Man as living bioreactor: Fate of an exogenously prepared customized tissue-engineered mandible☆

Hypoxia as a stimulus for tissue formation: The concept of organogenesis in microsurgically vascularized tissue engineering constructs

Axial vascularization of tissue constructs is essential to maintain an adequate blood supply for a stable regeneration of a clinically relevant tissue size. The versatility of the arterio-venous loop (AVL) has been previously shown in various small and large animal models as well as in clinical reports for bone regeneration. We have previously demonstrated the capability of the AVL to induce axial vascularization and to support the nourishment of tissue constructs in small animal models after applying high doses of ionizing radiation comparable to those applied for adjuvant radiotherapy after head and neck cancer. We hypothesize that this robust ability to induce regeneration after irradiation could be related to a state of hypoxia inside the constructs that triggers the HIF1 (hypoxia induced factor 1) - SDF1 (stromal derived factor 1) axis leading to chemotaxis of progenitor cells and induction of tissue regeneration and vascularization. We analyzed the expression of HIF1 and SDF1 via immunofluorescence in axially vascularized bone tissue engineering constructs in Lewis rats 2 and 5 weeks after local irradiation with 9Gy or 15Gy. We also analyzed the expression of various genes for osteogenic differentiation (collagen 1, RUNX, alkaline phosphatase and osteonectin) via real time PCR analysis. The expression of HIF1 and SDF1 was enhanced two weeks after irradiation with 15Gy in comparison to non-irradiated constructs. The expression of osteogenic markers was enhanced at the 5-weeks time point with significant results regarding collagen, alkaline phosphatase and osteonectin. These results indicate that the hypoxia within the AVL constructs together with an enhanced SDF1 expression probably play a role in promoting tissue differentiation. The process of tissue generation triggered by hypoxia in the vicinity of a definite vascular axis with enhanced tissue differentiation over time resembles hereby the well-known concept of organogenesis in fetal life.

Hybrid Implants Based on Calcium-Magnesium Silicate Ceramic Diopside as a Carrier of Recombinant BMP-2 and Demineralized Bone Matrix as a Scaffold: Ectopic Osteogenesis in Intramuscular Implantation in Mice

High efficiency of hybrid implants based on calcium-magnesium silicate ceramic, diopside, as a carrier of recombinant BMP-2 and xenogenic demineralized bone matrix (DBM) as a scaffold for bone tissue regeneration was demonstrated previously using the model of critical size cranial defects in mice. In order to investigate the possibility of using these implants for growing autologous bone tissue using in vivo bioreactor principle in the patient's own body, effectiveness of ectopic osteogenesis induced by them in intramuscular implantation in mice was studied. At the dose of 7 μg of BMP-2 per implant, dense agglomeration of cells, probably skeletal muscle satellite precursor cells, was observed one week after implantation with areas of intense chondrogenesis, initial stage of indirect osteogenesis, around the implants. After 12 weeks, a dense bone capsule of trabecular structure was formed covered with periosteum and mature bone marrow located in the spaces between the trabeculae. The capsule volume was about 8-10 times the volume of the original implant. There were practically no signs of inflammation and foreign body reaction. Microcomputed tomography data showed significant increase of the relative bone volume, number of trabeculae, and bone tissue density in the group of mice with BMP-2-containing implant in comparison with the group without BMP-2. Considering that DBM can be obtained in practically unlimited quantities with required size and shape, and that BMP-2 is obtained by synthesis in E. coli cells and is relatively inexpensive, further development of the in vivo bioreactor model based on the hybrid implants constructed from BMP-2, diopside, and xenogenic DBM seems promising.

Revascularization and angiogenesis for bone bioengineering in the craniofacial region: a review

The revascularization of grafted tissues is a complicated and non-straightforward process, which makes it challenging to perform reconstructive surgery for critical-sized bone defects. This challenge is combined with the low vascularity that results from radiotherapy. This low vascularity could result from ischemia-reperfusion injuries, also known as ischemia which may happen upon grafting. Ischemia may affect the hard tissue during reconstruction, and this can often cause resorption, infections, disfigurement, and malunion. This paper therefore reviews the clinical and experimental application of procedures that were employed to improve the reconstructive surgery process, which would ensure that the vascularity of the tissue is maintained or enhanced. It also presents the key strategies that are implemented to perform tissue engineering within the grafted sites aiming to optimize the microenvironment and to enhance the overall process of neovascularization and angiogenesis. This review reveals that the current strategies, according to the literature, are the seeding of the mature and progenitor cells, use of extracellular matrix (ECM), co-culturing of osteoblasts with the ECM, growth factors and the use of microcapillaries incorporated into the scaffold design. However, due to the unstable and regression-prone capillary structures in bone constructs, further research focusing on creating long-lasting and stable blood vessels is required.

Advances in In Vitro and In Vivo Bioreactor-Based Bone Generation for Craniofacial Tissue Engineering

Craniofacial reconstruction requires robust bone of specified geometry for the repair to be both functional and aesthetic. While native bone from elsewhere in the body can be harvested, shaped, and implanted within a defect, using either an in vitro or in vivo bioreactors eliminates donor site morbidity while increasing the customizability of the generated tissue. In vitro bioreactors utilize cells harvested from the patient, a scaffold, and a device to increase mass transfer of nutrients, oxygen, and waste, allowing for generation of larger viable tissues. In vivo bioreactors utilize the patient's own body as a source of cells and of nutrient transfer and involve the implantation of a scaffold with or without growth factors adjacent to vasculature, followed by the eventual transfer of vascularized, mineralized tissue to the defect site. Several different models of in vitro bioreactors exist, and several different implantation sites have been successfully utilized for in vivo tissue generation and defect repair in humans. In this review, we discuss the specifics of each bioreactor strategy, as well as the advantages and disadvantages of each and the future directions for the engineering of bony tissues for craniofacial defect repair.

