Endothelial and Osteoblast Differentiation of Adipose-Derived Mesenchymal Stem Cells Using a Cobalt-Doped CaP/Silk Fibroin Scaffold

Adipose derived stem cells - Sources, differentiation capacity and a new target for reconstructive and regenerative medicine

Adipose-derived stem cells (ADSCs) are mesenchymal stem cells (MSCs) derived from adipose tissue with mesenchymal lineage differentiation potential and remarkable potential in regenerative medicine. ADSCs are easily sourced from adipose tissue, share regenerative characteristics akin to other MSCs. Their convenient adherence to plastic culture flasks, coupled with their capacity for in vitro expansion and multi-lineage differentiation, underscores their promise as a robust tool for tissue repair and enhancement. The accessibility of human adipose tissue and the development of minimally invasive isolation protocols have further propelled the autologous use of ADSCs, fueling excitement in both organ repair and regenerative medicine. Consequently, research in ADSCsis experiencing rapid growth. A detailed overview of the current landscape of ADSCs isolation and differentiation capacity including the latest advancements in ADSCs usage, encompassing ongoing clinical investigations are important considerations to understand their potential to shape the landscape of regenerative medicine.

In vivo imaging of adipose-derived stem cell sheets on biodegradable nonwoven fabric using X-ray CT

BACKGROUND

A biodegradable nonwoven fabric that can be used to extract adipose-derived stem cells (ADSCs) from adipose tissue slices was developed, which were cultured rapidly without enzymatic treatment. The extracted and cultured ADSCs remain on the nonwoven fabric and form a thick cell sheet. The aim was to use the thick cell sheet as a treatment by transplanting it into the living body. In addition, the expectation was that it will be possible to observe the cell sheet in the living body using X-ray computed tomography (CT) because the nonwoven fabric used to produce the cell sheet contains 50% (by weight) hydroxyapatite.

RESULTS

Thick cell sheets of ADSCs supported by two layers of nonwoven fabric were cut to size and transplanted into the cheeks of rats. No health damage was observed in the rats in which the cell sheets were implanted, except for one in which the surgery appeared to have failed. X-ray CT imaging showed that the fabric of the implanted cell sheet biodegraded over 12 weeks. Changes in the position, shape, and size of the cell sheet within the rat's body were tracked by X-ray CT. The thick cell sheets, which can be easily produced by simply seeding tissue slices, can be cut into appropriate shapes and transplanted safely, and it was confirmed that they slowly biodegraded when transplanted into the rats' bodies.

CONCLUSIONS

We demonstrated not only that the thick ADSC sheets can be transplanted successfully into animals, but also that the transplanted sheets can be observed in vivo by X-ray CT, which also allows changes in the ADSC sheets to be tracked. The results suggest that the biodegradable nonwoven fabric will be a useful transplantation device to ensure cell engraftment throughout the affected area, and facilitate monitoring of the transplant's subsequent status. We expect that this transplantation device will promote the development of regenerative therapy.

Differentiation of mesenchymal stem cells into vascular endothelial cells in 3D culture: a mini review

Mesenchymal Stem Cells, mesodermal origin and multipotent stem cells, have ability to differentiate into vascular endothelial cells. The cells are squamous in morphology, inlining, and protecting blood vessel tissue, as well as maintaining homeostatic conditions. ECs are essential in vascularization and blood vessels formation. The differentiation process, generally carried out in 2D culture systems, were relied on growth factors induction. Therefore, an artificial extracellular matrix with relevant mechanical properties is essential to build 3D culture models. Various 3D fabrication techniques, such as hydrogel-based and fibrous scaffolds, scaffold-free, and co-culture to endothelial cells were reviewed and summarized to gain insights. The obtained MSCs-derived ECs are shown by the expression of endothelial gene markers and tubule-like structure. In order to mimicking relevant vascular tissue, 3D-bioprinting facilitates to form more complex microstructures. In addition, a microfluidic chip with adequate flow rate allows medium perfusion, providing mechanical cues like shear stress to the artificial vascular vessels.

