Resurfacing of goat articular cartilage by chondrocytes derived from bone marrow

Research Progress in Hydrogels for Cartilage Organoids

The repair and regeneration of cartilage has always been a hot topic in medical research. Cartilage organoids (CORGs) are special cartilage tissue created using tissue engineering techniques outside the body. These engineered organoids tissues provide models that simulate the complex biological functions of cartilage, opening new possibilities for cartilage regenerative medicine and treatment strategies. However, it is crucial to establish suitable matrix scaffolds for the cultivation of CORGs. In recent years, utilizing hydrogel to culture stem cells and induce their differentiation into chondrocytes has emerged as a promising method for the in vitro construction of CORGs. In this review, the methods for establishing CORGs are summarized and an overview of the advantages and limitations of using matrigel in the cultivation of such organoids is provided. Furthermore, the importance of cartilage tissue ECM and alternative hydrogel substitutes for Matrigel, such as alginate, peptides, silk fibroin, and DNA derivatives is discussed, and the pros and cons of using these hydrogels for the cultivation of CORGs are outlined. Finally, the challenges and future directions in hydrogel research for CORGs are discussed. It is hoped that this article provides valuable references for the design and development of hydrogels for CORGs.

Mesenchymal Stem Cell Studies in the Goat Model for Biomedical Research-A Review of the Scientific Literature

Mesenchymal stem cells (MSCs) are multipotent cells, defined by their ability to self-renew, while maintaining the capacity to differentiate into different cellular lineages, presumably from their own germinal layer. MSCs therapy is based on its anti-inflammatory, immunomodulatory, and regenerative potential. Firstly, they can differentiate into the target cell type, allowing them to regenerate the damaged area. Secondly, they have a great immunomodulatory capacity through paracrine effects (by secreting several cytokines and growth factors to adjacent cells) and by cell-to-cell contact, leading to vascularization, cellular proliferation in wounded tissues, and reducing inflammation. Currently, MSCs are being widely investigated for numerous tissue engineering and regenerative medicine applications. Appropriate animal models are crucial for the development and evaluation of regenerative medicine-based treatments and eventual treatments for debilitating diseases with the hope of application in upcoming human clinical trials. Here, we summarize the latest research focused on studying the biological and therapeutic potential of MSCs in the goat model, namely in the fields of orthopedics, dermatology, ophthalmology, dentistry, pneumology, cardiology, and urology fields.

Fabrication and characterization of microstructure-controllable COL-HA-PVA hydrogels for cartilage repair

Polyvinyl alcohol (PVA) hydrogel has gained interest in cartilage repair because of its highly swollen, porosity, and viscoelastic properties. However, PVA has some deficiencies, such as its poor biocompatibility and microstructure. This research aimed to design novel hydroxyapatite (HA)-collagen (COL)-PVA hydrogels. COL was added to improve cell biocompatibility, and the microstructure of the hydrogels was controlled by fused deposition modeling (FDM). The feasibility of the COL-HA-PVA hydrogels in cartilage repair was evaluated by in vitro and in vivo experiments. The scanning electron microscopy results showed that the hybrid hydrogels had interconnected macropore structures that contained a COL reticular scaffold. The diameter of the macropore was 1.08-1.85 mm, which corresponds to the diameter of the denatured PVA column. The chondrocytes were then seeded in hydrogels to assess the cell viability and formation of the cartilage matrix. The in vitro results revealed excellent cellular biocompatibility. Osteochondral defects (8 mm in diameter and 8 mm in depth) were created in the femoral trochlear of goats, and the defects were implanted with cell-seeded hydrogels, cell-free hydrogels, or a blank control. The in vivo results showed that the COL-HA-PVA hydrogels effectively repaired cartilage defects, especially the conditions inoculated with chondrocyte in advance. This research suggests that the COL-HA-PVA hydrogels have promising application in cartilage repair.

Endochondral Bone Regeneration by Non-autologous Mesenchymal Stem Cells

Mimicking endochondral bone formation is a promising strategy for bone regeneration. To become a successful therapy, the cell source is a crucial translational aspect. Typically, autologous cells are used. The use of non-autologous mesenchymal stromal cells (MSCs) represents an interesting alternative. Nevertheless, non-autologous, differentiated MSCs may trigger an undesired immune response, hampering bone regeneration. The aim of this study was to unravel the influence of the immune response on endochondral bone regeneration, when using xenogeneic (human) or allogeneic (Dark Agouti) MSCs. To this end, chondrogenically differentiated MSCs embedded in a collagen carrier were implanted in critical size femoral defects of immunocompetent Brown Norway rats. Control groups were included with syngeneic/autologous (Brown Norway) MSCs or a cell-free carrier. The amount of neo-bone formation was proportional to the degree of host-donor relatedness, as no full bridging of the defect was observed in the xenogeneic group whereas 2/8 and 7/7 bridges occurred in the allogeneic and the syngeneic group, respectively. One week post-implantation, the xenogeneic grafts were invaded by pro-inflammatory macrophages, T lymphocytes, which persisted after 12 weeks, and anti-human antibodies were developed. The immune response toward the allogeneic graft was comparable to the one evoked by the syngeneic implants, aside from an increased production of alloantibodies, which might be responsible for the more heterogeneous bone formation. Our results demonstrate for the first time the feasibility of using non-autologous MSC-derived chondrocytes to elicit endochondral bone regeneration in vivo. Nevertheless, the pronounced immune response and the limited bone formation observed in the xenogeneic group undermine the clinical relevance of this group. On the contrary, although further research on how to achieve robust bone formation with allogeneic cells is needed, they may represent an alternative to autologous transplantation.

Tissue Engineering: An Alternative to Repair Cartilage

Herein we review the state-of-the-art in tissue engineering for repair of articular cartilage. First, we describe the molecular, cellular, and histologic structure and function of endogenous cartilage, focusing on chondrocytes, collagens, extracellular matrix, and proteoglycans. We then explore in vitro cell culture on scaffolds, discussing the difficulties involved in maintaining or obtaining a chondrocytic phenotype. Next, we discuss the diverse compounds and designs used for these scaffolds, including natural and synthetic biomaterials and porous, fibrous, and multilayer architectures. We then report on the mechanical properties of different cell-loaded scaffolds, and the success of these scaffolds following in vivo implantation in small animals, in terms of generating tissue that structurally and functionally resembles native tissue. Last, we highlight future trends in this field. We conclude that despite major technical advances made over the past 15 years, and continually improving results in cartilage repair experiments in animals, the development of clinically useful implants for regeneration of articular cartilage remains a challenge

The impact of immune response on endochondral bone regeneration

Tissue engineered cartilage substitutes, which induce the process of endochondral ossification, represent a regenerative strategy for bone defect healing. Such constructs typically consist of multipotent mesenchymal stromal cells (MSCs) forming a cartilage template in vitro, which can be implanted to stimulate bone formation in vivo. The use of MSCs of allogeneic origin could potentially improve the clinical utility of the tissue engineered cartilage constructs in three ways. First, ready-to-use construct availability can speed up the treatment process. Second, MSCs derived and expanded from a single donor could be applied to treat several patients and thus the costs of the medical interventions would decrease. Finally, it would allow more control over the quality of the MSC chondrogenic differentiation. However, even though the envisaged clinical use of allogeneic cell sources for bone regeneration is advantageous, their immunogenicity poses a significant obstacle to their clinical application. The aim of this review is to increase the awareness of the role played by immune cells during endochondral ossification, and in particular during regenerative strategies when the immune response is altered by the presence of implanted biomaterials and/or cells. More specifically, we focus on how this balance between immune response and bone regeneration is affected by the implantation of a cartilaginous tissue engineered construct of allogeneic origin.

