First of all, vasculogenesis is de novo formation of the primary blood system by endothelial cells in response to local cues such as GFs and ECM [ , ]. On the other hand, angiogenesis is defined as the creation of new capillaries from pre-existing blood vessels. Upon angiogenic stimulation, endothelial cells are activated and begin to degrade their surrounding basement membrane. Then, they migrate into the interstitium to form capillary buds and sprouts and proliferate, elongating the newly blood vessel [ , ]. The strategies currently used to vascularized engineered tissues are: The use of biomaterials is a versatile strategy, easy to develop and translate into multiple tissues.
However, after implantation, the limitation of oxygen and nutrient supply remains an issue. The success of the bio implant relies on vessel ingrowth from host tissue and, therefore, scaffold design has a deep impact in vascularization rate after surgery. Nowadays, there are several studies confronting this issue using scaffolds from different sources [ , , ], converging that pore size and interconnectivity is the most critical parameters.
Besides the development of vascularized grafts, it is also necessary to develop structures that contribute to repair the damaged vasculature [ , ].
3D Cell Culture: Fundamentals and Applications in Tissue Engineering and Regenerative Medicine
Another strategy to improve blood perfusion is angiogenic factors delivery. It is well established that the addition of angiogenic factors to tissue-engineered constructs can enhance their vascularization after implantation. Parallel, there is a set of factors that stimulate cells close to the vascularization site to produce angiogenic factors. Finally, both in vivo and in vitro pre-vascularization are interesting strategies to obtain vascularized grafts for TE. In vitro prevascularization is based on the use of endothelial cells cultured under specific conditions to form pre-vascular structures.
On the other hand, in vivo pre-vascularization consists in implanting a tissue-engineered construct into a region with an artery suitable for microsurgical transfer. Despite in vitro approach does not rely on vessel ingrowth from host, avoiding consequently the need for extra surgery, it lacks the complex biological machinery that in vivo regulates vessel maturation and anastomosis.
Interestingly, in vitro pre-vascularization has been used for the regeneration of many tissues, like skin, skeletal muscle, cardiac muscle or bone [ , ]. In vivo methodology is a promising strategy since it can generate a mature and organized vasculature. However, two surgeries are required: Moreover it is highly probable to obtain an implant filled with fibrous tissue [ ]. Vascularization should be integrated in most TE fields, since the proper delivery of oxygen, nutrient and soluble effector molecules as well as removal of metabolites is essential to improve regeneration of the damaged tissue.
Although there are several existing techniques to induce vascularization, they need to be optimized in order to overcome their associated problems. Another growing application of TE is the creation of in vitro human models, which help us to identify and comprehend the factors that drive cellular processes. In fact, these models fulfill the need for reductionist approaches to understand the in vivo molecular mechanisms that rule human physiological as well as pathological processes and, in turn, better predict the effect of drugs and medical therapies.
Important efforts are being directed towards the study of different disorders such as arrhythmia [ ], skin fibrosis [ ] and wound healing [ , ] and the comprehension of the biological function of healthy organs such as skin [ - ], blood-brain barrier [ ] and mammary gland [ ] development. In this review we will focus our attention in 3D modeling for drug discovery and cancer disease. This critical process is initiated when tumor cells gain the capacity to degrade their basement membrane and invade the surrounding tissue.
Subsequently, they enter to lymphatic and blood vessels in order to disseminate into the circulation and undergo growth in distant organs or tissues [ - ]. This cascade of events occurs through Epithelial- Mesenchymal Transition EMT that involves complex changes in cell architecture and function. During EMT, tumor cells lose their epithelial phenotype, resulting in basal-apical polarity disruption, intercellular adhesions down-regulation and a dramatic remodeling of the actin cytoskeleton.
As a consequence, cells turn into a mesenchymal phenotype that switches on cell motility programs. This transition is driven by tumor microenvironment, especially by the mechanical and chemical cues that arise from ECM and neighboring cells, arranged in a 3D pattern [ , - ]. A major challenge in cancer research is the development of in vitro models that recreate the process of tumor progression, with particular focus on migration and invasion key steps.