Conductive hydrogels based on tragacanth and silk fibroin containing dopamine functionalized carboxyl-capped aniline pentamer: Merging hemostasis, antibacterial, and anti-oxidant properties into a multifunctional hydrogel for burn wound healing

Hydrogels possessing both conductive characteristics and notable antibacterial and antioxidant properties hold considerable significance within the realm of wound healing and recovery. The object of current study is the development of conductive hydrogels with antibacterial and antioxidant properties, emphasizing their potential for effective wound healing, especially in treating third-degree burns. For this purpose, various conductive hydrogels are developed based on tragacanth and silk fibroin, with variable dopamine functionalized carboxyl-capped aniline pentamer (CAP@DA). The FTIR analysis confirms that the CAP powder was successfully synthesized and modified with DA. The results show that the incorporation of CAP@DA into hydrogels can increase the porosity and swellability of the hydrogels. Additionally, the mechanical and viscoelastic properties of the hydrogels are also improved. The release of vancomycin from the hydrogels is sustained over time, and the hydrogels are effective in inhibiting the growth of Methicillin-resistant Staphylococcus aureus (MRSA). In vitro cell studies of the hydrogels show that all hydrogels are biocompatible and support cell attachment. The hydrogels' tissue adhesiveness yielded a satisfactory hemostatic outcome in a rat-liver injury model. The third-degree burn was created on the dorsal back paravertebral region of the rats and then grafted with hydrogels. The burn was monitored for 3, 7, and 14 days to evaluate the efficacy of the hydrogel in promoting wound healing. The hydrogels revealed treatment effect, resulting in enhancements in wound closure, dermal collagen matrix production, new blood formation, and anti-inflammatory properties. Better results were obtained for hydrogel with increasing CAP@DA. In summary, the multifunctional conducive hydrogel, featuring potent antibacterial properties, markedly facilitated the wound regeneration process.

Angiogenic and immunomodulation role of ions for initial stages of bone tissue regeneration

It is widely known that bone has intrinsic capacity to self-regenerate after injury. However, the physiological regeneration process can be impaired when there is an extensive damage. One of the main reasons is due to the inability to establish a new vascular network that ensures oxygen and nutrient diffusion, leading to a necrotic core and non-junction of bone. Initially, bone tissue engineering (BTE) emerged to use inert biomaterials to just fill bone defects, but it eventually evolved to mimic bone extracellular matrix and even stimulate bone physiological regeneration process. In this regard, the stimulation of osteogenesis has gained a lot of attention especially in the proper stimulation of angiogenesis, being critical to achieve a successful osteogenesis for bone regeneration. Besides, the immunomodulation of a pro-inflammatory environment towards an anti-inflammatory one upon scaffold implantation has been considered another key process for a proper tissue restoration. To stimulate these phases, growth factors and cytokines have been extensively used. Nonetheless, they present some drawbacks such as low stability and safety concerns. Alternatively, the use of inorganic ions has attracted higher attention due to their higher stability and therapeutic effects with low side effects. This review will first focus in giving fundamental aspects of initial bone regeneration phases, focusing mainly on inflammatory and angiogenic ones. Then, it will describe the role of different inorganic ions in modulating the immune response upon biomaterial implantation towards a restorative environment and their ability to stimulate angiogenic response for a proper scaffold vascularization and successful bone tissue restoration. STATEMENT OF SIGNIFICANCE: The impairment of bone tissue regeneration when there is excessive damage has led to different tissue engineered strategies to promote bone healing. Significant importance has been given in the immunomodulation towards an anti-inflammatory environment together with proper angiogenesis stimulation in order to achieve successful bone regeneration rather than stimulating only the osteogenic differentiation. Ions have been considered potential candidates to stimulate these events due to their high stability and therapeutic effects with low side effects compared to growth factors. However, up to now, no review has been published assembling all this information together, describing individual effects of ions on immunomodulation and angiogenic stimulation, as well as their multifunctionality or synergistic effects when combined together.

