Extracellular matrix scaffolds for cartilage and bone regeneration

A Bioactive Cartilage Graft of IGF1-Transduced Adipose Mesenchymal Stem Cells Embedded in an Alginate/Bovine Cartilage Matrix Tridimensional Scaffold

Articular cartilage injuries remain as a therapeutic challenge due to the limited regeneration potential of this tissue. Cartilage engineering grafts combining chondrogenic cells, scaffold materials, and microenvironmental factors are emerging as promissory alternatives. The design of an adequate scaffold resembling the physicochemical features of natural cartilage and able to support chondrogenesis in the implants is a crucial topic to solve. This study reports the development of an implant constructed with IGF1-transduced adipose-derived mesenchymal stem cells (immunophenotypes: CD105⁺, CD90⁺, CD73⁺, CD14⁻, and CD34⁻) embedded in a scaffold composed of a mix of alginate/milled bovine decellularized knee material which was cultivated in vitro for 28 days (3CI). Histological analyses demonstrated the distribution into isogenous groups of chondrocytes surrounded by a de novo dense extracellular matrix with balanced proportions of collagens II and I and high amounts of sulfated proteoglycans which also evidenced adequate cell proliferation and differentiation. This graft also shoved mechanical properties resembling the natural knee cartilage. A modified Bern/O'Driscoll scale showed that the 3CI implants had a significantly higher score than the 2CI implants lacking cells transduced with IGF1 (16/18 vs. 14/18), representing high-quality engineering cartilage suitable for in vivo tests. This study suggests that this graft resembles several features of typical hyaline cartilage and will be promissory for preclinical studies for cartilage regeneration.

3D Structure and Processing Methods Direct the Biological Attributes of ECM-Based Cardiac Scaffolds

High hopes are held for cardiac regenerative therapy, driving a vast research effort towards the development of various cardiac scaffolds using diverse technologies and materials. Nevertheless, the role of factors such as fabrication process and structure in determining scaffold's characteristics is yet to be discovered. In the present study, the effects of 3D structure and processing method on cardiac scaffolds are addressed using three distinct scaffolds made through different production technologies from the same biomaterial: decellularized porcine cardiac extracellular matrix (pcECM). pcECM patch, injectable pcECM hydrogel, and electrospun pcECM scaffolds were all proven as viable prospective therapies for MI, thus generally preserving pcECM beneficial properties. Yet, as we demonstrate, minor differences in scaffolds composition and micro-morphology as well as substantial differences in their mechanical properties, which arise from their production process, highly affect the interactions of the scaffold with both proliferating cells and functional cells. Hence, the rates of cell attachment, survival, and proliferation significantly vary between the different scaffolds. Moreover, major differences in cell morphology and alignment as well as in matrix remodeling are obtained. Overall, the effects revealed herein can guide a more rational scaffold design for the improved cellular or acellular treatment of different cardiac disease scenarios.

Fiber Reinforced Cartilage ECM Functionalized Bioinks for Functional Cartilage Tissue Engineering

Focal articular cartilage (AC) defects, if left untreated, can lead to debilitating diseases such as osteoarthritis. While several tissue engineering strategies have been developed to promote cartilage regeneration, it is still challenging to generate functional AC capable of sustaining high load-bearing environments. Here, a new class of cartilage extracellular matrix (cECM)-functionalized alginate bioink is developed for the bioprinting of cartilaginous tissues. The bioinks are 3D-printable, support mesenchymal stem cell (MSC) viability postprinting and robust chondrogenesis in vitro, with the highest levels of COLLII and ACAN expression observed in bioinks containing the highest concentration of cECM. Enhanced chondrogenesis in cECM-functionalized bioinks is also associated with progression along an endochondral-like pathway, as evident by increases in RUNX2 expression and calcium deposition in vitro. The bioinks loaded with MSCs and TGF-β3 are also found capable of supporting robust chondrogenesis, opening the possibility of using such bioinks for direct "print-and-implant" cartilage repair strategies. Finally, it is demonstrated that networks of 3D-printed polycaprolactone fibers with compressive modulus comparable to native AC can be used to mechanically reinforce these bioinks, with no loss in cell viability. It is envisioned that combinations of such biomaterials can be used in multiple-tool biofabrication strategies for the bioprinting of biomimetic cartilaginous implants.

Homing of adipose stem cells on the human amniotic membrane as a scaffold: A histological study

BACKGROUND

The human amniotic membrane (HAM) is a suitable and effective scaffold for cell culture and delivery, and adipose-derived stem cells (ADSCs) are an important source of stem cells for transplantation and chondrogenic differentiation.

OBJECTIVE

To assess the practicability of a cryopreserved HAM as a scaffold in cell proliferation and differentiation in vitro.

MATERIALS AND METHODS

In this experimental study, adipose tissue samples were harvested from the inguinal region of male patients aged 15-30 years. Flow cytometry was used to identify CD31, CD45, CD90, and CD105 markers in adipose stem cells. HAM was harvested from donor placenta after cesarean section, washed, trypsin-based decellularized trypsinized decellularized, and used as a scaffold via three methods: 1) ADSCs were differentiated into chondrocytes on cell culture flasks (monolayer method), and after 14 days of culture, the cells were transferred and cultured on both sides of the HAM; 2) ADSCs were cultured and differentiated directly on both sides of the HAM for 14 days (scaffold-mediated differentiation); and 3) chondrocytes were differentiated with micromass culture for 14 days, transferred on HAM, and tissue slides were histologically analyzed qualitatively.

RESULTS

Flow cytometry confirmed the presence of mesenchymal stem cells. Histological findings revealed that the cells adhered and grew well on the stromal layer of HAM. Among the three methods, scaffold-mediated differentiation of ADSCs showed the best results.

CONCLUSION

ADSCs have excellent attachment, viability, and differentiation capacity in the stromal side of HAM. Additionally, the direct culture and differentiation of ADSCs on HAM is more suitable than the culture of differentiated cells on HAM.

A Photo-Crosslinkable Kidney ECM-Derived Bioink Accelerates Renal Tissue Formation

3D bioprinting strategies in tissue engineering aim to fabricate clinically applicable tissue constructs that can replace the damaged or diseased tissues and organs. One of the main prerequisites in 3D bioprinting is finding an appropriate bioink that provides a tissue-specific microenvironment supporting the cellular growth and maturation. In this respect, decellularized extracellular matrix (dECM)-derived hydrogels have been considered as bioinks for the cell-based bioprinting due to their capability to inherit the intrinsic cues from native ECM. Herein, a photo-crosslinkable kidney ECM-derived bioink (KdECMMA) is developed that could provide a kidney-specific microenvironment for renal tissue bioprinting. Porcine whole kidneys are decellularized through a perfusion method, dissolved in an acid solution, and chemically modified by methacrylation. A KdECMMA-based bioink is formulated and evaluated for rheological properties and printability for the printing process. The results show that the bioprinted human kidney cells in the KdECMMA bioink are highly viable and mature with time. Moreover, the bioprinted renal constructs exhibit the structural and functional characteristics of the native renal tissue. The potential of the tissue-specific ECM-derived bioink is demonstrated for cell-based bioprinting that could enhance the cellular maturation and eventually tissue formation.

Decellularised nucleus pulposus as a potential biologic scaffold for disc tissue engineering

Intervertebral disc (IVD) degeneration is associated with lower back pain, with the dysfunction of nucleus pulposus (NP) cells instigating degeneration onset. Here, we developed an optimized decellularised NP scaffold that could induce mesenchymal stem cells (MSCs) into NP-like cells in vitro and rescue the degenerated IVD in vivo. We optimized a decellularisation protocol for porcine NP and evaluated the biological properties and microstructure of the NP scaffold. Through co-culture with MSCs, we analysed scaffold bioactivity and potential signalling pathways. We tested the therapeutic efficacy of the scaffold using an IVD degeneration model in vivo. The decellularisation protocol generally removed the cellular components of the NP and preserved the majority of the biological components and regular microstructure. MSCs seeded in the NP-ECM scaffold differentiated into NP-like cells in vitro; this change was attributed to activation of the TGF-β signalling pathway. The NP-ECM exhibited good cytocompatibility ex vivo and decelerated the degeneration of the IVD in vivo. These results indicate the successful establishment of a naturally-derived ECM material that could induce MSCs into NP cells and serve as a potential treatment for degenerated IVDs.

