Bone mimetic environments support engineering, propagation, and analysis of therapeutic response of patient-derived cells, ex vivo and in vivo

Bone metastases are the most common milestone in the lethal progression of prostate cancer and prominent in a substantial portion of renal malignancies. Interactions between cancer and bone host cells have emerged as drivers of both disease progression and therapeutic resistance. To best understand these central host-epithelial cell interactions, biologically relevant preclinical models are required. To achieve this goal, we here established and characterized tissue-engineered bone mimetic environments (BME) capable of supporting the growth of patient-derived xenograft (PDX) cells, ex vivo and in vivo. The BME consisted of a polycaprolactone (PCL) scaffold colonized by human mesenchymal stem cells (hMSCs) differentiated into osteoblasts. PDX-derived cells were isolated from bone metastatic prostate or renal tumors, engineered to express GFP or luciferase and seeded onto the BMEs. BMEs supported the growth and therapy response of PDX-derived cells, ex vivo. Additionally, BMEs survived after in vivo implantation and further sustained the growth of PDX-derived cells, their serial transplant, and their application to study the response to treatment. Taken together, this demonstrates the utility of BMEs in combination with patient-derived cells, both ex vivo and in vivo. STATEMENT OF SIGNIFICANCE: Our tissue-engineered BME supported the growth of patient-derived cells and proved useful to monitor the therapy response, both ex vivo and in vivo. This approach has the potential to enable co-clinical strategies to monitor bone metastatic tumor progression and therapy response, including identification and prioritization of new targets for patient treatment.

"Biological responses of two calcium-silicate-based cements on a tissue-engineered 3D organotypic deciduous pulp analogue"

OBJECTIVES

The biological responses of MTA and Biodentine™ has been assessed on a three-dimensional, tissue-engineered organotypic deciduous pulp analogue.

METHODS

Human endothelial (HUVEC) and dental mesenchymal stem cells (SHED) at a ratio of 3:1, were incorporated into a collagen I/fibrin hydrogel; succeeding Biodentine™ and MTA cylindrical specimens were placed in direct contact with the pulp analogue 48 h later. Cell viability/proliferation and morphology were evaluated through live/dead staining, MTT assay and Scanning Electron Microscopy (SEM), and expression of angiogenic, odontogenic markers through real time PCR.

RESULTS

Viable cells dominated at day 3 after treatment presenting typical morphology, firmly attached within the hydrogel structures, as shown by live/dead staining and SEM images. MTT assay at day 1 presented a significant increase of cell proliferation in Biodentine™ group. Real-time PCR showed significant upregulation of odontogenic markers DSPP, BMP-2 (day 3,6), RUNX2, ALP (day 3) in contact with Biodentine™ compared to MTA and the control, whereas MTA promoted significant upregulation of DSPP, BMP-2, RUNX2, Osterix (day 3) and ALP (day 6) compared to the control. MSX1 presented downregulation in both experimental groups. Expression of angiogenic markers VEGFa and ANGPT-1 at day 3 was significantly upregulated in contact with Biodentine™ and MTA respectively, while the receptors VEGFR1, VEGFR2 and Tie-2, as well as PECAM-1 were downregulated.

SIGNIFICANCE

Both calcium silicate-based materials are biocompatible and exert positive angiogenic and odontogenic effects, although Biodentine™ during the first days of culture, seems to induce higher cell proliferation and provoke a more profound odontogenic and angiogenic response from SHED.

3D bioprinted functional skeletal muscle models have potential applications for studies of muscle wasting in cancer cachexia

Acquired muscle diseases such as cancer cachexia are responsible for the poor prognosis of many patients suffering from cancer. In vitro models are needed to study the underlying mechanisms of those pathologies. Extrusion bioprinting is an emerging tool to emulate the aligned architecture of fibers while implementing additive manufacturing techniques in tissue engineering. However, designing bioinks that reconcile the rheological needs of bioprinting and the biological requirements of muscle tissue is a challenging matter. Here we formulate a biomaterial with dual crosslinking to modulate the physical properties of bioprinted models. We design 3D bioprinted muscle models that resemble the mechanical properties of native tissue and show improved proliferation and high maturation of differentiated myotubes suggesting that the GelMA-AlgMA-Fibrin biomaterial possesses myogenic properties. The electrical stimulation of the 3D model confirmed the contractile capability of the tissue and enhanced the formation of sarcomeres. Regarding the functionality of the models, they served as platforms to recapitulate skeletal muscle diseases such as muscle wasting produced by cancer cachexia. The genetic expression of 3D models demonstrated a better resemblance to the muscular biopsies of cachectic mouse models. Altogether, this biomaterial is aimed to fabricate manipulable skeletal muscle in vitro models in a non-costly, fast and feasible manner.

Stem cell and tissue engineering approaches in pressure ulcer treatment

CONTEXT

Pressure ulcers or injuries, arise from ischemic damage to soft tissues induced by unrelieved pressure over a bony prominence. They are usually difficult to treat with standard medical therapy and often they recur. In the search for better treatment options, promising alternative forms of treatment are today emerging. Within the field of regenerative medicine, ongoing research on advanced therapies seeks to develop medicinal products based on gene therapy, somatic cell therapy, tissue-engineering and combinations of these.

OBJECTIVE

The main objective is to perform an overview of experimental and clinical developments in somatic cell therapy and tissue engineering targeting the treatment of pressure injuries.

METHODS

Searching terms as "PRESSURE ULCER", "STEM CELL THERAPY", "TISSUE ENGINEERING" or "WOUND HEALING" were used in combination or alone, including publications refered to basic and clinical research and focusing on articles showing results obtained in a clinical context. A total of 80 references are cited, including 23 references published in the 3 last years.

RESULTS

The results suggest that this form of treatment could be an interesting option in patients with difficult-to-treat ulcers as spinal cord injury patients.

CONCLUSION

This field of regenerative medicine is very broad and further research is warranted.

Development of a 3D psoriatic skin model optimized for infiltration of IL-17A producing T cells: Focus on the crosstalk between T cells and psoriatic keratinocytes

Psoriasis is a chronic inflammatory skin disease involving several cell types, including T cells, via the IL-23/IL-17 axis. IL-17A acts on the surrounding epithelial cells thus resulting in an inflammatory feedback loop. The development of immunocompetent models that correctly recapitulate the complex phenotype of psoriasis remains challenging, which also includes both the T cell isolation and activation methods. The purpose of this work was to develop an advanced in vitro 3D psoriatic skin model that enables the study of the impact of T cells on psoriatic epithelial cells. To reach that aim, healthy and psoriatic fibroblasts and keratinocytes were used to reproduce this tissue-engineered skin model in which activated T cells, isolated beforehand from human whole blood, have been incorporated. Our study showed that isolation of T cells with the EasySep procedure, followed by activation with PMA/ionomycin, mimicked the psoriatic characteristics in an optimal manner with the production of inflammatory cytokines important in the pathogenesis of psoriasis, as well as increased expression of Ki67, S100A7, elafin and involucrin. This psoriatic model enriched in activated T cells displayed enhanced production of IL-17A, IFN-ƴ, CCL2, CXCL10, IL-1ra, IL-6 and CXCL8 compared with the healthy model and whose increased secretion was maintained over time. In addition, anti-IL17A treatment restored some psoriatic features, including epidermal thickness and basal keratinocytes proliferation, as well as a downregulation of S100A7, elafin and involucrin expression. Altogether, our study demonstrated that this model reflects a proper psoriatic inflammatory environment and is effective for the investigation of epidermal and T cell interaction over time. STATEMENT OF SIGNIFICANCE: The aim of this study was to provide an innovative 3D immunocompetent human psoriatic skin model. To our knowledge, this is the first immunocompetent model that uses skin cells from psoriatic patients to study the impact of IL-17A on pathological cells. Through the use of this model, we demonstrated that the T-cell enriched psoriatic model differs from T-cell enriched healthy model, highlighting efficient crosstalk between pathologic epithelial cells and T cells. This advanced preclinical model further mimics the original psoriatic skin and will prove relevant in predicting clinical outcomes, thereby decreasing inaccurate predictions of compound effects.

