Advancements of 3D bioprinting in regenerative medicine: Exploring cell sources for organ fabrication

Limbal explant cultures on amniotic membrane: The effects of passaging the explants on cell phenotype

In vitro expansion of limbal epithelial stem cells (LESCs) while maintaining their characteristics has the potential to address the urgent need in ophthalmology clinics for the treatment of limbal stem cell deficiency (LSCD). Herein, we investigated the impact of explant passaging on the phenotype of LESCs cultured on human amniotic membrane (hAM). Following initial coverage of the hAM surface by cells (passage 0), the rabbit limbal explants underwent two additional passages. Expanded cells were then counted using a hemocytometer and examined by immunocytochemistry and RT-qPCR to assess markers associated with LESCs (ABCG2, P63, CK14, CXCR4, BMI-1, and vimentin) and differentiated LESCs (CK3 and connexin 43). The cell yield of passage 1 was the highest among all passages. Immunocytochemistry analysis revealed that the number of CK14-positive cells was similar across all passages; vimentin-positive cells were the lowest in passage 0, while vimentin-positive cells were the highest in passage 1; and CK3-positive cells were the highest in passage 0. RT-qPCR analysis revealed that CK3 and connexin 43 expression was significantly higher in passage 0 cells than in passage 2 cells; and CXCR4 and BMI-1 expressions were significantly higher in passage 1 cells than in passage 0 cells. Our data highlight that the passaging of limbal explant on hAM results in varying cell characteristics. The decrease in CK3 and increase in ABCG2 expression in cells obtained by passaging the limbal explant suggest that passaging could potentially enhance the stem cell population within the in vitro limbal explant culture on hAM.

Transcriptomic and proteomic integrated analysis reveals molecular mechanisms of 3D bioprinted vaginal scaffolds in vaginal regeneration

3D Bioprinting technology has been applied to vaginal reconstruction with satisfactory results. Understanding the transcriptome and proteome of regenerated vaginas is essential for knowing how biomaterials and seed cells contribute to vaginal regeneration. There are no reports on the systemic analysis of vaginal regeneration transcriptomes or proteomes. This study aims to explore the transcriptomic and proteomic features of vaginal tissue reconstructed with 3D bioprinted scaffolds. The scaffolds were made with biomaterials and bone marrow-derived mesenchymal stem cells (BMSCs) and then transplanted into a rabbit model.rna sequencing was used to analyze the transcriptomes of reconstructed and normal vaginal tissues, identifying 11,956 differentially expressed genes (DEGs). Proteomic analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and data-independent acquisition (DIA) identified 7,363 differentially expressed proteins (DEPs). Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses were performed on DEGs and deps. Results showed that DEGs and deps.were involved in extracellular matrix remodeling, angiogenesis, inflammatory response, epithelialization, and muscle formation. This study shows that 3D bioprinted scaffolds are feasible for vaginal reconstruction and offers new insights into the molecular mechanisms involved.

Innovative 3D printing technologies and advanced materials revolutionizing orthopedic surgery: current applications and future directions

Three-dimensional (3D) printing has rapidly become a transformative force in orthopedic surgery, enabling the creation of highly customized and precise medical implants and surgical tools. This review aims to provide a more systematic and comprehensive perspective on emerging 3D printing technologies-ranging from extrusion-based methods and bioink printing to powder bed fusion-and the broadening array of materials, including bioactive agents and cell-laden inks. We highlight how these technologies and materials are employed to fabricate patient-specific implants, surgical guides, prosthetics, and advanced tissue engineering scaffolds, significantly enhancing surgical outcomes and patient recovery. Despite notable progress, the field faces challenges such as optimizing mechanical properties, ensuring structural integrity, addressing regulatory complexities across different regions, and considering environmental impacts and cost barriers, especially in low-resource settings. Looking ahead, innovations in smart materials and functionally graded materials (FGMs), along with advancements in bioprinting, hold promise for overcoming these obstacles and expanding the capabilities of 3D printing in orthopedics. This review underscores the pivotal role of interdisciplinary collaboration and ongoing research in harnessing the full potential of additive manufacturing, ultimately paving the way for more effective, personalized, and durable orthopedic solutions that improve patient quality of life.