Biomedical applications of three-dimensional bioprinted craniofacial tissue engineering

Anatomical complications of the craniofacial regions often present considerable challenges to the surgical repair or replacement of the damaged tissues. Surgical repair has its own set of limitations, including scarcity of the donor tissues, immune rejection, use of immune suppressors followed by the surgery, and restriction in restoring the natural aesthetic appeal. Rapid advancement in the field of biomaterials, cell biology, and engineering has helped scientists to create cellularized skeletal muscle-like structures. However, the existing method still has limitations in building large, highly vascular tissue with clinical application. With the advance in the three-dimensional (3D) bioprinting technique, scientists and clinicians now can produce the functional implants of skeletal muscles and bones that are more patient-specific with the perfect match to the architecture of their craniofacial defects. Craniofacial tissue regeneration using 3D bioprinting can manage and eliminate the restrictions of the surgical transplant from the donor site. The concept of creating the new functional tissue, exactly mimicking the anatomical and physiological function of the damaged tissue, looks highly attractive. This is crucial to reduce the donor site morbidity and retain the esthetics. 3D bioprinting can integrate all three essential components of tissue engineering, that is, rehabilitation, reconstruction, and regeneration of the lost craniofacial tissues. Such integration essentially helps to develop the patient-specific treatment plans and damage site-driven creation of the functional implants for the craniofacial defects. This article is the bird's eye view on the latest development and application of 3D bioprinting in the regeneration of the skeletal muscle tissues and their application in restoring the functional abilities of the damaged craniofacial tissue. We also discussed current challenges in craniofacial bone vascularization and gave our view on the future direction, including establishing the interactions between tissue-engineered skeletal muscle and the peripheral nervous system.

In vivo prevascularization strategy enhances neovascularization of β-tricalcium phosphate scaffolds in bone regeneration

Background

Neovascularization is critical for bone regeneration. Numerous studies have explored prevascularization preimplant strategies, ranging from calcium phosphate cement (CPC) scaffolds to co-culturing CPCs with stem cells. The aim of the present study was to evaluate an alternative in vivo prevascularization approach, using preimplant-prepared macroporous beta-tricalcium phosphate (β-TCP) scaffolds and subsequent transplantation in bone defect model.

Methods

The morphology of β-TCPs was characterized by scanning electron microscopy. After 3 weeks of prevascularization within a muscle pouch at the lateral size of rat tibia, we transplanted prevascularized macroporous β-TCPs in segmental tibia defects, using blank β-TCPs as a control. Extent of neovascularization was determined by angiography and immunohistochemical (IHC) evaluations. Tibia samples were collected at different time points for biomechanical, radiological, and histological analyses. RT-PCR and western blotting were used to evaluate angio- and osteo-specific markers.

Results

With macroporous β-TCPs, we documented more vascular and supporting tissue invasion in the macroporous β-TCPs with prior in vivo prevascularization. Radiography, biomechanical, IHC, and histological analyses revealed considerably more vascularity and bone consolidation in β-TCP scaffolds that had undergone the prevascularization step compared to the blank β-TCP scaffolds. Moreover, the prevascularization treatment remarkably upregulated mRNA and protein expression of BMP2 and vascular endothelial growth factor (VEGF) during bone regeneration.

Conclusion

This novel in vivo prevascularization strategy successfully accelerated vascular formation to bone regeneration. Our findings indicate that prevascularized tissue-engineered bone grafts have promising potential in clinical applications.

The translational potential of this article

This study indicates a novel in vivo prevascularization strategy for growing vasculature on β-TCP scaffolds to be used for repair of large segmental bone defects, might serve as a promising tissue-engineered bone grafts in the future.

Sustained local ionic homeostatic imbalance caused by calcification modulates inflammation to trigger heterotopic ossification

Heterotopic ossification (HO) is a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues. Despite being a frequent complication of orthopedic and trauma surgery, brain and spinal injury, the etiology of HO is poorly understood. The aim of this study is to evaluate the hypothesis that a sustained local ionic homeostatic imbalance (SLIHI) created by mineral formation during tissue calcification modulates inflammation to trigger HO. This evaluation also considers the role SLIHI could play for the design of cell-free, drug-free osteoinductive bone graft substitutes. The evaluation contains five main sections. The first section defines relevant concepts in the context of HO and provides a summary of proposed causes of HO. The second section starts with a detailed analysis of the occurrence and involvement of calcification in HO. It is followed by an explanation of the causes of calcification and its consequences. This allows to speculate on the potential chemical modulators of inflammation and triggers of HO. The end of this second section is devoted to in vitro mineralization tests used to predict the ectopic potential of materials. The third section reviews the biological cascade of events occurring during pathological and material-induced HO, and attempts to propose a quantitative timeline of HO formation. The fourth section looks at potential ways to control HO formation, either acting on SLIHI or on inflammation. Chemical, physical, and drug-based approaches are considered. Finally, the evaluation finishes with a critical assessment of the definition of osteoinduction. STATEMENT OF SIGNIFICANCE: The ability to regenerate bone in a spatially controlled and reproducible manner is an essential prerequisite for the treatment of large bone defects. As such, understanding the mechanism leading to heterotopic ossification (HO), a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues, would be very useful. Unfortunately, the mechanism(s) behind HO is(are) poorly understood. The present study reviews the literature on HO and based on it, proposes that HO can be caused by a combination of inflammation and calcification. This mechanism helps to better understand current strategies to prevent and treat HO. It also shows new opportunities to improve the treatment of bone defects in orthopedic and dental procedures.

Prefabricated 3D-Printed Tissue-Engineered Bone for Mandibular Reconstruction: A Preclinical Translational Study in Primate

The advent of three dimensionally (3D) printed customized bone grafts using different biomaterials has enabled repairs of complex bone defects in various in vivo models. However, studies related to their clinical translations are truly limited. Herein, 3D printed poly(lactic-co-glycolic acid)/β-tricalcium phosphate (PLGA/TCP) and TCP scaffolds with or without recombinant bone morphogenetic protein −2 (rhBMP-2) coating were utilized to repair primate’s large-volume mandibular defects and compared efficacy of prefabricated tissue-engineered bone (PTEB) over direct implantation (without prefabrication). ¹⁸F-FDG PET/CT was explored for real-time monitoring of bone regeneration and vascularization. After 3-month’s prefabrication, the original 3D-architecture of the PLGA/TCP-BMP scaffold was found to be completely lost, while it was properly maintained in TCP-BMP scaffolds. Besides, there was a remarkable decrease in the PLGA/TCP-BMP scaffold density and increase in TCP-BMP scaffolds density during ectopic (within latissimus dorsi muscle) and orthotopic (within mandibular defect) implantation, indicating regular bone formation with TCP-BMP scaffolds. Notably, PTEB based on TCP-BMP scaffold was successfully fabricated with pronounced effects on bone regeneration and vascularization based on radiographic, ¹⁸F-FDG PET/CT, and histological evaluation, suggesting a promising approach toward clinical translation.

