Tissue engineering in plastic surgery: an up-to-date review of the current literature

Non-significant Effects of The Geometric Shape of Autologous Cartilage Grafts on Tissue Healing: An Animal Study

BACKGROUND

The reconstruction of cartilage defects for cosmetic and/or functional reasons has become routine in plastic and reconstructive surgery. However, it remains challenging due to the slow turnover and low viability of cartilage grafts. Although autologous grafts can be used to determine the shape of the defect in cartilage-reconstruction surgeries, the effect of defect shape on cartilage healing has not been reported. Here, we present the first study aiming to investigate the influence of cartilage graft geometry on healing.

METHODS

Twelve New Zealand white rabbits were used in the study. Square-, rectangle-, sphere-, and fusiform-shaped cartilage defects were applied to both ears with 1-cm² geometric templates that completely elevated the cartilage tissue without damaging the opposite perichondrium. As a control, the removed cartilage was sutured back to the right ear, whereas the left ear was sutured back without any graft. Histological examinations were made on samples taken during surgery and those taken four months post-surgery. Chondrocyte production and organisation, chondrocyte vacuolisation, collagen synthesis, proteoglycan levels, vascularisation, focal bleeding, and peripheral proliferation were scored independently by two histologists.

RESULTS

There was no statistically significant difference in the growth rates of either the control or experimental cartilage tissues when compared with that of the initial cartilage tissue (p = 0.083). Histologic comparisons revealed better outcomes in the grafted cartilage groups compared to those receiving the donor cartilage, but this was not statistically significant.

CONCLUSIONS

This study demonstrates that the geometric shape of the defect has no significant effect on cartilage healing.

LEVEL OF EVIDENCE

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Large adipose tissue generation in a mussel-inspired bioreactor of elastic-mimetic cryogel and platelets

Soft tissue generation, especially in large tissue, is a major challenge in reconstructive surgery to treat congenital deformities, posttraumatic repair, and cancer rehabilitation. The concern is along with the donor site morbidity, donor tissue shortage, and flap necrosis. Here, we report a dissection-free adipose tissue chamber-based novel guided adipose tissue regeneration strategy in a bioreactor of elastic gelatin cryogel and polydopamine-assisted platelet immobilization intended to improve angiogenesis and generate large adipose tissue in situ. In order to have matched tissue mechanics, we used 5% gelatin cryogel as growth substrate of bioreactor. Platelets from the platelet-rich plasma were then immobilized onto the gelatin cryogel with the aid of polydopamine to form a biomimetic bioreactor (polydopamine/gelatin cryogel/platelet). Platelets on the substrate led to a sustained high release in both platelet-derived growth factor and vascular endothelial growth factor compared with non-polydopamine-assisted group. The formed bioreactor was then transferred to a tissue engineering chamber and then inserted above inguinal fat pad of rats without flap dissection. This integrate strategy significantly boomed the vessel density, stimulated cellular proliferation, and upregulated macrophage infiltration. There was a noticeable rise in the expression of dual-angiogenic growth factors (platelet-derived growth factor and vascular endothelial growth factor) in chamber fluid; host cell migration and host fibrous protein secretion coordinated with gelatin cryogel degradation. The regenerated adipose tissue volume gained threefold larger than control group (p < 0.05) with less fibrosis tissue. These results indicate that a big well-vascularized three-dimensional mature adipose tissue can be regenerated using elastic gel, polydopamine, platelets, and small fat tissue.

Mesothelial Stem Cells and Stromal Vascular Fraction for Skin Rejuvenation

The use of stem cells in regenerative medicine and specifically facial rejuvenation is thought provoking and controversial. Today there is increased emphasis on tissue engineering and regenerative medicine, which translates into a need for a reliable source of stem cells in addition to biomaterial scaffolds and cytokine growth factors. Adipose tissue is currently recognized as an accessible and abundant source for adult stem cells. Cellular therapies and tissue engineering are still in their infancy, and additional basic science and preclinical studies are needed before cosmetic and reconstructive surgical applications can be routinely undertaken and satisfactory levels of patient safety achieved.

In vivo tracking of adipose tissue grafts with cadmium-telluride quantum dots

Background

Fat grafting, or lipofilling, represent frequent clinically used entities. The fate of these transplants is still not predictable, whereas only few animal models are available for further research. Quantum dots (QDs) are semiconductor nanocrystals which can be conveniently tracked in vivo due to photoluminescence.

Methods

Fat grafts in cluster form were labeled with cadmium-telluride (CdTe)-QD 770 and transplanted subcutaneously in a murine in vivo model. Photoluminescence levels were serially followed in vivo.

Results

Tracing of fat grafts was possible for 50 days with CdTe-QD 770. The remaining photoluminescence was 4.9%±2.5% for the QDs marked fat grafts after 30 days and 4.2%± 1.7% after 50 days. There was no significant correlation in the relative course of the tracking signal, when vital fat transplants were compared to non-vital graft controls.

Conclusions

For the first-time fat grafts were tracked in vivo with CdTe-QDs. CdTe-QDs could offer a new option for in vivo tracking of fat grafts for at least 50 days, but do not document vitality of the grafts.

