Auricle shaping using 3D printing and autologous diced cartilage

3D printing tissue-engineered scaffolds for auricular reconstruction

Congenital microtia is the most common cause of auricular defects, with a prevalence of approximately 5.18 per 10,000 individuals. Autologous rib cartilage grafting is the leading treatment modality at this stage of auricular reconstruction currently. However, harvesting rib cartilage may lead to donor site injuries, such as pneumothorax, postoperative pain, chest wall scarring, and deformity. Therefore, in the pursuit of better graft materials, biomaterial scaffolds with great histocompatibility, precise control of morphology, non-invasiveness properties are gradually becoming a new research hotspot in auricular reconstruction. This review collectively presents the exploit and application of 3D printing biomaterial scaffold in auricular reconstruction. Although the tissue-engineered ear still faces challenges before it can be widely applied to patients in clinical settings, and its long-term effects have yet to be evaluated, we aim to provide guidance for future research directions in 3D printing biomaterial scaffold for auricular reconstruction. This will ultimately benefit the translational and clinical application of cartilage tissue engineering and biomaterials in the treatment of auricular defects.

Suitability of Ex Vivo-Expanded Microtic Perichondrocytes for Auricular Reconstruction

Tissue engineering (TE) techniques offer solutions for tissue regeneration but require large quantities of cells. For microtia patients, TE methods represent a unique opportunity for therapies with low donor-site morbidity and reliance on the surgeon's individual expertise. Microtia-derived chondrocytes and perichondrocytes are considered a valuable cell source for autologous reconstruction of the pinna. The aim of this study was to investigate the suitability of perichondrocytes from microtia patients for autologous reconstruction in comparison to healthy perichondrocytes and microtia chondrocytes. Perichondrocytes were isolated via two different methods: explant culture and enzymatic digestion. The isolated cells were analyzed in vitro for their chondrogenic cell properties. We examined migration activity, colony-forming ability, expression of mesenchymal stem cell markers, and gene expression profile. We found that microtic perichondrocytes exhibit similar chondrogenic properties compared to chondrocytes in vitro. We investigated the behavior in three-dimensional cell cultures (spheroids and scaffold-based 3D cell cultures) and assessed the expression of cartilage-specific proteins via immunohistochemistry, e.g., collagen II, which was detected in all samples. Our results show that perichondrocytes from microtia patients are comparable to healthy perichondrocytes and chondrocytes in terms of chondrogenic cell properties and could therefore be a promising cell source for auricular reconstruction.

Suitable characteristics in the selection of human allogeneic chondrocytes donors to increase the number of viable cells for cartilage repair

Autologous chondrocyte implantation has shown optimal long-term outcomes in the treatment of cartilage lesions. The challenge for a single-stage approach lies in obtaining sufficient number of cells with high viability. The answer could lie in supplementing or replacing them with allogenic chondrocytes coming from cadaveric donors. In the present work, we aimed to compare the number of viable cells isolated from cartilage of live and cadaveric donors and to determine the suitable characteristics of the best donors. A total of 65 samples from donors aged from 17 to 55 years, either women or men, were enrolled in this study (33 living vs. 32 cadaveric). The mean time of hours from death to processing samples in cadaveric donors was higher compared to live donors (64.3 ± 17.7 vs. 4.6±6.4). The number of isolated chondrocytes per gram of cartilage was higher in cadaveric donors (5.389 × 106 compared to 3.067 × 106 in living donors), whereas the average of cell viability was comparable in both groups (84.16% cadaveric, 87.8% alive). It is possible to obtain viable chondrocytes from cartilage harvested from cadaveric donors, reaching a similar cell number and viability to that obtained from the cartilage of living donors.

