Feasibility of Polycaprolactone Scaffolds Fabricated by Three-Dimensional Printing for Tissue Engineering of Tunica Albuginea

Treating critical bone defects by using core-shell biological scaffold to regulate Fibrosis-Osteogenic homeostasis

Critical bone defects pose a significant challenge in the realm of bone defect repair. During the repair process, bone formation is crucial, as the occurrence of invasive tissue growth into the defect, known as fibrosis, is also a possibility. Excessive fibrosis can lead to a "filling effect," wherein fibrous tissue occupies the bone defect area, thereby impeding the bone formation and repair processes. Hence, regulating the dynamic balance between fibrosis and osteogenesis is pivotal to effectively treat critical bone defects. To mitigate the rapid fibrosis rate at the bone defect site, which may result in repair failure, we have devised and fabricated a biomimetic core-shell scaffold-PCL-FAPI/GelMA/HAMA-GBA@plasmid-knockdown SHN-3 (PCL-FAPI/GH-GBA@pk SHN-3)-aimed at modulating fibrosis and vascularization processes within the new callus. The outer "shell" structure of the scaffold employs polycaprolactone (PCL) electrospun nanofibers loaded with fibroblast activating protein inhibitor (FAPI). Utilizing hydrophobic PCL electrospun fibers effectively impedes the growth of exogenous fibrous tissue, while releasing FAPI to inhibit the growth of endogenous fibroblasts. The inner layer "nucleus" structure comprises GelMA/HAMA hydrogel-supported plasmid/polyamideamine (GBA@plasmid-knockdown SHN-3), which enhances the secretion of Slit3 protein and promotes the formation of Type H blood vessels by silencing the SHN-3 gene in osteoblasts. The biomimetic "core-shell" scaffold PCL-FAPI/GH-GBA@pkSHN-3 serves to prevent excessive fibrosis of the callus and foster the formation of Type H blood vessels within the new callus, effectively averting bone nonunion and expediting the repair process of critical bone defects.

Corpus cavernosum and tunica albuginea reconstruction by tissue engineering: towards functional erectile structures regeneration

BACKGROUND

Current treatments for penile erectile structures reconstruction are limited and remain a great challenge in clinical practice. Tissue engineering techniques using different seed cells and scaffolds to construct a neo-tissue open promising avenues for penile erectile structures repair and replacement and show great promise in the restoration of: structure, mechanical property, and function which matches the original tissue.

METHODS

A comprehensive literature review was conducted by accessing the NCBI PubMed, Cochrane, and Google Scholar databases from January 1, 1990, to January, 1, 2022 using the search terms "Tissue engineering, Corpus cavernosum (CC), Tunica albuginea (TA), Acellular Matrix, Penile Reconstruction". Articles were screened and assessed by two independent reviewers to determine whether those met the inclusion criteria, and a total of 19 articles were being selected and included in the data analysis.

RESULTS

Tissue engineered cell-seeded scaffold can reconstruct a similar structure to native TA and CC and showed good histocompatibility with no immunological rejection. The results of the evaluation of morphological feature, intracavernosal pressure, and erectile-related nitric oxide (NO) expression were strongly proofs that the tissue engineered graft can significantly improve the penile erectile and ejaculatory function. In addition, increasing the purity of seed cells, improving the mechanical properties of the scaffold, providing appropriate induction for stem cells, and optimizing cell delivery systems are potential approaches to improve reconstructive outcomes. Currently, a larger animal model, comparable in size to the human penis, is needed to test the feasibility of the engineered grafts.

CONCLUSION

Our review summarized the research in tissue engineering of CC and TA. It showed great promise in reconstructing the functional structures and restoring the erection and ejaculatory function. With continuous advancement in the field, tissue-engineered penile erectile structures hold substantial potential to enhance clinical outcomes for patients.

Tissue anisotropy and collagenomics in porcine penile tunica albuginea: Implications for penile structure-function relationships and tissue engineering

The tunica albuginea (TA) of the penis is an elastic layer that serves a structural role in penile erection. Disorders affecting the TA cause pain, deformity, and erectile dysfunction. There is a substantial clinical need for engineered replacements of TA, but data are scarce on the material properties and biochemical composition of healthy TA. The objective of this study was to assess tissue organization, protein content, and mechanical properties of porcine TA to establish structure-function relationships and design criteria for tissue engineering efforts. TA was isolated from six pigs and subjected to histomorphometry, quantification of collagen content and pyridinoline crosslinks, bottom-up proteomics, and tensile mechanical testing. Collagen was 20 ± 2%/wet weight (WW) and 53 ± 4%/dry weight (DW). Pyridinoline content was 426 ±131 ng/mg WW, 1011 ± 190 ng/mg DW, and 45 ± 8 mmol/mol hydroxyproline. Bottom-up proteomics identified 14 proteins with an abundance of >0.1% of total protein. The most abundant collagen subtype was type I, representing 95.5 ± 1.5% of the total protein in the samples. Collagen types III, XII, and VI were quantified at 1.7 ± 1.0%, 0.8 ± 0.2%, and 0.4 ± 0.2%, respectively. Tensile testing revealed anisotropy: Young's modulus was significantly higher longitudinally than circumferentially (60 ± 18 MPa vs. 8 ± 5 MPa, p < 0.01), as was ultimate tensile strength (16 ± 4 MPa vs. 3 ± 3 MPa, p < 0.01). Taken together, the tissue mechanical and compositional data obtained in this study provide important benchmarks for the development of TA biomaterials. STATEMENT OF SIGNIFICANCE: The tunica albuginea of the penis serves an important structural role in physiologic penile erection. This tissue can become damaged by disease or trauma, leading to pain and deformity. Treatment options are limited. Little is known about the precise biochemical composition and biomechanical properties of healthy tunica albuginea. In this study, we characterize the tissue using proteomic analysis and tensile testing to establish design parameters for future tissue engineering efforts. To our knowledge, this is the first study to quantify tissue anisotropy and to use bottom-up proteomics to characterize the composition of penile tunica albuginea.

