Remendable Cross-Linked Alginate/Gelatin Hydrogels Incorporating Nanofibers for Wound Repair and Regeneration.

Wound dressings made from natural-derived polymers are highly valued for their biocompatibility, biodegradability, and biofunctionality. However, natural polymer-based hydrogels can come with their own set of limitations, such as low mechanical strength, limited cell affinity, and the potential cytotoxicity of cross-linkers, which delineate the boundaries of their usage and hamper their practical application. To overcome the limitation of natural-derived polymers, this study utilized a mixture of oxidized alginate and gelatin with 5 mg/mL polycaprolactone (PCL):gelatin nanofiber fragments at a ratio of 7:3 (OGN-7) to develop a hydrogel composite wound dressing that can be injected and has the ability to be remended. The in situ formation of the remendable hydrogel is facilitated by dual cross-linking of oxidized alginate chains with gelatin and PCL/gelatin nanofibers through Schiff-base mechanisms, supported by the physical integration of nanofibers, thereby obviating the need for additional cross-linking agents. Furthermore, OGN-7 exhibits increased stiffness (γ = 79.4-316.3%), reduced gelation time (543 ± 5 to 475 ± 5 s), improved remendability of the hydrogel, and excellent biocompatibility. Notably, OGN-7 achieves full fusion within 1 h of incubation and maintains structural integrity under external stress, effectively overcoming the inherent mechanical weaknesses of natural polymer-based dressings and enhancing biofunctionality. The therapeutic efficacy of OGN-7 was validated through a full-thickness in vivo wound healing analysis, which demonstrated that OGN-7 significantly accelerates wound closure compared to alginate-based dressings and control groups. Histological analysis further revealed that re-epithelialization and collagen deposition were markedly enhanced in the regenerating skin of the OGN-7 group, confirming the superior therapeutic performance of OGN-7. In summary, OGN-7 optimized the synergistic effects of natural polymers, which enhances their collective functionality as a wound dressing and expands their utility across diverse biomedical applications.

Children's communication repair strategies: Online versus face-to-face interaction.

INTRODUCTION: One's ability to repair communication breakdown is an important pragmatic language skill. The present study examined children's communication repair strategies between online and face-to-face interactions using a reading comprehension task designed to probe for persistent clarification requests. METHODS: 4-6-year-old typically developing children (Age: M = 5.5years) completed a communication repair task. Online group (n = 17) completed the task online, face-to-face group(n = 22) met researchers in person. Children's responses were then categorized into verbal strategies, supplementary strategies, and nonresponses. RESULTS: Our results showed that children can effectively employ repair strategies when a communication breakdown occurs, regardless of the communication setting in response to a series of clarification requests. However, types and patterns of communication repair strategies varied between online and face-to-face interactions. Children in online interaction showed higher use of repetition and suprasegmental strategies than did their face-to-face peers. In contrast, children in face-to-face interaction demonstrated more frequent use of revision and addition. Also, we examined the relationship between repair strategy and children's language skills. The results showed that children with better language skills used more addition, which is a more complex strategy than suprasegmental and nonresponse, and tried to use repair strategies effectively in an attempt to repair their statements as clarification requests proceeded. CONCLUSION: It is important to understand different trends of pragmatic skills of children across online and face-to-face interaction. Guidance on the effective strategy to repair communication breakdowns depending on the different contexts needs to be considered for the successful use of online learning and telepractice.

A micro-fragmented collagen gel as a cell-assembling platform for critical limb ischemia repair.

Critical limb ischemia (CLI) is a devastating disease characterized by the progressive blockage of blood vessels. Although the paracrine effect of growth factors in stem cell therapy made it a promising angiogenic therapy for CLI, poor cell survival in the harsh ischemic microenvironment limited its efficacy. Thus, an imperative need exists for a stem-cell delivery method that enhances cell survival. Here, a collagen microgel (CMG) cell-delivery scaffold (40 × 20 µm) was fabricated via micro-fragmentation from collagen-hyaluronic acid polyionic complex to improve transplantation efficiency. Culturing human adipose-derived stem cells (hASCs) with CMG enabled integrin receptors to interact with CMG to form injectable 3-dimensional constructs (CMG-hASCs) with a microporous microarchitecture and enhanced mass transfer. CMG-hASCs exhibited higher cell survival (p < 0.0001) and angiogenic potential in tube formation and aortic ring angiogenesis assays than cell aggregates. Injection of CMG-hASCs intramuscularly into CLI mice increased blood perfusion and limb salvage ratios by 40 % and 60 %, respectively, compared to cell aggregate-treated mice. Further immunofluorescent analysis revealed that transplanted CMG-hASCs have greater muscle regenerative and angiogenic potential, with enhanced cell survival than cell aggregates (p < 0.05). Collectively, we propose CMG as a cell-assembling platform and CMG-hASCs as promising therapeutics to treat CLI.

