 0.269 MPa, ultimate tensile strength of 2.04 MPa and elongation at break of 51.62 %. In vitro, the PCL/LAP-dECM-NFMs had favourable cytocompatibility, and the enhanced hydrophilicity was conducive to cell adhesion, proliferation, and osteoblast differentiation. PCL/LAP-dECM-NFMs exhibited an excellent bone repair capacity in vivo. Overall, dECM-modified PCL/LAP-NFMs should be promising biomimetic barrier membranes for GBR.

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.

Pulmonary decellularized extracellular matrix (dECM) modified polyethylene terephthalate three-dimensional cell carriers regulate the proliferation and paracrine activity of mesenchymal stem cells

Introduction: Mesenchymal stem cells (MSCs) possess a high degree of self-renewal capacity and in vitro multi-lineage differentiation potential. Decellularized materials have garnered considerable attention due to their elevated biocompatibility, reduced immunogenicity, excellent biodegradability, and the ability to partially mimic the in vivo microenvironment conducive to cell growth. To address the issue of mesenchymal stem cells losing their stem cell characteristics during two-dimensional (2D) cultivation, this study established three-dimensional cell carriers modified with lung decellularized extracellular matrix and assessed its impact on the life activities of mesenchymal stem cells. Methods: This study employed PET as a substrate material, grafting with polydopamine (PDA), and constructing a decellularized extracellular matrix (dECM) coating on its surface, thus creating the PET/PDA/dECM three-dimensional (3D) composite carrier. Subsequently, material characterization of the cellular carriers was conducted, followed by co-culturing with human umbilical cord mesenchymal stem cells in vitro, aiming to investigate the material's impact on the proliferation and paracrine activity of mesenchymal stem cells. Results and Discussion: Material characterization demonstrated successful grafting of PDA and dECM materials, and it had complete hydrophilicity, high porosity, and excellent mechanical properties. The material was rich in various ECM proteins (collagen I, collagen IV , laminin, fibronectin, elastin), indicating good biocompatibility. In long-term in vitro cultivation (14 days) experiments, the PET/PDA/dECM three-dimensional composite carrier significantly enhanced adhesion and proliferation of human umbilical cord-derived mesenchymal stem cells (HUCMSCs), with a proliferation rate 1.9 times higher than that of cells cultured on tissue culture polystyrene (TCPS) at day 14. Furthermore, it effectively maintained the stem cell characteristics, expressing specific antigens for HUCMSCs. Through qPCR, Western blot, and ELISA experiments, the composite carrier markedly promoted the expression and secretion of key cell factors in HUCMSCs. These results demonstrate that the PET/PDA/dECM composite carrier holds great potential for scaling up MSCs' long-term in vitro cultivation and the production of paracrine factors.

Body fluid-derived stem cells - an untapped stem cell source in genitourinary regeneration

Somatic stem cells have been obtained from solid organs and tissues, including the bone marrow, placenta, corneal stroma, periosteum, adipose tissue, dental pulp and skeletal muscle. These solid tissue-derived stem cells are often used for tissue repair, disease modelling and new drug development. In the past two decades, stem cells have also been identified in various body fluids, including urine, peripheral blood, umbilical cord blood, amniotic fluid, synovial fluid, breastmilk and menstrual blood. These body fluid-derived stem cells (BFSCs) have stemness properties comparable to those of other adult stem cells and, similarly to tissue-derived stem cells, show cell surface markers, multi-differentiation potential and immunomodulatory effects. However, BFSCs are more easily accessible through non-invasive or minimally invasive approaches than solid tissue-derived stem cells and can be isolated without enzymatic tissue digestion. Additionally, BFSCs have shown good versatility in repairing genitourinary abnormalities in preclinical models through direct differentiation or paracrine mechanisms such as pro-angiogenic, anti-apoptotic, antifibrotic, anti-oxidant and anti-inflammatory effects. However, optimization of protocols is needed to improve the efficacy and safety of BFSC therapy before therapeutic translation.

Extracellular matrix turnover in salivary gland disorders and regenerative therapies: Obstacles and opportunities

Salivary gland (SG) extracellular matrix (ECM) has a major influence on tissue development, homeostasis, and tissue regeneration after injury. During aging, disease, and physical insult, normal remodeling of the SG microenvironment (i.e. ECM) becomes dysregulated, leading to alterations in matrix composition which disrupt tissue architecture/structure, alter cell activity, and negatively impact gland function. Matrix metalloproteinases (MMPs) are a large and diverse family of metalloendopeptidases which play a major role in matrix degradation and are intimately involved in regulating development and cell function; dysregulation of these enzymes leads to the production of a fibrotic matrix. In the SG this altered fibrotic ECM (or cell microenvironment) negatively impacts normal cell function and the effectiveness of gene and stem cell therapies which serve as a foundation for many SG regenerative therapies. For this reason, prospective regenerative strategies should prioritize the maintenance and/or restoration of a healthy SG ECM. Mesenchymal stem cells (MSCs) have great potential for mitigating damage to the SG microenvironment by ameliorating inflammation, reducing fibrosis, and repairing the damaged milieu of extracellular regulatory cues, including the matrix. This review addresses our current understanding of the impact of aging and disease on the SG microenvironment and suggests critical deficiencies and opportunities in ECM-targeted therapeutic interventions.

Blockade of TGF-β signalling alleviates human adipose stem cell senescence induced by native ECM in obesity visceral white adipose tissue

BACKGROUND

Abdominal obesity is appreciated as a major player in insulin resistance and metabolically dysfunctional adipose tissue. Inappropriate extracellular matrix (ECM) remodelling and functional alterations in human adipose stromal/stem cells (hASCs) have been linked with visceral white adipose tissue (vWAT) dysfunction in obesity. Understanding the interactions between hASCs and the native ECM environment in obese vWAT is required for the development of future therapeutic approaches for obesity-associated metabolic complications.

METHODS

The phenotypes and transcriptome properties of hASCs from the vWAT of obese patients and lean donors were assessed. The hASC-derived matrix from vWAT of obese or lean patients was generated in vitro using a decellularized method. The topography and the major components of the hASC-derived matrix were determined. The effects of the obese hASC-derived matrix on cell senescence and mitochondrial function were further determined.

