The effect of incorporation of SDF-1alpha into PLGA scaffolds on stem cell recruitment and the inflammatory response

Surface modification of decellularized kidney scaffold with chemokine and AKI-CKD cytokine juice to increase the recellularization efficiency of bio-engineered kidney

Chronic kidney disease (CKD) is a prevalent global health issue, primarily caused by glomerular dysfunction, diabetes, endovascular disorders, hypertensive nephrosclerosis, and other vascular diseases. Despite the increase in available organ sources, significant challenges remain in securing organ compatibility, prompting extensive research into creating a bio-artificial kidney free from immune rejection. In this study, a bio-engineered kidney was established using a stem cell chemoattractant within a bioreactor system; rBMSCs were used to recellularize the decellularized kidney scaffold coated with SDF-1α/AKI-CKD cytokine juice under mimic-hypoxic conditions as these chemokines and cytokines are crucial for the cell migration. LC-MS/MS proteomic analysis of the scaffold suggested that it contains various important proteins related to angiogenesis, cell migration, differentiation, etc. The in-silico binding simulation and Immunohistochemical (IHC) staining were utilized to detect the coated chemokines and cytokines. Cells were administered through both ureter and arterial routes of the kidney scaffold to differentiate into epithelial and endothelial cells. After 14 days of the recellularization process utilizing a mimic-hypoxia-induced bioreactor, the SDF-1α/AKI-CKD CJ-coated kidney scaffold exhibited high levels of cell attachment, migration, and proliferation in both the cortex and medulla. Additionally, the coating of the cytokines remarkably enhanced the expression of specific renal cell markers within the complex microfilter-like tubular structures. This study underscores a recellularization strategy that addresses the challenges associated with constructing bio-artificial kidneys and contributes to the growing field of bio-artificial organ research.

A bioactive three-layered skin substitute based on ECM components effectively promotes skin wound healing and regeneration

To overcome the limitations of conventional skin tissue engineering (TE), 3D biofabrication approaches are being developed. However, tissue mimicry should be further improved in skin models. Here, we developed and characterized biomimetic hydrogels to obtain a biofabricated three-layered (BT) skin substitute based on the main components found in the epidermal, dermal, and hypodermal skin layers. Hydrogels for dermal and hypodermal skin layers were based on a mix of agarose and type I collagen, supplemented with skin-related extracellular matrix (ECM) components (dermatan sulfate, hyaluronic acid, and elastin) and loaded with human dermal fibroblasts (hDFs) or human mesenchymal stem/stromal cells (hMSCs), respectively. The epidermal hydrogel was formulated using type I collagen supplemented with keratin and sphingolipids, and seeded with human epidermal keratinocytes (hEKs). Physicochemical results revealed adequate viscosity, gelling times, and pH for each hydrogel solution. The BT Skin also showed good swelling and degradation kinetics, and mechanical properties in a similar range of human skin. The hydrogels and BT Skin demonstrated stable cell viability and metabolic activity, as well as intercellular communication through the release of growth factors. Moreover, the BT Skin demonstrated controlled inflammation in vivo, and produced results comparable to autografting in a mouse skin wound model. This bioactive and biomimetic three-layered BT Skin has a composition that attempts to mimic the natural ECM of the skin, formulated with the characteristic cells and biomolecules present in each skin layer, and offers promising properties for its clinical application in the treatment of patients with skin injuries.

Modulation of biomaterial-induced foreign body response by regulating the differentiation and migration of Treg cells through the CXCL12-CXCR4/7 axis

Tissue exposure to implanted biomaterials triggers a foreign body response (FBR), which is a stepwise immunological process involving innate immune cells and tissue repair cells. Although the regulatory T (Treg) cells play a crucial role in inflammation and tissue repair, their function in the process of FBR has not been well investigated. In this study, as titanium (Ti) exhibits better biocompatibility and induces milder FBR than polymethyl methacrylate (PMMA), we analyzed the characteristics of Treg cells during FBR caused by the two types of biomaterials. In a rat femur implantation model, we found that the number of Treg cells around titanium implants was much more than that in the PMMA-implanted group. Meanwhile, the expression of CXCR4 in tissues around Ti implants was significantly higher, and the expression of CXCR7 was lower. When co-cultured with biomaterials and macrophages, the differentiation and migration of Treg cells in the Ti-implanted group were promoted, and this effect could be modulated by CXCR4/7 inhibitors. Moreover, targeting CXCR4/7 influenced the amount of Treg cells in vivo and then reversed the FBR induced by PMMA or Ti implants. In summary, our findings revealed the role of CXCR4/CXCR7 in regulating the migration and differentiation of Treg cells during FBR and suggested that the CXCL12-CXCR4/CXCR7 axis may serve as a potential therapeutic target for immunomodulating foreign body response.

Enhanced osteogenic capacity of octacalcium phosphate involving adsorption of stromal-derived factor-1 in a standardized defect of a rat femur

This study investigated whether octacalcium phosphate (OCP) enhances bone regeneration through its synergistic effect with stromal-derived factor-1 (SDF-1). Recombinant SDF-1 (0.5-5.0 μg) was combined with OCP granules through lyophilization. OCP/SDF-1 granules were implanted into a rat femoral standardized defect for 2 and 4 weeks and subjected to histomorphometry, C-X-C motif chemokine receptor 4 (CXCR4) and osteocalcin immunohistomorphometry, and tartrate-resistant acid phosphatase (TRAP) staining. Calcium-deficient hydroxyapatite (CDHA) was used as a control for in vitro analyses. Mesenchymal stem cell (MSC) migration was estimated using a Transwell system with OCP/SDF-1. SDF-1 release from OCP/SDF-1 into the supernatant was determined without cells. SDF-1 adsorption in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer onto OCP, the chemical structure of OCP immersed in the medium using Fourier transform infrared spectroscopy, and the degree of supersaturation of the medium were determined. Bone regeneration and OCP degradation were enhanced the most by 1.0 μg of OCP/SDF-1 at 2 weeks after implantation by CT analysis and increasing CXCR4-positive, osteocalcin-positive, and TRAP-positive cells accumulation around the OCP. MSC migration increased until 48 h in the following order: SDF-1 only, CDHA/SDF-1, and OCP/SDF-1, with the greatest effect with 1.0 μg of SDF-1 than from OCP. CDHA promoted a greater release than OCP at 48 h. The physicochemical analyses indicated that SDF-1 interacted with OCP through Freundlich-type adsorption and that the adsorption controlled SDF-1 release from OCP during the hydrolysis into CDHA. Therefore, leveraging its molecular affinity for the OCP surface, OCP/SDF-1 facilitates MSC migration and enhances bone formation by ensuring the controlled, sustained release of SDF-1 from OCP.