Mesenchymal stem cell-loaded porous tantalum integrated with biomimetic 3D collagen-based scaffold to repair large osteochondral defects in goats

Background

The body is unable to repair and regenerate large area bone defects. Moreover, the repair capacity of articular cartilage is very limited. There has long been a lack of effective treatments for osteochondral lesions. The engineered tissue with biphase synthetic for osteochondral repair has become one of the hot research fields over the past few years. In this study, an integrated biomanufacturing platform was constructed with bone marrow mesenchymal stem cells (BMSCs)/porous tantalum (pTa) associated with chondrocytes/collagen membranes (CM) to repair large osteochondral defects in load-bearing areas of goats.

Methods

Twenty-four goats with a large osteochondral defect in the femoral heads of the left hind legs were randomly divided into three groups: eight were treated with chondrocytes/CM-BMSCs/pTa, eight were treated with pure CM-pTa composite, and the other eight goats were untreated. The repair effect was assessed by X-ray, gross observation, and histomorphology for 16 weeks after the operation. In addition, the biocompatibility of chondrocytes/CM-BMSCs/pTa was observed by flow cytometry, CCK8, immunocytochemistry, and Q-PCR. The characteristics of the chondrocytes/CM-BMSCs/pTa were evaluated using both scanning electron microscopy and mechanical testing machine.

Results

The integrated repair material consists of pTa, injectable fibrin sealant, and CM promoted adhesion and growth of BMSCs and chondrocytes. pTa played an important role in promoting the differentiation of BMSCs into osteoblasts. Three-dimensional CM maintained the phenotype of chondrocytes successfully and expressed chondrogenic genes highly. The in vivo study showed that after 16 weeks from implantation, osteochondral defects in almost half of the femoral heads had been successfully repaired by BMSC-loaded pTa associated with biomimetic 3D collagen-based scaffold.

Conclusions

The chondrocytes/CM-BMSCs/pTa demonstrated significant therapeutic efficacy in goat models of large osteochondral defect. This provides a novel therapeutic strategy for large osteochondral lesions in load-bearing areas caused by severe injury, necrosis, infection, degeneration, and tumor resection with a high profile of safety, effectiveness, and simplicity.

Human mesenchymal stromal cells in adhesion to cell-derived extracellular matrix and titanium: Comparative kinome profile analysis

The extracellular matrix (ECM) physically supports cells and influences stem cell behaviour, modulating kinase-mediated signalling cascades. Cell-derived ECMs have emerged in bone regeneration as they reproduce physiological tissue-architecture and ameliorate mesenchymal stromal cell (MSC) properties. Titanium scaffolds show good mechanical properties, facilitate cell adhesion, and have been routinely used for bone tissue engineering (BTE). We analyzed the kinomic signature of human MSCs in adhesion to an osteopromotive osteoblast-derived ECM, and compared it to MSCs on titanium. PamChip kinase-array analysis revealed 63 phosphorylated peptides on ECM and 59 on titanium, with MSCs on ECM exhibiting significantly higher kinase activity than on titanium. MSCs on the two substrates showed overlapping kinome profiles, with activation of similar signalling pathways (FAK, ERK, and PI3K signalling). Inhibition of PI3K signalling in cells significantly reduced adhesion to ECM and increased the number of nonadherent cells on both substrates. In summary, this study comprehensively characterized the kinase activity in MSCs on cell-derived ECM and titanium, highlighting the role of PI3K signalling in kinomic changes regulating osteoblast viability and adhesion. Kinome profile analysis represents a powerful tool to select pathways to better understand cell behaviour. Osteoblast-derived ECM could be further investigated as titanium scaffold-coating to improve BTE.

Tunable synthetic extracellular matrices to investigate breast cancer response to biophysical and biochemical cues

The extracellular matrix (ECM) is thought to play a critical role in the progression of breast cancer. In this work, we have designed a photopolymerizable, biomimetic synthetic matrix for the controlled, 3D culture of breast cancer cells and, in combination with imaging and bioinformatics tools, utilized this system to investigate the breast cancer cell response to different matrix cues. Specifically, hydrogel-based matrices of different densities and modified with receptor-binding peptides derived from ECM proteins [fibronectin/vitronectin (RGDS), collagen (GFOGER), and laminin (IKVAV)] were synthesized to mimic key aspects of the ECM of different soft tissue sites. To assess the breast cancer cell response, the morphology and growth of breast cancer cells (MDA-MB-231 and T47D) were monitored in three dimensions over time, and differences in their transcriptome were assayed using next generation sequencing. We observed increased growth in response to GFOGER and RGDS, whether individually or in combination with IKVAV, where binding of integrin β1 was key. Importantly, in matrices with GFOGER, increased growth was observed with increasing matrix density for MDA-MB-231s. Further, transcriptomic analyses revealed increased gene expression and enrichment of biological processes associated with cell-matrix interactions, proliferation, and motility in matrices rich in GFOGER relative to IKVAV. In sum, a new approach for investigating breast cancer cell-matrix interactions was established with insights into how microenvironments rich in collagen promote breast cancer growth, a hallmark of disease progression in vivo, with opportunities for future investigations that harness the multidimensional property control afforded by this photopolymerizable system.

A hydrogel derived from acellular blood vessel extracellular matrix to promote angiogenesis

The biocompatibility and bioactivity of injectable acellular extracellular matrix nominates its use as an optimal candidate for cell delivery, serving as a reconstructive scaffold. In this study, we investigated the feasibility of preparing a blood vessel matrix (BVM) hydrogel, which revealed its pro-angiogenic effects in vitro and its therapeutic effects in an in vivo skin flap model. Aortic and abdominal aortic arteries from pigs were acellularized by Triton-X 100 and confirmed by hematoxylin and eosin and 4,6-diamidino-2-phenylindole staining. Different concentrations of blood vessel matrix hydrogel were generated successfully through enzymatic digestion, neutralization, and gelation. Hematoxylin and eosin staining, Masson’s trichrome staining, collagen type I immunohistochemistry staining, and enzyme-linked immunosorbent assays showed that type I collagen and some growth factors were retained in the hydrogel. Scanning electron microscopy demonstrated the different diametric fibrils in blood vessel matrix hydrogels. A blood vessel matrix hydrogel-coated plate promoted the tube formation of human umbilical vein endothelial cells in vitro. After injection into skin flaps, the hydrogel improved the flap survival rate and increased blood perfusion and capillary density. These results indicated that we successfully prepared a blood vessel matrix hydrogel and demonstrated its general characteristics and angiogenic effects in vitro and in vivo.

Intact vitreous humor as a potential extracellular matrix hydrogel for cartilage tissue engineering applications

Decellularisation of tissues, utilising their biochemical cues, poses exciting tissue engineering (TE) opportunities. However, removing DNA from cartilage (dCart) requires harsh treatments due to its dense structure, causing loss of bioactivity and limiting its application as a cartilaginous extra cellular matrix (ECM). In this study, we demonstrate for the first time the successful application of vitreous humor (VH), a highly hydrated tissue closely resembling the glycosaminoglycan (GAG) and collagen composition of cartilage, as an ECM hydrogel to support chondrogenic differentiation. Equine VH was extracted followed by biochemical quantifications, histological examinations, cytotoxicity (human mesenchymal stromal cells, hMSCs and human articular chondrocytes, hACs) and U937 cell proliferation studies. VH was further seeded with hACs or hMSCs and cultured for 3-weeks to study chondrogenesis compared to scaffold-free micro-tissue pellet cultures and collagen-I hydrogels. Viability, metabolic activity, GAG and DNA content, chondrogenic gene expression (aggrecan, collagen I/II mRNA) and mechanical properties were quantified and matrix deposition was visualised using immunohistochemistry (Safranin-O, collagen I/II). VH was successfully extracted, exhibiting negligible amounts of DNA (0.4 ± 0.4 µg/mg dry-weight) and notable preservation of ECM components. VH displayed neither cytotoxic responses nor proliferation of macrophage-like U937 cells, instead enhancing both hMSC and hAC proliferation. Interestingly, encapsulated cells self-assembled the VH-hydrogel into spheroids, resulting in uniform distribution of both GAGs and collagen type II with increased compressive mechanical properties, rendering VH a permissive native ECM source to fabricate cartilaginous hydrogels for potential TE applications. STATEMENT OF SIGNIFICANCE: Fabricating bioactive and cell-instructive cartilage extracellular matrix (ECM) derived biomaterials and hydrogels has over recent years proven to be a challenging task, often limited by poor retention of inherent environmental cues post decellularisation due to the dense and avascular nature of native cartilage. In this study, we present an alternative route to fabricate highly permissive and bioactive ECM hydrogels from vitreous humor (VH) tissue. This paper specifically reports the discovery of optimal VH extraction protocols and cell seeding strategy enabling fabrication of cartilaginous matrix components into a hydrogel support material for promoting chondrogenic differentiation. The work showcases a naturally intact and unmodified hydrogel design that improves cellular responses and may help guide the development of cell instructive and stimuli responsive hybrid biomaterials in a number of TERM applications.

