Developing biomedical engineering technologies for reproductive medicine

Sequential activation of osteogenic microenvironment via composite peptide-modified microfluidic microspheres for promoting bone regeneration

The osteogenic microenvironment (OME) significantly influences bone repair; however, reproducing its dynamic activation and repair processes remains challenging. In this study, we designed injectable porous microspheres modified with composite peptides to investigate cascade alterations in OME and their underlying mechanisms. Poly l-lactic acid microfluidic microspheres underwent surface modifications through alkaline hydrolysis treatment, involving heterogeneous grafting of bovine serum albumin nanoparticles with stem cell-homing peptides (BNP@SKP) and BMP-2 mimicking peptides (P24), respectively. These modifications well-organized the actions of initial release and subsequent in situ grafting of peptides. Cellular experiments demonstrated varied degrees of chemotactic recruitment and osteogenic differentiation in mesenchymal stem cells. Further biological analysis revealed that BNP@SKP targeted the Ras/Erk axis and upregulated matrix metalloproteinase (MMP)2 and MMP9 expression, thereby enhancing initial chemotaxis and recruitment. In vivo studies validated the establishment of a dynamically regulated OME centered on the microspheres, resulting in increased stem cell recruitment, sequential activation of the differentiation microenvironment, and facilitation of in situ osteogenesis without ectopic ossification. In conclusion, this study successfully fabricated composite peptide-modified microspheres and systematically explored the mechanisms of bone formation through sequential activation of OME via heterogeneous grafting of signaling molecules. This provides theoretical evidence for biomaterials based on microenvironment regulation.

Tβ4-Engineered ADSC Extracellular Vesicles Rescue Cell Senescence Through Separable Microneedle Patches for Diabetic Wound Healing

Microneedles loaded with bioactive substances have demonstrated efficacy in wound healing, while their application in the elderly chronic wounds, aggravated by cellular senescence, is still a significant challenge. Here, a novel therapeutic strategy is presented utilizing Thymosin β4 (Tβ4)-modified adipose-derived stem cell extracellular vesicles (ADSC-EVs) delivered via separable microneedle patches (MN@EVsTβ4). The therapeutic EVsTβ4 are derived from ADSCs that overexpress Tβ4, a factor that reverses cellular senescence. Leveraging the drug-loading and release properties of gelatin methacryloyl and poly(ethylene glycol) diacrylate, EVsTβ4 are encapsulated within the tips of the microneedles. Notably, the soluble hyaluronic acid base layer dissolves rapidly and separates from the tips upon exudate absorption, enabling a sustained release of EVsTβ4. Subsequently, it is demonstrated its ability to mitigate senescence and improve function via the PTEN/PI3K/AKT pathway. Furthermore, MN@EVsTβ4 patches showed significant efficacy in reversing senescence and promoting wound healing in diabetic wound models. Thus, the engineered ADSC-EVs, combined with separable microneedle patches, represent a promising bioengineering strategy for clinical wound management.

A Novel 3D Bioprinting Crosslinking Method Based on Solenoid Valve Control

The crosslinking method of bioinks is essential for scaffold formation in 3D bioprinting. Currently, the crosslinking process of bioinks presents challenges in control, resulting in diminished stability and reliability of the gel and the presence of residual crosslinking agents that may adversely affect cell viability within the gel. This study utilizes sodium alginate as the printing ink and calcium chloride as the crosslinking agent, employing a dual-mode 3D bioprinter for alternating printing. A crosslinking agent is injected through a solenoid valve after using an extrusion-based printing method to create multilayer cell scaffolds. By controlling the printing intervals and opening times of the valve, precise localized crosslinking is achieved, and multiple alternating prints can be performed according to the required thickness of the scaffold. The results indicate that this solenoid valve crosslinking technology significantly enhances the stability and biological properties of the scaffolds, including excellent hydrophilicity, decreased swelling rate, slow degradation rate, and improved mechanical properties. Additionally, due to the reduced residual crosslinking agent, the cell proliferation rate has significantly increased. This technology advances 3D bioprinting toward a more mature stage and provides significant implications for the development of dual-mode printing.

Biomaterial-based drug delivery systems in the treatment of inner ear disorders

Inner ear disorders are among the predominant etiology of hearing loss. The blood-labyrinth barrier limits the ability of drugs to attain pharmacologically effective concentrations within the inner ear; consequently, delivering drugs systemically is insufficient for effectively treating inner ear disorders. Hence, it is imperative to create efficient, minimal or non-invasive methods for administering drugs to the inner ear. However, the development of such a system is hindered by three main factors: anatomical unavailability, the lack of sustained drug delivery, and individual variability. Advances in biomaterials technology have created new opportunities for overcoming existing barriers, offering great hope for the effective treatment of inner ear disorders. Hydrogel- and nanoparticle-based drug delivery systems can carry drugs to targeted designated anatomical locations in the inner ear for long-term, sustained release. Furthermore, a range of devices, including microneedles, micropumps, and cochlear implants, when paired with biomaterials, enhance the delivery of drugs to the inner ear, making the treatment of inner ear disorders more effective. Therefore, biomaterial-based drug delivery systems offer the possibility for extensive clinical uses and promise to restore hearing to millions of patients with inner ear disorders.

Injectable mineralized hydrogel microspheres for accelerated osteocyte network reconstruction and intelligent bone regeneration

The disruption and limited reconstruction capacity of the osteocyte network are pivotal factors underlying impaired bone regeneration. This study developed an injectable mineralized hydrogel microsphere that provides a mineral-rich environment and optimal matrix stiffness for osteocyte network restoration. Furthermore, it spatially activates Notch signaling through osteocyte-derived vesicles with high Jagged1 expression, promoting osteocyte differentiation and enhancing angiogenic regulatory function. Specifically, hydrogel microspheres combining gelatin methacrylate (GelMA), alginate methacrylate (AlgMA), and osteocyte membrane vesicles (OMVs) were fabricated via gas-shear microfluidics and photopolymerization, followed by in situ pre-mineralization to produce mineralized microspheres. Findings indicate that mineralized hydrogel microspheres exhibit significantly increased compressive modulus and in situ formation of amorphous calcium phosphate particles within the gel matrix. In vitro, the mineralized microspheres effectively facilitated osteogenic differentiation in bone marrow-derived mesenchymal stem cells (BMSCs), with adherent cells displaying accelerated osteocyte marker expression. Co-culture experiments further revealed enhanced vascular formation potential. Ectopic bone regeneration studies demonstrated that mineralized hydrogel microspheres promote rapid formation of mature osteocyte networks in vivo. Moreover, in a femoral critical bone defect model, these microspheres accelerated defect healing. Collectively, mineralized hydrogel microspheres expedite osteocyte network reconstruction, supporting intelligent bone regeneration, and present a promising approach for critical-sized bone defect repair.

Magnetic structural color microspheres for the multiplex detection of acute kidney injury biomarkers

BACKGROUND

Acute kidney injury (AKI) is a frequent acute condition that features sharp loss of kidney functions and often leads to severe situations such as end-stage renal disease and even death. The incidence and mortality of AKI in hospitalized patients are high worldwide, and one of the reasons for this poor prognosis is the inability to diagnose AKI promptly. The sensitive and specific assay of biomarkers is considered a promising method for early diagnosis of AKI.