In vivo cartilage tissue engineering

Background

Biologic treatment options for cartilage injuries require chondrocyte expansion using cell culture. Clinical application is accomplished in two surgical sessions and is expensive. If isolation of chondrocytes and stimulus for proliferation and extracellular matrix synthesis can be achieved in vivo, the treatment can be performed in one session and the cost can be reduced.

Methods

A 2.5-cm diameter full-thickness chondral defect was created in the knees of five groups of sheep. In one group, some of the chondral tissues obtained from the creation of the defect were diced into small pieces and were placed into the defect and were covered with a collagen membrane (MIV group). In the other group, the collagen membrane was soaked in collagenase prior to usage. In the next group, the collagen membrane was soaked in both collagenase and growth factors. Matrix-induced autologous chondrocyte implantation (MACI) was applied to another group in two sessions, and the last group was left untreated. After 15 weeks of follow-up, repair tissues were compared macroscopically, histomorphometrically, and biochemically for tissue concentrations of glycosaminoglycan and type II collagen.

Results

MACI and MIV groups demonstrated better healing than others and were similar. Addition of collagenase or growth factors did not improve the results. Addition of collagenase did not have detrimental effect on the surrounding cartilage.

Conclusions

With the described method, it is possible to obtain comparable results with MACI. Further studies are also needed to see if it works similarly in humans.

Large Animal Models for Osteochondral Regeneration

Namely, in the last two decades, large animal models - small ruminants (sheep and goats), pigs, dogs and horses - have been used to study the physiopathology and to develop new therapeutic procedures to treat human clinical osteoarthritis. For that purpose, cartilage and/or osteochondral defects are generally performed in the stifle joint of selected large animal models at the condylar and trochlear femoral areas where spontaneous regeneration should be excluded. Experimental animal care and protection legislation and guideline documents of the US Food and Drug Administration, the American Society for Testing and Materials and the International Cartilage Repair Society should be followed, and also the specificities of the animal species used for these studies must be taken into account, such as the cartilage thickness of the selected defect localization, the defined cartilage critical size defect and the joint anatomy in view of the post-operative techniques to be performed to evaluate the chondral/osteochondral repair. In particular, in the articular cartilage regeneration and repair studies with animal models, the subchondral bone plate should always be taken into consideration. Pilot studies for chondral and osteochondral bone tissue engineering could apply short observational periods for evaluation of the cartilage regeneration up to 12 weeks post-operatively, but generally a 6- to 12-month follow-up period is used for these types of studies.

Micrometer scale guidance of mesenchymal stem cells to form structurally oriented large-scale tissue engineered cartilage

Current clinical methods to treat articular cartilage lesions provide temporary relief of the symptoms but fail to permanently restore the damaged tissue. Tissue engineering, using mesenchymal stem cells (MSCs) combined with scaffolds and bioactive factors, is viewed as a promising method for repairing cartilage injuries. However, current tissue engineered constructs display inferior mechanical properties compared to native articular cartilage, which could be attributed to the lack of structural organization of the extracellular matrix (ECM) of these engineered constructs in comparison to the highly oriented structure of articular cartilage ECM. We previously showed that we can guide MSCs undergoing chondrogenesis to align using microscale guidance channels on the surface of a two-dimensional (2-D) collagen scaffold, which resulted in the deposition of aligned ECM within the channels and enhanced mechanical properties of the constructs. In this study, we developed a technique to roll 2-D collagen scaffolds containing MSCs within guidance channels in order to produce a large-scale, three-dimensional (3-D) tissue engineered cartilage constructs with enhanced mechanical properties compared to current constructs. After rolling the MSC-scaffold constructs into a 3-D cylindrical structure, the constructs were cultured for 21days under chondrogenic culture conditions. The microstructure architecture and mechanical properties of the constructs were evaluated using imaging and compressive testing. Histology and immunohistochemistry of the constructs showed extensive glycosaminoglycan (GAG) and collagen type II deposition. Second harmonic generation imaging and Picrosirius red staining indicated alignment of neo-collagen fibers within the guidance channels of the constructs. Mechanical testing indicated that constructs containing the guidance channels displayed enhanced compressive properties compared to control constructs without these channels. In conclusion, using a novel roll-up method, we have developed large scale MSC based tissue-engineered cartilage that shows microscale structural organization and enhanced compressive properties compared to current tissue engineered constructs.

STATEMENT OF SIGNIFICANCE

Tissue engineered cartilage constructs made with human mesenchymal stem cells (hMSCs), scaffolds and bioactive factors are a promising solution to treat cartilage defects. A major disadvantage of these constructs is their inferior mechanical properties compared to the native tissue, which is likely due to the lack of structural organization of the extracellular matrix of the engineered constructs. In this study, we developed three-dimensional (3-D) cartilage constructs from rectangular scaffold sheets containing hMSCs in micro-guidance channels and characterized their mechanical properties and metabolic requirements. The work led to a novel roll-up method to embed 2-D microscale structures in 3-D constructs. Further, micro-guidance channels incorporated within the 3-D cartilage constructs led to the production of aligned cell-produced matrix and enhanced mechanical function.

Methodology to Produce Specimen-Specific Models of Vertebrae: Application to Different Species

Image-based continuum-level finite element models have been used for bones to evaluate fracture risk and the biomechanical effects of diseases and therapies, capturing both the geometry and tissue mechanical properties. Although models of vertebrae of various species have been developed, an inter-species comparison has not yet been investigated. The purpose of this study was to derive species-specific modelling methods and compare the accuracy of image-based finite element models of vertebrae across species. Vertebral specimens were harvested from porcine (N = 12), ovine (N = 13) and bovine (N = 14) spines. The specimens were experimentally loaded to failure and apparent stiffness values were derived. Image-based finite element models were generated reproducing the experimental protocol. A linear relationship between the element grayscale and elastic modulus was calibrated for each species matching in vitro and in silico stiffness values, and validated on independent sets of models. The accuracy of these relationships were compared across species. Experimental stiffness values were significantly different across species and specimen-specific models required species-specific linear relationship between image grayscale and elastic modulus. A good agreement between in vitro and in silico values was achieved for all species, reinforcing the generality of the developed methodology.

The Manipulated Mesenchymal Stem Cells in Regenerated Skeletal Tissues

Ample experimental examples have been accumulated during the last 3 decades indicating the ability of exogenous sources of cultured cells to serve as implants accelerating cartilage regeneration in defects of articular surfaces. In some cases, the repair tissues form complete spatial reconstruction of the defect. In other cases, either the spatial reconstruction is incomplete or the quality of the reparative tissue is inadequate. A delayed pace of endochondral ossification in the deep zones of the subchondral region of the defects, or ossification above the tide mark, within the superficial cartilaginous articular regions have been noted. Therefore, even in this promising approach of biological resurfacing procedure results are not certain, and further investigative research efforts are required. In the current study, a comparison of implantations of various cultured cells of four different sources were tested in an avian system. The reparative tissue outcomes are divided into three grades: full regeneration success, partial success, and failure of regeneration according to qualitative histological parameters and quantitative observation of the gross specimen. Defects that failed to regenerate a completely filled lesion were found to contain cells carrying the preskeletal–precartilaginous characteristic marker of FGFR3. The findings based on the above parameters suggest that autogeneic, chondrocytic-enriched bone marrow derived mesenchymal cells are superior to other cell sources for articular cartilage regeneration. Grafting of defects with these cells results in a 100% success rate. Allogeneic limb bud-derived mesenchymal cells and allogeneic embryonal chondrocytes have both reached a success of 75% of completely filled defects. Allogeneic chondrocytic-enriched bone marrow-derived mesenchymal cells yielded a 31% success rate. Untreated defects completely failed to heal. In successfully healed defects no cells of the reparative tissue carry the FGFR3 marker 3 months postimplantation. In partially healed defects, FGFR3 positive staining is present in fibrous cells at the invaginated surface. These latest findings may suggest some kind of proliferation failure in such cases.