Bioprinting approaches in cardiac tissue engineering to reproduce blood-pumping heart function

The heart, with its complex structural and functional characteristics, plays a critical role in sustaining life by pumping blood throughout the entire body to supply nutrients and oxygen. Engineered heart tissues have been introduced to reproduce heart functions to understand the pathophysiological properties of the heart and to test and develop potential therapeutics. Although numerous studies have been conducted in various fields to increase the functionality of heart tissue to be similar to reality, there are still many difficulties in reproducing the blood-pumping function of the heart. In this review, we discuss advancements in cells, biomaterials, and biofabrication in cardiac tissue engineering to achieve cardiac models that closely mimic the pumping function. Moreover, we provide insight into future directions by proposing future perspectives to overcome remaining challenges, such as scaling up and biomimetic patterning of blood vessels and nerves through bioprinting.

Three-Dimensional Printing/Bioprinting and Cellular Therapies for Regenerative Medicine: Current Advances

The application of three-dimensional (3D) printing/bioprinting technologies and cell therapies has garnered significant attention due to their potential in the field of regenerative medicine. This paper aims to provide a comprehensive overview of 3D printing/bioprinting technology and cell therapies, highlighting their results in diverse medical applications, while also discussing the capabilities and limitations of their combined use. The synergistic combination of 3D printing and cellular therapies has been recognised as a promising and innovative approach, and it is expected that these technologies will progressively assume a crucial role in the treatment of various diseases and conditions in the foreseeable future. This review concludes with a forward-looking perspective on the future impact of these technologies, highlighting their potential to revolutionize regenerative medicine through enhanced tissue repair and organ replacement strategies.

Bioprinting 3D lattice-structured lumens using polyethylene glycol diacrylate (PEGDA) combined with self-assembling peptide nanofibers as hybrid bioinks for anchorage dependent cells

There is a pressing need for new cell-laden, printable bioinks to mimic stiffer tissues such as cartilage, fibrotic tissue and bone. PEGDA monomers are bioinks that crosslink with light to form a viscoelastic solid, however, they lack cell adhesion properties. Here, we utilized a hybrid bioink by combining self-assembled peptide nanofibers with PEGDA for 3D printing lumens. Adult human dermal fibroblast (aHDF) cells were first seeded in peptide-laden in 2D and 3D layers and cell behavior were studied. The cell's morphology remained spheres when they were infused in the 3D hydrogel and highly aligned with 2D overlay hydrogels. HDF cells did not adhere to unmodified PEGDA lumens, however, they successfully attached and proliferated on PEGDA/peptide lumens. Moreover, HDF cells seeded on the hybrid PEGDA/peptide lumens displayed a distinct spread F-actin morphology. The results showcase the potential of peptide hydrogels in facilitating interaction of anchorage dependent cells with PEGDA structures.

Advanced 3D bioprinted liver models with human-induced hepatocytes for personalized toxicity screening

The development of advanced in vitro models for assessing liver toxicity and drug responses is crucial for personalized medicine and preclinical drug development. 3D bioprinting technology provides opportunities to create human liver models that are suitable for conducting high-throughput screening for liver toxicity. In this study, we fabricated a humanized liver model using human-induced hepatocytes (hiHeps) derived from human fibroblasts via a rapid and efficient reprogramming process. These hiHeps were then employed in 3D bioprinted liver models with bioink materials that closely mimic the natural extracellular matrix. The constructed humanized 3D bioprinted livers (h3DPLs) exhibited mature hepatocyte functions, including albumin expression, glycogen storage, and uptake/release of indocyanine green and acetylated low-density lipoprotein. Notably, h3DPLs demonstrated increased sensitivity to hepatotoxic agents such as acetaminophen (APAP), making them a promising platform for studying drug-induced liver injury. Furthermore, our model accurately reflected the impact of rifampin, a cytochrome P450 inducer, on CYP2E1 levels and APAP hepatotoxicity. These results highlight the potential of hiHep-based h3DPLs as a cost-effective and high-performance alternative for personalized liver toxicity screening and preclinical drug testing, paving the way for improved drug development strategies and personalized therapeutic interventions.

