Biomimetic Concealing of PLGA Microspheres in a 3D Scaffold to Prevent Macrophage Uptake

Large-scale expansion of human umbilical cord-derived mesenchymal stem cells using PLGA@PLL scaffold

Mesenchymal stem cells (MSCs) are highly important in biomedicine and hold great potential in clinical treatment for various diseases. In recent years, the capabilities of MSCs have been under extensive investigation for practical application. Regarding therapy, the efficacy usually depends on the amount of MSCs. Nevertheless, the yield of MSCs is still limited due to the traditional cultural methods. Herein, we proposed a three-dimensional (3D) scaffold prepared using poly lactic-co-glycolic acid (PLGA) nanofiber with polylysine (PLL) grafting, to promote the growth and proliferation of MSCs derived from the human umbilical cord (hUC-MSCs). We found that the inoculated hUC-MSCs adhered efficiently to the PLGA scaffold with good affinity, fast growth rate, and good multipotency. The harvested cells were ideally distributed on the scaffold and we were able to gain a larger yield than the traditional culturing methods under the same condition. Thus, our cell seeding with a 3D scaffold could serve as a promising strategy for cell proliferation in the large-scale production of MSCs. Moreover, the simplicity and low preparation cost allow this 3D scaffold to extend its potential application beyond cell culture.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40643-023-00635-6.

Bioactive engineered scaffolds based on PCL-PEG-PCL and tumor cell-derived exosomes to minimize the foreign body reaction

Long-term presence of M1 macrophages causes serious foreign body reaction (FBR), which is the main reason for the failure of biological scaffold integration. Inducing M2 polarization of macrophages near scaffolds to reduce foreign body response has been widely researched. In this work, inspired by the special capability of tumor exosomes in macrophages M2 polarization, we integrate tumor-derived exosomes into biological scaffolds to minimize the FBR. In brief, breast cancer cell-derived exosomes are loaded into polycaprolactone-b-polyethylene glycol-b-polycaprolactone (PCL-PEG-PCL) fiber scaffold through physical adsorption and entrapment to constructed bioactive engineered scaffold. In cellular experiments, we demonstrate bioactive engineered scaffold based on PCL-PEG-PCL and exosomes can promote the transformation of macrophages from M1 to M2 through the PI3K/Akt signaling pathway. In addition, the exosomes release gradually from scaffolds and act on the macrophages around the scaffolds to reduce FBR in a subcutaneous implant mouse model. Compared with PCL-PEG-PCL scaffolds without exosomes, bioactive engineered scaffolds reduce significantly inflammation and fibrosis of tissues around the scaffolds. Therefore, cancer cell-derived exosomes show the potential for constructing engineered scaffolds in inhibiting the excessive inflammation and facilitating tissue formation.

Recent advances in PLGA-based biomaterials for bone tissue regeneration

Bone regeneration is an interdisciplinary complex lesson, including but not limited to materials science, biomechanics, immunology, and biology. Having witnessed impressive progress in the past decades in the development of bone substitutes; however, it must be said that the most suitable biomaterial for bone regeneration remains an area of intense debate. Since its discovery, poly (lactic-co-glycolic acid) (PLGA) has been widely used in bone tissue engineering due to its good biocompatibility and adjustable biodegradability. This review systematically covers the past and the most recent advances in developing PLGA-based bone regeneration materials. Taking the different application forms of PLGA-based materials as the starting point, we describe each form's specific application and its corresponding advantages and disadvantages with many examples. We focus on the progress of electrospun nanofibrous scaffolds, three-dimensional (3D) printed scaffolds, microspheres/nanoparticles, hydrogels, multiphasic scaffolds, and stents prepared by other traditional and emerging methods. Finally, we briefly discuss the current limitations and future directions of PLGA-based bone repair materials. STATEMENT OF SIGNIFICANCE: As a key synthetic biopolymer in bone tissue engineering application, the progress of PLGA-based bone substitute is impressive. In this review, we summarized the past and the most recent advances in the development of PLGA-based bone regeneration materials. According to the typical application forms and corresponding crafts of PLGA-based substitutes, we described the development of electrospinning nanofibrous scaffolds, 3D printed scaffolds, microspheres/nanoparticles, hydrogels, multiphasic scaffolds and scaffolds fabricated by other manufacturing process. Finally, we briefly discussed the current limitations and proposed the newly strategy for the design and fabrication of PLGA-based bone materials or devices.