To reach this objective, it is necessary an accurate modeling of tumor microenvironment. In classical 2D cultures, tumor cells are unnaturally polarized and have their surface mainly exposed to cultured media and rigid substrates [ 10 ]. On the other hand, 3D cultures can better capture tumor architecture, characterized by having quiescent or necrotic cells located at the internal core of the tumor and highly proliferative cells at the surface.
This situation occurs due to naturally arising mass transfer phenomena, which are caused by an elevated deposition of ECM components and a poorly organized vascular network. Therefore, 3D cultures can provide the micro-environmental conditions that control tumorogenesis [ - ]. During the last two decades, a wide range of biomaterials have been carefully designed in order to guide and promote tumor progression.
A further step in cancer research has consisted of developing synthetic biomaterials that provide both a reproducible cellular microenvironment and the flexibility to individually tune a physical or chemical characteristic with the aim of analyzing its specific role on the disease. Importantly, there are two ECM parameters that act as key regulators of cellular response in cancer and, therefore, it is essential to characterize and control them: First of all, tumors progressively stiffen their microenvironment; breast cancer tissue can be 10 times stiffer than healthy tissue [ 12 ].
This phenomenon is produced by an elevated deposition and remodeling of ECM components, mainly fibrilar collagen and hyaluronic acid, secreted by cancer cells and resident fibroblasts of the stroma [ 11 , ].
In particular, Rho proteins induce contraction of the actomyosin cytoskeleton, increasing intracellular tension, down-regulating ECM specific ligands and activating key genes in tumor progression, such as metalloproteinases [ 16 , , ]. Traditionally, in vivo stiffness values have been achieved by increasing concentration, composition or cross-linking density of the biomaterials. Natural scaffolds suffer modifications of fiber architecture, adhesiveness and pore size when increasing their stiffness.
To overcome this drawback, it has been described the use of self-assembling peptides laminin-absorbed RADI to individually tune tumor compliance microenvironment, without affecting other physical parameters [ ]. Therefore, they enable the study of the molecular mechanism whereby ECM stiffness regulates tumorogenesis, without introducing an array of confusing biophysical cues. In particular, it has been observed that ECM stiffness per se could initiate tumor progression through modulation of integrin dynamics.
Secondly, ECM binding motifs and GFs constantly interact with cells, activating signaling transduction cascades that determine cell fate. The results showed that expression of key tumoral genes EMT markers, matrix metalloproteinases, pro-angiogenic factors, etc. A further step in cancer research is the development of synthetic scaffolds that incorporate this ECM molecular composition, enabling the profound study of their specific role on the disease. An important example is the design of PEG scaffolds functionalized with integrin-binding domains RGD , which cause a major cell cluster formation and, therefore, point that integrins act as direct regulators of cell survival and proliferation [ , ].
A part of biomaterial perspective, tumor microenvironment is also comprised of stroma cells, which include fibroblasts, pro-angiogenic cells endothelial cells, pericytes and smooth muscle cells and immune system cells lymphocytes, macrophages and mast cells. They are responsible for the synthesis, deposition and modeling of a large portion of the ECM proteins. Furthermore, they secrete several paracrine GFs that participate in cancer cell growth.
Hence, these cells act as active participants in tumorogenesis rather than passive bystanders [ , ]. For this reason, co-cultures have been introduced in cancer research. Up to date, fibroblasts [ ], endothelial cells [ ] and macrophages [ ] have been cultured together with tumor cells in collagen gels. Results showed that stroma cells contributed to tumor cells migration and vasculature sprout formation trough the up-regulation of proteases and the delivery of angiogenic factors respectively.
Nowadays many questions about cancer biology remain to be answered, but TE modeling enriches the toolbox to understand disease progression and, thus, improve therapeutic approaches. To achieve this goal, it would be interesting to use more extendedly 3D models within the scientific community. The above-mentioned 3D cultures are based on combining cells, scaffolds and biomolecules.
However, we can reach a higher degree of complexity by integrating microchip and microfluidic approaches to TE. First of all, microfabrication include techniques such as photolithography, replica molding and microcontact printing, which enable the creation of structures with well-defined shapes on the micrometer scale, so that we can control cell position, morphology and function.