Evaluating cells metabolic activity of bioinks for bioprinting: the role of cell-laden hydrogels and 3D printing on cell survival

Introduction

Tissue engineering has advanced significantly in recent years, owing primarily to additive manufacturing technology and the combination of biomaterials and cells known as 3D cell printing or Bioprinting. Nonetheless, various obstacles remain developing adequate 3D printed structures for biomedical applications, including bioinks optimization to meet biocompatibility and printability standards. Hydrogels are among the most intriguing bioinks because they mimic the natural extracellular matrix found in connective tissues and can create a highly hydrated environment that promotes cell attachment and proliferation; however, their mechanical properties are weak and difficult to control, making it difficult to print a proper 3D structure.

Methods

In this research, hydrogels based on Alginate and Gelatin are tested to evaluate the metabolic activity, going beyond the qualitative evaluation of cell viability. The easy-to-make hydrogel has been chosen due to the osmotic requirements of the cells for their metabolism, and the possibility to combine temperature and chemical crosslinking. Different compositions (%w/v) are tested (8% gel-7% alg, 4% gel-4% alg, 4% gel-2% alg), in order to obtain a 3D structure up to 10.3 ± 1.4 mm.

Results

The goal of this paper is to validate the obtained cell-laden 3D structures in terms of cell metabolic activity up to 7 days, further highlighting the difference between printed and not printed cell-laden hydrogels. To this end, MS5 cells viability is determined by implementing the live/dead staining with the analysis of the cellular metabolic activity through ATP assay, enhancing the evaluation of the actual cells activity over cells number.

Discussion

The results of the two tests are not always comparable, indicating that they are not interchangeable but provide complementary pieces of information.

Application of 3D-Printed Bioinks in Chronic Wound Healing: A Scoping Review

Chronic wounds, such as diabetic foot ulcers, pressure ulcers, and venous ulcers, pose significant clinical challenges and burden healthcare systems worldwide. The advent of 3D bioprinting technologies offers innovative solutions for enhancing chronic wound care. This scoping review evaluates the applications, methodologies, and effectiveness of 3D-printed bioinks in chronic wound healing, focusing on bioinks incorporating living cells to facilitate wound closure and tissue regeneration. Relevant studies were identified through comprehensive searches in databases, including PubMed, Scopus, and Web of Science databases, following strict inclusion criteria. These studies employ various 3D bioprinting techniques, predominantly extrusion-based, to create bioinks from natural or synthetic polymers. These bioinks are designed to support cell viability, promote angiogenesis, and provide structural integrity to the wound site. Despite these promising results, further research is necessary to optimize bioink formulations and printing parameters for clinical application. Overall, 3D-printed bioinks offer a transformative approach to chronic wound care, providing tailored and efficient solutions. Continued development and refinement of these technologies hold significant promise for improving chronic wound management and patient outcomes.

Beyond hype: unveiling the Real challenges in clinical translation of 3D printed bone scaffolds and the fresh prospects of bioprinted organoids

Bone defects pose significant challenges in healthcare, with over 2 million bone repair surgeries performed globally each year. As a burgeoning force in the field of bone tissue engineering, 3D printing offers novel solutions to traditional bone transplantation procedures. However, current 3D-printed bone scaffolds still face three critical challenges in material selection, printing methods, cellular self-organization and co-culture, significantly impeding their clinical application. In this comprehensive review, we delve into the performance criteria that ideal bone scaffolds should possess, with a particular focus on the three core challenges faced by 3D printing technology during clinical translation. We summarize the latest advancements in non-traditional materials and advanced printing techniques, emphasizing the importance of integrating organ-like technologies with bioprinting. This combined approach enables more precise simulation of natural tissue structure and function. Our aim in writing this review is to propose effective strategies to address these challenges and promote the clinical translation of 3D-printed scaffolds for bone defect treatment.

