Chondrogenesis of human mesenchymal stem cells by local transforming growth factor-beta delivery in a biphasic resorbable carrier

Microfracture- and Xeno-Matrix-Induced Chondrogenesis for Treatment of Focal Traumatic Cartilage Defects of the Knee: Age-Based Mid-Term Results

The aim of this study was to investigate clinical and instrumental outcomes of the autologous matrix-induced chondrogenesis (AMIC) technique for the treatment of isolated traumatic condyle and femoropatellar cartilage lesions. A total of 25 patients (12 males, 13 females, mean age 47.3 years) treated between 2018 and 2021 were retrospectively reviewed and subdivided into two groups based on age (Group A, age < 45 years; Group B, age > 45 years). A clinical evaluation was performed using the International Knee Documentation Committee (IKDC), Lysholm score and Visual Analogue Score (VAS). Cartilage regeneration was evaluated via magnetic resonance (1.5 Tesla) and classified according to a Magnetic resonance Observation of CArtilage Repair Tissue (MOCART) scoring system. At a minimum follow-up of 2 years, Group A patients obtained greater instrumental results in comparison to group B: in fact, the MOCART score was statistically significantly correlated with IKDC (r = 0.223) (p < 0.001) exclusively in group A. Nevertheless, a significant improvement in clinical functionality was shown in Group B (p < 0.001), demonstrating that this technique is safe, reproducible and capable of offering satisfactory clinical results regardless of age.

Advances in Biomaterial-Mediated Gene Therapy for Articular Cartilage Repair

Articular cartilage defects caused by various reasons are relatively common in clinical practice, but the lack of efficient therapeutic methods remains a substantial challenge due to limitations in the chondrocytes’ repair abilities. In the search for scientific cartilage repair methods, gene therapy appears to be more effective and promising, especially with acellular biomaterial-assisted procedures. Biomaterial-mediated gene therapy has mainly been divided into non-viral vector and viral vector strategies, where the controlled delivery of gene vectors is contained using biocompatible materials. This review will introduce the common clinical methods of cartilage repair used, the strategies of gene therapy for cartilage injuries, and the latest progress.

Is there clinical evidence to support autologous matrix-induced chondrogenesis (AMIC) for chondral defects in the talus? A systematic review and meta-analysis

BACKGROUND

The aim of this study is to systematically review the literature on clinical outcomes of patients who have undergone autologous matrix-induced chondrogenesis (AMIC) for treatment of osteochondral lesions of the talus (OCL) and compare the studies' outcomes.

METHODS

Pubmed and Embase were searched in January 2020 for articles concerning OCL surgery. Studies were included if they had a minimum 1-year follow-up and the primary measures were functional outcomes. The meta-analysis compared the Visual Analogic Score (VAS), the American Orthopedic Foot and Ankle Score (AOFAS), and the Foot Function Index (FFI) between baseline and follow-up of 1-2years, and 3-5years. A random effects model was used to evaluate outcome changes.

RESULTS

The search returned 15 studies, with a total of 492 patients. The VAS improved 4.45 and 4.6 points from baseline to the 1-2year and 3-5yearfollow-up, respectively (p<0.001). AOFAS improved 31.59 and 32.47 points from baseline to the 1-2year and 3-5yearfollow-up, respectively (p<0.001). The FFI showed a significant improvement of 30.93 points from baseline to year 3-5 (p<0.001). A total of 6 patients with revision surgeries have been reported within the follow up period. It was not possible to correlate clinical features like lesion size, surgical approach, and bone marrow stimulation technique to the reported outcome.

CONCLUSION

Surgical treatment of OCL via the AMIC procedure provided significant improvement in the functional outcome and pain scores when compared to the pre-operative values. Improvements were observed up to 5years post-operatively.

Different types of cartilage neotissue fabricated from collagen hydrogels and mesenchymal stromal cells via SOX9, TGFB1 or BMP2 gene transfer

Objective

As native cartilage consists of different phenotypical zones, this study aims to fabricate different types of neocartilage constructs from collagen hydrogels and human mesenchymal stromal cells (MSCs) genetically modified to express different chondrogenic factors.

Design

Human MSCs derived from bone-marrow of osteoarthritis (OA) hips were genetically modified using adenoviral vectors encoding sex-determining region Y-type high-mobility-group-box (SOX) 9, transforming growth factor beta (TGFB) 1 or bone morphogenetic protein (BMP) 2 cDNA, placed in type I collagen hydrogels and maintained in serum-free chondrogenic media for three weeks. Control constructs contained unmodified MSCs or MSCs expressing GFP. The respective constructs were analyzed histologically, immunohistochemically, biochemically, and by qRT-PCR for chondrogenesis and hypertrophy.