Secondly, microfluidics consists of manipulating small amounts to L of fluids in hollow chambers and, therefore, allows us to generate and precisely tune spatiotemporal gradients of soluble effector molecules nutrients and oxygen. The combination of both techniques can lead to organ-on-chips microdevices, which notably improve the level of cell differentiation and organization achieved with 3D models and constitute potential substitutes for animals in drug screening processes [ ]. A leading cause for this high failure rate is the use of models that miss or alter many tissue-related functions and, as a consequence, impair their predictive power.
For this reason, 3D cultures are being introduced into drug screening as promising platforms to analyze the effect of drug action, improving the effectiveness and reducing the investment of this process. They are able to recreate in a more realistic way the complexity of human tissues, while retaining the ability for high-throughput screening and cellular level imaging.
The relevance of 3D cultures becomes evident in the assessment of a drug safety profile, in terms of its interaction with the liver [ ]. This organ has the function of controlling the biotransformation and elimination of toxic waste substances from the body. Hepatocytes cultured in monolayers dedifferentiate after few passages and lose liver-specific functions, such as the expression of drug metabolizing enzymes [ , ]. On the other hand, liver toxicity is species specific; therefore the results obtained with animal models cannot be always directly translated to humans [ ].
However, these animals are still challenging and expensive to adopt in an assay format [ ]. As a consequence, 3D cultures have been proposed as alternative cellular systems predictors in drug screening processes, since it has been shown that hepatocytes regained their morphology and expression of key-liver proteins urea, fibrinogen, albumin and drug-metabolizing enzymes when cultured in alginate [ ] and synthetic self-assembling peptides by the sandwich method [ ].
An unresolved matter for TE is the translation of 3D cultures from the academia to the pharmaceutical industry. To achieve this goal, 3D cultures should meet a set of requirements, apart from biological relevance: Hence, major efforts are being made in this direction [ ]. TE is a promising approach to promote, guide and enhance the innate capacity of tissues to engage regeneration, assisting to recover function and shape where naturally would not. In fact, encouraging advances have been accomplished during the last two decades in several areas such as bone, cartilage, heart, pancreas and vasculature.
Furthermore, TE is transforming the way we study human physiology and pathophysiology, having a deep impact on the development of new therapies. As 3D cultures can bridge the gap between 2D cultures and animal models, they emerge as a valuable tool for next generation biology and biomedical research. Further research is still needed in TE. Particularly, the selection of the material appears to be a major challenge.
Concerted efforts should be directed to the optimization of synthetic scaffolds, since they can be custom-tailored depending on their specific applications.
Biomaterials & Tissue Engineering
In addition to the classical issues to be faced in every engineering discipline, TE requires special efforts to be pointed on the needs of living organisms. Either when designing models for in vitro biological studies or grafts for in vivo regeneration, it should be taken into accounts the complexity of tissue architecture. For instance, the implementation into 3D cultures of vascularization networks that facilitate a constant turnover of oxygen and nutrients is under extensive studies.
World Journal of Surgery Nature reviews, Molecular cell biology 8: Taking cancer biology to the next dimension. Considerations and practical approach. Accounting for the Effects of Tissue Complexity. Journal of cell science The Journal of cell biology, The Journal of cell biology The Journal of endocrinology Nature reviews Molecular cell biology Can J Chem Eng Polak DJ Regenerative medicine. Atala A Regenerative medicine strategies. Journal of pediatric surgery Cells, tissues, organs Journal of biomaterials applications Clifford DM, et al.
Qayyum AA, et al. Placenta 32 Suppl 4: Cortes-Morichetti M, et al. Takahashi K, Yamanaka S Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Yu J, Induced pluripotent stem cell lines derived from human somatic cells. Zhu Z, Huangfu D Human pluripotent stem cells: Molecular cell biology 9: Lee SJ Cytokine delivery and tissue engineering. Yonsei medical journal Current opinion in cell biology Advanced materials 21, Current opinion in biotechnology Expert Opinion On Drug Delivery 5: Nguyen LH, et al.