RESULTS

We showed that hASCs derived from the vWAT of obese patients exhibited senescence and were accompanied by the increased production of ECM. The matrix secreted by obese hASCs formed a fibrillar suprastructure with an abundance of fibronectin, type I collagen, and transforming growth factor beta 1 (TGF-β1), which resembles the native matrix microenvironment of hASCs in vWAT derived from obese patients. Furthermore, the obese hASC-derived matrix promoted lean hASC ageing and induced mitochondrial dysfunction compared to the lean hASC-derived matrix. Blockade of TGF-β1 signalling using an anti-TGF-β1 neutralizing antibody alleviated the lean hASC senescence and mitochondrial dysfunction induced by the obese hASC-derived matrix.

CONCLUSIONS

Native ECM in obesity vWAT initiates hASC senescence through TGF-β1-mediated mitochondrial dysfunction. These data provide a key mechanism for understanding the importance of cell-ECM interactions in hASCs senescence in obesity.

Autologous mesenchymal stem cells offer a new paradigm for salivary gland regeneration

Salivary gland (SG) dysfunction, due to radiotherapy, disease, or aging, is a clinical manifestation that has the potential to cause severe oral and/or systemic diseases and compromise quality of life. Currently, the standard-of-care for this condition remains palliative. A variety of approaches have been employed to restore saliva production, but they have largely failed due to damage to both secretory cells and the extracellular matrix (niche). Transplantation of allogeneic cells from healthy donors has been suggested as a potential solution, but no definitive population of SG stem cells, capable of regenerating the gland, has been identified. Alternatively, mesenchymal stem cells (MSCs) are abundant, well characterized, and during SG development/homeostasis engage in signaling crosstalk with the SG epithelium. Further, the trans-differentiation potential of these cells and their ability to regenerate SG tissues have been demonstrated. However, recent findings suggest that the "immuno-privileged" status of allogeneic adult MSCs may not reflect their status post-transplantation. In contrast, autologous MSCs can be recovered from healthy tissues and do not present a challenge to the recipient's immune system. With recent advances in our ability to expand MSCs in vitro on tissue-specific matrices, autologous MSCs may offer a new therapeutic paradigm for restoration of SG function.

Bovine Fibroblast-Derived Extracellular Matrix Promotes the Growth and Preserves the Stemness of Bovine Stromal Cells during In Vitro Expansion

Cultivated meat is a fast-growing research field and an industry with great potential to overcome the limitations of traditional meat production. Cultivated meat utilizes cell culture and tissue engineering technologies to culture a vast number of cells in vitro and grow/assemble them into structures mimicking the muscle tissues of livestock animals. Stem cells with self-renewal and lineage-specific differentiation abilities have been considered one of the key cell sources for cultivated meats. However, the extensive in vitro culturing/expansion of stem cells results in a reduction in their abilities to proliferate and differentiate. Extracellular matrix (ECM) has been used as a culturing substrate to support cell expansion for cell-based therapies in regenerative medicine due to its resemblance to the native microenvironment of cells. In this study, the effect of the ECM on the expansion of bovine umbilical cord stromal cells (BUSC) in vitro was evaluated and characterized. BUSCs with multi-lineage differentiation potentials were isolated from bovine placental tissue. Decellularized ECM prepared from a confluent monolayer of bovine fibroblasts (BF) is free of cellular components but contains major ECM proteins such as fibronectin and type I collagen and ECM-associated growth factors. Expansion of BUSC on ECM for three passages (around three weeks) resulted in about 500-fold amplification, while cells were amplified less than 10-fold when cultured on standard tissue culture plates (TCP). Moreover, the presence of ECM reduced the requirement for serum in the culture medium. Importantly, the cells amplified on ECM retained their differentiation abilities better than cells cultured on TCP. The results of our study support the notion that monolayer cell-derived ECM may be a strategy to expand bovine cells in vitro effectively and efficiently.

Intraarticular Injections of Mesenchymal Stem Cells in Knee Osteoarthritis: A Review of Their Current Molecular Mechanisms of Action and Their Efficacy

More than 10% of the world's population suffers from osteoarthritis (OA) of the knee, with a lifetime risk of 45%. Current treatments for knee OA pain are as follows: weight control; oral pharmacological treatment (non-steroidal anti-inflammatory drugs, paracetamol, opioids); mechanical aids (crutches, walkers, braces, orthotics); therapeutic physical exercise; and intraarticular injections of corticosteroids, hyaluronic acid, and platelet-rich plasma (PRP). The problem is that such treatments usually relieve joint pain for only a short period of time. With respect to intraarticular injections, corticosteroids relieve pain for several weeks, while hyaluronic acid and PRP relieve pain for several months. When the above treatments fail to control knee pain, total knee arthroplasty (TKA) is usually indicated; however, although a very effective surgical technique, it can be associated with medical and postoperative (surgery-related) complications. Therefore, it seems essential to look for safe and effective alternative treatments to TKA. Recently, there has been much research on intraarticular injections of mesenchymal stem cells (MSCs) for the management of OA of the knee joint. This article reviews the latest information on the molecular mechanisms of action of MSCs and their potential therapeutic benefit in clinical practice in patients with painful knee OA. Although most recent publications claim that intraarticular injections of MSCs relieve joint pain in the short term, their efficacy remains controversial given that the existing scientific information on MSCs is indecisive. Before recommending intraarticular MSCs injections routinely in patients with painful knee OA, more studies comparing MSCs with placebo are needed. Furthermore, a standard protocol for intraarticular injections of MSCs in knee OA is needed.

Engineering hypertrophic cartilage grafts from lipoaspirate for critical-sized calvarial bone defect reconstruction: An adipose tissue-based developmental engineering approach

Developmental engineering of living implants from different cell sources capable of stimulating bone regeneration by recapitulating endochondral ossification (ECO) is a promising strategy for large bone defect reconstruction. However, the clinical translation of these cell-based approaches is hampered by complex manufacturing procedures, poor cell differentiation potential, and limited predictive in vivo performance. We developed an adipose tissue-based developmental engineering approach to overcome these hurdles using hypertrophic cartilaginous (HyC) constructs engineered from lipoaspirate to repair large bone defects. The engineered HyC constructs were implanted into 4-mm calvarial defects in nude rats and compared with decellularized bone matrix (DBM) grafts. The DBM grafts induced neo-bone formation via the recruitment of host cells, while the HyC pellets supported bone regeneration via ECO, as evidenced by the presence of remaining cartilage analog and human NuMA-positive cells within the newly formed bone. However, the HyC pellets clearly showed superior regenerative capacity compared with that of the DBM grafts, yielding more new bone formation, higher blood vessel density, and better integration with adjacent native bone. We speculate that this effect arises from vascular endothelial growth factor and bone morphogenetic protein-2 secretion and mineral deposition in the HyC pellets before implantation, promoting increased vascularization and bone formation upon implantation. The results of this study demonstrate that adipose-derived HyC constructs can effectively heal large bone defects and present a translatable therapeutic option for bone defect repair.