Functionally enhanced cell spheroids for stem cell therapy: Role of TIMP1 in the survival and therapeutic effectiveness of stem cell spheroids.

Stem cell therapy has emerged as a promising regenerative medicine strategy but is limited by poor cell survival, leading to low therapeutic outcomes. We developed cell spheroid therapeutics to overcome this limitation. We utilized solid-phase FGF2 to form functionally enhanced cell spheroid-adipose derived (FECS-Ad), a type of cell spheroid that preconditions cells with intrinsic hypoxia to increase the survival of transplanted cells. We demonstrated an increase in hypoxia-inducible factor 1-alpha (HIF-1α) levels in FECS-Ad, which led to the upregulation of tissue inhibitor of metalloproteinase 1 (TIMP1). TIMP1 enhanced the survival of FECS-Ad, presumably through the CD63/FAK/Akt/Bcl2 anti-apoptotic signaling pathway. Cell viability of transplanted FECS-Ad was reduced by TIMP1 knockdown in an in vitro collagen gel block and a mouse model of critical limb ischemia (CLI). TIMP1 knockdown in FECS-Ad inhibited angiogenesis and muscle regeneration induced by FECS-Ad transplanted into ischemic mouse tissue. Genetic overexpression of TIMP1 in FECS-Ad further promoted the survival and therapeutic efficacy of transplanted FECS-Ad. Collectively, we suggest that TIMP1 acts as a key survival factor to improve the survival of transplanted stem cell spheroids, which provides scientific evidence for enhanced therapeutic efficacy of stem cell spheroids, and FECS-Ad as a potential therapeutic agent to treat CLI. STATEMENT OF SIGNIFICANCE: We used FGF2-tethered substrate platform to form adipose-derived stem cell spheroids, as we named as functionally enhanced cell spheroid-adipose derived (FECS-Ad). In this paper, we showed that intrinsic hypoxia of spheroids upregulated expression of HIF-1α, which in turn upregulated expression of TIMP1. Our paper highlights TIMP1 as a key survival factor to improve survival of transplanted stem cell spheroids. We believe that our study has a very strong scientific impact as extending transplantation efficiency is essential for successful stem cell therapy.

Hydrogel/Nanofiber Composite Wound Dressing Optimized for Skin Layer Regeneration through the Mechanotransduction-Based Microcellular Environment.

Wound dressings have been designed to provide the optimal environment to fibroblasts, keratinocytes, and macrophages to promote wound healing while inhibiting potential microbial infection. Gelatin methacrylate (GelMA) is a photopolymerizable hydrogel with a gelatin backbone that contains natural cell binding motifs such as arginine-glycine-aspartic acid (RGD) and MMP-sensitive degradation sites, making it an ideal material for wound dressing. However, GelMA alone is unable to stably protect the wound and regulate cellular activities due to its weak mechanical properties and nonmicropatterned surface, limiting its application as a wound dressing. Herein, we report the development of a hydrogel-nanofiber composite wound dressing utilizing GelMA and poly(caprolactone) (PCL)/gelatin nanofiber, which can systematically manage the skin regeneration process with an enhanced mechanical property and micropatterned surface. GelMA sandwiched between electrospun aligned and interlaced nanofibers that mimic epidermis and dermis layers, respectively, increased the stiffness of the resulting hydrogel composite with a comparable swelling rate as GelMA. Fabricated hydrogel composite was determined to be biocompatible and nontoxic. In addition to the beneficial effect of GelMA in accelerating wound healing, subsequent histological analysis revealed upregulated re-epithelialization of granulation tissue and deposition of mature collagen. Hydrogel composite interacted with fibroblasts to regulate their morphology, proliferation, and collagen synthesis, as well as the expression of α-SMA, TGF-ß, and collagen I and III during the wound healing process both in vitro and in vivo. Taken together, we propose hydrogel/nanofiber composite as a wound dressing of the next generation that can induce skin tissue layer regeneration beyond the basic wound closure promotion of present dressings.

