The Use of Autologous Chondrocyte and Mesenchymal Stem Cell Implants for the Treatment of Focal Chondral Defects in Human Knee Joints—A Systematic Review and Meta-Analysis

Focal chondral defects of the knee occur commonly in the young, active population due to trauma. Damage can insidiously spread and lead to osteoarthritis with significant functional and socioeconomic consequences. Implants consisting of autologous chondrocytes or mesenchymal stem cells (MSC) seeded onto scaffolds have been suggested as promising therapies to restore these defects. However, the degree of integration between the implant and native cartilage still requires optimization. A PRISMA systematic review and meta-analysis was conducted using five databases (PubMed, MEDLINE, EMBASE, Web of Science, CINAHL) to identify studies that used autologous chondrocyte implants (ACI) or MSC implant therapies to repair chondral defects of the tibiofemoral joint. Data on the integration of the implant-cartilage interface, as well as outcomes of clinical scoring systems, were extracted. Most eligible studies investigated the use of ACI only. Our meta-analysis showed that, across a total of 200 patients, 64% (95% CI (51%, 75%)) achieved complete integration with native cartilage. In addition, a pooled improvement in the mean MOCART integration score was observed during post-operative follow-up (standardized mean difference: 1.16; 95% CI (0.07, 2.24), p = 0.04). All studies showed an improvement in the clinical scores. The use of a collagen-based scaffold was associated with better integration and clinical outcomes. This review demonstrated that cell-seeded scaffolds can achieve good quality integration in most patients, which improves over time and is associated with clinical improvements. A greater number of studies comparing these techniques to traditional cartilage repair methods, with more inclusion of MSC-seeded scaffolds, should allow for a standardized approach to cartilage regeneration to develop.     

Implantation of Various Cell-Free Matrixes Does Not Contribute to the Restoration of Hyaline Cartilage within Full-Thickness Focal Defects

Articular cartilage is a highly organized tissue that has a limited ability to heal. Tissue engineering is actively exploited for joint tissue reconstruction in numerous cases of articular cartilage degeneration associated with trauma, arthrosis, rheumatoid arthritis, and osteoarthritis. However, the optimal scaffolds for cartilage repair are not yet identified. Here we have directly compared five various scaffolds, namely collagen-I membrane, collagen-II membrane, decellularized cartilage, a cellulose-based implant, and commercially available Chondro-Gide^® (Geistlich Pharma AG, Wolhusen, Switzerland) collagen membrane. The scaffolds were implanted in osteochondral full-thickness defects, formed on adult Wistar rats using a hand-held cutter with a diameter of 2.0 mm and a depth of up to the subchondral bone. The congruence of the articular surface was almost fully restored by decellularized cartilage and collagen type II-based scaffold. The most vivid restoration was observed 4 months after the implantation. The formation of hyaline cartilage was not detected in any of the groups. Despite cellular infiltration into scaffolds being observed in each group except cellulose, neither chondrocytes nor chondro-progenitors were detected. We concluded that for restoration of hyaline cartilage, scaffolds have to be combined either with cellular therapy or morphogens promoting chondrogenic differentiation.     

Evaluation of the chondrogenic differentiation of mesenchymal stem cells on hybrid biomimetic scaffolds

Hybrid materials are widely and promisingly used as scaffolds in cartilage tissue remodeling. In this study, hybrid scaffolds consist of polycaprolactone (PCL), poly(vinyl alcohol) (PVA) with/without gelatin (GEL) to mimic natural cartilage extracellular matrix (ECM) were investigated. Scaffolds were prepared by freeze drying and characterized by scanning electron microscopy and compressive mechanical testing. Biological assays of mesenchymal stem cell (MSC) cultures, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide, and dimethyl methylene blue were performed, and real‐time polymerization chain reaction analysis of the cartilage‐specific ECM gene marker expression was done. The results show an open interconnected porous structure with a compression modulus of 1.27 ± 0.04 MPa. The surface of the scaffolds showed an excellent efficiency in the adhesion and proliferation of MSCs. A significant increase in the proteoglycan content from 3.70 ± 0.96 to 5.4 ± 1.13 μg/mL was observed after 14 days in the PCL–PVA–GEL scaffolds. The expression amount of the sex‐determining region Y–Box 9 (SOX9) and collagen II (COL2) mRNA levels of the MSCs showed significant increases in SOX9 and COL2, respectively in comparison with PCL–PVA scaffold. The study revealed that the aforementioned scaffold as a blend of natural and synthetic polymers may be a promising substrate in tissue engineering for cartilage repair with MSC transplantation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40635.     