RESULTS

We designed a magnetic-responsive structural colored inverse opal hydrogel microspheres (IOHMs) for the multiplex detection of cystatin C (CysC) and neutrophil gelatinase-associated lipocalin (NGAL), which are two early biomarkers of AKI. The microsphere possessed structural colors for encoding and directional motion ability for improved detection sensitivity and separation efficiency, showing the detection ranges of CysC and NGAL in 10-5000 ng/mL and 10-1000 ng/mL, respectively.

SIGNIFICANCE

The method's accuracy and reliability were consistent with commonly used enzyme-linked immunosorbent assay methods. Therefore, these magnetic IOHMs have a promising application for early AKI diagnosis.

Therapeutic strategies: Bioactive hydrogels oxidized sodium alginate/strontium/betamethasone for preventing intrauterine adhesion

Intrauterine adhesion (IUA) is an endometrial damage repair disorder that leads to menstrual loss, amenorrhea, and infertility in women; therefore, addressing this dilemma is a critical challenge. In this study, a multifunctional hydrogel, comprising oxidized sodium alginate (OSA), strontium carbonate (SrCO3), and betamethasone 21-phosphate sodium (BSP), was formulated to facilitate angiogenesis, reduce fibrosis, and support tissue repair in the treatment of IUA. The composite hydrogels showed significant bioactivity on human endometrial stromal cells (HESCs) and human umbilical vein endothelial cells (HUVECs), promoting the injured HESCs repair, reversing the degree of fibrosis to a certain extent, and enhancing the proliferation and migration of HUVECs. These results were also verified in the IUA model of sexually mature female rats. Compared with the model group, the selection of the appropriate hydrogel significantly increased endometrial thickness (p < 0.01), the number of glands (p < 0.001), decreased the degree of fibrosis (p < 0.05), and Vimentin (p < 0.01), CK19 (p < 0.01), CD31 (p < 0.01), and Ki67 (p < 0.01) molecular expression increased remarkably. In summary, in situ injection of this multifunctional hydrogel into the uterine cavity not only serves as a physical barrier, isolating the damaged endometrium, but also gradually releases drugs as the hydrogel degrades. This multifunctional hydrogel promotes endometrial proliferation and angiogenesis while reducing fibrosis, and provides therapeutic strategies for patients with clinical IUA.

Mechanically regulated microcarriers with stem cell loading for skin photoaging therapy

Long-term exposure to ultraviolet radiation compromises skin structural integrity and results in disruption of normal physiological functions. Stem cells have gained attention in anti-photoaging, while controlling the tissue mechanical microenvironment of cell delivery sites is crucial for regulating cell fate and achieving optimal therapeutic performances. Here, we introduce a mechanically regulated human recombinant collagen (RHC) microcarrier generated through microfluidics, which is capable of modulating stem cell differentiation to treat photoaged skin. By controlling the cross-linking parameters, the mechanical properties of microcarriers could precisely tuned to optimize the stem cell differentiation. The microcarriers are surface functionalized with fibronectin (Fn)-platelet derived growth factor-BB (PDGF-BB) to facilitate adipose derived mesenchymal stem cells (Ad-MSCs) loading. In in vivo experiments, subcutaneous injection of stem cell loaded RHC microcarriers significantly reduced skin wrinkles after ultraviolet-injury, effectively promoted collagen synthesis, and increased vascular density. These encouraging results indicate that the present mechanically regulated microcarriers have great potential to deliver stem cells and regulate their differentiation for anti-photoaging treatments.

The causal relationship of inflammation-related factors with osteoporosis: A Mendelian Randomization Analysis

BACKGROUND

We used Mendelian randomization (MR) approach to examine whether genetically determined inflammation-related risk factors play a role in the onset of osteoporosis (OP) in the European population.

METHODS

Genome-wide association studies (GWASs) summary statistics of estimated bone mineral density (eBMD) obtained from the public database GEnetic Factors for OSteoporosis Consortium (GEFOS) including 142,487 European people. For exposures, we utilized GWAS data of 9 risk factors including diseases chronic kidney disease (CKD) (41,395 cases and 439,303 controls), type 2 diabetes (T2D) (88,427 cases and 566,778 controls), Alzheimer's disease (AD) (71,880 cases, 383,378 controls) and major depression disorder (MDD) (9240 cases and 9519 controls) and lifestyle behaviors are from different consortiums. Inverse variance weighted (IVW) analysis was principal method in this study and random effect model was applied; MR-Egger method and weighted median method were also performed for reliable results. Cochran's Q test and MR-Egger regression were used to detect heterogeneity and pleiotropy and leave-one-out analysis was performed to find out whether there are influential SNPs.

RESULTS

We found that T2D (IVW: β = 0.05, P = 0.0014), FI (IVW: β = -0.22, P < 0.001), CKD (IVW: β = 0.02, P = 0.009), ALZ (IVW: β = 0.06, P = 0.005), Coffee consumption (IVW: β = 0.11, P = 0.003) were causally associated with OP (P<0.006after Bonferroni correction).

CONCLUSIONS

Our study revealed that T2D, FI, CKD, ALZ and coffee consumption are causally associated with OP. Future interventions targeting factors above could provide new clinical strategies for the personalized prevention and treatment of osteoporosis.

Dual physiological responsive structural color hydrogel particles for wound repair

Hydrogel-based patches have demonstrated their values in diabetic wounds repair, particularly those intelligent dressings with continuous repair promoting and monitoring capabilities. Here, we propose a type of dual physiological responsive structural color particles for wound repair. The particles are composed of a hyaluronic acid methacryloyl (HAMA)-sodium alginate (Alg) inverse opal scaffold, filled with oxidized dextran (ODex)/quaternized chitosan (QCS) hydrogel. The photo-polymerized HAMA and ionically cross-linked Ca-Alg constitute to the dual-network hydrogel with stable structural color. Furthermore, the ODex/QCS hydrogel, combined with glucose oxidase (GOX), exhibits pH/glucose dual responsiveness. Moreover, antimmicrobial peptide (AMP) plus vascular endothelial growth factor (VEGF) are comprised within the GOX-doped ODex/QCS hydrogel. In the high-glucose wound environment, GOX catalyzes glucose to generate acidic products, triggering rapid release of AMP and VEGF. Importantly, this process also leads to structural color changes of the particles, offering significant potential for wound monitoring. It has been demonstrated that such particles greatly promote the healing progress of diabetic wound in vivo. These results indicate that the present dual responsive particles would find valuable applications in diabetic wounds repair and the associated areas.

Microfluidic Synthesis of Magnetic Nanoparticles for Biomedical Applications

Magnetic nanoparticles have attracted great attention and become promising candidates in the biomedicine field due to their special physicochemical properties. They are generally divided into metallic and non-metallic magnetic nanoparticles, according to their compositions. Both of the two types have shown practical values in biomedicine applications, such as drug delivery, biosensing, bioimaging, and so on. Research efforts are devoted to the improvement of synthesis strategies to achieve magnetic nanoparticles with controllable morphology, diverse composition, active surface, or multiple functions. Taking high repeatability, programmable operation, precise fluid control, and simple device into account, the microfluidics system can expand the production scale and develop magnetic nanoparticles with desired features. This review will first describe different classifications of promising magnetic nanoparticles, followed by the advancements in microfluidic synthesis and the latest biomedical applications of these magnetic nanoparticles. In addition, the challenges and prospects of magnetic nanoparticles in the biomedical field are also discussed.