Advanced Immunomodulatory Biomaterials for Therapeutic Applications

The multifaceted biological defense system modulating complex immune responses against pathogens and foreign materials plays a critical role in tissue homeostasis and disease progression. Recently developed biomaterials that can specifically regulate immune responses, nanoparticles, graphene, and functional hydrogels have contributed to the advancement of tissue engineering as well as disease treatment. The interaction between innate and adaptive immunity, collectively determining immune responses, can be regulated by mechanobiological recognition and adaptation of immune cells to the extracellular microenvironment. Therefore, applying immunomodulation to tissue regeneration and cancer therapy involves manipulating the properties of biomaterials by tailoring their composition in the context of the immune system. This review provides a comprehensive overview of how the physicochemical attributes of biomaterials determine immune responses, focusing on the physical properties that influence innate and adaptive immunity. This review also underscores the critical aspect of biomaterial-based immune engineering for the development of novel therapeutics and emphasizes the importance of understanding the biomaterials-mediated immunological mechanisms and their role in modulating the immune system.

Exploring mesenchymal stem cells homing mechanisms and improvement strategies

Mesenchymal stem cells (MSCs) are multipotent cells with high self-renewal and multilineage differentiation abilities, playing an important role in tissue healing. Recent advancements in stem cell-based technologies have offered new and promising therapeutic options in regenerative medicine. Upon tissue damage, MSCs are immediately mobilized from the bone marrow and move to the injury site via blood circulation. Notably, allogenically transplanted MSCs can also home to the damaged tissue site. Therefore, MSCs hold great therapeutic potential for curing various diseases. However, one major obstacle to this approach is attracting MSCs specifically to the injury site following systemic administration. In this review, we describe the molecular pathways governing the homing mechanism of MSCs and various strategies for improving this process, including targeted stem cell administration, target tissue modification, in vitro priming, cell surface engineering, genetic modifications, and magnetic guidance. These strategies are crucial for directing MSCs precisely to the injury site and, consequently, enhancing their migration and local tissue repair properties. Specifically, our review provides a guide to improving the therapeutic efficacy of clinical applications of MSCs through optimized in vivo administration and homing capacities.

Application value of combined detection of serum IL-6, SDF-1 and CD64 in the diagnosis of early postoperative infection after limb fractures

OBJECTIVE

To explore the application value of combined detection of serum interleukin-6 (IL-6), stromal cell-derived factor-1 (SDF-1) and neutrophils CD64 (CD64) in the diagnosis of early postoperative infection after limb fractures.

METHODS

419 patients with limb fractures un erwent surgical treatment in our hospital were selected as study subjects, and they were divided into infection group (n = 104) and non-infection group (n = 315) according to postoperative pathological results of puncture to detect the levels of serum IL-6, SDF-1 and CD64 in the two groups on the 1st, 3rd, 5th and 7th day after surgery, and to analyze the clinical diagnostic efficacy of single and combined detection of the three indexes in early postoperative infection after limb fractures by ROC curve.

RESULTS

The levels of serum IL-6, SDF-1 and CD64 in infection group were overtly higher than those in non-infection group at different time after surgery (P < 0.05), and the AUC value, specificity and sensitivity of combined detection were higher than those of single diagnosis. In this study, 14 patients in infection group underwent reoperation, 22 patients received conservative treatment in the later period, 6 patients had postoperative muscular dystrophy, and the remaining patients had a good prognosis.

CONCLUSION

Serum IL-6, SDF-1 and CD64 are closely related to the occurrence of early postoperative infection after limb fractures, and their combination is helpful to improve diagnostic accuracy of early postoperative infection and provide effective reference value for the treatment of postoperative infection in orthopedics.

Analysis of current trends in angiogenesis research for wound healing: A bibliometric study from 2013 to 2023

Background

Traumatic injuries, surgery, and chronic diseases lead to soft tissue wounds. Stimulating normal wound healing (WH) is important for tissue repair and restoration of homeostasis. Lack of angiogenesis impedes wound healing and is noted in chronic wounds. The goal of this investigation was to thoroughly assess the present state and patterns of investigations on angiogenesis in WH by the use of bibliometric analysis.

Methods

Studies examining angiogenesis and WH were sourced from the database of the Web of Science Core Collection. Only studies that fulfilled the inclusion criteria were chosen for the purpose of investigation. To analyze the publications included in this research, bibliometric and visual analysis techniques were applied utilizing tools like VOSviewer and CiteSpace.

Results

For the analysis, 11,558 papers were considered. The number of publications increased annually from 2013 to 2023. China, the USA, and South Korea were the top nations in this subject, accounting for 41.1 %, 19.4 %, and 5.8 % of published articles, respectively. The author and institution with the greatest number of publications were found to be Chang J and Shanghai Jiao Tong University. PLOS One had the greatest publication count among journals, whereas Biomaterials had the greatest number of citations and was often mentioned in co-citations. Angiogenesis-related biomedical engineering and tissue engineering were the topics that received the most research attention. Recent studies have focused on vascular endothelial growth factor and carboxymethyl chitosan as emerging areas of interest.

Conclusion

In this investigation, we compiled the features of publications and determined the most impactful nations, organizations, writers, periodicals, popular subjects, and patterns concerning the process of angiogenesis in the context of WH.

A sequential macrophage activation strategy for bone regeneration: A micro/nano strontium-releasing composite scaffold loaded with lipopolysaccharide

Effective tissue repair relies on the orchestration of different macrophage phenotypes, both the M2 phenotype (promotes tissue repair) and M1 phenotype (pro-inflammatory) deserve attention. In this study, we propose a sequential immune activation strategy to mediate bone regeneration, by loading lipopolysaccharide (LPS) onto the surface of a strontium (Sr) ions -contained composite scaffold, which was fabricated by combining Sr-doped micro/nano-hydroxyapatite (HA) and dual degradable matrices of polycaprolactone (PCL) and poly (lactic-co-glycolic acid) (PLGA). Our strategy involves the sequential release of LPS to promote macrophage homing and induce the expression of the pro-inflammatory M1 phenotype, followed by the release of Sr ions to suppress inflammation. In vitro and in vivo experiments demonstrated that, the appropriate pro-inflammatory effects at the initial stage of implantation, along with the anti-inflammatory effects at the later stage, as well as the structural stability of the scaffolds conferred by the composition, can synergistically promote the regeneration and repair of bone defects.

Multifunctional nanocoatings with synergistic controlled release of zinc ions and cytokines for precise modulation of vascular intimal reconstruction

Vascular stent implantation remains the major therapeutic method for cardiovascular diseases currently. We here introduced crucial biological functional biological function factors (SDF-1α, VEGF) and vital metal ions (Zn2+) into the stent surface to explore their synergistic effect in the microenvironment. The combination of the different factors is known to effectively regulate cellular inflammatory response and selectively regulate cell biological behavior. Meanwhile, in the implemented method, VEGF and Zn2+ were loaded into heparin and poly-l-lysine (Hep-PLL) nanoparticles, ensuring a controlled release of functional molecules with a multi-factor synergistic effect and excellent biological functions in vitro and in vivo. Notably, after 150 days of implantation of the modified stent in rabbits, a thin and smooth new intima was obtained. This study offers a new idea for constructing a modified surface microenvironment and promoting tissue repair.

Modulation of gene expression and bone formation by expanded and dense polytetrafluoroethylene membranes during guided bone regeneration: An experimental study

BACKGROUND

Nonresorbable membranes promote bone formation during guided bone regeneration (GBR), yet the relationships between membrane properties and molecular changes in the surrounding tissue are largely unknown.