Inhibition of the Oxygen Sensor PHD2 Enhances Tissue-Engineered Endochondral Bone Formation

Tissue engineering holds great promise for bone regenerative medicine, but clinical translation remains challenging. An important factor is the low cell survival after implantation, primarily caused by the lack of functional vasculature at the bone defect. Interestingly, bone development and repair initiate predominantly via an avascular cartilage template, indicating that chondrocytes are adapted to limited vascularization. Given these advantageous properties of chondrocytes, we questioned whether tissue-engineered cartilage intermediates implanted ectopically in mice are able to form bone, even when the volume size increases. Here, we show that endochondral ossification proceeds efficiently when implant size is limited (≤30 mm³ ), but chondrogenesis and matrix synthesis are impaired in the center of larger implants, leading to a fibrotic core. Increasing the level of angiogenic growth factors does not improve this outcome, because this strategy enhances peripheral bone formation, but disrupts the conversion of cartilage into bone in the center, resulting in a fibrotic core, even in small implants. On the other hand, activation of hypoxia signaling in cells before implantation stimulates chondrogenesis and matrix production, which culminates in enhanced bone formation throughout the entire implant. Together, our results show that induction of angiogenesis alone may lead to adverse effects during endochondral bone repair, whereas activation of hypoxia signaling represents a superior therapeutic strategy to improve endochondral bone regeneration in large tissue-engineered implants. © 2018 American Society for Bone and Mineral Research.

A silk fibroin/decellularized extract of Wharton's jelly hydrogel intended for cartilage tissue engineering

A hybrid hydrogel was obtained from decellularized extract from Wharton's jelly (DEWJ) and silk fibroin (SF) and characterized for cartilage tissue engineering. Wharton's jelly was used due to its similarity with articular cartilage in extracellular matrix composition. Also, silk fibroin has good mechanical properties which make this construct appropriate for cartilage repair. Decellularization of Wharton's jelly was verified by DAPI staining, DNA quantification, and PCR analysis. Then, the biochemical composition of DEWJ was determined by ELISA kits for total proteins, collagens, sulfated glycosaminoglycans (sGAG), and transforming growth factor β1 (TGF-β1). After fabricating pure SF and SF/DEWJ hybrid hydrogels, their physical and mechanical properties were characterized by FESEM, Fourier-transform infrared spectroscopy (FTIR) and rheological assays (amplitude and frequency sweeps). Furthermore, cell viability and proliferation were assessed by MTT assay. The results have shown that DEWJ in hybrid hydrogels enhances mechanical properties of the construct relative to pure SF hydrogels. Also, this extract at its 40% concentration in culture media and 20% or 40% concentrations in SF/DEWJ hybrid hydrogels significantly increases population of the cells compared to control and pure SF hydrogel after 7 days. In conclusion, this study proposes the potential of SF/DEWJ hybrid hydrogels for cartilage tissue engineering applications.

Repair of cartilage defects with devitalized osteochondral tissue: A pilot animal study

Devitalization using high hydrostatic pressure (HHP) treatment inactivates cells while matrix structure and biomechanical properties are maintained. Because of strong chondroinductive potential of HHP-devitalized cartilage matrix, it may be used as scaffold for reconstruction of (osteo-)chondral lesions. In this pilot study, we evaluated the feasibility of HHP-devitalized osteochondral tissue to repair osteochondral defects in a rabbit model. Removal and reimplantation of osteochondral plugs were performed in 12 female New Zealand White rabbits. From the knee joint of each animal, osteochondral plugs (diameter = 4 mm; depth = 2.5 mm) were harvested and devitalized by HHP (452 MPa for 10 min). Afterward, the plugs were reimplanted into the respective cavity, from where they were taken. Animals were sacrificed 12 weeks postoperatively and the integration of osteochondral plugs was examined using μ-CT, MRI, and histological staining. Furthermore, revitalization of HHP-treated osteochondral plugs was characterized by gene expression analyses. Macroscopic evaluation of tissue repair at implantation sites of HHP-treated osteochondral plugs showed an adequate defect filling 12 weeks after implantation. Plug margins were hardly detectable indicating successful tissue integration. Additionally, gene expression analyses demonstrated initial revitalization of the HHP-treated tissue 12 weeks postoperatively. Our preliminary data revealed that HHP-treated osteochondral plugs could be used to refill osteochondral defects in the knee joint and promote cell migration into defect site. Data indicated that HHP-treated tissue has the potential to act as functional scaffolds for reconstruction of cartilage defects. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2354-2364, 2019.

Cartilage regeneration using decellularized cartilage matrix: Long-term comparison of subcutaneous and intranasal placement in a rabbit model

Autologous cartilage as donor tissue for various surgical reconstructions such as nasal septum regeneration is limited and associated with donor site morbidity. Our goal was to evaluate a new resorbable chondroconductive biomaterial made of decellularized porcine nasal septum cartilage compared with autologous native auricular cartilage as the gold standard. In order to examine the material and determine its long-term outcome further, we used subcutaneous implantation and septal implantation in an orthotopic rabbit model. In addition to non-seeded decellularized xenogenic cartilage, chondrocyte-seeded decellularized xenogenic cartilage was implanted as a septal replacement. After a three- or six-month period, the formation of newly synthesized cartilage extracellular matrix was evaluated immunohistochemically, whereas septal integrity and biocompatibility were evaluated histologically. The formation of the implanted neoseptum and form stability was analyzed by using 7-Tesla Magnetic Resonance Imaging. Good biocompatibility with no excessive rejection was demonstrated in all groups. Long-term stable and reliable septal reconstruction could be achieved in the study groups with or without cell seeding with autologous auricular chondrocytes. Autologous cell seeding was advantageous only with regard to septal perforations. Thus, cell seeding provides a benefit regarding long-term stability. However, because of slightly better biocompatibility, less pronounced septum deviation and the markedly lower effort involved, the non-seeded scaffold is favoured for possible clinical application.

Disassembling and Reaggregating the Thymus: The Pros and Cons of Current Assays

This review briefly describes the last decades of experimental work on the thymus. Given the histological complexity of this organ, the multiple embryological origins of its cellular components and its role in carefully regulating T lymphocyte maturation and function, methods to dissect and understand this complexity have been developed through the years. The possibility to study ex vivo the thymus organ function has been achieved by developing Fetal Thymus Organ Cultures (FTOC). Subsequently, the combination of organ disaggregation and reaggregation in vitro represented by Reaggregate Thymus Organ cultures (RTOC) allowed mixing cellular components from different genetic backgrounds. Moreover, RTOC allowed dissecting the different stromal and hematological components to study the interactions between Major Histocompatibility Complex (MHC) molecules and the T-cell receptors during thymocytes selection. In more recent years, prospective isolation of stromal cells and thymocytes at different stages of development made it possible to explore and elucidate the molecular and cellular players in both the developing and adult thymus. Finally, the appearance of novel cell sources such as embryonic stem (ES) cells and more recently induced pluripotent stem (iPS) cells has opened new scenarios in modelling thymus development and regeneration strategies. Most of the work described was carried out in rodents and the current challenge is to develop equivalent or even more informative assays and tools in entirely human model systems.