Recombinant human collagen hydrogels with different stem cell-derived exosomes encapsulation for wound treatment

Exosomes-loaded hydrogels have potential value in wound treatment. Current studies focus on improving hydrogels' biocompatibility and optimizing different stem cell-derived exosomes for better therapeutic effect. Herein, we present a novel biocompatible recombinant human collagen (RHC) hydrogel loading with different MSCs-derived exosomes for promoting wound healing. We modify the RHC with methacrylate anhydride (MA) at optimal concentration, generating collagen hydrogel (RHCMA) with ideal physiochemical properties for exosome delivery (MSC-exos@RHCMA). Exosomes derived from human adipose-derived MSCs (ADSC-exos), bone marrow-derived MSCs (BMSC-exos) and umbilical cord MSCs (ucMSC-exos) are harvested from the culture supernatants and are loaded into RHCMA, respectively. These three hydrogel systems exhibit desired sustained release features, and can significantly improve cell proliferation and migration. In addition, these MSC-exos@RHCMAs show excellent therapeutic performance in treating the wounds of rats. Notably, we have demonstrated that the healing effect occurs best under the treatment of ucMSC-exos@RHCMA, following inflammatory resolution, angiogenesis, and collagen formation. These results would supply important value for the clinical application of MSC-exos in wound treatment in the future.

Dynamic Tumor Immunology-on-a-Chip for Peripheral Blood-Derived Tumor-Reactive T Cell Expansion

Adoptive T cell therapy has shown great promise in the treatment of solid tumors, which, however, poses a great challenge to obtain autologous tumor-reactive T cells in a cost-effective manner. Here, we present a dynamic tumor immunology-on-a-chip, mimicking immune responses, for achieving the enrichment and expansion of tumor-reactive T cells. Tumor spheroids with uniform size can be generated by seeding tumor cells in hydrogel-embedded micropillar arrays, and could be trapped upon removal of hydrogel. Then, T cells were infused and fully contacted with these tumor spheroids under biomimetic flow conditions provided by herringbone-patterned microgrooves arrays. We found that the tamed tumor-reactive T cells could be fully activated and a rapid clonal proliferation was realized during the cultivation. In addition, these tumor-reactive T cells exhibited a specific and powerful tumor-killing capability in vitro. Thus, the suggested dynamic microfluidic chips with staged structure-transformable properties realize both the producible formation of tumor spheroids and the recapitulation of tumor-immune crosstalk to expand tumor-reactive T cells. These features indicate that the dynamic and reproducible tumor immunology-on-a-chip has potential in the preparation of therapeutic T cell products for clinical cancer immunotherapy.

3D printing in musculoskeletal interface engineering: Current progress and future directions

The musculoskeletal system relies on critical tissue interfaces for its function; however, these interfaces are often compromised by injuries and diseases. Restoration of these interfaces is complex by nature which renders traditional treatments inadequate. An emerging solution is three-dimensional printing, which allows for precise fabrication of biomimetic scaffolds to enhance tissue regeneration. This review summarizes the utility of 3D printing in creating scaffolds for musculoskeletal interfaces, mainly focusing on advanced techniques such as multi-material printing, bioprinting, and 4D printing. We emphasize the significance of mimicking natural tissue gradients and the selection of appropriate biomaterials to ensure scaffold success. The review outlines state-of-the-art 3D printing technologies, varying from extrusion, inkjet and laser-assisted bioprinting, which are crucial for producing scaffolds with tailored mechanical and biological properties. Applications in cartilage-bone, intervertebral disc, tendon/ligament-bone, and muscle-tendon junction engineering are discussed, highlighting the potential for improved integration and functionality. Furthermore, we address challenges in material development, printing resolution, and the in vivo performance of scaffolds, as well as the prospects for clinical translation. The review concludes by underscoring the transformative potential of 3D printing to advance orthopedic medicine, offering a roadmap for future research at the intersection of biomaterials, drug delivery, and tissue engineering.

Developing 3D bioprinting for organs-on-chips

Organs-on-chips (OoCs) have significantly advanced biomedical research by precisely reconstructing human microphysiological systems with biomimetic functions. However, achieving greater structural complexity of cell cultures on-chip for enhanced biological mimicry remains a challenge. To overcome these challenges, 3D bioprinting techniques can be used in directly building complex 3D cultures on chips, facilitating the in vitro engineering of organ-level models. Herein, we review the distinctive features of OoCs, along with the technical and biological challenges associated with replicating complex organ structures. We discuss recent bioprinting innovations that simplify the fabrication of OoCs while increasing their architectural complexity, leading to breakthroughs in the field and enabling the investigation of previously inaccessible biological problems. We highlight the challenges for the development of 3D bioprinted OoCs, concluding with a perspective on future directions aimed at facilitating their clinical translation.

Colon-Targeted Hydrogel Microsphere System Encapsulating Oleic Acid-Emodin for Crohn's Disease Treatment via Ferroptosis Inhibition

Crohn's disease (CD) is a relapsing, systemic inflammatory disease that primarily affects the gastrointestinal tract and is often accompanied by extraintestinal manifestations and associated immune disorders. However, current pharmacological treatments for CD encounter several challenges, such as a lack of precise drug targeting and inadequate retention of drugs in the inflamed colon, along with low bioavailability. Herein, we utilized oleic acid (OA) as a solvent to enhance the bioavailability and solubility of emodin. Simultaneously, we encapsulated OA-emodin (OAE) into hydrogel microspheres (HMs) composed of hyaluronic acid (HA) and calcium alginate (CA) to develop a colon-targeted drug delivery system (HM@OAE) for CD therapy. The pH responsiveness of CA enabled HM@OAE to bypass the stomach and specifically target the colon, where it released OAE following oral administration. In addition, in vitro studies demonstrated that HM@OAE significantly reduced the secretion of proinflammatory cytokines, decreased reactive oxygen species levels, and restrained ferroptosis by upregulating GPX4 and SLC7A11 expression while downregulating ACSL4 expression. Furthermore, to confirm these findings in a live organism, an in vivo study was conducted using a dextran sulfate sodium-induced colitis mouse model. This study validated the therapeutic efficacy of HM@OAE, significantly alleviating colonic inflammation and restoring intestinal epithelial integrity. These results suggest that HM@OAE is a promising clinical candidate for CD treatment.

Multiresponsive Microcapsules for Prevention of Intrauterine Adhesion

Intrauterine adhesion (IUA) has a significant negative impact on women's reproductive health. One of the development trends of biomaterials for prevention of IUA is improving the stability and multifaceted functions. Here, we propose a multiresponsive microcapsule (A/G-Fe3O4-Se) with an alginate (ALG) and gelatin methacryloyl (GelMA) dual-network hydrogel shell loaded with magnetic nanoparticles (Fe3O4-Se) and an ultrasound-responsive decafluoropentane core for the prevention of IUA using a microfluidic technique. The microcapsules inherited the biofriendly advantages of ALG and GelMA. The encapsulated magneto-responsive Fe3O4-Se made the microcapsule flexibly change the distribution to adapt to the irregular shape of the uterus and better exert the therapeutic effect. Besides, the A/G-Fe3O4-Se microcapsules demonstrated antioxidant, antibacterial, and pro-healing properties in vitro. Moreover, in the IUA rat models, we also observed a reduction in oxidative stress, better endometrial regeneration, and improved endometrial receptivity and pregnancy rates after treatment of the microcapsules. Consequently, the A/G-Fe3O4-Se microcapsules can be used as a promising strategy for the treatment of damaged endometrium as well as prevention of IUA.