Optimization of human umbilical cord blood-derived mesenchymal stem cell isolation and culture methods in serum- and xeno-free conditions

BACKGROUND

Although umbilical cord blood (UCB) is identified as a source of mesenchymal stem cells (MSCs) with various advantages, the success in cell isolation is volatile. Therefore, it is necessary to optimize methods of cord blood-derived MSC (UCB-MSC) isolation and culture. In this study, we evaluated the efficiency of UCB-MSC isolation and expansion using different commercially available serum- and xeno-free media and investigated the capacity of autologous serum and plasma as a supplement to support cell proliferation. Additionally, we defined the presence of multilineage-differentiating stress-enduring (Muse) cells in the UCB-MSC population. Functions of UCB-MSC in in vitro angiogenesis processes and anti-cancer were also verified.

METHODS

Mononuclear cells were isolated using density gradient separation and cultured in four commercial media kits, as well as four surface coating solutions. UCB-MSCs were characterized and tested on tube formation assay, and co-cultured with SK-MEL cells in a transwell system.

RESULTS

The results showed that only StemMACS™ MSC Expansion Media is more appropriate to isolate and culture UCB-MSCs. The cells exhibited a high cell proliferation rate, CFU forming capability, MSC surface marker expression, trilineage differentiate potential, and chromosome stability. In addition, the culture conditions with autologous serum coating and autologous plasma supplement enhanced cell growth and colony forming. This cell population contained Muse cells at rate of 0.3%. Moreover, UCB-MSCs could induce the tube formation of human umbilical vein endothelial cells and inhibit more than 50% of SK-MEL cell growth.

CONCLUSIONS

UCB-MSCs could be high-yield isolated and expanded under serum- and xeno-free conditions by using the StemMACS™ MSC Expansion Media kit. Autologous serum coating and plasma supplement enhanced cell proliferation. These UCB-MSCs had effected the tube formation process and an anti-cancer impact.

Autologous decellularized extracellular matrix promotes adipogenic differentiation of adipose derived stem cells in low serum culture system by regulating the ERK1/2-PPARγ pathway

High viability and further adipogenic differentiation of adipose-derived stem cells (ADSCs) are fundamental for engraftment and growth of the transplanted adipose tissue. It has been demonstrated that extracellular matrix (ECM) regulates cell proliferation and differentiation by interacting with ERK1/2 signalling pathway. In this study, we prepared autologous decellularized extracellular matrix (d-ECM) and explored its effect on the proliferation and adipogenic ability of ADSCs in low serum culture. We found that 2% foetal bovine serum (FBS) in growth medium inhibited cell viability and DNA replication, and decreased mRNA and protein levels of PPARγ and C/EPBα compared with 10% FBS. Correspondingly, after 14-days adipogenic induction, cells cultured in 2% FBS possessed lower efficiency of adipogenesis and expressed less adipocyte differentiation markers ADIPOQ and aP2. On the contrary, the d-ECM-coated substrate continuously promoted the expression of PPARγ, and regulated the phosphorylation of ERK1/2 in different manners during differentiation. Pretreatment with ERK1/2 inhibitor PD98059 neutralized the effects of d-ECM, which suggested d-ECM might regulate the adipogenesis of ADSCs through ERK1/2-PPARγ pathway. In addition, d-ECM was revealed to regulate the transcription and expression of stemness-associated genes, such as OCT4, NANOG and SOX2, in the undifferentiated ADSCs, which might be related to the initiation of differentiation.

Cell-derived extracellular matrix materials for tissue engineering

The involvement of cell-derived extracellular matrix (CDM) in assembling tissue engineering scaffolds has yielded significant results. CDM possesses excellent characteristics, such as ideal cellular microenvironment mimicry and good biocompatibility, which make it a popular research direction in the field of bionanomaterials. CDM has significant advantages as an expansion culture substrate for stem cells, including stabilization of phenotype, reversal of senescence, and guidance of specific differentiation. In addition, the applications of CDM-assembled tissue engineering scaffolds for disease simulation and tissue organ repair are comprehensively summarized; the focus is mainly on bone and cartilage repair, skin defect or wound healing, engineered blood vessels, peripheral nerves, and periodontal tissue repair. We consider CDM a highly promising bionic biomaterial for tissue engineering applications and propose a vision for its comprehensive development.

A Chemically Defined, Xeno- and Blood-Free Culture Medium Sustains Increased Production of Small Extracellular Vesicles From Mesenchymal Stem Cells

Cell therapy is witnessing a notable shift toward cell-free treatments based on paracrine factors, in particular, towards small extracellular vesicles (sEV), that mimic the functional effect of the parental cells. While numerous sEV-based applications are currently in advanced preclinical stages, their promised translation depends on overcoming the manufacturing hurdles posed by the large-scale production of purified sEV. Unquestionably, the culture medium used with the parental cells plays a key role in the sEV's secretion rate and content. An essential requisite is the use of a serum-, xeno-, and blood-free medium to meet the regulatory entity requirements of clinical-grade sEV's production. Here, we evaluated Oxium^TMEXO, a regulatory complying medium, with respect to production capacity and conservation of the EV's characteristics and functionality and the parental cell's phenotype and viability. A comparative study was established with standard DMEM and a commercially available culture medium developed specifically for sEV production. Under similar conditions, Oxium^TMEXO displayed a three-fold increase of sEV secretion, with an enrichment of particles ranging between 51 and 200 nm. These results were obtained through direct quantification from the conditioned medium to avoid the isolation method's interference and variability and were compared to the two culture media under evaluation. The higher yield obtained was consistent with several harvest time points (2, 4, and 6 days) and different cell sources, incluiding umbilical cord-, menstrual blood-derived mesenchymal stromal cells and fibroblasts. Additionally, the stem cell phenotype and viability of the parental cell remained unchanged. Furthermore, Oxium^TMEXO-sEV showed a similar expression pattern of the vesicular markers CD63, CD9, and CD81, with respect to sEV derived from the other conditions. The in vitro internalization assays in different target cell types and the pharmacokinetic profile of intraperitoneally administered sEV in vivo indicated that the higher EV production rate did not affect the uptake kinetics or the systemic biodistribution in healthy mice. In conclusion, the Oxium^TMEXO medium sustains an efficient and robust production of large quantities of sEV, conserving the classic functional properties of internalization into acceptor target cells and biodistribution in vivo, supplying the amount and quality of EVs for the development of cell-free therapies.

