Bioactive Decellularized Extracellular Matrix Derived from 3D Stem Cell Spheroids under Macromolecular Crowding Serves as a Scaffold for Tissue Engineering

Tailoring the therapeutic potential of stem cell spheroid-derived decellularized ECM through post-decellularization BDNF incorporation to enhance brain repair

Decellularized extracellular matrix (dECM) from tissues has significant therapeutic potential but is limited by its rigid molecular composition and reliance on post-decellularization modifications to tailor its functionality. Harsh decellularization processes often result in substantial glycosaminoglycan (GAG) loss, impairing natural growth factor incorporation and necessitating chemical modifications that complicate processing and limit clinical translation. To address these challenges, we developed mesenchymal stem cell (MSC) spheroid-derived three-dimensional (3D) dECM using gentle decellularization techniques. This study demonstrated a crucial advancement-the retention of endogenous GAGs-enabling direct growth factor incorporation without chemical agents. As a proof-of-concept, brain-derived neurotrophic factor (BDNF) was incorporated into the 3D dECM to enhance its therapeutic potential for brain repair. In vitro, BDNF-loaded 3D dECM enabled sustained growth factor release, significantly enhancing the proneuritogenic, neuroprotective, and proangiogenic effects. In a mouse model of traumatic brain injury, the implantation of BDNF-loaded 3D dECM significantly enhanced motor function and facilitated brain repair. These findings highlight the adaptability of MSC spheroid-derived 3D dECM for tissue-specific customization through straightforward and translatable growth factor incorporation, demonstrating its potential as a pro-regenerative biomaterial for advancing regenerative medicine applications.

Advances in abiotic tissue-based biomaterials: A focus on decellularization and devitalization techniques

This Review explores the growing and diversifying field of tissue-derived abiotic constructs for tissue engineering applications, with main focus on decellularization and devitalization techniques and principles. Acellular fractions derived from biological tissues, such as the extracellular matrix (ECM), have long been considered a valuable approach for the generation of numerous scaffolds and more complex constructs. The removal of the cellular content has been considered essential to prevent the development of adverse immunological reactions. Nevertheless, the discovery of promising features of certain cellular components has sparked interest in the use of inactivated or devitalized cellular fractions for several applications, particularly in regenerative medicine and inflammation control. Devitalization has been described for several clinical applications, but remains poorly explored in terms of in vitro constructs compared to decellularization methods currently available. In this review, we present and critically evaluate a spectrum of approaches for the decellularization of whole-organs and in vitro constructs, and the most prevalent devitalization techniques, with a discussion on their implications on scaffolds composition, structure, and potentially therapeutic properties. Processing methodologies to achieve optimal cell-based abiotic materials and approaches for their effective characterization are described and discussed. The application of these materials in healthcare, with most focus on regenerative approaches and including examples of commercially available products, is also addressed.

Assembly of MSCs into a spheroid configuration increases poly(I:C)-mediated TLR3 activation and the immunomodulatory potential of MSCs for alleviating murine colitis

BACKGROUND

Inflammatory bowel disease (IBD) is associated with significant clinical challenges due to the limitations of current therapeutic approaches. Mesenchymal stem cell (MSC)-based therapies have shown promise in alleviating IBD owing to their potent immunomodulatory properties. However, the therapeutic efficacy of these cells remains suboptimal, primarily due to the harsh peritoneal microenvironment, which compromises MSC viability and functional capacity after transplantation.

METHODS

To address these limitations, this study aimed to improve MSC engraftment and functionality by assembling MSCs into three-dimensional (3D) spheroids and priming them with the Toll-like receptor 3 (TLR3) agonist polyinosinic-polycytidylic acid (poly(I:C)). Their potential for treating IBD was evaluated using male C57BL/6 mice with dextran sulfate sodium-induced colitis.

RESULTS

While 3D spheroid formation alone upregulated TLR3 expression and increased MSC survival under oxidative stress, poly(I:C) priming had a pronounced synergistic effect, significantly increasing MSC-mediated splenocyte modulation and oxidative stress resistance. In a murine colitis model, compared with unprimed spheroids or MSC suspensions, poly(I:C)-primed MSC spheroids administered intraperitoneally exhibited increased survival and therapeutic efficacy, effectively alleviating colitis symptoms, reducing colonic inflammation, and promoting tissue recovery.

CONCLUSION

Collectively, these findings highlight the synergistic benefits of combining 3D spheroid assembly with TLR3 activation as an innovative strategy to improve the therapeutic efficacy of MSC-based treatments for IBD and other inflammatory diseases by increasing post-engraftment cell survival and immunomodulatory capacity.

Implantation of MSC spheroid-derived 3D decellularized ECM enriched with the MSC secretome ameliorates traumatic brain injury and promotes brain repair

Traumatic brain injury (TBI) presents substantial clinical challenges, as existing treatments are unable to reverse damage or effectively promote brain tissue regeneration. Although implantable biomaterials have been proposed to support tissue repair by mitigating the adverse microenvironment in injured brains, many fail to replicate the complex composition and architecture of the native extracellular matrix (ECM), resulting in only limited therapeutic outcomes. This study introduces an innovative approach by developing a mesenchymal stem cell (MSC) spheroid-derived three-dimensional (3D) decellularized ECM (dECM) that is enriched with the MSC-derived matrisome and secretome, offering a promising solution for TBI treatment and brain tissue regeneration. Proteomic and cytokine array analyses revealed that 3D dECM retained a diverse array of MSC spheroid-derived matrisome proteins and secretome components, which are crucial for replicating the complexity of native ECM and the therapeutic capabilities of MSCs. These molecules were found to underlie the observed effects of 3D dECM on immunomodulation, proneuritogenesis, and proangiogenesis in our in vitro functional assays. Implantation of 3D dECM into TBI model mice effectively mitigated postinjury tissue damage and promoted brain repair, as evidenced by a reduced brain lesion volume, decreased cell apoptosis, alleviated neuroinflammation, reduced glial scar formation, and increased of neuroblast recruitment to the lesion site. These outcomes culminated in improved motor function recovery in animals, highlighting the multifaceted therapeutic potential of 3D dECM for TBI. In summary, our study elucidates the transformative potential of MSC spheroid-derived bioactive 3D dECM as an implantable biomaterial for effectively mitigating post-TBI neurological damage, paving the way for its broader therapeutic application.

Injectable Glucose-Releasing Microgels Enhance the Survival and Therapeutic Potential of Transplanted MSCs Under Ischemic Conditions

Mesenchymal stem cell (MSC)-based therapies show potential to treat ischemic diseases owing to their versatile functions. However, sustaining MSC viability and therapeutic efficacy in ischemic tissues postengraftment remains a significant challenge. This is because, although MSCs are metabolically flexible, they fail to adapt to hypoxic conditions in the absence of glucose, leading to cell death. To overcome these issues, it is aimed to establish an injectable glucose delivery system using starch and amyloglucosidase embedded in alginate microgels. Here, starch/amyloglucosidase (S/A) microgels are engineered to continuously release glucose for seven days via enzymatic hydrolysis, thereby supporting MSC functions under ischemic conditions. In vitro tests under oxygen/glucose-deprived conditions revealed that the S/A microgels not only maintained the viability and intracellular energy but also enhanced the pro-angiogenic and immunomodulatory functions of MSCs. In vivo data further confirmed the pro-survival and pro-angiogenic effects of S/A microgels on MSCs following subcutaneous engraftment in mice. Overall, the developed S/A microgel significantly enhanced the survival and therapeutic potential of MSCs via sustained glucose delivery, highlighting its potential use in advancing MSC-based therapies for ischemic conditions.