Bioartificial Organ Manufacturing Technologies

Bioartificial organ manufacturing technologies are a series of enabling techniques that can be used to produce human organs based on bionic principles. During the last ten years, significant progress has been achieved in the development of various organ manufacturing technologies. According to the degree of automation, organ manufacturing technologies can be divided into three main groups: (1) fully automated; (2) semi-automated; (3) handworked (or handmade); each has the advantages and disadvantages for bioartificial organ manufacturing. One of the most promising bioartificial organ manufacturing technologies is to use combined multi-nozzle three-dimensional printing techniques to automatically assemble personal cells along with other biomaterials to build exclusive organ substitutes for defective/failed human organs. This is the first time that advanced bioartificial organ manufacturing technologies have been reviewed. These technologies hold the promise to greatly improve the quality of health and average lifespan of human beings in the near future.

Bionic cartilage acellular matrix microspheres as a scaffold for engineering cartilage

Bionic cartilage acellular matrix microspheres (BCAMMs) made from decelluarized bionic cartilage microspheres (BCMs).

The Importance of Controlled Mismatch of Biomechanical Compliances of Implantable Scaffolds and Native Tissue for Articular Cartilage Regeneration

Scaffolds for articular cartilage repair have to be optimally biodegradable with simultaneous promotion of hyaline cartilage formation under rather complex biomechanical and physiological conditions. It has been generally accepted that scaffold structure and composition would be the best when it mimics the structure of native cartilage. However, a reparative construct mimicking the mature native tissue in a healing tissue site presents a biological mismatch of reparative stimuli. In this work, we studied a new recombinant human type III collagen-polylactide (rhCol-PLA) scaffolds. The rhCol-PLA scaffolds were assessed for their relative performance in simulated synovial fluids of 1 and 4 mg/mL sodium hyaluronate with application of model-free analysis with Biomaterials Enhanced Simulation Test (BEST). Pure PLA scaffold was used as a control. The BEST results were compared to the results of a prior in vivo study with rhCol-PLA. Collectively the data indicated that a successful articular cartilage repair require lower stiffness of the scaffold compared to surrounding cartilage yet matching the strain compliance both in static and dynamic conditions. This ensures an optimal combination of load transfer and effective oscillatory nutrients supply to the cells. The results encourage further development of intelligent scaffold structures for optimal articular cartilage repair rather than simply trying to imitate the respective original tissue.

Novel decellularized animal conchal cartilage graft for application in human patient

Restoration of the external ear and nose in human patients, in either congenital deformity or acquired defects, is a challenge in reconstructive surgery. Optimization of the currently available materials is necessary for rhinoplasty and microtia correction to avoid intraoperative manoeuvring and early rejection. The aim of this study was to develop cross-linked decellularized caprine conchal cartilages as biocompatible, robust, and non-toxic matrix template. The characterization of the decellularized tissue encompasses in vitro lymphoproliferation assay, cytotoxicity test, agar gel precipitation test, in vivo immunocompatibility study, histology, and determination of pro-inflammatory cytokines in animal model. Decellularized cartilage was implanted in human volunteer at R. G. Kar Medical College and Hospital, Kolkata, India, and samples were assessed histologically by retrieving those after 4 months. The processed cartilages were implanted in rhinoplasty (nine) and microtia patients (six) keeping autogenous cartilage graft as control up to 18 months after surgery. Primary outcomes were viability and safety of the material, both in animal model and human pre-application in actual site. Secondary outcomes included self-assessed clinical findings on gross examination. This study is under the ethical approval no. RKC/14 dated January 27, 2012. The in vitro cellular reactivity was less in processed cartilage protein than control. Histology of retrieved tissues in animal model and human volunteer showed no adverse reactions. Production of IL-2, IL-6, and TNF-α cytokines was lower at 4 weeks. The rhinoplasty and microtia operation in clinical patients utilizing the processed cartilage showed satisfactory recovery with improved facial look. These low cost, easily available, biocompatible, safe xenocartilage biomatrices of caprine conchal cartilage origin are very flexible in shape and size, enabling them as potential bioimplant for repair of nasal and auricular structure without any rejection or diverse biomedical applications.

Mesenchymal stem cells associated with chitosan scaffolds loaded with rosuvastatin to improve wound healing

In this study we explored the role of rosuvastatin calcium in skin regeneration as statins play important role in the field of tissue engineering. Chitosan hydrochloride was crosslinked with different weight ratios of collagen, β-glycerolphosphate and carboxymethyl cellulose to produce scaffolds by lyophilization technique. Subsequently, the fabricated scaffolds were examined for their morphology, water absorption capacity, water retention, friability and in-vitro drug release as well as in-vivo studies. The results revealed porous 3-D structured scaffolds with maximum water absorption values-ranging between 396 and 2993%. Scaffolds containing carboxymethyl cellulose revealed highest water absorption-values. In-vitro drug release results showed gradual drug release for 60 h with mean dissolution time-values (MDT) between 13 and 21 h. Combination of chitosan, collagen, carboxymethyl cellulose in weight ratio of 40:30:30, respectively achieved gradual disintegration of the scaffold in a simulating medium to an open wound after 4 days. This selected scaffold loaded with rosuvastatin revealed increase proliferation of human dermal fibroblasts compared to placebo scaffold. After 30 days of implantation of selected medicated scaffold loaded with/without mesenchymal stem cells and placebo scaffolds to induced wounds in Albino rats, enhanced skin regeneration and absence of scar formation for drug loaded scaffolds were observed. The histopathological study showed the advantage of stem cells-loaded scaffolds through the normal redistribution of collagen in the epidermal layer. In conclusion, rosuvastatin calcium and stem cells loaded in the tested scaffolds proved their potential effect in enhancing skin healing and regeneration.

Cartilaginous extracellular matrix derived from decellularized chondrocyte sheets for the reconstruction of osteochondral defects in rabbits

Cartilaginous extracellular matrix (ECM) materials derived from decellularized native articular cartilage are widely used in cartilage regeneration. However, it is difficult for endogenous cells to migrate into ECM derived from native cartilage owing to its nonporous structure and dense nature. Moreover, current decellularization approaches frequently lead to architectural breakdown and potential loss of surface composition of ECM. To solve this problem, we aimed to establish a novel biological ECM scaffold from chondrocyte sheets for cartilage regeneration. We cultured chondrocytes harvested from the auricular cartilage of 4-week-old New Zealand rabbits and enabled them to form cell sheets. These sheets were decellularized using sodium dodecyl sulfate (SDS) with three different concentrations, namely, 1%, 5%, and 10%, followed by 1% Triton X-100 and deoxyribonuclease enzyme solution. In vitro microstructural examination and mechanical tests demonstrated that 1% SDS not only removed chondrocytes completely but also maintained the native architecture and composition of ECM, thus avoiding the use of high-concentration SDS. Application of decellularized chondrocyte sheets for osteochondral defects in rabbits resulted in substantial host remodeling and variant regeneration of osteochondral tissues. One percent SDS-treated decellularized chondrocyte sheets contributed to the superior reconstruction of osteochondral defects as compared with 5% and 10% SDS groups, which includes vascularized subchondral bone, articular cartilage with adequate thickness, and integration with host tissues. Furthermore, ECM from 1% SDS significantly increased the migrating potential of bone marrow mesenchymal stem cells (BMSCs) in vitro. RT-PCR and western blot also revealed that ECM increased the expression of SOX-9 in BMSCs, whereas it decreased COL-X expression. In conclusion, our results suggested that the chondrocyte sheets decellularized with 1% SDS preserved the integrity and bioactivity, which favored cell recruitment and enabled osteochondral regeneration in the knee joints of rabbits, thus offering a promising approach for articular cartilage reconstruction without cell transplantation. STATEMENT OF SIGNIFICANCE: Although biological extracellular matrix (ECM) derived from decellularized native cartilage has been widely used in cartilage regeneration, it is difficult for endogenous cells to migrate into ECM owing to its dense nature. Moreover, current decellularization approaches lead to architectural breakdown of ECM. This study established a novel biological ECM from decellularized chondrocyte sheets for cartilage regeneration. Our results suggested that cartilaginous ECM favored cell recruitment and enabled osteochondral regeneration in rabbits, thus offering a promising approach for articular cartilage reconstruction without cell transplantation. SDS 1% adequately decellularized the chondrocytes in cell sheets, whereas it maintained the native architecture and composition of ECM, thereby avoiding the use of high-concentration SDS and providing a new way to acquire cartilaginous ECM.