Extracellular Matrix Synthesis and Remodeling by Mesenchymal Stromal Cells Is Context-Sensitive

Matrix remodeling could be an important mode of action of multipotent mesenchymal stromal cells (MSC) in extracellular matrix (ECM) disease, but knowledge is limited in this respect. As MSC are well-known to adapt their behavior to their environment, we aimed to investigate if their mode of action would change in response to healthy versus pathologically altered ECM. Human MSC-derived ECM was produced under different culture conditions, including standard culture, culture on Matrigel-coated dishes, and stimulation with the pro-fibrotic transforming growth factor-β1 (TGFβ1). The MSC-ECM was decellularized, characterized by histochemistry, and used as MSC culture substrate reflecting different ECM conditions. MSC were cultured on the different ECM substrates or in control conditions for 2 days. Culture on ECM increased the presence of surface molecules with ECM receptor function in the MSC, demonstrating an interaction between MSC and ECM. In MSC cultured on Matrigel-ECM and TGFβ1-ECM, which displayed a fibrosis-like morphology, gene expression of collagens and decorin, as well as total matrix metalloproteinase (MMP) activity in the supernatant were decreased as compared with control conditions. These results demonstrated that MSC adapt to their ECM environment, which may include pathological adaptations that could compromise therapeutic efficacy.     

Bioprinting of Cartilage with Bioink Based on High-Concentration Collagen and Chondrocytes

The study was aimed at the applicability of a bioink based on 4% collagen and chondrocytes for de novo cartilage formation. Extrusion-based bioprinting was used for the biofabrication. The printing parameters were tuned to obtain stable material flow. In vivo data proved the ability of the tested bioink to form a cartilage within five to six weeks after the subcutaneous scaffold implantation. Certain areas of cartilage formation were detected as early as in one week. The resulting cartilage tissue had a distinctive structure with groups of isogenic cells as well as a high content of glycosaminoglycans and type II collagen.     

Tethered TGF-β1 in a Hyaluronic Acid-Based Bioink for Bioprinting Cartilaginous Tissues

In 3D bioprinting for cartilage regeneration, bioinks that support chondrogenic development are of key importance. Growth factors covalently bound in non-printable hydrogels have been shown to effectively promote chondrogenesis. However, studies that investigate the functionality of tethered growth factors within 3D printable bioinks are still lacking. Therefore, in this study, we established a dual-stage crosslinked hyaluronic acid-based bioink that enabled covalent tethering of transforming growth factor-beta 1 (TGF-β1). Bone marrow-derived mesenchymal stromal cells (MSCs) were cultured over three weeks in vitro, and chondrogenic differentiation of MSCs within bioink constructs with tethered TGF-β1 was markedly enhanced, as compared to constructs with non-covalently incorporated TGF-β1. This was substantiated with regard to early TGF-β1 signaling, chondrogenic gene expression, qualitative and quantitative ECM deposition and distribution, and resulting construct stiffness. Furthermore, it was successfully demonstrated, in a comparative analysis of cast and printed bioinks, that covalently tethered TGF-β1 maintained its functionality after 3D printing. Taken together, the presented ink composition enabled the generation of high-quality cartilaginous tissues without the need for continuous exogenous growth factor supply and, thus, bears great potential for future investigation towards cartilage regeneration. Furthermore, growth factor tethering within bioinks, potentially leading to superior tissue development, may also be explored for other biofabrication applications.     

