Development of Cell Culture Platforms for Study of Trabecular Meshwork Cells and Glaucoma Development.

BACKGROUND: Various cell culture platforms that could display native environmental cue-mimicking stimuli were developed, and effects of environmental cues on cell behaviors were studied with the cell culture platforms. Likewise, various cell culture platforms mimicking native trabecular meshwork (TM) composed of juxtacanalicular, corneoscleral and uveal meshwork located in internal scleral sulcus were used to study effects of environmental cues and/or drug treatments on TM cells and glaucoma development. Glaucoma is a disease that could cause blindness, and cause of glaucoma is not clearly identified yet. It appears that aqueous humor (AH) outflow resistance increased by damages on pathway of AH outflow can elevate intraocular pressure (IOP). These overall possibly contribute to development of glaucoma. METHODS: For the study of glaucoma, static and dynamic cell culture platforms were developed. Particularly, the dynamic platforms exploiting AH outflow-mimicking perfusion or increased IOP-mimicking increased pressure were used to study how perfusion or increased pressure could affect TM cells. Overall, potential mechanisms of glaucoma development, TM structures and compositions, TM cell culture platform types and researches on TM cells and glaucoma development with the platforms were described in this review. RESULTS AND CONCLUSION: This will be useful to improve researches on TM cells and develop enhanced therapies targeting glaucoma.

Effect of lyophilized gelatin-norbornene cryogel size on calvarial bone regeneration.

Molding processes with molds containing topographical structures have been used for fabrication of hydrogel and cryogel particles. However, they can involve difficulties in separation of fabricated particles with complex shape from the molds or repeated fabrication of the particles although the overall processes do not require much skill and equipment. In this study, molds with etched superhydrophobic patterns have been developed by etching polytetrafluoroethylene (PTFE) blocks in user-defined designs with a femtosecond (FS) laser-based etching system. Lyophilized cryogel particles with various designs and sizes were fabricated by molding precursors with these PTFE molds. Additionally, the clean and easy separation of particles from the molds allowed repeated fabrication of the particles. For an application, relatively 'big' gelatin-norbornene (GelNB) cryogel particles prepared via molding with polydimethylsiloxane (PDMS) molds, swelling in phosphate buffered saline (PBS) and slicing height in half and 'small' GelNB cryogel particles fabricated with the PTFE molds were fabricated. Then, they were used to study scaffold size effect on calvarial bone regeneration. The molds generated with the FS laser-based etching system can be useful for various applications that require the mass production of cryogel particles in various geometries.

Fibrous hydrogels by electrospinning: Novel platforms for biomedical applications.

Hydrogels, hydrophilic and biocompatible polymeric networks, have been used for numerous biomedical applications because they have exhibited abilities to mimic features of extracellular matrix (ECM). In particular, the hydrogels engineered with electrospinning techniques have shown great performances in biomedical applications. Electrospinning techniques are to generate polymeric micro/nanofibers that can mimic geometries of natural ECM by drawing micro/nanofibers from polymer precursors with electrical forces, followed by structural stabilization of them. By exploiting the electrospinning techniques, the fibrous hydrogels have been fabricated and utilized as 2D/3D cell culture platforms, implantable scaffolds, and wound dressings. In addition, some hydrogels that respond to external stimuli have been used to develop biosensors. For comprehensive understanding, this review covers electrospinning processes, hydrogel precursors used for electrospinning, characteristics of fibrous hydrogels and specific biomedical applications of electrospun fibrous hydrogels and highlight their potential to promote use in biomedical applications.

Hydroethanolic Extract of Fritillariae thunbergii Bulbus Alleviates Dextran Sulfate Sodium-Induced Ulcerative Colitis by Enhancing Intestinal Barrier Integrity.