Recent development of micro-nano carriers for oral antineoplastic drug delivery

Chemotherapy is widely recognized as a highly efficacious modality for cancer treatment, involving the administration of chemotherapeutic agents to target and eradicate tumor cells. Currently, oral administration stands as the prevailing and widely utilized method of delivering chemotherapy drugs. However, the majority of anti-tumor medications exhibit limited solubility and permeability, and poor stability in harsh gastrointestinal environments, thereby impeding their therapeutic efficacy for chemotherapy. Therefore, more and more micro-nano drug delivery carriers have been developed and used to effectively deliver anti-cancer drugs, which can overcome physiological barriers, facilitate oral administration, and ultimately improve drug efficacy. In this paper, we first discuss the effects of various biological barriers on micro-nano drug carriers and oral administration approach. Then, the development of micro-nano drug carriers based on various biomedical components, such as micelles, dendrimers, hydrogels, liposomes, inorganic nanoparticles, etc. were introduced. Finally, the current dilemma and the potential of oral drug delivery for clinical treatment were discussed. The primary objective of this review is to introduce various oral delivery methods and serve as a point of reference for the advancement of novel oral delivery carriers, with the ultimate goal of informing the development of future clinical applications.

Directed Cell Growth of C2C12 Cells on ECM Free Bioprinted Nano/Micro Scaffolds

Skeletal muscle cell growth impairment can result in severe health issues, such as reduced mobility, metabolic problems, and cardiovascular issues, which can significantly impact an individual's overall health and lifestyle. To address this issue, it is essential to adopt a multi-faceted approach. Conventional 2D cell culture methods fail to replicate the critical features of in vivo micro/nanoarchitecture, which is crucial for the growth of skeletal muscle cells. In this study, the directed growth of mouse skeletal myoblasts (C2C12) cells on ECM-free biocompatible scaffolds is demonstrated and fabricated using two-photon lithography (TPL). These scaffolds are 2D and 3D and have nano/micro-features derived from chitosan-based carbon quantum dots (Ch-CQDs). Ch-CQDs act as two-photon initiators for TPL and also provide the scaffolds with adequate mechanical strength and specific binding sites. These scaffolds are biocompatible and can support cellular adhesion and growth without the need for ECM coating. The nano/micro scaffolds mimic the in vivo cellular microenvironment, enabling directed cell growth on ECM-free surfaces. The fabricated scaffolds have tunable mechanical strength ranging from 0.09 to 0.75 GPa. By using Ch-CQDs, scaffolds are created that promote cell growth and alignment, which is crucial for skeletal muscle cell growth.

Functionalized 3D-printed GelMA/Laponite hydrogel scaffold promotes BMSCs recruitment through osteoimmunomodulatory enhance osteogenic via AMPK/mTOR signaling pathway

The migration and differentiation of bone marrow mesenchymal stem cells (BMSCs) play crucial roles in bone repair processes. However, conventional scaffolds often lack of effectively inducing and recruiting BMSCs. In our study, we present a novel approach by introducing a 3D-bioprinted scaffold composed of hydrogels, with the addition of laponite to the GelMA solution, aimed at enhancing scaffold performance. Both in vivo and in vitro experiments have confirmed the outstanding biocompatibility of the scaffold. Furthermore, for the first time, Apt19s has been chemically modified onto the surface of the hydrogel scaffold, resulting in a remarkable enhancement in the migration and adhesion of BMSCs. Moreover, the scaffold has demonstrated robust osteogenic differentiation capability in both in vivo and in vitro environments. Additionally, the hydrogel scaffold has shown the ability to induce the polarization of macrophages from M1 to M2, thereby facilitating the osteogenic differentiation of BMSCs via the bone immune pathway. Through RNA-seq analysis, it has been revealed that macrophages regulate the osteogenic differentiation of BMSCs through the AMPK/mTOR signaling pathway. In summary, the functionalized GelMA/Laponite scaffold offers a cost-effective approach for tailored in situ bone regeneration.

Emerging biomedical technologies for scarless wound healing

Complete wound healing without scar formation has attracted increasing attention, prompting the development of various strategies to address this challenge. In clinical settings, there is a growing preference for emerging biomedical technologies that effectively manage fibrosis following skin injury, as they provide high efficacy, cost-effectiveness, and minimal side effects compared to invasive and costly surgical techniques. This review gives an overview of the latest developments in advanced biomedical technologies for scarless wound management. We first introduce the wound healing process and key mechanisms involved in scar formation. Subsequently, we explore common strategies for wound treatment, including their fabrication methods, superior performance and the latest research developments in this field. We then shift our focus to emerging biomedical technologies for scarless wound healing, detailing the mechanism of action, unique properties, and advanced practical applications of various biomedical technology-based therapies, such as cell therapy, drug therapy, biomaterial therapy, and synergistic therapy. Finally, we critically assess the shortcomings and potential applications of these biomedical technologies and therapeutic methods in the realm of scar treatment.

Functional Mechanism and Clinical Implications of lncRNA LINC-PINT in Delayed Fracture Healing

BACKGROUND

Fracture healing can be impeded or even compromised by various factors, resulting in a growing number of patients suffering. The lncRNA LINC-PINT has garnered attention for its latent role in enhancing fracture healing, but its specific functions in this process remain unclear.

OBJECTIVES

The primary objective of this study is to investigate the clinical relevance and underlying molecular mechanisms of LINC-PINT in delayed fracture healing (DFH), while also assessing its potential as an early diagnostic biomarker.

MATERIALS AND METHODS

The expression levels of LINC-PINT were measured in the serum of DFH patients and those with normal fracture healing using RT-qPCR. In MC3T3-E1 cells, the study investigated the influence on the expression of differentiation-related protein, cell viability, and apoptosis through the modulation of LINC-PINT and miR-324-3p. To elucidate the targeting relationship between LINC-PINT, miR-324-3p, and BMP2, a dual-luciferase reporter assay was employed.

RESULTS

The findings revealed a significant downregulation of LINC-PINT expression in DFH patients. LINC-PINT showed high sensitivity and specificity as a diagnostic marker for DFH. In MC3T3-E1 cells, LINC-PINT overexpression markedly enhanced the expression levels of ALP, OCN, Runx2, and OPN, improved cell viability, and inhibited apoptosis. LINC-PINT negatively regulated miR-324-3p, and the effects of LINC-PINT were counteracted by miR-324-3p. LINC-PINT was found to regulate BMP2 by targeting miR-324-3p.

CONCLUSION

LINC-PINT could serve as an early diagnostic biomarker for DFH and slow the progression of DFH by modulating BMP2 through the targeted regulation of miR-324-3p. This research presents new molecular targets for the diagnosis and treatment of DFH.

Bioactive additives from the dorsal dermis of mice for enhanced vascularization in 3D bioprinting

Effective angiogenesis is essential for creating complex vascular networks in tissue engineering; however, there is a scarcity of safe and potent pro-angiogenic factors. Although a decellularized extracellular matrix (dECM) offers excellent biocompatibility and is widely used in tissue engineering as a pro-angiogenic additive, its conventional extraction technique resulting in significant loss of bioactivity limits clinical potential. The dorsal dermal tissue has rich blood perfusion and its dECM is rich in angiogenic factors. In this study, the dECM components from the dorsal dermis of mice (DD) were produced to enhance in vitro and in vivo pro-angiogenic abilities using a novel physical method. Morphological studies showed no significant difference between DD-wild-type (DD-wt) and DD-wild-type-newborn (DD-wtn), and there was also no difference in DNA or RNA concentration. In addition, DD-wtn outperformed DD-wt in maintaining the stemness of MSCs, promoting inflammatory response and facilitating endothelial cell differentiation. It is of greater significance to note that the dermal combined fibrous capsule thickness is greater in the DD-wt treated group than in the DD-wtn group. Furthermore, the number of blood vessels in the subcutaneously implanted scaffold with DD-wtn increased by 233%. Consequently, our current finding provides a promising strategy to produce a novel pro-angiogenic bioink additive for enhancing vascularization in 3D bioprinting.