Decellularization of Trachea With Combined Techniques for Tissue-Engineered Trachea Transplantation

Objectives

The purpose of this study is to shorten the decellularization time of trachea by using combination of physical, chemical, and enzymatic techniques.

Methods

Approximately 3.5-cm-long tracheal segments from 42 New Zealand rabbits (3.5±0.5 kg) were separated into seven groups according to decellularization protocols. After decellularization, cellular regions, matrix and strength and endurance of the scaffold were followed up.

Results

DNA content in all groups was measured under 50 ng/mg and there was no significant difference for the glycosaminoglycan content between group 3 (lyophilization+deoxycholic acid+de-oxyribonuclease method) and control group (P=0.46). None of the decellularized groups was different than the normal trachea in tensile stress values (P>0.05). Glucose consumption and lactic acid levels measured from supernatants of all decellularized groups were close to group with cells only (76 mg/dL and 53 mg/L).

Conclusion

Using combination methods may reduce exposure to chemicals, prevent the excessive influence of the matrix, and shorten the decellularization time.

Human amniotic membrane as differentiating matrix for in vitro chondrogenesis

Aim: The aim of the present study is to use human amniotic membrane (HAM) for in vitro chondrogenesis of placenta-derived mesenchymal stem cells (MSCs) and umbilical cord-derived MSCs. Materials & methods: MSCs from the placenta and umbilical cord were isolated, characterized by immunophenotyping and after analyzing their rate of proliferation, cytotoxicity and viability, chondrogenesis was performed on plastic adherent surface and on HAM. Results: Successfully isolated and characterized placenta-derived MSCs and umbilical cord-derived MSCs revealed positive expression of MSCs markers CD90, CD73, CD105 and CD49d, while they were negative for CD45. Both types of cells in the presence of chondrogenic induction medium on plastic adherent surface and HAM showed aggregates of proteoglycan and strong expression of COL2A1 (collagen 2) and ACAN1 (aggrecan). Conclusion: HAM supported proliferation as well as chondrogenesis of MSCs and provide novelty of HAM utilization as an efficient natural delivery matrix for stem cell transplantation.

Clinical Protocol of Producing Adipose Tissue-Derived Stromal Vascular Fraction for Potential Cartilage Regeneration

Osteoarthritis (OA) is one of the most common debilitating disorders. Recently, numerous attempts have been made to improve the functions of the knees by using different forms of mesenchymal stem cells (MSCs). In Korea, bone marrow concentrates and cord blood-derived stem cells have been approved by the Korean Food and Drug Administration (KFDA) for cartilage regeneration. In addition, an adipose tissue-derived stromal vascular fraction (SVF) has been allowed by the KFDA for joint injections in human patients. Autologous adipose tissue-derived SVF contains extracellular matrix (ECM) in addition to mesenchymal stem cells. ECM excretes various cytokines that, along with hyaluronic acid (HA) and platelet-rich plasma (PRP) activated by calcium chloride, may help MSCs to regenerate cartilage and improve knee functions. In this article, we presented a protocol to improve knee functions by regenerating cartilage-like tissue in human patients with OA. The result of the protocol was first reported in 2011 followed by a few additional publications. The protocol involves liposuction to obtain autologous lipoaspirates that are mixed with collagenase. This lipoaspirates-collagenase mixture is then cut and homogenized to remove large fibrous tissue that may clog up the needle during the injection. Afterwards, the mixture is incubated to obtain adipose tissue-derived SVF. The resulting adipose tissue-derived SVF, containing both adipose tissue-derived MSCs and remnants of ECM, is injected into knees of patients, combined with HA and calcium chloride activated PRP. Included are three cases of patients who were treated with our protocol resulting in improvement of knee pain, swelling, and range of motion along with MRI evidence of hyaline cartilage-like tissue.

Potential Use of Amniotic Membrane - Derived Scaffold for Cerebrospinal Fluid Applications

Scaffolds derived from decellularized tissues provide a natural microenvironment for cell culture. Embryonic cerebrospinal fluid (e-CSF) contains factors which play vital roles in the development of the nervous system. This research was aimed to survey the effect of Wistar rat e-CSF on neural differentiation of bone marrow derived mesenchymal stem cells (BM-MSCs) cultured on the human amniotic membrane (AM). BM-MSCs were collected from femurs and tibias, and were cultured in Dulbecco's Modified Eagle's Medium. The placenta was harvested from healthy women during cesarean section and AM was acellularized using EDTA and physical scrubbing. e- CSF was harvested from rat fetuses at E17. Adequate numbers of BM-MSCs were cultured on acellularized membrane, and were treated with E17 CSF for 7 days. MTT (3-(4, 5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) assay confirmed the survival and proliferation of BM-MSCs cultured on AM derived scaffold. Hematoxylin/eosin staining and scanning electron microscopy showed the morphological and the structural changes of BM-MSCs throughout the culture and treatment with e-CSF. The results of immunocytochemistry showed that microtubule associated protein 2 and beta-III tubulin were expressed in BM-MSCs cultured on acellular amnion scaffold and treated with e-CSF. Our results showed for the first time that the combination of acellular AM as a natural scaffold and e-CSF as a source of neurological factors could effectively improve the BM-MSCs cultivation and differentiation.

Effect of ascorbic and chondrogenic derived decellularized extracellular matrix from mesenchymal stem cells on their proliferation, viability and differentiation

BACKGROUND

The development and application of biomaterials to promote stem cell proliferation and differentiation has undergone major expansion over the last few years. Decellularized stem cell matrix (DSCMs) represent bioactive and biocompatible materials which achieve similar characteristics of native extracellular matrix. DSCMs have given promising outcomes in generating novel cell culture substrates mimicking specific niche microenvironments in tissue engineering.

AIMS

This research aims at producing two different DSCMs obtained from adipose derived mesenchymal stem cells and bone marrow mesenchymal stem cells, characterize them and evaluate the DSCMs bioactivity on mesenchymal stem cells.

METHODS

DSCMs were produced using ascorbic or chondrogenic medium, which were then used as a scaffold for adipose derived mesenchymal stem cells and bone marrow mesenchymal stem cells, respectively. The biological characteristics of both types of DSCMs, including cell attachment, morphology, proliferation, viability, and chondrogenic and osteogenic differentiation were evaluated and compared.

RESULTS

Differences between ascorbic derived-DSCMs and chondrogenic derived DSCMs were found. Chondrogenic derived-DSCMs remained compact and stronger during extraction and this made their handling easier. Ascorbic derived-DSCMs showed a different protein composition to chondrogenic-DSCMs. Bioactive characteristics analyzed were different depending on the cellular origin of DSCM and the method used to produce them.

CONCLUSIONS

The DSCMs obtained in this work constitutes favorable structure- and growth factors providing a microenvironment which is very similar to that of native ECM, which results in enhanced biological potential of the MSCs and responsiveness to the induction of differentiation. We found differences between ascorbic derived-DSCMs and chondrogenic derived DSCMs. Our results suggest that the cell source used to produce DSCMs is highly related to the bioactive characteristics of DSCMs.

Cartilage Regeneration in Humans with Adipose Tissue-Derived Stem Cells and Adipose Stromal Vascular Fraction Cells: Updated Status

Adipose tissue-derived stem cells (ASCs) in the form of stromal vascular fraction (SVF) and cultured expansion have been applied in clinical settings in some countries to treat osteoarthritis (OA) of knees, one of the most common debilitating, incurable disorders. Since the first report of successful cartilage-like tissue regeneration with autologous adipose SVF containing ASCs, there has been a gradual increase in the number of publications confirming such results. Thus far, most of the reports have been limited to treatments of OA of knees. Recently, successful applications of adipose SVF in treating OA of ankles and hips have been reported. In addition, several groups have reported modified methods of applying adipose SVF, such as combining bone marrow stimulation with adipose SVF or adding additional extracellular matrix (ECM) in treating OA. Here, we present an updated, systematic review of clinical effectiveness and safety in treating OA of knees, ankles, and one hip since 2016 using ASCs in the form of adipose SVF or in cultured expansion, along with a description and suggestion of potential biological mechanisms of cartilage regeneration.

