3D bioprinting-a model for skin aging

Functional regeneration strategies of hair follicles: advances and challenges

Hair follicles are essential appendages of human skin that function in protection, sensation, thermoregulation and social interactions. The multicellular components, particularly the dermal papilla, matrix and bulge housing stem cells, enable cyclic hair growth postnatally. However, miniaturization and loss of hair follicles can occur in the context of ageing, trauma and various alopecia-related diseases. Conventional treatments involve the redistribution of existing follicles, which may not be viable in patients lacking follicular resources. Recent progress in the comprehension of morphogenesis and the development of biomaterials has significantly advanced follicle reconstruction, incorporating organ germ assembling, stem cell induction and bioprinting techniques. Despite these advancements, fully restoring hair follicles remains challenging due to the complexities of replicating embryonic signals and sustaining growth cycles. Identifying suitable cell sources for clinical applications also presents a hurdle. Here, we retrospect the progress made in the field of hair follicle regeneration, aiming to offer an exhaustive analysis on the benefits and limitations of these methods, and to foster the development of innovative solutions.

Evaluation of Drug Permeation Enhancement by Using In Vitro and Ex Vivo Models

Drugs administered by means of extravascular routes of drug administration must be absorbed into the systemic circulation, which involves the movement of the drug molecules across biological barriers such as epithelial cells that cover mucosal surfaces or the stratum corneum that covers the skin. Some drugs exhibit poor permeation across biological membranes or may experience excessive degradation during first-pass metabolism, which tends to limit their bioavailability. Various strategies have been used to improve drug bioavailability. Absorption enhancement strategies include the co-administration of chemical permeation enhancers, enzymes, and/or efflux transporter inhibitors, chemical changes, and specialized dosage form designs. Models with physiological relevance are needed to evaluate the efficacy of drug absorption enhancement techniques. Various in vitro cell culture models and ex vivo tissue models have been explored to evaluate and quantify the effectiveness of drug permeation enhancement strategies. This review deliberates on the use of in vitro and ex vivo models for the evaluation of drug permeation enhancement strategies for selected extravascular drug administration routes including the nasal, oromucosal, pulmonary, oral, rectal, and transdermal routes of drug administration.

A Comprehensive Literature Review on Advancements and Challenges in 3D Bioprinting of Human Organs: Ear, Skin, and Bone

The field of 3D bioprinting is rapidly emerging within the realm of regenerative medicine, offering significant potential in dealing with the issue of organ shortages. Despite being in its early stages, it has the potential to replicate tissue structures accurately, providing new potential solutions for reconstructive surgery. This review explores the diverse applications of 3D bioprinting in regenerative medicine, pharmaceuticals, and the food industry, specifically focusing on ear, skin, and bone tissues due to their unique challenges and implications in the field. Significant progress has been made in cartilage and bone scaffold fabrication in ear reconstruction, yet challenges in functional maturation persist. Recent advancements highlight the potential for patient-specific ear substitutes, emphasizing the need for extensive clinical trials. In skin regeneration, 3D bioprinting addresses limitations in existing models, offering opportunities for improved wound healing and realistic skin models. While challenges exist, progress in biomaterials and in-situ bioprinting holds promise. In bone regeneration, 3D bioprinting presents personalized solutions for defects, but scaffold design refinement and addressing regulatory and ethical considerations are crucial. The transformative potential of 3D bioprinting in the field of medicine holds the promise of redefining therapeutic approaches and delivering personalized treatments and functional tissues. Interdisciplinary collaboration is essential for fully realizing the capabilities of 3D bioprinting. This review provides a detailed analysis of current methodologies, challenges, and prospects in 3D bioprinting for ear, skin, and bone tissue regeneration.