Determination of cytocompatibility and osteogenesis properties of in situ forming collagen-based scaffolds loaded with bone synthesizing drug for bone tissue engineering

Bone tissue engineering using in situ forming 3D scaffolds can be an alternative to surgically treated scaffolds. This work aimed to develop in situ forming scaffolds using poly (lactic-co-glycolic acid) and a bone synthesizing drug (risedronate) with or without the porogenic agent (collagen). Hybrid scaffolds were formed through solvent-induced phase inversion technique and were morphologically evaluated using scanning electron microscopy (SEM). The effect of scaffolds on Saos-2 cell line viability using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide test besides their effect on cell growth using fluorescence microscope was assessed. Furthermore, alkaline phosphatase (ALP) activity as well as Ca²⁺ deposition on the scaffolds was evaluated. SEM images revealed the porous structure for collagen-based scaffolds. Saos-2 cell proliferation was significantly enhanced with risedronate-loaded scaffolds compared to those lacking the drug. Porous collagen-based scaffolds were more favorable for both the cell growth and the promotion of ALP activity. Furthermore, collagen-based scaffolds promoted the Ca²⁺ deposition compared to their counterparts without collagen. Such results suggest that collagen-based scaffolds offer excellent biocompatibility for bone regeneration, where this biocompatible nature of scaffold leads to the proliferation of cells that lead to the deposition of mineral on the scaffold. Such in situ forming 3D scaffolds provide a promising noninvasive approach for bone tissue engineering.     

A Decellularized Human Limbal Scaffold for Limbal Stem Cell Niche Reconstruction

The transplantation of ex vivo expanded limbal epithelial progenitor cells (LEPCs) on amniotic membrane or fibrin gel is an established therapeutic strategy to regenerate the damaged corneal surface in patients with limbal stem cell deficiency (LSCD), but the long-term success rate is restricted. A scaffold with niche-specific structure and extracellular matrix (ECM) composition might have the advantage to improve long-term clinical outcomes, in particular for patients with severe damage or complete loss of the limbal niche tissue structure. Therefore, we evaluated the decellularized human limbus (DHL) as a biomimetic scaffold for the transplantation of LEPCs. Corneoscleral tissue was decellularized by sodium deoxycholate and deoxyribonuclease I in the presence or absence of dextran. We evaluated the efficiency of decellularization and its effects on the ultrastructure and ECM composition of the human corneal limbus. The recellularization of these scaffolds was studied by plating cultured LEPCs and limbal melanocytes (LMs) or by allowing cells to migrate from the host tissue following a lamellar transplantation ex vivo. Our decellularization protocol rapidly and effectively removed cellular and nuclear material while preserving the native ECM composition. In vitro recellularization by LEPCs and LMs demonstrated the good biocompatibility of the DHL and intrastromal invasion of LEPCs. Ex vivo transplantation of DHL revealed complete epithelialization as well as melanocytic and stromal repopulation from the host tissue. Thus, the generated DHL scaffold could be a promising biological material as a carrier for the transplantation of LEPCs to treat LSCD.     

Decellularized Human Skeletal Muscle as Biologic Scaffold for Reconstructive Surgery

Engineered skeletal muscle tissues have been proposed as potential solutions for volumetric muscle losses, and biologic scaffolds have been obtained by decellularization of animal skeletal muscles. The aim of the present work was to analyse the characteristics of a biologic scaffold obtained by decellularization of human skeletal muscles (also through comparison with rats and rabbits) and to evaluate its integration capability in a rabbit model with an abdominal wall defect. Rat, rabbit and human muscle samples were alternatively decellularized with two protocols: n.1, involving sodium deoxycholate and DNase I; n.2, trypsin-EDTA and Triton X-NH₄OH. Protocol 2 proved more effective, removing all cellular material and maintaining the three-dimensional networks of collagen and elastic fibers. Ultrastructural analyses with transmission and scanning electron microscopy confirmed the preservation of collagen, elastic fibres, glycosaminoglycans and proteoglycans. Implantation of human scaffolds in rabbits gave good results in terms of integration, although recellularization by muscle cells was not completely achieved. In conclusion, human skeletal muscles may be effectively decellularized to obtain scaffolds preserving the architecture of the extracellular matrix and showing mechanical properties suitable for implantation/integration. Further analyses will be necessary to verify the suitability of these scaffolds for in vitro recolonization by autologous cells before in vivo implantation.     