Decellularized Extracellular Matrix Improves Mesenchymal Stromal Cell Spheroid Response to Chondrogenic Stimuli

Cartilage regeneration is hindered due to the low proliferative capacity of chondrocytes and the avascular nature of cartilaginous tissue. Mesenchymal stromal cells (MSCs) are widely studied for cartilage tissue engineering, and the aggregation of MSCs into high-density cell spheroids facilitates chondrogenic differentiation due to increased cell-cell contact. Despite the promise of MSCs, the field would benefit from improved strategies to regulate the chondrogenic potential of MSCs differentiated from induced pluripotent stem cells (iPSCs), which are advantageous for their capacity to yield large numbers of required cells. We previously demonstrated the ability of MSC-secreted extracellular matrix (ECM) to promote MSC chondrogenic differentiation, but the combinatorial effect of iPSC-derived MSC (iMSC) spheroids, iMSC-derived decellularized ECM (idECM), and other stimuli (e.g., oxygen tension and transforming growth factor [TGF]-β) on chondrogenic potential has not been described. Similar to MSCs, iMSCs secreted a collagen-rich ECM. When incorporated into spheroids, idECM increased spheroid diameter and promoted chondrogenic differentiation. The combination of idECM loading, chondrogenic media, and hypoxia enhanced glycosaminoglycan (GAG) content 1.6-fold (40.9 ± 4.6 ng vs. 25.6 ± 3.3 ng, p < 0.05) in iMSC spheroids. Compared with active TGF-β1, the presentation of latent TGF-β1 resulted in greater GAG content (26.6 ± 1.8 ng vs. 41.9 ± 4.3 ng, p < 0.01). Finally, we demonstrated the capacity of individual spheroids to self-assemble into larger constructs and undergo both chondrogenic and hypertrophic differentiation when maintained in lineage-inducing media. These results highlight the potential of idECM to enhance the efficacy of chondrogenic stimuli for improved cartilage regeneration using human MSCs and iMSCs.

Fibroblasts/three-dimensional scaffolds complexes promote wound healing in rats with skin defects

We aim to construct a three-dimensional nano-skin scaffold material in vitro and study its promoting effect on wound healing in vivo. In this study, hybrid constructs of three-dimensional (3D) scaffolds were successfully fabricated by combination of type I collagen (COL-1) and polylactic-glycolic acid (PLGA). Fibroblasts and human umbilical cord mesenchymal stem cells (hUCMSCs) were used to implanted into 3D scaffolds and constructed into SD skin scaffolds in vitro. Finally, the fibroblasts/scaffolds complexes were inoculated on the surface of rat wound skin to study the promoting effect of the complex on wound healing. In our study, we successfully built a 3D scaffold, which had a certain porosity. Meanwhile, the content of COL-1 in the cell supernatant of fibroblast/scaffold complexes was increased. Furthermore, the expression of F-actin, CD105, integrin β, VEGF, and COL-1 was up-regulated in hUCMSC/scaffold complexes compared with the control group. In vivo, fibroblast/scaffold complexes promoted wound healing in rats. Our data suggested that the collagen Ⅳ and vimentin were elevated and collagen fibers were neatly arranged in the fibroblast/scaffold complex group was significantly higher than that in the scaffold group. Taken together, fibroblast/scaffold complexes were expected to be novel materials for treating skin defects.

In vitro and in vivo assessment of a non-animal sourced chitosan scaffold loaded with xeno-free umbilical cord mesenchymal stromal cells cultured under macromolecular crowding conditions

There is an increasing demand to not only accelerate the development of advanced therapy tissue engineered medicines, but to also eliminate xenogeneic materials from their development cycle. With these in mind, herein we first assessed the influence of carrageenan as macromolecular crowding agent to enhance and accelerate extracellular matrix deposition in xeno-free human umbilical cord mesenchymal stromal cell cultures and we developed and characterised a non-animal sourced chitosan scaffold. Following appropriate in vitro experimentation, a splinted nude mouse wound healing model was used to assess wound closure and scar size of non-treated control, non-animal sourced chitosan scaffold, non-animal sourced chitosan scaffold loaded with xeno-free human umbilical cord mesenchymal stromal cells and non-animal sourced chitosan scaffold loaded with xeno-free human umbilical cord mesenchymal stromal cells cultured under macromolecular crowding conditions groups. Across all three donors, carrageenan supplementation significantly increased collagen deposition at day 5, day 8 and day 11 without affecting cell morphology, viability, DNA concentration and metabolic activity. Through freeze drying, a non-animal sourced chitosan sponge was developed with appropriate structural and mechanical properties for wound healing applications. In vitro biological analysis made apparent that neither the scaffold nor macromolecular crowding negatively impacted xeno-free human umbilical cord mesenchymal stromal cell metabolic activity and proliferation. In vivo biological analysis revealed no significant differences between the groups in wound closure and scar size, raising question about the suitability of the model. In any case, this work sets the foundations for the development of completely xeno-free tissue engineered medicines.

Combining ultrasound technology with targeted fucoidan/arginine-gelatin nanoparticles loaded with doxorubicin to enhance therapeutic efficacy and modulate bioeffects in drug-resistant triple-negative breast cancer

Triple-negative breast cancer (TNBC) presents formidable challenges due to its aggressive nature and high recurrence rates, compounded by the involvement of epithelial-mesenchymal transition (EMT) in its progression and metastasis. Standard chemotherapy, which typically employs doxorubicin (DOX), remains a primary treatment approach. However, multidrug resistance (MDR) mechanisms, which include ATP-binding cassette transporters and EMT, contribute to treatment failures. Ultrasound has emerged as a promising modality among the various strategies explored to address MDR in TNBC. It serves as a diagnostic tool and holds therapeutic potential by inducing various biological effects depending on the exposure level. Targeted nanoparticles offer a means to enhance drug delivery efficiency. Our study aims to advance ultrasound technology combined with biocompatible nanoparticles using simplified preparation methods to improve treatment outcomes for drug-resistant TNBC. In particular, employing DOX-loaded fucoidan/arginine-gelatin nanoparticles facilitated the targeted delivery of chemotherapy drugs to tumors by effectively interacting with P-selectin, resulting in tumor growth inhibition. Furthermore, these nanoparticles mitigated MDR and EMT, particularly when combined with ultrasound treatment. This integrated approach of nanoparticle delivery with ultrasonography opens up a promising and innovative avenue for clinical cancer research.

Tailored environments for directed mesenchymal stromal cell proliferation and differentiation using decellularized extracellular matrices in conjunction with substrate modulus

Decellularised extracellular matrix (dECM) produced by mesenchymal stromal cells (MSCs) is a promising biomaterial for improving the ex vivo expansion of MSCs. The dECMs are often deposited on high modulus surfaces such as tissue culture plastic or glass, and subsequent differentiation assays often bias towards osteogenesis. We tested the hypothesis that dECM deposited on substrates of varying modulus will produce cell culture environments that are tailored to promote the proliferation and/or lineage-specific differentiation of MSCs. dECM was produced on type I collagen-functionalised polyacrylamide hydrogels with discrete moduli (∼4, 10, and 40 kPa) or in a linear gradient of modulus that spans the same range, and the substrates were used as culture surfaces for MSCs. Fluorescence spectroscopy and mass spectrometry characterization revealed structural compositional changes in the dECM as a function of substrate modulus. Softer substrates (4 kPa) with dECM supported the largest number of MSCs after 7 days (∼1.6-fold increase compared to glass). Additionally, osteogenic differentiation was greatest on high modulus substrates (40 kPa and glass) with dECM. Nuclear translocation of YAP1 was observed on all surfaces with a modulus of 10 kPa or greater and may be a driver for the increased osteogenesis on the high modulus surfaces. These data demonstrate that dECM technology can be integrated with environmental parameters such as substrate modulus to improve/tailor MSC proliferation and differentiation during ex vivo culture. These results have potential impact in the improved expansion of MSCs for tailored therapeutic applications and in the development of advanced tissue engineering scaffolds. STATEMENT OF SIGNIFICANCE: Mesenchymal stromal cells (MSCs) are extensively used in tissue engineering and regenerative medicine due to their ability to proliferate, differentiate, and modulate the immune environment. Controlling MSC behavior is critical for advances in the field. Decellularised extracellular matrix (dECM) can maintain MSC properties in culture, increase their proliferation rate and capacity, and enhance their stimulated differentiation. Substrate stiffness is another key driver of cell function, and previous reports have primarily looked at dECM deposition and function on stiff substrates such as glass. Herein, we produce dECM on substrates of varying stiffness to create tailored environments that enhance desired MSC properties such as proliferation and differentiation. Additionally, we complete mechanistic studies including quantitative mass spec of the ECM to understand the biological function.