Tailor-made natural and synthetic grafts for precise urethral reconstruction

Injuries to the urethra can be caused by malformations, trauma, inflammation, or carcinoma, and reconstruction of the injured urethra is still a significant challenge in clinical urology. Implanting grafts for urethroplasty and end-to-end anastomosis are typical clinical interventions for urethral injury. However, complications and high recurrence rates remain unsatisfactory. To address this, urethral tissue engineering provides a promising modality for urethral repair. Additionally, developing tailor-made biomimetic natural and synthetic grafts is of great significance for urethral reconstruction. In this work, tailor-made biomimetic natural and synthetic grafts are divided into scaffold-free and scaffolded grafts according to their structures, and the influence of different graft structures on urethral reconstruction is discussed. In addition, future development and potential clinical application strategies of future urethral reconstruction grafts are predicted.

3D Bioprinting of Polycaprolactone-Based Scaffolds for Pulp-Dentin Regeneration: Investigation of Physicochemical and Biological Behavior

In this study, two structurally different scaffolds, a polycaprolactone (PCL)/45S5 Bioglass (BG) composite and PCL/hyaluronic acid (HyA) were fabricated by 3D printing technology and were evaluated for the regeneration of dentin and pulp tissues, respectively. Their physicochemical characterization was performed by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle, and compressive strength tests. The results indicated that the presence of BG in the PCL/BG scaffolds promoted the mechanical properties, surface roughness, and bioactivity. Besides, a surface treatment of the PCL scaffold with HyA considerably increased the hydrophilicity of the scaffolds which led to an enhancement in cell adhesion. Furthermore, the gene expression results showed a significant increase in expression of odontogenic markers, e.g., dentin sialophosphoprotein (DSPP), osteocalcin (OCN), and dentin matrix protein 1 (DMP-1) in the presence of both PCL/BG and PCL/HyA scaffolds. Moreover, to examine the feasibility of the idea for pulp-dentin complex regeneration, a bilayer PCL/BG-PCL/HyA scaffold was successfully fabricated and characterized by FESEM. Based on these results, it can be concluded that PCL/BG and PCL/HyA scaffolds have great potential for promoting hDPSC adhesion and odontogenic differentiation.

The Role of 3D-Printed Phantoms and Devices for Organ-specified Appliances in Urology

Urology is one of the fields that are always at the frontline of bringing scientific advancements into clinical practice, including 3D printing (3DP). This study aims to discuss and presents the current role of 3D-printed phantoms and devices for organ-specified applications in urology. The discussion started with a literature search regarding the two mentioned topics within PubMed, Embase, Scopus, and EBSCOhost databases. 3D-printed urological organ phantoms are reported for providing residents new insight regarding anatomical characteristics of organs, either normal or diseased, in a tangible manner. Furthermore, 3D-printed organ phantoms also helped urologists to prepare a pre-surgical planning strategy with detailed anatomical models of the diseased organs. In some centers, 3DP technology also contributed to developing specified devices for disease management. To date, urologists have been benefitted by 3D-printed phantoms and devices in the education and disease management of organs of in the genitourinary system, including kidney, bladder, prostate, ureter, urethra, penis, and adrenal. It is safe to say that 3DP technology can bring remarkable changes to daily urological practices.

Innovation in Urology: Three Dimensional Printing and Its Clinical Application

Three-dimensional (3D) printing allows rapid prototyping of novel equipment as well as the translation of medical imaging into tangible replicas of patient-specific anatomy. The technology has emerged as a versatile medium for innovation in medicine but with ever-expanding potential uses, does 3D printing represent a valuable adjunct to urological practice? We present a concise systematic review of articles on 3D printing within urology, outlining proposed benefits and the limitations in evidence supporting its utility. We review publications prior to December 2019 using guidelines outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. Of 117 identified articles, 67 are included highlighting key areas of research as the use of patient-specific models for patient education, surgical planning, and surgical training. Further novel applications included printed surgical tools, patient-specific surgical guides, and bioprinting of graft tissues. We conclude to justify its adoption within standard practice, further research is required demonstrating that use of 3D printing can produce; direct and measurable improvements in patient experience, consistent evidence of superior surgical outcomes or simulation which surpasses existing means' both in fidelity and enhancement of surgical skills. Although exploration of 3D printing's urological applications remains nascent, the seemingly limitless scope for innovation and collaborative design afforded by the technology presents undeniable value as a resource and assures a place at the forefront of future advances.

Current applications of three-dimensional printing in urology

Three-dimensional (3D) printing or additive manufacturing is a new technology that has seen rapid development in recent years with decreasing costs. 3D printing allows the creation of customised, finely detailed constructs. Technological improvements, increased printer availability, decreasing costs, improved cell culture techniques, and biomaterials have enabled complex, novel and individualised medical treatments to be developed. Although the long-term goal of printing biocompatible organs has not yet been achieved, major advances have been made utilising 3D printing in biomedical engineering. In this literature review, we discuss the role of 3D printing in relation to urological surgery. We highlight the common printing methods employed and show examples of clinical urological uses. Currently, 3D printing can be used in urology for education of trainees and patients, surgical planning, creation of urological equipment, and bioprinting. In this review, we summarise the current applications of 3D-printing technology in these areas of urology.