Distinctions in bone matrix nanostructure, composition, and formation between osteoblast-like cells, MG-63, and human mesenchymal stem cells, UE7T-13

Osteoblast-like cells and human mesenchymal stem cells (hMSCs) are frequently employed as osteoprogenitor cell models for evaluating novel biomaterials in bone healing and tissue engineering. In this study, the characterization of UE7T-13 hMSCs and MG-63 human osteoblast-like cells was examined. Both cells can undergo osteogenesis and produce calcium extracellular matrix; however, calcium nodules produced by MG-63 lacked a central mass and appeared flatter than UE7T-13. The absence of growing calcium nodules in MG-63 was discovered by SEM-EDX to be associated with the formation of alternating layers of cells and calcium extracellular matrix. The nanostructure and composition analysis showed that UE7T-13 had a finer nanostructure of calcium nodules with a higher calcium/phosphate ratio than MG-63. Both cells expressed high intrinsic levels of collagen type I alpha 1 chain, while only UE7T-13 expressed high levels of alkaline phosphatase, biomineralization associated (ALPL). High ALP activity in UE7T-13 was not further enhanced by osteogenic induction, but in MG-63, low intrinsic ALP activity was greatly induced by osteogenic induction. These findings highlight the differences between the two immortal osteoprogenitor cell lines, along with some technical notes that should be considered while selecting and interpreting the pertinent in vitro model.

Insight into the effect of biomaterials on osteogenic differentiation of mesenchymal stem cells: A review from a mitochondrial perspective

Bone damage may be triggered by a variety of factors, and the damaged area often requires a bone graft. Bone tissue engineering can serve as an alternative strategy for repairing large bone defects. Mesenchymal stem cells (MSCs), the progenitor cells of connective tissue, have become an important tool for tissue engineering due to their ability to differentiate into a variety of cell types. The precise regulation of the growth and differentiation of the stem cells used for bone regeneration significantly affects the efficiency of this type of tissue engineering. During the process of osteogenic induction, the dynamics and function of localized mitochondria are altered. These changes may also alter the microenvironment of the therapeutic stem cells and result in mitochondria transfer. Mitochondrial regulation not only affects the induction/rate of differentiation, but also influences its direction, determining the final identity of the differentiated cell. To date, bone tissue engineering research has mainly focused on the influence of biomaterials on phenotype and nuclear genotype, with few studies investigating the role of mitochondria. In this review, we provide a comprehensive summary of researches into the role of mitochondria in MSCs differentiation and critical analysis regarding smart biomaterials that are able to "programme" mitochondria modulation was proposed. STATEMENT OF SIGNIFICANCE: : • This review proposed the precise regulation of the growth and differentiation of the stem cells used to seed bone regeneration. • This review addressed the dynamics and function of localized mitochondria during the process of osteogenic induction and the effect of mitochondria on the microenvironment of stem cells. • This review summarized biomaterials which affect the induction/rate of differentiation, but also influences its direction, determining the final identity of the differentiated cell through the regulation of mitochondria.

Application of bioactive metal ions in the treatment of bone defects

The treatment of bone defects is an important problem in clinical practice. The rapid development of bone tissue engineering (BTE) may provide a new method for bone defect treatment. Metal ions have been widely studied in BTE and demonstrated a significant effect in promoting bone tissue growth. Different metal ions can be used to treat bone defects according to specific conditions, including promoting osteogenic activity, inhibiting osteoclast activity, promoting vascular growth, and exerting certain antibacterial effects. Multiple studies have confirmed that metal ions-modified composite scaffolds can effectively promote bone defect healing. By studying current extensive research on metal ions in the treatment of bone defects, this paper reviews the mechanism of metal ions in promoting bone tissue growth, analyzes the loading mode of metal ions, and lists some specific applications of metal ions in different types of bone defects. Finally, this paper summarizes the advantages and disadvantages of metal ions and analyzes the future research trend of metal ions in BTE. This article can provide some new strategies and methods for future research and applications of metal ions in the treatment of bone defects.