Impact of Three Different Serum Sources on Functional Properties of Equine Mesenchymal Stromal Cells

Culture and expansion of equine mesenchymal stromal cells (MSCs) are routinely performed using fetal bovine serum (FBS) as a source of growth factors, nutrients, and extracellular matrix proteins. However, the desire to minimize introduction of xenogeneic bovine proteins or pathogens and to standardize cellular products intended for clinical application has driven evaluation of alternatives to FBS. Replacement of FBS in culture for several days before administration has been proposed to reduce antigenicity and potentially prolong survival after injection. However, the functional consequences of MSC culture in different serum types have not been fully evaluated. The objective of this study was to compare the immunomodulatory and antibacterial properties of MSCs cultured in three serum sources: FBS or autologous or allogeneic equine serum. We hypothesized that continuous culture in FBS would generate MSCs with improved functionality compared to equine serum and that there would not be important differences between MSCs cultured in autologous vs. allogeneic equine serum. To address these questions, MSCs from three healthy donor horses were expanded in medium with FBS and then switched to culture in FBS or autologous or allogeneic equine serum for 72 h. The impact of this 72-h culture period in different sera on cell viability, cell doubling time, cell morphology, bactericidal capability, chondrogenic differentiation, and production of cytokines and antimicrobial peptides was assessed. Altering serum source did not affect cell viability or morphology. However, cells cultured in FBS had shorter cell doubling times and secreted more interleukin 4 (IL-4), IL-5, IL-17, RANTES, granulocyte–macrophage colony-stimulating factor, fibroblast growth factor 2, eotaxin, and antimicrobial peptide cathelicidin/LL-37 than cells cultured in either source of equine serum. Cells cultured in FBS also exhibited greater spontaneous bactericidal activity. Notably, significant differences in any of these parameters were not observed when autologous vs. allogeneic equine serum was used for cell culture. Chondrogenic differentiation was not different between different serum sources. These results indicate that MSC culture in FBS will generate more functional cells based on a number of parameters and that the theoretical risks of FBS use in MSC culture should be weighed against the loss of MSC function likely to be incurred from culture in equine serum.

Regeneration enhanced in critical-sized bone defects using bone-specific extracellular matrix protein

Extracellular matrix (ECM) products have the potential to improve cellular attachment and promote tissue-specific development by mimicking the native cellular niche. In this study, the therapeutic efficacy of an ECM substratum produced by bone marrow stem cells (BM-MSCs) to promote bone regeneration in vitro and in vivo were evaluated. Fluorescence-activated cell sorting analysis and phenotypic expression were employed to characterize the in vitro BM-MSC response to bone marrow specific ECM (BM-ECM). BM-ECM encouraged cell proliferation and stemness maintenance. The efficacy of BM-ECM as an adjuvant in promoting bone regeneration was evaluated in an orthotopic, segmental critical-sized bone defect in the rat femur over 8 weeks. The groups evaluated were either untreated (negative control); packed with calcium phosphate granules or granules+BM-ECM free protein and stabilized by collagenous membrane. Bone regeneration in vivo was analyzed using microcomputed tomography and histology. in vivo results demonstrated improvements in mineralization, osteogenesis, and tissue infiltration (114 ± 15% increase) in the BM-ECM complex group from 4 to 8 weeks compared to mineral granules only (45 ± 21% increase). Histological observations suggested direct apposition of early bone after 4 weeks and mineral consolidation after 8 weeks implantation for the group supplemented with BM-ECM. Significant osteoid formation and greater functional bone formation (polar moment of inertia was 71 ± 0.2 mm4 with BM-ECM supplementation compared to 48 ± 0.2 mm4 in untreated defects) validated in vivo indicated support of osteoconductivity and increased defect site cellularity. In conclusion, these results suggest that BM-ECM free protein is potentially a therapeutic supplement for stemness maintenance and sustaining osteogenesis.

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.

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.

Extracellular matrix-derived biomaterials in engineering cell function

Extracellular matrix (ECM) derived components are emerging sources for the engineering of biomaterials that are capable of inducing desirable cell-specific responses. This review explores the use of biomaterials derived from naturally occurring ECM proteins and their derivatives in approaches that aim to regulate cell function. Biomaterials addressed are grouped into six categories: purified single ECM proteins, combinations of purified ECM proteins, cell-derived ECM, tissue-derived ECM, diseased and modified ECM, and ECM-polymer coupled biomaterials. Purified ECM proteins serve as a material coating for enhanced cell adhesion and biocompatibility. Cell-derived and tissue-derived ECM, generated by cell isolation and decellularization technologies, can capture the native state of the ECM environment and guide cell migration and alignment patterns as well as stem cell differentiation. We focus primarily on recent advances in the fields of soft tissue, cardiac, and dermal repair, and explore the utilization of ECM proteins as biomaterials to engineer cell responses.

Type I collagen facilitates safe and reliable expansion of human dental pulp stem cells in xenogeneic serum-free culture

BACKGROUND

Human dental pulp stem cells (DPSCs) are a readily accessible and promising cell source for regenerative medicine. We recently reported that a xenogeneic serum-free culture medium (XFM) is preferable to fetal bovine serum-containing culture medium for ex vivo expansion of DPSCs; however, we observed that, upon reaching overconfluence, XFM cells developed a multilayered structure and frequently underwent apoptotic death, resulting in reduced cell yield. Therefore, we focused on optimization of the XFM culture system to avoid the undesirable death of DPSCs.

METHODS

We selected type I collagen (COL) as the optimal coating substrate for the cultureware and compared DPSCs cultured on COL in XFM (COL-XFM cells) to the conventional XFM cultures (XFM cells).