Results

Chondrogenesis in MSCs was consistently and strongly induced in collagen I hydrogels by the transgenes SOX9, TGFB1 and BMP2 as evidenced by positive staining for proteoglycans, chondroitin-4-sulfate (CS4) and collagen (COL) type II, increased levels of glycosaminoglycan (GAG) synthesis, and expression of mRNAs associated with chondrogenesis. The control groups were entirely non-chondrogenic. The levels of hypertrophy, as judged by expression of alkaline phosphatase (ALP) and COL X on both the protein and mRNA levels revealed different stages of hypertrophy within the chondrogenic groups (BMP2>TGFB1>SOX9).

Conclusions

Different types of neocartilage with varying levels of hypertrophy could be generated from human MSCs in collagen hydrogels by transfer of genes encoding the chondrogenic factors SOX9, TGFB1 and BMP2. This technology may be harnessed for regeneration of specific zones of native cartilage upon damage.

Fine-Tunable and Injectable 3D Hydrogel for On-Demand Stem Cell Niche

Stem-cell-based tissue engineering requires increased stem cell retention, viability, and control of differentiation. The use of biocompatible scaffolds encapsulating stem cells typically addresses the first two problems. To achieve control of stem cell fate, fine-tuned biocompatible scaffolds with bioactive molecules are necessary. However, given that the fine-tuning of stem cell scaffolds is associated with UV irradiation and in situ scaffold gelation, this process is in conflict with injectability. Herein, a fine-tunable and injectable 3D hydrogel system is developed with the use of thermosensitive poly(organophosphazene) bearing β-cyclodextrin (β-CD PPZ) and two types of adamantane-peptides (Ad-peptides) that are associated with mesenchymal stem cell (MSC) differentiation and that serve as stoichiometrically controlled pendants for fine-tuning. Given that complexation of hosts and guests subject to strict stoichiometric control is achieved with simple mixing, these fabricated hydrogels exhibit well-aligned, fine-tuning responses, even in living animals. Injection of MSCs in fine-tuned hydrogels also results in various chondrogenic differentiation levels at three weeks postinjection. This is attributed to the differential controls of Ad-peptides, if MSC preconditioning is excluded. Eventually, the fine-tunable and injectable 3D hydrogel could be applied as platform technology by simply switching the types of peptides bearing adamantane and their stoichiometry.

Functional Medium-Term Results After Autologous Matrix-Induced Chondrogenesis for Osteochondral Lesions of the Talus: A 5-Year Prospective Cohort Study

Autologous matrix-induced chondrogenesis (AMIC) has gained popularity in the treatment of osteochondral lesions of the talus. Previous studies have presented promising short-term results for AMIC talar osteochondral lesion repair, a 1-step technique using a collagen type I/III bilayer matrix. The aim of the present study was to investigate the mid-term effects. The 5-year results of a prospective cohort study are presented. All patients underwent an open AMIC procedure for a talar osteochondral lesion. Data analysis included general demographic data, preoperative magnetic resonance imaging findings, intraoperative details, and German version of the Foot Function Index (FFI-D) scores preoperatively and at 1 and 5 years after surgery. The primary outcome variable was the longitudinal effect of the procedure, and the influence of various variables on the outcome was tested. Of 47 consecutive patients, 21 (45%) were included. Of the 21 patients, 8 were female (38%) and 13 were male (62%), with a mean age of 37 ± 15 (range 15 to 62) years and a body mass index of 26 ± 5 (range 20 to 38) kg/m². The defect size was 1.4 ± 0.9 (range 0.2 to 4.0) cm². The FFI-D decreased significantly from preoperatively to 1 year postoperatively (56 ± 18 versus 33 ± 25; p = .003), with a further, nonsignificant decrease between the 1- and 5-year follow-up examination (33 ± 25 versus 24 ± 21; p = .457). Similar results were found for the FFI-D subscales of function and pain. The body mass index and lesion size showed a positive correlation with the preoperative FFI-D overall and subscale scores. These results showed a significant improvement in pain and function after the AMIC procedure, with a significant return to sports by the 5-year follow-up point. The greatest improvement overall was seen within the first year; however, further clinical satisfaction among the patients was noticeable after 5 years.

3D bioprinting: improving in vitro models of metastasis with heterogeneous tumor microenvironments

Even with many advances in treatment over the past decades, cancer still remains a leading cause of death worldwide. Despite the recognized relationship between metastasis and increased mortality rate, surprisingly little is known about the exact mechanism of metastatic progression. Currently available in vitro models cannot replicate the three-dimensionality and heterogeneity of the tumor microenvironment sufficiently to recapitulate many of the known characteristics of tumors in vivo Our understanding of metastatic progression would thus be boosted by the development of in vitro models that could more completely capture the salient features of cancer biology. Bioengineering groups have been working for over two decades to create in vitro microenvironments for application in regenerative medicine and tissue engineering. Over this time, advances in 3D printing technology and biomaterials research have jointly led to the creation of 3D bioprinting, which has improved our ability to develop in vitro models with complexity approaching that of the in vivo tumor microenvironment. In this Review, we give an overview of 3D bioprinting methods developed for tissue engineering, which can be directly applied to constructing in vitro models of heterogeneous tumor microenvironments. We discuss considerations and limitations associated with 3D printing and highlight how these advances could be harnessed to better model metastasis and potentially guide the development of anti-cancer strategies.