Skeletal regeneration for segmental bone loss: Vascularised grafts, analogues and surrogates

Massive segmental bone defects (SBD) are mostly treated by removing the fibula and transplanting it complete with blood supply. While revolutionary 50 years ago, this remains the standard treatment. This review considers different strategies to repair SBD and emerging potential replacements for this highly invasive procedure. Prior to the technical breakthrough of microsurgery, researchers in the 1960s and 1970s had begun to make considerable progress in developing non autologous routes to repairing SBD. While the breaktthrough of vascularised bone transplantation solved the immediate problem of a lack of reliable repair strategies, much of their prior work is still relevant today. We challenge the assumption that mimicry is necessary or likely to be successful and instead point to the utility of quite crude (from a materials technology perspective), approaches. Together there are quite compelling indications that the body can regenerate entire bone segments with few or no exogenous factors. This is important, as there is a limit to how expensive a bone repair can be and still be widely available to all patients since cost restraints within healthcare systems are not likely to diminish in the near future. STATEMENT OF SIGNIFICANCE: This review is significant because it is a multidisciplinary view of several surgeons and scientists as to what is driving improvement in segmental bone defect repair, why many approaches to date have not succeeded and why some quite basic approaches can be as effective as they are. While there are many reviews of the literature of grafting and bone repair the relative lack of substantial improvement and slow rate of progress in clinical translation is often overlooked and we seek to challenge the reader to consider the issue more broadly.

Personalized medicine for reconstruction of critical-size bone defects - a translational approach with customizable vascularized bone tissue

Tissue engineering principles allow the generation of functional tissues for biomedical applications. Reconstruction of large-scale bone defects with tissue-engineered bone has still not entered the clinical routine. In the present study, a bone substitute in combination with mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC) with or without growth factors BMP-2 and VEGF-A was prevascularized by an arteriovenous (AV) loop and transplanted into a critical-size tibia defect in the sheep model. With 3D imaging and immunohistochemistry, we could show that this approach is a feasible and simple alternative to the current clinical therapeutic option. This study serves as proof of concept for using large-scale transplantable, vascularized, and customizable bone, generated in a living organism for the reconstruction of load-bearing bone defects, individually tailored to the patient's needs. With this approach in personalized medicine for the reconstruction of critical-size bone defects, regeneration of parts of the human body will become possible in the near future.

Investigation of a Prevascularized Bone Graft for Large Defects in the Ovine Tibia

In vivo bioreactors are a promising approach for engineering vascularized autologous bone grafts to repair large bone defects. In this pilot parametric study, we first developed a three-dimensional (3D) printed scaffold uniquely designed to accommodate inclusion of a vascular bundle and facilitate growth factor delivery for accelerated vascular invasion and ectopic bone formation. Second, we established a new sheep deep circumflex iliac artery (DCIA) model as an in vivo bioreactor for engineering a vascularized bone graft and evaluated the effect of implantation duration on ectopic bone formation. Third, after 8 weeks of implantation around the DCIA, we transplanted the prevascularized bone graft to a 5 cm segmental bone defect in the sheep tibia, using the custom 3D printed bone morphogenic protein 2 (BMP-2) loaded scaffold without prior in vivo bioreactor maturation as a control. Analysis by micro-computed tomography and histomorphometry found ectopic bone formation in BMP-2 loaded scaffolds implanted for 8 and 12 weeks in the iliac pouch, with greater bone formation occurring after 12 weeks. Grafts transplanted to the tibial defect supported bone growth, mainly on the periphery of the graft, but greater bone growth and less soft tissue invasion was observed in the avascular BMP-2 loaded scaffold implanted directly into the tibia without prior in vivo maturation. Histopathological evaluation noted considerably greater vascularity in the bone grafts that underwent in vivo maturation with an inserted vascular bundle compared with the avascular BMP-2 loaded graft. Our findings indicate that the use of an initial DCIA in vivo bioreactor maturation step is a promising approach to developing vascularized autologous bone grafts, although scaffolds with greater osteoinductivity should be further studied. Impact statement This translational pilot study aims at combining a tissue engineering scaffold strategy, in vivo prevascularization, and a modified transplantation technique to accelerate large segmental bone defect repair. First, we three-dimensional (3D) printed a 5 cm scaffold with a unique design to facilitate vascular bundle inclusion and osteoinductive growth factor delivery. Second, we established a new sheep deep circumflex iliac artery model as an in vivo bioreactor for prevascularizing the novel 3D printed osteoinductive scaffold. Subsequently, we transplanted the prevascularized bone graft to a clinically relevant 5 cm segmental bone defect in the sheep tibia for bone regeneration.

Bioengineering for head and neck reconstruction: the role of customized flaps

PURPOSE OF REVIEW

The purpose of this review is to provide the reader with an overview of the present and future applications of bioengineering for head and neck reconstruction, ranging from the application of Computed Assisted Surgery (CAS) to the most recent advances in 3D printing and tissue engineering.

RECENT FINDINGS

The use of CAS in head and neck reconstruction has been demonstrated to provide shorter surgical times, improved reconstructive accuracy of bone reconstruction, and achieves better alignment of bone segments in osteotomized reconstructions. Beyond its classical application in bone reconstructions, CAS has demonstrated reliability in the planning and harvesting of soft tissue flaps. To date, literature regarding bioengineering for head and neck reconstruction is mainly focused on in-vitro and animal model experiments; however, some pioneering reports on human patients suggest the potential feasibility of this technology.

SUMMARY

Bioengineering is anticipated to play a key role in the future development of customized flaps for head and neck reconstruction. These technologies are particularly appealing as a new technology to address certain unsolved challenges in head and neck reconstruction.

Strategies for re-vascularization and promotion of angiogenesis in trauma and disease

The maintenance of a healthy vascular system is essential to ensure the proper function of all organs of the human body. While macrovessels have the main role of blood transportation from the heart to all tissues, microvessels, in particular capillaries, are responsible for maintaining tissues' functionality by providing oxygen, nutrients and waste exchanges. Occlusion of blood vessels due to atherosclerotic plaque accumulation remains the leading cause of mortality across the world. Autologous vein and artery grafts bypassing are the current gold standard surgical procedures to substitute primarily obstructed vascular structures. Ischemic scenarios that condition blood supply in downstream tissues may arise from blockage phenomena, as well as from other disease or events leading to trauma. The (i) great demand for new vascular substitutes, arising from both the limited availability of healthy autologous vessels, as well as the shortcomings associated with small-diameter synthetic vascular grafts, and (ii) the challenging induction of the formation of adequate and stable microvasculature are current driving forces for the growing interest in the development of bioinspired strategies to ensure the proper function of vasculature in all its dimensional scales. Here, a critical review of well-established technologies and recent biotechnological advances to substitute or regenerate the vascular system is provided.

