Craniomaxillofacial reconstruction using allotransplantation and tissue engineering: challenges, opportunities, and potential synergy

Evaluating osteogenic effects associated with the incorporation of ascorbic acid in mineralized collagen scaffolds

Current treatments for craniomaxillofacial (CMF) defects motivate the design of instructive biomaterials that can promote osteogenic healing of complex bone defects. We report methods to promote in vitro osteogenesis of human mesenchymal stem cells (hMSCs) within a model mineralized collagen scaffold via the incorporation of ascorbic acid (vitamin C), a key factor in collagen biosynthesis and bone mineralization. An addition of 5 w/v% ascorbic acid into the base mineralized collagen scaffold significantly changes key morphology characteristics including porosity, macrostructure, and microstructure. This modification promotes hMSC metabolic activity, ALP activity, and hMSC-mediated deposition of calcium and phosphorous. Additionally, the incorporation of ascorbic acid influences osteogenic gene expression (BMP-2, RUNX2, COL1A2) and delays the expression of genes associated with osteoclast activity and bone resorption (OPN, CTSK), though it reduces the secretion of OPG. Together, these findings highlight ascorbic acid as a relevant component for mineralized collagen scaffold design to promote osteogenic differentiation and new bone formation for improved CMF outcomes.

Polymeric Nanocomposite Hydrogel Scaffolds in Craniofacial Bone Regeneration: A Comprehensive Review

Nanocomposite biomaterials combine a biopolymeric matrix structure with nanoscale fillers. These bioactive and easily resorbable nanocomposites have been broadly divided into three groups, namely natural, synthetic or composite, based on the polymeric origin. Preparing such nanocomposite structures in the form of hydrogels can create a three-dimensional natural hydrophilic atmosphere pivotal for cell survival and new tissue formation. Thus, hydrogel-based cell distribution and drug administration have evolved as possible options for bone tissue engineering and regeneration. In this context, nanogels or nanohydrogels, created by cross-linking three-dimensional polymer networks, either physically or chemically, with high biocompatibility and mechanical properties were introduced as promising drug delivery systems. The present review highlights the potential of hydrogels and nanopolymers in the field of craniofacial tissue engineering and bone regeneration.

The current regenerative medicine approaches of craniofacial diseases: A narrative review

Craniofacial deformities (CFDs) develop following oncological resection, trauma, or congenital disorders. Trauma is one of the top five causes of death globally, with rates varying from country to country. They result in a non-healing composite tissue wound as they degenerate in soft or hard tissues. Approximately one-third of oral diseases are caused by gum disease. Due to the complexity of anatomical structures in the region and the variety of tissue-specific requirements, CFD treatments present many challenges. Many treatment methods for CFDs are available today, such as drugs, regenerative medicine (RM), surgery, and tissue engineering. Functional restoration of a tissue or an organ after trauma or other chronic diseases is the focus of this emerging field of science. The materials and methodologies used in craniofacial reconstruction have significantly improved in the last few years. A facial fracture requires bone preservation as much as possible, so tiny fragments are removed initially. It is possible to replace bone marrow stem cells with oral stem cells for CFDs due to their excellent potential for bone formation. This review article discusses regenerative approaches for different types of craniofacial diseases.

Biodegradable Zn-Cu-Fe Alloy as a Promising Material for Craniomaxillofacial Implants: An in vitro Investigation into Degradation Behavior, Cytotoxicity, and Hemocompatibility