Approaches for Potential Improvement. Swiss medical weekly w Jakob M, et al. Stem cells translational medicine 1: Teixeira S, et al. J Biomed Mater Res Xia Z, et al. Cardoso D, et al. J Biomed Mater Res. Jin HH, et al. Int J Biol Macromol Caplan AI Review: Tissue Eng Part A Cheng K, et al. Stem cells translational medicine1: Grayson WL, et al. Merceron C, et al. Joint Bone Spine Longo UG, et al. Johnstone B, et al. European Cells and Materials Boeuf S, Richter W Chondrogenesis of mesenchymal stem cells: Arthritis and rheumatism Clin Orthop Relat Res Nehrer S, et al.
Sims DC, et al.
Plastic and reconstructive surgery Deponti D, et al. Tissue Maturation from In vitro to in vivo. Tissue Engineering Part A A review of its pharmacology and use as a surgical aid in ophthalmology, and its therapeutic potential in joint disease and wound healing. Rahfoth B, et al.
Biomaterial - Wikipedia
Osteoarthritis and cartilage 6: Kisiday J, et al. Paige K, et al. Plast Reconstr Surg J Gene Med 8: Shin H, Olsen B D, Khademhosseini A The mechanical properties and cytotoxicity of cell-laden double-network hydrogels based on photocrosslinkable gelatin and gellan gum biomacromolecules. Journal of biomedical materials research. Zhang S Fabrication of novel biomaterials through molecular self-assembly. J Tissue Eng Regen Med. J Tissue Eng Regen Med 2: J Biomed Mater Res A Castells-Sala C, Semino CE Biomaterials for stem cell culture and seeding for the generation and delivery of cardiac myocytes.
Curr Opin Organ Transplant Wang F, Guan J Cellular cardiomyoplasty and cardiac tissue engineering for myocardial therapy. Adv Drug Deliv Rev Curr Opin Cardiol Curr Cardiol Rev 4: Li Z, Guo X, Guan J A thermosensitive hydrogel capable of releasing bFGF for enhanced differentiation of mesenchymal stem cell into cardiomyocyte-like cells under ischemic conditions.
J Am Coll Cardiol Johnson TD, Christman KL Injectable hydrogel therapies and their delivery strategies for treating myocardial infarction. Expert Opin Drug Deliv Annu Rev Biomed Eng J R Soc Interface 9: Kleger A, Liebau S Calcium-activated potassium channels, cardiogenesis of pluripotent stem cells, and enrichment of pacemaker-like cells. Trends Cardiovasc Med Chong JJ Cell therapy for left ventricular dysfunction: Heart Lung Circ Stem Cells Dev J Surg Oncol Can J Physiol Pharmacol Vasc Health Risk Manag 8: Journal of the mechanical behavior of biomedical materials 5: Biores Open Access 2: Biomed Res Int Int J Nanomedicine 7: Mol Cell Biochem Int J Nanomedicine 6: J Control Release Minato A, Ise H, Goto M, Akaike T Cardiac differentiation of embryonic stem cells by substrate immobilization of insulin-like growth factor binding protein 4 with elastin-like polypeptides.
Nir T, Dor Y How to make pancreatic beta cells--prospects for cell therapy in diabetes. Curr Opin Biotechnol Biochem Biophys Res Commun Samuelson L, Gerber D Improved function and growth of pancreatic cells in a three-dimensional bioreactor environment. Oberg-Welsh C Long-term culture in matrigel enhances the insulin secretion of fetal porcine islet-like cell clusters in vitro. J Cell Physiol J Investig Med Curr Diab Rep Islet transplantation in the future: Use of a bioartificial pancreas. J Hep Bil Pancr Surg 3, — Am J Pathol J Cell Biochem Curr Pharm Des Risau W Mechanisms of angiogenesis.
Carmeliet P Mechanisms of angiogenesis and arteriogenesis. Sci Transl Med 3 Wang F, Li Z, Guan J Fabrication of mesenchymal stem cells-integrated vascular constructs mimicking multiple properties of the native blood vessels. J Biomater Sci Polym Nat Rev Mol Cell Biol 7: Sci Transl Med 4: J Cell Mol Med Int J Biochem Cell Biol Am J Physiol Cell Physiol Tissue Eng Part A. Exp Cell Res Am J Transplant 5: Rouwkema J, de Boer J, Van Blitterswijk CA Endothelial cells assemble into a 3-dimensional prevascular network in a bone tissue engineering construct. J Mol Cell Cardiol Moulin VJ Reconstitution of skin fibrosis development using a tissue engineering approach.