Tissue-Engineered Solutions in Plastic and Reconstructive Surgery: Principles and Practice

Recent advances in microsurgery, imaging, and transplantation have led to significant refinements in autologous reconstructive options; however, the morbidity of donor sites remains. This would be eliminated by successful clinical translation of tissue-engineered solutions into surgical practice. Plastic surgeons are uniquely placed to be intrinsically involved in the research and development of laboratory engineered tissues and their subsequent use. In this article, we present an overview of the field of tissue engineering, with the practicing plastic surgeon in mind. The Medical Research Council states that regenerative medicine and tissue engineering “holds the promise of revolutionizing patient care in the twenty-first century.” The UK government highlighted regenerative medicine as one of the key eight great technologies in their industrial strategy worthy of significant investment. The long-term aim of successful biomanufacture to repair composite defects depends on interdisciplinary collaboration between cell biologists, material scientists, engineers, and associated medical specialties; however currently, there is a current lack of coordination in the field as a whole. Barriers to translation are deep rooted at the basic science level, manifested by a lack of consensus on the ideal cell source, scaffold, molecular cues, and environment and manufacturing strategy. There is also insufficient understanding of the long-term safety and durability of tissue-engineered constructs. This review aims to highlight that individualized approaches to the field are not adequate, and research collaboratives will be essential to bring together differing areas of expertise to expedite future clinical translation. The use of tissue engineering in reconstructive surgery would result in a paradigm shift but it is important to maintain realistic expectations. It is generally accepted that it takes 20–30 years from the start of basic science research to clinical utility, demonstrated by contemporary treatments such as bone marrow transplantation. Although great advances have been made in the tissue engineering field, we highlight the barriers that need to be overcome before we see the routine use of tissue-engineered solutions.

An Evaluation of the Stemness, Paracrine, and Tumorigenic Characteristics of Highly Expanded, Minimally Passaged Adipose-Derived Stem Cells

The use of adipose-derived stem cells (ADSC) in regenerative medicine is rising due to their plasticity, capacity of differentiation and paracrine and trophic effects. Despite the large number of cells obtained from adipose tissue, it is usually not enough for therapeutic purposes for many diseases or cosmetic procedures. Thus, there is the need for culturing and expanding cells in-vitro for several weeks remain. Our aim is to investigate if long- term proliferation with minimal passaging will affect the stemness, paracrine secretions and carcinogenesis markers of ADSC. The immunophenotypic properties and aldehyde dehydrogenase (ALDH) activity of the initial stromal vascular fraction (SVF) and serially passaged ADSC were observed by flow cytometry. In parallel, the telomerase activity and the relative expression of oncogenes and tumor suppressor genes were assessed by q-PCR. We also assessed the cytokine secretion profile of passaged ADSC by an ELISA. The expanded ADSC retain their morphological and phenotypical characteristics. These cells maintained in culture for up to 12 weeks until P4, possessed stable telomerase and ALDH activity, without having a TP53 mutation. Furthermore, the relative expression levels of TP53, RB, and MDM2 were not affected while the relative expression of c-Myc decreased significantly. Finally, the levels of the secretions of PGE₂, STC1, and TIMP2 were not affected but the levels of IL-6, VEGF, and TIMP 1 significantly decreased at P2. Our results suggest that the expansion of passaged ADSC does not affect the differentiation capacity of stem cells and does not confer a cancerous state or capacity in vitro to the cells.

Collagen gel formation in the presence of a carbon nanobrush

Type I, bovine skin collagen was allowed to gel in the presence of various concentrations of a carbon nanotube material covered with a polystyrene/polyaniline copolymer, called a carbon nanobrush (CNB). The rate of collagen gelation was enhanced by the presence of the CNB in a dose dependent manner. The extent of collagen gelation was due to the concentration of collagen and not the amount of CNB. Collagen D-periodicity, and average fibril diameter were unchanged by the CNB material as seen in transmission electron micrographs. Gel tensile strength was reduced by the presence of the CNB in a dose related manner. The collagen-CNB mixture may have a role in the repair and reconstruction of wounds or degenerated connective tissue.

Stem cell and research in plastic surgery

Regenerative medicine using stem cells has progressed significantly over the last decade. Plastic surgeons historically have used tissues of human being to restore various defect sites and utilized a single cell lines for the tissue regeneration. The cell sources (autologous or allogeneic), cell types (embryonic stem cell or adult stem cell), and source of tissues (bone marrow, muscle, adipose, cartilage, or blood) are very important for stem cell-based tissue coverage. Embryonic stem cells are pluripotent precursors obtained from the inner cell mass of the blastocyst and reported to be used for preventing muscle atrophy after peripheral nerve injury. Multipotent adult stem cells are easily accessed for plastic surgeons during many routine procedures. This article briefly review the current state of overall stem cell research and clinical applications in the plastic surgical field.

Tissue engineering chamber promotes adipose tissue regeneration in adipose tissue engineering models through induced aseptic inflammation

Tissue engineering chamber (TEC) makes it possible to generate significant amounts of mature, vascularized, stable, and transferable adipose tissue. However, little is known about the role of the chamber in tissue engineering. Therefore, to investigate the role of inflammatory response and the change in mechanotransduction started by TEC after implantation, we placed a unique TEC model on the surface of the groin fat pads in rats to study the expression of cytokines and tissue development in the TEC. The number of infiltrating cells was counted, and vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) expression levels in the chamber at multiple time points postimplantation were analyzed by enzyme-linked immunosorbent assay. Tissue samples were collected at various time points and labeled for specific cell populations. The result showed that new adipose tissue formed in the chamber at day 60. Also, the expression of MCP-1 and VEGF in the chamber decreased slightly from an early stage as well as the number of the infiltrating cells. A large number of CD34+/perilipin- perivascular cells could be detected at day 30. Also, the CD34+/perilipin+ adipose precursor cell numbers increased sharply by day 45 and then decreased by day 60. CD34-/perilipin+ mature adipocytes were hard to detect in the chamber content at day 30, but their number increased and then peaked at day 60. Ki67-positive cells could be found near blood vessels and their number decreased sharply over time. Masson's trichrome showed that collagen was the dominant component of the chamber content at early stage and was replaced by newly formed small adipocytes over time. Our findings suggested that the TEC implantation could promote the proliferation of adipose precursor cells derived from local adipose tissue, increase angiogenesis, and finally lead to spontaneous adipogenesis by inducing aseptic inflammation and changing local mechanotransduction.