Osteogenic differentiation of adipose-derived stem cells on dihydroartemisinin electrospun nanofibers

Background

Adipose tissue-derived stem cells (ASCs) are promising candidate in stem cell therapies, and maintaining their stemness potential is vital to achieve effective treatment. Natural-based scaffolds have been recently attracted increasing attention in nanomedicine and drug delivery. In this study, Dihydroartemisinin (DHART)-loaded polycaprolactone collagen nanofibers (PCL/Col NFs) were constructed as effective biocompatible scaffolds through adjusting the proportions of hydrophobic/ hydrophilic polymers for enhanced osteoblastic differentiation of human adipose-derived stem cells (hADSCs).

Results

The designed NFs were characterized through FTIR, XRD, TGA, FE-SEM, and tensile testing. DHART-loaded PCL/Col electrospun NFs provide an ideal solution, with the potential of sustained drug release as well as inhibition of drug re-crystallization. Interestingly, inhibiting DHART re-crystallization can improve its bioavailability and provide a more effective therapeutic efficacy. Besides, the data set found through FE-SEM, MTT, PicoGreen, qPCR, and alkaline phosphatase (ALP) assays revealed the improved adhesion and proliferation rate of hADSCs cultured on PCL/Col/DHART (5%) NFs after 14 and 21 days of incubation.

Conclusions

These findings confirmed the potential of the designed NF scaffolds for sustained/controlled release of DHART therapeutic molecules toward bone tissue regeneration and engineering.

Graphical Abstract

Tissue-engineered bones with adipose-derived stem cells - composite polymer for repair of bone defects

Background: Development of alternative bone tissue graft materials based on tissue engineering technology has gradually become a research focus. Engineered bone composed of biodegradable, biosafe and bioactive materials is attractive, but also challenging. Materials & methods: An adipose-derived stem cell/poly(L-glutamic acid)/chitosan composite scaffold was further developed for construction of biodegradable and bone-promoting tissue-engineered bone. A series of composite scaffold materials with different physical properties such as structure, pore size, porosity and pore diameter was developed. Results: The composite scaffold showed good biodegradability and water absorption, and exhibited an excellent ability to promote bone differentiation. Conclusion: This type of biodegradable scaffold is expected to be applied to the field of bone repair or bone tissue engineering.

A Composite Deferoxamine/Black Phosphorus Nanosheet/Gelatin Hydrogel Scaffold for Ischemic Tibial Bone Repair

Introduction

Bone delay union is mostly caused by lack of blood supply. Although autografts, allografts and artificial bone have been widely used to treat bone delay union, the bone regeneration fails in the ischemic site accompanied by the bone donor site complications and disease transmission. Recently, there is a growing recognition of the importance of hydrogel scaffolds which are regarded as an eligible engineer tissue for bone repair. However, hydrogel is still limited in improving neovascularization.

Methods

In this work, black phosphorus nanosheet and deferoxamine (BPN-DFO) were loaded in the gelatin hydrogel to overcome the high risk of bone delay union and systemically investigated the regeneration capability of BPN-DFO hydrogel in vitro and vivo.

Results

The resulting BPN-DFO hydrogel scaffold showed superior swollen, degradation and release rate, as well as satisfied biocompatibility. BPN-DFO hydrogel shown the significant up-expression of mRNA related to bone regeneration and cell proliferation. In vivo, the proposed BPN-DFO hydrogel significantly improved osteogenesis and neovascularization in the ischemic tibial bone site of SD rats with acute femoral artery occlusion. Both macroscopic and histological evaluation of new regenerated bone showed newly formed blood vessel and collagen using BPN-DFO hydrogel. The immunohistochemistry and RT-PCR revealed that the bone regeneration could be improved via BMP/Runx2 pathway.