Stem cells display a donor dependent response to escalating levels of growth factor release from extracellular matrix-derived scaffolds

Numerous growth factor delivery systems have been developed for tissue engineering. However, little is known about how the dose of a specific protein will influence tissue regeneration, or how different patients will respond to altered levels of growth factor presentation. The objective of the present study was to assess stem cell chondrogenesis within extracellular-matrix (ECM)-derived scaffolds loaded with escalating levels of transforming growth factor (TGF)-β3. It was also sought to determine if stem cells display a donor-dependent response to different doses of TGF-β3, from low (5 ng) to high (200 ng), released from such scaffolds. It was found that ECM-derived scaffolds possess the capacity to bind and release increasing amounts of TGF-β3, with between 60% and 75% of this growth factor released into the media over the first 12 days of culture. After seeding these scaffolds with human infrapatellar fat pad-derived stem cells (FPSCs), it was found that cartilage-specific ECM accumulation was greatest for the higher levels of growth factor loading. Importantly, soak-loading cartilage ECM-derived scaffolds with high levels of TGF-β3 always resulted in at least comparable levels of chondrogenesis to controls where this growth factor was continuously added to the culture media. Similar results were observed for FPSCs from all donors, although the absolute level of secreted matrix did vary from donor to donor. Therefore, while no single growth factor release profile will be optimal for all patients, the results of this study suggest that the combination of a highly porous cartilage ECM-derived scaffold coupled with appropriate levels of TGF-β3 can consistently drive chondrogenesis of adult stem cells. Copyright © 2016 John Wiley & Sons, Ltd.

In vitro culture of hFOB1.19 osteoblast cells on TGF-β1-SF-CS three-dimensional scaffolds

The aim of the present study was to examine the biocompatibility of transforming growth factor-β1-silk fibroin-chitosan (TGF-β1-SF-CS) scaffolds. In order to provide an ideal scaffold for use in bone tissue engineering, TGF-β1 was introduced into the SF-CS scaffold in order to reconstruct a three dimensional scaffold, following which hFOB1.19 osteoblast cells were seeded onto TGF-β1-SF-CS and SF-CS scaffolds. On the TGF-β1-SF-CS and SF-CS scaffolds, the cell adhesion rate increased in a time-dependent manner. Scanning electron microscopy revealed that the cells grew actively and exhibited normal morphological features with multiple fissions, and granular and filamentous substrates were observed surrounding the cells. In addition, the cell microfilaments were closely connected with the scaffolds. The cells exhibited attached growth on the surfaces of the scaffolds, however, the growth also extended into the scaffolds. Cell Counting Kit-8 and ALP analyses revealed that TGF-β1 significantly promoted the growth and proliferation of the hFOB1.19 osteoblast cells in the SF-CS scaffolds, and the enhancement of osteoblast cell proliferation and activity by TGF-β1 occurred in a time-dependent manner. The TGF-β1-SF-CS composite material may offer potential as an ideal scaffold material for bone tissue engineering.

Tissue engineering of the temporomandibular joint disc: current status and future trends

INTRODUCTION

Temporomandibular joint disorders are extremely prevalent and there is no ideal treatment clinically for the moment. For severe cases, a discectomy often need to be performed, which will further result in the development of osteoarthritis. In the past thirty years, tissue engineering has provided a promising approach for the effective remedy of severe TMJ disease through the creation of viable, effective, and biological functional implants.

METHODS

Although TMJ disc tissue engineering is still in early stage, unremitting efforts and some achievements have been made over the past decades. In this review, a comprehensive summary of the available literature on the progress and status in tissue engineering of the TMJ disc regarding cell sources, scaffolds, biochemical and biomechanical stimuli, and other prospects relative to this field is provided.

RESULTS AND CONCLUSIONS

Even though research studies in this field are too few compared to other fibrocartilage (e.g., knee meniscus) and numerous, difficult tasks still exist, we believe that our ultimate goal of regenerating a biological implant whose histological, biochemical, and biomechanical properties parallel native TMJ discs for clinical therapy will be achieved in the near future.

Reconstruction of focal cartilage defects in the talus with miniarthrotomy and collagen matrix

SURGICAL PRINCIPAL AND OBJECTIVE

Treatment of focal cartilage defects (traumatic or osteochondrosis dissecans) of the talus using a collagen matrix. The goal is to stabilize the superclot formed after microfracturing to accommodate cartilage repair. The procedure can be carried out via miniarthrotomy, without medial malleolus osteotomy.

INDICATIONS

International Cartilage Repair Society (ICRS) grade III and IV focal cartilage defects of the talus > 1.5 cm(2).