Xenogeneic versus allogeneic serum and macromolecular crowding in human tenocyte cultures

Allogeneic serum and tissue-specific extracellular matrix have been shown to maintain permanently differentiated cell phenotype in culture. This is of particular importance for human tenocytes, a cell population that readily loses its function during ex vivo culture. With these in mind, herein we extracted human tenocytes using either foetal bovine serum or human serum, cultured them in the absence and presence of carrageenan and Ficoll®, the most widely used macromolecular crowding agents (to induce tissue-specific extracellular matrix deposition), and assessed cellular function, via metabolic activity, viability, proliferation and immunofluorescence for collagen related molecules, non-collagenous molecules and transmembrane molecules. At day 7, longest time point assessed, neither carrageenan nor Ficoll® significantly affected metabolic activity, viability and proliferation in either serum and human serum significantly increased metabolic activity and proliferation. At day 7, in the absence of macromolecular crowding, cells in human serum deposited significantly lower collagen type VI, biglycan, versican and tenomodulin than cells in foetal bovine serum. Interestingly, at day 7, in comparison to the no macromolecular crowding group, carrageenan in foetal bovine serum induced the highest effect, as judged by the highest number of significantly increased molecules (collagen type I, collagen type IV, collagen type V, collagen type VI, transforming growth factor β1, matrix metalloproteinase 14, lumican, versican, scleraxis and integrin α2β1). These data, although contradict previous observations where human serum outperformed foetal bovine serum, at the same time, support the use of foetal bovine serum in the development of cell-based medicines.

PLA tissue-engineered scaffolds loaded with sustained-release active substance chitosan nanoparticles: Modeling BSA-bFGF as the active substance

The utilization of basic fibroblast growth factor (bFGF) in the development of tissue-engineered scaffolds is both challenging and imperative. In our pursuit of creating a scaffold that aligns with the natural healing process, we initially fabricated chitosan-bFGF nanoparticles (CS-bFGF NPs) through electrostatic spraying. Subsequently, polylactic acid (PLA) fiber was prepared using electrospinning technique, and the CS-bFGF NPs were uniformly embedded within the pores of porous PLA fibers. Scanning electron micrographs illustrate the smooth surface of the nanoparticles, showing a porous structure intricately attached to PLA fibers. Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses provided conclusive evidence that the CS-bFGF NPs were uniformly distributed throughout the porous PLA fibers, forming a robust physical bond through electrostatic adsorption. The resultant scaffolds exhibited commendable mechanical properties and hydrophilicity, facilitating a sustained-release for 72 h. Furthermore, the biocompatibility and degradation performance of the scaffolds were substantiated by monitoring conductivity and pH changes in pure water over different time intervals, complemented by scanning electron microscopy (SEM) observations. Cell experiments confirmed the cytocompatibility of the scaffolds. In animal studies, the group treated with 16 % NPs/Scaffold demonstrated the highest epidermal reconstruction rate. In summary, our developed materials present a promising candidate for serving as a tissue engineering scaffold, showcasing exceptional biocompatibility, sustained-release characteristics, and substantial potential for promoting epidermal regeneration.

Insulin-like growth factor-binding protein 7 (IGFBP7): A microenvironment-dependent regulator of angiogenesis and vascular remodeling

Insulin-like Growth Factor-Binding Protein 7 (IGFBP7) is an extracellular matrix (ECM) glycoprotein, highly enriched in activated vasculature during development, physiological and pathological tissue remodeling. Despite decades of research, its role in tissue (re-)vascularization is highly ambiguous, exhibiting pro- and anti-angiogenic properties in different tissue remodeling states. IGFBP7 has multiple binding partners, including structural ECM components, cytokines, chemokines, as well as several receptors. Based on current evidence, it is suggested that IGFBP7's bioactivity is strongly dependent on the microenvironment it is embedded in. Current studies indicate that during physiological angiogenesis, IGFBP7 promotes endothelial cell attachment, luminogenesis, vessel stabilization and maturation. Its effects on other stages of angiogenesis and vessel function remain to be determined. IGFBP7 also modulates the pro-angiogenic properties of other signaling factors, such as VEGF-A and IGF, and potentially acts as a growth factor reservoir, while its actual effects on the factors' signaling may depend on the environment IGFBP7 is embedded in. Besides (re-)vascularization, IGFBP7 clearly promotes progenitor and stem cell commitment and may exhibit anti-inflammatory and anti-fibrotic properties. Nonetheless, its role in inflammation, immunomodulation, fibrosis and cellular senescence is again likely to be context-dependent. Future studies are required to shed more light on the intricate functioning of IGFBP7.

Mesenchymal Stem Cell Spheroids: A Promising Tool for Vascularized Tissue Regeneration

BACKGROUND

Mesenchymal stem cells (MSCs) are undifferentiated cells that can differentiate into specific cell lineages when exposed to the right conditions. The ability of MSCs to differentiate into particular cells is considered very important in biological research and clinical applications. MSC spheroids are clusters of MSCs cultured in three dimensions, which play an important role in enhancing the proliferation and differentiation of MSCs. MSCs can also participate in vascular formation by differentiating into endothelial cells and secreting paracrine factors. Vascularization ability is essential in impaired tissue repair and function recovery. Therefore, the vascularization ability of MSCs, which enhances angiogenesis and accelerates tissue healing has made MSCs a promising tool for tissue regeneration. However, MSC spheroids are a relatively new research field, and more research is needed to understand their full potential.

METHODS

In this review, we highlight the importance of MSC spheroids' vascularization ability in tissue engineering and regenerative medicine while providing the current status of studies on the MSC spheroids' vascularization and suggesting potential future research directions for MSC spheroids.

RESULTS

Studies both in vivo and in vitro have demonstrated MSC spheroids' capacity to develop into endothelial cells and stimulate vasculogenesis.

CONCLUSION

MSC spheroids show potential to enhance vascularization ability in tissue regeneration. Yet, further research is required to comprehensively understand the relationship between MSC spheroids and vascularization mechanisms.