Cardiac Stem Cell-Loaded Delivery Systems: A New Challenge for Myocardial Tissue Regeneration

Cardiovascular disease (CVD) remains the leading cause of death in Western countries. Post-myocardial infarction heart failure can be considered a degenerative disease where myocyte loss outweighs any regenerative potential. In this scenario, regenerative biology and tissue engineering can provide effective solutions to repair the infarcted failing heart. The main strategies involve the use of stem and progenitor cells to regenerate/repair lost and dysfunctional tissue, administrated as a suspension or encapsulated in specific delivery systems. Several studies demonstrated that effectiveness of direct injection of cardiac stem cells (CSCs) is limited in humans by the hostile cardiac microenvironment and poor cell engraftment; therefore, the use of injectable hydrogel or pre-formed patches have been strongly advocated to obtain a better integration between delivered stem cells and host myocardial tissue. Several approaches were used to refine these types of constructs, trying to obtain an optimized functional scaffold. Despite the promising features of these stem cells’ delivery systems, few have reached the clinical practice. In this review, we summarize the advantages, and the novelty but also the current limitations of engineered patches and injectable hydrogels for tissue regenerative purposes, offering a perspective of how we believe tissue engineering should evolve to obtain the optimal delivery system applicable to the everyday clinical scenario.

Permeable hollow 3D tissue-like constructs engineered by on-chip hydrodynamic-driven assembly of multicellular hierarchical micromodules

Engineered three-dimensional (3D) microtissues that recapitulate in vivo tissue morphology and microvessel lumens have shown significant potential in drug screening and regenerative medicine. Although microfluidic-based techniques have been developed for bottom-up assembly of 3D tissue models, the spatial organization of heterogeneous micromodules into tissue-specific 3D constructs with embedded microvessels remains challenging. Inspired by a hydrodynamic-based classic game which stacks rings in water through the flow, a facile strategy is proposed for effective assembly of heterogeneous hierarchical micromodules with a central hole, into permeable hollow 3D tissue-like constructs through hydrodynamic interaction in a versatile microfluidic chip. The micromodules are fabricated by in situ multi-step photo-crosslinking of cell-laden hydrogels with different mechanical properties to give the high fidelity. With the hydrodynamic interaction derived from the discontinuous circulating flow, the micromodules are spatially organized layer-by-layer to form a 3D construct with a microvessel-like lumen. As an example, a ten-layered liver lobule-like construct containing inner radial-like poly(ethylene glycol) diacrylate (PEGDA) structure with hepatocytes and outer hexagonal gelatin methacrylate (GelMA) structure with endothelial cells are assembled in 2 min. During 10 days of co-culture, cells maintain high viability and proliferated along with the composite lobule-like morphology. The 3D construct owns a central lumen, which allows perfusion culture to promote albumin secretion. We anticipate that this microassembly strategy can be used to fabricate vascularized 3D tissues with various physiological morphologies as alternatives for biomedical research applications. STATEMENT OF SIGNIFICANCE: Microfluidic-based assembly is an attractive approach for the fabrication of 3D tissue models using cell-laden hydrogel microstructures with single mechanical stability. However, native tissues are complex 3D structures with indispensable vessels and multiple mechanical properties, which is still challenging to recreate. This study proposed a novel strategy to fabricate tissue-like 3D constructs with embedded lumen through hydrodynamic interaction using multicellular micromodules with hierarchical mechanical properties. The resultant hollow 3D constructs allow perfusion co-culture to enhance cell activity. This strategy relies on a simple and facile microfluidic chip to fabricate various 3D tissue-like constructs with hierarchical mechanical properties and permeable lumen, which can potentially be used as in vitro perfusion models for biomedical research.

Targeted protein delivery: carbodiimide crosslinking influences protein release from microparticles incorporated within collagen scaffolds

Tissue engineering response may be tailored via controlled, sustained release of active agents from protein-loaded degradable microparticles incorporated directly within three-dimensional (3D) ice-templated collagen scaffolds. However, the effects of covalent crosslinking during scaffold preparation on the availability and release of protein from the incorporated microparticles have not been explored. Here, we load 3D ice-templated collagen scaffolds with controlled additions of poly-(DL-lactide-co-glycolide) microparticles. We probe the effects of subsequent N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride crosslinking on protein release, using microparticles with different internal protein distributions. Fluorescein isothiocyanate labelled bovine serum albumin is used as a model protein drug. The scaffolds display a homogeneous microparticle distribution, and a reduction in pore size and percolation diameter with increased microparticle addition, although these values did not fall below those reported as necessary for cell invasion. The protein distribution within the microparticles, near the surface or more deeply located within the microparticles, was important in determining the release profile and effect of crosslinking, as the surface was affected by the carbodiimide crosslinking reaction applied to the scaffold. Crosslinking of microparticles with a high proportion of protein at the surface caused both a reduction and delay in protein release. Protein located within the bulk of the microparticles, was protected from the crosslinking reaction and no delay in the overall release profile was seen.