AIM

To compare the molecular events in the overlying soft tissue, the membrane, and the underlying bone defect during GBR using dual-layered expanded membranes versus dense polytetrafluoroethylene (PTFE) membranes.

MATERIALS AND METHODS

Rat femur defects were treated with either dense PTFE (d-PTFE) or dual-layered expanded PTFE (dual e-PTFE) or left untreated as a sham. Samples were collected after 6 and 28 days for gene expression, histology, and histomorphometry analyses.

RESULTS

The two membranes promoted the overall bone formation compared to sham. Defects treated with dual e-PTFE exhibited a significantly higher proportion of new bone in the top central region after 28 days. Compared to that in the sham, the soft tissue in the dual e-PTFE group showed 2-fold higher expression of genes related to regeneration (FGF-2 and FOXO1) and vascularization (VEGF). Furthermore, compared to cells in the d-PTFE group, cells in the dual e-PTFE showed 2.5-fold higher expression of genes related to osteogenic differentiation (BMP-2), regeneration (FGF-2 and COL1A1), and vascularization (VEGF), in parallel with lower expression of proinflammatory cytokines (IL-6 and TNF-α). Multiple correlations were found between the molecular activities in membrane-adherent cells and those in the soft tissue.

CONCLUSION

Selective surface modification of the two sides of the e-PTFE membrane constitutes a novel means of modulating the tissue response and promoting bone regeneration.

Decellularization-Based Modification Strategy for Bioactive Xenografts Promoting Tendon Repair

Xenografts have emerged as a promising option for severe tendon defects treatment. However, despite undergoing decellularization, concerns still remain regarding the immunogenicity of xenografts. Because certain components within the extracellular matrix also possess immunogenicity. In this study, a novel strategy of post-decellularization modification aimed at preserving the endogenous capacity of cells on collagen synthesis to mask antigenic epitopes in extracellular matrix is proposed. To implement this strategy, a human-derived rosiglitazone-loaded decellularized extracellular matrix (R-dECM) is developed. R-dECM can release rosiglitazone for over 7 days in vitro. By suppressing M1 macrophage polarization, R-dECM protects the migration and collagen synthesis abilities of tendon-derived stem cells (TDSCs), while also stabilizing the phenotype of M2 macrophages in vitro. RNA sequencing reveals R-dECM can mitigate the detrimental crosstalk between TDSCs and inflammatory cells. When applied to a rat patellar tendon defect model, R-dECM effectively inhibits early inflammation, preventing chronic inflammation. Its duration of function far exceeds the release time of rosiglitazone, implying the establishment of immune evasion, confirming the effectiveness of the proposed strategy. And R-dECM demonstrates superior tendon repair outcomes compared to dECM. Thus, this study provides a novel bioactive scaffold with the potential to enhance the long-term clinical outcomes of xenogeneic tendon grafts.

Pomegranate Peel Extract Differently Modulates Gene Expression in Gingiva-Derived Mesenchymal Stromal Cells under Physiological and Inflammatory Conditions

Pomegranate has shown a favorable effect on gingivitis/periodontitis, but the mechanisms involved are poorly understood. The aim of this study was to test the effect of pomegranate peel extract (PoPEx) on gingiva-derived mesenchymal stromal cells (GMSCs) under physiological and inflammatory conditions. GMSC lines from healthy (H) and periodontitis (P) gingiva (n = 3 of each) were established. The lines were treated with two non-toxic concentrations of PoPEX (low-10; high-40 µg/mL), with or without additional lipopolysaccharide (LPS) stimulation. Twenty-four genes in GMSCs involved in different functions were examined using real-time polymerase chain reaction (RT-PCR). PoPEx (mostly at higher concentrations) inhibited the basal expression of IL-6, MCP-1, GRO-α, RANTES, IP-10, HIF-1α, SDF-1, and HGF but increased the expression of IL-8, TLR3, TGF-β, TGF-β/LAP ratio, IDO-1, and IGFB4 genes in H-GMSCs. PoPEx increased IL-6, RANTES, MMP3, and BMP2 but inhibited TLR2 and GRO-α gene expression in P-GMSCs. LPS upregulated genes for proinflammatory cytokines and chemokines, tissue regeneration/repair (MMP3, IGFBP4, HGF), and immunomodulation (IP-10, RANTES, IDO-1, TLR3, COX-2), more strongly in P-GMSCs. PoPEx also potentiated most genes' expression in LPS-stimulated P-GMSCs, including upregulation of osteoblastic genes (RUNX2, BMP2, COL1A1, and OPG), simultaneously inhibiting cell proliferation. In conclusion, the modulatory effects of PoPEx on gene expression in GMSCs are complex and dependent on applied concentrations, GMSC type, and LPS stimulation. Generally, the effect is more pronounced in inflammation-simulating conditions.

Injectable Hydrogels of Amphiphilic Vitamin E Derivatives for Locoregional Chemotherapy

Vitamin E derivatives are particularly effective in chemotherapy drug development because they are nontoxic, biocompatible, and selective. Among them, α-tocopheryl succinate (α-TOS) can act synergistically with some chemotherapeutic agents. However, its hydrophobicity limits its systemic administration, and localized formulations are not available. Herein, we developed an injectable hydrogel based on self-assembled micelles of a triblock amphiphilic derivative of α-TOS (PEG-2VES), in which doxorubicin (DOX) was encapsulated in the core of the micelles for combined chemotherapy. A molecule of α-TOS was grafted onto each end of poly(ethylene glycols) (PEGs) of different lengths. Hydrogels were prepared by dissolving the polymers or the DOX-loaded micelles in water at room temperature. The subcutaneously injected hydrogels kept their shape and sustainably released the payloads over 7 days without any noticeable inflammatory response. In vitro and in vivo results confirmed the synergistic antitumor effects of the hydrogel and loaded drug. Furthermore, DOX-loaded hydrogels showed greater therapeutic efficiency and fewer toxic side effects than DOX alone. Overall, this hydrogel acts as a multifunctional system that can deliver drug, improve the therapeutic effect, and minimize drug toxicity.

Sequential Dual-Biofactor Release from the Scaffold of Mesoporous HA Microspheres and PLGA Matrix for Boosting Endogenous Bone Regeneration

The combined design of scaffold structure and multi-biological factors is a prominent strategy to promote bone regeneration. Herein, a composite scaffold of mesoporous hydroxyapatite (HA) microspheres loaded with the bone morphogenetic protein-2 (BMP-2) and a poly(DL-lactic-co-glycolic acid) (PLGA) matrix is constructed by 3D printing. Furthermore, the chemokine stromal cell-derived factor-1α (SDF-1α) is adsorbed on a scaffold surface to achieve the sequential release of the dual-biofactors. The results indicate that the rapid release of SDF-1α chemokine on the scaffold surface effectively recruits bone marrow-derived mesenchymal stem cells (BMSCs) to the target defect area, whereas the long-term sustained release of BMP-2 from the HA microspheres in the degradable PLGA matrix successfully triggers the osteogenic differentiation in the recruited BMSCs, significantly promoting bone regeneration and reconstruction. In addition, these structures/biofactors specially combining scaffold exhibit significantly better biological performance than that of other combined scaffolds, including the bare HA/PLGA scaffold, the scaffold loaded with SDF-1α or BMP-2 biofactor alone, and the scaffold with surface SDF-1α and BMP-2 dual-biofactors. The utilization of mesoporous HA, the assembly method, and sequential release of the two biofactors in the 3D printed composite scaffold present a new method for future design of high-performance bone repairing scaffolds.