Cell-laden injectable microgels: Current status and future prospects for cartilage regeneration

Injectable hydrogels have been employed extensively as versatile materials for cartilage regeneration due to their excellent biocompatibility, tunable structure, and ability to accommodate bioactive factors, as well as their ability to be locally delivered via minimally invasive injection to fill irregular defects. More recently, in vitro and in vivo studies have revealed that processing these materials to produce cell-laden microgels can enhance cell-cell and cell-matrix interactions and boost nutrient and metabolite exchange. Moreover, these studies have demonstrated gene expression profiles and matrix regeneration that are superior compared to conventional injectable bulk hydrogels. As cell-laden microgels and their application in cartilage repair are moving closer to clinical translation, this review aims to present an overview of the recent developments in this field. Here we focus on the currently used biomaterials and crosslinking strategies, the innovative fabrication techniques being used for the production of microgels, the cell sources used, the signals used for induction of chondrogenic differentiation and the resultant biological responses, and the ability to create three-dimensional, functional cartilage tissues. In addition, this review also covers the current clinical approaches for repairing cartilage as well as specific challenges faced when attempting the regeneration of damaged cartilage tissue. New findings related to the macroporous nature of the structures formed by the assembled microgel building blocks and the novel use of microgels in 3D printing for cartilage tissue engineering are also highlighted. Finally, we outline the challenges and future opportunities for employing cell-laden microgels in clinical applications.

Biological action of docosahexaenoic acid in a 3D tissue-engineered psoriatic skin model: Focus on the PPAR signaling pathway

N-3 polyunsaturated fatty acids (n-3 PUFAs), and in particular docosahexaenoic acid (DHA), have many beneficial metabolic effects, including reducing epidermal thickness in patients with psoriasis. The positive impacts of DHA in psoriasis could be mediated by its interactions with the PPAR signaling pathway, as well as by its secretion of anti-inflammatory bioactive metabolites, but the detailed metabolism is still not understood. In the present study, we evaluated the influence of DHA on the main features of psoriasis and its effects on the PPAR signaling pathway, in a psoriatic in vitro skin model. Healthy and psoriatic skin substitutes were produced according to the tissue-engineered self-assembly method, using culture media supplemented with 10 μM of DHA. The presence of DHA led to a reduction in the abnormal cell differentiation of psoriatic keratinocytes, seen in the increased expression of filaggrin and keratin 10. DHA was incorporated into the membrane phospholipids of the epidermis and transformed principally into eicosapentaenoic acid (EPA). Furthermore, the addition of DHA into the culture medium led to a decrease in the levels of lipid mediators derived from n-6 PUFAs, mainly prostaglandin E₂ (PGE₂) and 12-hydroxyeicosatetraenoic acid (12-HETE). Finally, DHA supplementation rebalanced the expression of PPAR receptors and caused a decrease in the secretion of TNF-α. Altogether, our results show that DHA possesses the ability to attenuate the psoriatic characteristics of psoriatic skin substitutes, mostly by restoring epidermal cell differentiation and proliferation, as well as by reducing inflammation.

Esophagus tissue engineering: from decellularization to in vivo recellularization in two sites

To produce an esophageal scaffold with suitable features and evaluate the result of in vivo cell seeding after its implantation in the omentum and near its original anatomical position in the rat model. The esophagus of twelve rats were resected, cannulated, and decellularized via a peristaltic pump. After confirmation of decellularization and preservation of extracellular matrix, decellularized scaffolds were implanted either in the abdominal cavity (group I, n = 6) or cervical area (group II, n = 6). Histological evaluations were performed after 3 and 6 months of implantation. The results of histological evaluations, scanning electron microscopy, and the tensile test confirmed the maintenance of extracellular matrix and removal of all cellular constituents. At the time of biopsy, no evidence of inflammation was detected and the implanted scaffolds appeared normal. Histopathological evaluations of implanted tissues revealed that undifferentiated cells were seen in scaffolds of all follow-ups in both groups. Epithelial cell seeding was more advanced in biopsies of group II obtained after 6 months of operation and was accompanied by angiogenesis in surrounding adventitia. It seems that the implantation of scaffold near its original place may have an important role in further cell seeding. This method may be surpassing in comparison with traditional implantation techniques for perfecting esophageal transplantation.

In vitro models of the human heart

Cardiac congenital disabilities are the most common organ malformations, but we still do not understand how they arise in the human embryo. Moreover, although cardiovascular disease is the most common cause of death globally, the development of new therapies is lagging compared with other fields. One major bottleneck hindering progress is the lack of self-organizing human cardiac models that recapitulate key aspects of human heart development, physiology and disease. Current in vitro cardiac three-dimensional systems are either engineered constructs or spherical aggregates of cardiomyocytes and other cell types. Although tissue engineering enables the modeling of some electro-mechanical properties, it falls short of mimicking heart development, morphogenetic defects and many clinically relevant aspects of cardiomyopathies. Here, we review different approaches and recent efforts to overcome these challenges in the field using a new generation of self-organizing embryonic and cardiac organoids.

A novel synthetic approach to produce cellulose-based woven scaffolds impregnated with bioactive glass for bone regeneration

Tissue-engineering has become the best alternative solution for replacing the damaged tissues. However, the cost of scaffold materials is still a big challenge, so the development of cost-effective scaffolds is highly encouraged. In this research, different types of cotton textile-scaffolds as a cellulosic material were developed to be utilized as a substrate for cells proliferation. They were loaded with bioactive glass (BG) doped with silver nanoparticles (AgNPs). The effect of the loaded materials on the physicochemical and mechanical characteristics of the cellulosic textile scaffolds was investigated by means of FTIR, contact angle, physical and mechanical properties of the cotton fabrics, in addition to assessing their antimicrobial activity. Moreover, the biomineralization was evaluated after soaking in Simulated Body Fluid (SBF) using ICP and SEM accessorized with EDX. Cells proliferation capacities of the developed cellulosic woven-scaffolds were assessed against MG63 cell line at different incubation times. The physicochemical and mechanical features of these fabrics demonstrated a positive influence for the existence of BG impregnation, especially those doped with AgNPs. The antimicrobial features were also affirmed for the cellulosic scaffolds. More pronounced influence was observed on the biomineralization of the scaffold impregnated with BG doped with 0.5% Ag. The percentages of proliferated cells were very close to negative control (100% ± 10). This approach offers a novel and affordable alternative cellulosic woven-scaffolds for bone regeneration.