Effects of photochemical riboflavin-mediated crosslinks on the physical properties of collagen constructs and fibrils

The use of collagen scaffold in tissue engineering is on the rise, as modifications to mechanical properties are becoming more effective in strengthening constructs whilst preserving the natural biocompatibility. The combined technique of plastic compression and cross-linking is known to increase the mechanical strength of the collagen construct. Here, a modified protocol for engineering these collagen constructs is used to bring together a plastic compression method, combined with controlled photochemical crosslinking using riboflavin as a photoinitiator. In order to ascertain the effects of the photochemical crosslinking approach and the impact of the crosslinks created upon the properties of the engineered collagen constructs, the constructs were characterized both at the macroscale and at the fibrillar level. The resulting constructs were found to have a 2.5 fold increase in their Young's modulus, reaching a value of 650 ± 73 kPa when compared to non-crosslinked control collagen constructs. This value is not yet comparable to that of native tendon, but it proves that combining a crosslinking methodology to collagen tissue engineering may offer a new approach to create stronger, biomimetic constructs. A notable outcome of crosslinking collagen with riboflavin is the collagen's greater affinity for water; it was demonstrated that riboflavin crosslinked collagen retains water for a longer period of time compared to non-cross-linked control samples. The affinity of the cross-linked collagen to water also resulted in an increase of individual collagen fibrils' cross-sectional area as function of the crosslinking. These changes in water affinity and fibril morphology induced by the process of crosslinking could indicate that the crosslinked chains created during the photochemical crosslinking process may act as intermolecular hydrophilic nanosprings. These intermolecular nanosprings would be responsible for a change in the fibril morphology to accommodate variable volume of water within the fibril.

Electrospinning of PCL/PVP blends for tissue engineering scaffolds

Currently, one of the main drawbacks of using poly(ε-caprolactone) in the biomedical and pharmaceutical fields is represented by its low biodegradation rate. To overcome this limitation, electrospinning of PCL blended with a water-soluble poly(N-vinyl-2-pyrrolidone) was used to fabricate scaffolds with tunable fiber surface morphology and controllable degradation rates. Electrospun scaffolds revealed a highly immiscible blend state. The incorporated PVP phase was dispersed as inclusions within the electrospun fibers, and then easily extracted by immersing them in cell culture medium, exhibiting nanoporosity on the fiber surface. As a striking result, nanoporosity facilitated not only fiber biodegradation rates, but also improved cell attachment and spreading on the blend electrospun scaffolds. The present findings demonstrate that simultaneous electrospinning technique for PCL with water-soluble PVP provides important insights for successful tuning biodegradation rate for the PCL electrospun scaffolds but not limited to expand other high valuable biocompatible polymers for the future biomedical applications, ranging from tissue regeneration to controlled drug delivery.

Dynamic reanimation for facial palsy: an overview

Facial paralysis can have a profound effect on the patient from both an aesthetic and functional point of view. The symptoms depend on which branch of the nerve has been damaged and the severity of the injury. The purpose of this paper is to review currently available treatments for dynamic reanimation of a damaged facial nerve, and the goals are a symmetrical and coordinated smile. Careful selection of patients and use of the appropriate surgical technique can have excellent results.

Human auricular tissue engineering in an immunocompetent animal model

BACKGROUND

Tissue engineering has the potential to provide ear-shaped cartilaginous constructs in the near future. Previous attempts to engineer human ear-shaped constructs mimicked human shape and characteristics but were done in immunocompromised animal models.

OBJECTIVES

The authors design and evaluate a novel, 3-dimensional (3D) cell-copolymer construct resembling a human ear that was subsequently implanted in an immunocompetent rabbit model.

MATERIALS

Mesenchymal progenitor cells that were obtained from perichondrium and chondrium of a rabbit auricular cartilaginous site were expanded in vitro to chondrocytes and seeded onto biodegradable alginate and silk polymer ear-shaped scaffolds. After implantation in the back of 6 immunocompetent rabbits for 8 weeks, cell/scaffold constructs were harvested and analyzed in terms of size, shape, and histology.

RESULTS

Data from this study suggest that auricular mesenchymal progenitor cells derived from rabbit perichondrium and chondrium are suitable for development of tissue-engineered human ear models with retention over time of 3D construct architecture. Gross morphology revealed that the silk alginate scaffold diminished slightly the size dimensions but maintained shape and flexibility. Histological analysis showed formation of cartilage tissue along with type II collagen and proteoglycan extracellular matrix components of the silk alginate construct.

CONCLUSIONS

This study demonstrates for the first time that it is possible to engineer an ear cartilage construct that resembles the human ear not only in shape but also in size and flexibility in a real test model. This study also confirms that the association of silk, alginate, and perichondrium and chondrium mesenchymal cells is a reliable method to produce an engineered auricular cartilage construct. Further long-term research needs to be done to confirm these observations.