Trinity of Three-Dimensional (3D) Scaffold, Vibration, and 3D Printing on Cell Culture Application: A Systematic Review and Indicating Future Direction

Cell culture and cell scaffold engineering have previously developed in two directions. First can be 'static into dynamic', with proven effects that dynamic cultures have benefits over static ones. Researches in this direction have used several mechanical means, like external vibrators or shakers, to approximate the dynamic environments in real tissue, though such approaches could only partly address the issue. Second, can be '2D into 3D', that is, artificially created three-dimensional (3D) passive (also called 'static') scaffolds have been utilized for 3D cell culture, helping external culturing conditions mimic real tissue 3D environments in a better way as compared with traditional two-dimensional (2D) culturing. In terms of the fabrication of 3D scaffolds, 3D printing (3DP) has witnessed its high popularity in recent years with ascending applicability, and this tendency might continue to grow along with the rapid development in scaffold engineering. In this review, we first introduce cell culturing, then focus 3D cell culture scaffold, vibration stimulation for dynamic culture, and 3DP technologies fabricating 3D scaffold. Potential interconnection of these realms will be analyzed, as well as the limitations of current 3D scaffold and vibration mechanisms. In the recommendation part, further discussion on future scaffold engineering regarding 3D vibratory scaffold will be addressed, indicating 3DP as a positive bridging technology for future scaffold with integrated and localized vibratory functions.

miR-34a exerts as a key regulator in the dedifferentiation of osteosarcoma via PAI-1-Sox2 axis

Osteosarcoma (OS) is a malignant bone cancer with severe chromosomal abnormalities and genetic aberrations. Our previous work reported the dedifferentiation of OS, which is related to poor prognosis. However, the molecular mechanism that regulates OS dedifferentiation is still a subject of exploration. Emerging evidence has suggested that microRNAs (miRNAs) are associated with the pathogenesis of OS and could potentially be developed for use as diagnostic biomarkers and therapeutic strategies. In the present study, we intended to illustrate the role of miR-34a in the dedifferentiation of OS. Upregulation of miR-34a was observed while OS cells were induced into stem-like phenotype. Notably, inhibition of miR-34a could promote the reprogramming transition of OS. Further exploration on the downstream network of miR-34a identified that blocking plasminogen activator inhibitor-1 (PAI-1) expression could restrain OS dedifferentiation into cancer stem-like cells by downregulating SRY-related-HMG box (Sox) 2. We also showed that Sox2 overexpression rescued the suppression phenotype driven by PAI-1 inhibition. Conversely, PAI-1 inhibitor (PAI-039) could suppress the upregulation of Sox2 expression caused by miR-34a inhibition. Be applying bone extracellular matrix (BEM)-OS models, we demonstrated the phenotypic heterogeneity of OS cells, consistent with a strong concordance between PAI-1 and Sox2 expression levels. Taken together, our findings proved miR-34a to be a bona fide suppressor involved in the regulation of OS dedifferentiation. Targeting miR-34a or its direct target PAI-1 could offer new strategies for OS treatment.

Laser micro-ablation of fibrocartilage tissue: Effects of tissue processing on porosity modification and mechanics

The temporomandibular joint disk (TMJd) is an extremely dense and avascular fibrocartilaginous extracellular matrix (ECM) resulting in a limited regenerative capacity. The use of decellularized TMJd as a biocompatible scaffold to guide tissue regeneration is restricted by innate subcellular porosity of the ECM that hinders cellular infiltration and regenerative events. Incorporation of an artificial microporosity through laser micro-ablation (LMA) can alleviate these cell and diffusion based limitations. In this study, LMA was performed either before or after decellularization to assess to effect of surfactant treatment on porosity modification as well as the resultant mechanical and physical scaffold properties. Under convective flow or agitation schemes, pristine and laser ablated disks were decellularized using either low (0.1% w/v) or high (1% w/v) concentrations of sodium dodecyl sulfate (SDS). Results show that lower concentrations of SDS minimized collagen degradation and tissue swelling while retaining its capacity to solubilize cellular content. Regardless of processing scheme, laser ablated channels incorporated after SDS treatment were relatively smaller and more uniform than those incorporated before SDS treatment, indicating an altered laser interaction with surfactant treated tissues. Smaller channels correlated with less disruption of native biomechanical properties indicating surfactant pre-treatment is an important consideration when using LMA to produce artificial porosity in ex vivo derived tissues. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1858-1868, 2018.

Functionality of decellularized matrix in cartilage regeneration: A comparison of tissue versus cell sources

Increasing evidence indicates that decellularized extracellular matrices (dECMs) derived from cartilage tissues (T-dECMs) or chondrocytes/stem cells (C-dECMs) can support proliferation and chondrogenic differentiation of cartilage-forming cells. However, few review papers compare the differences between these dECMs when they serve as substrates for cartilage regeneration. In this review, after an introduction of cartilage immunogenicity and decellularization methods to prepare T-dECMs and C-dECMs, a comprehensive comparison focuses on the effects of T-dECMs and C-dECMs on proliferation and chondrogenic differentiation of chondrocytes/stem cells in vitro and in vivo. Key factors within dECMs, consisting of microarchitecture characteristics and micromechanical properties as well as retained insoluble and soluble matrix components, are discussed in-depth for potential mechanisms underlying the functionality of these dECMs in regulating chondrogenesis. With this information, we hope to benefit dECM based cartilage engineering and tissue regeneration for future clinical application.

STATEMENT OF SIGNIFICANCE

The use of decellularized extracellular matrix (dECM) is becoming a promising approach for tissue engineering and regeneration. Compared to dECM derived from cartilage tissue, recently reported dECM from cell sources exhibits a distinct role in cell based cartilage regeneration. In this review paper, for the first time, tissue and cell based dECMs are comprehensively compared for their functionality in cartilage regeneration. This information is expected to provide an update for dECM based cartilage regeneration.

Calcium and phosphate ions as simple signaling molecules with versatile osteoinductivity

Due to the continually increasing clinical need to heal large bone defects, synthetic bone graft substitutes have become ever more necessary with calcium phosphates (CaP) widely used due to their similarity to the mineral component of bone. In this research, different concentrations of calcium ions (Ca²⁺), phosphate ions (P_i), or their combination were provided to mesenchymal stem cells (MSCs) to evaluate their influence on proliferation and differentiation. The results suggest that 1-16 mM Ca²⁺ and 1-8 mM P_i is osteoinductive, but not cytotoxic. Furthermore, three distinct calcium phosphates (i.e. monobasic, dibasic, and hydroxyapatite) with different dissolution rates were investigated for their Ca²⁺ and P_i release. These biomaterials were then adjusted to release ion concentrations within the established therapeutics window for which MSC bioactivity was assessed. These findings suggest that CaP-based biomaterials can be leveraged to achieve Ca²⁺ and P_i dose-dependent osteoinduction for bone regenerative engineering applications.

An immortalised mesenchymal stem cell line maintains mechano-responsive behaviour and can be used as a reporter of substrate stiffness

The mechanical environment can influence cell behaviour, including changes to transcriptional and proteomic regulation, morphology and, in the case of stem cells, commitment to lineage. However, current tools for characterizing substrates' mechanical properties, such as atomic force microscopy (AFM), often do not fully recapitulate the length and time scales over which cells 'feel' substrates. Here, we show that an immortalised, clonal line of human mesenchymal stem cells (MSCs) maintains the responsiveness to substrate mechanics observed in primary cells, and can be used as a reporter of stiffness. MSCs were cultured on soft and stiff polyacrylamide hydrogels. In both primary and immortalised MSCs, stiffer substrates promoted increased cell spreading, expression of lamin-A/C and translocation of mechano-sensitive proteins YAP1 and MKL1 to the nucleus. Stiffness was also found to regulate transcriptional markers of lineage. A GFP-YAP/RFP-H2B reporter construct was designed and virally delivered to the immortalised MSCs for in situ detection of substrate stiffness. MSCs with stable expression of the reporter showed GFP-YAP to be colocalised with nuclear RFP-H2B on stiff substrates, enabling development of a cellular reporter of substrate stiffness. This will facilitate mechanical characterisation of new materials developed for applications in tissue engineering and regenerative medicine.