Management of urinary and bowel dysfunction in rabbit model of spinal cord injury using Schwann cells and muscle progenitors: functional study and evidence for novel mechanism of action

PURPOSE

We tried to investigate the role of Schwann and satellite cells in the treatment of neurogenic bladder and bowel dysfunction; following spinal cord injury in the rabbit model.

METHODS

Twelve male New Zealand rabbits underwent induction of neurogenic bladder by spinal cord injury. Rabbits underwent the fiber tractography analysis to confirm the induction of spinal cord injury. Then, animals were randomly divided into two groups. In group I (n = 4), Schwann cells were obtained from autologous peroneal nerve. In group II (n = 4), the co-culture of nerve-muscle cells was obtained from autologous peroneal nerve and quadriceps muscle. Animals in the control group (n = 4) did not undergo any rehabilitation therapy. One and 4 months after injection of cells into the external anal sphincter, electromyography, urethral pressure profiles, urodynamic studies, voiding cystourethrogram, and manometry was performed to confirm the efficacy of treatment in short- (1 month) and long-term (4 months) follow-ups.

RESULTS

The investigations validated that no statistically significant difference was detected between the two experimental groups in a short-term follow-up (p-value > 0.05). However, the functional features were improved in group II in long-term follow-up. In both groups, the external anal sphincter contracted in response to electrical signals delivered to the muscle. However, more signals were detected in group II in electromyography evaluation. The immunohistochemical staining demonstrated that the histological features of the bladder and spinal cord were more satisfactory in group II in all follow-ups compared to group I, in terms of less edema, inflammation, presence of progenitor cells, and expression of muscle and nerve markes.

CONCLUSION

Our results suggested that the injection of nerve-muscle co-culture cells into the external anal sphincter may be a helpful tactic for ameliorating the urological complications; following spinal cord injury induction in the rabbit model.

Recellularization of testicular feminization testis in C57bl6 as a natural bioreactor for creation of cellularized seminiferous tubules: an experimental study

We determined histological aspects of implanted human decellularized testicular matrix (DTM) in C57BL6 as a primitive step for further testis tissue engineering. A total of 4 immature human testicles were obtained after bilateral orchiectomy from patients with testicular feminization syndrome. The optimal decellularization protocol was determined and the efficacy of decellularization was evaluated in two of the testicles. The remaining scaffolds were cut in 3 × 3 mm³ pieces and implanted between the tight muscles in 32 C57BL6. Biopsies were taken at 2, 4, 8, and 24 weeks postoperatively and stained with PLZF, protamine, and tekt1 markers. Histological examination of DTMs confirmed complete absence of nuclear remnants and preservation of the extracellular matrix. Successful cell seeding was observed in all follow-ups confirmed by H&E and IHC staining that increased continuously during the whole study. Interestingly, spermatogonial stem-like cells were observed on decellularized implants that were well differentiated during the follow-ups. Natural bioreactors may provide a good cell source for testes tissue regeneration. This technique may provide testis bioscaffold as a three-dimensional platform and further successful cell seeding to produce a functional testis. This novel technique may be beneficial for patients who require testicular supplementation.

Designing a novel vacuum aspiration system to decellularize large-size enthesis with preservation of physicochemical and biological properties

Background

Functional and rapid enthesis regeneration remains a challenge after arthroscopic rotator cuff (RC) repair. Tissue-engineering a large-size biomimetic scaffold may be an adjuvant strategy to improve this clinical dilemma. Herein, we developed an optimized protocol to decellularize large-size enthesis as scaffolds for augmenting RC tear.

Methods

A novel vacuum aspiration system (VAS) was set up, which can provide a negative pressure to suck out cellular substances from tissue blocks without using chemical detergents. Large-size enthesis tissue specimens were harvested from canine infraspinatus tendon (IT) insertion, and then decellularized with an optimized protocol [freeze-thaw processing followed by nuclease digestion and phosphate buffer saline (PBS) rinsing in the custom-designed VAS], or a conventional protocol (freeze-thaw processing followed by nuclease digestion and PBS rinsing), thus fabricating two kinds of acellular enthesis matrix (AEM), namely C-AEM and O-AEM. After that, the C-AEM and O-AEM were comparatively evaluated from the aspect of their physicochemical and biological properties.

Results

Physiochemically, the O-AEM preserved the morphologies, ingredients, and tensile properties much better than the C-AEM. Biologically, in vitro studies demonstrated that both C-AEM and O-AEM show no cytotoxicity and low immunogenicity, which could promote stem cells attachment and proliferation. Interestingly, O-AEM showed better region-specific inducibility on the interacted stem cell down osteogenic, chondrogenic and tenogenic lineages compared with C-AEM. Additionally, using a canine IT repair model, the injured enthesis patched with O-AEM showed a significant improvement compared with the injured enthesis patched with C-AEM or direct suture histologically.

Conclusions

The proposed VAS may help us fabricate large-size AEM with good physicochemical and biological properties, and this AEM may have potential clinical applications in patching large/massive RC tear.

Tissue engineered ultra-thin descemet stripping corneal endothelial layers using porcine cornea and stem cells

Due to their very poor proliferative capacity, the dysfunction of corneal endothelial cells can sometimes lead to incurable eye diseases that require corneal transplantation. Although many studies have been performed to reconstruct corneal endothelial cells, corneal transplantation is still considered to be the established approach. In this study, we developed bio-engineered Descemet stripping endothelial (DSE) layers, using porcine cornea and induced pluripotent stem cell (iPSC)-derived corneal endothelial cells (iCECs). First, we optimized a protocol to prepare an ultra-thin and decellularized Descemet stripping (DS) scaffold from porcine cornea. Our DS layers show over 90% transparency compared to the control. Porcine-derived cells and xenogenic antigens disappeared, whereas the collagen matrix remained in the graft. Next, corneal endothelial cell lines or iCECs were seeded on the decellularized DS graft and cultured for 7 days. The drying method reduced graft rolling and edema, and increased transparency during culture. The reseeded cells were evenly distributed over the graft, and most of the cells survived. Although future clinical studies are warranted, engineered DSE tissues using xenogenic tissues and stem cells will be useful tools for the treatment of incurable corneal diseases.

Mucoadhesive emulgel systems containing curcumin for oral squamous cell carcinoma treatment: From pre-formulation to cytotoxicity in tissue-engineering oral mucosa

Current oral squamous cell carcinoma chemotherapies demonstrate off-target toxicity, which could be reduced by local delivery. Curcumin acts via many cellular targets to give anti-cancer properties; however the bioavailability is hindered by its physicochemical characteristics. The incorporation of curcumin into emulgel systems could be a promising approach for its solubilization and delivery. The aim of this work was to develop emulgel systems containing curcumin for the treatment of oral cancer. The emulgels containing curcumin were prepared with poloxamer 407, acrylic acid derivatives, oil phase (sesame oil or isopropyl myristate). The more stable system was evaluated for mechanical and rheological properties, as well as, the in vitro drug release profile, permeation and cytotoxic potential to oral mucosa models. The flow-throw system evidenced that the formulations could keep 5 min over porcine oral mucosa. Emulgel showed pseudoplastic behavior and a gelation temperature of 33 °C, which ensure their higher consistency. In addition, 70% of the incorporated curcumin was released within 24 h in an in vitro drug release study and could permeate porcine oral mucosa. Monolayers cultures and tissue-engineered models showed the selectivity of the drug and systems for tumor cells. The physicochemical properties, subsequent release and permeation of curcumin to selectivity kill cancer cells could be improved by the incorporation into emulgel systems.