The incidence of ulcerative colitis (UC), an inflammatory disorder of the gastrointestinal tract, has rapidly increased in Asian countries over several decades. To overcome the limitations of conventional drug therapies, including biologics for UC management, the development of herbal medicine-derived products has received continuous attention. In this study, we evaluated the beneficial effects of a hydroethanolic extract of Fritillariae thunbergii Bulbus (FTB) in a mouse model of DSS-induced UC. The DSS treatment successfully induced severe colonic inflammation and ulceration. However, the severity of colitis was reduced by the oral administration of FTB. Histopathological examination showed that FTB alleviated the infiltration of inflammatory cells (e.g., neutrophils and macrophages), damage to epithelial and goblet cells in the colonic mucosal layer, and fibrotic lesions. Additionally, FTB markedly reduced the gene expression of proinflammatory cytokines and extracellular matrix remodeling. Immunohistochemical analysis showed that FTB alleviated the decrease in occludin and zonula occludens-1 expression induced by DSS. In a Caco-2 monolayer system, FTB treatment improved intestinal barrier permeability in a dose-dependent manner and increased tight junction expression. Overall, FTB has potential as a therapeutic agent through the improvement of tissue damage and inflammation severity through the modulation of intestinal barrier integrity.

Network pharmacology-based identification of bioavailable anti-inflammatory agents from Psoralea corylifolia L. in an experimental colitis model.

ETHNOPHARMACOLOGICAL RELEVANCE: In traditional oriental medicine, the dried seeds of Psoralea corylifolia L. (PC) have been used to treat various diseases, including gastrointestinal, urinary, orthopedic, diarrheal, ulcer, and inflammatory disorders. AIM OF THE STUDY: Although its various biological properties are well-known, there is no information on the therapeutic effects and bioavailable components of PC against inflammatory bowel disease. Therefore, we focused on the relationship between hydroethanolic extract of PC (EPC) that ameliorates colitis in mice and bioactive constituents of EPC that suppress pro-inflammatory cytokines in macrophages. MATERIALS AND METHODS: We investigated the therapeutic effects of EPC in a dextran sulfate sodium-induced colitis mouse model and identified the orally absorbed components of EPC using UPLC-MS/MS analysis. In addition, we evaluated and validated the mechanism of action of the bioavailable constituents of EPC using network pharmacology analysis. The effects on nitric oxide (NO) and inflammatory cytokines were measured by Griess reagent and enzyme linked immunosorbent assay in lipopolysaccharide (LPS)-induced macrophages. RESULTS: In experimental colitis, EPC improved body weight loss, colon length shortening, and disease activity index. Moreover, EPC reduced the serum levels of pro-inflammatory cytokines and histopathological damage to the colon. Network pharmacological analysis identified 13 phytochemicals that were bioavailable following oral administration of EPC, as well as their potential anti-inflammatory effects. 11 identified EPC constituents markedly reduced the overproduction of NO, tumor necrosis factor-α, and/or interleukin-6 in macrophages induced by LPS. The LPS-induced expression of the nuclear factor kappa-light-chain-enhancer of activated B cells reporter gene was reduced by the 4 EPC constituents. CONCLUSIONS: The results indicate that the protective activity of EPC against colitis is a result of the additive effects of each constituent on the expression of inflammatory cytokines. Therefore, it suggests that 11 bioavailable phytochemicals of EPC could aid in the management of intestinal inflammation, and also provides useful insights into the clinical application of PC for the treatment of inflammatory bowel diseases.

Therapeutic effects of Pulsatilla koreana Nakai extract on ovalbumin-induced allergic rhinitis by inhibition of Th2 cell activation and differentiation via the IL-4/STAT6/GATA3 pathway.