Osteogenesis and chondrogenesis of biomimetic integrated porous PVA/gel/V-n-HA/pa6 scaffolds and BMSCs construct in repair of articular osteochondral defect

A novel bi-layered osteochondral scaffold, including of PVA/Gel/V layer for the cartilage and n-HA/PA6 layer for the subchondral bone, has been proposed to evaluate the potential of the engineered of osteochondral grafts in repairing articular osteochondral defects in rabbits. The two different layers of the scaffolds were seeded with allogenic bone marrow-derived stem cells (BMSCs), which were chondrogenically and osteogenically induced respectively. The critical-size osteochondral defects were created in the knees of adult rabbits. The defects were treated with cell-bi-layered constructs (Group A), bi-layered constructs (Group B) and untreated group C as control group. The adhesion, proliferation and differentiation of BMSCs were demonstrated by immunohistochemical staining and scanning electron microscopy (SEM) in vitro. Cell survival was tracked via fluorescent labeling in vivo. Overall, the porous PVA/Gel/V-n-HA/PA6 scaffold was compatible and had no negative effects on the BMSCs in vitro culture. The cell-bi-layered scaffolds showed superior repair results as compared to the control group using gross examination and histological assessment. With BMSCs implantation, the two different layers of the composite biomimetic scaffolds provided a suitable environment for cells to form respective tissue. Simultaneously, the RT-PCR results confirmed the expression of specific extracellular matrix (ECM) markers for cartilaginous or osteoid tissue. This investigation showed that the porous PVA/Gel/V-n-HA/PA6 scaffold is a potential matrix for treatment of osteochondral defects, and the method of using chondrogenically and osteogenically differentiated BMSCs as seed cells on each layer might be a promising strategy in repair of articular osteochondral defect due to enhanced chondrogenesis and osteogenesis.

Treatment with embryonic stem-like cells into osteochondral defects in sheep femoral condyles

Background

Articular cartilage has poor intrinsic capacity for regeneration because of its avascularity and very slow cellular turnover. Defects deriving from trauma or joint disease tend to be repaired with fibrocartilage rather than hyaline cartilage. Consequent degenerative processes are related to the width and depth of the defect. Since mesenchymal stem cells (MSCs) deriving from patients affected by osteoarthritis have a lower proliferative and chondrogenic activity, the systemic or local delivery of heterologous cells may enhance regeneration or inhibit the progressive loss of joint tissue. Embryonic stem cells (ESCs) are very promising, since they can self-renew for prolonged periods without differentiation and can differentiate into tissues from all the 3 germ layers. To date only a few experiments have used ESCs for the study of the cartilage regeneration in animal models and most of them used laboratory animals. Sheep, due to their anatomical, physiological and immunological similarity to humans, represent a valid model for translational studies. This experiment aimed to evaluate if the local delivery of male sheep embryonic stem-like (ES-like) cells into osteochondral defects in the femoral condyles of adult sheep can enhance the regeneration of articular cartilage. Twenty-two ewes were divided into 5 groups (1, 2, 6, 12 and 24 months after surgery). Newly formed tissue was evaluated by macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays.

Results

Regenerated tissue was ultimately evaluated on 17 sheep. Samples engrafted with ES-like cells had significantly better histologic evidence of regeneration with respect to empty defects, used as controls, at all time periods.

Conclusions

Histological assessments demonstrated that the local delivery of ES-like cells into osteochondral defects in sheep femoral condyles enhances the regeneration of the articular hyaline cartilage, without signs of immune rejection or teratoma for 24 months after engraftment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-014-0301-9) contains supplementary material, which is available to authorized users.

Basic science and clinical application of stem cells in veterinary medicine

Stem cells play an important role in veterinary medicine in different ways. Currently several stem cell therapies for animal patients are being developed and some, like the treatment of equine tendinopathies with mesenchymal stem cells (MSCs), have already successfully entered the market. Moreover, animal models are widely used to study the properties and potential of stem cells for possible future applications in human medicine. Therefore, in the young and emerging field of stem cell research, human and veterinary medicine are intrinsically tied to one another. Many of the pioneering innovations in the field of stem cell research are achieved by cooperating teams of human and veterinary medical scientists.Embryonic stem (ES) cell research, for instance, is mainly performed in animals. Key feature of ES cells is their potential to contribute to any tissue type of the body (Reed and Johnson, J Cell Physiol 215:329-336, 2008). ES cells are capable of self-renewal and thus have the inherent potential for exceptionally prolonged culture (up to 1-2 years). So far, ES cells have been recovered and maintained from non-human primate, mouse (Fortier, Vet Surg 34:415-423, 2005) and horse blastocysts (Guest and Allen, Stem Cells Dev 16:789-796, 2007). In addition, bovine ES cells have been grown in primary culture and there are several reports of ES cells derived from mink, rat, rabbit, chicken and pigs (Fortier, Vet Surg 34:415-423, 2005). However, clinical applications of ES cells are not possible yet, due to their in vivo teratogenic degeneration. The potential to form a teratoma consisting of tissues from all three germ lines even serves as a definitive in vivo test for ES cells.Stem cells obtained from any postnatal organism are defined as adult stem cells. Adult haematopoietic and MSCs, which can easily be recovered from extra embryonic or adult tissues, possess a more limited plasticity than their embryonic counterparts (Reed and Johnson, J Cell Physiol 215:329-336, 2008). It is believed that these stem cells serve as cell source to maintain tissue and organ mass during normal cell turnover in adult individuals. Therefore, the focus of attention in veterinary science is currently drawn to adult stem cells and their potential in regenerative medicine. Also experience gained from the treatment of animal patients provides valuable information for human medicine and serves as precursor to future stem cell use in human medicine.Compared to human medicine, haematopoietic stem cells only play a minor role in veterinary medicine because medical conditions requiring myeloablative chemotherapy followed by haematopoietic stem cell induced recovery of the immune system are relatively rare and usually not being treated for monetary as well as animal welfare reasons.In contrast, regenerative medicine utilising MSCs for the treatment of acute injuries as well as chronic disorders is gradually turning into clinical routine. Therefore, MSCs from either extra embryonic or adult tissues are in the focus of attention in veterinary medicine and research. Hence the purpose of this chapter is to offer an overview on basic science and clinical application of MSCs in veterinary medicine.