Zinc-based nanoparticles, nanoscale metal frameworks and metals have been considered as biocompatible materials for bone tissue engineering. Among them, zinc-based metals are recognized as promising biodegradable materials thanks to their moderate degradation rate ranging between magnesium and iron. Nonetheless, materials’ biodegradability and the related biological response depend on the specific implant site. The present study evaluated the biodegradability, cytocompatibility, and hemocompatibility of a hot-extruded zinc-copper-iron (Zn-Cu-Fe) alloy as a potential biomaterial for craniomaxillofacial implants. Firstly, the effect of fetal bovine serum (FBS) on in vitro degradation behavior was evaluated. Furthermore, an extract test was used to evaluate the cytotoxicity of the alloy. Also, the hemocompatibility evaluation was carried out by a modified Chandler-Loop model. The results showed decreased degradation rates of the Zn-Cu-Fe alloy after incorporating FBS into the medium. Also, the alloy exhibited acceptable toxicity towards RAW264.7, HUVEC, and MC3T3-E1 cells. Regarding hemocompatibility, the alloy did not significantly alter erythrocyte, platelet, and leukocyte counts, while the coagulation and complement systems were activated. This study demonstrated the predictable in vitro degradation behavior, acceptable cytotoxicity, and appropriate hemocompatibility of Zn-Cu-Fe alloy; therefore, it might be a candidate biomaterial for craniomaxillofacial implants.

Evaluation of bone formation using recombinant human bone morphogenetic proteins-7 in small maxillofacial bony defects

Context

Bone morphogenetic proteins (BMP) are multifunctional molecules of transforming growth factor-β superfamily that induces the differentiation of fibroblasts into osteoblasts to form bone.

Aims

This study was undertaken to evaluate the effects of recombinant human BMP-7 (rhBMP-7) in bone healing of small maxillofacial bone defects and assess the serum levels of osteopontin (OPN) and receptor activator of nuclear factor kappa-B ligand (RANKL) biomarkers for bone remodeling.

Materials and Methods

Twenty patients with small maxillofacial bony defects were enrolled in this study and randomly allocated to two groups; wherein after apicoectomy of the involved teeth, the control group had defect filled with collagen sponge only while the experimental group had rhBMP-7 impregnated collagen sponge placed in the defect.

Results

The clinical parameters showed no significant difference between the two groups (P > 0.05). The radiographic parameters showed a significantly slower rate of reduction in bone defect volume (P < 0.01) in control group than the experimental group when followed at 2, 4 and 24 postoperative weeks. RANKL and OPN serum levels showed no significant changes in pre- and post-operative stage.

Conclusion

This study confirms that rhBMP-7 in collagen definitely accelerates bone healing in maxillofacial bone defects and minimizes postoperative complications. RANKL and OPN biomarkers in serum may not show bone remodeling, hence tissue samples may be used to assess their levels.

Novel standardized massive bone defect model in rats employing an internal eight-hole stainless steel plate for bone tissue engineering

Massive bone defects are a challenge in orthopaedic research. Defective regeneration leads to bone atrophy, non-union of bone, and physical morbidity. Large animals are important models, however, production costs are high, nursing is complex, and evaluation methods are limited. A suitable laboratory animal model is required to explore the underlying molecular mechanism and cellular process of bone tissue engineering. We designed a stainless steel plate with 8 holes; the middle 2 holes were used as a guide to create a standardized critical size defect in the femur of anaesthetized rats. The plate was fixed to the bone using 6 screws, serving as an inner fixed bracket to secure a tricalcium phosphate implant seeded with green fluorescent protein-positive rat bone marrow mesenchymal stem cells within the defect. In some animals, we also grafted a vessel bundle into the lateral side of the implant, to promote vascularized bone tissue engineering. X-ray, microcomputed tomography, and histological analyses demonstrated the stainless steel plate resulted in a stable large segmental defect model in the rat femur. Vascularization significantly increased bone formation and implant degradation. Moreover, survival and expansion of green fluorescent protein-positive seeded cells could be clearly monitored in vivo at 1, 4, and 8 weeks postoperation via fluorescent microscopy. This standardized large segmental defect model in a small animal may help to advance the study of bone tissue engineering. Furthermore, availability of antibodies and genetically modified rats could help to dissect the precise cellular and molecular mechanisms of bone repair.

Ethical issues in pediatric face transplantation

Facial transplantation has become a reality in adult medicine. Children are subject to congenital craniofacial differences, disease-related, traumatic, or thermochemical craniofacial changes and might be suitable for face transplantation. This manuscript addresses unique ethical issues in considering potential pediatric face transplant. These challenges are operant at the individual, technologic, and psychosocial level for clinicians, investigators, and society.