The Effect of Polybutylcyanoacrylate Nanoparticles as a Protos Delivery Vehicle on Dental Bone Formation

Background: Dental implants are commonly used for missing teeth, for which success depends heavily on the quality of the alveolar bone. The creation of an ideal implant site is a key component in shortening the treatment time, which remains clinically challenging. Strontium ranelate (Protos) is an anti-osteoporotic agent which has previously been used to promote bone formation, however the systemic use of Protos has been linked to serious cardiovascular and venous thromboembolic events, thus local delivery strategies may be better suited for this purpose. In this study, a biodegradable, and biocompatible nanocarrier “polybutylcyanoacrylate” (PBCA) loaded with strontium was constructed and its ability to promote bone formation was assessed. Methodology: PBCA nanoparticles loaded with strontium (PBCA-Sr NPs) were synthesized using the emulsion polymerization method, and their physical properties (zeta potential, size and shape) and entrapment efficiency were characterized. Committed MSCs (osteoblasts) were derived from the differentiation of cultured rat mesenchymal stem cells (MSC), which were tested with the PBCA-Sr NPs for cytotoxicity, inflammatory response, bone formation and mineralization. Scanning electron microscopy was performed following a 7-day treatment of PBCA-Sr NPs on decellularized procaine mandibular bone blocks grafted with osteoblasts. Results: Spherical PBCA-Sr NPs of 166.7 ± 2.3 nm, zeta potential of −1.15 ± 0.28 mV with a strontium loading efficiency of 90.04 ± 3.27% were constructed. The presence of strontium was confirmed by energy-dispersive X-ray spectroscopy. Rat committed MSCs incubated in PBCA-Sr NPs for 24 hrs showed viabilities in excess of 90% for concentrations of up to 250 ug/mL, the cellular expression of osteocalcin and alkaline phosphatase were 1.4 and 1.3 times higher than the untreated control, and significantly higher than those treated with strontium alone. Bone formation was evident following osteoblast engraftment on the decellularized procaine mandibular bone block with PBCA-Sr NPs, which appeared superior to those treated with strontium alone. Conclusion: Treatment of committed MSCs with PBCA-Sr NPs showed higher expression of markers of bone formation when compared with strontium alone and which corresponded to greater degree of bone formation observed on the 3-dimensinal decellularized procaine mandibular bone block. Further quantitative analysis on the extent of new bone formation is warranted.     

The Regeneration of Large-Sized and Vascularized Adipose Tissue Using a Tailored Elastic Scaffold and dECM Hydrogels

A dome-shaped elastic poly(l-lactide-co-caprolactone) (PLCL) scaffold with a channel and pore structure was fabricated by a combinative method of 3D printing technology and the gel pressing method (13 mm in diameter and 6.5 mm in thickness) for patient-specific regeneration. The PLCL scaffold was combined with adipose decellularized extracellular matrix (adECM) and heart decellularized extracellular matrix (hdECM) hydrogels and human adipose-derived stem cells (hADSCs) to promote adipogenesis and angiogenesis. These scaffolds had mechanical properties similar to those of native adipose tissue for improved tissue regeneration. The results of the in vitro real-time PCR showed that the dECM hydrogel mixture induces adipogenesis. In addition, the in vivo study at 12 weeks demonstrated that the tissue-engineered PLCL scaffolds containing the hydrogel mixture (hdECM/adECM (80:20)) and hADSCs promoted angiogenesis and adipose tissue formation, and suppressed apoptosis. Therefore, we expect that our constructs will be clinically applicable as material for the regeneration of patient-specific large-sized adipose tissue.     

Towards 3D Bioprinted Spinal Cord Organoids

Three-dimensional (3D) cultures, so-called organoids, have emerged as an attractive tool for disease modeling and therapeutic innovations. Here, we aim to determine if boundary cap neural crest stem cells (BC) can survive and differentiate in gelatin-based 3D bioprinted bioink scaffolds in order to establish an enabling technology for the fabrication of spinal cord organoids on a chip. BC previously demonstrated the ability to support survival and differentiation of co-implanted or co-cultured cells and supported motor neuron survival in excitotoxically challenged spinal cord slice cultures. We tested different combinations of bioink and cross-linked material, analyzed the survival of BC on the surface and inside the scaffolds, and then tested if human iPSC-derived neural cells (motor neuron precursors and astrocytes) can be printed with the same protocol, which was developed for BC. We showed that this protocol is applicable for human cells. Neural differentiation was more prominent in the peripheral compared to central parts of the printed construct, presumably because of easier access to differentiation-promoting factors in the medium. These findings show that the gelatin-based and enzymatically cross-linked hydrogel is a suitable bioink for building a multicellular, bioprinted spinal cord organoid, but that further measures are still required to achieve uniform neural differentiation.     