CONTRAINDICATIONS

Generalized osteoarthritis, inflammatory joint disease, gout, neuroarthropathy.

SURGICAL TECHNIQUE

Miniarthrotomy to open the ankle joint. Debridement of unstable cartilage and necrotic bone, curettage of cysts. Filling of the bone defects with autologous cancellous bone. Sealing of reconstructed bone with fibrin glue and attachment of a collagen matrix shaped to precisely fit the defect.

POSTOPERATIVE REGIMEN

Immobilization for 48 h. Partial weight bearing of 10 kg for 6 weeks, with continuous passive motion. Increasing weight bearing from 7 weeks onwards.

RESULTS

Follow-up of at least 30 months in 14 patients showed improvement in the Score of the American Orthopedic Foot and Ankle Society (AOFAS) from 50 to 89 points, with equal mobility on both sides of the upper ankle joint.

Enhanced microfracture techniques in cartilage knee surgery: Fact or fiction?

The limited intrinsic healing potential of human articular cartilage is a well-known problem in orthopedic surgery. Thus a variety of surgical techniques have been developed to reduce joint pain, improve joint function and delay the onset of osteoarthritis. Microfractures as a bone marrow stimulation technique present the most common applied articular cartilage repair procedure today. Unfortunately the deficiencies of fibrocartilaginous repair tissue inevitably lead to breakdown under normal joint loading and clinical results deteriorate with time. To overcome the shortcomings of microfracture, an enhanced microfracture technique was developed with an additional collagen I/III membrane (Autologous, Matrix-Induced Chondrogenesis, AMIC^®). This article reviews the pre-clinical rationale of microfractures and AMIC^®, presents clinical studies and shows the advantages and disadvantages of these widely used techniques. PubMed and the Cochrane database were searched to identify relevant studies. We used a comprehensive search strategy with no date or language restrictions to locate studies that examined the AMIC^® technique and microfracture. Search keywords included cartilage, microfracture, AMIC^®, knee, Chondro-Gide^®. Besides this, we included our own experiences and study authors were contacted if more and non published data were needed. Both cartilage repair techniques represent an effective and safe method of treating full-thickness chondral defects of the knee in selected cases. While results after microfracture deteriorate with time, mid-term results after AMIC^® seem to be enduring. Randomized studies with long-term follow-up are needed whether the grafted area will maintain functional improvement and structural integrity over time.

Initial boost release of transforming growth factor-β3 and chondrogenesis by freeze-dried bioactive polymer scaffolds

In cartilage regeneration, bio-activated implants are used in stem and progenitor cell-based microfracture cartilage repair procedures. Our aim was to analyze the chondrogenic potential of freeze-dried resorbable polymer-based polyglycolic acid (PGA) scaffolds bio-activated with transforming growth factor-β3 (TGFB3) on human subchondral mesenchymal progenitor cells known from microfracture. Progenitor cells derived from femur heads were cultured in the presence of freeze-dried TGFB3 in high-density pellet culture and in freeze-dried TGFB3-PGA scaffolds for chondrogenic differentiation. Progenitor cell cultures in PGA scaffolds as well as pellet cultures with and without continuous application of TGFB3 served as controls. Release studies showed that freeze-dried TGFB3-PGA scaffolds facilitate a rapid, initial boost-like release of 71.5% of TGFB3 in the first 10 h. Gene expression analysis and histology showed induction of typical chondrogenic markers like type II collagen and formation of cartilaginous tissue in TGFB3-PGA scaffolds seeded with subchondral progenitor cells and in pellet cultures stimulated with freeze-dried TGFB3. Chondrogenic differentiation in freeze-dried TGFB3-PGA scaffolds was comparable to cultures receiving TGFB3 continuously, while non-stimulated controls did not show chondrogenesis during prolonged culture for 14 days. These results suggest that bio-activated, freeze-dried TGFB3-PGA scaffolds have chondrogenic potential and are a promising tool for stem cell-mediated cartilage regeneration.

Collagen scaffold for cartilage tissue engineering: the benefit of fibrin glue and the proper culture time in an infant cartilage model

This study (i) developed a scaffold made of collagen I designed for hosting the autologous chondrocytes, (ii) focused on the optimization of chondrocytes seeding by the addition of the fibrin glue, and (iii) investigated the culture time for the ideal scaffold maturation in vitro. In the first part of the study, fresh chondrocytes were isolated from infant swine articular cartilage, and immediately seeded onto the collagen sponges either in medium or in fibrinogen in order to show the contribute of fibrin glue in cell seeding and survival into the scaffold. In the second part of the study, chondrocytes were first expanded in vitro and then resuspended in fibrinogen, seeded in collagen sponges, and cultured for 1, 3, and 5 weeks in order to identify the optimal time for the rescue of cell phenotype and for the scaffold maturation into a tissue with chondral properties. The histological and immunohistochemical data from the first part of the study (study with primary chondrocytes) demonstrated that the presence of fibrin glue ameliorated cell distribution and survival into the chondral composites. The second part of this work (study with dedifferentiated chondrocytes) showed that the prolongation of the culture to 3 weeks promoted a significant restoration of the cell phenotype, resulting in a composite with proper morphological features, biochemical composition, and mechanical integrity. In conclusion, this study developed a collagenic-fibrin glue scaffold that was able to support chondrocyte survival and synthetic activity in a static culture; in particular, this model was able to turn the engineered samples into a tissue with chondral-like properties when cultured in vitro for at least 3 weeks.