Guided Self-Generation of Vascularized Neo-Bone for Autologous Reconstruction of Large Mandibular Defects

Reconstruction of large mandibular defects is complex and challenging. The authors aimed to individually self-generate a large vascularized bone construct for autologous transplantation without the use of exogenous additives based on the concept of guided self-generation. Using computer-aided design and manufacturing a large size goat mandibular bone was reconstructed in 3 dimensions. Its negative mold printed from hydroxylapatite was temporarily embedded into the costal periosteum along with a contralateral demineralized bone matrix scaffold as control. After 3 months, a mandibular bone construct was obtained and used for autologous transplantation. Osteogenesis and angiogenesis were assessed by real-time imaging, histology, and biomechanical tests during neo-bone formation and up to 6 months after transplantation surgery. A total of 20 animals received implantation of a mandibular bone negative mold along with a contralateral demineralized bone matrix scaffold. Resulting negative mold mandibular bone constructs showed anatomically, histologically, and functionally similar characteristics compared with native controls. Only 1 goat presented partial fibrosis during construct generation with subsequent absorbtion after reconstruction. The absence of exogenous cells, growth factors, and scaffolds facilitated direct translation of this novel concept into clinical application. Further studies are needed to determine functional long-term outcomes and possible extensions to other tissues and organs.

A rapid, flexible method for incorporating controlled antibiotic release into porous polymethylmethacrylate space maintainers for craniofacial reconstruction

Severe injuries in the craniofacial complex, resulting from trauma or pathology, present several challenges to functional and aesthetic reconstruction. The anatomy and position of the craniofacial region make it vulnerable to injury and subsequent local infection due to external bacteria as well as those from neighbouring structures like the sinuses, nasal passages, and mouth. Porous polymethylmethacrylate (PMMA) "space maintainers" have proven useful in staged craniofacial reconstruction by promoting healing of overlying soft tissue prior to reconstruction of craniofacial bones. We describe herein a method by which the porosity of a prefabricated porous PMMA space maintainer, generated by porogen leaching, can be loaded with a thermogelling copolymer-based drug delivery system. Porogen leaching, space maintainer prewetting, and thermogel loading all significantly affected the loading of a model antibiotic, colistin. Weeks-long release of antibiotic at clinically relevant levels was achieved with several formulations. In vitro assays confirmed that the released colistin maintained its antibiotic activity against several bacterial targets. Our results suggest that this method is a valuable tool in the development of novel therapeutic approaches for the treatment of severe complex, infected craniofacial injuries.

Optimizing Hybrid Occlusion in Face-Jaw-Teeth Transplantation: A Preliminary Assessment of Real-Time Cephalometry as Part of the Computer-Assisted Planning and Execution Workstation for Craniomaxillofacial Surgery

BACKGROUND

The aesthetic and functional outcomes surrounding Le Fort-based, face-jaw-teeth transplantation have been suboptimal, often leading to posttransplant class II/III skeletal profiles, palatal defects, and "hybrid malocclusion." Therefore, a novel technology-real-time cephalometry-was developed to provide the surgical team instantaneous, intraoperative knowledge of three-dimensional dentoskeletal parameters.

METHODS

Mock face-jaw-teeth transplantation operations were performed on plastic and cadaveric human donor/recipient pairs (n = 2). Preoperatively, cephalometric landmarks were identified on donor/recipient skeletons using segmented computed tomographic scans. The computer-assisted planning and execution workstation tracked the position of the donor face-jaw-teeth segment in real time during the placement/inset onto recipient, reporting pertinent hybrid cephalometric parameters from any movement of donor tissue. The intraoperative data measured through real-time cephalometry were compared to posttransplant measurements for accuracy assessment. In addition, posttransplant cephalometric relationships were compared to planned outcomes to determine face-jaw-teeth transplantation success.