Allergic rhinitis (AR), caused by immunoglobulin E (IgE)-mediated inflammation, generally occurs in the upper respiratory tract. T helper type 2 (Th2) cell-mediated cytokines, including interleukin (IL)-4, IL-5, and IL-13, are important factors in AR pathogenesis. Despite various treatment options, the difficulty in alleviating AR and pharmacological side effects necessitate development of new therapies. The root of Pulsatilla koreana Nakai (P. koreana), a pasque flower, has been used as a herbal medicine. However, its effects on AR remain unclear; therefore, we aimed to explore this subject in the current study. The therapeutic effects of P. koreana water extract (PKN) on the pathophysiological functions of the nasal mucosa was examined in ovalbumin (OVA)-induced AR mice. The effect of PKN on Th2 activation and differentiation was evaluated using concanavalin A-induced splenocytes and differentiated Th2 cells from naïve CD4+ T cells. We also investigated the effect of changes in JAK/STAT6/GATA3 signaling on IL-4-induced Th2 cells. In OVA-induced AR mice, PKN administration alleviated allergic nasal symptoms and decreased the total number of immune cells, lymphocytes, neutrophils, and eosinophils in nasal lavage fluid; serum levels of OVA-specific IgE, histamine, and IL-13 were also significantly reduced. PKN also ameliorated OVA-induced nasal mucosal tissue thickening by inhibiting inflammation and goblet cell hyperplasia. PKN treatment significantly inhibited Th2 activity and differentiation through the IL-4/STAT-6/GATA3 pathway in Th2 cells. PKN is an effective AR treatment with the potential to improve patients' daily lives by regulating the allergic inflammatory response induced by Th2 cells.

Effects of Alginate Oligosaccharide on Testosterone-Induced Benign Prostatic Hyperplasia in Orchiectomized Rats.

Benign prostatic hyperplasia (BPH) is an age-related disease of the urinary system that affects elderly men. Current treatments for BPH are associated with several adverse effects, thus highlighting the need for alternative agents. Alginate oligosaccharide (AOS), a water-soluble functional oligomer derived from brown algae, inhibits prostate cancer cell proliferation. However, the effects of AOS on BPH and the underlying molecular mechanisms remain unclear. Therefore, here, we aimed to investigate the therapeutic potential of AOS in BPH by using human benign prostatic epithelial cells (BPH-1) and a rat model of testosterone-induced BPH. Treatment with AOS inhibited in vitro and in vivo proliferation of prostatic epithelial cells and the testosterone-induced expression of androgen receptor (AR) and androgen-associated genes, such as those encoding 5α-reductase type 2 and prostate-specific antigen. Oral administration of AOS remarkably reduced the serum levels of dihydrotestosterone (DHT) and testosterone as well as the expression of proliferating cell nuclear antigen, inflammatory cytokines, and enzymes, which showed increased levels in prostatic tissues of rats with testosterone-induced BPH. Taken together, these data demonstrate that AOS suppresses testosterone-induced BPH in rats by downregulating AR and the expression of androgen-associated genes, supporting the hypothesis that AOS might be of potential use for the treatment of BPH.

Terminalia chebula Retz. extract ameliorates the symptoms of atopic dermatitis by regulating anti-inflammatory factors in vivo and suppressing STAT1/3 and NF-ĸB signaling in vitro.

BACKGROUND: Terminalia chebula (TC) is a traditional medicinal plant used for treating various diseases in humans. However, pharmacological mechanisms underlying the effects of TC in atopic treatment remain unelucidated. HYPOTHESIS/PURPOSE: We investigated the therapeutic effects of TC extract in a mouse model of atopic dermatitis (AD) in vivo and the anti-inflammatory mechanism in vitro. STUDY DESIGN/METHODS: For the in vivo study, AD was induced by Dermatophagoides farinae extract (Dfe) in NC/Nga mice. After 14 days of oral administration, the effects of TC concentrations of 30, 100, and 300 mg/kg were analyzed by assessing morphological changes visually; measuring serum levels of inflammatory chemokines/cytokines, IgE, histamine, MDC, TARC, RANTES, and TSLP using ELISA kits; and counting infiltrated mast cells. For in vitro analyses, we used IFNγ/TNF-α-stimulated human keratinocyte cell lines to study the mechanism of action. The production of chemokines/cytokines in the IFNγ/TNF-α-stimulated HaCaT cells was measured using ELISA and a bead array kit. The signaling pathways were analyzed by western blotting and the expression of the transcriptional factors using RT-PCR and luciferase assay. RESULTS: Administration of TC significantly alleviated AD-like symptoms in vivo and decreased the ear thickness, dermatitis score, keratinization, and mast cell infiltration. It also resulted in decreased serum levels of IgE, histamine, and inflammation-related mediators MDC, TARC, RANTES, and TSLP compared with those in the Dfe treatment group. Moreover, TC downregulated the expression of the inflammatory chemokines RANTES and MDC in IFNγ/TNF-α-stimulated HaCaT cells. TC inhibited phosphorylated STAT1/3 and NK-κB subunits and nuclear translocation of NF-κB. It also suppressed the transcription of IFNγ, IL-6, IL-8 and MCP-1 in the IFNγ/TNF-α-stimulated HaCaT cells. TC and its constituents, chebulic acid, gallic acid, corlagin, chebulanin, chbulagic acid, ellagic acid, and chebulinic acid, strongly inhibited the nuclear translocation of NF-κB, STAT1, and STAT3 and decreased the expression of inflammatory cytokines at the mRNA level. CONCLUSIONS: Overall, TC extract alleviated AD-like symptoms by regulating anti-inflammatory factors in vivo and suppressing STAT1/3 and NF-κB signaling in vitro. In addition, our results show the in vivo effect of partial improvements in AD, as well as the in vitro effect on inflammatory factors by the constituents of TC. This finding provides that TC extract and its components could be potential therapeutic drugs for AD.