Tissue-engineered cartilaginous constructs for the treatment of caprine cartilage defects, including distribution of laminin and type IV collagen

The purpose of this study was the immunohistochemical evaluation of (1) cartilage tissue-engineered constructs; and (2) the tissue filling cartilage defects in a goat model into which the constructs were implanted, particularly for the presence of the basement membrane molecules, laminin and type IV collagen. Basement membrane molecules are localized to the pericellular matrix in normal adult articular cartilage, but have not been examined in tissue-engineered constructs cultured in vitro or in tissue filling cartilage defects into which the constructs were implanted. Cartilaginous constructs were engineered in vitro using caprine chondrocyte-seeded type II collagen scaffolds. Autologous constructs were implanted into 4-mm-diameter defects created to the tidemark in the trochlear groove in the knee joints of skeletally mature goats. Eight weeks after implantation, the animals were sacrificed. Constructs underwent immunohistochemical and histomorphometric evaluation. Widespread staining for the two basement membrane molecules was observed throughout the extracellular matrix of in vitro and in vivo samples in a distribution unlike that previously reported for cartilage. At sacrifice, 70% of the defect site was filled with reparative tissue, which consisted largely of fibrous tissue and some fibrocartilage, with over 70% of the reparative tissue bonded to the adjacent host tissue. A novel finding of this study was the observation of laminin and type IV collagen in in vitro engineered cartilaginous constructs and in vivo cartilage repair samples from defects into which the constructs were implanted, as well as in normal caprine articular cartilage. Future work is needed to elucidate the role of basement membrane molecules during cartilage repair and regeneration.

Preferential therapy for osteoarthritis by cord blood MSCs through regulation of chondrogenic cytokines

Osteoarthritis (OA) is a common rheumatic disease associated with imbalanced cartilage homeostasis which could be corrected by mesenchymal stem cells (MSCs) therapy. However, MSCs from different origins might exhibit distinct differentiation capacities. This study was undertaken to compare the therapeutic efficacies between MSCs from cord blood (CB-MSCs) and bone marrow (BM-MSCs) on OA treatment. The surface phenotypes and multipotent capacities of CB-MSCs and BM-MSCs were first characterized. The coculture commitment system was subsequently utilized for comparing the patterned molecules in stage-specific chondrogenesis of committed MSCs. For examining the therapeutic efficacies, committed CB-MSCs and BM-MSCs were encapsulated in neo-cartilage and subjected into pro-inflammatory cytokine environment. Finally, chondrogenic and inflammatory cytokine profiles in committed MSCs were evaluated. CB-MSCs and BM-MSCs were both negative for hematopoietic markers and positive for adhesion and mesenchymal cell markers. The CB-MSCs showed a markedly higher chondrogenic potential and relatively lower osteogenic and adipogenic capacities than BM-MSCs. During chondrogenesis, the committed CB-MSCs also showed significant increases in cell proliferation, adhesion molecules, signaling molecules, and chondrogenic-specific gene expressions in a coculture system. For the therapeutic efficacies, the committed CB-MSCs could strongly recover the pro-inflammatory cytokines diminished-Col II and proteoglycan expressions in a 3D arthritic model. The IL-10, ICAM-1 and TGF-β1 were also up-regulated in committed CB-MSCs analyzed by using cytokine profiling. Our data demonstrate that CB-MSCs possess specific advantages in cartilage regeneration over BM-MSCs. The CB-MSCs showed a better therapeutic potential that can contribute to advanced cell-based transplantation for clinical OA therapy.

The role of environmental factors in regulating the development of cartilaginous grafts engineered using osteoarthritic human infrapatellar fat pad-derived stem cells

Engineering functional cartilaginous grafts using stem cells isolated from osteoarthritic human tissue is of fundamental importance if autologous tissue engineering strategies are to be used in the treatment of diseased articular cartilage. It has previously been demonstrated that human infrapatellar fat pad (IFP)-derived stem cells undergo chondrogenesis in pellet culture; however, the ability of such cells to generate functional cartilaginous grafts has not been adequately addressed. The objective of this study was to explore how environmental conditions regulate the functional development of cartilaginous constructs engineered using diseased human IFP-derived stem cells (FPSCs). FPSCs were observed to display a diminished chondrogenic potential upon encapsulation in a three-dimensional hydrogel compared with pellet culture, synthesizing significantly lower levels of glycosaminoglycan and collagen on a per cell basis. To engineer more functional cartilaginous grafts, we next explored whether additional biochemical and biophysical stimulations would enhance chondrogenesis within the hydrogels. Serum stimulation was observed to partially recover the diminished chondrogenic potential within hydrogel culture. Over 42 days, stem cells that had first been expanded in a low-oxygen environment proliferated extensively on the outer surface of the hydrogel in response to serum stimulation, assembling a dense type II collagen-positive cartilaginous tissue resembling that formed in pellet culture. The application of hydrostatic pressure did not further enhance extracellular matrix synthesis within the hydrogels, but did appear to alter the spatial accumulation of extracellular matrix leading to the formation of a more compact tissue with superior mechanically functionality. Further work is required in order to recapitulate the environmental conditions present during pellet culture within scaffolds or hydrogels in order to engineer more functional cartilaginous grafts using human osteoarthritic FPSCs.

TISSUE ENGINEERING APPROACH TO OSTEOCHONDRAL REPAIR AND REGENERATION

Repair of osteochondral lesions remains difficult in current clinical medicine. This is due to the lack of self-reparatory capacity in adult cartilage to respond to injuries. Furthermore, current surgical based treatment is unable to achieve long-term satisfactory results. Cell therapies combined with scaffolds has become a promising tissue engineering approach for osteochondral regeneration. This article briefly outlines the approaches and limitations in osteochondral tissue engineering from three key aspects, namely: (1) Cells and Cell Source; (2) Biomaterials and Scaffold design and fabrication; and (3) Mechanical and Biochemical Stimulus. Current optimal candidate cells for tissue engineering include bone marrow and adipose tissue derived mesenchymal stem cells. As for scaffolds, the structural design and biomaterials used should support cell growth and the organization of new functional tissue formation. Using Fused Deposition Modeling (FDM) technique, the authors developed a novel polycaprolactone osteochondral scaffold which was shown to have the ability to recruit mesenchymal stem cells and the potential for repairing defects in vivo. The article also discussed mechanical and biological stimulus for enhancing in vitro growth of tissue-engineered constructs. The final challenge is the integration of the tissue-engineered tissues into a living system as a functional device.

COMPARATIVE MACROSCOPIC STUDY OF OSTEOCHONDRAL DEFECTS PRODUCED IN FEMURS OF RABBITS REPAIRED WITH BIOPOLYMER GEL CANE SUGAR

OBJECTIVE

To study the surface, coloring, consistency, continuity and healing of osteochondral defects produced in the femoral condyles of rabbits and filled with sugar cane biopolymer gel (SCBG), after 90, 120 and 180 days, and in comparison with a control group.

METHOD

Sixteen adult New Zealand white rabbits aged 6 to 7 months, weighing between 2 and 2.5 kg and without locomotor system abnormalities were studied. In all the animals, a defect was made in the femoral condyles of the right and left knees, measuring 3.2 mm in diameter and 4 mm in depth, using a trephine. The animals were divided into two groups: study group formed by the right knees, in which the medial and lateral condyles received implants of SCBG; and control group formed by the left knees, in which the medial and lateral condyles were allowed to heal naturally. The knees were assessed 90, 120 and 180 days after the operation. After the animals had been sacrificed, the anatomical specimens were resected and placed in Bouin's solution. They were then photographed with a Nikon Coolpix 5400(®) coupled to a Nikon SM2800(®) stereoscopic loupe, to analyze the surface, coloring, consistency, continuity and healing.

RESULTS

The results were evaluated using the chi-square test. There were no significant differences in the macroscopic assessments of healing between the study and control groups.