RESULTS

Compared with postoperative data, the real-time cephalometry-calculated intraoperative measurement errors were 1.37 ± 1.11 mm and 0.45 ± 0.28 degrees for the plastic skull and 2.99 ± 2.24 mm and 2.63 ± 1.33 degrees for the human cadaver experiments. These results were comparable to the posttransplant relations to planned outcome (human cadaver experiment, 1.39 ± 1.81 mm and 2.18 ± 1.88 degrees; plastic skull experiment, 1.06 ± 0.63 mm and 0.53 ± 0.39 degrees).

CONCLUSION

Based on this preliminary testing, real-time cephalometry may be a valuable adjunct for adjusting and measuring "hybrid occlusion" in face-jaw-teeth transplantation and other orthognathic surgical procedures.

Osteoinduction of umbilical cord and palate periosteum-derived mesenchymal stem cells on poly(lactic-co-glycolic) acid nanomicrofibers

The need for tissue-engineered bone to treat complex craniofacial bone defects secondary to congenital anomalies, trauma, and cancer extirpation is sizeable. Traditional strategies for treatment have focused on autologous bone in younger patients and bone substitutes in older patients. However, the capacity for merging new technologies, including the creation of nanofiber and microfiber scaffolds with advances in natal sources of stem cells, is crucial to improving our treatment options. The advantages of using smaller diameter fibers for scaffolding are 2-fold: the similar fiber diameters mimic the in vivo extracellular matrix construct and smaller fibers also provide a dramatically increased surface area for cell-scaffold interactions. In this study, we compare the capacity for a polymer with Federal Drug Administration approval for use in humans, poly(lactic-co-glycolic) acid (PLGA) from Delta polymer, to support osteoinduction of mesenchymal stem cells (MSCs) harvested from the umbilical cord (UC) and palate periosteum (PP). Proliferation of both UC- and PP-derived MSCs was improved on PLGA scaffolds. The PLGA scaffolds promoted UC MSC differentiation (indicated by earlier gene expression and higher calcium deposition), but not in PP-derived MSCs. Umbilical cord-derived MSCs on the PLGA nanomicrofiber scaffolds have potential clinical utility in providing solutions for craniofacial bone defects, with the added benefit of earlier availability.

From bench to application: current practices in tissue engineering and its realisation at maxillofacial units in Germany, Austria and Switzerland

Over the last 20 years, the highly interdisciplinary field of tissue engineering (TE) has become an established subspecialty in research facilities all over the world. Numerous methods and protocols are available for various research intentions and aims, but there are no data indicating which of these methods and resources are generally used. This study is an overview of the resources and methods that are commonly applied in TE research in general, and in the field of oral and maxillofacial surgery (OMFS) in Germany, Austria and Switzerland. The DÖSAK collaborative group for TE developed a detailed questionnaire and collected information from participating university hospitals in these three countries. We evaluated the availability of research facilities, in vitro realisation and in vivo designs for animal studies in these departments. 11 units who replied, out of 35 we contacted, conducted research on bone regeneration in interdisciplinary research facilities. 10 departments used xenogeneic and alloplastic scaffolds for in vitro and in vivo applications. In this case, the most commonly utilised trademarks were Bio-Oss(®) and CERASORB(®). 9 units used osteoblasts (73%) and 10 proliferation assays in vitro, whereas rats served as the standard animal model for histology/immunohistochemistry in 6. All research units were interested in establishing a platform for research exchange and communication. This study shows that tissue engineering is well established and highly accepted in most participating university hospitals and research facilities. The presented data, together with data published in a foregoing paper will help arrange more readily available standardised procedures for further investigations.

Porcine small intestine submucosal grafts for post-tumor resection orbital reconstruction

OBJECTIVES/HYPOTHESIS

Removal of the medial orbital wall for sinonasal tumor involvement is required to obtain complete oncologic resection. However, orbital fat herniation can produce significant morbidity, including enophthalmos and diplopia. The purpose of the current study was to evaluate outcomes following use of porcine small intestine submucosa (SIS) grafts for orbital reconstruction following extirpation of sinonasal malignancies.

STUDY DESIGN

Case series in a tertiary hospital setting.

METHODS

Review of prospectively collected data regarding orbital reconstruction using SIS was performed. Demographics, tumor histology, size of orbital defect, adjuvant treatment, clinical status, and complications were recorded.