Redefining vascular repair: revealing cellular responses on PEUU-gelatin electrospun vascular grafts for endothelialization and immune responses on in vitro models

Tissue-engineered vascular grafts (TEVGs) poised for regenerative applications are central to effective vascular repair, with their efficacy being significantly influenced by scaffold architecture and the strategic distribution of bioactive molecules either embedded within the scaffold or elicited from responsive tissues. Despite substantial advancements over recent decades, a thorough understanding of the critical cellular dynamics for clinical success remains to be fully elucidated. Graft failure, often ascribed to thrombogenesis, intimal hyperplasia, or calcification, is predominantly linked to improperly modulated inflammatory reactions. The orchestrated behavior of repopulating cells is crucial for both initial endothelialization and the subsequent differentiation of vascular wall stem cells into functional phenotypes. This necessitates the TEVG to provide an optimal milieu wherein immune cells can promote early angiogenesis and cell recruitment, all while averting persistent inflammation. In this study, we present an innovative TEVG designed to enhance cellular responses by integrating a physicochemical gradient through a multilayered structure utilizing synthetic (poly (ester urethane urea), PEUU) and natural polymers (Gelatin B), thereby modulating inflammatory reactions. The luminal surface is functionalized with a four-arm polyethylene glycol (P4A) to mitigate thrombogenesis, while the incorporation of adhesive peptides (RGD/SV) fosters the adhesion and maturation of functional endothelial cells. The resultant multilayered TEVG, with a diameter of 3.0 cm and a length of 11 cm, exhibits differential porosity along its layers and mechanical properties commensurate with those of native porcine carotid arteries. Analyses indicate high biocompatibility and low thrombogenicity while enabling luminal endothelialization and functional phenotypic behavior, thus limiting inflammation in in-vitro models. The vascular wall demonstrated low immunogenicity with an initial acute inflammatory phase, transitioning towards a pro-regenerative M2 macrophage-predominant phase. These findings underscore the potential of the designed TEVG in inducing favorable immunomodulatory and pro-regenerative environments, thus holding promise for future clinical applications in vascular tissue engineering.

Hierarchical Design of Tissue-Mimetic Fibrillar Hydrogel Scaffolds

Most tissues of the human body present hierarchical fibrillar extracellular matrices (ECMs) that have a strong influence over their physicochemical properties and biological behavior. Of great interest is the introduction of this fibrillar structure to hydrogels, particularly due to the water-rich composition, cytocompatibility, and tunable properties of this class of biomaterials. Here, the main bottom-up fabrication strategies for the design and production of hierarchical biomimetic fibrillar hydrogels and their most representative applications in the fields of tissue engineering and regenerative medicine are reviewed. For example, the controlled assembly/arrangement of peptides, polymeric micelles, cellulose nanoparticles (NPs), and magnetically responsive nanostructures, among others, into fibrillar hydrogels is discussed, as well as their potential use as fibrillar-like hydrogels (e.g., those from cellulose NPs) with key biofunctionalities such as electrical conductivity or remote stimulation. Finally, the major remaining barriers to the clinical translation of fibrillar hydrogels and potential future directions of research in this field are discussed.

Primary Human Cell-Derived Extracellular Matrix from Decellularized Fibroblast Microtissues with Tissue-Dependent Composition and Microstructure

Purpose

Human extracellular matrix (ECM) exhibits complex protein composition and architecture depending on tissue and disease state, which remains challenging to reverse engineer. One promising approach is based on cell-secreted ECM from primary human fibroblasts that can be decellularized into acellular biomaterials. However, fibroblasts cultured on rigid culture plastic or biomaterial scaffolds can experience aberrant mechanical cues that perturb the biochemical, mechanical, and the efficiency of ECM production.

Methods

Here, we demonstrate a method for preparing decellularized ECM using primary human fibroblasts with tissue and disease-specific features with two case studies: (1) cardiac fibroblasts; (2) lung fibroblasts from healthy or diseased donors. Cells aggregate into engineered microtissues in low adhesion microwells that deposited ECM and can be decellularized. We systematically investigate microtissue morphology, matrix architecture, and mechanical properties, along with transcriptomic and proteomic analysis.

Results

Microtissues exhibited tissue-specific gene expression and proteomics profiling, with ECM complexity similar to native tissues. Healthy lung microtissues exhibited web-like fibrillar collagen compared to dense patches in healthy heart microtissues. Diseased lung exhibited more disrupted collagen architecture than healthy. Decellularized microtissues had tissue-specific mechanical stiffness that was physiologically relevant. Importantly, decellularized microtissues supported viability and proliferation of human cells.

Conclusions

We show that engineered microtissues of primary human fibroblasts seeded in low-adhesion microwells can be decellularized to produce human, tissue and disease-specific ECM. This approach should be widely applicable for generating personalized matrix that recapitulate tissues and disease states, relevant for culturing patient cells ex vivo as well as implantation for therapeutic treatments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00809-y.

Cell-Derived Matrix: Production, Decellularization, and Application of Wound Repair

Chronic nonhealing wounds significantly reduce patients' quality of life and are a major burden on healthcare systems. Over the past few decades, tissue engineering materials have emerged as a viable option for wound healing, with cell-derived extracellular matrix (CDM) showing remarkable results. The CDM's compatibility and resemblance to the natural tissue microenvironment confer distinct advantages to tissue-engineered scaffolds in wound repair. This review summarizes the current processes for CDM preparation, various cell decellularization protocols, and common characterization methods. Furthermore, it discusses the applications of CDM in wound healing, including skin defect and wound repair, angiogenesis, and engineered vessels, and offers perspectives on future developments.

Gums as Macromolecular Crowding Agents in Human Skin Fibroblast Cultures

Even though tissue-engineered medicines are under intense academic, clinical, and commercial investigation, only a handful of products have been commercialised, primarily due to the costs associated with their prolonged manufacturing. While macromolecular crowding has been shown to enhance and accelerate extracellular matrix deposition in eukaryotic cell culture, possibly offering a solution in this procrastinating tissue-engineered medicine development, there is still no widely accepted macromolecular crowding agent. With these in mind, we herein assessed the potential of gum Arabic, gum gellan, gum karaya, and gum xanthan as macromolecular crowding agents in WS1 skin fibroblast cultures (no macromolecular crowding and carrageenan were used as a control). Dynamic light scattering analysis revealed that all macromolecules had negative charge and were polydispersed. None of the macromolecules affected basic cellular function. At day 7 (the longest time point assessed), gel electrophoresis analysis revealed that all macromolecules significantly increased collagen type I deposition in comparison to the non-macromolecular crowding group. Also at day 7, immunofluorescence analysis revealed that carrageenan; the 50 µg/mL, 75 µg/mL, and 100 µg/mL gum gellan; and the 500 µg/mL and 1000 µg/mL gum xanthan significantly increased both collagen type I and collagen type III deposition and only carrageenan significantly increased collagen type V deposition, all in comparison to the non-macromolecular crowding group at the respective time point. This preliminary study demonstrates the potential of gums as macromolecular crowding agents, but more detailed biological studies are needed to fully exploit their potential in the development of tissue-engineered medicines.

Schwann cells acquire a repair phenotype after assembling into spheroids and show enhanced in vivo therapeutic potential for promoting peripheral nerve repair

The prognosis for postinjury peripheral nerve regeneration remains suboptimal. Although transplantation of exogenous Schwann cells (SCs) has been considered a promising treatment to promote nerve repair, this strategy has been hampered in practice by the limited availability of SC sources and an insufficient postengraftment cell retention rate. In this study, to address these challenges, SCs were aggregated into spheroids before being delivered to an injured rat sciatic nerve. We found that the three-dimensional aggregation of SCs induced their acquisition of a repair phenotype, as indicated by enhanced levels of c-Jun expression/activation and decreased expression of myelin sheath protein. Furthermore, our in vitro results demonstrated the superior potential of the SC spheroid-derived secretome in promoting neurite outgrowth of dorsal root ganglion neurons, enhancing the proliferation and migration of endogenous SCs, and recruiting macrophages. Moreover, transplantation of SC spheroids into rats after sciatic nerve transection effectively increased the postinjury nerve structure restoration and motor functional recovery rates, demonstrating the therapeutic potential of SC spheroids. In summary, transplantation of preassembled SC spheroids may hold great potential for enhancing the cell delivery efficiency and the resultant therapeutic outcome, thereby improving SC-based transplantation approaches for promoting peripheral nerve regeneration.