RESULTS

Our results demonstrated that COL coating facilitated significantly higher rates of cell isolation and growth; upon reaching overconfluence, cell survival and sustained proliferative potential resulted in two-fold yield compared to the XFM cells. Surprisingly, after subculturing the overconfluent COL-XFM cultures, the cells retained stem cell behavior including stable cell growth, multidifferentiation potential, stem cell phenotype, and chromosomal stability, which was achieved through HIF-1α-dependent production and uniform distribution of collagen type I and its interactions with integrins α2β1 and α11β1 at overconfluency. In contrast, cells undergoing apoptotic death within overconfluent XFM cultures had disorganized mitochondria with membrane depolarization.

CONCLUSION

The use of COL as a coating substrate promises safe and reliable handling of DPSCs in XFM culture, allowing translational stem cell medicine to achieve stable isolation, expansion, and banking of donor-derived stem cells.

Native extracellular matrix, synthesized ex vivo by bone marrow or adipose stromal cells, faithfully directs mesenchymal stem cell differentiation

Mesenchymal stem cells (MSCs) are highly responsive to cues in the microenvironment (niche) that must be recapitulated ex vivo to study their authentic behavior. In this study, we hypothesized that native bone marrow (BM)- and adipose (AD)-derived extracellular matrices (ECM) were unique in their ability to control MSC behavior. To test this, we compared proliferation and differentiation of bone marrow (BM)-derived MSCs when maintained on native decellularized ECM produced by BM versus AD stromal cells (i.e. BM- versus AD-ECM). We found that both ECMs contained similar types of collagens but differed in the relative abundance of each. Type VI collagen was the most abundant (≈60% of the total collagen present), while type I was the next most abundant at ≈30%. These two types of collagen were found in nearly equal proportions in both ECMs. In contrast, type XII collagen was almost exclusively found in AD-ECM, while types IV and V were only found in BM-ECM. Physically and mechanically, BM-ECM was rougher and stiffer, but less adhesive, than AD-ECM. During 14 days in culture, both ECMs supported BM-MSC proliferation better than tissue culture plastic (TCP), although MSC-related surface marker expression remained relatively high on all three culture surfaces. BM-MSCs cultured in osteogenic (OS) differentiation media on BM-ECM displayed a significant increase in calcium deposition in the matrix, indicative of osteogenesis, while BM-MSCs cultured on AD-ECM in the presence of adipogenic (AP) differentiation media showed a significant increase in Oil Red O staining, indicative of adipogenesis. Further, culture on BM-ECM significantly increased BM-MSC-responsiveness to rhBMP-2 (an osteogenic inducer), while culture on AD-ECM enhanced responsiveness to rosiglitazone (an adipogenic inducer). These findings support our hypothesis and indicate that BM- and AD-ECMs retain unique elements, characteristic of their tissue-specific microenvironment (niche), which promote retention of MSC differentiation state (i.e. "stemness") during expansion and direct cell response to lineage-specific inducers. This study provides a new paradigm for precisely controlling MSC fate to a desired cell lineage for tissue-specific cell-based therapies.

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.

Matrix mechanics and water permeation regulate extracellular vesicle transport

Cells release extracellular vesicles (EVs) to communicate over long distances, which requires EVs to traverse the extracellular matrix (ECM). However, given that the size of EVs is usually larger than the mesh size of the ECM, it is not clear how they can travel through the dense ECM. Here we show that, in contrast to synthetic nanoparticles, EVs readily transport through nanoporous ECM. Using engineered hydrogels, we demonstrate that the mechanical properties of the matrix regulate anomalous EV transport under confinement. Matrix stress relaxation allows EVs to overcome the confinement, and a higher crosslinking density facilitates a fluctuating transport motion through the polymer mesh, which leads to free diffusion and fast transport. Furthermore, water permeation through aquaporin-1 mediates the EV deformability, which further supports EV transport in hydrogels and a decellularized matrix. Our results provide evidence for the nature of EV transport within confined environments and demonstrate an unexpected dependence on matrix mechanics and water permeation.

In Vitro Expansion of Keratinocytes on Human Dermal Fibroblast-Derived Matrix Retains Their Stem-Like Characteristics

The long-term expansion of keratinocytes under conditions that avoid xenogeneic components (i.e. animal serum- and feeder cell-free) generally causes diminished proliferation and increased terminal differentiation. Here we present a culture system free of xenogeneic components that retains the self-renewal capacity of primary human keratinocytes. In vivo the extracellular matrix (ECM) of the tissue microenvironment has a major influence on a cell's fate. We used ECM from human dermal fibroblasts, cultured under macromolecular crowding conditions to facilitate matrix deposition and organisation, in a xenogeneic-free keratinocyte expansion protocol. Phospholipase A2 decellularisation produced ECM whose components resembled the core matrix composition of natural dermis by proteome analyses. Keratinocytes proliferated rapidly on these matrices, retained their small size, expressed p63, lacked keratin 10 and rarely expressed keratin 16. The colony forming efficiency of these keratinocytes was enhanced over that of keratinocytes grown on collagen I, indicating that dermal fibroblast-derived matrices maintain the in vitro expansion of keratinocytes in a stem-like state. Keratinocyte sheets formed on such matrices were multi-layered with superior strength and stability compared to the single-layered sheets formed on collagen I. Thus, keratinocytes expanded using our xenogeneic-free protocol retained a stem-like state, but when triggered by confluence and calcium concentration, they stratified to produce epidermal sheets with a potential clinical use.

Mesenchymal Stromal Cell-Based Bone Regeneration Therapies: From Cell Transplantation and Tissue Engineering to Therapeutic Secretomes and Extracellular Vesicles

Effective regeneration of bone defects often presents significant challenges, particularly in patients with decreased tissue regeneration capacity due to extensive trauma, disease, and/or advanced age. A number of studies have focused on enhancing bone regeneration by applying mesenchymal stromal cells (MSCs) or MSC-based bone tissue engineering strategies. However, translation of these approaches from basic research findings to clinical use has been hampered by the limited understanding of MSC therapeutic actions and complexities, as well as costs related to the manufacturing, regulatory approval, and clinical use of living cells and engineered tissues. More recently, a shift from the view of MSCs directly contributing to tissue regeneration toward appreciating MSCs as "cell factories" that secrete a variety of bioactive molecules and extracellular vesicles with trophic and immunomodulatory activities has steered research into new MSC-based, "cell-free" therapeutic modalities. The current review recapitulates recent developments, challenges, and future perspectives of these various MSC-based bone tissue engineering and regeneration strategies.