Biomolecule-releasing bioadhesive for glenoid labrum repair through induced host progenitor cell responses

Glenoid labral tears occur with repetitive dislocation events and are common injuries observed in shoulder arthroscopic procedures. Although surgery can restore shoulder anatomy, repair is associated with poor clinical outcomes, which may be attributed to the poor regenerative capability of glenoid labral fibrocartilage. Thus, this study was designed to assess whether in situ tissue regeneration via biomolecule-stimulated recruitment of progenitor cells is a viable approach for the regeneration of labral tears. We developed a click chemistry-based bioadhesive to improve labral repair and reduce local inflammatory responses due to trauma. Additionally, we previously identified the presence of progenitor cells in the human labrum, which can be recruited by platelet-derived growth factor (PDGF). Thus, we hypothesized that PDGF-releasing adhesives could induce the regenerative responses of progenitor cells at the injury site to improve labral healing. In a rat glenoid labral tear model, we evaluated the effect of PDGF-releasing adhesives on promoting progenitor cells to participate in labral tear healing. After 3 and 6 weeks, the labrum was histologically analyzed for inflammatory responses, progenitor cell recruitment, proliferation, and extracellular matrix (ECM) production (collagen and glycosaminoglycan). Our results showed that adhesives alone considerably reduced local inflammatory responses and labral tissue dissolution. PDGF-releasing adhesives significantly increased progenitor cell recruitment, proliferation, and ECM production. These results demonstrate that by accelerating autologous progenitor cell responses, PDGF-releasing adhesives represent a novel clinically relevant strategy to improve the healing of glenoid labral tears.

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.

Immunomodulatory biomaterials on chemokine signaling in wound healing

Normal wound healing occurs through a careful orchestration of cytokine and chemokine signaling in response to injury. Chemokines are a small family of chemotactic cytokines that are secreted by immune cells in response to injury and are primarily responsible for recruiting appropriate immune cell types to injured tissue at the appropriate time. Dysregulation of chemokine signaling is suspected to contribute to delayed wound healing and chronic wounds in diseased states. Various biomaterials are being used in the development of new therapeutics for wound healing and our understanding of their effects on chemokine signaling is limited. It has been shown that modifications to the physiochemical properties of biomaterials can affect the body's immune reaction. Studying these effects on chemokine expression by various tissues and cell type can help us develop novel biomaterial therapies. In this review, we summarize the current research available on both natural and synthetic biomaterials and their effects on chemokine signaling in wound healing. In our investigation, we conclude that our knowledge of chemokines is still limited and that many in fact share both pro-inflammatory and anti-inflammatory properties. The predominance of either a pro-inflammatory or anti-inflammatory profile is mostly likely dependent on timing after injury and exposure to the biomaterial. More research is needed to better understand the interaction and contribution of biomaterials to chemokine activity in wound healing and their immunomodulatory effects.

Biomedical polymer scaffolds mimicking bone marrow niches to advance in vitro expansion of hematopoietic stem cells

Hematopoietic stem cell (HSC) transplantation provides an effective platform for the treatment of hematological disorders. However, the donor shortage of HSCs and immune responses severely restrict the clinical applications of HSCs. Compared to allogeneic transplantation, autogenous transplantation poses less risk to the immune system, but the problem associated with insufficient HSCs remains a substantial challenge. A significant strategy for obtaining sufficient HSCs is to promote the expansion of HSCs. In vivo, a bone marrow microenvironment supports the survival and hematopoiesis of HSCs. Therefore, it is crucial to establish a platform that mimics the features of a bone marrow microenvironment for the in vitro expansion of HSCs. Three-dimensional (3D) scaffolds have emerged as the most powerful tools to mimic cellular microenvironments for the growth and proliferation of stem cells. Biomedical polymers have been widely utilized as cell scaffolds due to their advantageous features including favorable biocompatibility, biodegradability, as well as adjustable physical and chemical properties. This review focuses on recent advances in the study of biomedical polymer scaffolds that mimic bone marrow microenvironments for the in vitro expansion of HSCs. Bone marrow transplantation and microenvironments are first introduced. Then, biomedical polymer scaffolds for the expansion of HSCs and future prospects are summarized and discussed.

Tantalum and magnesium nanoparticles enhance the biomimetic properties and osteo-angiogenic effects of PCL membranes

Segmental bone defects, accompanied by periosteum stripping or injury, usually lead to delayed bone union or nonunion, which have challenged orthopedic surgeons. The periosteum, which provides essential blood supply and initial stem cells for bone tissue, plays an important role in the repair of bone defects. The reconstruction of the destroyed periosteum has attracted the attention of researchers exploring more satisfactory therapies to repair bone defects. However, periosteum-like biomaterials have yet to meet the clinical requirements and resolve this challenging problem. In this study, we manufactured a nanofiber periosteum replacement based on poly-ε-caprolactone (PCL), in which tantalum nanoparticles (TaNPs) and nanoscale magnesium oxide (MgO) were introduced to enhance its osteogenic and angiogenic ability. The results of in vitro experiments indicated that the PCL/Ta/MgO periosteum replacement, with excellent cytocompatibility, promoted the proliferation of both bone marrow mesenchymal stem cells (BMSCs) and endothelial progenitor cells (EPCs). Furthermore, the incorporation of TaNPs and nano-MgO synergistically enhanced the osteogenic differentiation of BMSCs and the angiogenic properties of EPCs. Similarly, the results of in vivo experiments from subcutaneous implantation and critical-sized calvarial defect models showed that the PCL/Ta/MgO periosteum replacement combined the osteogenesis and angiogenesis abilities, promoting vascularized bone formation to repair critical-sized calvarial defects. The results of our study suggest that the strategy of stimulating repairing bone defects can be achieved with the periosteum repaired in situ and that the proposed periosteum replacement can act as a bioactive medium to accelerate bone healing.

Biomechanically and biochemically functional scaffold for recruitment of endogenous stem cells to promote tendon regeneration

Tendon regeneration highly relies on biomechanical and biochemical cues in the repair microenvironment. Herein, we combined the decellularized bovine tendon sheet (DBTS) with extracellular matrix (ECM) from tendon-derived stem cells (TDSCs) to fabricate a biomechanically and biochemically functional scaffold (tECM-DBTS), to provide a functional and stem cell ECM-based microenvironment for tendon regeneration. Our prior study showed that DBTS was biomechanically suitable to tendon repair. In this study, the biological function of tECM-DBTS was examined in vitro, and the efficiency of the scaffold for Achilles tendon repair was evaluated using immunofluorescence staining, histological staining, stem cell tracking, biomechanical and functional analyses. It was found that tECM-DBTS increased the content of bioactive factors and had a better performance for the proliferation, migration and tenogenic differentiation of bone marrow-derived stem cells (BMSCs) than DBTS. Furthermore, our results demonstrated that tECM-DBTS promoted tendon regeneration and improved the biomechanical properties of regenerated Achilles tendons in rats by recruiting endogenous stem cells and participating in the functionalization of these stem cells. As a whole, the results of this study demonstrated that the tECM-DBTS can provide a bionic microenvironment for recruiting endogenous stem cells and facilitating in situ regeneration of tendons.