Long-term observation of airway reconstruction using decellularized tracheal allografts in micro-miniature pigs at growing stage

Introduction

Decellularized tissue exhibits cell matrix-like properties, along with reduced antigenicity. We explored the potential of decellularized allogeneic trachea to restore the upper respiratory tract, focusing on pediatric application. This study specifically aimed at long-term observation of tissue regeneration using a micro-miniature pig model.

Methods

Artificial defects (15 × 15 mm) in the subglottis and trachea of micro-miniature pigs were repaired by transplantation of either allogeneic decellularized or fresh (control) tracheal patches. Pigs were evaluated in situ, by bronchoscopy, every three months, and sacrificed for histological examination at six and twelve months after transplantation.

Results

No airway symptom was observed in any pig during the observation period. Bronchoscopy revealed the tracheal lumen to be restored by fresh grafts, showing an irregular surface with remarkable longitudinal compression; these changes were mild after restoration with decellularized grafts. Histologically, while fresh graft patches were denatured and replaced by calcified tissue, decellularized patches remained unchanged throughout the observation period. There were regeneration foci of cartilage adjacent to the grafts, and some foci joined the decellularized graft uniformly, suggesting the induction of tracheal reconstitution.

Conclusion

Allogeneic decellularized tracheal tissue could serve as a promising biomaterial for tracheal restoration, especially for pediatric patients at the growing stage.

Preclinical models for neuroblastoma: Advances and challenges

Neuroblastoma is a paediatric cancer of the sympathetic nervous system and the most common solid tumour of infancy, contributing to 15% of paediatric oncology deaths. Current therapies are not effective in the long-term treatment of almost 80% of patients with this clinically aggressive disease. The primary challenge in the identification and validation of new agents for paediatric drug development is the accurate representation of tumour biology and diversity. In addition to this limitation, the low incidence of neuroblastoma makes the recruitment of eligible patients for early phase clinical trials highly challenging and highlights the need for robust preclinical testing to ensure that the best treatments are selected. The research field requires new preclinical models, technologies, and concepts to tackle these problems. Tissue engineering offers attractive tools to assist in the development of three-dimensional (3D) cell models using various biomaterials and manufacturing approaches that recreate the geometry, mechanics, heterogeneity, metabolic gradients, and cell communication of the native tumour microenvironment. In this review, we discuss current experimental models and assess their abilities to reflect the structural organisation and physiological conditions of the human body, in addition to current and new techniques to recapitulate the tumour niche using tissue-engineered platforms. Finally, we will discuss the possible use of novel 3D in vitro culture systems to address open questions in neuroblastoma biology.

Interfacing cells with microengineered scaffolds for neural tissue reconstruction

The development of cellular microenvironments suitable for neural tissue engineering purposes involves a plethora of research fields ranging from cell biology to biochemistry, neurosciences, physics, nanotechnology, mechanobiology. In the last two decades, this multi-disciplinary activity has led to the emergence of numerous strategies to create architectures capable of reproducing the topological, biochemical and mechanical properties of the extracellular matrix present in the central (CNS) and peripheral nervous system (PNS). Some of these approaches have succeeded in inducing the functional recovery of damaged areas in the CNS and the PNS to address the current lack of effective medical treatments for this type of injury. In this review, we analyze recent developments in the realization of two-dimensional and three-dimensional neuronal scaffolds following either top-down or bottom-up approaches. After providing an overview of the different fabrication techniques employed for tailoring the biomaterials, we draw on specific examples to describe the major features of the developed approaches. We then conclude with prospective proof of concept studies on guiding scaffolds and regenerative models on macro-scale brain implants targeting neural regeneration.

Reconstruction of the pulmonary artery by a novel biodegradable conduit engineered with perinatal stem cell-derived vascular smooth muscle cells enables physiological vascular growth in a large animal model of congenital heart disease

Lack of growth potential of available grafts represents a bottleneck in the correction of congenital heart defects. Here we used a swine small intestinal submucosa (SIS) graft functionalized with mesenchymal stem cell (MSC)-derived vascular smooth muscle cells (VSMCs), for replacement of the pulmonary artery in piglets.

MSCs were expanded from human umbilical cord blood or new-born swine peripheral blood, seeded onto decellularized SIS grafts and conditioned in a bioreactor to differentiate into VSMCs. Results indicate the equivalence of generating grafts engineered with human or swine MSC-derived VSMCs. Next, we conducted a randomized, controlled study in piglets (12–15 kg), which had the left pulmonary artery reconstructed with swine VSMC-engineered or acellular conduit grafts. Piglets recovered well from surgery, with no casualty and similar growth rate in either group. After 6 months, grafted arteries had larger circumference in the cellular group (28.3 ± 2.3 vs 18.3 ± 2.1 mm, P < 0.001), but without evidence of aneurism formation. Immunohistochemistry showed engineered grafts were composed of homogeneous endothelium covered by multi-layered muscular media, whereas the acellular grafts exhibited a patchy endothelial cell layer and a thinner muscular layer.

Results

show the feasibility and efficacy of pulmonary artery reconstruction using clinically available grafts engineered with allogeneic VSMCs in growing swine.

Benchmarking in vitro tissue-engineered blood-brain barrier models

The blood–brain barrier (BBB) plays a key role in regulating transport into and out of the brain. With increasing interest in the role of the BBB in health and disease, there have been significant advances in the development of in vitro models. The value of these models to the research community is critically dependent on recapitulating characteristics of the BBB in humans or animal models. However, benchmarking in vitro models is surprisingly difficult since much of our knowledge of the structure and function of the BBB comes from in vitro studies. Here we describe a set of parameters that we consider a starting point for benchmarking and validation. These parameters are associated with structure (ultrastructure, wall shear stress, geometry), microenvironment (basement membrane and extracellular matrix), barrier function (transendothelial electrical resistance, permeability, efflux transport), cell function (expression of BBB markers, turnover), and co-culture with other cell types (astrocytes and pericytes). In suggesting benchmarks, we rely primarily on imaging or direct measurements in humans and animal models.

Recent Trends in the Fabrication of Starch Nanofibers: Electrospinning and Non-electrospinning Routes and Their Applications in Biotechnology

Electrospinning a versatile and the most preferred technique for the fabrication of nanofibers has revolutionized by opening unlimited avenues in biomedical fields. Presently, the simultaneous functionalization and/or post-modification of as-spun nanofibers with biomolecules has been explored, to serve the distinct goals in the aforementioned field. Starch is one of the most abundant biopolymers on the earth. Besides, being biocompatible and biodegradable in nature, it has unprecedented properties of gelatinization and retrogradation. Therefore, starch has been used in numerous ways for wide range of applications. Keeping these properties in consideration, the present article summarizes the recent expansion in the fabrication of the pristine/modified starch-based composite scaffolds by electrospinning along with their possible applications. Apart from electrospinning technique, this review will also provide the comprehensive information on various other techniques employed in the fabrication of the starch-based nanofibers. Furthermore, we conclude with the challenges to be overcome in the fabrication of nanofibers by the electrospinning technique and future prospects of starch-based fabricated scaffolds for exploration of its applications.