Hypoxia enhances chondrogenic differentiation of human adipose tissue-derived stromal cells in scaffold-free and scaffold systems

Human adipose-derived stromal cells (hASCs) possess the potential for chondrogenic differentiation. Recent studies imply that this differentiation process may be enhanced by culturing the cells in low oxygen tension in combination with three-dimensional (3D) scaffolds. We report the evaluation of the chondrogenic potential of hASC pellets in 5 and 21% O2 and as cell-scaffold constructs using a collagen I/III scaffold with chemical induction using TGF-β3. hASCs from four human donors were cultured both in a micromass pellet system and in 3D collagen I/III scaffolds in either 5 or 21% O2. Chondrogenesis was evaluated by quantitative gene expression analysis of aggrecan, SOX9, collagen I, II and X and histological evaluation with H&E and toluidine blue staining. Induced pellets cultured in 5% O2 showed increased peripheral cellularity and matrix deposition compared with 21% O2. Induced pellets cultured in 5% O2 had increased control-adjusted gene expression of aggrecan, SOX9 and collagen I and decreased collagen X compared with 21% O2 cultures. Induced pellets had higher gene expression of aggrecan, SOX9, collagen I, II and X and increased ratios of collagen II/I and collagen II/X compared with controls. As for pellets, scaffold cultures showed cellularity and matrix deposition organized in a zonal manner as a function of the oxygen tension, with a cartilage-like morphology and matrix deposition peripherally in the 5% O2 group and a more centrally located matrix in the 21% O2 group. There were no differences in histology and gene expressions between pellet and scaffold cultures. Five percent O2 in combination with chondrogenic culture medium stimulated chondrogenic differentiation of hASCs in vitro. We observed similar patterns of differentiation and matrix disposition in pellet and scaffold cultures.

Transforming growth factor Beta-releasing scaffolds for cartilage tissue engineering

The maintenance of a critical threshold concentration of transforming growth factor beta (TGF-β) for a given period of time is crucial for the onset and maintenance of chondrogenesis. Thus, the development of scaffolds that provide temporal and/or spatial control of TGF-β bioavailability has appeal as a mechanism to induce the chondrogenesis of stem cells in vitro and in vivo for articular cartilage repair. In the past decade, many types of scaffolds have been designed to advance this goal: hydrogels based on polysaccharides, hyaluronic acid, and alginate; protein-based hydrogels such as fibrin, gelatin, and collagens; biopolymeric gels and synthetic polymers; and solid and hybrid composite (hydrogel/solid) scaffolds. In this study, we review the progress in developing strategies to deliver TGF-β from scaffolds with the aim of enhancing chondrogenesis. In the future, such scaffolds could prove critical for tissue engineering cartilage, both in vitro and in vivo.

Different culture media affect growth characteristics, surface marker distribution and chondrogenic differentiation of human bone marrow-derived mesenchymal stromal cells

Background

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) play an important role in modern tissue engineering, while distinct variations of culture media compositions and supplements have been reported. Because MSCs are heterogeneous regarding their regenerative potential and their surface markers, these parameters were compared in four widely used culture media compositions.

Methods

MSCs were isolated from bone marrow and expanded in four established cell culture media. MSC yield/1000 MNCs, passage time and growth index were observed. In P4, typical MSC surface markers were analysed by fluorescence cytometry. Additionally, chondrogenic, adipogenic and osteogenic differentiation potential were evaluated.

Results

Growth index and P0 cell yield varied importantly between the media. The different expansion media had a significant influence on the expression of CD10, CD90, CD105, CD140b CD146 and STRO-1. While no significant differences were observed regarding osteogenic and adipogenic differentiation, chondrogenic differentiation was superior in medium A as reflected by GAG/DNA content.

Conclusions

The choice of expansion medium can have a significant influence on growth, differentiation potential and surface marker expression of mesenchymal stromal cells, which is of fundamental importance for tissue engineering procedures.