Recent Trends in Decellularized Extracellular Matrix Bioinks for 3D Printing: An Updated Review

The promise of regenerative medicine and tissue engineering is founded on the ability to regenerate diseased or damaged tissues and organs into functional tissues and organs or the creation of new tissues and organs altogether. In theory, damaged and diseased tissues and organs can be regenerated or created using different configurations and combinations of extracellular matrix (ECM), cells, and inductive biomolecules. Regenerative medicine and tissue engineering can allow the improvement of patients' quality of life through availing novel treatment options. The coupling of regenerative medicine and tissue engineering with 3D printing, big data, and computational algorithms is revolutionizing the treatment of patients in a huge way. 3D bioprinting allows the proper placement of cells and ECMs, allowing the recapitulation of native microenvironments of tissues and organs. 3D bioprinting utilizes different bioinks made up of different formulations of ECM/biomaterials, biomolecules, and even cells. The choice of the bioink used during 3D bioprinting is very important as properties such as printability, compatibility, and physical strength influence the final construct printed. The extracellular matrix (ECM) provides both physical and mechanical microenvironment needed by cells to survive and proliferate. Decellularized ECM bioink contains biochemical cues from the original native ECM and also the right proportions of ECM proteins. Different techniques and characterization methods are used to derive bioinks from several tissues and organs and to evaluate their quality. This review discusses the uses of decellularized ECM bioinks and argues that they represent the most biomimetic bioinks available. In addition, we briefly discuss some polymer-based bioinks utilized in 3D bioprinting.

Fabrication and characterization of extracellular matrix scaffolds obtained from adipose-derived stem cells

Chronic non-healing wounds are detrimental for the quality of life of the affected individuals and represent a major burden for the health care systems. Adipose-derived stem cells (ASCs) are being investigated for the development of novel treatments of chronic wounds, as they have shown several positive effects on wound healing. While these effects appear to be mediated by the release of soluble factors, it is has also become apparent that the extracellular matrix (ECM) deposited by ASCs is essential in several phases of the wound healing process. In this work, we describe an approach to produce ECM scaffolds derived from ASCs in culture. Upon growth of ASCs into an overconfluent cell layer, a detergent-based cell extraction approach is applied to remove the cellular components. The extraction is followed by an enzymatic treatment to remove the residual DNA. The resultant cell-derived scaffolds are depleted of cellular components, display low DNA remnant, and retain the native fibrillar organization of the ECM. Analysis of the molecular composition of the ECM scaffolds revealed that they are composed of collagens type I and III, and fibronectin. The decellularized scaffolds represent a substrate that supports adhesion and proliferation of primary human fibroblasts and dermal microvascular endothelial cells, indicating their potential as platforms for wound healing studies.

In vitro simulation of the early proinflammatory phase in fracture healing reveals strong immunomodulatory effects of CD146-positive mesenchymal stromal cells

The impact of microenvironmental cues and changes due to injury on the phenotype and fate of mesenchymal stromal cells (MSCs) is poorly understood. Here, we aimed to simulate the microenvironment associated with the early stage of bone healing in vitro and to study the regenerative response of MSCs. We enriched CD146+ MSCs from the human bone marrow. Different physiological and pathological microenvironments were simulated by using conditioned medium (CM) from human endothelial cells and osteoblasts (healthy bone), femoral head-derived bone fragments (injured bone), and activated platelets (platelet-rich plasma [PRP], injury). Cells were incubated in CM and analyzed with respect to proliferation, gene expression, migration, osteogenic differentiation, and their effect on polyclonally induced proliferation of peripheral blood mononuclear cells. CD146+ MSCs showed a specific response to different microenvironments. Cell proliferation was observed in all media with the highest values in PRP-CM and injured bone-CM. Gene expression analysis revealed the upregulation of chemokines, proinflammatory, proangiogenic, and genes involved in immunomodulation in cells stimulated with PRP- and injured bone-CM, suggesting strong paracrine activity. PRP-CM led to pronounced inhibition of lymphocyte proliferation by CD146+MSCs. Our results indicate that a microenvironment simulating bone injury elicits strong immunomodulatory and proangiogenic activity of CD146+ MSCs. This suggests that in the early stage of bone healing, the prime function of MSCs and their CD146+ subpopulation is in regulating the immune response and inducing neovascularization. Future studies will investigate the key components in CM driving this function, which might be potential targets to therapeutically stimulate the regenerative potential of MSCs.

Soluble matrix protein is a potent modulator of mesenchymal stem cell performance

We challenge the conventional designation of structural matrix proteins primarily as supporting scaffolds for resident cells. The extracellular matrix protein tropoelastin is classically regarded as a structural component that confers mechanical strength and resilience to tissues subject to repetitive elastic deformation. Here we describe how tropoelastin inherently induces a range of biological responses, even in cells not typically associated with elastic tissues and in a manner unexpected of typical substrate-dependent matrix proteins. We show that tropoelastin alone drives mesenchymal stem cell (MSC) proliferation and phenotypic maintenance, akin to the synergistic effects of potent growth factors such as insulin-like growth factor 1 and basic fibroblast growth factor. In addition, tropoelastin functionally surpasses these growth factors, as well as fibronectin, in allowing substantial media serum reduction without loss of proliferative potential. We further demonstrate that tropoelastin elicits strong mitogenic and cell-attractive responses, both as an immobilized substrate and as a soluble additive, via direct interactions with cell surface integrins αvβ3 and αvβ5. This duality of action converges the long-held mechanistic dichotomy between adhesive matrix proteins and soluble growth factors and uncovers the powerful, untapped potential of tropoelastin for clinical MSC expansion and therapeutic MSC recruitment. We propose that the potent, growth factor-like mitogenic and motogenic abilities of tropoelastin are biologically rooted in the need for rapid stem cell homing and proliferation during early development and/or wound repair.

Nucleic acid delivery to mesenchymal stem cells: a review of nonviral methods and applications

Background

Mesenchymal stem cells (MSCs) are multipotent stem cells that can be isolated and expanded from many tissues, and are being investigated for use in cell therapies. Though MSC therapies have demonstrated some success, none have been FDA approved for clinical use. MSCs lose stemness ex vivo, decreasing therapeutic potential, and face additional barriers in vivo, decreasing therapeutic efficacy. Culture optimization and genetic modification of MSCs can overcome these barriers. Viral transduction is efficient, but limited by safety concerns related to mutagenicity of integrating viral vectors and potential immunogenicity of viral antigens. Nonviral delivery methods are safer, though limited by inefficiency and toxicity, and are flexible and scalable, making them attractive for engineering MSC therapies.