Injectable cartilaginous template transformed BMSCs into vascularized bone

Regeneration of alveolar bone for dental implant remains a major issue, partifcularly for patients suffering from severe bone adsorption and irregular socket trauma. Recapitulating embryological development is becoming an attractive approach for engineer organ or three-dimensional tissues from stem cells. In this study, we aimed to develop an injectable “cartilaginous” graft with adequate mechanical resistance and ideal bone remodelling potential. The cartilaginous graft was composed of a particulate decellularised cartilage matrix (PDCM), chondrogenically primed bone mesenchymal stem cell (BMSC) bricks (CB), and enriched platelet-rich plasma (P) gel. In immunodeficient mice, we found that angiogenesis occurred quickly inside PDCM-CB-P constructs after implantation, thereby improving tissue survival and bone formation. In rabbit tibia bone defects around implants, we confirmed that CBs not only transformed into bone tissue rapidly, but also significantly promoted bone remodelling and replacement of PDCM, thus realising osseointegration of dental implants within 3 months. In conclusion, CBs exhibited the potential for endochondral ossification in vivo, and application of a cartilaginous template composed of PDCM, CB, and P provided a minimally-invasive, “free material residual” approach to regenerate alveolar bone tissues in vivo. This method could have applications in peri-implant bone regeneration.

Decellularized Cartilage Directs Chondrogenic Differentiation: Creation of a Fracture Callus Mimetic

Complications that arise from impaired fracture healing have considerable socioeconomic implications. Current research in the field of bone tissue engineering predominantly aims to mimic the mature bone tissue microenvironment. This approach, however, may produce implants that are intrinsically unresponsive to the cues present during the initiation of fracture repair. As such, this study describes the development of decellularized xenogeneic hyaline cartilage matrix in an attempt to mimic the initial reparative phase of fracture repair. Three approaches based on vacuum-assisted osmotic shock (Vac-OS), Triton X-100 (Vac-STx), and sodium dodecyl sulfate (Vac-SDS) were investigated. The Vac-OS methodology reduced DNA content below 50 ng/mg of tissue, while retaining 85% of the sulfate glycosaminoglycan content, and as such was selected as the optimal methodology for decellularization. The resultant Vac-OS scaffolds (decellularized extracellular matrix [dcECM]) were also devoid of the immunogenic alpha-Gal epitope. Furthermore, minimal disruption to the structural integrity of the dcECM was demonstrated using differential scanning calorimetry and fluorescence lifetime imaging microscopy. The biological integrity of the dcECM was confirmed by its ability to drive the chondrogenic commitment and differentiation of human chondrocytes and periosteum-derived cells, respectively. Furthermore, histological examination of dcECM constructs implanted in immunocompetent mice revealed a predominantly M2 macrophage-driven regenerative response both at 2 and 8 weeks postimplantation. These findings contrasted with the implanted native costal cartilage that elicited a predominantly M1 macrophage-mediated inflammatory response. This study highlights the capacity of dcECM from the Vac-OS methodology to direct the key biological processes of endochondral ossification, thus potentially recapitulating the callus phase of fracture repair.

Spiral Layer-by-Layer Micro-Nanostructured Scaffolds for Bone Tissue Engineering

This Article reports the fabrication and characterization of composite micro-nanostructured spiral scaffolds functionalized with nanofibers and hydroxyapatite (HA) for bone regeneration. The spiral poly(lactic acid-co-glycolic acid) (PLGA) porous microstructure was coated with sparsely spaced PLGA nanofibers and HA to enhance surface area and bioactivity. Polyelectrolyte-based HA coating in a layer-by-layer (LBL) fashion allowed 10-70 μM Ca²⁺/mm² incorporation. These scaffolds provided a controlled release of Ca²⁺ ions up to 60 days with varied release kinetics accounting up to 10-50 μg. Spiral scaffolds supported superior adhesion, proliferation, and osteogenic differentiation of rat bone marrow stromal cells (MSCs) as compared to controls microstructures. Spiral micro-nanostructures supported homogeneous tissue ingrowth and resulted in bone-island formation in the center of the scaffold as early as 3 weeks in a rabbit ulnar bone defect model. In contrast, control cylindrical scaffolds showed tissue ingrowth only at the surface because of limitations in scaffold transport features.

Biofunctionalized peptide nanofiber-based composite scaffolds for bone regeneration

Bone tissue had moderate self-healing capabilities, but biomaterial scaffolds were required for the repair of some defects such as large bone defects. Peptide nanofiber scaffolds demonstrated important potential in regenerative medicine. Functional modification and controlled release of signal molecules were two significant approaches to increase the bioactivity of biofunctionalized peptide nanofiber scaffolds, but peptide scaffolds were limited by insufficient mechanical strength. Thus, it was necessary to combine peptide scaffolds with other materials including polymers, hydroxyapatite, demineralized bone matrix (DBM) and metal materials based on the requirement of different bone defects. As the development of peptide-based composite scaffolds continued to evolve, ultimate translation to the clinical environment may allow for improved therapeutic outcomes for bone repair.

The effect of decellularized tissue engineered constructs on periodontal regeneration

AIM

To evaluate the effect of decellularized tissue engineered constructs on cell differentiation in vitro and periodontal regeneration in vivo.

MATERIALS AND METHODS

Periodontal ligament cell (PDLC) sheets were loaded on polycaprolactone (PCL) scaffolds and then decellularized. Constructs were assessed for their effect on allogenic PDLC and mesenchymal stem cell (MSC) differentiation in vitro, as evaluated by gene expression of bone and periodontal ligament tissue markers post-seeding. Expression of MSC marker STRO-1 was assessed by immunostaining. Decellularized constructs were evaluated in a rat periodontal defect model to assess their biocompatibility and tissue integration. Microcomputed topography (μCT) and histological assessment were performed to assess the regenerative potential of the constructs at 2 and 4 weeks postoperatively.

RESULTS

There was upregulation of bone marker gene expression by PDLCs especially on the 14th day. MSCs lacked bone markers expression, but showed increased collagen I marker expression on day 14. STRO-1 expression by the MSCs decreased over the three timepoints when seeded on decellularized sheets. Histological assessment demonstrated the biocompatibility of the decellularized constructs in vivo. More new attachment formation was observed on the decellularized constructs compared to scaffold only controls.

CONCLUSION

Decellularized tissue engineered constructs are capable of inducing cell differentiation in vitro and have the potential to facilitate periodontal regeneration in vivo.

Tissue Engineered Bone Differentiated From Human Adipose Derived Stem Cells Inhibit Posterolateral Fusion in an Athymic Rat Model

STUDY DESIGN

Biological augmentation spinal arthrodesis trial in athymic rats.

OBJECTIVE

To assess the efficacy of tissue-engineered bone to promote L4-L5 intertransverse process fusion in an athymic rat model.

SUMMARY OF BACKGROUND DATA

Each year in the United States, over 400,000 spinal fusion surgeries are performed requiring bone graft. The current gold standard for posterolateral lumbar fusion is autogenous iliac crest bone graft (ICBG), but the harvesting of ICBG is associated with increased operative time and significant complications. This being the case, an alternative cost-effective bone graft source is needed.

METHODS

Bovine bone cores were sterilized and decellularized for scaffold production. Human adipose derived mesenchymal stem cells (ADSC) were obtained and verified by tridifferentiation testing and seeded onto dried scaffolds. The seeded cores were cultured for 5 weeks in culture medium designed to mimic endochondral ossification and produce hypertrophic chondrocytes. Single-level intertransverse process fusions were performed at the L4-L5 level of 31 athymic rats. Fifteen rats were implanted with the hypertrophic chondrocyte seeded scaffold and 16 had scaffold alone. Half of the study rats were sacrificed at 3 weeks and the other half at 6 weeks. Spinal fusion was assessed using 2D and 3D micro computed tomography (μCT) analysis and tissue histology.