CONCLUSION

With regard to the surface, coloring, consistency, continuity and healing of the defects, the macroscopic appearance of the tissue repaired with SCBG was similar to that of the control group.

Matrix-associated implantation of predifferentiated mesenchymal stem cells versus articular chondrocytes: in vivo results of cartilage repair after 1 year

BACKGROUND

The use of predifferentiated mesenchymal stem cells (MSC) leads to better histological results compared with undifferentiated MSC in sheep. This raises the need for a longer term follow-up study and comparison with a clinically established method.

HYPOTHESIS

We hypothesized that chondrogenic in vitro predifferentiation of autologous MSC embedded in a collagen I hydrogel leads to better structural repair of a chronic osteochondral defect in an ovine stifle joint after 1 year. We further hypothesized that resulting histological results would be comparable with those of chondrocyte-seeded matrix-associated autologous chondrocyte transplantation (MACT).

STUDY DESIGN

Controlled laboratory study.

METHODS

Predifferentiation period of ovine MSC within collagen gel in vitro was defined by assessment of several cellular and molecular biological parameters. For the animal study, 2 osteochondral lesions (7-mm diameter) were created at the medial femoral condyles of the hind legs in 9 sheep. Implantation of MSC gels was performed 6 weeks after defect creation. Thirty-six defects were divided into 4 treatment groups: (1) chondrogenically predifferentiated MSC gels (pre-MSC gels), (2) undifferentiated MSC gels (un-MSC gels), (3) MACT gels, and (4) untreated controls (UC). Histological, immunohistochemical, and radiological evaluations followed after 12 months.

RESULTS

After 12 months in vivo, pre-MSC gels showed significantly better histological outcome compared with un-MSC gels and UC. Compared with MACT gels, the overall scores were higher for O'Driscoll and International Cartilage Repair Society (ICRS). The repair tissue of the pre-MSC group showed immunohistochemical detection of interzonal collagen type II staining. Radiological evaluation supported superior bonding of pre-MSC gels to perilesional native cartilage. Compared with previous work by our group, no degradation of the repair tissue between 6 and 12 months in vivo, particularly in pre-MSC gels, was observed.

CONCLUSION

Repair of chronic osteochondral defects with collagen hydrogels composed of chondrogenically predifferentiated MSC shows no signs of degradation after 1 year in vivo. In addition, pre-MSC gels lead to partially superior histological results compared with articular chondrocytes.

CLINICAL RELEVANCE

The results suggest an encouraging method for future treatment of focal osteochondral defects without donor site morbidity by harvesting articular chondrocytes.

Chondrogenic differentiation of bone marrow-derived mesenchymal stem cells: tips and tricks

It is well known that adult cartilage lacks the ability to repair itself; this makes articular cartilage a very attractive target for tissue engineering. The majority of articular cartilage repair models attempt to deliver or recruit reparative cells to the site of injury. A number of efforts are directed to the characterization of progenitor cells and the understanding of the mechanisms involved in their chondrogenic differentiation. Our laboratory has focused on cartilage repair using mesenchymal stem cells and studied their differentiation into cartilage. Mesenchymal stem cells are attractive candidates for cartilage repair due to their osteogenic and chondrogenic potential, ease of harvest, and ease of expansion in culture. However, the need for chondrogenic differentiation is superposed on other technical issues associated with cartilage repair; this adds a level of complexity over using mature chondrocytes. This chapter will focus on the methods involved in the isolation and expansion of human mesenchymal stem cells, their differentiation along the chondrogenic lineage, and the qualitative and quantitative assessment of chondrogenic differentiation.

Use of synovium-derived stromal cells and chitosan/collagen type I scaffolds for cartilage tissue engineering

The objective was to investigate synovium-derived stromal cells (SDSCs) coupled with chitosan/collagen type I (CS/COL-I) scaffolds for cartilage engineering. CS/COL-I scaffolds were fabricated through freeze-drying and cross-linked by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. SDSCs were isolated from synovium and cultured onto CS/COL-I scaffolds, constructs of which were incubated in serum-free chondrogenic medium with sequential application of TGF-β1 and bFGF for up to 21 days and then implanted into nude mice. The physical characteristics of the scaffolds were examined. The quality of the in vitro constructs was assessed in terms of DNA content by PicoGreen assay and cartilaginous matrix by histological examination. The implants of the constructs were evaluated by histological and immunohistochemical examinations and reverse transcription PCR. Results indicated that the CS/COL-I scaffold showed porous structures, and the DNA content of SDSCs in CS/COL-I scaffolds increased at 1 week culture time. Both of the constructs in vitro and the implants were examined with positive stained GAGs histologically and the implants with positive collagen type II immunohistochemically. RT-PCR of the implants indicated that aggrecan and collagen type II expressed. It suggested that SDSCs coupled with CS/COL-I scaffolds treated sequentially with TGF-β1 and bFGF in vitro were highly competent for engineered cartilage formation in vitro and in vivo.

Animal models for cartilage regeneration and repair

Articular cartilage injury and degeneration are leading causes of disability. Animal studies are critically important to developing effective treatments for cartilage injuries. This review focuses on the use of animal models for the study of the repair and regeneration of focal cartilage defects. Animals commonly used in cartilage repair studies include murine, lapine, canine, caprine, porcine, and equine models. There are advantages and disadvantages to each model. Small animal rodent and lapine models are cost effective, easy to house, and useful for pilot and proof-of-concept studies. The availability of transgenic and knockout mice provide opportunities for mechanistic in vivo study. Athymic mice and rats are additionally useful for evaluating the cartilage repair potential of human cells and tissues. Their small joint size, thin cartilage, and greater potential for intrinsic healing than humans, however, limit the translational value of small animal models. Large animal models with thicker articular cartilage permit study of both partial thickness and full thickness chondral repair, as well as osteochondral repair. Joint size and cartilage thickness for canine, caprine, and mini-pig models remain significantly smaller than that of humans. The repair and regeneration of chondral and osteochondral defects of size and volume comparable to that of clinically significant human lesions can be reliably studied primarily in equine models. While larger animals may more closely approximate the human clinical situation, they carry greater logistical, financial, and ethical considerations. A multifactorial analysis of each animal model should be carried out when planning in vivo studies. Ultimately, the scientific goals of the study will be critical in determining the appropriate animal model.

Current concepts in the diagnosis and treatment of osteochondral lesions of the ankle

Osteochondral lesions of the ankle are a more common source of ankle pain than previously recognized. Although the exact pathophysiology of the condition has not been clearly established, it is likely that a variety of etiological factors play a role, with trauma, typically from ankle sprains, being the most common. Technological advancements in ankle arthroscopy and radiologic imaging, most importantly magnetic resonance imaging, have improved diagnostic capabilities for detecting osteochondral lesions of the ankle. Moreover, these technologies have allowed for the development of more sophisticated classification systems that may, in due course, direct specific future treatment strategies. Nonoperative treatment yields best results when employed in select pediatric and adolescent patients with osteochondritis dissecans. However, operative treatment, which is dependent on the size and site of the lesion, as well as the presence or absence of cartilage damage, is frequently warranted in both children and adults with osteochondral lesions. Arthroscopic microdrilling, micropicking, and open procedures, such as osteochondral autograft transfer system and matrix-induced autologous chondrocyte implantation, are frequently employed. The purpose of this article is to review the history, etiology, and classification systems for osteochondral lesions of the ankle, as well as to describe current approaches to diagnosis and management.