Methods Mol Biol Development of new models for in vitro studies. Ann N Y Acad Sci J Mater Sci Mater Med Gene therapy with modified MSCs might increase this therapeutic field in the near future [ 68 , 96 , ]. This may obviate the limited lifespan of chondrocytes that is an obstacle in the treatment of large OCDs [ ]. Another therapeutic possibility makes use of cultured chondrocytes, which are expanded and finally implanted at the defect site [ ]. ACI is an alternative to OAT and it involves harvesting a small amount of cartilage for chondrocyte isolation and culturing in vitro , usually from a knee ipsilateral to the ankle injury [ 87 , 88 , ].
Nevertheless, a recent study [ ] has shown that chondrocytes from the injured zone in the ankle have poorer regenerative capacities as compared with normal tissue, stating some reservations to their use in the therapeutic field. Thus, it seems that the source for harvesting cells should be a normal, healthy tissue, requiring one additional surgical procedure and limited associated morbidity. On the other hand, the differentiated cells are sensitive and can present biochemical changes or diminished viability during the processes of harvesting, culturing, expansion or re-implantation in the defect zone [ 6 ].
After 3 years of follow-up, the transplants restored considerable knee function in 14 of the 16 patients with femoral defects. The treatment resulted in the formation of new cartilage that was similar to normal cartilage in that it had an abundance of type II collagen and metachromatically stained matrix, similar as in original cartilage. Some advocate specific conditions for its use, for example a defect area more than 4 cm 2 factor predictor of a better outcome with ACI , reinstating the existence of specific injury and individual's conditions which might play a determinant role in outcome [ ].
As aforementioned, gene therapy can enhance the clinical application of differentiated cells as stated by Orth et al. That study demonstrated that chondrocytes modified for higher co-expression of IGF-1 and FGF-2 hold an increased chondrogenic capacity in vivo.
Hyaline cartilage serves as a low-friction surface with high wear resistance for weight-bearing joints. Unfortunately, it possesses an avascular and alymphatic profile which limits its autonomous regenerative capacity. The application of differentiated cells in the clinic presents additional problems such as cells' tendency towards losing their differentiated phenotype in a two-dimensional culture e. To overcome this problem in the treatment of cartilage lesions, different scaffolds have been developed for supporting cell adhesion, proliferation and maintenance of phenotype in an effective manner [ 4 , ].
Among the several scaffolds proposed in an attempt to better fulfil the requirements of cartilage regeneration process, there are substantial differences regarding the materials chosen and their physical forms i. Solid scaffolds provide a substrate on which cells can adhere, whereas gel scaffolds physically entrap the cells [ ].
The biomaterials used can be classified as synthetic or natural. Synthetic matrices present mechanical properties and degradation rates more easily tuned as compared with that of natural polymers, but some biocompatibility concerns might be raised owing to their degradation products and potential effect on native tissue and implanted cells.
However, innovations in chemistry and materials science have been improving their biocompatibility [ ]. Among the natural and synthetic materials that have been investigated e. Biomaterials used in the preparation of scaffolds for osteochondral tissue regeneration.
Biomaterials including ceramics and polymers, such as aragonite [ ], silk fibroin [ 5 , ] or tricalcium phosphate [ — ], are some of the most promising materials for OCD regeneration, alone or alternatively blended with other materials. The application of an injectable biomaterial with bioadhesive properties, for example gellan gum figure 6 a , for regeneration of cartilage has been proposed for the first time by Oliveira et al.
The gellan gum hydrogel was shown to efficiently sustain the delivery and growth of human articular chondrocytes and support the deposition of a hyaline-like ECM [ ], leading to the formation of a functional cartilage. The use of biocompatible gellan gum-based hydrogels e. The versatility of the injectable gellan gum hydrogels and functionalized derivatives allowed the development of ionic- and photo-cross-linked GG-MA hydrogels, with improved mechanical properties for in situ gelation, within seconds to a few minutes [ , ].
In other words, one can use two different forms of gellan gum-based hydrogels to transport different cells: That important work brings new insights to mimicking more precisely the native properties of tissue, because different tissues require neovascularization for regeneration, as in others vascularization and re-innervation is associated with pain and degeneration [ ].