Enhanced wound healing of tissue-engineered human corneas through altered phosphorylation of the CREB and AKT signal transduction pathways

The cornea is a transparent organ, highly specialized and unique that is continually subjected to abrasive forces and occasional mechanical or chemical trauma because of its anatomical localization. Upon injury, the extracellular matrix (ECM) rapidly changes to promote wound healing through integrin-dependent activation of specific signal transduction mediators whose contribution is to favor faster closure of the wound by altering the adhesive and migratory properties of the cells surrounding the damaged area. In this study, we exploited the human tissue-engineered cornea (hTECs) as a model to study the signal transduction pathways that participate to corneal wound healing. By exploiting both gene profiling and activated kinases arrays, we could demonstrate the occurrence of important alterations in the level of expression and activation of a few mediators from the PI3K/Akt and CREB pathways in response to the ECM remodeling taking place during wound healing of damaged hTECs. Pharmacological inhibition of CREB with C646 considerably accelerated wound closure compared to controls. This process was considerably accelerated further when both C646 and SC79, an Akt agonist, were added together to wounded hTECs. Therefore, our study demonstrate that proper corneal wound healing requires the activation of Akt together with the inhibition of CREB and that wound healing in vitro can be altered by the use of pharmacological inhibitors (such as C646) or agonists (such as SC79) of these mediators.

STATEMENT OF SIGNIFICANCE

Corneal wounds account for a large proportion of all visual disabilities in North America. To our knowledge, this is the first time that a tissue-engineered human cornea (hTEC) entirely produced using normal untransformed human cells is used as a biomaterial to study the signal transduction pathways that are critical to corneal wound healing. Through the use of this biomaterial, we demonstrated that human corneal epithelial cells engaged in wound healing reduce phosphorylation of the signal transduction mediator CREB while, in the mean time, they increase that of AKT. By increasing the activation of AKT together with a decrease in CREB activation, we could considerably reduce wound closure time in our punch-damaged hTECs. Considering the increasing interest given to the reconstruction of different types of tissues, we believe these results will have a strong impact on the field of tissue-engineering and biomaterials. Altering the activation status of the Akt and CREB proteins might prove to be a therapeutically interesting avenue and may also find applications in wound healing of other tissues beside the cornea, such as the skin.

Puncturing of lyophilized tissue engineered vascular matrices enhances the efficiency of their recellularization

Data on in vitro engineered "off the shelf" matrices support the concept of endogenous cellular repopulation driving the graft's remodeling via immune-mediated response. This seems important to further accelerate the cell reconstitution and may play a crucial role when mononuclear cells are used. Nevertheless, studies on decellularized xenogeneic grafts showed only limited host cell repopulation post-implantation. This study aims at a systematic comparison of reseeding methods (dripping, injection, bathing in a cell suspension and combined puncturing-dripping method) to define the most efficient technique enhancing recellularization of tissue engineered vascular matrices (patches, vessels, small diameter and standard size valves) prior implantation. The constructs were analyzed histologically, biochemically and biomechanically. Various preconditioning treatments (wet, lyophilized and air-dried) combined with reseeding methods demonstrated the highest cell loading efficiency, despite applied crimping and flow stress, of lyophilization followed by puncturing-dripping technique. This novel seeding method allows for an efficient, time-saving graft reseeding that can be used within a one-step cardiovascular clinical intervention.

STATEMENT OF SIGNIFICANCE

The concept of living tissue engineered, self-repairing, autologous cardiovascular replacements, was proposed alternatively to existing synthetic/xenogeneic prostheses. Recent studies in animal models demonstrate faster in vivo recellularization after grafts pre-seeding with cells prior implantation. Pre-seeded cells hold either, the ability to differentiate directionally or attract host cells, crucial for graft integration and remodeling. It is unclear, however, how efficient the pre-loading is and how well cells withstand the flow. The study presents a systematic overview of cell loading techniques of different cardiovascular constructs, tested under static and dynamic conditions. Comparison illustrates a significantly higher efficiency of cells loading in lyophilized tissues punctured before their standard seeding. This technique may beneficially accelerate remodeling of cardiovascular grafts in further in vivo studies.

Functional brain-specific microvessels from iPSC-derived human brain microvascular endothelial cells: the role of matrix composition on monolayer formation

BACKGROUND

Transwell-based models of the blood-brain barrier (BBB) incorporating monolayers of human brain microvascular endothelial cells (dhBMECs) derived from induced pluripotent stem cells show many of the key features of the BBB, including expression of transporters and efflux pumps, expression of tight junction proteins, and physiological values of transendothelial electrical resistance. The fabrication of 3D BBB models using dhBMECs has so far been unsuccessful due to the poor adhesion and survival of these cells on matrix materials commonly used in tissue engineering.

METHODS

To address this issue, we systematically screened a wide range of matrix materials (collagen I, hyaluronic acid, and fibrin), compositions (laminin/entactin), protein coatings (fibronectin, laminin, collagen IV, perlecan, and agrin), and soluble factors (ROCK inhibitor and cyclic adenosine monophosphate) in 2D culture to assess cell adhesion, spreading, and barrier function.

RESULTS

Cell coverage increased with stiffness of collagen I gels coated with collagen IV and fibronectin. On 7 mg mL^-1 collagen I gels coated with basement membrane proteins (fibronectin, collagen IV, and laminin), cell coverage was high but did not reliably reach confluence. The transendothelial electrical resistance (TEER) on collagen I gels coated with basement membrane proteins was lower than on coated transwell membranes. Agrin, a heparin sulfate proteoglycan found in basement membranes of the brain, promoted monolayer formation but resulted in a significant decrease in transendothelial electrical resistance (TEER). However, the addition of ROCK inhibitor, cAMP, or cross-linking the gels to increase stiffness, resulted in a significant improvement of TEER values and enabled the formation of confluent monolayers.

CONCLUSIONS

Having identified matrix compositions that promote monolayer formation and barrier function, we successfully fabricated dhBMEC microvessels in cross-linked collagen I gels coated with fibronectin and collagen IV, and treated with ROCK inhibitor and cAMP. We measured apparent permeability values for Lucifer yellow, comparable to values obtained in the transwell assay. During these experiments we observed no focal leaks, suggesting the formation of tight junctions that effectively block paracellular transport.

Bone regeneration using composite non-demineralized xenogenic dentin with beta-tricalcium phosphate in experimental alveolar cleft repair in a rabbit model

Background

Alveolar cleft repair is performed via bone grafting procedure to restore the dental arch continuity. A suitable bone substitute materials should possess osteoinductive and osteoconductive properties, to promote new bone formation, along with a slowly resorbable scaffold that is subsequently replaced with functionally viable bone. Calcium phosphate biomaterials have long proved their efficacy as bone replacement materials. Dentin in several forms has also demonstrated its possibility to be used as bone graft replacement material in several studies. The purpose of this study was to evaluate bone regeneration pattern and quantify bone formation after grafting pre-established experimental alveolar clefts defects model in rabbits using composite xenogenic dentin and β-TCP in comparison to β-TCP alone.