The role of decellularized cell derived extracellular matrix in the establishment and culture ofin vitrobreast cancer tumor model

Decades of research have shown that two-dimensional cell culture studies are insufficient for preclinical cancer diagnosis and treatment, and that cancer cells in three-dimensional (3D) culture systems have better cell-cell and cell-matrix interactions, gene expression, heterogeneity, and structural complexity that more closely resemblein vivotumors. Researchers are still optimizing 3D culturing settings for different cancers. Despite promising tumor spheroid research, tumor cell-only aggregates lack the tumor microenvironment and cannot model tumors. Here, MCF-7 breast cancer cell derived decellularized extracellular matrix (CD-dECMs) were obtained and converted into autologous, biologically active, biocompatible, and non-immunogenic hydrogels to be used as micro-environment in both organoid formation and culture. For the production of organoids, CD-dECM doping concentrations ranging from 0.1 mg ml-1to 1.5 mg ml-1were evaluated, and the lowest concentration was found to be the most effective. For organoid culture, 8 mg ml-1CD-dECM, 4 mg ml-1rat tendon collagen type I (Col I) (4 mg ml-1) and a 1:1 (v/v) mixture of these two were used and the most viable and the biggest organoids were discovered in CD-dECM/Col I (1:1) group. The results show that autologous CD-dECM can replace hydrogels in tumor organoid generation and culture at low and high concentrations, respectively.

The Transplantation of 3-Dimensional Spheroids of Adipose-Derived Stem Cells Promotes Achilles Tendon Healing in Rabbits by Enhancing the Proliferation of Tenocytes and Suppressing M1 Macrophages

BACKGROUND

Tendons have limited regenerative potential, so healing of ruptured tendon tissue requires a prolonged period, and the prognosis is suboptimal. Although stem cell transplantation-based approaches show promise for accelerating tendon repair, the resultant therapeutic efficacy remains unsatisfactory.

HYPOTHESIS

The transplantation of stem cells preassembled as 3-dimensional spheroids achieves a superior therapeutic outcome compared with the transplantation of single-cell suspensions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Adipose-derived stem cells (ADSCs) were assembled as spheroids using a methylcellulose hydrogel system. The secretome of ADSC suspensions or spheroids was collected and utilized to treat tenocytes and macrophages to evaluate their therapeutic potential and investigate the mechanisms underlying their effects. RNA sequencing was performed to investigate the global difference in gene expression between ADSC suspensions and spheroids in an in vitro inflammatory microenvironment. For the in vivo experiment, rabbits that underwent Achilles tendon transection, followed by stump suturing, were randomly assigned to 1 of 3 groups: intratendinous injection of saline, rabbit ADSCs as conventional single-cell suspensions, or preassembled ADSC spheroids. The tendons were harvested for biomechanical testing and histological analysis at 4 weeks postoperatively.

RESULTS

Our in vitro results demonstrated that the secretome of ADSCs assembled as spheroids exhibited enhanced modulatory activity in (1) tenocyte proliferation (P = .015) and migration (P = .001) by activating extracellular signal-regulated kinase (ERK) signaling and (2) the suppression of the secretion of interleukin-6 (P = .005) and interleukin-1α (P = .042) by M1 macrophages via the COX-2/PGE2/EP4 signaling axis. Gene expression profiling of cells exposed to an inflammatory milieu revealed significantly enriched terms that were associated with the immune response, cytokines, and tissue remodeling in preassembled ADSC spheroids. Ex vivo fluorescence imaging revealed that the engraftment efficiency of ADSCs in the form of spheroids was higher than that of ADSCs in single-cell suspensions (P = .003). Furthermore, the transplantation of ADSC spheroids showed superior therapeutic effects in promoting the healing of sutured stumps, as evidenced by improvements in the tensile strength (P = .019) and fiber alignment (P < .001) of the repaired tendons.

CONCLUSION

The assembly of ADSCs as spheroids significantly advanced their potential to harness tenocytes and macrophages. As a proof of concept, this study clearly demonstrates the effectiveness of using ADSC spheroids to promote tendon regeneration.

CLINICAL RELEVANCE

The present study lays a foundation for future clinical applications of stem cell spheroid-based therapy for the management of tendon injuries.

Tailoring the multiscale mechanics of tunable decellularized extracellular matrix (dECM) for wound healing through immunomodulation

With the discovery of the pivotal role of macrophages in tissue regeneration through shaping the tissue immune microenvironment, various immunomodulatory strategies have been proposed to modify traditional biomaterials. Decellularized extracellular matrix (dECM) has been extensively used in the clinical treatment of tissue injury due to its favorable biocompatibility and similarity to the native tissue environment. However, most reported decellularization protocols may cause damage to the native structure of dECM, which undermines its inherent advantages and potential clinical applications. Here, we introduce a mechanically tunable dECM prepared by optimizing the freeze-thaw cycles. We demonstrated that the alteration in micromechanical properties of dECM resulting from the cyclic freeze-thaw process contributes to distinct macrophage-mediated host immune responses to the materials, which are recently recognized to play a pivotal role in determining the outcome of tissue regeneration. Our sequencing data further revealed that the immunomodulatory effect of dECM was induced via the mechnotrasduction pathways in macrophages. Next, we tested the dECM in a rat skin injury model and found an enhanced micromechanical property of dECM achieved with three freeze-thaw cycles significantly promoted the M2 polarization of macrophages, leading to superior wound healing. These findings suggest that the immunomodulatory property of dECM can be efficiently manipulated by tailoring its inherent micromechanical properties during the decellularization process. Therefore, our mechanics-immunomodulation-based strategy provides new insights into the development of advanced biomaterials for wound healing.

Primary Human Cell-Derived Extracellular Matrix from Decellularized Fibroblast Microtissues with Tissue-Dependent Composition and Microstructure

Human extracellular matrix (ECM) exhibits complex protein composition and architecture depending on tissue and disease state, which remains challenging to reverse engineer. One promising approach is based on cell-secreted ECM from human fibroblasts, which can then be decellularized into an acellular biomaterial. However, fibroblasts initially seeded on rigid tissue culture plastic or biomaterial scaffolds experience aberrant mechanical cues that influence ECM deposition. Here, we show that engineered microtissues of primary human fibroblasts seeded in low-adhesion microwells can be decellularized to produce human, tissue-specific ECM. We investigate: 1) cardiac fibroblasts, as well as 2) lung fibroblasts from healthy, idiopathic fibrosis and chronic obstructive pulmonary disease donors. We demonstrate optimized culture and decellularization conditions, then characterize gene expression and protein composition. We further characterize ECM microstructure and mechanical properties. We envision that this method could be utilized for biomanufacturing of patient and tissue-specific ECM for organoid drug screening as well as implantable scaffolds.

Impact

In this study, we demonstrate a method for preparing decellularized matrix using primary human fibroblasts with tissue and disease-specific features. We aggregate single cell dispersions into engineered tissues using low adhesion microwells and show culture conditions that promote ECM deposition. We demonstrate this approach for cardiac fibroblasts as well as lung fibroblasts (both normal and diseased). We systematically investigate tissue morphology, matrix architecture, and mechanical properties, along with transcriptomic and proteomic analysis. This approach should be widely applicable for generating personalized ECM with features of patient tissues and disease state, relevant for culturing patient cells ex vivo as well as implantation for therapeutic treatments.

Effects of Homogeneous and Heterogeneous Crowding on Translational Diffusion of Rigid Bovine Serum Albumin and Disordered Alfa-Casein

Intracellular environment includes proteins, sugars, and nucleic acids interacting in restricted media. In the cytoplasm, the excluded volume effect takes up to 40% of the volume available for occupation by macromolecules. In this work, we tested several approaches modeling crowded solutions for protein diffusion. We experimentally showed how the protein diffusion deviates from conventional Brownian motion in artificial conditions modeling the alteration of medium viscosity and rigid spatial obstacles. The studied tracer proteins were globular bovine serum albumin and intrinsically disordered α-casein. Using the pulsed field gradient NMR, we investigated the translational diffusion of protein probes of different structures in homogeneous (glycerol) and heterogeneous (PEG 300/PEG 6000/PEG 40,000) solutions as a function of crowder concentration. Our results showed fundamentally different effects of homogeneous and heterogeneous crowded environments on protein self-diffusion. In addition, the applied "tracer on lattice" model showed that smaller crowding obstacles (PEG 300 and PEG 6000) create a dense net of restrictions noticeably hindering diffusing protein probes, whereas the large-sized PEG 40,000 creates a "less restricted" environment for the diffusive motion of protein molecules.