In fact, one of the goals of TERM is, precisely, to maintain the human characteristics of the natural tissue and so the knowledge of physiology of the original tissue is crucial. Photographs of gellan gum hydrogels: Another biomaterial that has been tested, including in talar dome resurfacing, is collagen in its many presentations [ 66 ]. Besides its biocompatibility and positive results for the management of painful post-traumatic of the ankle joint, the biomechanical properties and stability remains an issue in several of its applications [ 66 , ].
Hydrogel systems have been developed to obtain optimal nutrient diffusion [ 40 , 49 ], connectivity with host matrix, adequate biodegradability, solubility and mechanical properties to facilitate the production and organization of the matrix [ 14 ]. One of the most studied hydrogels is based in HA.
The use of HA as adjuvant of microfractures surgical treatment i. Since a treatment that focuses exclusively on articular cartilage is likely to fail [ 90 ], it has been suggested that treatment strategies should be designed with the entire osteochondral unit articular cartilage and subchondral bone [ 90 ]. Therefore, bilayered porous scaffolds with poly lactide- co -glycolic PLGA seeded with BMSCs [ ] or with GFs [ ] were reported to simultaneously regenerate cartilage and subchondral bone of rabbit knee.
Porous PLGA—calcium sulfate biopolymer TruFit by Smith and Nephew, London, UK is one of the most popular commercially available devices probably the most clinically tested [ , ], and it has been applied from mono- to bilayered presentations figure 7. More recently, this device is also available in a shape adapted to the anteromedial talar corner. However, there is still little evidence-based medical data supporting its use in either acellular or cellular strategies, besides the existence of some concerns with polyglycolic acid biocompatibility [ 90 , ].
In the field of ceramic polymers, hydroxyapatite is one of the most used implant materials for medical applications owing to its high biocompatibility [ ]. It seems to be the most appropriate ceramic material for cartilage tissue engineering. However, owing to low strength and fracture toughness of the material, new approaches have been reported [ ] in order to achieve a scaffold with the most suitable properties for cartilage tissue engineering. The use of bilayered scaffolds figure 6 b that combine different materials in the same implant constitutes a natural evolution in OCD treatment, in an attempt to combine favourable properties to both bone integration and cartilage repair [ , ].
In fact, it has been shown that the hydroxyapatite layer permits adhesion and proliferation of MSCs and osteogenic differentiation in vitro [ ], while facilitating new bone formation in vivo [ 72 ]. By its turn, the cartilage-like layer is also able to support the adhesion of MSCs and can promote chondrogenesis, in vitro.
The deepest layer is composed of hydroxyapatite, the intermediate layer is a mixture of type I collagen and hydroxyapatite and the superficial layer consists of type I collagen only. In a previous study performed in vitro and in vivo , Kon et al. The ability of the scaffold to induce OCD repair without the seeding of autologous cells makes it very attractive [ ]. Comparative studies with OAT, ACI and bone-marrow-stimulation techniques are needed to establish the clinical outcome of this procedure. The requirement for full OCD repair has been approached considering the heterogeneity of different tissues, different components and layers including subchondral bone plate and different hyaline cartilage layers.
This is also part of the underlying principle for OAT. Although some attempts have been made to overcome one of the most relevant problem of OAT [ ], relevant morbidity related to donor zone in knee-to-ankle transplantation has been demonstrated [ , ]. Furthermore, other problems persist with these techniques including graft's source, achievement of joint congruence and interface between graft plugs and between grafts and native cartilage. It is generally accepted that the use of a lower number of plugs is a predictor of a better mid- to long-term outcome [ ].
Those studies have tested two main biomaterials, i. This technique can be considered as an evolution of conventional ACI and it makes use of processed cells that are harvested and isolated from the patient and expanded in vitro. Once grown, the chondrocytes are seeded between layers of a bilayered collagen scaffold in the operating room, prior to implantation of cell—scaffold construct into the defect area.
Cellular-based techniques, such as ACI and MACI, require a two-stage operative procedure, where initial harvesting of cartilage is followed by culturing and subsequent implantation of the cultured tissue. In fact, this issue has been considered one of the major drawbacks of ACI. This has been the driving force for the search for new treatment methods [ ] and development of novel and bioactive scaffolds, which can be easily implanted and fixed, and best mimic the native tissue to be repaired.