In situ production of pre-vascularized synthetic bone grafts for regenerating critical-sized defects in rabbits

Reconstructing large bone defects caused by severe trauma or resection of tumors remains a challenge for surgeons. A fibula free flap and its vascularized bed can be transplanted to the reconstruction site to achieve healing. However, this technique adds morbidity, and requires microsurgery and sculpting of the bone tissue to adapt the graft to both the vasculature and the anatomy of the defect. The aim of the current study was to evaluate an alternative approach consisting of the in situ production of a pre-vascularized synthetic bone graft and its subsequent transplantation to a critical-sized bone defect. 3D printed chambers containing biphasic calcium phosphate (BCP) granules, perfused by a local vascular pedicle, with or without the addition of stromal vascular fraction (SVF), were subcutaneously implanted into New Zealand White female rabbits. SVF was prepared extemporaneously from autologous adipose tissue, the vascular pedicle was isolated from the inguinal site, while BCP granules alone served as a control group. After 8 weeks, the constructs containing a vascular pedicle exhibited abundant neovascularization with blood vessels sprouting from the pedicle, leading to significantly increased vascularization compared to BCP controls. Pre-vascularized synthetic bone grafts were then transplanted into 15 mm critical-sized segmental ulnar defects for a further 8 weeks. Micro-CT and decalcified histology revealed that pre-vascularization of synthetic bone grafts led to enhanced bone regeneration. This pre-clinical study demonstrates the feasibility and efficacy of the in situ production of pre-vascularized synthetic bone grafts for regenerating large bone defects, thereby addressing an important clinical need. STATEMENT OF SIGNIFICANCE: The current gold standard in large bone defect regeneration is vascularized fibula grafting. An alternative approach consisting of in situ production of a pre-vascularized synthetic bone graft and its subsequent transplantation to a bone defect is presented here. 3D printed chambers were filled with biphasic calcium phosphate granules, supplemented with autologous stromal vascular fraction and an axial vascular pedicle and subcutaneously implanted in inguinal sites. These pre-vascularized synthetic grafts were then transplanted into critical-sized segmental ulnar defects. Micro-CT and decalcified histology revealed that the pre-vascularized synthetic bone grafts led to higher bone regeneration than non-vascularized constructs. An alternative to vascularized fibula grafting is provided and may address an important clinical need for large bone defect reconstruction.

Innovations and Future Directions in Head and Neck Microsurgical Reconstruction

Head and neck reconstructive microsurgery is constantly innovating because of a combination of multidisciplinary advances. This article examines recent innovations that have affected the field as well as presenting research leading to future advancement. Innovations include the use of virtual surgical planning and three-dimensional printing in craniofacial reconstruction, advances in intraoperative navigation and imaging, as well as postoperative monitoring, development of minimally invasive reconstructive microsurgery techniques, integration of regenerative medicine and stem cell biology with reconstruction, and the dramatic advancement of face transplant.

Application of additive manufacturing in customized titanium mandibular implants for patients with oral tumors

The application of additive manufacturing (AM) technology has been widely used in various medical fields, including craniomaxillofacial surgery. The aim of the present study was to examine the surgical efficiency and post-operative outcomes of patient-specific titanium mandibular reconstruction using AM. Major steps in directly designing and manufacturing 3D customized titanium implants are discussed. Furthermore, pre-operative preparations, surgical procedures and post-operative treatment outcomes were compared among patients who received mandibular reconstruction using a customized 3D titanium implant, titanium reconstruction plates or vascularized autologous fibular grafting. Use of a customized titanium implant significantly improved surgical efficiency and precision. When compared with mandibular reconstruction using the two conventional approaches, patients who received the customized implant were significantly more satisfied with their facial appearance, and exhibited minimal post-operative complications in the 12-month follow-up period. Patients who underwent mandibular reconstruction using a customized titanium implant displayed improved mandibular contour symmetry, restored occlusal function, normal range of mouth opening and no temporomandibular joint related pain; all complications frequently experienced by patients who undergo conventional approaches of mandibular reconstruction.

Regeneration of segmental defects in metatarsus of sheep with vascularized and customized 3D-printed calcium phosphate scaffolds

Although autografts are considered to be the gold standard treatment for reconstruction of large bone defects resulting from trauma or diseases, donor site morbidity and limited availability restrict their use. Successful bone repair also depends on sufficient vascularization and to address this challenge, novel strategies focus on the development of vascularized biomaterial scaffolds. This pilot study aimed to investigate the feasibility of regenerating large bone defects in sheep using 3D-printed customized calcium phosphate scaffolds with or without surgical vascularization. Pre-operative computed tomography scans were performed to visualize the metatarsus and vasculature and to fabricate customized scaffolds and surgical guides by 3D printing. Critical-sized segmental defects created in the mid-diaphyseal region of the metatarsus were either left empty or treated with the 3D scaffold alone or in combination with an axial vascular pedicle. Bone regeneration was evaluated 1, 2 and 3 months post-implantation. After 3 months, the untreated defect remained non-bridged while the 3D scaffold guided bone regeneration. The presence of the vascular pedicle further enhanced bone formation. Histology confirmed bone growth inside the porous 3D scaffolds with or without vascular pedicle inclusion. Taken together, this pilot study demonstrated the feasibility of precised pre-surgical planning and reconstruction of large bone defects with 3D-printed personalized scaffolds.

Promising Scaffold-Free Approaches in Translational Dentistry

Regenerative medicine has recently improved the principal therapies in several medical fields. In the past ten years, the continuous search for novel approaches to treat the most common dental pathologies has developed a new branch called regenerative dentistry. The main research fields of translational dentistry involve biomimetic materials, orally derived stem cells, and tissue engineering to populate scaffolds with autologous stem cells and bioactive growth factors. The scientific literature has reported two main research trends in regenerative dentistry: scaffold-based and scaffold-free approaches. This article aims to critically review the main biological properties of scaffold-free regenerative procedures in dentistry. The most impactful pros and cons of the exosomes, the leading role of hypoxia-based mesenchymal stem cells (MSCs), and the strategic use of heat shock proteins in regenerative dentistry will be highlighted and discussed in terms of the use of such tools in dental regeneration and repair.