Main text

Transfection method and nucleic acid determine efficiency and expression profile in transfection of MSCs. Transfection methods include microinjection, electroporation, and nanocarrier delivery. Microinjection and electroporation are efficient, but are limited by throughput and toxicity. In contrast, a variety of nanocarriers have been demonstrated to transfer nucleic acids into cells, however nanocarrier delivery to MSCs has traditionally been inefficient. To improve efficiency, plasmid sequences can be optimized by choice of promoter, inclusion of DNA targeting sequences, and removal of bacterial elements. Instead of DNA, RNA can be delivered for rapid protein expression or regulation of endogenous gene expression. Beyond choice of nanocarrier and nucleic acid, transfection can be optimized by priming cells with media additives and cell culture surface modifications to modulate barriers of transfection. Media additives known to enhance MSC transfection include glucocorticoids and histone deacetylase inhibitors. Culture surface properties known to modulate MSC transfection include substrate stiffness and specific protein coating. If nonviral gene delivery to MSCs can be sufficiently improved, MSC therapies could be enhanced by transfection for guided differentiation and reprogramming, transplantation survival and directed homing, and secretion of therapeutics. We discuss utilized delivery methods and nucleic acids, and resulting efficiency and outcomes, in transfection of MSCs reported for such applications.

Conclusion

Recent developments in transfection methods, including nanocarrier and nucleic acid technologies, combined with chemical and physical priming of MSCs, may sufficiently improve transfection efficiency, enabling scalable genetic engineering of MSCs, potentially bringing effective MSC therapies to patients.

Fractionated human adipose tissue as a native biomaterial for the generation of a bone organ by endochondral ossification

Many steps are required to generate bone through endochondral ossification with adipose mesenchymal stromal cells (ASC), from cell isolation to in vitro monolayer expansion, seeding into scaffolds, cartilaginous differentiation and in vivo remodeling. Moreover, monolayer expansion and passaging of ASC strongly decreases their differentiation potential. Here, we propose that adipose tissue itself can be used as scaffold for ASC expansion and endochondral ossification. Human liposuctions were fractionated and cultured for 3 weeks with proliferative medium in suspension. The resulting constructs, named Adiscaf, were compared to constructs generated with a previously developed, control approach, i.e. collagen sponges seeded with monolayer-expanded ASC. After 4 weeks of chondrogenic differentiation, Adiscaf contained cartilage tissue, characterized by glycosaminoglycans and collagen type II. After 2 additional weeks of hypertrophic differentiation, Adiscaf showed upregulation of hypertrophic markers at the gene expression and protein levels. After 8 weeks of in vivo implantation, Adiscaf resulted in ectopic bone tissue formation, including bone marrow elements. Adiscaf showed superior in vitro differentiation and in vivo performance as compared to the control paradigm involving isolation and monolayer expansion of ASC. This new paradigm exploits the physiological niche of adipose tissue and strongly suggests a higher functionality of cells inside adipose tissue after in vitro expansion. This study demonstrates that adult human adipose tissue used as a native construct can generate a bone organ by endochondral ossification. The concept could be exploited for the generation of osteogenic grafts for bone repair.

STATEMENT OF SIGNIFICANCE

In this study we used adult human adipose tissue as scaffolding materials (called Adiscaf) to generate a bone organ by endochondral ossification. Adiscaf concept is based on the culture of adipose tissue cells inside their native microenvironment for the generation of osteogenic grafts for bone repair. This simplified approach overcomes several limitations linked to the current techniques in bone tissue engineering, such as isolation of cells and inadequate properties of the biomaterials used as scaffolds. In addition, the present paradigm proposes to exploit physiological niches in order to better maintain the functionality of cells during their in vitro expansion. This project not only has a scientific impact by evaluating the impact of native physiological niches on the functionality and chondrogenic differentiation of mesenchymal progenitors but also a clinical impact to generate osteogenic grafts and/or osteoinductive materials for bone regeneration and repair.

Differential and Interactive Effects of Substrate Topography and Chemistry on Human Mesenchymal Stem Cell Gene Expression

Variations in substrate chemistry and the micro-structure were shown to have a significant effect on the biology of human mesenchymal stromal cells (hMSCs). This occurs when differences in the surface properties indirectly modulate pathways within numerous signaling networks that control cell fate. To understand how the surface features affect hMSC gene expression, we performed RNA-sequencing analysis of bone marrow-derived hMSCs cultured on tissue culture-treated polystyrene (TCP) and poly(l-lactide) (PLLA) based substrates of differing topography (Fl: flat and Fs: fibrous) and chemistry (Pr: pristine and Am: aminated). Whilst 80% of gene expression remained similar for cells cultured on test substrates, the analysis of differentially expressed genes (DEGs) revealed that surface topography significantly altered gene expression more than surface chemistry. The Fl and Fs topologies introduced opposite directional alternations in gene expression when compared to TCP control. In addition, the effect of chemical treatment interacted with that of topography in a synergistic manner with the Pr samples promoting more DEGs than Am samples in all gene ontology function groups. These findings not only highlight the significance of the culture surface on regulating the overall gene expression profile but also provide novel insights into cell-material interactions that could help further design the next-generation biomaterials to facilitate hMSC applications. At the same time, further studies are required to investigate whether or not the observations noted correlate with subsequent protein expression and functionality of cells.

Future Research Directions in the Design of Versatile Extracellular Matrix in Tissue Engineering

Native and artificial extracellular matrices (ECMs) have been widely applied in biomedical fields as one of the most effective components in tissue regeneration. In particular, ECM-based drugs are expected to be applied to treat diseases in organs relevant to urology, because tissue regeneration is particularly important for preventing the recurrence of these diseases. Native ECMs provide a complex in vivo architecture and native physical and mechanical properties that support high biocompatibility. However, the applications of native ECMs are limited due to their tissue-specificity and chemical complexity. Artificial ECMs have been fabricated in an attempt to create a broadly applicable scaffold by using controllable components and a uniform formulation. On the other hands, artificial ECMs fail to mimic the properties of a native ECM; consequently, their applications in tissues are also limited. For that reason, the design of a versatile, hybrid ECM that can be universally applied to various tissues is an emerging area of interest in the biomedical field.

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.