Application of kartogenin for the treatment of cartilage defects: current practice and future directions

Osteoarthritis and sports injuries often lead to cartilage defects. How to promote its repair and rebuild the smooth cartilage surface has been a hot spot of research in recent years. Kartogenin (KGN), a small molecule discovered in recent years, has been shown to promote the proliferation and chondrogenic differentiation of mesenchymal stem cells (MSCs). As more and more studies have been conducted on KGN, its mechanism of action has been gradually revealed. However, KGN is insoluble in water and therefore easily removed by body fluids. In order to address such issues, a number of systems for efficient intra-articular delivery of KGN have been developed. In addition, due to the complex pathology of cartilage repair, KGN is often used in combination with other drugs to target different stages. In addition, with the rapid development of tissue engineering, scholars have combined KGN with various scaffolds by physical or chemical methods. In this paper, we firstly introduce the general properties of KGN followed by a review of the latest advances in the intra-articular delivery modes of KGN. Finally, we discuss the prospects for the application of KGN in cartilage regeneration, which is aimed at providing a new idea and target for the treatment of cartilage defects.

Polydopamine-coated polycaprolactone/carbon nanotube fibrous scaffolds loaded with basic fibroblast growth factor for wound healing

Image 1.

Medical Applications and Cellular Mechanisms of Action of Carboxymethyl Chitosan Hydrogels

Carboxymethyl chitosan (CMCS) hydrogels have been investigated in biomedical research because of their versatile properties that make them suitable for various medical applications. Key properties that are especially valuable for biomedical use include biocompatibility, tailored solid-like mechanical characteristics, biodegradability, antibacterial activity, moisture retention, and pH stimuli-sensitive swelling. These features offer advantages such as enhanced healing, promotion of granulation tissue formation, and facilitation of neutrophil migration. As a result, CMCS hydrogels are favorable materials for applications in biopharmaceuticals, drug delivery systems, wound healing, tissue engineering, and more. Understanding the interactions between CMCS hydrogels and biological systems, with a focus on their influence on cellular behavior, is crucial for leveraging their versatility. Because of the constantly growing interest in chitosan and its derivative hydrogels in biomedical research and applications, the present review aims to provide updated insights into the potential medical applications of CMCS based on recent findings. Additionally, we comprehensively elucidated the cellular mechanisms underlying the actions of these hydrogels in medical settings. In summary, this paper recapitulates valuable data gathered from the current literature, offering perspectives for further development and utilization of carboxymethyl hydrogels in various medical contexts.

Structural Color Colloidal Photonic Crystals for Biomedical Applications

Photonic crystals are a new class of optical microstructure materials characterized by a dielectric constant that varies periodically with space and features a photonic bandgap. Inspired by natural photonic crystals such as butterfly scales, a series of artificial photonic crystals are developed for use in integrated photonic platforms, biosensing, communication, and other fields. Among them, colloidal photonic crystals (CPCs) have gained widespread attention due to their excellent optical properties and advantages, such as ease of preparation and functionalization. This work reviews the classification and self-assembly principles of CPCs, details some of the latest biomedical applications of large-area, high-quality CPCs prepared using advanced self-assembly methods, summarizes the existing challenges in CPC construction and application, and anticipates future development directions and optimization strategy. With further advancements, CPCs are expected to play a more critical role in biosensors, drug delivery, cell research, and other fields, bringing significant benefits to biomedical research and clinical practice.

Locationally activated PRP via an injectable dual-network hydrogel for endometrial regeneration

Enhancing the effectiveness of platelet-rich plasma (PRP) for endometrial regeneration is challenging, due to its limited mechanical properties and burst release of growth factors. Here, we proposed an injectable interpenetrating dual-network hydrogel that can locationally activate PRP within the uterine cavity, sustained release growth factors and further address the insufficient therapeutic efficacy. Locational activation of PRP is achieved using the dual-network hydrogel. The phenylboronic acid (PBA) modified methacrylated hyaluronic acid (HAMA) dispersion chelates Ca2+ by carboxy groups and polyphenol groups, and in situ crosslinked with PRP-loaded polyvinyl alcohol (PVA) dispersion by dynamic borate ester bonds thus establishing the soft hydrogel. Subsequently, in situ photo-crosslinking technology is employed to enhance the mechanical performance of hydrogels by initiating free radical polymerization of carbon-carbon double bonds to form a dense network. The PRP-hydrogel significantly promoted the endometrial cell proliferation, exhibited strong pro-angiogenic effects, and down-regulated the expression of collagen deposition genes by inhibiting the TGF-β1-SMAD2/3 pathway in vitro. In vivo experiments using a rat intrauterine adhesion (IUA) model showed that the PRP-hydrogel significantly promoted endometrial regeneration and restored uterine functionality. Furthermore, rats treated with the PRP-hydrogel displayed an increase in the number of embryos, litter size, and birth rate, which was similar to normal rats. Overall, this injectable interpenetrating dual-network hydrogel, capable of locational activation of PRP, suggests a new therapeutic approach for endometrial repair.

3D Printing of Naturally Derived Adhesive Hemostatic Sponge

Hydrogel hemostatic sponges have been recognized for its effectiveness in wound treatment due to its excellent biocompatibility, degradability, as well as multi-facet functionalities. Current research focuses on optimizing the composition and structure of the sponge to enhance its therapeutic effectiveness. Here, we propose an adhesive hydrogel made from purely natural substances extracted from okra and Panax notoginseng. We utilize 3-dimensional (3D) printing technology to fabricate the hemostatic hydrogel scaffold, incorporating gelatin into the hydrogel and refining the mixing ratio. The interaction between gelatin and okra polyphenols contributes to successful injectability as well as stability of the printed scaffold. The okra in the scaffold exhibits favorable adhesion and hemostatic effects, and the total saponins of Panax notoginseng facilitate angiogenesis. Through in vitro experiments, we have substantiated the scaffold's excellent stability, adhesion, biocompatibility, and angiogenesis-promoting ability. Furthermore, in vivo experiments have demonstrated its dual functionality in rapid hemostasis and wound repair. These features suggest that the 3D-printed, natural substance-derived hydrogel scaffolds have valuable potential in wound healing and related applications.

Emerging platelet-based drug delivery systems

Drug delivery systems are becoming increasingly utilized; however, a major challenge in this field is the insufficient target of tissues or cells. Although efforts with engineered nanoparticles have shown some success, issues with targeting, toxicity and immunogenicity persist. Conversely, living cells can be used as drug-delivery vehicles because they typically have innate targeting mechanisms and minimal adverse effects. As active participants in hemostasis, inflammation, and tumors, platelets have shown great potential in drug delivery. This review highlights platelet-based drug delivery systems, including platelet membrane engineering, platelet membrane coating, platelet cytoplasmic drug loading, genetic engineering, and synthetic/artificial platelets for different applications.