FGF2-primed 3D spheroids producing IL-8 promote therapeutic angiogenesis in murine hindlimb ischemia.

Peripheral artery disease is a progressive, devastating disease that leads to critical limb ischemia (CLI). Therapeutic angiogenesis using stem cell therapy has emerged as a promising approach for its treatment; however, adapting cell-based therapy has been limited by poor cell survival and low treatment efficiency. To overcome unmet clinical needs, we developed a fibroblast growth factor 2 (FGF2)-immobilized matrix that enabled control of cell adhesion to the surface and exerted a priming effect on the cell. Human adipose-derived stem cells (hASCs) grown in this matrix formed a functionally enhanced cells spheroid (FECS-Ad) that secreted various angiogenic factors including interleukin-8 (IL-8). We demonstrated that IL-8 was upregulated by the FGF2-mediated priming effect during FECS-Ad formation. Immobilized FGF2 substrate induced stronger IL-8 expression than soluble FGF2 ligands, presumably through the FGFR1/JNK/NF-κB signaling cascade. In IL-8-silenced FECS-Ad, vascular endothelial growth factor (VEGF) expression was decreased and angiogenic potential was reduced. Intramuscular injection of FECS-Ad promoted angiogenesis and muscle regeneration in mouse ischemic tissue, while IL-8 silencing in FECS-Ad inhibited these effects. Taken together, our data demonstrate that IL-8 contributes to therapeutic angiogenesis and suggest that FECS-Ad generated using the MBP-FGF2 matrix might provide a reliable platform for developing therapeutic agents to treat CLI.

The development of a functional human small intestinal epithelium model for drug absorption.

Advanced technologies are required for generating human intestinal epithelial cells (hIECs) harboring cellular diversity and functionalities to predict oral drug absorption in humans and study normal intestinal epithelial physiology. We developed a reproducible two-step protocol to induce human pluripotent stem cells to differentiate into highly expandable hIEC progenitors and a functional hIEC monolayer exhibiting intestinal molecular features, cell type diversity, and high activities of intestinal transporters and metabolic enzymes such as cytochrome P450 3A4 (CYP3A4). Functional hIECs are more suitable for predicting compounds metabolized by CYP3A4 and absorbed in the intestine than Caco-2 cells. This system is a step toward the transition from three-dimensional (3D) intestinal organoids to 2D hIEC monolayers without compromising cellular diversity and function. A physiologically relevant hIEC model offers a novel platform for creating patient-specific assays and support translational applications, thereby bridging the gap between 3D and 2D culture models of the intestine.

Editor's Highlight: Congener-Specific Disposition of Chiral Polychlorinated Biphenyls in Lactating Mice and Their Offspring: Implications for PCB Developmental Neurotoxicity.

Chiral polychlorinated biphenyl (PCB) congeners have been implicated by laboratory and epidemiological studies in PCB developmental neurotoxicity. These congeners are metabolized by cytochrome P450 (P450) enzymes to potentially neurotoxic hydroxylated metabolites (OH-PCBs). The present study explores the enantioselective disposition and toxicity of 2 environmentally relevant, neurotoxic PCB congeners and their OH-PCB metabolites in lactating mice and their offspring following dietary exposure of the dam. Female C57BL/6N mice (8-weeks old) were fed daily, beginning 2 weeks prior to conception and continuing throughout gestation and lactation, with 3.1 µmol/kg bw/d of racemic 2,2',3,5',6-pentachlorobiphenyl (PCB 95) or 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) in peanut butter; controls received vehicle (peanut oil) in peanut butter. PCB 95 levels were higher than PCB 136 levels in both dams and pups, consistent with the more rapid metabolism of PCB 136 compared with PCB 95. In pups and dams, both congeners were enriched for the enantiomer eluting second on enantioselective gas chromatography columns. OH-PCB profiles in lactating mice and their offspring were complex and varied according to congener, tissue and age. Developmental exposure to PCB 95 versus PCB 136 differentially affected the expression of P450 enzymes as well as neural plasticity (arc and ppp1r9b) and thyroid hormone-responsive genes (nrgn and mbp). The results suggest that the enantioselective metabolism of PCBs to OH-PCBs may influence neurotoxic outcomes following developmental exposures, a hypothesis that warrants further investigation.