Resilin-Like Polypeptide Hydrogels Engineered for Versatile Biological Functions

Natural resilin, the rubber-like protein that exists in specialized compartments of most arthropods, possesses excellent mechanical properties such as low stiffness, high resilience and effective energy storage. Recombinantly-engineered resilin-like polypeptides (RLPs) that possess the favorable attributes of native resilin would be attractive candidates for the modular design of biomaterials for engineering mechanically active tissues. Based on our previous success in creating a novel RLP-based hydrogel and demonstrating useful mechanical and cell-adhesive properties, we have produced a suite of new RLP-based constructs, each equipped with 12 repeats of the putative resilin consensus sequence and a single, distinct biologically active domain. This approach allows independent control over the concentrations of cell-binding, MMP-sensitive, and polysaccharide-sequestration domains in hydrogels comprising mixtures of the various RLPs. The high purity, molecular weight and correct compositions of each new polypeptide have been confirmed via high performance liquid chromatography (HPLC), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), and amino acid analysis. These RLP-based polypeptides exhibit largely random-coil conformation, both in solution and in the cross-linked hydrogels, as indicated by circular dichroic and infrared spectroscopic analyses. Hydrogels of various compositions, with a range of elastic moduli (1kPa to 25kPa) can be produced from these polypeptides, and the activity of the cell-binding and matrix metalloproteinase (MMP) sensitive domains was confirmed. Tris(hydroxymethyl phosphine) cross-linked RLP hydrogels were able to maintain their mechanical integrity as well as the viability of encapsulated primary human mesenchymal stem cells (MSCs). These results validate the promising properties of these RLP-based elastomeric biomaterials.

Adipogenic differentiation of scaffold-bound human adipose tissue-derived stem cells (hASC) for soft tissue engineering

Adipose tissue engineering, instead of tissue substitution, often uses autologous adipose tissue-derived stem cells (hASC). These cells are known to improve graft integration and to support neovascularization of scaffolds when seeded onto biomaterials. In this study we thought to engineer adipose tissue using scaffold-bound hASC, since they can be differentiated into the adipocyte cell lineage and used for soft tissue regeneration. We show here by microscopy and gene expression of the peroxysome proliferator-activated receptor gene (PPARγ2) that hASC growing on polypropylene fibrous scaffolds as well as on three-dimensional nonwoven scaffolds can be turned into adipose tissue within 19 days. Freshly isolated hASC displayed a higher differentiation potential than hASC cultured for eight passages. In addition, we proved a modified alginate microcapsule to directly induce adipogenic differentiation of incorporated hASC. The results may help to improve long-term success of adipose tissue regeneration, especially for large-scale soft tissue defects, and support the development of cell-scaffold combinations which can be shaped individually and directly induce the adipogenic differentiation of incorporated hASC at the site of implantation.

Tissue engineering for the management of chronic wounds: current concepts and future perspectives

Chronic wounds constitute a significant and growing biomedical burden. With the increasing growth of populations prone to dysfunctional wound healing, there is an urgent and unmet need for novel strategies to both prevent and treat these complications. Tissue engineering offers the potential to create functional skin, and the synergistic efforts of biomedical engineers, material scientists, and molecular and cell biologists have yielded promising therapies for non-healing wounds. However, traditional paradigms for wound healing focus largely on the role of inflammatory cells and fail to incorporate more recent research highlighting the importance of stem cells and matrix dynamics in skin repair. Approaches to chronic wound healing centred on inflammation alone are inadequate to guide the development of regenerative medicine-based technologies. As the molecular pathways and biologic defects underlying non-healing wounds are further elucidated, multifaceted bioengineering systems must advance in parallel to exploit this knowledge. In this viewpoint essay, we highlight the current concepts in tissue engineering for chronic wounds and speculate on areas for future research in this increasingly interdisciplinary field.

Pre-culturing human adipose tissue mesenchymal stem cells under hypoxia increases their adipogenic and osteogenic differentiation potentials

OBJECTIVES

Hypoxia is an important factor in many aspects of stem-cell biology including their viability, proliferation, differentiation and migration. We evaluated whether low oxygen level (2%) affected human adipose tissue mesenchymal stem-cell (hAT-MSC) phenotype, population growth, viability, apoptosis, necrosis and their adipogenic and osteogenic differentiation potential.

MATERIALS AND METHODS

hAT-MSCs from four human donors were cultured in growth medium under either normoxic or hypoxic conditions for 7 days and were then transferred to normoxic conditions to study their differentiation potential.

RESULTS

Hypoxia enhanced hAT-MSC expansion and viability, whereas expression of mesenchymal markers such as CD90, CD73 and endothelial progenitor cell marker CD34, remained unchanged. We also found that pre-culturing hAT-MSCs under hypoxia resulted in their enhanced ability to differentiate into adipocytes and osteocytes.

CONCLUSIONS

This protocol could be useful for maximizing hAT-MSC potential to differentiate in vitro into the adipogenic and osteogenic lineages, for use in plastic and reconstructive surgery, and in tissue engineering strategies.

Bilateral calf augmentation for aesthetic purposes

BACKGROUND

The shape of the calf is determined by the development of the soleus and gastrocnemius muscles, the length and orientation of the crural bones, and the distribution of subcutaneous fat. Some people have a naturally thin or underdeveloped calf that remains small despite exercise. Calf augmentation is indicated for cosmetic reasons or for reconstruction of a shrunken lower leg resulting from injury, illness, or congenital disability.