Segmental Mandibular Reconstruction Using Tissue Engineering Strategies: A Systematic Review of Individual Patient Data

Objective

The aim of the systematic review was to analyze the current clinical evidence concerning the use of tissue engineering as a treatment strategy for reconstruction of segmental defects of the mandible and their clinical outcomes using individual patient data.

Methods

A systematic review of the literature was conducted using PubMed and Cochrane Library on May 21, 2019. The eligibility criteria included patients in whom segmental mandibular reconstruction was carried out using tissue engineering as the primary treatment strategy. After screening and checking for eligibility, individual patient data were extracted to the extent it was available. Data extraction included the type of tissue engineering strategy, demographics, and indication for treatment, and outcomes included clinical and radiographic outcome measures, vitality of engineered bone, dental rehabilitation, and patient-reported outcome measures and complications.

Results

Out of a total of 408 articles identified, 44 articles reporting on 285 patients were included, of which 179 patients fulfilled the inclusion criteria. The different tissue engineering treatment strategies could be broadly classified into 5 groups: "prefabrication," "cell culture," "bone morphogenetic protein (BMP) without autografts," "BMP with autografts," and "scaffolds containing autografts." Most included studies were case reports or case series. A wide variety of components were used as scaffolds, cells, and biological substances. There was not a single outcome measure that was both objective and consistently reported, although most studies reported successful outcome.

Discussion

A wide variety of tissue engineering strategies were used for segmental mandibular reconstruction that could be classified into 5 groups. Due to the low number of treated patients, lack of standardized and consistent reporting outcomes, lack of comparative studies, and low evidence of reported literature, there is insufficient evidence to recommend any particular tissue engineering strategy.

Management of Endodontic and Periodontal Lesions: the Role of Regenerative Dentistry and Biomaterials

Regenerative dentistry represents a novel interdisciplinary approach involving biomaterials, several molecules and mesenchymal stem cells (MSCs), preferably derived from oral tissues. The pivotal role of MSCs depends on the fact that they can differentiate into different cell lineages and have the strategic role to release bioactive substances that stimulate the renewal and regeneration of damaged tissues. The role of regenerative dentistry is promising in all the branches of dentistry: the most intriguing application is related to the management of endodontic and periodontal defects, overcoming the surgical approach and the implantology as a consequence of a poorly efficient therapeutic plan.

The use of muscle extracellular matrix (MEM) and SCPC bioceramic for bone augmentation

BACKGROUND

Bone augmentation is a challenging problem in the field of maxillofacial surgery.

OBJECTIVE

In this study, we prepared and evaluated muscle extracellular matrix (MEM) after adding silica calcium phosphate composite (SCPC) seeded with human bone marrow mesenchymal cells (hBMSCs). We then investigated bone augmentation in vivo using the prepared MEM-SCPC.

MATERIALS AND METHODS

hBMSCs were seeded on MEM-SCPC, and MEM was characterized. Calvarial bone grafts were prepared using nude mice (n = 12) and grafted separately in two experimental groups: grafts with MEM (control, n = 4) and grafts with MEM-SCPC-hBMSCs (experimental group, n = 8) for 8 weeks. Micro-computed tomography (micro-CT) and histological analysis were then performed.

RESULTS

Micro-CT analysis demonstrated a thinner trabeculae in grafted defects than normal native bone, with a high degree of anisotropy. Quantitative histomorphometric assessment showed a higher median bone percentage surface area of 80.2% ± 6.0% in the experimental group.

CONCLUSION

The enhanced bone formation and maturation of bone grafted with MEM-SCPC-hBMSCs suggested the potential use of this material for bone augmentation.

Reconstruction of a Mandibular Defect with Toronto Bridge Following Tumor Resection and Bone Graft: A Case Report

Dental implants are highly recommended to improve the retention, stability, and support of prostheses in edentulous patients with large surgical defects. Depending on the size of the defect, a bone graft procedure might be necessary. However, due to limitations of bone grafts, some complications might negatively affect the prosthetic rehabilitation of the patient. This case report presents some of these prosthetic problems following surgical resection and autogenous bone graft procedures.

Reconstruction of segmental mandibular defects: Current procedures and perspectives

Background

The reconstruction of segmental mandibular defects remains a challenge for the reconstructive surgeon, from both a functional and an esthetic point of view.

Methods

This clinical review examines the different techniques currently in use for mandibular reconstruction as related to a range of etiologies, including the different bone donor sites, the alternatives to free flaps (FFs), as well as the contribution of computer‐assisted surgery. Recent progress and the perspectives in bone tissue engineering (BTE) are also discussed.

Results

Osseous FF allows reliable and satisfying outcomes. However, locoregional flap, distraction osteogenesis, or even induced membrane techniques are other potential options in less favorable cases. Obtaining an engineered bone with satisfactory mechanical properties and sufficient vascular supply requires further investigations.

Conclusions

Osseous FF procedure remains the gold standard for segmental mandible reconstruction. BTE strategies offer promising alternatives.

Mandibular reconstruction with autogenous non-vascularised bone graft

Background

Reconstruction of mandibular defects can be challenging because an acceptable aesthetic and functional outcome must be achieved simultaneously.

Aim

To evaluate the pattern of mandibulectomy and reconstruction materials used in the reconstruction of mandibular defects.

Materials and methods

This was a retrospective study of mandibulectomies with reconstruction in Sokoto, Nigeria between 2012 and 2016. Data such as demographics, type of tumour, type of resection and type of reconstruction materials used were extracted and stored.

Results

Fifty-two cases of mandibulectomies were done comprising 24 males and 28 females (ratio 1:1.2). Age ranged 5–80 years with mean±SD (37.8±15). Most of the cases 30 (57.7%) were on the right. There are 35 (67.3%) benign and 17 (32.7%) malignant cases. Thirty (57.7%) lateral, 16 (30.8%) condylar, 1 (1.9%) central and 5 (9.6%) combined mandibular defects were seen. Reconstruction plate alone was used in 11 (21.2%) cases, reconstruction plate with rib and tibia grafts in 16 (30.8%) cases, reconstruction plate with Iliac crest and tibia grafts in 15 (28.8%) cases. Graft length ranged from 0–20cm. There was satisfactory outcome altogether in 32 (80.0%).

Conclusion

This study has shown the types of mandibulectomies and reconstruction materials used in our centre.