Advances in, and prospects of, 3D preclinical models for skin drug discovery

The skin has an important role in regulating homeostasis and protecting the body from endogenous and exogenous microenvironments. Although 3D models for drug discovery have been extensively studied, there is a growing demand for more advanced 3D skin models to enhance skin research. The use of these advanced skin models holds promise across domains such as cosmetics, skin disease treatments, and toxicity testing of new therapeutics. Recent advances include the development of skin-on-a-chip, spheroids, reconstructed skin, organoids, and computational approaches, including quantitative structure-activity relationship (QSAR) and quantitative structure-property relationship (QSPR) research. These innovations are bridging the gap between traditional 2D and advanced 3D models, moving progress from research to clinical applications. In this review, we highlight in vitro and computational skin models with advanced drug discovery for skin-related applications.

The interplay of skin architecture and cellular dynamics in wound healing: Insights and innovations in care strategies

Wound healing involves complex interactions among skin layers: the epidermis, which epithelializes to cover wounds; the dermis, which supports granulation tissue and collagen production; and the hypodermis, which protects overall skin structure. Key factors include neutrophils, activated by platelet degranulation and cytokines, and fibroblasts, which aid in collagen production during proliferation. The healing process encompasses inflammation, proliferation, and remodeling, with angiogenesis, fibroplasia, and re-epithelialization crucial for wound closure. Angiogenesis is characterized by the creation of collateral veins, the proliferation of endothelial cells, and the recruitment of perivascular cells. Collagen is produced by fibroblasts in granulation tissue, aiding in the contraction of wounds. The immunological response is impacted by T cells and cytokines. External topical application of various formulations and dressings expedites healing and controls microbial contamination. Polymeric materials, both natural and synthetic, and advanced dressings enhance healing by providing biodegradability, biocompatibility, and infection control, thus addressing tissue regeneration challenges. Numerous dressings promote healing, including films, hydrocolloids, hydrogels, foams, alginates, and tissue-engineered substitutes. Wound dressings are treated with growth factors, particularly PDGF, and antibacterial drugs to prevent infection. The challenges of tissue regeneration and infection control are evolving along with the field of wound care.

Application of 3D printing in the treatment of diabetic foot ulcers: current status and new insights

Background and Aims

Diabetic foot ulcers (DFUs) are a serious complication of diabetes mellitus (DM), affecting around 25% of individuals with DM. Primary treatment of a DFU involves wound off-loading, surgical debridement, dressings to provide a moist wound environment, vascular assessment, and appropriate antibiotics through a multidisciplinary approach. Three-dimensional (3D) printing technology is considered an innovative tool for the management of DFUs. The utilization of 3D printing technology in the treatment of DFU involves the modernization of traditional methods and the exploration of new techniques. This review discusses recent advancements in 3D printing technology for the application of DFU care, and the development of personalized interventions for the treatment of DFUs.

Methods

We searched the electronic database for the years 2019-2024. Studies related to the use of 3D printing technology in Diabetic foot were included.

Results

A total of 25 identified articles based on database search and citation network analysis. After removing duplicates, 18 articles remained, and three articles that did not meet the inclusion criteria were removed after reading the title/abstract. A total of 97 relevant articles were included during the reading of references. In total, 112 articles were included.

Conclusion

3D printing technology offers unparalleled advantages, particularly in the realm of personalized treatment. The amalgamation of traditional treatment methods with 3D printing has yielded favorable outcomes in decelerating the progression of DFUs and facilitating wound healing. However, there is a limited body of research regarding the utilization of 3D printing technology in the domain of DFUs.

[Research progress in repair and reconstruction of tumor-related bone defects in proximal femur]

Objective

To review the repair and reconstruction methods for large segmental femoral proximal bone defects caused by tumors, and to explore their clinical application effects, advantages, and disadvantages, and future research directions.

Methods

A comprehensive search of Chinese and foreign databases was conducted to select basic and clinical research literature related to the repair and reconstruction of femoral proximal bone defects caused by tumors. The studies were classified and analyzed based on two main strategies: hip-preserving reconstruction and non-hip-preserving reconstruction.

Results

In hip-preserving reconstruction, traditional methods such as allograft transplantation and vascularized autograft transplantation are common but have risks of poor bone integration and bone resorption. The clinical application of inactivated tumor segment reimplantation and distraction osteogenesis techniques is limited. In recent years, three-dimensional printing technology has become increasingly mature, with personalized prostheses and precise surgeries becoming development trends. Non-hip-preserving reconstruction primarily includes allograft prosthesis composite and total femoral replacement. The former focuses on improving the survival rate and bone integration efficiency of the allograft, while the latter requires the simultaneous reconstruction of hip and knee joint stability.