Methods

Unilateral alveolar cleft defects were created in 16 New Zealand rabbits according to previously described methodology. Alveolar clefts were allowed 8 weeks healing period. 8 defects were filled with β-TCP, whereas 8 defects filled with composite xenogenic dentin with β-TCP. Bone regeneration of the healed defects was compared at the 8 weeks after intervention. Quantification of bone formation was analyzed using micro-computed tomography (µCT) and histomorphometric analysis.

Results

µCT and histomorphometric analysis revealed that defects filled with composite dentin/β-TCP showed statistically higher bone volume fraction, bone mineral density and percentage residual graft volume when compared to β-TCP alone. An improved surgical handling of the composite dentin/β-TCP graft was also noted.

Conclusions

Composite xenogenic dentin/β-TCP putty expresses enhanced bone regeneration compared to β-TCP alone in the reconstruction of rabbit alveolar clefts defects.

Airway reconstruction using decellularized tracheal allografts in a porcine model

PURPOSE

Tracheal cartilage reconstruction is an essential approach for the treatment of tracheal congenital abnormalities or injury. Here, we evaluated the use of allogeneic decellularized tracheas as novel support scaffolds.

METHODS

Six weaned pigs (4-week-old domestic males) were transplanted with allogeneic tracheal graft patches (three decellularized and three fresh tracheal scaffolds) onto artificial defects (approximately 15 × 15 mm). After 11 weeks, the tracheas were evaluated by bronchoscopy and histological studies.

RESULTS

No pigs displayed airway symptoms during the observation period. Tracheal lumen restored by fresh graft patches showed more advanced narrowing than that treated with decellularized grafts by bronchoscopy. Histologically, fresh grafts induced typical cellular rejection; this was decreased with decellularized grafts. In addition, immunohistochemistry demonstrated regenerating foci of recipient cartilage along the adjacent surface of decellularized tracheal grafts.

CONCLUSION

Decellularized allogeneic tracheal scaffolds could be effective materials for restoring impaired trachea.

Online quantitative monitoring of live cell engineered cartilage growth using diffuse fiber-optic Raman spectroscopy

Tissue engineering (TE) has the potential to improve the outcome for patients with osteoarthritis (OA). The successful clinical translation of this technique as part of a therapy requires the ability to measure extracellular matrix (ECM) production of engineered tissues in vitro, in order to ensure quality control and improve the likelihood of tissue survival upon implantation. Conventional techniques for assessing the ECM content of engineered cartilage, such as biochemical assays and histological staining are inherently destructive. Raman spectroscopy, on the other hand, represents a non-invasive technique for in situ biochemical characterization. Here, we outline current roadblocks in translational Raman spectroscopy in TE and introduce a comprehensive workflow designed to non-destructively monitor and quantify ECM biomolecules in large (>3 mm), live cell TE constructs online. Diffuse near-infrared fiber-optic Raman spectra were measured from live cell cartilaginous TE constructs over a 56-day culturing period. We developed a multivariate curve resolution model that enabled quantitative biochemical analysis of the TE constructs. Raman spectroscopy was able to non-invasively quantify the ECM components and showed an excellent correlation with biochemical assays for measurement of collagen (R2 = 0.84) and glycosaminoglycans (GAGs) (R2 = 0.86). We further demonstrated the robustness of this technique for online prospective analysis of live cell TE constructs. The fiber-optic Raman spectroscopy strategy developed in this work offers the ability to non-destructively monitor construct growth online and can be adapted to a broad range of TE applications in regenerative medicine toward controlled clinical translation.

Tissue-engineered human 3D model of bladder cancer for invasion study and drug discovery

The tumour microenvironment is critical to both the initiation and maintenance of tumorigenesis. Reconstitution of the microenvironment is a major challenge for in vitro cancer models. Indeed, conventional 2D culture systems cannot replicate the complexity, diversity and dynamic nature of the tumour microenvironment. In this study, we have developed a 3D endotheliazed vesical equivalent by using tissue engineering from primary human cells in which non-invasive or invasive bladder cancer (BCa) cell lines, cultured as compact spheroids, were incorporated. Invasive BCa cells cross the basement membrane and invade the stromal compartment whereas non-invasive BCa cells are confined to the urothelium. Our 3D BCa model could be used as a reliable model for assessing drug responses, potentially reducing or partially replacing animal experiments, and thus should have applications in the identification of novel targets as well as toxicological evaluation of anti-cancer therapies.

Comparative assessment of intrinsic mechanical stimuli on knee cartilage and compressed agarose constructs

A well-established cue for improving the properties of tissue-engineered cartilage is mechanical stimulation. However, the explicit ranges of mechanical stimuli that correspond to favorable metabolic outcomes are elusive. Usually, these outcomes have only been associated with the applied strain and frequency, an oversimplification that can hide the fundamental relationship between the intrinsic mechanical stimuli and the metabolic outcomes. This highlights two important key issues: the firstly is related to the evaluation of the intrinsic mechanical stimuli of native cartilage; the second, assuming that the intrinsic mechanical stimuli will be important, deals with the ability to replicate them on the tissue-engineered constructs. This study quantifies and compares the volume of cartilage and agarose subjected to a given magnitude range of each intrinsic mechanical stimulus, through a numerical simulation of a patient-specific knee model coupled with experimental data of contact during the stance phase of gait, and agarose constructs under direct-dynamic compression. The results suggest that direct compression loading needs to be parameterized with time-dependence during the initial culture period in order to better reproduce each one of the intrinsic mechanical stimuli developed in the patient-specific cartilage. A loading regime which combines time periods of low compressive strain (5%) and frequency (0.5Hz), in order to approach the maximal principal strain and fluid velocity stimulus of the patient-specific cartilage, with time periods of high compressive strain (20%) and frequency (3Hz), in order to approach the pore pressure values, may be advantageous relatively to a single loading regime throughout the full culture period.

A rabbit model for experimental alveolar cleft grafting

Objectives

The purpose of the present study was to develop an animal model for creating alveolar cleft defects with properly simulated clinical defect environment for tissue-engineered bone-substitute materials testing without compromising the health of the animal. Cleft creation surgery was aimed at creating a complete alveolar cleft with a wide bone defect with an epithelial lining (oral mucosa) overlying the cleft defect.

Methods

A postmortem skull of a New Zealand White (NZW) rabbit skull (Oryctolagus cuniculus) underwent an osteological and imaging survey. A pilot postmortem surgery was conducted to confirm the feasability of a surgical procedure and the defect was also radiologically confirmed and illustrated with micro-computed tomography. Then, a surgical in vivo model was tested and evaluated in 16 (n = 16) 8-week-old NZW rabbits to create in vivo alveolar cleft creation surgery.

Results

Clinical examination and imaging analysis 8 weeks after cleft creation surgery revealed the establishment of a wide skeletal defect extending to the nasal mucosa simulating alveolar clefts in all of the rabbits.