Jammed Microgel-Based Inks for 3D Printing of Complex Structures Transformable via pH/Temperature Variations.

Structure changes mediated by anisotropic volume changes of stimuli-responsive hydrogels are useful for many research fields, yet relatively simple structured objects are mostly used due to limitation in fabrication methods. To fabricate complex 3 dimensional (3D) structures that undergo structure changes in response to external stimuli, jammed microgel-based inks containing precursors of stimuli-responsive hydrogels are developed for extrusion-based 3D printing. Specifically, the jammed microgel-based inks are prepared by absorbing precursors of poly(acrylic acid) or poly(N-isopropylacrylamide) in poly(acrylamide) (PAAm) microgels, and jamming them. The inks exhibit shear-thinning and self-healing properties that allow extrusion of the inks through a nozzle and rapid stabilization after printing. Stimuli-mediated volume changes are observed for the extruded structures when they are post-crosslinked by UV light to form interpenetrating networks of PAAm microgels and stimuli-responsive hydrogels. Using this method, a dumbbell-shaped object that can transform to a biconvex shape, and a gripper that can grasp and lift an object in response to stimuli are 3D-printed. The jammed microgel-based 3D printing strategy is a versatile method useful for variety of applications as diverse types of monomers absorbable in the microgels can be used to fabricate complex 3D objects transformable by external stimuli.

A time-dependently regulated gene network reveals that Aspergillus protease affects mitochondrial metabolism and airway epithelial cell barrier function via mitochondrial oxidants.

The airway epithelium maintains tight barrier integrity to prevent penetration of pathogens; thus, impairment of the barrier function is an important and common histological feature in asthmatic patients. Proteolytic allergens from fungi, pollen, and house dust mites can disrupt epithelial barrier integrity, but the mechanism remains unclear. Aspergillus oryzae protease (AP)-induced mitochondrial reactive oxygen species (ROS) contribute to the epithelial inflammatory response. However, as mitochondrial ROS affect various cellular functions, such as metabolism, cell death, cell proliferation, and redox homeostasis through signal transduction, it is difficult to understand the detailed action mechanism of AP by measuring changes in a single gene or protein of a specific signaling pathway. Moreover, mitochondrial ROS can directly oxidize DNA to activate transcription, thereby affecting the expression of various genes at the transcriptional level. Therefore, we conducted whole-genome analysis and used a network-based approach to understand the effect of AP and AP-induced mitochondrial ROS in human primary airway epithelial cells and to evaluate the mechanistic basis for AP-mediated epithelial barrier dysfunction. Our results indicate that production of mitochondrial ROS following AP exposure induce mitochondrial dysfunction at an early stage. Over time, changes in genome expression were further expanded without remaining mitochondrial ROS. Specifically, genes involved in the apoptotic functions and intercellular junctions were affected, consequently impairing the cellular barrier integrity. This change was recovered by scavenging mitochondrial ROS at an early point after exposure to AP. In conclusion, our findings indicate that instantly increased mitochondrial ROS at the time of exposure to allergenic proteases consequently induces epithelial barrier dysfunction at a later time point, resulting in pathological changes. These data suggest that antioxidant therapy administered immediately after exposure to proteolytic antigens may be effective in maintaining epithelial barrier function.