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

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

Mesenchymal Stromal Cells from Healthy and Inflamed Human Gingiva Respond Differently to Porphyromonas gingivalis

Gingiva-Derived Mesenchymal Stromal Cells (GMSCs) have been shown to play an important role in periodontitis. However, how P. gingivalis, one of the key etiological agents of the disease, affects healthy (H)- and periodontitis (P)-GMSCs is unknown. To address this problem, we established 10 H-GMSC and 12 P-GMSC lines. No significant differences in morphology, differentiation into chondroblasts and adipocytes, expression of characteristic MSCS markers, including pericyte antigens NG2 and PDGFR, were observed between H- and P-GMSC lines. However, proliferation, cell size and osteogenic potential were higher in P-GMSCs, in contrast to their lower ability to suppress mononuclear cell proliferation. P. gingivalis up-regulated the mRNA expression of IL-6, IL-8, MCP-1, GRO-α, RANTES, TLR-2, HIF-1α, OPG, MMP-3, SDF-1, HGF and IP-10 in P-GMSCs, whereas only IL-6, MCP-1 and GRO-α were up-regulated in H-GMSCs. The expression of MCP-1, RANTES, IP-10 and HGF was significantly higher in P-GMSCs compared to H-GMSCs, but IDO1 was lower. No significant changes in the expression of TLR-3, TLR-4, TGF-β, LAP, IGFBP4 and TIMP-1 were observed in both types of GMSCs. In conclusion, our results suggest that P-GMSCs retain their pro-inflammatory properties in culture, exhibit lower immunosuppressive potential than their healthy counterparts, and impaired regeneration-associated gene induction in culture. All these functions are potentiated significantly by P. gingivalis treatment.

Into the Tissues: Extracellular Matrix and Its Artificial Substitutes: Cell Signalling Mechanisms

The existence of orderly structures, such as tissues and organs is made possible by cell adhesion, i.e., the process by which cells attach to neighbouring cells and a supporting substance in the form of the extracellular matrix. The extracellular matrix is a three-dimensional structure composed of collagens, elastin, and various proteoglycans and glycoproteins. It is a storehouse for multiple signalling factors. Cells are informed of their correct connection to the matrix via receptors. Tissue disruption often prevents the natural reconstitution of the matrix. The use of appropriate implants is then required. This review is a compilation of crucial information on the structural and functional features of the extracellular matrix and the complex mechanisms of cell-cell connectivity. The possibilities of regenerating damaged tissues using an artificial matrix substitute are described, detailing the host response to the implant. An important issue is the surface properties of such an implant and the possibilities of their modification.

Cell-Seeded Biomaterial Scaffolds: The Urgent Need for Unanswered Accelerated Angiogenesis

One of the most arduous challenges in tissue engineering is neovascularization, without which there is a lack of nutrients delivered to a target tissue. Angiogenesis should be completed at an optimal density and within an appropriate period of time to prevent cell necrosis. Failure to meet this challenge brings about poor functionality for the tissue in comparison with the native tissue, extensively reducing cell viability. Prior studies devoted to angiogenesis have provided researchers with some biomaterial scaffolds and cell choices for angiogenesis. For example, while most current angiogenesis approaches require a variety of stimulatory factors ranging from biomechanical to biomolecular to cellular, some other promising stimulatory factors have been underdeveloped (such as electrical, topographical, and magnetic). When it comes to choosing biomaterial scaffolds in tissue engineering for angiogenesis, key traits rush to mind including biocompatibility, appropriate physical and mechanical properties (adhesion strength, shear stress, and malleability), as well as identifying the appropriate biomaterial in terms of stability and degradation profile, all of which may leave essential trace materials behind adversely influencing angiogenesis. Nevertheless, the selection of the best biomaterial and cells still remains an area of hot dispute as such previous studies have not sufficiently classified, integrated, or compared approaches. To address the aforementioned need, this review article summarizes a variety of natural and synthetic scaffolds including hydrogels that support angiogenesis. Furthermore, we review a variety of cell sources utilized for cell seeding and influential factors used for angiogenesis with a concentrated focus on biomechanical factors, with unique stimulatory factors. Lastly, we provide a bottom-to-up overview of angiogenic biomaterials and cell selection, highlighting parameters that need to be addressed in future studies.

Modulation of the Immune System Promotes Tissue Regeneration

The immune system plays an essential role in the angiogenesis, repair, and regeneration of damaged tissues. Therefore, the design of scaffolds that manipulate immune cells and factors in such a way that could accelerate the repair of damaged tissues, following implantation, is one of the main goals of regenerative medicine. However, before manipulating the immune system, the function of the various components of the immune system during the repair process should be well understood and the fabrication conditions of the manipulated scaffolds should be brought closer to the physiological state of the body. In this article, we first review the studies aimed at the role of distinct immune cell populations in angiogenesis and support of damaged tissue repair. In the second part, we discuss the use of strategies that promote tissue regeneration by modulating the immune system. Given that various studies have shown an increase in tissue repair rate with the addition of stem cells and growth factors to the scaffolds, and regarding the limited resources of stem cells, we suggest the design of scaffolds that are capable to develop repair of damaged tissue by manipulating the immune system and create an alternative for repair strategies that use stem cells or growth factors.

Engineering strategies to achieve efficient in vitro expansion of haematopoietic stem cells: development and improvement

Haematopoietic stem cells are the basis for building and maintaining lifelong haematopoietic mechanisms and important resources for the treatment of blood disorders. Haematopoietic niches are microenvironment in the body where...

Mechanistically Scoping Cell-Free and Cell-Dependent Artificial Scaffolds in Rebuilding Skeletal and Dental Hard Tissues

Rebuilding mineralized tissues in skeletal and dental systems remains costly and challenging. Despite numerous demands and heavy clinical burden over the world, sources of autografts, allografts, and xenografts are far limited, along with massive risks including viral infections, ethic crisis, and so on. Per such dilemma, artificial scaffolds have emerged to provide efficient alternatives. To date, cell-free biomimetic mineralization (BM) and cell-dependent scaffolds have both demonstrated promising capabilities of regenerating mineralized tissues. However, BM and cell-dependent scaffolds have distinctive mechanisms for mineral genesis, which makes them methodically, synthetically, and functionally disparate. Herein, these two strategies in regenerative dentistry and orthopedics are systematically summarized at the level of mechanisms. For BM, methodological and theoretical advances are focused upon; and meanwhile, for cell-dependent scaffolds, it is demonstrated how scaffolds orchestrate osteogenic cell fate. The summary of the experimental advances and clinical progress will endow researchers with mechanistic understandings of artificial scaffolds in rebuilding hard tissues, by which better clinical choices and research directions may be approached.