Conclusion

Significant progress has been made in repairing and reconstructing proximal femoral bone defects caused by tumors, but many challenges remain. The integration of three-dimensional printing technology and digital design offers potential for precise bone defect repair. Future efforts should focus on new concepts, technologies, and materials through multidisciplinary approaches to provide personalized and precise solutions, thereby improving patient quality of life.

Innovations in three-dimensional-printed individualized bone prosthesis materials: revolutionizing orthopedic surgery: a review

The advent of personalized bone prosthesis materials and their integration into orthopedic surgery has made a profound impact, primarily as a result of the incorporation of three-dimensional (3D) printing technology. By leveraging digital models and additive manufacturing techniques, 3D printing enables the creation of customized, high-precision bone implants tailored to address complex anatomical variabilities and challenging bone defects. In this review, we highlight the significant progress in utilizing 3D-printed prostheses across a wide range of orthopedic procedures, including pelvis, hip, knee, foot, ankle, spine surgeries, and bone tumor resections. The integration of 3D printing in preoperative planning, surgical navigation, and postoperative rehabilitation not only enhances treatment outcomes but also reduces surgical risks, accelerates recovery, and optimizes cost-effectiveness. Emphasizing the potential for personalized care and improved patient outcomes, this review underscores the pivotal role of 3D-printed bone prosthesis materials in advancing orthopedic practice towards precision, efficiency, and patient-centric solutions. The evolving landscape of 3D printing in orthopedic surgery holds promise for revolutionizing treatment approaches, enhancing surgical outcomes, and ultimately improving the quality of care for orthopedic patients.

3D Models Currently Proposed to Investigate Human Skin Aging and Explore Preventive and Reparative Approaches: A Descriptive Review

Skin aging is influenced by intrinsic and extrinsic factors that progressively impair skin functionality over time. Investigating the skin aging process requires thorough research using innovative technologies. This review explores the use of in vitro human 3D culture models, serving as valuable alternatives to animal ones, in skin aging research. The aim is to highlight the benefits and necessity of improving the methodology in analyzing the molecular mechanisms underlying human skin aging. Traditional 2D models, including monolayers of keratinocytes, fibroblasts, or melanocytes, even if providing cost-effective and straightforward methods to study critical processes such as extracellular matrix degradation, pigmentation, and the effects of secretome on skin cells, fail to replicate the complex tissue architecture with its intricated interactions. Advanced 3D models (organoid cultures, "skin-on-chip" technologies, reconstructed human skin, and 3D bioprinting) considerably enhance the physiological relevance, enabling a more accurate representation of skin aging and its peculiar features. By reporting the advantages and limitations of 3D models, this review highlights the importance of using advanced in vitro systems to develop practical anti-aging preventive and reparative approaches and improve human translational research in this field. Further exploration of these technologies will provide new opportunities for previously unexplored knowledge on skin aging.

The influence of viscosity of hydrogels on the spreading and migration of cells in 3D bioprinted skin cancer models

Various in vitro three-dimensional (3D) tissue culture models of human and diseased skin exist. Nevertheless, there is still room for the development and improvement of 3D bioprinted skin cancer models. The need for reproducible bioprinting methods, cell samples, biomaterial inks, and bioinks is becoming increasingly important. The influence of the viscosity of hydrogels on the spreading and migration of most types of cancer cells is well studied. There are however limited studies on the influence of viscosity on the spreading and migration of cells in 3D bioprinted skin cancer models. In this review, we will outline the importance of studying the various types of skin cancers by using 3D cell culture models. We will provide an overview of the advantages and disadvantages of the various 3D bioprinting technologies. We will emphasize how the viscosity of hydrogels relates to the spreading and migration of cancer cells. Lastly, we will give an overview of the specific studies on cell migration and spreading in 3D bioprinted skin cancer models.