RESULTS

At 3 weeks, none of the tissue engineered rats had partial or complete fusion, whereas 62.5% of the decellularized rats fused and another 12.5% had partial fusions (P = 0.013). At 6 weeks, none of the tissue engineered rats fused and 50% had partial fusions, whereas 87.5% of the decellularized rats fused (P = 0.002).

CONCLUSION

Tissue engineered bone composed of hypertrophic chondrocytes inhibits posterolateral fusion in an athymic rat model and therefore does not represent a promising cost-effective bone graft substitute.

LEVEL OF EVIDENCE

N/A.

Inhibition of osteoclastogenesis by stem cell-derived extracellular matrix through modulation of intracellular reactive oxygen species

Decellularized extracellular matrix (ECM) derived from stem cells has been shown as a promising biomaterial for bone regeneration because of the promotion effect on osteogenesis in mesenchymal stem cells (MSCs). However, bone regeneration is also influenced by bone resorption and little is known about the effect of cell-derived ECM on osteoclast differentiation. In this study, ECM was deposited by MSCs and, after decellularization, the effect of ECM on osteoclastogenesis of bone marrow monocytes (BMMs) was investigated in comparison to standard tissue culture polystyrene. Our results showed that cell-derived ECM improved BMM proliferation but potently inhibited osteoclast differentiation, evidenced by down-regulation of multinucleated tartrate-resistant acid phosphatase (TRAP)-positive cells, areas of actin rings, and osteoclast-specific gene expression. ECM-mediated attenuation of intracellular reactive oxygen species (ROS) was suggested to play a rival role in the inhibition of osteoclastogenesis, because exogenous hydrogen peroxide supplementation partially rescued the ECM-inhibited osteoclastogenesis. Furthermore, rather than collagen type I, fibronectin in the ECM contributed to ECM-mediated anti-osteoclastogenesis. In conclusion, stem cell-derived decellularized ECM significantly suppressed osteoclastogenesis via the attenuation of intracellular ROS. The anti-osteoclastogenic property of cell-derived ECM may benefit its clinical use for modulating bone remodeling and promoting bone tissue engineering.

STATEMENT OF SIGNIFICANCE

Decellularized extracellular matrix (ECM) derived from stem cells has been shown as a promising biomaterial for bone regeneration; however, bone remodeling is influenced by bone resorption and little is known about the effect of cell-derived ECM on osteoclast differentiation. Cell-derived ECM improved BMM proliferation but potently inhibited osteoclast differentiation. ECM-mediated attenuation of intracellular reactive oxygen species was suggested to play a rival role in osteoclastogenesis. Fibronectin in cell-derived ECM also contributed to ECM-mediated anti-osteoclastogenesis. The anti-osteoclastogenic property of cell-derived ECM may benefit clinically for modulating bone remodeling and promoting bone tissue engineering.

Effect of hyaluronic acid hydrogels containing astrocyte-derived extracellular matrix and/or V2a interneurons on histologic outcomes following spinal cord injury

One reason for the lack of regeneration, and poor clinical outcomes, following central nervous system (CNS) injury is the formation of a glial scar that inhibits new axon growth. In addition to forming the glial scar, astrocytes have been shown to be important for spontaneous SCI recovery in rodents, suggesting some astrocyte populations are pro-regenerative, while others are inhibitory following injury. In this work, the effect of implanting hyaluronic acid (HA) hydrogels containing extracellular matrix (ECM) harvested from mouse embryonic stem cell (mESC)-derived astrocytes on histologic outcomes following SCI in rats was explored. In addition, the ability of HA hydrogels with and without ECM to support the transplantation of mESC-derived V2a interneurons was tested. The incorporation of ECM harvested from protoplasmic (grey matter) astrocytes, but not ECM harvested from fibrous (white matter) astrocytes, into hydrogels was found to reduce the size of the glial scar, increase axon penetration into the lesion, and reduce macrophage/microglia staining two weeks after implantation. HA hydrogels were also found to support transplantation of V2a interneurons and the presence of these cells caused an increase in neuronal processes both within the lesion and in the 500 μm surrounding the lesion. Overall, protoplasmic mESC-derived astrocyte ECM showed potential to treat CNS injury. In addition, ECM:HA hydrogels represent a novel scaffold with beneficial effects on histologic outcomes after SCI both with and without cells.

Development of Printable Natural Cartilage Matrix Bioink for 3D Printing of Irregular Tissue Shape

The extracellular matrix (ECM) is known to provide instructive cues for cell attachment, proliferation, differentiation, and ultimately tissue regeneration. The use of decellularized ECM scaffolds for regenerative-medicine approaches is rapidly expanding. In this study, cartilage acellular matrix (CAM)-based bioink was developed to fabricate functional biomolecule-containing scaffolds. The CAM provides an adequate cartilage tissue-favorable environment for chondrogenic differentiation of cells. Conventional manufacturing techniques such as salt leaching, solvent casting, gas forming, and freeze drying when applied to CAM-based scaffolds cannot precisely control the scaffold geometry for mimicking tissue shape. As an alternative to the scaffold fabrication methods, 3D printing was recently introduced in the field of tissue engineering. 3D printing may better control the internal microstructure and external appearance because of the computer-assisted construction process. Hence, applications of the 3D printing technology to tissue engineering are rapidly proliferating. Therefore, printable ECM-based bioink should be developed for 3D structure stratification. The aim of this study was to develop printable natural CAM bioink for 3D printing of a tissue of irregular shape. Silk fibroin was chosen to support the printing of the CAM powder because it can be physically cross-linked and its viscosity can be easily controlled. The newly developed CAM-silk bioink was evaluated regarding printability, cell viability, and tissue differentiation. Moreover, we successfully demonstrated 3D printing of a cartilage-shaped scaffold using only this CAM-silk bioink. Future studies should assess the efficacy of in vivo implantation of 3D-printed cartilage-shaped scaffolds.

Understanding interactions between biomaterials and biological systems using proteomics

The role that biomaterials play in the clinical treatment of damaged organs and tissues is changing. While biomaterials used in permanent medical devices were required to passively take over the function of a damaged tissue in the long term, current biomaterials are expected to trigger and harness the self-regenerative potential of the body in situ and then to degrade, the foundation of regenerative medicine. To meet these different requirements, it is imperative to fully understand the interactions biomaterials have with biological systems, in space and in time. This knowledge will lead to a better understanding of the regenerative capabilities of biomaterials aiding their design with improved functionalities (e.g. biocompatibility, bioactivity). Proteins play a pivotal role in the interaction between biomaterials and cells or tissues. Protein adsorption on the material surface is the very first event of this interaction, which is determinant for the subsequent processes of cell growth, differentiation, and extracellular matrix formation. Against this background, the aim of the current review is to provide insight in the current knowledge of the role of proteins in cell-biomaterial and tissue-biomaterial interactions. In particular, the focus is on proteomics studies, mainly using mass spectrometry, and the knowledge they have generated on protein adsorption of biomaterials, protein production by cells cultured on materials, safety and efficacy of new materials based on nanoparticles and the analysis of extracellular matrices and extracellular matrix-derived products. In the outlook, the potential and limitations of this approach are discussed and mass spectrometry imaging is presented as a powerful technique that complements existing mass spectrometry techniques by providing spatial molecular information about the material-biological system interactions.

3D Printing and Electrospinning of Composite Hydrogels for Cartilage and Bone Tissue Engineering

Injuries of bone and cartilage constitute important health issues costing the National Health Service billions of pounds annually, in the UK only. Moreover, these damages can become cause of disability and loss of function for the patients with associated social costs and diminished quality of life. The biomechanical properties of these two tissues are massively different from each other and they are not uniform within the same tissue due to the specific anatomic location and function. In this perspective, tissue engineering (TE) has emerged as a promising approach to address the complexities associated with bone and cartilage regeneration. Tissue engineering aims at developing temporary three-dimensional multicomponent constructs to promote the natural healing process. Biomaterials, such as hydrogels, are currently extensively studied for their ability to reproduce both the ideal 3D extracellular environment for tissue growth and to have adequate mechanical properties for load bearing. This review will focus on the use of two manufacturing techniques, namely electrospinning and 3D printing, that present promise in the fabrication of complex composite gels for cartilage and bone tissue engineering applications.