Unraveling the Dynamics of Estrogen and Progesterone Signaling in the Endometrium: An Overview

The endometrium is crucial for the perpetuation of human species. It is a complex and dynamic tissue lining the inner wall of the uterus, regulated throughout a woman's life based on estrogen and progesterone fluctuations. During each menstrual cycle, this multicellular tissue undergoes cyclical changes, including regeneration, differentiation in order to allow egg implantation and embryo development, or shedding of the functional layer in the absence of pregnancy. The biology of the endometrium relies on paracrine interactions between epithelial and stromal cells involving complex signaling pathways that are modulated by the variations of estrogen and progesterone levels across the menstrual cycle. Understanding the complexity of estrogen and progesterone receptor signaling will help elucidate the mechanisms underlying normal reproductive physiology and provide fundamental knowledge contributing to a better understanding of the consequences of hormonal imbalances on gynecological conditions and tumorigenesis. In this narrative review, we delve into the physiology of the endometrium, encompassing the complex signaling pathways of estrogen and progesterone.

Enhancement of Local Osseointegration and Implant Stability of Titanium Implant in Osteoporotic Rats by Biomimetic Multilayered Structures Containing Catalpol

This study examined the surface modification of titanium (Ti) implants to enhance early-stage osseointegration, which reduced the failure rate of internal fixation in osteoporotic fractures that inherently decrease in bone mass and strength. We employed a layer-by-layer electroassembly technique to deposit catalpol-containing hyaluronic acid/chitosan multilayers onto the surface of Ti implants. To evaluate the in vitro osteoinductive effects of catalpol-coated Ti implants, the robust osteoblast differentiation capacity of the murine preosteoblast cell line, MC3T3-E1, was employed. Furthermore, the performance of these implants was evaluated in vivo through femoral intramedullary implantation in Sprague-Dawley rats. The engineered implant effectively regulated catalpol release, promoting increased bone formation during the initial stages of implantation. The in vitro findings demonstrated that catalpol-coated Ti surfaces boosted ALP activity, cell proliferation as measured by CCK-8, and osteogenic protein expression via WB analysis, surpassing the uncoated Ti group (P < 0.05). In vivo micro-computed tomography (CT) and histological analyses revealed that catalpol-coated Ti significantly facilitated the formation and remodeling of new bone in osteoporotic rats at 14 days post-implantation. This study outlines a comprehensive and straightforward methodology for the fabrication of biofunctional Ti implants to address osteoporosis.

The STAT3 inhibitor B9 alleviates lipopolysaccharide-induced acute lung injury through its anti-inflammatory effects

The development of acute lung injury (ALI), a common respiratory condition with multiple causes, is significantly influenced by the pro-inflammatory environment of signal transducer and activator of transcription 3 (STAT3) in macrophages. Our study aimed to evaluate the anti-inflammatory effects of B9 (N-(4-hydroxyphenyl)-9, 10-dioxo-9, 10-dihydroanthracene-2-sulfonamide), a novel inhibitor targeting the STAT3 SH2 domain, in macrophages and to assess its therapeutic potential for ALI using a mouse model of lipopolysaccharide (LPS)-induced ALI. We found that B9 (30 mg/kg) significantly reduced lung pathological damage and neutrophil infiltration caused by the intratracheal administration of LPS. Additionally, the high expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in alveolar lavage fluid was also inhibited by B9 treatment. The decreased expression of CD86 and increased CD206 in lung tissue demonstrated the anti-inflammatory effect of B9, which was due to its inhibition of the STAT3 signaling pathway in macrophages of ALI mice. Furthermore, B9 suppressed the activation of RAW264.7 cells induced by LPS, characterized by its ability to inhibit the activation of iNOS and STAT3 in a dose-dependent manner, as well as reduce the secretion of IL-6 and IL-1β. The in vivo preliminary safety evaluation indicated that B9 had a favorable safety profile at the administered doses. These results suggest that B9 exerts a therapeutic effect on LPS-induced ALI, potentially by preventing the phosphorylation of STAT3 Y705 and S727 without affecting the STAT3 protein level. Taken together, these findings provide a foundation for developing B9 as a novel anti-inflammatory agent for ameliorating LPS-induced ALI.

Emerging approaches for the development of artificial islets

The islet of Langerhans, functioning as a "mini organ", plays a vital role in regulating endocrine activities due to its intricate structure. Dysfunction in these islets is closely associated with the development of diabetes mellitus (DM). To offer valuable insights for DM research and treatment, various approaches have been proposed to create artificial islets or islet organoids with high similarity to natural islets, under the collaborative effort of biologists, clinical physicians, and biomedical engineers. This review investigates the design and fabrication of artificial islets considering both biological and tissue engineering aspects. It begins by examining the natural structures and functions of native islets and proceeds to analyze the protocols for generating islets from stem cells. The review also outlines various techniques used in crafting artificial islets, with a specific focus on hydrogel-based ones. Additionally, it provides a concise overview of the materials and devices employed in the clinical applications of artificial islets. Throughout, the primary goal is to develop artificial islets, thereby bridging the realms of developmental biology, clinical medicine, and tissue engineering.

Composite Aerogel Scaffolds Containing Flexible Silica Nanofiber and Tricalcium Phosphate Enable Skin Regeneration

Poor hemostatic ability and less vascularization at the injury site could hinder wound healing as well as adversely affect the quality of life (QOL). An ideal wound dressing should exhibit certain characteristics: (a) good hemostatic ability, (b) rapid wound healing, and (c) skin appendage formation. This necessitates the advent of innovative dressings to facilitate skin regeneration. Therapeutic ions, such as silicon ions (Si4+) and calcium ions (Ca2+), have been shown to assist in wound repair. The Si4+ released from silica (SiO2) can upregulate the expression of proteins, including the vascular endothelial growth factor (VEGF) and alpha smooth muscle actin (α-SMA), which is conducive to vascularization; Ca2+ released from tricalcium phosphate (TCP) can promote the coagulation alongside upregulating the expression of cell migration and cell differentiation related proteins, thereby facilitating the wound repair. The overarching objective of this study was to exploit short SiO2 nanofibers along with the TCP to prepare TCPx@SSF aerogels and assess their wound healing ability. Short SiO2 nanofibers were prepared by electrospinning and blended with varying proportions of TCP to afford TCPx@SSF aerogel scaffolds. The TCPx@SSF aerogels exhibited good cytocompatibility in a subcutaneous implantation model and manifested a rapid hemostatic effect (hemostatic time 75 s) in a liver trauma model in the rabbit. These aerogel scaffolds also promoted skin regeneration and exhibited rapid wound closure, epithelial tissue regeneration, and collagen deposition. Taken together, TCPx@SSF aerogels may be valuable for wound healing.

Bio-inspired progressive motile sperm separation using joint rheotaxis and boundary-following behavior

Infertility, as a daunting ever-increasing challenge, poses a worldwide issue to both couples and the healthcare sector. According to the World Health Organization, half of infertility cases are attributed to male factor infertility, either partly or completely. Semen parameters of concern including sperm count, morphology, and motility are deemed to play a vital role in the insemination process. Density gradient centrifugation, being a clinically established procedure for improving on the mentioned parameters, has long been proven to inflict damage on the DNA content of the sperm cells, inducing DNA fragmentation. Herein, a bio-inspired microfluidic device is proposed that capitalizes on the geometry of the uterotubal junction (UTJ) of the female reproductive tract, which can act as a rheological barrier. The device leverages sperm rheotaxis and boundary-following behavior which have been considered as major migratory mechanisms used by sperm during the fertilization process in the female body. The device consists of a series of parallel channels that guide progressive motile sperms into the main sorting channel, where the hydrodynamic barriers created by two consecutive UTJ-like constrictions select sperms based on their propulsive velocity and linearity of motion. The sequential sorting employed here allows for the fractionation of the sperm population into two subpopulations with varying degrees of motility. Both sorted populations showed a significant increase in straight line velocity, reaching 63.4 ± 14.4 μm s-1 and 74 ± 13.8 μm s-1 in the first and second pools, respectively from 35.2 ± 27.2 μm s-1 in raw semen. Additionally, sorted populations demonstrated over 30% reduction in DNA fragmentation index, an indication that the proposed device selects for undamaged sperms with high quality. Apart from the biological superiority of the sorted sperms, this device presents itself as an easy and clinically-applicable method for the separation of progressive motile sperms, while at the same time, benefiting from a straightforward procedure for sperm retrieval.