RESULTS

Seventeen patients (average age, 58 years; range, 27-82 years) had SIS grafting of the medial orbital wall over a 5-year period at our tertiary academic institution. The average orbital wall defect size was 4.6 cm(2) (range, 1 cm(2)-24 cm(2)). Tumor histopathology included esthesioneuroblastoma (n = 5), squamous cell carcinoma (n = 4), adenocarcinoma (n = 2), sinonasal undifferentiated carcinoma (n = 2), melanoma (n = 3), and neuroendocrine carcinoma (n = 1). Surgical goals were curative intent in all patients. Ten patients had postoperative radiation therapy, whereas five individuals had surgical extirpation following neoadjuvant chemotherapy and radiation. All patients had complete locoregional control at last clinical follow-up (average, 16 months; range, 2-54 months), although three patients developed distant metastases. The only orbital complications noted were enophthalmos (n = 1), periorbital cellulitis (n = 1), and orbital wall crusting (n = 1).

CONCLUSIONS

SIS reconstruction of orbital wall defects was effective in the current series of patients, with only one patient developing noticeable enophthalmos and a low incidence of surgical complications.

LEVEL OF EVIDENCE

4.

Investigation of severe craniomaxillofacial battle injuries sustained by u.s. Service members: a case series

This case series describes craniomaxillofacial battle injuries, currently available surgical techniques, and the compromised outcomes of four service members who sustained severe craniomaxillofacial battle injuries in Iraq or Afghanistan. Demographic information, diagnostic evaluation, surgical procedures, and outcomes were collected and detailed with a follow-up of over 2 years. Reconstructive efforts with advanced, multidisciplinary, and multiple revision procedures were indicated; the full scope of conventional surgical options and resources were utilized. Patients experienced surgical complications, including postoperative wound dehiscence, infection, flap failure, inadequate mandibular healing, and failure of fixation. These complications required multiple revisions and salvage interventions. In addition, facial burns complicated reconstructive efforts by delaying treatment, decreasing surgical options, and increasing procedural numbers. All patients, despite multiple surgeries, continue to have functional and aesthetic deficits as a result of their injuries. Currently, no conventional treatments are available to satisfactorily reconstruct the face severely ravaged by explosive devices to an acceptable level, much less to natural form and function.

Bone repair cells for craniofacial regeneration

Reconstruction of complex craniofacial deformities is a clinical challenge in situations of injury, congenital defects or disease. The use of cell-based therapies represents one of the most advanced methods for enhancing the regenerative response for craniofacial wound healing. Both somatic and stem cells have been adopted in the treatment of complex osseous defects and advances have been made in finding the most adequate scaffold for the delivery of cell therapies in human regenerative medicine. As an example of such approaches for clinical application for craniofacial regeneration, Ixmyelocel-T or bone repair cells are a source of bone marrow derived stem and progenitor cells. They are produced through the use of single pass perfusion bioreactors for CD90+ mesenchymal stem cells and CD14+ monocyte/macrophage progenitor cells. The application of ixmyelocel-T has shown potential in the regeneration of muscular, vascular, nervous and osseous tissue. The purpose of this manuscript is to highlight cell therapies used to repair bony and soft tissue defects in the oral and craniofacial complex. The field at this point remains at an early stage, however this review will provide insights into the progress being made using cell therapies for eventual development into clinical practice.

Cellular and Molecular Bioengineering: A Tipping Point

In January of 2011, the Biomedical Engineering Society (BMES) and the Society for Physical Regulation in Biology and Medicine (SPRBM) held its inaugural Cellular and Molecular Bioengineering (CMBE) conference. The CMBE conference assembled worldwide leaders in the field of CMBE and held a very successful Round Table discussion among leaders. One of the action items was to collectively construct a white paper regarding the future of CMBE. Thus, the goal of this report is to emphasize the impact of CMBE as an emerging field, identify critical gaps in research that may be answered by the expertise of CMBE, and provide perspectives on enabling CMBE to address challenges in improving human health. Our goal is to provide constructive guidelines in shaping the future of CMBE.