Nanotechnology and Immunotherapy in Ovarian Cancer: Tracing New Landscapes

Ovarian cancer (OC) is the seventh most common cancer in women worldwide. Standard therapeutic treatments involve debulking surgery combined with platinum-based chemotherapies. Of the patients with advanced-stage cancer who initially respond to current treatments, 50%-75% relapse. Immunotherapy-based approaches aimed at boosting antitumor immunity have recently emerged as promising tools to challenge tumor progression. Treatments with inhibitors of immune checkpoint molecules have shown impressive results in other types of tumors. However, only 15% of checkpoint inhibitors evaluated have proven successful in OC due to the immunosuppressive environment of the tumor and the transport barriers. This limits the efficacy of the existing immunotherapies. Nanotechnology-based delivery systems hold the potential to overcome such limitations. Various nanoformulations including polymeric, liposomes, and lipid-polymer hybrid nanoparticles have already been proposed to improve the biodistribution and targeting capabilities of drugs against tumor-associated immune cells, including dendritic cells and macrophages. In this review, we examine the impact of immunotherapeutic approaches that are currently under consideration for the treatment of OC. In this review, we also provide a comprehensive analysis of the existing nanoparticle-based synthetic strategies and their limitations and advantages over standard treatments. Furthermore, we discuss how the strength of the combination of nanotechnology with immunotherapy may help to overcome the current therapeutic limitations associated with their individual application and unravel a new paradigm in the treatment of this malignancy.

Biomimetic hydroxyapatite/collagen composite drives bone niche recapitulation in a rabbit orthotopic model

Synthetic osteoinductive materials that mimic the human osteogenic niche have emerged as ideal candidates to address this area of unmet clinical need. In this study, we evaluated the osteoinductive potential in a rabbit orthotopic model of a magnesium-doped hydroxyapatite/type I collagen ​(MHA/Coll) composite. The composite was fabricated to exhibit a highly fibrous structure of carbonated MHA with 70% (±2.1) porosity and a Ca/P ratio of 1.5 (±0.03) as well as a diverse range of elasticity separated to two distinct stiffness peaks of low (2.35 ​± ​1.16 ​MPa) and higher (9.52 ​± ​2.10 ​MPa) Young's Modulus. Data suggested that these specific compositional and nanomechanical material properties induced the deposition of de novo mineral phase, while modulating the expression of early and late osteogenic marker genes, in a 3D in vitro model using human bone marrow-derived mesenchymal stem cells (hBM-MSCs). When tested in the rabbit orthotopic model, MHA/Col1 scaffold induction of new trabecular bone mass was observed by DynaCT scan, only 2 weeks after implantation. Bone histomorphometry at 6 weeks revealed a significant amount of de novo bone matrix formation. qPCR demonstrated MHA/Coll scaffold full cellularization in vivo and the expression of both osteogenesis-associated genes (Spp1, Sparc, Col1a1, Runx2, Dlx5) as well as hematopoietic (Vcam1, Cd38, Sele, Kdr) and bone marrow stromal cell marker genes (Vim, Itgb1, Alcam). Altogether, these data provide ​evidence of the solid osteoinductive potential of MHA/Coll and its suitability for multiple approaches of bone regeneration.

Electrospun Patch Functionalized with Nanoparticles Allows for Spatiotemporal Release of VEGF and PDGF-BB Promoting In Vivo Neovascularization

The use of nanomaterials as carriers for the delivery of growth factors has been applied to a multitude of applications in tissue engineering. However, issues of toxicity, stability, and systemic effects of these platforms have yet to be fully understood, especially for cardiovascular applications. Here, we proposed a delivery system composed of poly(dl-lactide- co-glycolide) acid (PLGA) and porous silica nanoparticles (pSi) to deliver vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF). The tight spatiotemporal release of these two proteins has been proven to promote neovascularization. In order to minimize tissue toxicity, localize the release, and maintain a stable platform, we conjugated two formulations of PLGA-pSi to electrospun (ES) gelatin to create a combined ES patch releasing both PDGF and VEGF. When compared to freely dispersed particles, the ES patch cultured in vitro with neonatal cardiac cells had significantly less particle internalization (2.0 ± 1.3%) compared to free PLGA-pSi (21.5 ± 6.1) or pSi (28.7 ± 2.5) groups. Internalization was positively correlated to late-stage apoptosis with PLGA-pSi and pSi groups having increased apoptosis compared to the untreated group. When implanted subcutaneously, the ES patch was shown to have greater neovascularization than controls evidenced by increased expression of α-SMA and CD31 after 21 days. Quantitative reverse transcription-polymerase chain reaction results support increased angiogenesis by the upregulation of VEGFA, VEGFR2, vWF, and COL3A1, exhibiting a synergistic effect with the release of VEGF-A164 and PDGF-BB after 21 days in vivo. The results of this study proved that the ES patch reduced cellular toxicity and may be tailored to have a dual release of growth factors promoting localized neovascularization.