Scaffold implantation in the omentum majus of rabbits for new bone formation

Restoration of the mandible after defects caused by ablative surgery remains challenging. Microvascular free flaps from the scapula, fibula or iliac crest remain the 'gold standard'. A drawback of these methods is donor-side morbidity, availability and the shape of the bone. Former cases have shown that prefabrication of a customized bone flap in the latissimus dorsi muscle may be successful; however, this method is still associated with high donor-side morbidity. Osteogenesis in the omentum majus of rabbits by wrapping the periosteum into it was confirmed recently and is particularly interesting for bone endocultivation. Twelve adult male New Zealand white rabbits were used. In each, two hydroxyapatite blocks were implanted in the greater omentum with autologous bone or autologous bone + rhBMP-2. Bone density measurements were performed by CT scans. Fluorochrome labelling was used for new bone formation detection. The animals were sacrificed at week 10, and the specimens were harvested for histological and histomorphometric analysis. In histological and fluorescence microscopic analysis, new bone formation could be found, as well as new blood vessels and connective tissue. No significant differences were found regarding the histological analysis and bone density measurements between the groups. It could be demonstrated that the omentum majus is a practical way to use one's own body as a bioreactor for prefabrication of tissue-engineered bony constructs. Regarding the influence and exact dose of rhBMP-2, further research is necessary. To establish and improve this method, further large-animal experimental studies are also necessary.

Engineered Fat Graft Enhanced with Adipose-Derived Stromal Vascular Fraction Cells for Regenerative Medicine: Clinical, Histological and Instrumental Evaluation in Breast Reconstruction

The areas in which Stromal Vascular Fraction cells (SVFs) have been used include radiotherapy based tissue damage after mastectomy, breast augmentation, calvarial defects, Crohn's fistulas, and damaged skeletal muscle. Currently, the authors present their experience using regenerative cell therapy in breast reconstruction. The goal of this study was to evaluate the safety and efficacy of the use of Engineered Fat Graft Enhanced with Adipose-derived Stromal Vascular Fraction cells (EF-e-A) in breast reconstruction. 121 patients that were affected by the outcomes of breast oncoplastic surgery were treated with EF-e-A, comparing the results with the control group (n = 50) treated with not enhanced fat graft (EF-ne-A). The preoperative evaluation included a complete clinical examination, a photographic assessment, biopsy, magnetic resonance (MRI) of the soft tissue, and ultrasound (US). Postoperative follow-up took place at two, seven, 15, 21, 36 weeks, and then annually. In 72.8% (n = 88) of breast reconstruction treated with EF-e-A, we observed a restoration of the breast contour and an increase of 12.8 mm in the three-dimensional volume after 12 weeks, which was only observed in 27.3% (n = 33) of patients in the control group that was treated with EF-ne-A. Transplanted fat tissue reabsorption was analyzed with instrumental MRI and US. Volumetric persistence in the study group was higher (70.8%) than that in the control group (41.4%) (p < 0.0001 vs. control group). The use of EF-e-A was safe and effective in this series of treated cases.

Biomaterials-aided mandibular reconstruction using in vivo bioreactors

Large mandibular defects are clinically challenging to reconstruct due to the complex anatomy of the jaw and the limited availability of appropriate tissue for repair. We envision leveraging current advances in fabrication and biomaterials to create implantable devices that generate bone within the patients themselves suitable for their own specific anatomical pathology. The in vivo bioreactor strategy facilitates the generation of large autologous vascularized bony tissue of customized geometry without the addition of exogenous growth factors or cells. To translate this technology, we investigated its success in reconstructing a mandibular defect of physiologically relevant size in sheep. We fabricated and implanted 3D-printed in vivo bioreactors against rib periosteum and utilized biomaterial-based space maintenance to preserve the native anatomical mandibular structure in the defect site before reconstruction. Nine weeks after bioreactor implantation, the ovine mandibles were repaired with the autologous bony tissue generated from the in vivo bioreactors. We evaluated tissues generated in bioreactors by radiographic, histological, mechanical, and biomolecular assays and repaired mandibles by radiographic and histological assays. Biomaterial-aided mandibular reconstruction was successful in a large superior marginal defect in five of six (83%) sheep. Given that these studies utilized clinically available biomaterials, such as bone cement and ceramic particles, this strategy is designed for rapid human translation to improve outcomes in patients with large mandibular defects.

Review of surgical resection and reconstruction in head and neck cancer. Traditional versus current concepts

This review summarizes the development of head and neck cancer resection and reconstruction. The developments in the treatment of cancer patients are reflected in their surgical outcomes, in addition to functional and aesthetic improvements. New technologies, such as surgical simulation and planning, minimally invasive surgery, and microsurgery have been added to the field to improve surgical resection of the tumor and reconstruction. The field is still growing to optimize the management of head and neck cancer.

Reconstructive Science in Orthopedic Oncology

Limb salvage is widely practiced as standard of care in most cases of extremity bone sarcoma. Allograft and endoprosthesis reconstructions are the most widely utilized modalities for the reconstruction of large segment defects, however complication rates remain high. Aseptic loosening and infection remain the most common modes of failure. Implant integration, soft-tissue function, and infection prevention are crucial for implant longevity and function. Macro and micro alterations in implant design are reviewed in this manuscript. Tissue engineering principles using nanoparticles, cell-based, and biological augments have been utilized to develop implant coatings that improve osseointegration and decrease infection. Similar techniques have been used to improve the interaction between soft tissues and implants. Tissue engineered constructs (TEC) used in combination with, or in place of, traditional reconstructive techniques may represent the next major advancement in orthopaedic oncology reconstructive science, although preclinical results have yet to achieve durable translation to the bedside.

The Maturation of Tissue-Engineered Skeletal Muscle Units following 28-Day Ectopic Implantation in a Rat

Volumetric muscle loss (VML) is a loss of skeletal muscle that results in a sustained impairment of function and is often accompanied by physical deformity. To address the need for more innovative repair options, our laboratory has developed scaffold-free, multiphasic tissue-engineered skeletal muscle units (SMUs) to treat VML injuries. In our previous work, using the concept of the "body as a bioreactor", we have shown that implantation promotes the maturation of our SMUs beyond what is possible in vitro. Thus, in this study we sought to better understand the effect of implantation on the maturation of our SMUs, including the effects of implantation on SMU force production and cellular remodeling. We used an ectopic implantation so that we could more easily dissect the implanted tissues post-recovery and measure the force contribution of the SMU alone and compare it to pre-implantation values. This study also aimed to scale up the size of our SMUs to enable the replacement of larger volumes of muscle in our future VML studies. Overall, implantation resulted in extensive maturation of the SMUs, as characterized by an increase in force production, substantial integration with native tissue, innervation, vascularization, and the development of structural organization similar to native tissue.