Control of innate immune response by biomaterial surface topography, energy, and stiffness

As the focus of implantable biomaterials has shifted from bioinert implants to bioactive designs, recent research has highlighted the complex interactions between cell physiologic systems and material properties, particularly physical cues. From the cells known to interact with implanted biomaterials, the response of the immune system has been a critical target of study recently. Here, we review studies characterizing the response of innate immune cells to various material cues, particularly of those at the surface of implanted materials.The innate immune system consists of cell types with various roles in inflammation. Neutrophils and macrophages serve both phagocytic and signaling roles, especially early in the inflammatory phase of biomaterial implantation. These cell types ultimately dictate the outcome of implants as chronic inflammation, fibrosis, or integration. Other cell types like dendritic cells, mast cells, natural killer cells, and innate lymphoid cells may also serve an immunomodulatory role in the biomaterial context. This review highlights recent advances in our understanding of the role of innate immunity in the response to implantable biomaterials as well as key mechanobiological findings in innate immune cells underpinning these advances. STATEMENT OF SIGNIFICANCE: This review highlights recent advances in the understanding of the role of innate immunity in the response to implantable biomaterials, especially in neutrophils and macrophages, as well as key mechanobiological findings in innate immune cells underpinning these advances. Here we discuss how physicochemical properties of biomaterials control innate immune cell behavior.

Stromal cell-derived factor (SDF)-1α and platelet-rich plasma enhance bone regeneration and angiogenesis simultaneously in situ in rabbit calvaria

The current study aimed to evaluate the effects of chemokine stromal cell-derived factor (SDF)-1α and platelet-rich plasma (PRP) on bone formation and angiogenesis, and to assess whether SDF-1α and PRP could function synergistically. Four evenly distributed defects (8 mm in diameter) were generated in the calvarial bones of New Zealand white rabbits. All rabbits received four treatment regimens containing autogenous bone particles (AB), SDF-1α, or PRP. AB group presented significantly less bone formation compared with the other three groups 2 and 4 weeks after surgery. The amount of newly formed bone in the AB+PRP+SDF-1α group was similar to that in the AB + SDF-1α group at the 4-week time-point (p = 0.65), and was much greater than that in the AB and AB+PRP group (p < 0.001). Meanwhile, more new blood vessels were formed in the AB+PRP, AB+SDF-1α, and AB+PRP+SDF-1α group versus the AB group. AB+PRP+SDF-1α group showed statistically increased angiogenesis compared with the AB+PRP and AB+SDF-1α groups (both p < 0.05) after treatment for 2 and 4 weeks. These findings indicated that SDF-1α and PRP might exhibit synergistic effects to promote angiogenesis in early bone regeneration.

Toward a Better Regeneration through Implant-Mediated Immunomodulation: Harnessing the Immune Responses

Tissue repair/regeneration, after implantation or injury, involves comprehensive physiological processes wherein immune responses play a crucial role to enable tissue restoration, amidst the immune cells early-stage response to tissue damages. These cells break down extracellular matrix, clear debris, and secret cytokines to orchestrate regeneration. However, the immune response can also lead to abnormal tissue healing or scar formation if not well directed. This review first introduces the general immune response post injury, with focus on the major immune cells including neutrophils, macrophages, and T cells. Next, a variety of implant-mediated immunomodulation strategies to regulate immune response through physical, chemical, and biological cues are discussed. At last, various scaffold-facilitated regenerations of different tissue types, such as, bone, cartilage, blood vessel, and nerve system, by harnessing the immunomodulation are presented. Therefore, the most recent data in biomaterials and immunomodulation is presented here in a bid to shape expert perspectives, inspire researchers to go in new directions, and drive development of future strategies focusing on targeted, sequential, and dynamic immunomodulation elicited by implants.

The Current Status of Mesenchymal Stromal Cells: Controversies, Unresolved Issues and Some Promising Solutions to Improve Their Therapeutic Efficacy

Mesenchymal stromal cells (MSCs) currently constitute the most frequently used cell type in advanced therapies with different purposes, most of which are related with inflammatory processes. Although the therapeutic efficacy of these cells has been clearly demonstrated in different disease animal models and in numerous human phase I/II clinical trials, only very few phase III trials using MSCs have demonstrated the expected potential therapeutic benefit. On the other hand, diverse controversial issues on the biology and clinical applications of MSCs, including their specific phenotype, the requirement of an inflammatory environment to induce immunosuppression, the relevance of the cell dose and their administration schedule, the cell delivery route (intravascular/systemic vs. local cell delivery), and the selected cell product (i.e., use of autologous vs. allogeneic MSCs, freshly cultured vs. frozen and thawed MSCs, MSCs vs. MSC-derived extracellular vesicles, etc.) persist. In the current review article, we have addressed these issues with special emphasis in the new approaches to improve the properties and functional capabilities of MSCs after distinct cell bioengineering strategies.

Tracking and Imaging of Transplanted Stem Cells in Animals

The shortage of organ donors has contributed to the rapid development of cell-based therapy in which stem cells are transplanted and administered to repair or regenerate damaged tissues or organs. The common sources of stem cells are embryonic, mesenchymal, stromal, and induced pluripotent cells. Despite the popularity of stem cell therapy, evaluation of the therapeutic efficiency of transplanted stem cells and their tracking in vivo remains a major challenge. Current imaging modalities such as magnetic resonance imaging, radionuclide imaging, and positron emission tomography have certain limitations such as toxicity, shorter circulation time, and higher cost. Here, we describe near-infrared imaging methods to track and monitor stem cell recruitment to the site of injury.

Update on Nanoparticle-Based Drug Delivery System for Anti-inflammatory Treatment

Nanobiotechnology plays an important role in drug delivery, and various kinds of nanoparticles have demonstrated new properties, which may provide opportunities in clinical treatment. Nanoparticle-mediated drug delivery systems have been used in anti-inflammatory therapies. Diseases, such as inflammatory bowel disease, rheumatoid arthritis, and osteoarthritis have been widely impacted by the pathogenesis of inflammation. Efficient delivery of anti-inflammatory drugs can reduce medical dosage and improve therapeutic effect. In this review, we discuss nanoparticles with potential anti-inflammatory activity, and we present a future perspective regarding the application of nanomedicine in inflammatory diseases.

Stromal Cell-Derived Factor-1a Autocrine/Paracrine Signaling Contributes to Spatiotemporal Gradients in the Brain

INTRODUCTION

Stromal cell derived factor-1a (SDF-1a) and its receptor CXCR4 modulate stem cell recruitment to neural injury sites. SDF-1a gradients originating from injury sites contribute to chemotactic cellular recruitment. To capitalize on this injury-induced cell recruitment, further investigation of SDF-1a/CXCR4 signaling dynamics are warranted. Here, we studied how exogenous SDF-1a delivery strategies impact spatiotemporal SDF-1a levels and the role autocrine/paracrine signaling plays.