Localized Photodynamic Therapy Using a Chlorin e6-Embedded Silicone-Covered Self-Expandable Metallic Stent as a Palliative Treatment for Malignant Esophageal Strictures

Localized photodynamic therapy (PDT) uses a polymeric-photosensitizer (PS)-embedded, covered self-expandable metallic stent (SEMS). PDT is minimally invasive and a noteworthy potential alternative for treating esophageal strictures, where surgery is not a viable option. However, preclinical evidence is insufficient, and optimized irradiation energy dose ranges for localized PDT are unclear. Herein, we validated the irradiation energy doses of the SEMS (embedded in a PS using chlorin e6 [Ce6] and covered in silicone) and PDT-induced tissue changes in a rat esophagus. Cytotoxicity and phototoxicity in the Ce6-embedded SEMS piece with laser irradiation were significantly higher than that of the silicone-covered SEMS with or without laser and the Ce6-embedded silicone-covered SEMS without laser groups (all p < 0.001). Moreover, surface morphology, atomic changes, and homogeneous coverage of the Ce6-embedded silicone-covered membrane were confirmed. The ablation range of the porcine liver was proportionally increased with the irradiation dose (all p < 0.001). The ablation region was identified at different irradiation energy doses of 50, 100, 200, and 400 J/cm2. The in vivo study in the rat esophagus comprised a control group and 100, 200, and 400 J/cm2 energy-dose groups. Finally, histology and immunohistochemistry (TUNEL and Ki67) confirmed that the optimized Ce6-embedded silicone-covered SEMS with selected irradiation energy doses (200 and 400 J/cm2) effectively damaged the esophageal tissue without ductal perforation. The polymeric PS-embedded silicone-covered SEMS can be easily placed via a minimally invasive approach and represents a promising new approach for the palliative treatment of malignant esophageal strictures.

DNA fragmentation, antioxidant activity and histological structure of cryopreserved testicular tissue depending on sexual maturity and immunological status

The objective of this work was to determine a relationship between a frequency of DNA fragmentation, a level of antioxidant activity and a preservation of histological structure depending on initial status of fragments of seminiferous tubules of testes (FSTT) of rats at the stages of cryopreservation. FSTT of animals of different ages (immature, mature), as well as animals with changed immunological status (adjuvant arthritis) were cryopreserved. Slow uncontrolled freezing was used in a cryomedium of fibrin gel with 0.7 M glycerol. The results showed that viability, TAS, γGGT and G6PD activities had the highest values in the group of intact immature animals both in fresh FSTT and after exposure to cryomedium or cryopreservation, while the indexes of DNA fragmentation and ROS content had the lowest values. It was found that an increase in the DNA fragmentation rate occurred in parallel with a decrease in the values of antioxidant activity and membrane integrity. The spermatogenenic epithelium after cryopreservation differed between the groups in a relative number of cells with pathologically changed nuclei and the frequency of exfoliation of epithelial cells into the tubule cavity namely, there was a tendency to an increase in the damaging effects in the series, "Immature → Sexually mature → Autoimmune arthritis". The obtained data can be taken into account in the development of low-temperature preservation protocols using cryotechnologies, which will ensure the maintenance of the morphological and functional characteristics of FSTT depending on sexual maturity and immunological status.

Functionalized biomimetic mineralized collagen promotes osseointegration of 3D-printed titanium alloy microporous interface

Mineralized collagen (MC) is the fundamental unit of natural bone tissue and can induce bone regeneration. Unmodified MC has poor mechanical properties and a single component, making it unable to cope with complex physiological environment. In this study, we introduced sodium alginate (SA) and vascular endothelial growth factor (VEGF) into the MC material to construct functionalized mineralized collagen (FMC) with good mechanical strength and the ability to continuously release growth factors. The FMC is filled into the pores of 3D printed titanium alloy scaffold to form a new organic-inorganic bioactive interface. With the continuous degradation of FMC, bone marrow mesenchymal stem cells (BMSCs) and vascular endothelial cells (VECs) in the surrounding environment are recruited to the surface of the scaffold to promote bone and vascular regeneration. After implanting the scaffold into the distal femoral defect of rabbits, Micro CT, histological, push-out, as well as immunohistochemical analysis showed that the composite interface can significantly promote osseointegration. These findings provide a new strategy for the development and application of mineralized collagen materials.

Scaffold-based non-viral CRISPR delivery platform for efficient and prolonged gene activation to accelerate tissue regeneration

Clustered regularly interspaced short palindromic repeat activation (CRISPRa) technology has emerged as a precise genome editing tool for activating endogenous transgene expression. While it holds promise for precise cell modification, its translation into tissue engineering has been hampered by biosafety concerns and suboptimal delivery methods. To address these challenges, we have developed a CRISPRa non-viral gene delivery platform by immobilizing non-viral CRISPRa complexes into a biocompatible hydrogel/nanofiber (Gel/NF) composite scaffold. The Gel/NF scaffold facilitates the controlled and sustained release of CRISPRa complexes and also promotes cell recruitment to the scaffold for efficient and localized transfection. As a proof of concept, we employed this CRISPRa delivery platform to activate the vascular endothelial growth factor (VEGF) gene in a rat model with full-thickness skin defects. Our results demonstrate sustained upregulation of VEGF expression even at 21 days post-implantation, resulting in enhanced angiogenesis and improved skin regeneration. These findings underscore the potential of the Gel/NF scaffold-based CRISPRa delivery platform as an efficient and durable strategy for gene activation, offering promising prospects for tissue regeneration. STATEMENT OF SIGNIFICANCE: Translation of clustered regularly interspaced short palindromic repeat activation (CRISPRa) therapy to tissue engineering is limited by biosafety concerns and unsatisfactory delivery strategy. To solve this issue, we have developed a CRISPRa non-viral gene delivery platform by immobilizing non-viral CRISPRa complexes into a biocompatible hydrogel/nanofiber (Gel/NF) composite scaffold. This scaffold enables controlled and sustained release of CRISPRa and can induce cell recruitment for localized transfection. As a proof of concept, we activated vascular endothelial growth factor (VEGF) in a rat model with full-thickness skin defects, leading to sustained upregulation of VEGF expression, enhanced angiogenesis and improved skin regeneration in vivo. These findings demonstrate the potential of this platform for gene activation, thereby offering promising prospects for tissue regeneration.