Angelica gigas extract ameliorates allergic rhinitis in an ovalbumin-induced mouse model by inhibiting Th2 cell activation.

BACKGROUND: Allergic rhinitis (AR) is a well-documented type 2 helper T (Th2) cell-mediated allergic disease that is accompanied by symptoms such as nasal rubbing, sneezing, itching, and rhinorrhea. Angelica gigas (AG) is traditional oriental medicine, and its dried root is widely used for the treatment of anemia, as a sedative, and as a blood tonic. PURPOSE: The effects of AG on allergic diseases including AR are currently unclear; therefore, we aimed to investigate the effects of AG extract (AG-Ex) in ameliorating AR. STUDY DESIGN/METHODS: The cytotoxicity of AG-Ex was analyzed by EZ-Cytox or MTS assay in splenocytes, differentiated Th2 cells, and human nasal epithelial cells (HNEpC). The changes of Th2 cells activation were determined by the secretion levels of cytokines and chemokines using cytometric bead array in splenocytes and differentiated Th2 cells. The expression levels of eotaxin-3 and periostin were analyzed using an ELISA. AR was induced by ovalbumin in BALB/c mice and the ameliorating effects of AG-Ex were assessed by their clinical symptoms. RESULTS: The secretion of Th2 cytokines such as IL-4, IL-5, and IL-13 was inhibited by the AG-Ex treatment in the splenocytes and differentiated Th2 cells. The treatment also suppressed allergic responses including the secretion of eotaxin-3 and periostin in human nasal epithelial cells (HNEpC). Moreover, the administration of AG-Ex to the OVA-induced AR mice improved their clinical symptoms, including behavioral tests, immune cell counts, histopathological analysis, and changes in serum parameters. CONCLUSION: The results of this study suggest that AG-Ex ameliorates AR by inhibiting Th2 cell activation and could thus be utilized as a treatment for Th2-mediated allergic diseases in the future.

Cimicifugae Rhizoma Extract Attenuates Oxidative Stress and Airway Inflammation via the Upregulation of Nrf2/HO-1/NQO1 and Downregulation of NF-κB Phosphorylation in Ovalbumin-Induced Asthma.

Cimicifugae Rhizoma has been used as a medicinal herb for fever, pain, and inflammation in East Asia. We conducted this study because the effect of Cimicifugae Rhizoma extract (CRE) on allergic asthma has not yet been evaluated. To induce allergic airway inflammation, we intraperitoneally injected ovalbumin (OVA) mixed with aluminum hydroxide into mice twice at intervals of 2 weeks (Days 0 and 14) and then inhaled them thrice with 1% OVA solution using a nebulizer (Days 21 to 23). CRE (30 and 100 mg/kg) was administered orally daily for 6 days (Days 18 to 23). The mice showed remarkable reduction in allergic inflammation at 100 mg/kg of CRE, as evidenced by decreased inflammatory cell counts, pro-inflammatory cytokine levels, OVA-specific immunoglobulin E level, airway hyperresponsiveness, and production of mucus. Additionally, these effects were involved with the enhancement of heme oxygenase-1 (HO-1), NAD(P)H: quinone oxidoreductase (NQO1), and nuclear factor erythroid 2-related factor 2 (Nrf2) expression and reduction of nuclear factor-κB (NF-κB) phosphorylation and matrix metalloproteinase-9 expression. Our findings indicated that CRE effectively protected against OVA-induced inflammation and oxidative stress via upregulation of the Nrf2/HO-1/NQO1 signaling and downregulation of NF-κB phosphorylation in asthma caused by OVA.

Extracts of Phyllostachys pubescens Leaves Represses Human Steroid 5-Alpha Reductase Type 2 Promoter Activity in BHP-1 Cells and Ameliorates Testosterone-Induced Benign Prostatic Hyperplasia in Rat Model.