METHODS

A total of 53 consecutive patients (40 women and 13 men) had surgery for calf augmentation between January 2004 and January 2007. The patients ranged in age from 25 to 51 years (mean, 29.5 years). All the patients included in the study requested calf augmentation for aesthetic purposes. Asymmetric-base silicone elastomer smooth-surface implants were used. Overall satisfaction after silicone calf augmentation was rated on a scale of 1 (poor), 2 (fair), 3 (good), 4 (very good), and 5 (excellent). All the patients had surgery by the same team of surgeons (L.H.P., A.S., B.N.). The evaluation was made at follow-up office consultations after 1 year. The total mean follow-up time was 4.4 years.

RESULTS

In this study, 53 bilateral calf augmentations were performed, for a total of 106 procedures. The 125-ml implant was used in 37 bilateral cases, the 70-ml implant in 10 cases; and the 175-ml implant in 6 cases. In three cases, unilateral seroma formation needed to be drained by a partial skin incision opening. There were no cases of infection or hematoma. Hypertrophic scar was observed in four patients bilaterally. One patient requested removal of the implants, and the procedure was performed on an outpatient basis. There were no cases of compartment syndrome or deep vein thrombosis, and no pulmonary embolisms occurred. There were no cases of rotation or displacement of the implant. At 12 months, 73% of the patients rated their appearance after calf augmentation as "very good" to "excellent," and 19% responded that their appearance was "good." Only 8% of the patients thought their appearance was less than good. At this writing, the average follow-up time for this group of patients has been 3.4 years.

CONCLUSION

Calf augmentation by silicone-filled implants for cosmetic purposes appears to be effective, safe, and aesthetically pleasing, with minor side effects.

Stem cell-mediated osteogenesis: therapeutic potential for bone tissue engineering

Intervertebral disc degeneration often requires bony spinal fusion for long-term relief. Current arthrodesis procedures use bone grafts from autogenous bone, allogenic backed bone, or synthetic materials. Autogenous bone grafts can result in donor site morbidity and pain at the donor site, while allogenic backed bone and synthetic materials have variable effectiveness. Given these limitations, researchers have focused on new treatments that will allow for safe and successful bone repair and regeneration. Mesenchymal stem cells have received attention for their ability to differentiate into osteoblasts, cells that synthesize new bone. With the recent advances in scaffold and biomaterial technology as well as stem cell manipulation and transplantation, stem cells and their scaffolds are uniquely positioned to bring about significant improvements in the treatment and outcomes of spinal fusion and other injuries.

Control of Differentiation of Human Mesenchymal Stem Cells by Altering the Geometry of Nanofibers

Effective differentiation of mesenchymal stem cells (MSCs) is required for clinical applications. To control MSC differentiation, induction media containing different types of soluble factors have been used to date; however, it remains challenging to obtain a uniformly differentiated population of an appropriate quality for clinical application by this approach. We attempted to develop nanofiber scaffolds for effective MSC differentiation by mimicking anisotropy of the extracellular matrix structure, to assess whether differentiation of these cells can be controlled by using geometrically different scaffolds. We evaluated MSC differentiation on aligned and random nanofibers, fabricated by electrospinning. We found that induction of MSCs into adipocytes was markedly more inhibited on random nanofibers than on aligned nanofibers. In addition, adipoinduction on aligned nanofibers was also inhibited in the presence of mixed adipoinduction and osteoinduction medium, although osteoinduction was not affected by a change in scaffold geometry. Thus, we have achieved localized control over the direction of differentiation through changes in the alignment of the scaffold even in the presence of a mixed medium. These findings indicate that precise control of MSC differentiation can be attained by using scaffolds with different geometry, rather than by the conventional use of soluble factors in the medium.

Recent advances in reconstructive oral and maxillofacial surgery

Reconstruction within the head and neck is challenging. Defects can be anatomically complex and may already be compromised by scarring, inflammation, and infection. Tissue grafts and vascularised flaps (either pedicled or free) bring healthy tissue to a compromised wound for optimal healing and are the current gold standard for the repair of such defects, but disadvantages are their limited availability, the difficulty of shaping the flap to fit the defect and, most importantly, donor site morbidity. The importance of function and aesthetics has driven advances in the accuracy of surgical techniques. We discuss current advances in reconstruction within oral and maxillofacial surgery. Developments in navigation, three-dimensional imaging, stereolithographic models, and the use of custom-made implants can aid and improve the accuracy of existing reconstructive methods. Robotic surgery, which does not modify existing techniques of reconstruction, allows access, resection of tumours, and reconstruction with conventional free flap techniques in the oropharynx without the need for mandibulotomy. Tissue engineering and distraction osteogenesis avoid the need for autologous tissue transfer and can therefore be seen as more conservative methods of reconstruction. Recently, facial allotransplantation has allowed whole anatomical facial units to be replaced with the possibility of sensory recovery and reanimation being completed in a single procedure. However, patients who have facial allotransplants are subject to life-long immunosuppression so this method of reconstruction should be limited to selected cases.

Correction of liposuction sequelae by autologous fat transplantation

BACKGROUND

In many countries, liposuction is the most frequently performed aesthetic procedure. Although liposuction has been considered a safe surgical procedure, reports indicate that it can have significant sequelae. Irregularities ranging from "oversuctioning" to bumpy skin and asymmetries result from inadequate experience of the surgeon.

METHODS

A total of 57 consecutive female patients were operated on from June 2005 to June 2007. The age distribution of the patients ranged from 22 to 53 years, with a mean of 34.2 years. All the patients that were included in the study had undergone from one to three liposuction procedures. Overall satisfaction with the body appearance after autologous fat transplantation for correction of postliposuction irregularities was rated on a scale of 1-5, where 1 is poor, 2 is fair, 3 is good, 4 is very good, and 5 is excellent.