Three-Dimensional Culture of Cartilage Tissue on Nanogel-Cross-Linked Porous Freeze-Dried Gel Scaffold for Regenerative Cartilage Therapy: A Vibrational Spectroscopy Evaluation

This study presents a set of vibrational characterizations on a nanogel-cross-linked porous freeze-dried gel (NanoCliP-FD gel) scaffold for tissue engineering and regenerative therapy. This scaffold is designed for the in vitro culture of high-quality cartilage tissue to be then transplanted in vivo to enable recovery from congenital malformations in the maxillofacial area or crippling jaw disease. The three-dimensional scaffold for in-plate culture is designed with interface chemistry capable of stimulating cartilage formation and maintaining its structure through counteracting the dedifferentiation of mesenchymal stem cells (MSCs) during the formation of cartilage tissue. The developed interface chemistry enabled high efficiency in both growth rate and tissue quality, thus satisfying the requirements of large volumes, high matrix quality, and superior mechanical properties needed in cartilage transplants. We characterized the cartilage tissue in vitro grown on a NanoCliP-FD gel scaffold by human periodontal ligament-derived stem cells (a type of MSC) with cartilage grown by the same cells and under the same conditions on a conventional (porous) atelocollagen scaffold. The cartilage tissues produced by the MSCs on different scaffolds were comparatively evaluated by immunohistochemical and spectroscopic analyses. Cartilage differentiation occurred at a higher rate when MSCs were cultured on the NanoCliP-FD gel scaffold compared to the atelocollagen scaffold, and produced a tissue richer in cartilage matrix. In situ spectroscopic analyses revealed the cell/scaffold interactive mechanisms by which the NanoCliP-FD gel scaffold stimulated such increased efficiency in cartilage matrix formation. In addition to demonstrating the high potential of human periodontal ligament-derived stem cell cultures on NanoCliP-FD gel scaffolds in regenerative cartilage therapy, the present study also highlights the novelty of Raman spectroscopy as a non-destructive method for the concurrent evaluation of matrix quality and cell metabolic response. In situ Raman analyses on living cells unveiled for the first time the underlying physiological mechanisms behind such improved chondrocyte performance.     

Reinforcement and chemical cross-linking in collagen-based scaffolds in cartilage tissue engineering: a comparative study

Mechanical strength and biocompatibility are issues of most concern for scaffolds in cartilage tissue engineering. Collagen modification is always used to strengthen scaffolds. There are mainly two ways for collagen modification: inclusion of reinforcing phase to form composites and chemical cross-linking. To explore an alternative approach, the collagen hydrogel modified by a reinforcement phase was compared with cross-linking. Collagen-alginate hydrogel (CAH) and collagen hydrogel cross-linked by genipin (CGH), which were different in modification methods, were chosen candidates. A comprehensive study was carried out on mechanical, structural and biological properties including swelling ratio measurement, in vitro degradation, AFM, mechanical test, thermogravimetric analysis, and in vitro cartilage tissue engineering. The results showed that mechanical strength of collagen was more enhanced for CGH than CAH, as evidenced by analysis of swelling ratio, in vitro degradation, AFM, mechanical test and thermostability. MTT and histological results showed that CGH was superior to CAH with less cytotoxicity and more chondrocytes distributed as well as more aggrecan secreted. With the increase in culture time, the cytotoxicity of cross-linker may be alleviated. CGH may provide a more favorable biomimetic environment for cartilage growth. All these indicated that selecting a cross-linker with a minimal cytotoxicity could be more promising for collagen modification, with improvements observed in both physical and biological properties. For reinforcement, it was required that the incorporated component should be equipped with better or equivalent properties compared with collagen. This study provided important implications to engineering collagen-based hydrogels for cartilage graft applications.     