Conclusions

Our surgical technique was successful in creating a sizable and predictable model for bone grafting material testing. The model allows for simulating the cleft site environment and can be used to evaluate various bone grafting materials in regard to efficacy of osteogenesis and healing potential without compromising the health of the animal.

The Role of the Lysyl Oxidases in Tissue Repair and Remodeling: A Concise Review

Tissue injury provokes a series of events containing inflammation, new tissue formation and tissue remodeling which are regulated by the spatially and temporally coordinated organization. It is an evolutionarily conserved, multi-cellular, multi-molecular process via complex signalling network. Tissue injury disorders present grievous clinical problems and are likely to increase since they are generally associated with the prevailing diseases such as diabetes, hypertension and obesity. Although these dynamic responses vary not only for the different types of trauma but also for the different organs, a balancing act between the tissue degradation and tissue synthesis is the same. In this process, the degradation of old extracellular matrix (ECM) elements and new ones' synthesis and deposition play an essential role, especially collagens. Lysyl oxidase (LOX) and four lysyl oxidase-like proteins are a group of enzymes capable of catalyzing cross-linking reaction of collagen and elastin, thus initiating the formation of covalent cross-links that insolubilize ECM proteins. In this way, LOX facilitates ECM stabilization through ECM formation, development, maturation and remodeling. This ability determines its potential role in tissue repair and regeneration. In this review, based on the current in vitro, animal and human in vivo studies which have shown the significant role of the LOXs in tissue repair, e.g., tendon regeneration, ligament healing, cutaneous wound healing, and cartilage remodeling, we focused on the role of the LOXs in inflammation phase, proliferation phase, and tissue remodeling phase of the repair process. By summarizing its healing role, we hope to shed light on the understanding of its potential in tissue repair and provide up to date therapeutic strategies towards related injuries.

A Review of Current Regenerative Medicine Strategies that Utilize Nanotechnology to Treat Cartilage Damage

Background:

Cartilage is an important tissue found in a variety of anatomical locations. Damage to cartilage is particularly detrimental, owing to its intrinsically poor healing capacity. Current reconstructive options for cartilage repair are limited, and alternative approaches are required. Biomaterial science and Tissue engineering are multidisciplinary areas of research that integrate biological and engineering principles for the purpose of restoring premorbid tissue function. Biomaterial science traditionally focuses on the replacement of diseased or damaged tissue with implants. Conversely, tissue engineering utilizes porous biomimetic scaffolds, containing cells and bioactive molecules, to regenerate functional tissue. However, both paradigms feature several disadvantages. Faced with the increasing clinical burden of cartilage defects, attention has shifted towards the incorporation of Nanotechnology into these areas of regenerative medicine.

Methods:

Searches were conducted on Pubmed using the terms “cartilage”, “reconstruction”, “nanotechnology”, “nanomaterials”, “tissue engineering” and “biomaterials”. Abstracts were examined to identify articles of relevance, and further papers were obtained from the citations within.

Results:

The content of 96 articles was ultimately reviewed. The literature yielded no studies that have progressed beyond in vitro and in vivo experimentation. Several limitations to the use of nanomaterials to reconstruct damaged cartilage were identified in both the tissue engineering and biomaterial fields.

Conclusion:

Nanomaterials have unique physicochemical properties that interact with biological systems in novel ways, potentially opening new avenues for the advancement of constructs used to repair cartilage. However, research into these technologies is in its infancy, and clinical translation remains elusive.

Nanoscale Surface Modifications of Medical Implants for Cartilage Tissue Repair and Regeneration

BACKGROUND

Natural cartilage regeneration is limited after trauma or degenerative processes. Due to the clinical challenge of reconstruction of articular cartilage, research into developing biomaterials to support cartilage regeneration have evolved. The structural architecture of composition of the cartilage extracellular matrix (ECM) is vital in guiding cell adhesion, migration and formation of cartilage. Current technologies have tried to mimic the cell's nanoscale microenvironment to improve implants to improve cartilage tissue repair.

METHODS

This review evaluates nanoscale techniques used to modify the implant surface for cartilage regeneration.

RESULTS

The surface of biomaterial is a vital parameter to guide cell adhesion and consequently allow for the formation of ECM and allow for tissue repair. By providing nanosized cues on the surface in the form of a nanotopography or nanosized molecules, allows for better control of cell behaviour and regeneration of cartilage. Chemical, physical and lithography techniques have all been explored for modifying the nanoscale surface of implants to promote chondrocyte adhesion and ECM formation.

CONCLUSION

Future studies are needed to further establish the optimal nanoscale modification of implants for cartilage tissue regeneration.

Nanotechnology for mesenchymal stem cell therapies

Mesenchymal stem cells (MSC) display great proliferative, differentiative, chemotactic, and immune-modulatory properties required to promote tissue repair. Several clinical trials based on the use of MSC are currently underway for therapeutic purposes. The aim of this article is to examine the current trends and potential impact of nanotechnology in MSC-driven regenerative medicine. Nanoparticle-based approaches are used as powerful carrier systems for the targeted delivery of bioactive molecules to ensure MSC long-term maintenance in vitro and to enhance their regenerative potential. Nanostructured materials have been developed to recapitulate the stem cell niche within a tissue and to instruct MSC toward the creation of regeneration-permissive environment. Finally, the capability of MSC to migrate toward the site of injury/inflammation has allowed for the development of diagnostic imaging systems able to monitor transplanted stem cell bio-distribution, toxicity, and therapeutic effectiveness.

3D tissue-engineered bone marrow as a novel model to study pathophysiology and drug resistance in multiple myeloma

PURPOSE

Multiple myeloma (MM) is the second most prevalent hematological malignancy and it remains incurable despite the introduction of several novel drugs. The discrepancy between preclinical and clinical outcomes can be attributed to the failure of classic two-dimensional (2D) culture models to accurately recapitulate the complex biology of MM and drug responses observed in patients.

EXPERIMENTAL DESIGN

We developed 3D tissue engineered bone marrow (3DTEBM) cultures derived from the BM supernatant of MM patients to incorporate different BM components including MM cells, stromal cells, and endothelial cells. Distribution and growth were analyzed by confocal imaging, and cell proliferation of cell lines and primary MM cells was tested by flow cytometry. Oxygen and drug gradients were evaluated by immunohistochemistry and flow cytometry, and drug resistance was studied by flow cytometry.

RESULTS

3DTEBM cultures allowed proliferation of MM cells, recapitulated their interaction with the microenvironment, recreated 3D aspects observed in the bone marrow niche (such as oxygen and drug gradients), and induced drug resistance in MM cells more than 2D or commercial 3D tissue culture systems.

CONCLUSIONS

3DTEBM cultures not only provide a better model for investigating the pathophysiology of MM, but also serve as a tool for drug development and screening in MM. In the future, we will use the 3DTEBM cultures for developing personalized therapeutic strategies for individual MM patients.