RESULTS

The total amount of clean adipose tissue transplanted varied from 14 to 120 ml. There were no cases of liponecrosis, which developed in the grafted area, and no liponecrotic lumps were palpated on postoperative evaluation on any operated cases. There were no cases of cellulitis at the donor or grafted area, no deep vein thrombosis, and no pulmonary embolism. There were nine cases that needed one additional session of fat grafting of 5-35 ml. Seven of those cases needed further fat grafting on the abdominal area and the remaining two needed further grafting of the infragluteal depressions. At 12 months, 68% reported that their appearance after autologous fat grafting was "very good" to "excellent" and 23% responded that their appearance was "good." Only 9% of patients thought their appearance was less than good.

CONCLUSION

With the overall acceptance of aesthetic surgery increasing and the number of patients undergoing liposuction increasing, it is likely that plastic surgeons will see more patients requesting secondary contour surgery in the future. The key to successful autologous fat grafting is familiarity with the technique, recognizing its limitations, and understanding the goals of the patient. This study has shown that the patient satisfaction rate observed after autologous fat transplantation produces aesthetically acceptable results in correcting post liposuction deformities.

Long-term stability of adipose tissue generated from a vascularized pedicled fat flap inside a chamber

BACKGROUND

Numerous studies demonstrate the generation and short-term survival of adipose tissue; however, long-term persistence remains elusive. This study evaluates long-term survival and transferability of de novo adipose constructs based on a ligated vascular pedicle and tissue engineering chamber combination.

METHODS

Defined adipose tissue flaps were implanted into rats in either intact or perforated domed chambers. In half of the groups, the chambers were removed after 10 weeks and the constructs transferred on their vascular pedicle to a new site, where they were observed for a further 10 weeks. In the remaining groups, the tissue construct was observed for 20 weeks inside the chamber. Tissue volume was assessed using magnetic resonance imaging and histologic measures, and constructs were assessed for stability and necrosis. Sections were assessed histologically and for proliferation using Ki-67.

RESULTS

At 20 weeks, volume analysis revealed an increase in adipose volume from 0.04 ± 0.001 ml at the time of insertion into the chambers to 0.27 ± 0.004 ml in the closed and 0.44 ± 0.014 ml in the perforated chambers. There was an additional increase of approximately 10 to 15 percent in tissue volume in flaps that remained in chambers for 20 weeks, whereas the volume of the transferred tissue not in chambers remained unaltered. Histomorphometric assessment of the tissues documented no signs of hypertrophy, fat necrosis, or atypical changes of the newly generated tissue.

CONCLUSION

This study presents a promising new method of generating significant amounts of mature, vascularized, stable, and transferable adipose tissue for permanent autologous soft-tissue replacement.

Biological reconstruction of bone defects: the role of the free fibula flap

This review describes the kinds of skeletal bone defects in bones which develop through enchondral ossification. It focuses on the biological reconstruction of those defects according to the two main subtypes, intercalary and osteoarticular. We list the causes of bone defects and outline the different types and configurations that result from them. We then review the currently available reconstructive options according to the patient's age and describe the theoretical options as well. Finally, the history, surgical anatomy and clinical use of the free fibula flap will be reviewed. From our own clinical experience and review of the literature, we conclude that biological reconstruction is, in many ways, superior to alloplastic materials, especially in children, adolescents and young adults.

Autologous fat transplantation versus adipose-derived stem cell-enriched lipografts: a study

BACKGROUND

Several techniques for lipoinjection have been described in the literature. Recently, the role of adult stem cells in adipose tissue has gained interest.

OBJECTIVES

The authors compare autologous fat transplantation to adipose-derived stem cell-enriched lipografts.

METHODS

A group of 20 patients with congenital or acquired facial tissue defects were included in this study and randomly divided into two groups. Ten patients were treated with autologous fat transplantation (Group A; 12-165 mL per session), and the remaining ten were treated with adipose-derived stem cell-enriched lipografts (Group B; 8-155 mL per session). Overall patient satisfaction after both treatments was evaluated at six, 12, and 18 months after the initial surgical procedure.

RESULTS

In Group A, three patients achieved aesthetically-acceptable results after the first treatment; the remaining seven patients required additional sessions. In Group B, all patients required only one treatment. Analysis of patient satisfaction in the first six months clearly demonstrated better results in Group B. However, by the 18-month evaluation, there was no statistical difference between the two groups in terms of patient satisfaction.

CONCLUSIONS

Adipose-derived stem cell-enriched lipografts produced aesthetically-acceptable results without the need for repeat treatment sessions, which are necessary with autologous fat transplantation. Further long-term studies are necessary to confirm the favorable results seen in this study.