Open-Spaced Ridged Hydrogel Scaffolds Containing TiO2-Self-Assembled Monolayer of Phosphonates Promote Regeneration and Recovery Following Spinal Cord Injury

The spinal cord has a poor ability to regenerate after an injury, which may be due to cell loss, cyst formation, inflammation, and scarring. A promising approach to treating a spinal cord injury (SCI) is the use of biomaterials. We have developed a novel hydrogel scaffold fabricated from oligo(poly(ethylene glycol) fumarate) (OPF) as a 0.08 mm thick sheet containing polymer ridges and a cell-attractive surface on the other side. When the cells are cultured on OPF via chemical patterning, the cells attach, align, and deposit ECM along the direction of the pattern. Animals implanted with the rolled scaffold sheets had greater hindlimb recovery compared to that of the multichannel scaffold control, which is likely due to the greater number of axons growing across it. The immune cell number (microglia or hemopoietic cells: 50-120 cells/mm² in all conditions), scarring (5-10% in all conditions), and ECM deposits (Laminin or Fibronectin: approximately 10-20% in all conditions) were equal in all conditions. Overall, the results suggest that the scaffold sheets promote axon outgrowth that can be guided across the scaffold, thereby promoting hindlimb recovery. This study provides a hydrogel scaffold construct that can be used in vitro for cell characterization or in vivo for future neuroprosthetics, devices, or cell and ECM delivery.

Prochondrogenic effect of decellularized extracellular matrix secreted from human induced pluripotent stem cell-derived chondrocytes

Cartilage is mainly composed of chondrocytes and the extracellular matrix (ECM), which exchange important biochemical and biomechanical signals necessary for differentiation and homeostasis. Human articular cartilage has a low ability for regeneration because it lacks blood vessels, nerves, and lymphatic vessels. Currently, cell therapeutics, including stem cells, provide a promising strategy for cartilage regeneration and treatment; however, there are various hurdles to overcome, such as immune rejection and teratoma formation. In this study, we assessed the applicability of the stem cell-derived chondrocyte ECM for cartilage regeneration. Human induced pluripotent stem cell (hiPSC)-derived chondrocytes (iChondrocytes) were differentiated, and decellularized ECM (dECM) was successfully isolated from cultured chondrocytes. Isolated dECM enhanced in vitro chondrogenesis of iPSCs when recellularized. Implanted dECM also restored osteochondral defects in a rat osteoarthritis model. A possible association with the glycogen synthase kinase-3 beta (GSK3β) pathway demonstrated the fate-determining importance of dECM in regulating cell differentiation. Collectively, we suggested the prochondrogenic effect of hiPSC-derived cartilage-like dECM and offered a promising approach as a non-cellular therapeutic for articular cartilage reconstruction without cell transplantation. STATEMENT OF SIGNIFICANCE: Human articular cartilage has low ability for regeneration and cell culture-based therapeutics could aid cartilage regeneration. Yet, the applicability of human induced pluripotent stem cell-derived chondrocyte (iChondrocyte) extracellular matrix (ECM) has not been elucidated. Therefore, we first differentiated iChondrocytes and isolated the secreted ECM by decellularization. Recellularization was performed to confirm the pro-chondrogenic effect of the decellularized ECM (dECM). In addition, we confirmed the possibility of cartilage repair by transplanting the dECM into the cartilage defect in osteochondral defect rat knee joint. We believe that our proof-of-concept study will serve as a basis for investigating the potential of dECM obtained from iPSC-derived differentiated cells as a non-cellular resource for tissue regeneration and other future applications.

Stabilization and improved functionality of three-dimensional perfusable microvascular networks in microfluidic devices under macromolecular crowding

BACKGROUND

There is great interest to engineer in vitro models that allow the study of complex biological processes of the microvasculature with high spatiotemporal resolution. Microfluidic systems are currently used to engineer microvasculature in vitro, which consists of perfusable microvascular networks (MVNs). These are formed through spontaneous vasculogenesis and exhibit the closest resemblance to physiological microvasculature. Unfortunately, under standard culture conditions and in the absence of co-culture with auxiliary cells as well as protease inhibitors, pure MVNs suffer from a short-lived stability.

METHODS

Herein, we introduce a strategy for stabilization of MVNs through macromolecular crowding (MMC) based on a previously established mixture of Ficoll macromolecules. The biophysical principle of MMC is based on macromolecules occupying space, thus increasing the effective concentration of other components and thereby accelerating various biological processes, such as extracellular matrix deposition. We thus hypothesized that MMC will promote the accumulation of vascular ECM (basement membrane) components and lead to a stabilization of MVN with improved functionality.

RESULTS

MMC promoted the enrichment of cellular junctions and basement membrane components, while reducing cellular contractility. The resulting advantageous balance of adhesive forces over cellular tension resulted in a significant stabilization of MVNs over time, as well as improved vascular barrier function, closely resembling that of in vivo microvasculature.

CONCLUSION

Application of MMC to MVNs in microfluidic devices provides a reliable, flexible and versatile approach to stabilize engineered microvessels under simulated physiological conditions.

ECM-Inspired Hydrogels with ADSCs Encapsulation for Rheumatoid Arthritis Treatment

Due to their intrinsic anti-inflammatory and immunomodulatory properties, adipose-derived stem cells (ADSCs) are explored as a promising alternative in treating rheumatoid arthritis (RA). To address the poor survival and function loss of directly injected stem cells, efforts in this area are focus on the generation of efficient cell delivery vehicles. Herein, a novel extracellular matrix (ECM)-inspired injectable hydrogel for ADSCs encapsulation and RA treatment is proposed. The hydrogel with dendritic polylysine and polysaccharide components is formed through the reversible Schiff base crosslinking. It possesses self-healing capability, superior mechanical properties, minimal toxicity, and immunomodulatory ability. When encapsulated with ADSCs, the hydrogel could recover chronic inflammation by directly reversing the dominant macrophage phenotype from M1 to M2 and inhibiting the migration of fibroblast-like synoviocytes. Through a collagen-induced arthritis rat model, the tremendous therapeutic outcomes of this ADSCs-laden hydrogel, including inflammation attenuation, cartilage protection, and bone mineral density promotion are demonstrated. These results make the ECM-inspired hydrogel laden with ADSCs an ideal candidate for treating RA and other autoimmune disorders.

Rapid formation of 3D: Decellularized extracellular matrix spheroids for enhancing bone formation

Bone marrow mesenchymal stem cell sheet-derived spheroids (BMSCs spheroids) have been widely studied as native bioactive scaffolds. However, the abundant cells in BMSCs spheroids cause immunogenicity and make them difficult to store. This paper aimed to construct a new bioactive scaffold called 3D-decellularized extracellular matrix spheroids (ECM spheroids) via decellularization of BMSCs spheroids to enhance bone formation. Hematoxylin and eosin staining (HE), nuclear and cytoskeletal fluorescence, immunofluorescence (IF), and scanning electron microscopy (SEM) were utilized to detect the characteristics and components of ECM spheroids. Furthermore, the biological properties of migration, adhesion, and recellularization of cells in ECM spheroids were assessed in vitro, and bone formation was evaluated in rat calvarial defects. The results showed that both the nuclei and cytoskeleton in ECM spheroids were greatly altered and one of the major components of FN was intact. The migration, adhesion, and recellularization potential were improved in vitro. Meanwhile, ECM spheroids promoted osteogenesis in rat skull defects after 3 months (p < .01). In conclusion, ECM spheroids were successfully prepared and proven to promote cell migration, adhesion, and proliferation. Bone formation in vivo was also accelerated. We believe that ECM spheroids can be used as bioactive and biocompatible 3D scaffolds in the future.