Effect of serum and growth factors on chondrogenic differentiation of synovium-derived stromal cells

We used fetal bovine serum (FBS) and different growth factors to investigate their potential for inducing chondrogenic differentiation of synovium-derived stromal cells. Human synovium was harvested from patients suffering from osteoarthritis and expanded in monolayer. To evaluate the effect of serum and growth factors on chondrogenic differentiation, 10 ng/mL of transforming growth factor-beta1 (TGF-beta1), 100 ng/mL of bone morphogenic protein-2 (BMP-2), 100 ng/mL of insulin-like growth factor-1, 20 ng/mL of basic fibroblast growth factor (bFGF), and 10% FBS were added to the chemically defined chondrogenic medium singly or in combination during pellet culture for 21 days. The cell size and weight, glycosaminoglycan content, histology, and cartilage matrix-associated genes expression were analyzed. TGF-beta1 alone and TGF-beta1 + BMP-2 induced chondrogenic differentiation of synovium-derived stromal cells and synthesized cartilage-like matrix confirmed by histological analysis and immunohistochemistry. FBS, BMP-2, insulin-like growth factor-1, and bFGF as a single factor or other combinations except for TGF-beta1 + BMP-2 hardly induced chondrogenesis. Chondrogenic differentiation appeared to be inhibited when bFGF or the serum was added to the chondrogenic medium during pellet culture. The results of this study demonstrate the negative or positive role of serum and growth factors on chondrogenic differentiation of synovium-derived stromal cells.

Effects of chondrogenic microenvironment on construction of cartilage tissues using marrow stromal cells in vitro

OBJECTIVE

To investigate whether it is feasible to use the chondrogenic microenvironment provided by cartilage cells to construct cartilage tissues in vitro with bone marrow stromal cells (BMSC).

MATERIALS AND METHODS

We isolated and cultured BMSC and cartilage cells from Sprague Dawley rats (SD rats). The supernatant of cartilage culture was used as inducing solution to cause differentiation of BMSC from the second generation of cells cultured in vitro. Cells were examined seven days later, using immunohistochemistry to determine the expression of collagen specific to type II cartilage. RT-PCR was used to detect the expression of type II collagen and aggrecan mRNA. BMSC and cartilage cells were isolated from SD rats and cultured in vitro. The BMSC and cartilage cells in culture were mixed evenly in an 8:2 ratio and inoculated into a polyglycolic acid/polylactic acid (PGA/PLA) scaffold to a final concentration of 5.0x10(7) cells/ml. PGA/PLA preparations with pure cartilage cells or pure BMSC served as the positive and negative controls, respectively. The control group of low-concentration cartilage cells consisted of PGA/PLA preparations containing cartilage cells at 20% of the above mentioned concentration (1.0x10(7) cells/ml). Samples were collected eight weeks later, at which time general observations, wet weight, and glycosaminoglycan (GAG) levels were determined, and histological and immunohistochemical examinations were performed.

RESULTS

Immunohistochemistry showed the induction of BMSC type II collagen, and RT-PCR indicated the expression of type II collagen and aggrecan mRNA. In the mixed-cell group and the positive control group, pure mature cartilage cells were produced after eight weeks of culture in vitro, and the size and shape of the scaffold were maintained throughout the culture period. The two groups gave rise to newly generated cartilage cells essentially identical in appearance and histological properties. The immunohistochemical results showed that the cartilage cells of both groups expressed abundant cartilage-specific type II collagen. The average wet weight and GAG content were more than 70% of the values in the positive control group. Only an extremely small amount of immature cartilage tissue formed in local regions in the BMSC-only sample, and the scaffold was obviously shrunken and deformed. Although the wet weight of newly generated cartilage tissue in the low-concentration cartilage cell sample reached 30% of the value of the positive control group, the scaffold was obviously shrunken and deformed. Only regional and discontinuous cartilage tissues were formed, and the amount of newly generated cartilage was obviously less than in the co-culture and positive control groups.

CONCLUSIONS

Cartilage cells can provide a microenvironment for cartilage formation to some extent, and also effectively induce BMSC to differentiate into cartilage cells and form tissue-engineered cartilage in vitro.

Rabbit Articular Chondrocytes Seeded on Collagen-Chitosan-GAG Scaffold for Cartilage Tissue Engineering In Vivo

In this study, we prepared a tri-copolymer porous matrices by natural polymer, collagen (Col), Chitosan (Chi) and Chondroitin (CS). Rabbit articular chondrocytes were isolated from the shoulder articular joints of a rabbit, seeded in Col-Chi-CS scaffold, and implanted subcutaneously in the dorsum of athymic nude mice to tissue engineer articular cartilage in vivo. In vitro studies show that Chondrocytes adhered to the scaffold, where they proliferated and secreted extracellular matrices with time, filling the space within the scaffold. The results of hematoxylin and eosin staining scanning electron microscopy revealed that most of the chondrocytes maintained their typically rounded morphology. After 28 days of culture within Col-Chi-CS scaffold in vitro, the results of histological staining showed forming of cartilage-specific morphological appearance and structural characteristics such as lacunae. Subcutaneous implantation studies in nude mice demonstrated that a homogeneous cartilaginous tissue, which was similar to those of natural cartilage, formed when chondrocytes were seeded in Col-Chi-CS matrix after implant 12 weeks. The tri-copolymer matrix could therefore have potential applications as a three-dimensional scaffold for cartilage tissue engineering.

Success rates and immunologic responses of autogenic, allogenic, and xenogenic treatments to repair articular cartilage defects

This review examines current approaches available for articular cartilage repair, not only in terms of their regeneration potential, but also as a function of immunologic response. Autogenic repair techniques, including osteochondral plug transplantation, chondrocyte implantation, and microfracture, are the most widely accepted clinical treatment options due to the lack of immunogenic reactions, but only moderate graft success rates have been reported. Although suspended allogenic chondrocytes are shown to evoke an immune response upon implantation, allogenic osteochondral plugs and tissue-engineered grafts using allogenic chondrocytes exhibit a tolerable immunogenic response. Additionally, these repair techniques produce neotissue with success rates approaching those of currently available autogenic repair techniques, while simultaneously obviating their major hindrance of donor tissue scarcity. To date, limited research has been performed with xenogenic tissue, although several studies demonstrate the potential for its long-term success. This article focuses on the various treatment options for cartilage repair and their associated success rates and immunologic responses.

Poly-L-lactic acid/hydroxyapatite electrospun nanocomposites induce chondrogenic differentiation of human MSC

Cartilage and bone tissue engineering has been widely investigated but is still hampered by cell differentiation and transplant integration issues within the constructs. Scaffolds represent the pivotal structure of the engineered tissue and establish an environment for neo-extracellular matrix synthesis. They can be associated to signals to modulate cell activity. In this study, considering the well reported role of hydroxyapatite (HA) in cartilage repair, we focused on the putative chondrogenic differentiation of human mesenchymal stem cells (hMSCs) following culture on membranes of electrospun fibers of poly-L-lactic acid (PLLA) loaded with nanoparticles of HA. hMSCs were seeded on PLLA/HA and bare PLLA membranes and cultured in basal medium, using chondrogenic differentiation medium as a positive control. After 14 days of culture, SOX-9 positive cells could be detected in the PLLA/HA group. Cartilage specific proteoglycan immunostain confirmed the presence of neo-extracellular-matrix production. Co-expression of CD29, a typical surface marker of MSCs and SOX-9, suggested different degrees in the differentiation process. We developed a hydroxyapatite functionalized scaffold with the aim to recapitulate the native histoarchitecture and the molecular signaling of osteochondral tissue to facilitate cell differentiation toward chondrocyte. PLLA/HA nanocomposites induced differentiation of hMSCs in a chondrocyte-like phenotype with generation of a proteoglycan based matrix. This nanocomposite could be an amenable alternative scaffold for cartilage tissue engineering using hMSCs.