Large Animal Models of an In Vivo Bioreactor for Engineering Vascularized Bone

Reconstruction of large skeletal defects is challenging due to the requirement for large volumes of donor tissue and the often complex surgical procedures. Tissue engineering has the potential to serve as a new source of tissue for bone reconstruction, but current techniques are often limited in regards to the size and complexity of tissue that can be formed. Building tissue using an in vivo bioreactor approach may enable the production of appropriate amounts of specialized tissue, while reducing issues of donor site morbidity and infection. Large animals are required to screen and optimize new strategies for growing clinically appropriate volumes of tissues in vivo. In this article, we review both ovine and porcine models that serve as models of the technique proposed for clinical engineering of bone tissue in vivo. Recent findings are discussed with these systems, as well as description of next steps required for using these models, to develop clinically applicable tissue engineering applications.

Part II: Temporomandibular Joint (TMJ)-Regeneration, Degeneration, and Adaptation

PURPOSE OF REVIEW

Elucidate temporomandibular joint (TMJ) development and pathophysiology relative to regeneration, degeneration, and adaption.

RECENT FINDINGS

The pharyngeal arch produces a highly conserved stomatognathic system that supports airway and masticatory function. An induced subperiosteal layer of fibrocartilage cushions TMJ functional and parafunctional loads. If the fibrocartilage disc is present, a fractured mandibular condyle (MC) regenerates near the eminence of the fossa via a blastema emanating from the medial periosteal surface of the ramus. TMJ degenerative joint disease (DJD) is a relatively painless osteoarthrosis, resulting in extensive sclerosis, disc destruction, and lytic lesions. Facial form and symmetry may be affected, but the residual bone is vital because distraction continues to lengthen the MC with anabolic bone modeling. Extensive TMJ adaptive, healing, and regenerative potential maintains optimal, life support functions over a lifetime. Unique aspects of TMJ development, function, and pathophysiology may be useful for innovative management of other joints.

MicroRNA‑155 targets myosin light chain kinase to inhibit the migration of human bone marrow‑derived mesenchymal stem cells

Toll‑like receptors (TLRs) are expressed in human bone marrow‑derived mesenchymal stromal cells (BM‑MSCs). The activation of TLRs is important in the proliferation, differ-entiation, migration and hematopoiesis‑supporting functions of BM‑MSCs. MicroRNAs (miRNAs) are involved in various biological functions by mediating mRNA degradation or inhibiting the translation of target genes. Our previous study confirmed that TLRs regulate the migration ability of BM‑MSCs. It was also identified that multiple miRNAs were regulated by TLRs. In view of this, it was hypothesized that TLR‑regulated miRNAs may be important in regulating the migration of BM‑MSCs. The migration ability of BM‑MSCs was evaluated following transfection of the cells with the mimics or antagonists of miRNA (miR)‑27b, miR‑146a, miR‑155 and miR‑154. miR‑155 significantly inhibited cell migration. Myosin light chain kinase (MYLK) was identified as the direct target of miR‑155 in BM‑MSCs, which was further investigated using the luciferase reporter assay. However, miR‑155 did not affect the expression of upstream proteins of the RhoA pathway controlling the activity of MYLK, suggesting that miR‑155 directly suppressed the expression of MYLK without affecting the RhoA pathway. These results may facilitate the development and clinical use of BM‑MSCs in terms of their migration.

Man as a living bioreactor: Long-term histological aspects of a mandibular replacement engineered in the patient's own body

In 2016, we reported the world's first reconstruction of a mandibular discontinuity defect using a custom-made bone transplant that had been prefabricated in the gastrocolic omentum using tissue engineering strategies. However, the tissue of an engineered human neomandible has not been evaluated histologically until now. The current study assessed the long-term histological characteristics of biopsies of the neomandible 9months after transplantation. Histological analysis showed an increased amount of vital mineralized bone tissue after 10months, in comparison to biopsies obtained earlier. The engineered bone covered the surface of the bone substitute material but also grew out typical structures of cancellous bone tissue without a core of BioOss. The amount of induced bone tissue was 32% in the biopsy. In addition, the soft tissue showed an alignment of the connective tissue fibres parallel to the trabecular bone. Increasing time and mechanical forces at the mandible led to an increased amount of mineralized tissue and remodelling of the connective tissue fibres after transplantation. Further research should focus on developing advanced scaffold materials, as the outer titanium mesh cage leads to complications.

Nonunion fractures, mesenchymal stem cells and bone tissue engineering

Depending on the duration of healing process, 5-10% of bone fractures may result in either nonunion or delayed union. Because nonunions remain a clinically important problem, there is interest in the utilization of tissue engineering strategies to augment bone fracture repair. Three basic biologic elements that are required for bone regeneration include cells, extracellular matrix scaffolds and biological adjuvants for growth, differentiation and angiogenesis. Mesenchymal stem cells (MSCs) are capable to differentiate into various types of the cells including chondrocytes, myoblasts, osteoblasts, and adipocytes. Due to their potential for multilineage differentiation, MSCs are considered important contributors in bone tissue engineering research. In this review we highlight the progress in the application of biomaterials, stem cells and tissue engineering in promoting nonunion bone fracture healing. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2551-2561, 2018.

A historical perspective with current opinion on the management of atrophic mandibular fractures

The management of atrophic mandibular fractures has been a challenge for maxillofacial surgeons for decades. During the past 70 years, various techniques for treating edentulous mandibular fractures have been advocated. These techniques have been praised, criticized, abandoned, improved, and used in combination with other methods. Although some of the principles of management outlined before the end of World War II are still valid in today's technological era, other concepts did not survive the test of time. The aim of this paper is to examine the evolution of treatment modalities for the management of atrophic mandibular fractures that have been employed over the years. Debates and discussions generated by this topic are included. Current techniques and treatment philosophies with thoughts for future therapies are provided.

Pedicled Transplantation of Axially Vascularized Bone Constructs in a Critical Size Femoral Defect

INTRODUCTION

Axial vascularization represents a mandatory requirement for clinically applied larger scale vascularized bone grafts. The aim of this study was to combine the arteriovenous (AV) loop model in the rat with a critically sized femoral bone defect and to successfully transplant axially vascularized bone constructs into the defect.