Biomimetic Tissue Engineering: Tuning the Immune and Inflammatory Response to Implantable Biomaterials

Regenerative medicine technologies rely heavily on the use of well-designed biomaterials for therapeutic applications. The success of implantable biomaterials hinges upon the ability of the chosen biomaterial to negotiate with the biological barriers in vivo. The most significant of these barriers is the immune system, which is composed of a highly coordinated organization of cells that induce an inflammatory response to the implanted biomaterial. Biomimetic platforms have emerged as novel strategies that aim to use the principle of biomimicry as a means of immunomodulation. This principle has manifested itself in the form of biomimetic scaffolds that imitate the composition and structure of biological cells and tissues. Recent work in this area has demonstrated the promising potential these technologies hold in overcoming the barrier of the immune system and, thereby, improve their overall therapeutic efficacy. In this review, a broad overview of the use of these strategies across several diseases and future avenues of research utilizing these platforms is provided.

On the Correlation between the Microscopic Structure and Properties of Phosphate-Cross-Linked Chitosan Gels

Ionic chitosan gels fabricated using multivalent anions, tripolyphosphate (TPP) or pyrophosphate (PPi), respectively, have been investigated as potential biomaterials to be used in tissue engineering. Starting from the hypothesis that the polymer mesh texture at the microscale affects the final performance of the resulting materials, an innovative image analysis approach is presented in the first part of the article, which is aimed at deriving quantitative information from transmission electron microscopy images. The image analysis of the (more extended) central area of the gel networks revealed differences between both the cross-linking densities and pore size distributions of the two systems, the TPP gels showing a higher connectivity. Chitosan-TPP gels showed a limited degradation in simulated physiological media up to 6 weeks, reasonably ascribed to the texture of the (more extended) central area of the gels, whereas PPi counterparts degraded almost immediately. The release profiles and the calculation of diffusion coefficients for bovine serum albumin and cytochrome c, herein used as model payloads, indicated a different release behavior depending on the polymer network homogeneity/inhomogeneity and molecular weight of loaded molecules. This finding was ascribed to the marked inhomogeneity of the PPi gels (at variance with the TPP ones), which had been demonstrated in our previous work. Finally, thorough in vitro studies demonstrated good biocompatibility of both chitosan gels, and because of this feature, they can be used as suitable scaffolds for cellular colonization and metabolic activity.

Immune tuning scaffold for the local induction of a pro-regenerative environment

In mammals, tissue regeneration is accomplished through a well-regulated, complex cascade of events. The disruption of the cellular and molecular processes involved in tissue healing might lead to scar formation. Most tissue engineering approaches have tried to improve the regenerative outcome following an injury, through the combination of biocompatible materials, stem cells and bioactive factors. However, implanted materials can cause further healing impairments due to the persistent inflammatory stimuli that trigger the onset of chronic inflammation. Here, it is described at the molecular, cellular and tissue level, the body response to a functionalized biomimetic collagen scaffold. The grafting of chondroitin sulfate on the surface of the scaffold is able to induce a pro-regenerative environment at the site of a subcutaneous implant. The early in situ recruitment, and sustained local retention of anti-inflammatory macrophages significantly reduced the pro-inflammatory environment and triggered a different healing cascade, ultimately leading to collagen fibril re-organization, blood vessel formation, and scaffold integration with the surrounding native tissue.

Heparan Sulfate: A Potential Candidate for the Development of Biomimetic Immunomodulatory Membranes

Clinical trials have demonstrated that heparan sulfate (HS) could be used as a therapeutic agent for the treatment of inflammatory diseases. Its anti-inflammatory effect makes it suitable for the development of biomimetic innovative strategies aiming at modulating stem cells behavior toward a pro-regenerative phenotype in case of injury or inflammation. Here, we propose collagen type I meshes fabricated by solvent casting and further crosslinked with HS (HS-Col) to create a biomimetic environment resembling the extracellular matrix of soft tissue. HS-Col meshes were tested for their capability to provide physical support to stem cells’ growth, maintain their phenotypes and immunosuppressive potential following inflammation. HS-Col effect on stem cells was investigated in standard conditions as well as in an inflammatory environment recapitulated in vitro through a mix of pro-inflammatory cytokines (tumor necrosis factor-α and interferon-gamma; 20 ng/ml). A significant increase in the production of molecules associated with immunosuppression was demonstrated in response to the material and when cells were grown in presence of pro-inflammatory stimuli, compared to bare collagen membranes (Col), leading to a greater inhibitory potential when mesenchymal stem cells were exposed to stimulated peripheral blood mononuclear cells. Our data suggest that the presence of HS is able to activate the molecular machinery responsible for the release of anti-inflammatory cytokines, potentially leading to a faster resolution of inflammation.