The tissue-engineered human cornea as a model to study expression of matrix metalloproteinases during corneal wound healing

Corneal injuries remain a major cause of consultation in the ophthalmology clinics worldwide. Repair of corneal wounds is a complex mechanism that involves cell death, migration, proliferation, differentiation, and extracellular matrix (ECM) remodeling. In the present study, we used a tissue-engineered, two-layers (epithelium and stroma) human cornea as a biomaterial to study both the cellular and molecular mechanisms of wound healing. Gene profiling on microarrays revealed important alterations in the pattern of genes expressed by tissue-engineered corneas in response to wound healing. Expression of many MMPs-encoding genes was shown by microarray and qPCR analyses to increase in the migrating epithelium of wounded corneas. Many of these enzymes were converted into their enzymatically active form as wound closure proceeded. In addition, expression of MMPs by human corneal epithelial cells (HCECs) was affected both by the stromal fibroblasts and the collagen-enriched ECM they produce. Most of all, results from mass spectrometry analyses provided evidence that a fully stratified epithelium is required for proper synthesis and organization of the ECM on which the epithelial cells adhere. In conclusion, and because of the many characteristics it shares with the native cornea, this human two layers corneal substitute may prove particularly useful to decipher the mechanistic details of corneal wound healing.

Tissue engineering strategy using mesenchymal stem cell-based chitosan scafolds in growth plate surgery: a preliminary study in rabbits

BACKGROUND

Growth plate injury in children could produce limb length discrepancy and angular deformity. Removal of damaged physis or bony bar and insertion of spacers produced variable results and for large defects in young children, the treatment is challenging. In this study, we used tissue-engineered mesenchymal stem cells (MSC-based chitosan scaffold) for restoration of the damaged physis. The usage of chitosan as a spacer was also investigated.

MATERIALS AND METHODS

An experimental model of growth arrest was created by removing lateral 50% of distal femoral physis of fourteen 4-week-olds albino rabbits. The left side growth plate defects were filled with MSC-based chitosan scaffold in 10 and scaffold alone in 4 rabbits. For all the rabbits, right-side defects were left alone as the control limb. After 3 months, femoral bones were harvested and gross inspection and radiology for measurement of angulations were done; histological study for evaluation of regeneration of physis was also done.

RESULTS

The hemiphyseal resection procedures were successful and all of the operated limbs showed angular deformities. There was a trend toward less angular deformity in cases in which more concentration of MSCs with chitosan scaffold was used. In cases of transfer of MSCs with concentration of less than 1.5 millions, mixed results were observed and angular deformities were not reduced. Transfer of chitosan alone yielded poor results.

CONCLUSION

In this study, we have developed an in vitro construction of a transplantable tissue-engineered disk, using natural chitosan scaffold and MSCs. We investigated the efficacy of these disks for repairing the defect of growth plate cartilage at distal femoral physis. Our results showed that the beneficial effect of these cells on scaffold appeared in more concentration of cells.

LEVEL OF EVIDENCE

Level III. Low power comparative study.

Regulatory challenges for autologous tissue engineered products on their way from bench to bedside in Europe

Since the late eighties of last century the high potential of tissue engineered products (TEP)s has been shown for the treatment of various diseases and many scientific publications appeared in this field. However, only few products reached the market since. Development of TEPs is a promising but owing to its novelty a very challenging task that requires experts in this still developing field as well as ample financial resources. This paper summarises relevant regulatory challenges during quality, preclinical and clinical development of autologous TEPs in Europe. Selected strategies on how to manage major issues are presented, together with some examples from the development of an autologous TEP for urethroplasty. Considering these aspects may help other investigators with potential strategies during the development of novel TEPs.

Development of a Bladder Bioreactor for Tissue Engineering in Urology

A urinary bladder bioreactor was constructed to replicate physiological bladder dynamics. A cyclical low-delivery pressure regulator mimicked filling pressures of the human bladder. Cell growth was evaluated by culturing human urothelial cells (UCs) on porcine extracellular matrix scaffolds (ECMs) in the bioreactor and in static growth conditions for 5 consecutive days. UC proliferation was compared with quantitative viability indicators and by fluorescent markers for intracellular esterase activity and plasma membrane integrity. Scaffold integrity was characterized with scanning electron microscopy and 4,6-diamidino-2-phenylindole staining.

3D tissue-engineered model of Ewing's sarcoma

Despite longstanding reliance upon monolayer culture for studying cancer cells, and numerous advantages from both a practical and experimental standpoint, a growing body of evidence suggests that more complex three-dimensional (3D) models are necessary to properly mimic many of the critical hallmarks associated with the oncogenesis, maintenance and spread of Ewing's sarcoma (ES), the second most common pediatric bone tumor. And as clinicians increasingly turn to biologically-targeted therapies that exert their effects not only on the tumor cells themselves, but also on the surrounding extracellular matrix, it is especially important that preclinical models evolve in parallel to reliably measure antineoplastic effects and possible mechanisms of de novo and acquired drug resistance. Herein, we highlight a number of innovative methods used to fabricate biomimetic ES tumors, encompassing both the surrounding cellular milieu and the extracellular matrix (ECM), and suggest potential applications to advance our understanding of ES biology, preclinical drug testing, and personalized medicine.

Dynamic nanomechanics of individual bone marrow stromal cells and cell-matrix composites during chondrogenic differentiation

Dynamic nanomechanical properties of bovine bone marrow stromal cells (BMSCs) and their newly synthesized cartilage-like matrices were studied at nanometer scale deformation amplitudes. The increase in their dynamic modulus, |E(*)| (e.g., 2.4±0.4 kPa at 1 Hz to 9.7±0.2 kPa at 316 Hz at day 21, mean±SEM), and phase angle, δ, (e.g., 15±2° at 1 Hz to 74±1° at 316 Hz at day 21) with increasing frequency were attributed to the fluid flow induced poroelasticity, governed by both the newly synthesized matrix and the intracellular structures. The absence of culture duration dependence suggested that chondrogenesis of BMSCs had not yet resulted in the formation of a well-organized matrix with a hierarchical structure similar to cartilage. BMSC-matrix composites demonstrated different poro-viscoelastic frequency-dependent mechanical behavior and energy dissipation compared to chondrocyte-matrix composites due to differences in matrix molecular constituents, structure and cell properties. This study provides important insights into the design of optimal protocols for tissue-engineered cartilage products using chondrocytes and BMSCs.

In Vivo Application of Tissue-Engineered Veins Using Autologous Peripheral Whole Blood: A Proof of Concept Study

Vascular diseases are increasing health problems affecting > 25 million individuals in westernized societies. Such patients could benefit from transplantation of tissue-engineered vascular grafts using autologous cells. One challenge that has limited this development is the need for cell isolation, and risks associated with ex vivo expanded stem cells. Here we demonstrate a novel approach to generate transplantable vascular grafts using decellularized allogeneic vascular scaffolds, repopulated with peripheral whole blood (PWB) in vitro in a bioreactor. Circulating, VEGFR-2 +/CD45 + and a smaller fraction of VEGFR-2 +/CD14 + cells contributed to repopulation of the graft. SEM micrographs showed flat cells on the luminal surface of the grafts consistent with endothelial cells. For clinical validation, two autologous PWB tissue-engineered vein conduits were prepared and successfully used for by-pass procedures in two pediatric patients. These results provide a proof of principle for the generation of transplantable vascular grafts using a simple autologous blood sample, making it clinically feasible globally.