METHODS

We first assessed total SDF-1a and CXCR4 levels over the course of 7 days following intracortical injection of either bolus SDF-1a or SDF-1a loaded nanoparticles in CXCR4-EGFP mice. We then investigated cellular contributors to SDF-1a autocrine/paracrine signaling via time course in vitro measurements of SDF-1a and CXCR4 gene expression following exogenous SDF-1a application. Lastly, we created mathematical models that could recapitulate our in vivo observations.

RESULTS

In vivo, we found sustained total SDF-1a levels beyond 3 days post injection, indicating endogenous SDF-1a production. We confirmed in vitro that microglia, astrocytes, and brain endothelial cells significantly change SDF-1a and CXCR4 expression after exposure. We found that diffusion-only based mathematical models were unable to capture in vivo SDF-1a spatial distribution. Adding autocrine/paracrine mechanisms to the model allowed for SDF-1a temporal trends to be modeled accurately, indicating it plays an essential role in SDF-1a sustainment.

CONCLUSIONS

We conclude that autocrine/paracrine dynamics play a role in endogenous SDF-1a levels in the brain following exogenous delivery. Implementation of these dynamics are necessary to improving SDF-1a delivery strategies. Further, mathematical models introduced here may be utilized in predicting future outcomes based upon new biomaterial designs.

Skeletal Stem Cells as the Developmental Origin of Cellular Niches for Hematopoietic Stem and Progenitor Cells

The skeletal system is a highly complex network of mesenchymal, hematopoietic, and vasculogenic stem cell lineages that coordinate the development and maintenance of defined microenvironments, so-called niches. Technological advancements in recent years have allowed for the dissection of crucial cell types as well as their autocrine and paracrine signals that regulate these niches during development, homeostasis, regeneration, and disease. Ingress of blood vessels and bone marrow hematopoiesis are initiated by skeletal stem cells (SSCs) and their more committed downstream lineage cell types that direct shape and form of skeletal elements. In this chapter, we focus on the role of SSCs as the developmental origin of niches for hematopoietic stem and progenitor cells. We discuss latest updates in the definition of SSCs, cellular processes establishing and maintaining niches, as well as alterations of stem cell microenvironments promoting malignancies. We conclude with an outlook on future studies that could take advantage of SSC-niche engineering as a basis for the development of new therapeutic tools to not only treat bone-related diseases but also maladies stemming from derailed niche dynamics altering hematopoietic output.

The Possible Uses and Challenges of Nanomaterials in Mast Cell Research

Mast cells are tissue-resident immune cells that are involved in inflammation and fibrosis but also serve beneficial roles, including tissue maintenance, angiogenesis, pathogen clearance, and immunoregulation. Their multifaceted response and the ability of their mediators to target multiple organs and tissues means that mast cells play important roles in numerous conditions, including asthma, atopic dermatitis, drug sensitivities, ischemic heart disease, Alzheimer disease, arthritis, irritable bowel syndrome, infections (parasites, bacteria and viruses), and cancer. As a result, mast cells have become an important target for drug discovery and diagnostic research. Recent work has focused on applying novel nanotechnologies to explore cell biology. In this brief review, we will highlight the use of nanomaterials to modify mast cell functions and will discuss the potential of these technologies as research tools for understanding mast cell biology.

Stem cell recruitment based on scaffold features for bone tissue engineering

Stem-cell based therapy strategies are promising approaches for the treatment of bone defects. However, extensive cell expansion steps, the low rate of cell survival and uncontrolled differentiation of stem cells transplanted into the body currently remain key challenges in advancing stem cell therapeutics. An alternative strategy is to use specifically designed bone scaffolds to recruit endogenous stem cells upon implantation and to stimulate new bone formation and remodeling. Stem cell recruitment based on scaffold features for bone tissue engineering relies on the development of scaffolds that can effectively mobilize and recruit endogenous stem cells to the implantation site. This article addresses the recent advances in the recruitment of endogenous stem cells in applications of bone scaffolds, particularly focusing on chemical modification and physical characteristic modification of the scaffold for endogenous stem cell homing and recruitment. Finally, the continuing challenges and future directions of scaffold-based stem cell recruitment are discussed.

Chemokine SDF1 Mediated Bone Regeneration Using Biodegradable Poly(D,L-lactide-co-glycolide) 3D Scaffolds and Bone Marrow-Derived Mesenchymal Stem Cells: Implication for the Development of an "Off-the-Shelf" Pharmacologically Active Construct

There is an increasing need for bone substitutes for reconstructive orthopedic surgery following removal of bone tumors. Despite the advances in bone regeneration, the use of autologous mesenchymal stem cells (MSC) presents a significant challenge, particularly for the treatment of large bone defects in cancer patients. This study aims at developing new chemokine-based technology to generate biodegradable scaffolds that bind pharmacologically active proteins for regeneration/repair of target injured tissues in patients. Primary MSC were cultured from the uninvolved bone marrow (BM) of cancer patients and further characterized for "stemness". Their ability to differentiate into an osteogenic lineage was studied in 2D cultures as well as on 3D macroporous PLGA scaffolds incorporated with biomacromolecules bFGF and homing factor chemokine stromal-cell derived factor-1 (SDF1). MSC from the uninvolved BM of cancer patients exhibited properties similar to that reported for MSC from BM of healthy individuals. Macroporous PLGA discs were prepared and characterized for pore size, architecture, functional groups, thermostability, and cytocompatibility by ESEM, FTIR, DSC, and CCK-8 dye proliferation assay, respectively. It was observed that the MSC+PLGA+bFGF+SDF1 construct cultured for 14 days supported significant cell growth, osteo-lineage differentiation with increased osteocalcin expression, alkaline phosphatase secretion, calcium mineralization, bone volume, and soluble IL6 compared to unseeded PLGA and PLGA+MSC, as analyzed by confocal microscopy, biochemistry, ESEM, microCT imaging, flow cytometry, and EDS. Thus, chemotactic biomacromolecule SDF1-guided tissue repair/regeneration ability of MSC from cancer patients opens up the avenues for development of "off-the-shelf" pharmacologically active construct for optimal repair of the target injured tissue in postsurgery cancer patients, bone defects, damaged bladder tissue, and radiation-induced skin/mucosal lesions.

Antifibrotic strategies for medical devices

A broad range of medical devices initiate an immune reaction known as the foreign body response (FBR) upon implantation. Here, collagen deposition at the surface of the implant occurs as a result of the FBR, ultimately leading to fibrous encapsulation and, in many cases, reduced function or failure of the device. Despite significant efforts, the prevention of fibrotic encapsulation has not been realized at this point in time. However, many next-generation medical technologies including cellular therapies, sensors and devices depend on the ability to modulate and control the FBR. For these technologies to become viable, significant advances must be made in understanding the underlying mechanism of this response as well as in the methods modulating this response. In this review, we highlight recent advances in the development of materials and coatings providing a reduced FBR and emphasize key characteristics of high-performing approaches. We also provide a detailed overview of the state-of-the-art in strategies relying on controlled drug release, the surface display of bioactive signals, materials-based approaches, and combinations of these approaches. Finally, we offer perspectives on future directions in this field.