Current Status of Auricular Reconstruction Strategy Development

Microtia has severe physical and psychological impacts on patients, and auricular reconstruction offers improved esthetics and function, alleviating psychological issues. Microtia is a congenital disease caused by a multifactorial interaction of environmental and genetic factors, with complex clinical manifestations. Classification assessment aids in determining treatment strategies. Auricular reconstruction is the primary treatment for severe microtia, focusing on the selection of auricular scaffold materials, the construction of auricular morphology, and skin and soft tissue scaffold coverage. Autologous rib cartilage and synthetic materials are both used as scaffold materials for auricular reconstruction, each with advantages and disadvantages. Methods for achieving skin and soft tissue scaffold coverage have been developed to include nonexpansion and expansion techniques. In recent years, the application of digital auxiliary technology such as finite element analysis has helped optimize surgical outcomes and reduce complications. Tissue-engineered cartilage scaffolds and 3-dimensional bioprinting technology have rapidly advanced in the field of ear reconstruction. This article discusses the prevalence and classification of microtia, the selection of auricular scaffolds, the evolution of surgical methods, and the current applications of digital auxiliary technology in ear reconstruction, with the aim of providing clinical physicians with a reference for individualized ear reconstruction surgery. The focus of this work is on the current applications and challenges of tissue engineering and 3-dimensional bioprinting technology in the field of ear reconstruction, as well as future prospects.

Bioprinting of Cartilage with Bioink Based on High-Concentration Collagen and Chondrocytes

The study was aimed at the applicability of a bioink based on 4% collagen and chondrocytes for de novo cartilage formation. Extrusion-based bioprinting was used for the biofabrication. The printing parameters were tuned to obtain stable material flow. In vivo data proved the ability of the tested bioink to form a cartilage within five to six weeks after the subcutaneous scaffold implantation. Certain areas of cartilage formation were detected as early as in one week. The resulting cartilage tissue had a distinctive structure with groups of isogenic cells as well as a high content of glycosaminoglycans and type II collagen.

The Application of Cartilage Tissue Engineering with Cell-Laden Hydrogel in Plastic Surgery: A Systematic Review

BACKGROUND

As a contour-supporting material, the cartilage has a significant application value in plastic surgery. Since the development of hydrogel scaffolds with sufficient biomechanical strength and high biocompatibility, cell-laden hydrogels have been widely studied for application in cartilage bioengineering. This systematic review summarizes the latest research on engineered cartilage constructed using cell-laden hydrogel scaffolds in plastic surgery.

METHODS

A systematic review was performed by searching the PubMed and Web of Science databases using selected keywords and Medical Subject Headings search terms.

RESULTS

Forty-two studies were identified based on the search criteria. After full-text screening for inclusion and exclusion criteria, 18 studies were included. Data collected from each study included culturing form, seed cell types and sources, concentration of cells and gels, scaffold materials and bio-printing structures, and biomechanical properties of cartilage constructs. These cell-laden hydrogel scaffolds were reported to show some feasibility of cartilage engineering, including better cell proliferation, enhanced deposition of glycosaminoglycans and collagen type II in the extracellular matrix, and better biomechanical properties close to the natural state.

CONCLUSION

Cell-laden hydrogels have been widely used in cartilage bioengineering research. Through 3-dimensional (3D) printing, the cell-laden hydrogel can form a bionic contour structure. Extracellular matrix expression was observed in vivo and in vitro, and the elastic modulus was reported to be similar to that of natural cartilage. The future direction of cartilage tissue engineering in plastic surgery involves the use of novel hydrogel materials and more advanced 3D printing technology combined with biochemistry and biomechanical stimulation.

Outcomes of a new 3-D printing-assisted personalized macular buckle combined with para plana vitrectomy for myopic foveoschisis

PURPOSE

To describe and evaluate the application of a new 3-D printing-assisted personalized macular buckle for patients with myopic foveoschisis (MFS).