The use of bilayered tridimensional porous scaffolds enhanced by MSCs requires several years of preclinical research [ ]. Still, it remains a trend with high interest and investment from the scientific community. The histological results are available only in animal studies, but are indeed very encouraging [ ]. Clinically, they have been applied up to now only in the knee, but they may represent a solution for the repair of deep OCDs even in the ankle [ , ].
The development of the ideal scaffold has been performed in a stepwise manner and is dependent on the knowledge gained in the last few years, in what concerns the biomechanical and biological properties of native tissues [ 5 ]. MSCs are emerging as a powerful tool for treatment of cartilage lesions, thanks to their ability to differentiate into various lineages [ ]. In particular, the use of concentrated bone marrow instead of chondrocytes, in order to provide MSCs to be seeded onto the scaffold, has been recently introduced in clinical practice as a one-step procedure for the treatment of OCDs.
Two types of scaffolds were tested. Recently, the same group [ ] compared the clinical outcome in focal osteochondral monolateral talar dome lesions after three different surgical approaches: Although similar pattern of improvement was found at 3 years follow-up in all groups regarding collagen type II and proteoglycan expression, BMDCs showed a marked reduction in procedure morbidity and costs, demonstrating it to be a one-step technique able to overcome most of the drawbacks of previous techniques.
In addition, histological analysis highlighted the presence of all components of hyaline cartilage in repaired tissue, which showed various degrees of remodelling. Finally, Battaglia et al. The differentiation of MSCs into chondrocytes is a multi-factorial, complex target which requires, in vitro , the contemplation of simulators of biophysical stimulus present in normal tissues—bioreactors [ 26 , , , , ]. Both cell types remain under preclinical investigation and the bench-to-bedside transfer is still an unclosed matter.
The treatment of different focal OCDs by means of using autologous chondrocyte transplantation in tridimensional support scaffolds has been recently attempted [ 10 , , , ]. Aiming to enhance this therapeutic strategy, the simultaneous application of GFs has also been evaluated, attempting to favour local environment for short-term integration and promote differentiation [ 10 , 11 ]. A recent study comparing two commercially available methods, i Hyalograft C used by arthroscopic application and ii Chondro-Gide MACI open surgery application , concluded that both methods led to positive results, but the method of application influenced short-term results [ ].
Arthroscopic application seems to provide faster rehabilitation, despite no significant differences being noted at 2 years follow-up. Gene therapy can provide some new answers to previously described pitfalls and limitations, but it might raise a different level of concern. The use of chondrocytes genetically transfected to increase the expression of BMP-7 inoculated into a fibrin—collagen scaffold provided better histological results as compared with controls rabbit model [ 18 ].
TERM applications have not only been attempted in focal defects but also in global joint degeneration, i. Joint replacement using biological tissue modified using TERM principles to mimic osteochondral tissue has been attempted [ ]. In addition, the use of synthetic materials e.
Concerning focal defects, a non-biological solution developed by van Dijk's group [ ] presented promising results by means of contoured focal metallic replacement figure 8 , despite the lack of mid- to long-term follow-up in larger series. An important issue regarding the applications of biomaterials is the implant—tissue interface. Considering the basic principles of TERM, besides biological conditions, ankle biomechanics must be taken into account [ 91 ] since it is a more congruent joint compared with the knee [ ]. A congruent joint surface, for example the ankle, is usually covered with thinner hyaline cartilage compared with incongruent ones that possess thicker cartilage, for example in the knee.
The diminishing of articular congruence produces higher contact pressure per joint area. Higher loss of congruence or malalignment will lead to growing contact pressure with all its implications [ 91 , , ]. Injured subchondral bone, as in OCDs, is less effective in supporting the overlying cartilage, and this might be one of the reasons explaining the greater difficulty for cartilage repair in these situations [ , ].
Also, Custers et al. In the case of biomaterials, owing to their biocompatibility, integration into the surrounding cartilage is usually observed [ ]. This way, the stress level changes on the joint are minor. However, the size and shape of the OCDs must be taken into account, to ensure that the biomaterial is as similar as possible, in order to completely fulfil the injured area.