Articular cartilage degeneration following the treatment of focal cartilage defects with ceramic metal implants and compared with microfracture

BACKGROUND

Localized cartilage defects are frequently associated with joint pain, reduced function, and a predisposition to the development of osteoarthritis. The purposes of the current study were to investigate the feasibility of the application of defect-sized femoral implants for the treatment of localized cartilage defects and to compare this treatment, in terms of joint degeneration, with the use of microfracture in a goat model of established cartilage defects.

METHODS

In nine Dutch milk goats, a defect in the medial femoral condyle was created in both knees. After ten weeks, the knees were randomly treated by microfracture or by placement of an oxidized zirconium implant. At twenty-six weeks after surgery, the animals were killed. The joints were evaluated macroscopically. Implant osseointegration was measured by automated histomorphometry, and cartilage repair (after microfracture) was scored histologically. Cartilage quality was analyzed macroscopically and histologically. Glycosaminoglycan content and release were measured by alcian blue assay, and the synthesis and release of newly formed glycosaminoglycans were measured by liquid scintillation analysis of the incorporation of 35SO4(2-) in tissue and medium.

RESULTS

The mean bone-implant contact (and standard error) was appropriate (14.6%+/-5.4%), and the amount of bone surrounding the implant was extensive (mean, 40.3%+/-4.0%). The healing of the microfracture-treated defects was extensive, although not complete (mean, 18.38+/-0.43 points of a maximum possible score of 24 points). The macroscopic cartilage evaluation did not show any significant differences between the treatments. On histologic evaluation, the cartilage of the medial tibial plateau articulating directly against the treated defects demonstrated significantly more degeneration in the microfracture-treated knees than in the implant-treated knees (p<0.05). This was in accordance with a significantly higher glycosaminoglycan content, higher synthetic activity, and decreased glycosaminoglycan release of the medial tibial plateau cartilage of the implant-treated knees (p<0.05 for all). On histological analysis, degeneration was also found in the cartilage of the lateral tibial plateau and condyle, but no significant difference was found between the treatments.

CONCLUSIONS

Both microfracture and the use of implants as a treatment for established localized cartilage defects in the medial femoral condyle caused considerable (p < 0.05) degeneration of the directly articulating cartilage as well as in more remote sites in the knee. However, in the medial tibial plateau, the metal implants caused less damage than the microfracture technique.

In vitro stage-specific chondrogenesis of mesenchymal stem cells committed to chondrocytes

OBJECTIVE

Osteoarthritis is characterized by an imbalance in cartilage homeostasis, which could potentially be corrected by mesenchymal stem cell (MSC)-based therapies. However, in vivo implantation of undifferentiated MSCs has led to unexpected results. This study was undertaken to establish a model for preconditioning of MSCs toward chondrogenesis as a more effective clinical tool for cartilage regeneration.

METHODS

A coculture preconditioning system was used to improve the chondrogenic potential of human MSCs and to study the detailed stages of chondrogenesis of MSCs, using a human MSC line, Kp-hMSC, in commitment cocultures with a human chondrocyte line, hPi (labeled with green fluorescent protein [GFP]). In addition, committed MSCs were seeded into a collagen scaffold and analyzed for their neocartilage-forming ability.

RESULTS

Coculture of hPi-GFP chondrocytes with Kp-hMSCs induced chondrogenesis, as indicated by the increased expression of chondrogenic genes and accumulation of chondrogenic matrix, but with no effect on osteogenic markers. The chondrogenic process of committed MSCs was initiated with highly activated chondrogenic adhesion molecules and stimulated cartilage developmental growth factors, including members of the transforming growth factor beta superfamily and their downstream regulators, the Smads, as well as endothelial growth factor, fibroblast growth factor, insulin-like growth factor, and vascular endothelial growth factor. Furthermore, committed Kp-hMSCs acquired neocartilage-forming potential within the collagen scaffold.

CONCLUSION

These findings help define the molecular markers of chondrogenesis and more accurately delineate the stages of chondrogenesis during chondrocytic differentiation of human MSCs. The results indicate that human MSCs committed to the chondroprogenitor stage of chondrocytic differentiation undergo detailed chondrogenic changes. This model of in vitro chondrogenesis of human MSCs represents an advance in cell-based transplantation for future clinical use.

Histological and biomechanical properties of regenerated articular cartilage using chondrogenic bone marrow stromal cells with a PLGA scaffold in vivo

The properties of regenerated cartilage using bone marrow-derived mesenchymal stem cells (MSCs) and poly lactic-co-glycolic acid (PLGA) scaffold composites pretreated with TGF-beta3 were investigated and compared to the non-TGF-beta3 treated MSCs/PLGA composites in a rabbit model. We prepared MSCs/PLGA scaffold composites and pretreated it with TGF-beta3 for 3 weeks prior to transplantation. Then, composites were transplanted to the osteochondral defect in the rabbit knee. After 12 weeks of transplantation, 10 of the 12 rabbits in which TGF-beta3 pretreated MSCs/PLGA scaffold composites were transplanted showed cartilaginous regeneration. In gross morphology, regenerated cartilage showed smooth, flush, and transparent features. In indentation test, this had about 80% of Young's modulus of normal articular cartilage. Histological examination demonstrated hyaline like cartilage structures with glycosaminoglycan and type II collagen expression. Histological scores were not statistically different to the normal articular cartilage. These results showed improvement of cartilage regeneration compared to the non-TGF-beta3 pretreated MSCs/PLGA scaffold composite transplanted group. Thus, we have successfully regenerated improved hyaline-like cartilage and determined the feasibility of treating damaged articular cartilage using MSCs/PLGA scaffold composite pretreated with TGF-beta3. Also, we suggest this treatment modality as another concept of cartilage tissue engineering.

The minipig model for experimental chondral and osteochondral defect repair in tissue engineering: retrospective analysis of 180 defects

Articular cartilage repair is still a challenge in orthopaedic surgery. Although many treatment options have been developed in the last decade, true regeneration of hyaline articular cartilage is yet to be accomplished. In vitro experiments are useful for evaluating cell-matrix interactions under controlled parameters. When introducing new treatment options into clinical routine, adequate animal models are capable of closing the gap between in vitro experiments and the clinical use in human beings. We developed an animal model in the Göttingen minipig (GMP) to evaluate the healing of osteochondral or full-thickness cartilage defects. The defects were located in the middle third of the medial portion of the patellofemoral joint at both distal femurs. Chondral defects were 6.3 mm, osteochondral defects either 5.4 or 6.3 mm in diameter and 8 or 10 mm deep. In both defects the endogenous repair response showed incomplete repair tissue formation up to 12 months postoperatively. Based on its limited capability for endogenous repair of chondral and osteochondral defects, the GMP is a useful model for critical assessment of new treatment strategies in articular cartilage tissue engineering.