Benign prostatic hyperplasia (BPH) is the most common symptomatic abnormality of the human prostate characterized by uncontrolled proliferation of the prostate gland. In this study, we investigated the effect of bamboo, Phyllostachys pubescens, leaves extract (PPE) on human 5α-reductase type 2 (SRD5A2) gene promoter activity in human prostate cell lines and the protective effect of PPE on a testosterone-induced BPH rat model. PPE repressed human SRD5A2 promoter activity and its mRNA expression. The rats treated with PPE for 4 weeks showed a significantly attenuated prostate weight compared to vehicle control. PPE-treated rats also showed reduced serum dihydrotestosterone, testosterone, prostate-specific antigen, and SRD5A2 levels by testosterone injection. Quantitative real-time polymerase chain reaction showed that PPE treatment significantly decreased mRNA expression of SRD5A2, androgen receptor (AR), proliferating cell nuclear antigen (PCNA), and fibroblast growth factor 2 compared with the vehicle-treated, testosterone-injected rats in the prostate. Furthermore, PPE treatment showed reduced AR, PCNA, and tumor necrosis factor alpha expression in the prostate via immunohistofluorescence staining. In conclusion, oral administration of PPE prevented and inhibited the development and progression of enlarged prostate lesions in testosterone-induced animal models through various anti-proliferative and anti-inflammatory pharmacological effects and induced suppression of SRD5A2 gene expression.

Phytochemical Characterization for Quality Control of Phyllostachys pubescens Leaves Using High-Performance Liquid Chromatography Coupled with Diode Array Detector and Tandem Mass Detector.

Phyllostachys pubescens leaves are cultivated in a number of Asian countries and have been used for antipyretic and diuretic effects since ancient times, especially in Korea. The purpose of this study was to develop and validate of analytical method for quality control of P. pubescens leaves using high-performance liquid chromatography with diode array detector (HPLC-DAD) and liquid chromatography with tandem mass spectrometry (LC-MS/MS) detection. HPLC-DAD analysis was conducted with a Gemini C18 column, and distilled water-acetonitrile (both with 0.1% (v/v) formic acid) mobile-phase system. For the LC-MS/MS analysis, all markers were separated with a Waters ACQUITY UPLC BEH C18 column and gradient flow system of distilled water containing 0.1% (v/v) formic acid and 5 mM ammonium formate-acetonitrile. In both method, major components were detected at 2.13-11.63 mg/g (HPLC-DAD) and 0.12-19.20 mg/g (LC-MS/MS). These methods were validated with respect to linearity (coefficient of determination >0.99), recovery (95.22-118.81%), accuracy (90.52-116.96), and precision (<4.0%), and were successfully applied for the quantitative analysis of P. pubescens leaves.

Engineered Full-Length Fibronectin-Hyaluronic Acid Hydrogels for Stem Cell Engineering.

Mechanical cues induce a variety of downstream effects on cells, including the regulation of stem cell behavior. Cell fate is typically characterized on biomaterial substrates where mechanical and chemical properties can be precisely tuned; however, most of these substrates do not recapitulate the biological complexity of the extracellular matrix (ECM). Here, hydrogels are engineered for mechanobiological studies using two major components of the ECM: hyaluronic acid (HA) and fibronectin (FN). Rather than typical surface chemisorption of FN to substrates, the system contains full-length FN covalently crosslinked to HA throughout the hydrogel. The control over the mechanical properties of the hydrogel independent of the concentration of FN and the ability to culture viable cells either on top or encapsulated within the hydrogels are shown. Interestingly, human mesenchymal stem cells (MSCs) experience an increase in nuclear translocation of the yes-associated protein (YAP) to the nucleus when cultured on (2D) substrates with increasing amounts of FN while maintaining constant hydrogel stiffness. However, this FN dependence on nuclear YAP translocation is not observed for MSCs encapsulated in (3D) hydrogels. This work develops complex hydrogels that recapitulate features of the ECM for the control of stem cells in both 2D and 3D environments.

Nuclear softening expedites interstitial cell migration in fibrous networks and dense connective tissues.