METHODS

Twelve eyes of 12 patients with MFS were included in this study. Preoperative MRI images were subsequently measured after marker implantation and imported into the MIMICS software for the 3-D reconstruction of a virtual model of an eyeball and a marker. The virtual eyeball model was designed according to the degree of retinoschisis, which was measured using optical coherence tomography preoperatively. A macular buckle was designed using a titanium stent, assisted by 3-D printing; furthermore, it was surgically placed in combination with pars plana vitrectomy. Visual acuity, axial length and anatomic outcomes were analysed pre- and postoperatively.

RESULTS

Macular schisis in all patients was completely resolved after the surgery without any postoperative complications. The mean postoperative best corrected visual acuity (LogMAR) improved significantly from 1.21 to 0.92 during the 6-month follow-up period (p < 0.001) and reached 0.9 (p < 0.001) after 2 years. The axial length was significantly shortened during the 2 years postoperatively follow-up period (p < 0.01). The average axial lengths in all patients decreased from 30.62 mm preoperatively to 29.81 mm 1 month postoperatively and remained around 30.16 mm from 1 year after the surgery.

CONCLUSION

The 3-D printing technique is useful to predict the indentation height and position of the macular buckle. The 3D-printing-assisted macular buckle, in combination with vitrectomy, is an effective, safe and accurate treatment modality for MFS.

Auricular reconstruction: where are we now? A critical literature review

PURPOSE

Deformities of the external ear can affect psychosocial well-being and hearing. Current gold-standard reconstructive treatment is autologous costal cartilage grafting despite the vast morbidity profile. Tissue engineering using stem cells and 3D printing can create patient-specific reconstructed auricles with superior cosmetic outcomes and reduced morbidity. This review critically analyses recent and breakthrough research in the field of regenerative medicine for the pinna, considering gaps in current literature and suggesting further steps to identify whether this could be the new gold-standard.

METHODS

A literature review was conducted. PubMed (MEDLINE) and Cochrane databases were searched using key terms regenerative medicine, tissue engineering, 3D printing, biofabrication, auricular reconstruction, auricular cartilage, chondrocyte, outer ear and pinna. Studies in which tissue-engineered auricles were implanted into animal or human subjects were included. Exclusion criteria included articles not in English and not published within the last ten years. Titles, abstracts and full texts were screened. Reference searching was conducted and significant breakthrough studies included.

RESULTS

8 studies, 6 animal and 2 human, were selected for inclusion. Strengths and weaknesses of each are discussed. Common limitations include a lack of human studies, small sample sizes and short follow-up times.

CONCLUSION

Regenerative medicine holds significant potential to improve auricular reconstruction. To date there are no large multi-centred human studies in which tissue-engineered auricles have been implanted. However, recent human studies suggest promising results, raising the ever-growing possibility that tissue engineering is the future of auricular reconstruction. We aim to continue developing knowledge in this field.

Hybrid Three-Dimensional-Printed Ear Tissue Scaffold With Autologous Cartilage Mitigates Soft Tissue Complications

OBJECTIVES/HYPOTHESIS

To analyze the use of highly translatable three-dimensional (3D)-printed auricular scaffolds with and without novel cartilage tissue inserts in a rodent model.

STUDY DESIGN

Preclinical rodent animal model.

METHODS

This prospective study assessed a single-stage 3D-printed auricular bioscaffold with or without porcine cartilage tissue inserts in an athymic rodent model. Digital Imaging and Communications in Medicine computed tomography images of a human auricle were segmented to create an external anatomic envelope filled with orthogonally interconnected spherical pores. Scaffolds with and without tissue inset sites were 3D printed by laser sintering bioresorbable polycaprolactone, then implanted subcutaneously in five rats for each group.

RESULTS

Ten athymic rats were studied to a goal of 24 weeks postoperatively. Precise anatomic similarity and scaffold integrity were maintained in both scaffold conditions throughout experimentation with grossly visible tissue ingrowth and angiogenesis upon explantation. Cartilage-seeded scaffolds had relatively lower rates of nonsurgical site complications compared to unseeded scaffolds with relatively increased surgical site ulceration, though neither met statistical significance. Histology revealed robust soft tissue infiltration and vascularization in both seeded and unseeded scaffolds, and demonstrated impressive maintenance of viable cartilage in cartilage-seeded scaffolds. Radiology confirmed soft tissue infiltration in all scaffolds, and biomechanical modeling suggested amelioration of stress in scaffolds implanted with cartilage.