Comparative analysis of reference gene stability in human mesenchymal stromal cells during osteogenic differentiation

Mesenchymal stromal cells (MSCs) are one of the most frequently used cell sources for tissue engineering strategies. Cultivation of osteogenic MSCs is a prerequisite for cell-based concepts that aim at bone regeneration. Quantitative real time reverse transcription polymerase chain reaction (qRT-PCR) analysis is a commonly used method for the examination of mRNA expression levels. However, data on suitable reference genes for osteogenically cultivated MSCs is scarce. Hence, the aim of the study was to compare the regulation of different potential reference genes in osteogenically stimulated MSCs. Human MSCs were isolated from bone marrow aspirates of N = 6 hematologically healthy individuals, expanded by polystyrene-adherence, and maintained with and without osteogenic supplements for 14 days. Cellular proliferation and osteogenic differentiation were assessed by total DNA quantification, cell-specific alkaline phosphatase (ALP) activity and by qualitative staining for ALP and alizarin red, respectively. mRNA expression levels of N = 32 potential reference genes were quantified using the human Endogenous Control TaqMan® assays. mRNA expression stability was calculated using geNorm. The combined use of the most stable reference genes and DNA-damage-inducible alpha, Pumilio homolog 1, and large ribosomal protein P0 significantly improved gene expression accuracy as compared to the use of the commonly used reference genes beta actin and glyceraldehyde-3-phosphate dehydrogenase during qRT-PCR-based target gene expression analysis of osteogenically stimulated MSCs.

Enhanced reconstruction of long bone architecture by a growth factor mutant combining positive features of GDF-5 and BMP-2

Non healing bone defects remain a worldwide health problem and still only few osteoinductive growth factors are available for clinical use in bone regeneration. By introducing BMP-2 residues into growth and differentiation factor (GDF)-5 we recently produced a mutant GDF-5 protein BB-1 which enhanced heterotopic bone formation in mice. Designed to combine positive features of GDF-5 and BMP-2, we suspected that this new growth factor variant may improve long bone healing compared to the parent molecules and intended to unravel functional mechanisms behind its action. BB-1 acquired an increased binding affinity to the BMP-IA receptor, mediated enhanced osteogenic induction of human mesenchymal stem cells versus GDF-5 and higher VEGF secretion than BMP-2 in vitro. Rabbit radius defects treated with a BB-1-coated collagen carrier healed earlier and with increased bone volume compared to BMP-2 and GDF-5 according to in vivo micro-CT follow-up. While BMP-2 callus often remained spongy, BB-1 supported earlier corticalis and marrow cavity formation, showing no pseudojoint persistence like with GDF-5. Thus, by combining positive angiogenic and osteogenic features of GDF-5 and BMP-2, only BB-1 restored a natural bone architecture within 12 weeks, rendering this promising growth factor variant especially promising for long bone regeneration.

A Randomized, Controlled Trial Comparing Autologous Matrix-Induced Chondrogenesis (AMIC®) to Microfracture: Analysis of 1- and 2-Year Follow-Up Data of 2 Centers

Microfracture (MFx) is currently the recommended option for the treatment of small cartilage defects but is not regarded as suitable for the treatment of defects larger than 2.5 cm². To extent its applicability to medium-sized defects MFx has been combined with a collagen type I/III matrix (Chondro-Gide^®). This technique is called Autologous Matrix-Induced Chondrogenesis (AMIC^®) and meanwhile a clinically established treatment option for localized full-thickness small- to medium-sized cartilage defects. Despite its more spreading clinical use, clinical data published so far are limited to mainly case report series.

In this study, we report the first results of a randomized, controlled trial assessing the efficacy and safety of AMIC^® versus MFx. Patients enrolled in 2 centers were included in this analysis. 38 patients (aged 21-50 years, mean defect size 3.4 cm²) were randomized and treated either with MFx, with sutured AMIC^® or glued AMIC^®. Clinical outcomes (modified Cincinnati and ICRS score) could be assessed in 30 patients at 1-year and 27 patients at 2-years post-operation. Improvements in both scores were seen at 1-and 2-years post-operation, irrespective of the technique used. MRI assessment revealed a satisfactory and homogenous defect filling in the majority of patients. No treatment-related adverse events were reported.

This interim analysis confirms the mid-term results for AMIC^® reported in literature. It demonstrates clearly that clinical outcomes at 1-year post-operation are maintained at 2-years. Therefore we consider enhancing MFx with Chondro-Gide^® is a valid and safe cartilage repair option for small- to medium-sized cartilage defects of the knee.

Advanced Strategies for Articular Cartilage Defect Repair

Articular cartilage is a unique tissue owing to its ability to withstand repetitive compressive stress throughout an individual's lifetime. However, its major limitation is the inability to heal even the most minor injuries. There still remains an inherent lack of strategies that stimulate hyaline-like articular cartilage growth with appropriate functional properties. Recent scientific advances in tissue engineering have made significant steps towards development of constructs for articular cartilage repair. In particular, research has shown the potential of biomaterial physico-chemical properties significantly influencing the proliferation, differentiation and matrix deposition by progenitor cells. Accordingly, this highlights the potential of using such properties to direct the lineage towards which such cells follow. Moreover, the use of soluble growth factors to enhance the bioactivity and regenerative capacity of biomaterials has recently been adopted by researchers in the field of tissue engineering. In addition, gene therapy is a growing area that has found noteworthy use in tissue engineering partly due to the potential to overcome some drawbacks associated with current growth factor delivery systems. In this context, such advanced strategies in biomaterial science, cell-based and growth factor-based therapies that have been employed in the restoration and repair of damaged articular cartilage will be the focus of this review article.