Dense matrices impede interstitial cell migration and subsequent repair. We hypothesized that nuclear stiffness is a limiting factor in migration and posited that repair could be expedited by transiently decreasing nuclear stiffness. To test this, we interrogated the interstitial migratory capacity of adult meniscal cells through dense fibrous networks and adult tissue before and after nuclear softening via the application of a histone deacetylase inhibitor, Trichostatin A (TSA) or knockdown of the filamentous nuclear protein Lamin A/C. Our results show that transient softening of the nucleus improves migration through microporous membranes, electrospun fibrous matrices, and tissue sections and that nuclear properties and cell function recover after treatment. We also showed that biomaterial delivery of TSA promoted in vivo cellularization of scaffolds by endogenous cells. By addressing the inherent limitations to repair imposed by nuclear stiffness, this work defines a new strategy to promote the repair of damaged dense connective tissues.

Influence of Fiber Stiffness on Meniscal Cell Migration into Dense Fibrous Networks.

Fibrous scaffolds fabricated via electrospinning are being explored to repair injuries within dense connective tissues. However, there is still much to be understood regarding the appropriate scaffold properties that best support tissue repair. In this study, the influence of the stiffness of electrospun fibers on cell invasion into fibrous scaffolds is investigated. Specifically, soft and stiff electrospun fibrous networks are fabricated from crosslinked methacrylated hyaluronic acid (MeHA), where the stiffness is altered via the extent of MeHA crosslinking. Meniscal fibrochondrocyte (MFC) adhesion and migration into fibrous networks are investigated, where the softer MeHA fibrous networks are easily deformed and densified through cellular tractions and the stiffer MeHA fibrous networks support ≈50% greater MFC invasion over weeks when placed adjacent to meniscal tissue. When the scaffolds are sandwiched between meniscal tissues and implanted subcutaneously, the stiffer MeHA fibrous networks again support enhanced cellular invasion and greater collagen deposition after 4 weeks when compared to the softer MeHA fibrous networks. These results indicate that the mechanics and deformability of fibrous networks likely alter cellular interactions and invasion, providing an important design parameter toward the engineering of scaffolds for tissue repair.

Injectable and Conductive Granular Hydrogels for 3D Printing and Electroactive Tissue Support.

Conductive hydrogels are attractive to mimic electrophysiological environments of biological tissues and toward therapeutic applications. Injectable and conductive hydrogels are of particular interest for applications in 3D printing or for direct injection into tissues; however, current approaches to add conductivity to hydrogels are insufficient, leading to poor gelation, brittle properties, or insufficient conductivity. Here, an approach is developed using the jamming of microgels to form injectable granular hydrogels, where i) hydrogel microparticles (i.e., microgels) are formed with water-in-oil emulsions on microfluidics, ii) microgels are modified via an in situ metal reduction process, and iii) the microgels are jammed into a solid, permitting easy extrusion from a syringe. Due to the presence of metal nanoparticles at the jammed interface with high surface area in this unique design, the granular hydrogels have greater conductivity than non-particle (i.e., bulk) hydrogels treated similarly or granular hydrogels either without metal nanoparticles or containing encapsulated nanoparticles. The conductivity of the granular hydrogels is easily modified through mixing conductive and non-conductive microgels during fabrication and they can be applied to the 3D printing of lattices and to bridge muscle defects. The versatility of this conductive granular hydrogel will permit numerous applications where conductive materials are needed.

Jammed Microgel Inks for 3D Printing Applications.

3D printing involves the development of inks that exhibit the requisite properties for both printing and the intended application. In bioprinting, these inks are often hydrogels with controlled rheological properties that can be stabilized after deposition. Here, an alternate approach is developed where the ink is composed exclusively of jammed microgels, which are designed to incorporate a range of properties through microgel design (e.g., composition, size) and through the mixing of microgels. The jammed microgel inks are shear-thinning to permit flow and rapidly recover upon deposition, including on surfaces or when deposited in 3D within hydrogel supports, and can be further stabilized with secondary cross-linking. This platform allows the use of microgels engineered from various materials (e.g., thiol-ene cross-linked hyaluronic acid (HA), photo-cross-linked poly(ethylene glycol), thermo-sensitive agarose) and that incorporate cells, where the jamming process and printing do not decrease cell viability. The versatility of this particle-based approach opens up numerous potential biomedical applications through the printing of a more diverse set of inks.