CONCLUSIONS

A hybrid approach incorporating cartilage insets into 3D-printed bioscaffolds suggests enhanced clinical and histological outcomes. These data demonstrate the potential to integrate point-of-care tissue engineering techniques into 3D printing to generate alternatives to current reconstructive surgery techniques and avoid the demands of traditional tissue engineering.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1008-1015, 2021.

Review of Plastic Surgery Biomaterials and Current Progress in Their 3D Manufacturing Technology

Plastic surgery is a broad field, including maxillofacial surgery, skin flaps and grafts, liposuction and body contouring, breast surgery, and facial cosmetic procedures. Due to the requirements of plastic surgery for the biological safety of materials, biomaterials are widely used because of its superior biocompatibility and biodegradability. Currently, there are many kinds of biomaterials clinically used in plastic surgery and their applications are diverse. Moreover, with the rise of three-dimensional printing technology in recent years, the macroscopically more precise and personalized bio-scaffolding materials with microporous structure have made good progress, which is thought to bring new development to biomaterials. Therefore, in this paper, we reviewed the plastic surgery biomaterials and current progress in their 3D manufacturing technology.

The Effect of Perichondrium on Biological and Biomechanical Properties of Molded Diced Cartilage Grafts

BACKGROUND

Diced cartilage is a significant alternative approach to cartilage grafting. However, the viability and biomechanical properties of diced cartilage grafts remain to be improved, and the role of perichondrium is largely neglected. This study aimed to evaluate the histological and biomechanical effects of perichondrium on custom-shaped diced cartilage grafts constructed via a high-density porous polyethylene mold.

METHODS

Seven New Zealand rabbits were used. Unilateral auricular cartilage was harvested and divided into 2 parts, with or without perichondrium, diced into 1 × 1 × 0.5 mm cubical pieces, and filled into high-density porous polyethylene molds. Three grafts with the perichondrium removed and 3 with the perichondrium preserved were implanted subcutaneously at the dorsum. The grafts underwent biomechanical and histological tests 4, 8, and 12 weeks after the implantation.

RESULTS

The diced cartilage merged into integrated blocks without observable resorption in both groups at each time point. Additionally, the retention rate of weight was higher in the perichondrium-preserved group (P < 0.05). We observed regenerated cartilage that stained positively for type II collagen and glial fibrillary acidic protein (GFAP). A greater area of regenerated cartilage and higher scores of GFAP staining were observed in the perichondrium-preserved group (P < 0.05). The yield stress and modulus of elasticity were also higher in the perichondrium-preserved grafts from week 8 after implantation (P < 0.05).

CONCLUSIONS

Diced cartilage grafts with a custom shape can be constructed using a high-density porous polyethylene mold. The preservation of perichondrium can improve graft viability and biomechanical properties.

LEVEL OF EVIDENCE

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266.

Advances in bioprinting using additive manufacturing

Since its conception in the 1980's, several advances in the field of additive manufacturing have led to exploration of alternate as well as combination biomaterials. These progresses have directed the use of 3D printing in wider applications such as printing of dermal layers, cartilage, bone defects, and surgical implants. Furthermore, the incorporation of live and functional cells with or atop biomaterials has laid the foundation for its use in tissue engineering. The purpose of this review is to summarize the advances in 3D printing and bioprinting of several types of tissues such as skin, cartilage, bones, and cardiac valves. This review will address the current 3D technologies used in tissue construction and study the biomaterials being investigated. There are several requirements that need to be addressed, in order to reconstruct functional tissue such as mechanical strength, porosity of the replicate and cellular incorporation. Researchers have focused their studies to answer questions regarding these requirements.