MATERIALS AND METHODS

In Groups A and C, an AV loop together with a clinically approved hydroxyapatite and beta-tricalcium phosphate (HA/β-TCP) matrix, mesenchymal stem cells, and recombinant human bone morphogenetic protein 2 were implanted into a newly designed porous titanium chamber with an integrated osteosynthesis plate in the thighs of rats, whereas in Groups B and D, the same matrix composition without AV loop and, in Group E, only the HA/β-TCP matrix were implanted. After 6 weeks, the constructs were transplanted into a 10 mm femoral defect created in the same leg, in Groups A and C, under preservation of the AV loop pedicle. Group F served as a control group with an empty chamber. Ten days (Groups A and B) and 12 weeks (Groups C-F) after transplantation, the femora together with the constructs were explanted and investigated using computed tomography (CT), micro-CT, X-ray, histology, and real-time polymerase chain reaction (RT-PCR).

RESULTS

Ten days after transplantation, Group A showed a maintained vascular supply leading to increased vascularization, cell survival in the scaffold center, and bone generation compared to Group B. After 12 weeks, there was no difference detectable among all groups regarding total vessel number, although Group C, using the AV loop, still showed increased vascularization of the construct center compared to Groups D and E. In Group C, there was still enhanced bone generation detectable compared to the other groups and increased bony fusion rate at the proximal femoral stump.

CONCLUSIONS

This study shows the combination of the AV loop model in the rat with a critically sized femoral defect. By maintenance of the vascular supply, the constructs initially showed increased vascularization, leading to increased bone formation and bony fusion in the long term.

Atrophic Mandible Fractures: Are Bone Grafts Necessary? An Update

PURPOSE

The management of atrophic mandibular fractures poses a challenge because of anatomic variations and medical comorbidities associated with elderly patients. The purpose of this article is to review and update the literature regarding the management of atrophic mandible fractures using load-bearing reconstruction plates placed without bone grafts.

MATERIALS AND METHODS

We performed a review of the English-language literature looking for atrophic mandibular fractures with or without continuity defects and reconstruction without bone grafts. Included are 2 new patients from our institution who presented with fractures of their atrophic mandibles and had continuity defects and infections. Both patients underwent reconstruction with a combination of a reconstruction plate, recombinant human bone morphogenetic protein 2, and tricalcium phosphate. This study was approved as an "exempt study" by the Institutional Review Board at the University of Kentucky. This investigation observed the Declaration of Helsinki on medical protocol and ethics.

RESULTS

Currently, the standard of care to manage atrophic mandibular fractures with or without a continuity defect is a combination of a reconstruction plate plus autogenous bone graft. However, there is a need for an alternative option for patients with substantial comorbidities. Bone morphogenetic proteins, with or without additional substances, appear to be a choice. In our experience, successful healing occurred in patients with a combination of a reconstruction plate, recombinant human bone morphogenetic protein 2, and tricalcium phosphate.

CONCLUSIONS

Whereas primary reconstruction of atrophic mandibular fractures with reconstruction plates supplemented with autogenous bone graft is the standard of care, in selected cases in which multiple comorbidities may influence local and/or systemic outcomes, bone morphogenetic proteins and tricalcium phosphate can be used as a predictable alternative to autogenous grafts.

Carbon Nanostructures in Bone Tissue Engineering

BACKGROUND

Recent advances in developing biocompatible materials for treating bone loss or defects have dramatically changed clinicians' reconstructive armory. Current clinically available reconstructive options have certain advantages, but also several drawbacks that prevent them from gaining universal acceptance. A wide range of synthetic and natural biomaterials is being used to develop tissue-engineered bone. Many of these materials are currently in the clinical trial stage.

METHODS

A selective literature review was performed for carbon nanostructure composites in bone tissue engineering.

RESULTS

Incorporation of carbon nanostructures significantly improves the mechanical properties of various biomaterials to mimic that of natural bone. Recently, carbon-modified biomaterials for bone tissue engineering have been extensively investigated to potentially revolutionize biomaterials for bone regeneration.

CONCLUSION

This review summarizes the chemical and biophysical properties of carbon nanostructures and discusses their functionality in bone tissue regeneration.

Mandibular Reconstruction: Overview

INTRODUCTION

Mandibular reconstruction has changed significantly over the years and continues to evolve with the introduction of newer technologies and techniques.

PURPOSE

This article reviews the history of oromandibular reconstruction, biomechanics of mandible, summarizes the reconstruction options available for mandible with defect classification, goals in reconstruction, the various donor sites, current reconstructive options, dental rehabilitation and persistent associated problems.

SUMMARY

Oromandibular reconstruction, although a challenge for the head and neck reconstructive surgeon, is now reliable and highly successful with excellent long-term functional and aesthetic outcomes with the use of autogenous bone grafts and current reconstructive options. The ideal reconstruction would provide a solid arch to articulate with the upper jaw, restoring swallowing speech, mastication, and esthetics. Autogenous vascularized bone grafts in combination with microsurgical techniques have revolutionized mandibular reconstruction in oral cancer surgery. Current trends in mandibular reconstruction aim to achieve reestablishment of a viable mandible of proper form and maxillary mandibular relationship while decreasing the need for invasive autogenous graft procurement. However the optimal reconstruction of mandibular defects is still controversial in regards to reconstructive options which include the donor site selection, timing of surgery and method of reconstruction.

Autologous temporomandibular joint reconstruction independent of exogenous additives: a proof-of-concept study for guided self-generation

Joint defects are complex and difficult to reconstruct. By exploiting the body’s own regenerative capacity, we aimed to individually generate anatomically precise neo-tissue constructs for autologous joint reconstruction without using any exogenous additives. In a goat model, CT scans of the mandibular condyle including articular surface and a large portion of the ascending ramus were processed using computer-aided design and manufacturing. A corresponding hydroxylapatite negative mold was printed in 3D and temporarily embedded into the transition zone of costal periosteum and perichondrium. A demineralized bone matrix scaffold implanted on the contralateral side served as control. Neo-tissue constructs obtained by guided self-generation exhibited accurate configuration, robust vascularization, biomechanical stability, and function. After autologous replacement surgery, the constructs showed stable results with similar anatomical, histological, and functional findings compared to native controls. Further studies are required to assess long-term outcome and possible extensions to other further applications. The absence of exogenous cells, growth factors, and scaffolds may facilitate clinical translation of this approach.