Culture of patient-derived multicellular clusters in suspended hydrogel capsules for pre-clinical personalized drug screening

A personalized medication regimen provides precise treatment for an individual and can be guided by pre-clinical drug screening. The economical and high-efficiency simulation of the liver tumor microenvironment (TME) in a drug-screening model has high value yet challenging to accomplish. Herein, we propose a simulation of the liver TME with suspended alginate-gelatin hydrogel capsules encapsulating patient-derived liver tumor multicellular clusters, and the culture of patient-derived tumor organoids(PDTOs) for personalized pre-clinical drug screening. The hydrogel capsule offers a 3D matrix environment with mechanical and biological properties similar to those of the liver in vivo. As a result, 18 of the 28 patient-derived multicellular clusters were successfully cultured as PDTOs. These PDTOs, along with hepatocyte growth factor (HGF) of non-cellular components, preserve stromal cells, including cancer-associated fibroblasts (CAFs) and vascular endothelial cells (VECs). They also maintain stable expression of molecular markers and tumor heterogeneity similar to those of the original liver tumors. Drugs, including cabazitaxel, oxaliplatin, and sorafenib, were tested in PDTOs. The sensitivity of PDTOs to these drugs differs between individuals. The sensitivity of one PDTO to oxaliplatin was validated using magnetic resonance imaging (MRI) and biochemical tests after oxaliplatin clinical treatment of the corresponding patient. Therefore, this approach is promising for economical, accurate, and high-throughput drug screening for personalized treatment.

Sourcing of human peripheral blood-derived myeloid angiogenic cells under xeno-free conditions for the treatment of critical limb ischemia

BACKGROUND

Critical limb ischemia (CLI) is the most severe form of peripheral artery disease and exhibits a high risk of lower extremity amputations. As even the most promising experimental approaches based on mesenchymal stem cells (MSCs) demonstrated only moderate therapeutic effects, we hypothesized that other cell types with intrinsic roles in angiogenesis may exhibit a stronger therapeutic potential. We have previously established a protocol to source human peripheral blood-derived angiogenic cells (BDACs). These cells promoted revascularization and took perivascular location at sites of angiogenesis, thus resembling hematopoietic pericytes, which were only described in vivo so far. We thus hypothesized that BDACs might have a superior ability to promote revascularization and rescue the affected limb in CLI.

METHODS

As standard BDAC sourcing techniques involve the use of animal-derived serum, we sought to establish a xeno- and/or serum-free protocol. Next, BDACs or MSCs were injected intramuscularly following the ligation of the iliac artery in a murine model. Their ability to enhance revascularization, impair necrosis and modulate inflammatory processes in the affected limb was investigated. Lastly, the secretomes of both cell types were compared to find potential indications for the observed differences in angiogenic potential.

RESULTS

From the various commercial media tested, one xeno-free medium enabled the derivation of cells that resembled functional BDACs in comparable numbers. When applied to a murine model of CLI, both cell types enhanced limb reperfusion and reduced necrosis, with BDACs being twice as effective as MSCs. This was also reflected in histological evaluation, where BDAC-treated animals exhibited the least muscle tissue degeneration. The BDAC secretome was enriched in a larger number of proteins with pro-angiogenic and anti-inflammatory properties, suggesting that the combination of those factors may be responsible for the superior therapeutic effect.

CONCLUSIONS

Functional BDACs can be sourced under xeno-free conditions paving the way for their safe clinical application. Since BDACs are derived from an easily accessible and renewable tissue, can be sourced in clinically relevant numbers and time frame and exceeded traditional MSCs in their therapeutic potential, they may represent an advantageous cell type for the treatment of CLI and other ischemic diseases.

Biochemical composition of the glomerular extracellular matrix in patients with diabetic kidney disease

In the glomeruli, mesangial cells produce mesangial matrix while podocytes wrap glomerular capillaries with cellular extensions named foot processes and tether the glomerular basement membrane (GBM). The turnover of the mature GBM and the ability of adult podocytes to repair injured GBM are unclear. The actin cytoskeleton is a major cytoplasmic component of podocyte foot processes and links the cell to the GBM. Predominant components of the normal glomerular extracellular matrix (ECM) include glycosaminoglycans, proteoglycans, laminins, fibronectin-1, and several types of collagen. In patients with diabetes, multiorgan composition of extracellular tissues is anomalous, including the kidney, so that the constitution and arrangement of glomerular ECM is profoundly altered. In patients with diabetic kidney disease (DKD), the global quantity of glomerular ECM is increased. The level of sulfated proteoglycans is reduced while hyaluronic acid is augmented, compared to control subjects. The concentration of mesangial fibronectin-1 varies depending on the stage of DKD. Mesangial type III collagen is abundant in patients with DKD, unlike normal kidneys. The amount of type V and type VI collagens is higher in DKD and increases with the progression of the disease. The GBM contains lower amount of type IV collagen in DKD compared to normal tissue. Further, genetic variants in the α3 chain of type IV collagen may modulate susceptibility to DKD and end-stage kidney disease. Human cellular models of glomerular cells, analyses of human glomerular proteome, and improved microscopy procedures have been developed to investigate the molecular composition and organization of the human glomerular ECM.

Strontium Peroxide-Loaded Composite Scaffolds Capable of Generating Oxygen and Modulating Behaviors of Osteoblasts and Osteoclasts

The reconstruction of bone defects remains challenging. The utilization of bone autografts, although quite promising, is limited by several drawbacks, especially substantial donor site complications. Recently, strontium (Sr), a bioactive trace element with excellent osteoinductive, osteoconductive, and pro-angiogenic properties, has emerged as a potential therapeutic agent for bone repair. Herein, a strontium peroxide (SrO₂)-loaded poly(lactic-co-glycolic acid) (PLGA)-gelatin scaffold system was developed as an implantable bone substitute. Gelatin sponges serve as porous osteoconductive scaffolds, while PLGA not only reinforces the mechanical strength of the gelatin but also controls the rate of water infiltration. The encapsulated SrO₂ can release Sr²⁺ in a sustained manner upon exposure to water, thus effectively stimulating the proliferation of osteoblasts and suppressing the formation of osteoclasts. Moreover, SrO₂ can generate hydrogen peroxide and subsequent oxygen molecules to increase local oxygen tension, an essential niche factor for osteogenesis. Collectively, the developed SrO₂-loaded composite scaffold shows promise as a multifunctional bioactive bone graft for bone tissue engineering.

Microgel assembly: Fabrication, characteristics and application in tissue engineering and regenerative medicine

Microgel assembly, a macroscopic aggregate formed by bottom-up assembly of microgels, is now emerging as prospective biomaterials for applications in tissue engineering and regenerative medicine (TERM). This mini-review first summarizes the fabrication strategies available for microgel assembly, including chemical reaction, physical reaction, cell-cell interaction and external driving force, then highlights its unique characteristics, such as microporosity, injectability and heterogeneity, and finally itemizes its applications in the fields of cell culture, tissue regeneration and biofabrication, especially 3D printing. The problems to be addressed for further applications of microgel assembly are also discussed.