Long term results after implantation of tissue engineered cartilage for the treatment of osteochondral lesions in a minipig model

In present study we determined the long term in vivo integration and histological modeling of an in vitro engineered cartilage construct. Tissue engineered autologous cartilagenous tissue was cultured on calcium phosphate cylinders and implanted into osteochondral defects into the femoral condyles in minipigs. Radiological follow-up was performed at 2, 8, 26 and 52 weeks, condyles were harvested 26 and 52 weeks post-implantation. Thickness of cultivated tissue (1.10 +/- 0.55 mm) was comparable to in situ cartilage and cells produced in vitro cartilage specific proteins. In vivo, 26 and 52 weeks post-implantation defects were resurfaced with hyaline-like tissue, the implants were well integrated with no gap at the interface between the engineered neocartilage and the adjacent articular cartilage. Synthesis of type II collagen was detected 26 and 52 weeks after implantation. The modified ICRS score increased from 26 to 52 weeks. Histomorphometric evaluation revealed a decrease in cellularity in tissue engineered cartilage from 2.2-fold of native cartilage after 26 weeks to 1.5-fold after 52 weeks. In conclusion, these findings demonstrate the integration and maturation of tissue engineered cartilage pellets attached on a bone substitute carrier implanted in osteochondral defects over a long time.

Mesenchymal stem cells in rheumatology: a regenerative approach to joint repair

The advent of biologics in rheumatology has considerably changed the evolution and prognosis of chronic inflammatory arthritis. The success of these new treatments has contributed to steering more attention to research focussed on repair and remodelling of joint tissues. Indeed, when the tissue damage is established, treatment options are very limited and the risk of progression towards joint destruction and failure remains high. Increasing evidence indicates that mesenchymal stem cells persist postnatally within joint tissues. It is postulated that they would function to safeguard joint homoeostasis and guarantee tissue remodelling and repair throughout life. Alterations in mesenchymal stem cell biology in arthritis have indeed been reported but a causal relationship has not been demonstrated, mainly because our current knowledge of mesenchymal stem cell niches and functions within the joint in health and disease is very limited. Nonetheless, mesenchymal stem cell technologies have attracted the attention of the biomedical research community as very promising tools to achieve the repair of joint tissues such as articular cartilage, subchondral bone, menisci and tendons. This review will outline stem-cell-mediated strategies for the repair of joint tissues, spanning from the use of expanded mesenchymal stem cell populations to therapeutic targeting of endogenous stem cells, resident in their native tissues, and related reparative signals in traumatic, degenerative and inflammatory joint disorders.

Enhanced early chondrogenesis in articular defects following arthroscopic mesenchymal stem cell implantation in an equine model

Mesenchymal stem cells (MSCs) provide an important source of pluripotent cells for musculoskeletal tissue repair. This study examined the impact of MSC implantation on cartilage healing characteristics in a large animal model. Twelve full-thickness 15-mm cartilage lesions in the femoropatellar articulations of six young mature horses were repaired by injection of a self-polymerizing autogenous fibrin vehicle containing mesenchymal stem cells, or autogenous fibrin alone in control joints. Arthroscopic second look and defect biopsy was obtained at 30 days, and all animals were euthanized 8 months after repair. Cartilage repair tissue and surrounding cartilage were assessed by histology, histochemistry, collagen type I and type II immunohistochemistry, collagen type II in situ hybridization, and matrix biochemical assays. Arthroscopic scores for MSC-implanted defects were significantly improved at the 30-day arthroscopic assessment. Biopsy showed MSC-implanted defects contained increased fibrous tissue with several defects containing predominantly type II collagen. Long-term assessment revealed repair tissue filled grafted and control lesions at 8 months, with no significant difference between stem cell-treated and control defects. Collagen type II and proteoglycan content in MSC-implanted and control defects were similar. Mesenchymal stem cell grafts improved the early healing response, but did not significantly enhance the long-term histologic appearance or biochemical composition of full-thickness cartilage lesions.

Preconditioning of mesenchymal stem cells with low-intensity ultrasound for cartilage formation in vivo

The purpose of this study was to evaluate the benefits of in vitro preconditioning of mesenchymal stem cells (MSCs) using low-intensity ultrasound (US) in the induction of chondrogenic differentiation of MSCs in vivo. After rabbit bone marrow-derived MSCs were seeded onto a polyglycolic acid (PGA) scaffold, the PGA-MSCs constructs were divided into 4 subgroups: untreated control, low-intensity US group, transforming growth factor-beta [TGF]-treated group and low-intensity US/TGF group. The chondrocyte-seeded PGA construct served as a positive control. For 1 week before implantation, the low-intensity US groups were subjected to ultrasound treatment for 20 min daily at an intensity of 200 mW/cm(2). The TGF groups were treated with 10 ng/mL TGF-beta1. The cells were then implanted into the nude mouse subcutaneously. Retrieved 1, 2, 4, and 6 weeks after implantation, each construct underwent gross examination, histology, biochemical assays, mechanical testing, and reverse transcriptase polymerase chain reaction (RT-PCR). Substantial size reduction and blood invasion were found much earlier in the groups that did not undergo low-intensity US than in those that did. Safranin O/Fast green staining revealed that the chondrogenic differentiation of MSCs was more widespread throughout the constructs in the low-intensity US groups. In the biochemical and mechanical analyses, the low-intensity US and low-intensity US/TGF groups were significantly better in forming hyaline cartilage-like tissue by 4 weeks than the non-low-intensity US groups. Presented by von Kossa staining, the development of osteogenic phenotypes was highly suppressed until 4 weeks in the low-intensity US groups, along with compressive strength comparable to the positive control. In the RT-PCR analysis before implantation, the messenger RNA levels of Sox-9, aggrecan, and tissue inhibitors of metalloproteinase-2 were higher in the low-intensity US groups, while those of type I and type X collagens and matrix metalloproteinase-13 were higher in the non-low-intensity US groups. Blood invasion into the constructs was also considerably hindered in the low-intensity US groups. These results strongly indicate that low-intensity US preconditioning in vitro could be an effective cue to upregulate chondrogenic differentiation of MSCs in vivo.

Regulation of adipose-derived adult stem cells differentiating into chondrocytes with the use of rhBMP-2

BACKGROUND

Adipose tissue has been demonstrated to contain a population of progenitor cells that can differentiate into bone and cartilage. Studies have suggested that adipose-derived adult stem (ADAS) cells can be induced to differentiate into chondrocytes by transforming growth factor-beta (TGF-beta). In this study, we examined whether bone morphogenetic protein-2 (BMP-2), as a member of the TGF-beta superfamily, could regulate ADAS cells to differentiate into a chondrolineage.

METHODS

ADAS cells were isolated and induced by rhBMP-2. These cells were cultured in pellets for 2 weeks, and the chondrogenic phenotype was observed in vitro and in vivo. ADAS cells cultured without BMP-2 were used as controls.

RESULTS

After 2 weeks of culture, the differentiated ADAS cells reacted positively to Alcian blue and collagen II, and the content of collagen II protein was obviously up-regulated at day 14. Glycosaminoglycan (GAG) content gradually increased from day 2 to day 14 (P < 0.05). However, H&E staining and collagen II expression were weak, and there was a little collagen II protein and GAG detected in the control group. Additionally, the pellets of ADAS cells induced by rhBMP-2 were transplanted into BALB/C nude mice and formed cartilage lacuna at week 8 in vivo.

DISCUSSION

These data demonstrate that rhBMP-2 induce ADAS cells to differentiate into chondrocytes in vitro and in vivo. This is useful for basic and clinical studies aimed at repairing cartilage damage. But in a control group, ADAS cells tended towards differentiation into chondrocytes, which was affected by ITS. We will be exploring the mechanism further.