Integration of Islet/Beta-Cell Transplants with Host Tissue Using Biomaterial Platforms

Cell-based therapies are emerging for type I diabetes mellitus (T1D), an autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells, as a means to provide long-term restoration of glycemic control. Biomaterial scaffolds provide an opportunity to enhance the manufacturing and transplantation of islets or stem cell-derived β-cells. In contrast to encapsulation strategies that prevent host contact with the graft, recent approaches aim to integrate the transplant with the host to facilitate glucose sensing and insulin distribution, while also needing to modulate the immune response. Scaffolds can provide a supportive niche for cells either during the manufacturing process or following transplantation at extrahepatic sites. Scaffolds are being functionalized to deliver oxygen, angiogenic, anti-inflammatory, or trophic factors, and may facilitate cotransplantation of cells that can enhance engraftment or modulate immune responses. This local engineering of the transplant environment can complement systemic approaches for maximizing β-cell function or modulating immune responses leading to rejection. This review discusses the various scaffold platforms and design parameters that have been identified for the manufacture of human pluripotent stem cell-derived β-cells, and the transplantation of islets/β-cells to maintain normal blood glucose levels.

Biomaterial Based Strategies for Engineering New Lymphatic Vasculature

The lymphatic system is essential for tissue regeneration and repair due to its pivotal role in resolving inflammation, immune cell surveillance, lipid transport, and maintaining tissue homeostasis. Loss of functional lymphatic vasculature is directly implicated in a variety of diseases, including lymphedema, obesity, and the progression of cardiovascular diseases. Strategies that stimulate the formation of new lymphatic vessels (lymphangiogenesis) could provide an appealing new approach to reverse the progression of these diseases. However, lymphangiogenesis is relatively understudied and stimulating therapeutic lymphangiogenesis faces challenges in precise control of lymphatic vessel formation. Biomaterial delivery systems could be used to unleash the therapeutic potential of lymphangiogenesis for a variety of tissue regenerative applications due to their ability to achieve precise spatial and temporal control of multiple therapeutics, direct tissue regeneration, and improve the survival of delivered cells. In this review, the authors begin by introducing therapeutic lymphangiogenesis as a target for tissue regeneration, then an overview of lymphatic vasculature will be presented followed by a description of the mechanisms responsible for promoting new lymphatic vessels. Importantly, this work will review and discuss current biomaterial applications for stimulating lymphangiogenesis. Finally, challenges and future directions for utilizing biomaterials for lymphangiogenic based treatments are considered.

Antibiotic eluting sinus stents

OBJECTIVES

Chronic rhinosinusitis (CRS) is a multifactorial disease affecting up to 16% of the United States population and disproportionately affecting the cystic fibrosis (CF) patient population. Despite treating the underlying infection, the use of systemic antibiotics has shown little efficacy in alleviation of symptom burden. This review seeks to discuss recent research on novel antibiotic eluting stent therapy in vitro and within animal models as well as the factors that contribute to its efficacy.

DATA SOURCES

PubMed literature review.

REVIEW METHODS

A review of all published literature related to antibiotic eluting sinus stents was conducted to integrate and summarize this innovative approach to chronic sinus infections.

RESULTS

Placement of the ciprofloxacin sinus stent (CSS) and ciprofloxacin-ivacaftor sinus stent (CISS) exhibited improvement in endoscopic and radiographic findings in rabbit CRS models. While the CSS showed an overall trend toward improvement in microscopic findings and a reduction in biofilm mass, there remained a significant quantity of planktonic bacteria due to antibiotic depletion from an initial burst release in the first 48 hours of stent placement. The CISS and ciprofloxacin-azithromycin sinus stents (CASSs) exhibited controlled antibiotic release over the study period leading to greatly reduced planktonic bacterial load and biofilm mass. In vitro studies indicate that CASS may be just as efficacious at reducing biofilm mass.

CONCLUSION

Antibiotic eluting sinus stents show significant promise as a novel therapeutic strategy for CRS. The CISS may have particular promise for the CF patient population by addressing both the infectious and genetic components of disease. Animal studies demonstrate significant promise for translation into human studies. Human clinical trials are warranted to determine the efficacy of antibiotic sinus stents in human patients.

LEVEL OF EVIDENCE

NA.

Multifunctional Supramolecular Hydrogel for Prevention of Epidural Adhesion after Laminectomy

Postoperative epidural adhesion remains a clinically challenging problem in spine surgery. Currently there are no effective and safe antifibrotic and antiadhesion biomaterials that have been specifically developed for this complication in clinical practice. Herein we designed and engineered an advanced antiadhesion hydrogel with multiple functionalities, including temperature-responsive gelation, self-healing, tissue adhesiveness, antioxidation, anti-inflammation, and antifibrosis. This multifunctional supramolecular hydrogel can be facilely constructed by integrating three functional modules, i.e., a thermosensitive triblock copolymer, poloxamer 407 (PX); a reactive oxygen species-eliminating and anti-inflammatory nanoparticle (TPCD NP); and an adhesion-enhancing compound, tannic acid (TA). The optimal formulation (PXNT) was hierarchically screened based on in vitro properties and in vivo activities. Therapeutically, local treatment with PXNT hydrogel effectively prevented epidural fibrosis and adhesion after laminectomy in both rats and rabbits. Of note, PXNT hydrogel showed more beneficial efficacy than different control thermosensitive hydrogels and a commercially available barrier product, Interceed. Mechanistically, PXNT hydrogel significantly attenuated local oxidative stress, inhibited inflammatory responses, and reduced fibrotic tissue formation. Moreover, treatment with PXNT hydrogel did not cause systemic adverse effects and neurological symptoms. Consequently, PXNT hydrogel is a highly promising biomaterial for preventing postlaminectomy epidural adhesion and adhesions after other surgeries.

Stimulating pro-reparative immune responses to prevent adverse cardiac remodelling: consensus document from the joint 2019 meeting of the ESC Working Groups of cellular biology of the heart and myocardial function

Cardiac injury may have multiple causes, including ischaemic, non-ischaemic, autoimmune, and infectious triggers. Independent of the underlying pathophysiology, cardiac tissue damage induces an inflammatory response to initiate repair processes. Immune cells are recruited to the heart to remove dead cardiomyocytes, which is essential for cardiac healing. Insufficient clearance of dying cardiomyocytes after myocardial infarction (MI) has been shown to promote unfavourable cardiac remodelling, which may result in heart failure (HF). Although immune cells are integral key players of cardiac healing, an unbalanced or unresolved immune reaction aggravates tissue damage that triggers maladaptive remodelling and HF. Neutrophils and macrophages are involved in both, inflammatory as well as reparative processes. Stimulating the resolution of cardiac inflammation seems to be an attractive therapeutic strategy to prevent adverse remodelling. Along with numerous experimental studies, the promising outcomes from recent clinical trials testing canakinumab or colchicine in patients with MI are boosting the interest in novel therapies targeting inflammation in cardiovascular disease patients. The aim of this review is to discuss recent experimental studies that provide new insights into the signalling pathways and local regulators within the cardiac microenvironment promoting the resolution of inflammation and tissue regeneration. We will cover ischaemia- and non-ischaemic-induced as well as infection-related cardiac remodelling and address potential targets to prevent adverse cardiac remodelling.