Decellularization Strategies for Regenerating Cardiac and Skeletal Muscle Tissues

Cardiovascular disease is the leading cause of death worldwide and is associated with approximately 17.9 million deaths each year. Musculoskeletal conditions affect more than 1.71 billion people globally and are the leading cause of disability. These two areas represent a massive global health burden that is perpetuated by a lack of functionally restorative treatment options. The fields of regenerative medicine and tissue engineering offer great promise for the development of therapies to repair damaged or diseased tissues. Decellularized tissues and extracellular matrices are cornerstones of regenerative biomaterials and have been used clinically for decades and many have received FDA approval. In this review, we first discuss and compare methods used to produce decellularized tissues and ECMs from cardiac and skeletal muscle. We take a focused look at how different biophysical properties such as spatial topography, extracellular matrix composition, and mechanical characteristics influence cell behavior and function in the context of regenerative medicine. Lastly, we describe emerging research and forecast the future high impact applications of decellularized cardiac and skeletal muscle that will drive novel and effective regenerative therapies.

Brain Cancer Cell-Derived Matrices and Effects on Astrocyte Migration

Cell-derived matrices are useful tools for studying the extracellular matrix (ECM) of different cell types and testing the effects on cell migration or wound repair. These matrices typically are generated using extended culture with ascorbic acid to boost ECM production. Applying this technique to cancer cell cultures could advance the study of cancer ECM and its effects on recruitment and training of the tumor microenvironment, but ascorbic acid is potently cytotoxic to cancer cells. Macromolecular crowding (MMC) agents can also be added to increase matrix deposition based on the excluded volume principle. We report the use of MMC alone as an effective strategy to generate brain cancer cell-derived matrices for downstream analyses and cell migration studies. We cultured the mouse glioblastoma cell line GL261 for 1 week in the presence of three previously reported MMC agents (carrageenan, Ficoll 70/400, and hyaluronic acid). We measured the resulting deposition of collagens and sulfated glycosaminoglycans using quantitative assays, as well as other matrix components by immunostaining. Both carrageenan and Ficoll promoted significantly more accumulation of total collagen content, sulfated glycosaminoglycan content, and fibronectin staining. Only Ficoll, however, also demonstrated a significant increase in collagen I staining. The results were more variable in 3D spheroid culture. We focused on Ficoll MMC matrices, which were isolated using the small molecule Raptinal to induce cancer cell apoptosis and matrix decellularization. The cancer cell-derived matrix promoted significantly faster migration of human astrocytes in a scratch wound assay, which may be explained by focal adhesion morphology and an increase in cellular metabolic activity. Ultimately, these data show MMC culture is a useful technique to generate cancer cell-derived matrices and study the effects on stromal cell migration related to wound repair.

A functional extracellular matrix biomaterial enriched with VEGFA and bFGF as vehicle of human umbilical cord mesenchymal stem cells in skin wound healing

The construction of microvascular network is one of the greatest challenges for tissue engineering and cell therapy. Endothelial cells are essential for the construction of network of blood vessels. However, their application meets challenges in clinic due to the limited resource of autologous endothelium. Mesenchymal stem cells can effectively promote the angiogenesis in ischemic tissues for their abilities of endothelial differentiation and paracrine, and abundant sources. Extracellular matrix (ECM) has been widely used as an ideal biomaterial to mimic cellular microenvironment for tissue engineering due to its merits of neutrality, good biocompatibility, degradability, and controllability. In this study, a functional cell derived ECM biomaterial enriched with VEGFA and bFGF by expressing the collagen-binding domain fused factor genes in host cells was prepared. This material could induce endothelial differentiation of human umbilical cord mesenchymal stem cells (hUCMSCs) and promote angiogenesis, which may improve the healing effect of skin injury. Our research not only provides a functional ECM material to inducing angiogenesis by inducing endothelial differentiation of hUCMSCs, but also shed light on the ubiquitous approaches to endow ECM materials different functions by enriching different factors. This study will benefit tissue engineering and regenerative medicine researches.

Modulation of Inherent Niches in 3D Multicellular MSC Spheroids Reconfigures Metabolism and Enhances Therapeutic Potential

Multicellular spheroids show three-dimensional (3D) organization with extensive cell–cell and cell–extracellular matrix interactions. Owing to their native tissue-mimicking characteristics, mesenchymal stem cell (MSC) spheroids are considered promising as implantable therapeutics for stem cell therapy. Herein, we aim to further enhance their therapeutic potential by tuning the cultivation parameters and thus the inherent niche of 3D MSC spheroids. Significantly increased expression of multiple pro-regenerative paracrine signaling molecules and immunomodulatory factors by MSCs was observed after optimizing the conditions for spheroid culture. Moreover, these alterations in cellular behaviors may be associated with not only the hypoxic niche developed in the spheroid core but also with the metabolic reconfiguration of MSCs. The present study provides efficient methods for manipulating the therapeutic capacity of 3D MSC spheroids, thus laying solid foundations for future development and clinical application of spheroid-based MSC therapy for regenerative medicine.

Development of Cell-Derived Matrices for Three-Dimensional In Vitro Cancer Cell Models

Most morphogenetic and pathological processes are driven by cells responding to the surrounding matrix, such as its composition, architecture, and mechanical properties. Despite increasing evidence for the role of extracellular matrix (ECM) in tissue and disease development, many in vitro substitutes still fail to effectively mimic the native microenvironment. We established a novel method to produce macroscale (>1 cm) mesenchymal cell-derived matrices (CDMs) aimed to mimic the fibrotic tumor microenvironment surrounding epithelial cancer cells. CDMs are produced by human adipose mesenchymal stem cells cultured in sacrificial 3D scaffold templates of fibronectin-coated poly-lactic acid microcarriers (MCs) in the presence of macromolecular crowders. We showed that decellularized CDMs closely mimic the fibrillar protein composition, architecture, and mechanical properties of human fibrotic ECM from cancer masses. CDMs had highly reproducible composition made of collagen types I and III and fibronectin ECM with tunable mechanical properties. Moreover, decellularized and MC-free CDMs were successfully repopulated with cancer cells throughout their 3D structure, and following chemotherapeutic treatment, cancer cells showed greater doxorubicin resistance compared to 3D culture in collagen hydrogels. Collectively, these results support the use of CDMs as a reproducible and tunable tool for developing 3D in vitro cancer models.

Cell-Penetrating Delivery of Nitric Oxide by Biocompatible Dinitrosyl Iron Complex and Its Dermato-Physiological Implications

After the discovery of endogenous dinitrosyl iron complexes (DNICs) as a potential biological equivalent of nitric oxide (NO), bioinorganic engineering of [Fe(NO)₂] unit has emerged to develop biomimetic DNICs [(NO)₂Fe(L)₂] as a chemical biology tool for controlled delivery of NO. For example, water-soluble DNIC [Fe₂(μ-SCH₂CH₂OH)₂(NO)₄] (DNIC-1) was explored for oral delivery of NO to the brain and for the activation of hippocampal neurogenesis. However, the kinetics and mechanism for cellular uptake and intracellular release of NO, as well as the biocompatibility of synthetic DNICs, remain elusive. Prompted by the potential application of NO to dermato-physiological regulations, in this study, cellular uptake and intracellular delivery of DNIC [Fe₂(μ-SCH₂CH₂COOH)₂(NO)₄] (DNIC-2) and its regulatory effect/biocompatibility toward epidermal cells were investigated. Upon the treatment of DNIC-2 to human fibroblast cells, cellular uptake of DNIC-2 followed by transformation into protein-bound DNICs occur to trigger the intracellular release of NO with a half-life of 1.8 ± 0.2 h. As opposed to the burst release of extracellular NO from diethylamine NONOate (DEANO), the cell-penetrating nature of DNIC-2 rationalizes its overwhelming efficacy for intracellular delivery of NO. Moreover, NO-delivery DNIC-2 can regulate cell proliferation, accelerate wound healing, and enhance the deposition of collagen in human fibroblast cells. Based on the in vitro and in vivo biocompatibility evaluation, biocompatible DNIC-2 holds the potential to be a novel active ingredient for skincare products.