Autologous gluteal lipograft

In the past 25 years, several different techniques of lipoinjection have been developed. The authors performed a prospective study to evaluate the patient satisfaction and the rate of complications after an autologous gluteal lipograft among 351 patients during January 2002 and January 2008. All the patients included in the study requested gluteal augmentation and were candidates for the procedure. Overall satisfaction with body appearance after gluteal fat augmentation was rated on a scale of 1 (poor), 2 (fair), 3 (good), 4 (very good), and 5 (excellent). The evaluation was made at follow-up times of 12 and 24 months. The total amount of clean adipose tissue transplanted to the buttocks varied from 100 to 900 ml. In nine cases, liponecrosis was treated by aspiration with a large-bore needle connected to a 20-ml syringe, performed as an outpatient procedure. Infection of the grafted area also occurred for four patients and was treated by incision drainage and use of antibiotics. Of the 21 patients who expressed the desire of further gluteal augmentation, 16 had one more session of gluteal fat grafting. The remaining five patients did not have enough donor area and instead received gluteal silicone implants. At 12 months, 70% reported that their appearance after gluteal fat augmentation was "very good" to "excellent," and 23% responded that their appearance was "good." Only 7% of the patients thought their appearance was less than good. At 24 months, 66% reported that their appearance after gluteal fat augmentation was "very good" (36%) to "excellent" (30%), and 27% responded that their appearance was "good." However, 7% of the patients continued to think that their appearance was less than good. At this writing, the average follow-up time for this group of patients has been 4.9 years. The key to successful gluteal fat grafting is familiarity with the technique, knowledge of the gluteal topography, and understanding of the patient's goals. With experience, the surgeon can predict the amount of volume needing to be grafted to produce the desired result. Although the aim of every surgeon is to produce the desired augmentation of the gluteal region by autologous fat grafting in one stage, the patient should be advised that a secondary procedure may be needed to accomplish the desired result.

Ethical issues in plastic and reconstructive surgery

Plastic, reconstructive, and cosmetic surgery refers to a variety of operations performed in order to repair or restore body parts to look normal or to enhance a certain structure or anatomy that is already normal. Several ethical considerations such as a patient's right for autonomy, informed consent, beneficence, and nonmalfeasance need to be given careful consideration. The principal objective of the medical profession is to render services to humanity with full respect for human dignity. Plastic surgeons should merit the confidence of patients entrusted to their care, rendering to each a full measure of service and devotion. They require an extensive amount of education and training. The increases in demand for aesthetic plastic surgery and the advocacy of practice in the media have raised concerns about the circumstances under which cosmetic surgery is ethical and permissible. Innovative research, and new technologies derived from such research, almost always raises ethical and policy concerns. Medical ethics regulate what is, and what is not, correct in promoting plastic surgery to the public. It is essential to create an educated and informed public about the ethical issues in the plastic and reconstructive surgery field. Plastic surgeons need to carefully evaluate the degree of deformity, physical and emotional maturity, and desired outcome of patients who request plastic surgery procedures. Science is a powerful force for change in modern society and plastic surgeons have a responsibility to shepherd that change with thoughtful advocacy and careful ethical scrutiny of their own behavior.

Oxygen tension differentially influences osteogenic differentiation of human adipose stem cells in 2D and 3D cultures

Skeletal defects commonly suffer from poor oxygen microenvironments resulting from compromised vascularization associated with injury or disease. Adipose stem cells (ASCs) represent a promising cell population for stimulating skeletal repair by differentiating toward the osteogenic lineage or by secreting trophic factors. However, the osteogenic or trophic response of ASCs to reduced oxygen microenvironments is poorly understood. Moreover, a direct comparison between 2D and 3D response of ASCs to hypoxia is lacking. Thus, we characterized the osteogenic and angiogenic potential of human ASCs under hypoxic (1%), normoxic (5%), and atmospheric (21%) oxygen tensions in both 2D and 3D over 4 weeks in culture. We detected greatest alkaline phosphatase activity and extracellular calcium deposition in cells cultured in both 2D and 3D under 21% oxygen, and reductions in enzyme activity corresponded to reductions in oxygen tension. ASCs cultured in 1% oxygen secreted more vascular endothelial growth factor (VEGF) over the 4-week period than cells cultured in other conditions, with cells cultured in 2D secreting VEGF in a more sustained manner than those in 3D. Expression of osteogenic markers revealed temporal changes under different oxygen conditions with peak expression occurring earlier in 3D. In addition, the increase of most osteogenic markers was significantly higher in 2D compared to 3D cultures at 1% and 5% oxygen. These results suggest that oxygen, in conjunction with dimensionality, affects the timing of the differentiation program in ASCs. These findings offer new insights for the use of ASCs in bone repair while emphasizing the importance of the culture microenvironment.

Cell-assisted lipotransfer

Adipose tissue is believed to constitute an ideal source of uncultured stromal stem cells. By optimizing the harvesting, storage, and transplantation of adipose tissue, long-lasting results can be obtained. Cell-assisted lipotransfer (CAL) is a novel approach to autologous fat transplantation in which adipose-derived stem cells are attached to the aspirated fat. The authors describe the cell processing methods, delivery systems, and clinical applications of CAL.

Tissue engineering of skin

The engineering of skin substitutes and their application on human patients has become a reality. However, cell biologists, biochemists, technical engineers, and surgeons are still struggling with the generation of complex skin substitutes that can readily be transplanted in large quantities, possibly in only one surgical intervention and without significant scarring. Constructing a dermo-epidermal substitute that rapidly vascularizes, optimally supports a stratifying epidermal graft on a biodegradable matrix, and that can be conveniently handled by the surgeon, is now the ambitious goal. After all, this goal has to be reached coping with strict safety requirements and the harsh rules of the economic market.