Conformal 3D Printing Algorithm for Surfaces and Its In Situ Repair Applications

Conformal 3D printing can construct specific three-dimensional structures on the free-form surfaces of target objects, achieving in situ additive manufacturing and repair, making it one of the cutting-edge technologies in the current field of 3D printing. To further improve the repair efficacy in tissue engineering, this study proposes a conformal path planning algorithm for in situ printing in specific areas of the target object. By designing the conformal 3D printing algorithm and utilizing vector projection and other methods, coordinate transformation of the printing trajectory was achieved. The algorithm was validated, showing good adherence of the printing material to the target surface. In situ repair experiments were also conducted on human hands and pig tibia defect models, verifying the feasibility of this method and laying a foundation for further research in personalized medicine and tissue repair.

Focus on seed cells: stem cells in 3D bioprinting of corneal grafts

Corneal opacity is one of the leading causes of severe vision impairment. Corneal transplantation is the dominant therapy for irreversible corneal blindness. However, there is a worldwide shortage of donor grafts and consequently an urgent demand for alternatives. Three-dimensional (3D) bioprinting is an innovative additive manufacturing technology for high-resolution distribution of bioink to construct human tissues. The technology has shown great promise in the field of bone, cartilage and skin tissue construction. 3D bioprinting allows precise structural construction and functional cell printing, which makes it possible to print personalized full-thickness or lamellar corneal layers. Seed cells play an important role in producing corneal biological functions. And stem cells are potential seed cells for corneal tissue construction. In this review, the basic anatomy and physiology of the natural human cornea and the grafts for keratoplasties are introduced. Then, the applications of 3D bioprinting techniques and bioinks for corneal tissue construction and their interaction with seed cells are reviewed, and both the application and promising future of stem cells in corneal tissue engineering is discussed. Finally, the development trends requirements and challenges of using stem cells as seed cells in corneal graft construction are summarized, and future development directions are suggested.

Nanoformulations in Pharmaceutical and Biomedical Applications: Green Perspectives

This study provides a brief discussion of the major nanopharmaceuticals formulations as well as the impact of nanotechnology on the future of pharmaceuticals. Effective and eco-friendly strategies of biofabrication are also highlighted. Modern approaches to designing pharmaceutical nanoformulations (e.g., 3D printing, Phyto-Nanotechnology, Biomimetics/Bioinspiration, etc.) are outlined. This paper discusses the need to use natural resources for the "green" design of new nanoformulations with therapeutic efficiency. Nanopharmaceuticals research is still in its early stages, and the preparation of nanomaterials must be carefully considered. Therefore, safety and long-term effects of pharmaceutical nanoformulations must not be overlooked. The testing of nanopharmaceuticals represents an essential point in their further applications. Vegetal scaffolds obtained by decellularizing plant leaves represent a valuable, bioinspired model for nanopharmaceutical testing that avoids using animals. Nanoformulations are critical in various fields, especially in pharmacy, medicine, agriculture, and material science, due to their unique properties and advantages over conventional formulations that allows improved solubility, bioavailability, targeted drug delivery, controlled release, and reduced toxicity. Nanopharmaceuticals have transitioned from experimental stages to being a vital component of clinical practice, significantly improving outcomes in medical fields for cancer treatment, infectious diseases, neurological disorders, personalized medicine, and advanced diagnostics. Here are the key points highlighting their importance. The significant challenges, opportunities, and future directions are mentioned in the final section.