Glial differentiation of human inferior turbinate-derived stem cells: a new source of cells for nerve repair

Schwann cell (SC) transplantation as a cell-based therapy can enhance peripheral and central nerve repair experimentally, but it is limited by donor site morbidity for clinical application. We investigated whether human turbinate-derived mesenchymal stem cells (hTMSCs) isolated from discarded inferior turbinate during surgery can differentiate into functional SC-like cells. hTMSCs expressed mesenchymal cell surface markers CD29, CD44, CD90, and CD105 and did not express neural crest markers P75 and Nestin. After monolayer culture in predifferentiation medium and transdifferentiation medium with a mixture of glial growth factors and chemical regents for 14 days, the differentiated hTMSCs exhibited a spindle-like morphology similar to that of SCs. RT-PCR, immunocytochemical staining, and western blotting analysis indicated that SC-like cells expressed the glial markers S100β, P75, and glial fibrillary acidic protein at the gene and protein level. Compared with hTMSCs, differentiated hTMSCs secreted more neurotrophins, and significantly enhanced the neurite length when cocultured with dorsal root ganglia neuronal cells. Our data indicated that hTMSCs can differentiate into functional SC-like cells and have the ability to facilitate the neurite growth of dorsal root ganglia neuronal cells in vitro, representing a promising source of cells for nerve repair.

3D Decellularized Native Extracellular Matrix Scaffold for In Vitro Culture Expansion of Human Wharton's Jelly-Derived Mesenchymal Stem Cells (hWJ MSCs)

Mesenchymal stem cells (MSCs) are derived from Wharton's jelly tissue of the human umbilical cord. Given appropriate culture conditions, these cells can self-renew and differentiate into multiple cell types across the lineages. Among the properties exhibited by these cells, immunomodulation through secretion of trophic factors has been widely exploited in a broad spectrum of preclinical/clinical regenerative applications. Moreover, the extracellular matrix is found to play a major role apart from niche cells in determining stem cell fate including that of MSCs. Therefore, the currently employed technique of two-dimensional culture expansion can alter the inherent properties of naïve MSCs originally residing within the three-dimensional space. This limitation can be overcome to some extent by using native extracellular matrix scaffold culture system which mimics the in situ microenvironment. In this chapter, we have elucidated the protocol for the preparation of a native extracellular matrix scaffold by decellularization of the MSC sheet and thereof culture expansion and characterization of human Wharton's jelly-derived MSCs.

Restoring the quantity and quality of elderly human mesenchymal stem cells for autologous cell-based therapies

BACKGROUND

Degenerative diseases are a major public health concern for the aging population and mesenchymal stem cells (MSCs) have great potential for treating many of these diseases. However, the quantity and quality of MSCs declines with aging, limiting the potential efficacy of autologous MSCs for treating the elderly population.

METHODS

Human bone marrow (BM)-derived MSCs from young and elderly donors were obtained and characterized using standard cell surface marker criteria (CD73, CD90, CD105) as recommended by the International Society for Cellular Therapy (ISCT). The elderly MSC population was isolated into four subpopulations based on size and stage-specific embryonic antigen-4 (SSEA-4) expression using fluorescence-activated cell sorting (FACS), and subpopulations were compared to the unfractionated young and elderly MSCs using assays that evaluate MSC proliferation, quality, morphology, intracellular reactive oxygen species, β-galactosidase expression, and adenosine triphosphate (ATP) content.

RESULTS

The ISCT-recommended cell surface markers failed to detect any differences between young and elderly MSCs. Here, we report that elderly MSCs were larger in size and displayed substantially higher concentrations of intracellular reactive oxygen species and β-galactosidase expression and lower amounts of ATP and SSEA-4 expression. Based on these findings, cell size and SSEA-4 expression were used to separate the elderly MSCs into four subpopulations by FACS. The original populations (young and elderly MSCs), as well as the four subpopulations, were then characterized before and after culture on tissue culture plastic and BM-derived extracellular matrix (BM-ECM). The small SSEA-4-positive subpopulation representing ~ 8% of the original elderly MSC population exhibited a "youthful" phenotype that was similar to that of young MSCs. The biological activity of this elderly subpopulation was inhibited by senescence-associated factors produced by the unfractionated parent population. After these "youthful" cells were isolated and expanded (three passages) on a "young microenvironment" (i.e., BM-ECM produced by BM cells from young donors), the number of cells increased ≈ 17,000-fold to 3 × 10⁹ cells and retained their "youthful" phenotype.

CONCLUSIONS

These results suggest that it is feasible to obtain large numbers of high-quality autologous MSCs from the elderly population and establish personal stem cell banks that will allow serial infusions of "rejuvenated" MSCs for treating age-related diseases.

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.

Evaluation of characteristic of human turbinate derived mesenchymal stem cells cultured in the serum free media

We evaluated the effect of serum-free and xeno-cultivation (SFXFM) on the characterization, proliferation, and differentiation properties of human nasal stem cells (airway tissue; hTMSCs). hTMSCs were isolated from 10 patients, after which patient samples were separated into two groups, an SFXFM group and a control group. The control group was treated with bovine serum-containing medium. FACS analysis revealed that SFXFM-cultured hTMSCs maintained a characteristic mesenchymal stem cell phenotype. hTMSC proliferation was not influenced by SFXFM. In addition, upregulation of IL-8 and GM-CSF and downregulation of RANTES expression were shown in response to SFXFM. Moreover, two-lineage differentiation properties (osteocyte and adipocyte) of hTMSCs were enhanced under SFXFM. Finally, the genetic stability of SFXFM-cultured hTMSCs was demonstrated by normal karyotype results. SFXFM enables good expansion, multipotentiality, and normal genotype maintenance of MSCs. Moreover, this approach serves as a substitute to conventional media for the cultivation of capable MSCs for upcoming medical applications.

Microenvironmental factors that regulate mesenchymal stem cells: lessons learned from the study of heterotopic ossification

Bone marrow contains a non-hematopoietic, clonogenic, multipotent population of stromal cells that are later called mesenchymal stem cells (MSC). Similar cells that share many common features with MSC are also found in other organs, which are thought to contribute both to normal tissue regeneration and to pathological processes such as heterotopic ossification (HO), the formation of ectopic bone in soft tissue. Understanding the microenvironmental factors that regulate MSC in vivo is essential both for understanding the biology of the stem cells and for effective translational applications of MSC. Unfortunately, this important aspect has been largely underappreciated. This review tries to raise the attention and highlight this critical issue by updating the relevant literature along with discussions of the key issues in the area.