An Injectable Enzymatically Crosslinked and Mechanically Tunable Silk Fibroin/Chondroitin Sulfate Chondro-Inductive Hydrogel

An injectable hybrid hydrogel is synthesized, comprising silk fibroin (SF) and chondroitin sulfate (CS) through di-tyrosine formation bond of SF chains. CS and SF are reported with excellent biocompatibility as tissue engineering scaffolds. Nonetheless, the rapid degradation rate of pure CS scaffolds presents a challenge to effectively recreate articular cartilage. As CS is one of the cartilage extracellular matrix (ECM) components, it has the potential to enhance the biological activity of SF-based hydrogel in terms of cartilage repair. Therefore, altering the CS concentrations (i.e., 0 wt%, 0.25 wt%, 0.5 wt%, 1 wt%, and 2 wt%), which are interpenetrated between SF β-sheets and chains, can potentially adjust the physical, chemical, and mechanical features of these hybrid hydrogels. The formation of β-sheets by 30 days of immersion in de-ionized (DI) water can improve the compression strength of the SF/CS hybrid hydrogels in comparison with the same SF/CS hybrid hydrogels in the dried state. Biological investigation and observation depicts proper cell attachment, proliferation and cell viability for C28/I2 cells. Gene expression of sex-determining region YBox 9 (SOX9), Collagen II α1, and Aggrecan (AGG) exhibits positive C3H10T1/2 growth and expression of cartilage-specific genes in the 0.25 wt% and 0.5 wt% SF/CS hydrogels.     

Calcium phosphates Chitosan-Xanthan composite scaffolds associated with mesenchymal stem cells for regenerative dentistry application

The aim of this study was to synthesize and characterize polymeric porous scaffolds associated with different calcium phosphates (CaP) and Mesenchymal Stem Cells (MSC) for regenerative dentistry application. Chitosan-Xanthan Scaffolds (CX) were associated with 5% of the two CaP types, Hydroxyapatite (HA) and Brushite (BS). For advanced cell therapies, the scaffolds were associated with MSC. The scaffold structures were characterized by X Ray Diffraction (DRX), Fourier Transformed Infrared (FTIR), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy analysis (SEM) and the compressive strength. The in vitro Cytotoxicity was performed and the in vivo Biocompatibility by histomorphometry and inflammatory cells number count. XRD showed the amorphous phase of CX and main peaks of the CaP phases in the HA and BS scaffolds. FTIR showed the amide I and II bands, characteristic of Chitosan, and carboxyl group, characteristic of Xanthan. PO4 bands were found in CaP scaffolds. SEM showed pores and CaP fillers incorporated and adhered to the polymer in the CX-HA, CX-BS, CX-HA + MSC and CX-BS + MSC. Compressive strength and Modulus of Elasticity analysis exhibited higher values for CX-BS scaffolds, followed by CX-HA and CX. All scaffolds showed acceptable cells viability after 24 h and 48 h; however, the CX scaffolds showed higher cell viability in 48 h. CX-BS produced significantly higher inflammatory cells number after 7 and 30 days of implantation. After 60 days of implantation, CX + MSC and CX-HA + MSC showed the lowest inflammatory cells number. The CaP improved the mechanical properties of scaffolds but decreased the cell viability. MSCs improved the inflammatory response after 60 days.     

Composite scaffolds for cartilage tissue engineering based on natural polymers of bacterial origin,thermoplastic poly(3‐hydroxybutyrate) and micro‐fibrillated bacterial cellulose

Cartilage tissue engineering is an emerging therapeutic strategy that aims to regenerate damaged cartilage caused by disease, trauma, ageing or developmental disorder. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials and signalling factors to the defect site. Materials and fabrication technologies are therefore critically important for cartilage tissue engineering in designing temporary, artificial extracellular matrices (scaffolds), which support 3D cartilage formation. Hence, this work aimed to investigate the use of poly(3‐hydroxybutyrate)/microfibrillated bacterial cellulose (P(3HB)/MFC) composites as 3D‐scaffolds for potential application in cartilage tissue engineering. The compression moulding/particulate leaching technique employed in the study resulted in good dispersion and a strong adhesion between the MFC and the P(3HB) matrix. Furthermore, the composite scaffold produced displayed better mechanical properties than the neat P(3HB) scaffold. On addition of 10, 20, 30 and 40 wt% MFC to the P(3HB) matrix, the compressive modulus was found to have increased by 35%, 37%, 64% and 124%, while the compression yield strength increased by 95%, 97%, 98% and 102% respectively with respect to neat P(3HB). Both cell attachment and proliferation were found to be optimal on the polymer‐based 3D composite scaffolds produced, indicating a non‐toxic and highly compatible surface for the adhesion and proliferation of mouse chondrogenic ATDC5 cells. The large pores sizes (60 ‐ 83 µm) in the 3D scaffold allowed infiltration and migration of ATDC5 cells deep into the porous network of the scaffold material. Overall this work confirmed the potential of P(3HB)/MFC composites as novel materials in cartilage tissue engineering. © 2016 Society of Chemical Industry     