The microspheres/hydrogels scaffolds based on the proteins, nucleic acids, or polysaccharides composite as carriers for tissue repair: A review

There are many studies on specific macromolecules and their contributions to tissue repair. Macromolecules have supporting and protective effects in organisms and can help regrow, reshape, and promote self-repair and regeneration of damaged tissues. Macromolecules, such as proteins, nucleic acids, and polysaccharides, can be constructed into hydrogels for the preparation of slow-release drug agents, carriers for cell culture, and platforms for gene delivery. Hydrogels and microspheres are fabricated by chemical crosslinking or mixed co-deposition often used as scaffolds, drug carriers, or cell culture matrix, provide proper mechanical support and nutrient delivery, a well-conditioned environment that to promote the regeneration and repair of damaged tissues. This review provides a comprehensive overview of recent developments in the construction of macromolecules into hydrogels and microspheres based on the proteins, nucleic acids, polysaccharides and other polymer and their application in tissue repair. We then discuss the latest research trends regarding the advantages and disadvantages of these composites in repair tissue. Further, we examine the applications of microspheres/hydrogels in different tissue repairs, such as skin tissue, cartilage, tumor tissue, synovial, nerve tissue, and cardiac repair. The review closes by highlighting the challenges and prospects of microspheres/hydrogels composites.

Mimicked Spinal Cord Fibers Trigger Axonal Regeneration and Remyelination after Injury

Spinal cord injury (SCI) causes tissue structure damage and composition changes of the neural parenchyma, resulting in severe consequences for spinal cord function. Mimicking the components and microstructure of spinal cord tissues holds promise for restoring the regenerative microenvironment after SCI. Here, we have utilized electrospinning technology to develop aligned decellularized spinal cord fibers (A-DSCF) without requiring synthetic polymers or organic solvents. A-DSCF preserves multiple types of spinal cord extracellular matrix proteins and forms a parallel-oriented structure. Compared to aligned collagen fibers (A-CF), A-DSCF exhibits stronger mechanical properties, improved enzymatic stability, and superior functionality in the adhesion, proliferation, axonal extension, and myelination of differentiated neural progenitor cells (NPCs). Notably, axon extension or myelination has been primarily linked to Agrin (AGRN), Laminin (LN), or Collagen type IV (COL IV) proteins in A-DSCF. When transplanted into rats with complete SCI, A-DSCF loaded with NPCs improves the survival, maturation, axon regeneration, and motor function of the SCI rats. These findings highlight the potential of structurally and compositionally biomimetic scaffolds to promote axonal extension and remyelination after SCI.

Application of Nondegradable Synthetic Materials for Tendon and Ligament Injury

Tendon and ligament injuries, prevalent requiring surgical intervention, significantly impact joint stability and function. Owing to excellent mechanical properties and biochemical stability, Nondegradable synthetic materials, including polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE), have demonstrated significant potential in the treatment of tendon and ligament injuries. These above materials offer substantial mechanical support, joint mobility, and tissue healing promotion of the shoulder, knee, and ankle joint. This review conclude the latest development and application of nondegradable materials such as artificial patches and ligaments in tendon and ligament injuries including rotator cuff tears (RCTs), anterior cruciate ligament (ACL) injuries, and Achilles tendon ruptures.

Nanofiber Composite Microchannel-Containing Injectable Hydrogels for Cartilage Tissue Regeneration

Articular cartilage tissue is incapable of self-repair and therapies for cartilage defects are still lacking. Injectable hydrogels have drawn much attention in the field of cartilage regeneration. Herein, the novel design of nanofiber composite microchannel-containing hydrogels inspired by the tunnel-piled structure of subway tunnels is proposed. Based on the aldehydized polyethylene glycol/carboxymethyl chitosan (APA/CMCS) hydrogels, thermosensitive gelatin microrods (GMs) are used as a pore-forming agent, and coaxial electrospinning polylactic acid/gelatin fibers (PGFs) loaded with kartogenin (KGN) are used as a reinforcing agent and a drug delivery system to construct the nanofiber composite microchannel-containing injectable hydrogels (APA/CMCS/KGN@PGF/GM hydrogels). The in situ formation, micromorphology and porosity, swelling and degradation, mechanical properties, self-healing behavior, as well as drug release of the nanofiber composite microchannel-containing hydrogels are investigated. The hydrogel exhibits good self-healing ability, and the introduction of PGF nanofibers can significantly improve the mechanical properties. The drug delivery system can realize sustained release of KGN to match the process of cartilage repair. The microchannel structure effectively promotes bone marrow mesenchymal stem cell (BMSC) proliferation and ingrowth within the hydrogels. In vitro and animal experiments indicate that the APA/CMCS/KGN@PGF/GM hydrogels can enhance the chondrogenesis of BMSCs and promote neocartilage formation in the rabbit cartilage defect model.

Three-dimensional printing of cell-laden bioink for blood vessel tissue engineering: influence of process parameters and components on cell viability

Three-dimensional (3D) bioprinting is a potential therapeutic method for tissue engineering owing to its ability to prepare cell-laden tissue constructs. The properties of bioink are crucial to accurately control the printing structure. Meanwhile, the effect of process parameters on the precise structure is not nonsignificant. We investigated the correlation between process parameters of 3D bioprinting and the structural response of κ-carrageenan-based hydrogels to explore the controllable structure, printing resolution, and cell survival rate. Small-diameter (<6 mm) gel filaments with different structures were printed by varying the shear stress of the extrusion bioprinter to simulate the natural blood vessel structure. The cell viability of the scaffold was evaluated. The in vitro culture of human umbilical vein endothelium cells (HUVECs) on the κ-carrageenan (kc) and composite gels (carrageenan/carbon nanotube and carrageenan/sodium alginate) demonstrated that the cell attachment and proliferation on composite gels were better than those on pure kc. Our results revealed that the carrageenan-based composite bioinks offer better printability, sufficient mechanical stiffness, interconnectivity, and biocompatibility. This process can facilitate precise adjustment of the pore size, porosity, and pore distribution of the hydrogel structure by optimising the printing parameters as well as realise the precise preparation of the internal structure of the 3D hydrogel-based tissue engineering scaffold. Moreover, we obtained perfused tubular filament by 3D printing at optimal process parameters.

Microvascular endothelial cells derived from spinal cord promote spinal cord injury repair

Neural regeneration after spinal cord injury (SCI) closely relates to the microvascular endothelial cell (MEC)-mediated neurovascular unit formation. However, the effects of central nerve system-derived MECs on neovascularization and neurogenesis, and potential signaling involved therein, are unclear. Here, we established a primary spinal cord-derived MECs (SCMECs) isolation with high cell yield and purity to describe the differences with brain-derived MECs (BMECs) and their therapeutic effects on SCI. Transcriptomics and proteomics revealed differentially expressed genes and proteins in SCMECs were involved in angiogenesis, immunity, metabolism, and cell adhesion molecular signaling was the only signaling pathway enriched of top 10 in differentially expressed genes and proteins KEGG analysis. SCMECs and BMECs could be induced angiogenesis by different stiffness stimulation of PEG hydrogels with elastic modulus 50-1650 Pa for SCMECs and 50-300 Pa for BMECs, respectively. Moreover, SCMECs and BMECs promoted spinal cord or brain-derived NSC (SNSC/BNSC) proliferation, migration, and differentiation at different levels. At certain dose, SCMECs in combination with the NeuroRegen scaffold, showed higher effectiveness in the promotion of vascular reconstruction. The potential underlying mechanism of this phenomenon may through VEGF/AKT/eNOS- signaling pathway, and consequently accelerated neuronal regeneration and functional recovery of SCI rats compared to BMECs. Our findings suggested a promising role of SCMECs in restoring vascularization and neural regeneration.