Conclusion

The BPN-DFO hydrogel possesses potential tissue engineer material for ischemic bone defect treatment. However, furthermore studies are needed to testify the safety and efficacy of BPN-DFO hydrogel.

Effects of kartogenin/PLGA nanoparticles on silk scaffold properties and stem cell fate

Cartilage is an avascular and aneural connective tissue with poor self-healing capability. Recently, tissue engineering opens up new horizons for staving off or treating cartilage lesions. In this work, kartogenin (KGN), a small chondro-inductive molecule, was loaded into poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), which in turn was embedded in a silk fibroin (SF) scaffold, to prepare an appropriate microenvironment for mesenchymal stem cell (MSC) differentiation. In this research, SF was opted to serve as a scaffold based on its approved biocompatibility and non-toxicity, excellent mechanical properties and processability. The data obtained from this study show that entrapment of KGN in NPs provides sustained release, which could promote the differentiation of MSCs into chondrocytes. Likewise, the scaffold containing KGN-loaded NPs induces glycosaminoglycan production by the seeded MSCs. The introduction of NPs into the scaffold, meanwhile, elevated the compressive strength of the structures (more than two times) without any significant effect on their swelling behavior. Taken together, the authors’ findings demonstrate that the prepared scaffold, with an optimal structure, could be a potential candidate for cartilage tissue regeneration.

The Materiobiology of Silk: Exploring the Biophysical Influence of Silk Biomaterials on Directing Cellular Behaviors

Biophysical properties of the extracellular environment dynamically regulate cellular fates. In this review, we highlight silk, an indispensable polymeric biomaterial, owing to its unique mechanical properties, bioactive component sequestration, degradability, well-defined architectures, and biocompatibility that can regulate temporospatial biochemical and biophysical responses. We explore how the materiobiology of silks, both mulberry and non-mulberry based, affect cell behaviors including cell adhesion, cell proliferation, cell migration, and cell differentiation. Keeping in mind the novel biophysical properties of silk in film, fiber, or sponge forms, coupled with facile chemical decoration, and its ability to match functional requirements for specific tissues, we survey the influence of composition, mechanical properties, topography, and 3D geometry in unlocking the body's inherent regenerative potential.

Silk Biomaterials for Bone Tissue Engineering

Silk is a natural fibrous polymer with application potential in regenerative medicine. Increasing interest remains for silk materials in bone tissue engineering due to their characteristics in biocompatibility, biodegradability and mechanical properties. Plenty of the in vitro and in vivo studies confirmed the advantages of silk in accelerating bone regeneration. Silk is processed into scaffolds, hydrogels, and films to facilitate different bone regenerative applications. Bioactive factors such as growth factors and drugs, and stem cells are introduced to silk-based matrices to create friendly and osteogenic microenvironments, directing cell behaviors and bone regeneration. The recent progress in silk-based bone biomaterials is discussed and focused on different fabrication and functionalization methods related to osteogenesis. The challenges and potential targets of silk bone materials are highlighted to evaluate the future development of silk-based bone materials.

Exosomes derived from macrophages upon cobalt ion stimulation promote angiogenesis

Angiogenesis is critical for tissue repair and regeneration, including implant osseointegration. It is well known that macrophages exert immunomodulatory functions in angiogenesis. However, whether macrophage-derived exosomes participate in the process is still unclear. Cobalt (Co) ions are frequently used as implant additives to mimic hypoxic microenvironment, which can induce angiogenesis through stabilizing hypoxia inducible factor-1α (HIF-1α) of macrophages and endothelial cells (ECs). The present work attempts to investigate whether exosomes derived from macrophages upon Co ion stimulation can mediate angiogenesis and the possible mechanism. The results show that the exosomes promote endothelial migration and angiogenesis in vitro and in vivo, particularly when Co ion concentration is 200 μM. Further studies reveal that the exosomes upregulating nitric oxide (NO), vascular endothelial growth factor (VEGF), and integrin β1 expression may be the underlying mechanism of the observations. Our findings provide new insights for Co ion mediated macrophage-EC communication and surface design of biomaterials from the perspective of pro-angiogenesis.