A review of biomacromolecule-based 3D bioprinting strategies for structure-function integrated repair of skin tissues

When skin is damaged or affected by diseases, it often undergoes irreversible scar formation, leading to aesthetic concerns and psychological distress for patients. In cases of extensive skin defects, the patient's life can be severely compromised. In recent years, 3D printing technology has emerged as a groundbreaking approach to skin tissue engineering, offering promising solutions to various skin-related conditions. 3D bioprinting technology enables the precise fabrication of structures by programming the spatial arrangement of cells within the skin tissue and subsequently printing skin replacements either in a 3D bioprinter or directly at the site of the defect. This study provides a comprehensive overview of various biopolymer-based inks, with a particular emphasis on chitosan (CS), starch, alginate, agarose, cellulose, and fibronectin, all of which are natural polymers belonging to the category of biomacromolecules. Additionally, it summarizes artificially synthesized polymers capable of enhancing the performance of these biomacromolecule-based bioinks, thereby composing hybrid biopolymer inks aimed at better application in skin tissue engineering endeavors. This review paper examines the recent advancements, characteristics, benefits, and limitations of biological 3D bioprinting techniques for skin tissue engineering. By utilizing bioinks containing seed cells, hydrogels with bioactive factors, and biomaterials, complex structures resembling natural skin can be accurately fabricated in a layer-by-layer manner. The importance of biological scaffolds in promoting skin wound healing and the role of 3D bioprinting in skin tissue regeneration processes is discussed. Additionally, this paper addresses the challenges and constraints associated with current 3D bioprinting technologies for skin tissue and presents future perspectives. These include advancements in bioink formulations, full-thickness skin bioprinting, vascularization strategies, and skin appendages bioprinting.

Three-dimensional printing of the human lung pleural cavity model for PDT malignant mesothelioma

OBJECTIVE

The primary aim was to investigate emerging 3D printing and optical acquisition technologies to refine and enhance photodynamic therapy (PDT) dosimetry in the management of malignant pleural mesothelioma (MPM).

MATERIALS AND METHODS

A rigorous digital reconstruction of the pleural lung cavity was conducted utilizing 3D printing and optical scanning methodologies. These reconstructions were systematically assessed against CT-derived data to ascertain their accuracy in representing critical anatomic features and post-resection topographical variations.

RESULTS

The resulting reconstructions excelled in their anatomical precision, proving instrumental translation for precise dosimetry calculations for PDT. Validation against CT data confirmed the utility of these models not only for enhancing therapeutic planning but also as critical tools for educational and calibration purposes.

CONCLUSION

The research outlined a successful protocol for the precise calculation of light distribution within the complex environment of the pleural cavity, marking a substantive advance in the application of PDT for MPM. This work holds significant promise for individualizing patient care, minimizing collateral radiation exposure, and improving the overall efficiency of MPM treatments.

Applications of Engineered Skin Tissue for Cosmetic Component and Toxicology Detection

The scale of the cosmetic market is increasing every day. There are many safety risks to cosmetics, but they benefit people at the same time. The skin can become red, swollen, itchy, chronically toxic, and senescent due to the misuse of cosmetics, triggering skin injuries, with contact dermatitis being the most common. Therefore, there is an urgent need for a system that can scientifically and rationally detect the composition and perform a toxicological assessment of cosmetic products. Traditional detection methods rely on instrumentation and method selection, which are less sensitive and more complex to perform. Engineered skin tissue has emerged with the advent of tissue engineering technology as an emerging bioengineering technology. The ideal engineered skin tissue is the basis for building good in vitro structures and physiological functions in this field. This review introduces the existing cosmetic testing and toxicological evaluation methods, the current development status, and the types and characteristics of engineered skin tissue. The application of engineered skin tissue in the field of cosmetic composition detection and toxicological evaluation, as well as the different types of tissue engineering scaffold materials and three-dimensional (3D) organoid preparation approaches, is highlighted in this review to provide methods and ideas for constructing the next engineered skin tissue for cosmetic raw material component analysis and toxicological evaluation.