Controlled release strategies for bone, cartilage, and osteochondral engineering--Part II: challenges on the evolution from single to multiple bioactive factor delivery

The development of controlled release systems for the regeneration of bone, cartilage, and osteochondral interface is one of the hot topics in the field of tissue engineering and regenerative medicine. However, the majority of the developed systems consider only the release of a single growth factor, which is a limiting step for the success of the therapy. More recent studies have been focused on the design and tailoring of appropriate combinations of bioactive factors to match the desired goals regarding tissue regeneration. In fact, considering the complexity of extracellular matrix and the diversity of growth factors and cytokines involved in each biological response, it is expected that an appropriate combination of bioactive factors could lead to more successful outcomes in tissue regeneration. In this review, the evolution on the development of dual and multiple bioactive factor release systems for bone, cartilage, and osteochondral interface is overviewed, specifically the relevance of parameters such as dosage and spatiotemporal distribution of bioactive factors. A comprehensive collection of studies focused on the delivery of bioactive factors is also presented while highlighting the increasing impact of platelet-rich plasma as an autologous source of multiple growth factors.

Interplay between local versus soluble transforming growth factor-beta and fibrin scaffolds: role of cells and impact on human mesenchymal stem cell chondrogenesis

Structural extracellular matrix molecules gain increasing attention as scaffolds for cartilage tissue engineering owing to their natural role as a growth factor repository. We recently observed that a collagen-type I/III (Col-I/III) matrix, human recombinant transforming growth factor-beta (TGF-β) protein, and fibrin hydrogel (FG) combined to a biphasic construct provided sufficient long-term TGF-β support to drive in vitro chondrogenesis of human mesenchymal stem cells (hMSC). Here we ask whether FG and Col-I/III can both retain TGF-β, describe the influence of cell seeding on TGF-β release, and compare the molecular path of hMSC chondrogenic differentiation under soluble versus local TGF-β supply. Release of growth factor from scaffolds augmented with increasing amounts of TGF-β was analyzed over 7 days and chondrogenesis was assessed over 42 days. Low TGF-β release rates from Col-I/III as opposed to higher release from FG indicated that both molecules retained TGF-β, with Col-I/III being the superior storage component. Cell seeding enhanced TGF-β retention in FG by about threefold and almost stopped release beyond 24 h. TGF-β remained bioactive and supported MSC chondrogenesis without impairing the amount of proteoglycan and collagen-type II deposition per cell and per construct compared to standard scaffold-free MSC pellets supplied with soluble TGF-β. Local TGF-β, however, mediated lower cell content, less collagen-type X relative to collagen-type II deposition and no matrix metalloproteinase-13 up-regulation. In conclusion, cells quickly halted release of local TGF-β from FG, turning FG and Col-I/III into attractive TGF-β repositories capable to drive full hMSC chondrogenesis, but via a modulated differentiation pathway. Since only part of the changes was reproduced by transient soluble TGF-β supply, release kinetics alone could not explain the molecular differences, suggesting that local TGF-β acts distinct from its soluble counterpart.

Revision of failed osteochondral autologous transplantation procedure for chronic talus osteochondral lesion with iliac crest graft and autologous matrix-induced chondrogenesis: a case report

This article describes a novel technique for treatment of recurrent large osteochondral lesions of the talus using autologous matrix-induced chondrogenesis with a collagen I/III matrix.

Treatment of knee cartilage defect in 2010

Treatment of knee cartilage defect, a true challenge, should not only reconstruct hyaline cartilage on a long-term basis, but also be able to prevent osteoarthritis. Osteochondral knee lesions occur in either traumatic lesions or in osteochondritis dissecans (OCD). These lesions can involve all the articular surfaces of the knee in its three compartments. In principle, this review article covers symptomatic ICRS grade C or D lesions, depth III and IV, excluding management of superficial lesions, asymptomatic lesions that are often discovered unexpectedly, and kissing lesions, which arise prior to or during osteoarthritis. For clarity sake, the international classifications used are reviewed, for both functional assessment (ICRS and functional IKDC for osteochondral fractures, Hughston for osteochondritis) and morphological lesion evaluations (the ICRS macroscopic evaluation for fractures, the Bedouelle or SOFCOT for osteochondritis, and MOCART for MRI). The therapeutic armamentarium to treat these lesions is vast, but accessibility varies greatly depending on the country and the legislation in effect. Many comparative studies have been conducted, but they are rarely of high scientific quality; the center effect is nearly constant because patients are often referred to certain centers for an expert opinion. The indications defined herein use algorithms that take into account the size of the cartilage defect and the patient's functional needs for cases of fracture and the vitality, stability, and size of the fragment for cases of osteochondritis dissecans. Fractures measuring less than 2 cm(2) are treated with either microfracturing or mosaic osteochondral grafting, between 2 and 4 cm(2) with microfractures covered with a membrane or a culture of second- or third-generation chondrocytes, and beyond this size, giant lesions are subject to an exceptional allografting procedure, harvesting from the posterior condyle, or chondrocyte culture on a 3D matrix to restore volume. Cases of stable osteochondritis dissecans with closed articular cartilage can be simply monitored or treated with perforation in cases of questionable vitality. Cases of open joint cartilage are treated with a PLUS fixation if their vitality is preserved; if not, they are treated comparably to osteochondral fractures, with the type of filling depending on the defect size.