Human adipose-derived stem cell spheroids incorporating platelet-derived growth factor (PDGF) and bio-minerals for vascularized bone tissue engineering

Stem cells with mineralized materials have been used for bone regeneration; however, engineering the complex vascularized structure of the natural bone remains a challenge. Here, we developed platelet-derived growth factor (PDGF) and bio-mineral coated fibers which were then assembled with human adipose-derived stem cells (hADSCs) to form spheroids as building blocks for vascularized bone regeneration. The PDGF incorporated within the spheroid increased the proliferation of hADSCs, which was characterized by Ki-67 staining and DNA contents. Furthermore, the PDGF enhanced not only osteogenic differentiation, but also endothelial differentiation of hADSCs; the cells within the spheroids showed significantly greater gene expression by 2.46 ± 0.14 fold for osteocalcin (OCN) and by 12.85 ± 3.36 fold for von Willebrand factor (vWF) than those without PDGF. Finally, at two months following transplantation of PDGF-incorporated spheroids onto in vivo mouse calvarial defect, the regenerated bone area (42.48 ± 10.84%) was significantly enhanced and the greatest number of capillaries and arterioles with indication of transplanted hADSCs were observed. Moreover, millimeter-scale in vitro tissue prepared by fused assembly of the spheroids exhibited greater mRNA expression-associated to endothelial lineage. Taken together, these findings indicate that stem cell spheroids incorporating PDGF and bio-minerals could be used as a module for successful vascularized bone regeneration.

Tough Anisotropic Silk Nanofiber Hydrogels with Osteoinductive Capacity

Multiple physical cues such as hierarchical microstructures, topography, and stiffness influence cell fate during tissue regeneration. Yet, introducing multiple physical cues to the same biomaterial remains a challenge. Here, a synergistic cross-linking strategy was developed to fabricate protein hydrogels with multiple physical cues based on combinations of two types of silk nanofibers. β-sheet-rich silk nanofibers (BSNFs) were blended with amorphous silk nanofibers (ASNFs) to form composite nanofiber systems. The composites were transformed into tough hydrogels through horseradish peroxidase (HRP) cross-linking in an electric field, where ASNFs were cross-linked with HRP, while BSNFs were aligned by the electrical field. Anisotropic morphologies and higher stiffness of 120 kPa were achieved. These anisotropic hydrogels induced osteogenic differentiation and the aligned aggregation of stem cells in vitro while also exhibiting osteoinductive capacity in vivo. Improved tissue outcomes with the hydrogels suggest promising applications in bone tissue engineering, as the processing strategy described here provides options to form hydrogels with multiple physical cues.

Exosome loaded alginate hydrogel promotes tissue regeneration in full-thickness skin wounds: An in vivo study

Wound healing is known as one of the most complicated biological processes for injured skin caused by surgical, trauma, burns, or diabetic diseases, which causes a nonfunctioning mass of fibrotic tissue. Recent reports have suggested that exosomes (EXOs) secreted by this type of stem cells may contribute to their paracrine effect. In this study, the EXOs were isolated from the supernatant of cultured adipose-derived stem cells (ADSCs) via ultracentrifugation and filtration. The EXO loaded in the alginate-based hydrogel was used as a bioactive scaffold to preserve the EXO in the wound site in the animal model. The physical and biochemical properties of EXO loaded Alg hydrogel were characterized and results proved that fabricated structure was biodegradable and biocompatible. This bioactive wound dressing technique has significantly improved wound closure, collagen synthesis, and vessel formation in the wound area. Results offer a new viewpoint and a cell-free therapeutic strategy, for wound healing through the application of the composite structure of EXO encapsulated in alginate hydrogel.