Porous Chitosan Scaffolds: A Systematic Study for Choice of Crosslinker and Growth Factor Incorporation

A systematic study was conducted to evaluate the crosslinker and method of incorporation for bovine serum albumin (BSA) into chitosan hybrid scaffolds (CH-ALG) for better cartilage tissue engineering applications. Formaldehyde and sodium tripolyphosphate were used crosslinkers for fabrication of CH-ALG scaffolds using BSA as growth factor by direct incorporation and microencapsulation methods. An in vitro release study of BSA with maximum release (80%) for scaffolds of formaldehyde crosslinked was found. The present findings show that the CH-ALG hybrid scaffolds have been potential use in biomedical applications.     

Piezoelectric Electrospun Fibrous Scaffolds for Bone,Articular Cartilage and Osteochondral Tissue Engineering

Osteochondral tissue (OCT) related diseases, particularly osteoarthritis, number among the most prevalent in the adult population worldwide. However, no satisfactory clinical treatments have been developed to date to resolve this unmet medical issue. Osteochondral tissue engineering (OCTE) strategies involving the fabrication of OCT-mimicking scaffold structures capable of replacing damaged tissue and promoting its regeneration are currently under development. While the piezoelectric properties of the OCT have been extensively reported in different studies, they keep being neglected in the design of novel OCT scaffolds, which focus primarily on the tissue’s structural and mechanical properties. Given the promising potential of piezoelectric electrospun scaffolds capable of both recapitulating the piezoelectric nature of the tissue’s fibrous ECM and of providing a platform for electrical and mechanical stimulation to promote the regeneration of damaged OCT, the present review aims to examine the current state of the art of these electroactive smart scaffolds in OCTE strategies. A summary of the piezoelectric properties of the different regions of the OCT and an overview of the main piezoelectric biomaterials applied in OCTE applications are presented. Some recent examples of piezoelectric electrospun scaffolds developed for potentially replacing damaged OCT as well as for the bone or articular cartilage segments of this interfacial tissue are summarized. Finally, the current challenges and future perspectives concerning the use of piezoelectric electrospun scaffolds in OCT regeneration are discussed.     

Effects of Human and Porcine Adipose Extracellular Matrices Decellularized by Enzymatic or Chemical Methods on Macrophage Polarization and Immunocompetence

The decellularized extracellular matrix (ECM) obtained from human and porcine adipose tissue (AT) is currently used to prepare regenerative medicine bio-scaffolds. However, the influence of these natural biomaterials on host immune response is not yet deeply understood. Since macrophages play a key role in the inflammation/healing processes due to their high functional plasticity between M1 and M2 phenotypes, the evaluation of their response to decellularized ECM is mandatory. It is also necessary to analyze the immunocompetence of macrophages after contact with decellularized ECM materials to assess their functional role in a possible infection scenario. In this work, we studied the effect of four decellularized adipose matrices (DAMs) obtained from human and porcine AT by enzymatic or chemical methods on macrophage phenotypes and fungal phagocytosis. First, a thorough biochemical characterization of these biomaterials by quantification of remnant DNA, lipids, and proteins was performed, thus indicating the efficiency and reliability of both methods. The proteomic analysis evidenced that some proteins are differentially preserved depending on both the AT origin and the decellularization method employed. After exposure to the four DAMs, specific markers of M1 proinflammatory and M2 anti-inflammatory macrophages were analyzed. Porcine DAMs favor the M2 phenotype, independently of the decellularization method employed. Finally, a sensitive fungal phagocytosis assay allowed us to relate the macrophage phagocytosis capability with specific proteins differentially preserved in certain DAMs. The results obtained in this study highlight the close relationship between the ECM biochemical composition and the macrophage’s functional role.