Tissue engineering with adipose-derived stem cells (ADSCs): current and future applications

Soft-tissue loss presents an ongoing challenge in plastic and reconstructive surgery. Standard approaches to soft-tissue reconstruction include autologous tissue flaps, autologous fat transplantation and alloplastic implants. All of these approaches have disadvantages, including donor-site morbidity, implant migration and absorption and foreign body reaction. Stem cell application has recently been suggested as a possible novel therapy. Adipose-derived stem cells (ADSCs) are an abundant, readily available population of multipotent progenitor cells that reside in adipose tissue, which is an easily accessible and abundant source of putative stem cells for translational clinical research. Their therapeutic use in pre-clinical studies and experimental clinical trials has been well documented. We present the current strategies of tissue engineering with ADSC and we discuss the possible future applications of this new method in the field of plastic and reconstructive surgery. Complete understanding of the mechanisms of interactions among adipose stem cells, growth factors and biomaterials in tissue engineering is still lacking. Adipose tissue stem cell-based regenerative strategies hold tremendous promise, although this potential must be balanced against stringent standards of scientific and clinical investigation, before developing 'off-the-shelf' tissue engineering products.

Cell-free and cell-based approaches for bone regeneration

The clinical augmentation of bone currently involves the use of autogenous or allogeneic bone grafts and synthetic materials, all of which are associated with limitations. Research on the safe enhancement of bone formation concerns the potential value of scaffolds, stem cells, gene therapy, and chemical and mechanical signals. Optimal scaffolds are engineered to provide mechanical stability while supporting osteogenesis, osteoconduction and/or osteoinduction. Scaffold materials include natural or synthetic polymers, ceramics, and composites. The resorption, mechanical strength and efficacy of these materials can be manipulated through structural and chemical design parameters. Cell-seeded scaffolds contain stem cells or progenitor cells, such as culture-expanded marrow stromal cells and multipotent skeletal progenitor cells sourced from other tissues. Despite extensive evidence from proof-of-principle studies, bone tissue engineering has not translated to clinical practice. Much of the research involves in vitro and animal models that do not replicate potential clinical applications. Problem areas include cell sources and numbers, over-reliance on existing scaffold materials, optimum delivery of factors, control of transgene expression, vascularization, integration with host bone, and the capacity to form bone and marrow structures in vivo. Current thinking re-emphasizes the potential of biomimetic materials to stimulate, enhance, or control bone's innate regenerative capacity at the implantation site.

Autologous fat transplantation to the breast: a personal technique with 25 years of experience

BACKGROUND

Over the last 30 years there has been interest in the use of autologous fat transplantation for breast reconstructive and cosmetic purposes. Up until now injection of adipose tissue into the breast has been subject to two limiting factors. First, fat injection into the breast could result in fat necrosis, cyst formation, and indurations that could be mistaken as cancerous calcifications. Second, the degree of reabsorption of the injected adipose tissue is unpredictable.

METHODS

Patients included in the study were candidates for either breast reconstruction after tumor resection or breast augmentation and were divided into three groups. Group I included patients with asymmetry after mastectomy and breast reconstruction; Group II consisted of patients with congenital breast asymmetry; and Group III included patients requesting bilateral breast augmentation. All patients signed a consent form acknowledging potential complications of infiltrating fat into the breast.

RESULTS

A total of 820 consecutive female patients were operated on between 1983 and 2007. The age distribution of the patients ranged from 19 to 78 years, with a mean of 45.6 years. There were 381 patients in Group I, 54 in Group II, and 385 in Group III. Complications included ecchymosis in 76 patients, striae in 36 patients, 12 hematomas, and 5 infections. Long-term breast asymmetry was observed in 34 cases. Six hundred seventy patients have undergone mammography and ultrasonography 6 months and 1 year after their first intervention under our care. The majority of complications resulting from lipofilling of the breast have been seen in this series during the first 6 months after each session. Breast lesions, including calcifications, cysts, and cancer, that are not apparent in the first year after the final procedure of lipofilling we believe may not be directly associated with the autologous fat grafting to the breast. This has been confirmed by the long-term follow-up of 230 patients (range = 2-25 years, mean = 11.3 years) who have been followed up yearly with mammographic examination.

CONCLUSION

In the last 25 years the results of autologous fat transplantation have been predictable and satisfying on the condition that the treatment is performed in stages with small quantities of adipose tissue fat injected in each treatment session. To prevent major complications the final expected result should not be the aim of a single procedure. Mammary lipografting is a procedure that can be offered to patients for breast reconstructive and cosmetic purposes.

Biofabrication: a 21st century manufacturing paradigm

Biofabrication can be defined as the production of complex living and non-living biological products from raw materials such as living cells, molecules, extracellular matrices, and biomaterials. Cell and developmental biology, biomaterials science, and mechanical engineering are the main disciplines contributing to the emergence of biofabrication technology. The industrial potential of biofabrication technology is far beyond the traditional medically oriented tissue engineering and organ printing and, in the short term, it is essential for developing potentially highly predictive human cell- and tissue-based technologies for drug discovery, drug toxicity, environmental toxicology assays, and complex in vitro models of human development and diseases. In the long term, biofabrication can also contribute to the development of novel biotechnologies for sustainable energy production in the future biofuel industry and dramatically transform traditional animal-based agriculture by inventing 'animal-free' food, leather, and fur products. Thus, the broad spectrum of potential applications and rapidly growing arsenal of biofabrication methods strongly suggests that biofabrication can become a dominant technological platform and new paradigm for 21st century manufacturing. The main objectives of this review are defining biofabrication, outlining the most essential disciplines critical for emergence of this field, analysis of the evolving arsenal of biofabrication technologies and their potential practical applications, as well as a discussion of the common challenges being faced by biofabrication technologies, and the necessary conditions for the development of a global biofabrication research community and commercially successful biofabrication industry.