The appropriate treatment for OCD repair is still controversial. The ideal technique would regenerate a tissue with biomechanical properties similar to normal hyaline articular cartilage, with reduced morbidity and costs. The excellent durability of results obtained by ACI or MACI over time is well established and contrasts sharply with the long-term results reported for bone-marrow-stimulating techniques such as abrasion, drilling or microfractures.
A variety of biomaterials including polymers and ceramics have been proposed for regeneration of the cartilage of OCDs, and composite scaffolds e. Up to now only a few clinical trials on ankle healing have been described, whereas a scaffold approach to the treatment of knee chondral lesions has been largely used in clinical practice, with excellent or good clinical results largely documented in the literature. New approaches must be considered to talus osteocondral defects in order to improve restoration. Although there are particularities of such area, other biomaterials with significant results in knee OCDs may be applied to the ankle lesions.
TERM approaches are changing the paradigms of medicine and surgical practice. However, the success of these technologies at present and in future demands deep knowledge of native tissue biology and understanding of its repair mechanisms and response to injury, as well as the new biomaterials under consideration. However, undiscriminating use of any promising technique is one of the most effective ways to impair or even block its proper development.
We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address. To read similar articles, check out our sister journal. Skip to main content. Van Dijk , J. Published 18 December Abstract Tissue engineering and regenerative medicine TERM has caused a revolution in present and future trends of medicine and surgery.
TERM applications on the ankle joint. Applications of tissue engineering and regenerative medicine strategies to skin repair Cutaneous ulcers around the ankle, secondary to trauma, vascular insufficiency or diabetes [ 20 , 21 ] are injuries that require special attention mainly owing to low vascular supply, a problem that is of great importance in poor subcutaneous tissue areas. Applications of tissue engineering and regenerative medicine strategies to tendon repair Another relevant group of injuries located in the ankle region is the tendon lesions.
Applications of tissue engineering and regenerative medicine strategies to bone repair Bone defects and bone reconstruction are, probably, two of the most important issues in a TERM perspective, with several proposals advanced over the years [ 7 , 29 , 53 , 62 , 63 ]. Osteochondral ankle lesions Osteochondral defects OCDs and osteoarthritis in lower limb have a relevant socio-economic impact with significant therapeutic investments and absence from work-related costs [ 80 , 81 ].
Applications of tissue engineering and regenerative medicine strategies to ankle osteochondral lesions repair 2. Applications of isolated growth factors Debridement and bone marrow stimulation have been used as surgical approaches for partially destroying the calcified zone that is often present in OCDs and to create multiple openings into the subchondral bone [ 87 , 89 ]. Applications of isolated cells MSCs have demonstrated their high potential for clinical use as therapeutic agents with several possible RM applications including orthopaedics and percutaneous injectable techniques [ 98 ].
Applications of biomaterials Hyaline cartilage serves as a low-friction surface with high wear resistance for weight-bearing joints. View inline View popup. Applications of advanced tissue engineering and regenerative medicine strategies The requirement for full OCD repair has been approached considering the heterogeneity of different tissues, different components and layers including subchondral bone plate and different hyaline cartilage layers.
Final considerations The appropriate treatment for OCD repair is still controversial. Science , — Cartilage 1 , — Engebretsen L , et al. Biomaterials 28 , — A 16 , — USA , — Zengerink M , van Dijk CN. Clinical efficacy of growth factors to enhance tissue repair in oral and maxillofacial reconstruction: Arthroscopy 26 , — Ruszczak Z , Friess W. Organs 11 , — Skin Wound Care 21 , — Sharma P , Maffulli N.
- Journal Rankings on Biomedical Engineering.
- 1. Introduction: fundamentals of tissue engineering and regenerative medicine.
- Selected Aspects of Fractional Brownian Motion (Bocconi & Springer Series);
- Challenges in tissue engineering!
- Pearl: A sweeping love story of 1920s Ireland.
Muscles Ligaments Tendons J. Kew SJ , et al. Lee JY , et al. A cell culture study. Pereira DR , et al. Biomaterials 30 , — Biomaterials 31 , — C 29 , — Enea D , et al. In vivo study in an ovine model. A 15 , —