Osteochondral interface regeneration of the rabbit knee with macroscopic gradients of bioactive signals

To date, most interfacial tissue engineering approaches have used stratified designs, in which there are two or more discrete layers comprising the interface. Continuously graded interfacial designs, where there is no discrete transition from one tissue type to another, are gaining attention as an alternative to stratified designs. Given that osteochondral regeneration holds the potential to enhance cartilage regeneration by leveraging the healing capacity of the underlying bone, we endeavored to introduce a continuously-graded approach to osteochondral regeneration. The purpose of this study was thus to evaluate the performance of a novel gradient-based scaffolding approach to regenerate osteochondral defects in the New Zealand White rabbit femoral condyle. Bioactive plugs were constructed from poly(D,L-lactic-co-glycolic acid) microspheres with a continuous gradient transition between cartilage-promoting and bone-promoting growth factors. At 6 and 12 weeks of healing, results suggested that the implants provided support for the neo-synthesized tissue, and the gradient in bioactive signaling may have been beneficial for bone and cartilage regeneration compared to the blank control implant, as evidenced by histology. In addition, the effects of preseeding gradient scaffolds with umbilical cord mesenchymal stromal cells (UCMSCs) from the Wharton's jelly of New Zealand White rabbits were evaluated. Results indicated that there may be regenerative benefits to prelocalizing UCMSCs within scaffold interiors. The inclusion of bioactive factors in a gradient-based scaffolding design is a promising new treatment strategy for defect repair in the femoral condyle.

The use of growth factors and mesenchymal stem cells in orthopaedics

Stem cell therapy is an exciting and upcoming branch of tissue engineering with application in the field of orthopaedics. The most commonly used type of stem cells, mesenchymal stem cells (MSCs), can be easily isolated from bone marrow or synovium and cultured in vitro. Newer techniques using tissue engineering to regenerate musculoskeletal tissue by using biomimetic materials are now being studied. These osteoconductive three dimensional constructs seeded with MSCs are highly porous, biodegradable and biomechanically stable scaffolds which do not evoke an immunogenic host cell response. Research has shown the importance of growth factors in guiding and modulating the differentiation of MSCs in order to obtain the required cell type. Gene-based delivery systems have aided the delivery of sustained quantities of these growth factors. The evidence from growth factor enhanced tissue engineering studies for tissue healing looks very positive. This is a multi-disciplinary approach that integrates molecular, biochemical and clinical techniques with developmental and engineering processes. Initial studies indicate an immense potential for cell based strategies to enhance current orthopaedic approaches in skeletal tissue reconstruction. Ultimately, there is a need for randomised controlled trials on human populations to apply these findings to a clinical setting. Nevertheless, stem cell based tissue engineering in orthopaedics shows a promising future.

Biomedical Applications of Biodegradable Polymers

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Assessment of growth factor treatment on fibrochondrocyte and chondrocyte co-cultures for TMJ fibrocartilage engineering

Treatments for patients suffering from severe temporomandibular joint (TMJ) dysfunction are limited, motivating the development of strategies for tissue regeneration. In this study, co-cultures of fibrochondrocytes (FCs) and articular chondrocytes (ACs) were seeded in agarose wells, and supplemented with growth factors, to engineer tissue with biomechanical properties and extracellular matrix composition similar to native TMJ fibrocartilage. In the first phase, growth factors were applied alone and in combination, in the presence or absence of serum, while in the second phase, the best overall treatment was applied at intermittent dosing. Continuous treatment of AC/FC co-cultures with TGF-β1 in serum-free medium resulted in constructs with glycosaminoglycan/wet weight ratios (12.2%), instantaneous compressive moduli (790 kPa), relaxed compressive moduli (120 kPa) and Young's moduli (1.87 MPa) that overlap with native TMJ disc values. Among co-culture groups, TGF-β1 treatment increased collagen deposition ∼20%, compressive stiffness ∼130% and Young's modulus ∼170% relative to controls without growth factor. Serum supplementation, though generally detrimental to functional properties, was identified as a powerful mediator of FC construct morphology. Finally, both intermittent and continuous TGF-β1 treatment showed positive effects, though continuous treatment resulted in greater enhancement of construct functional properties. This work proposes a strategy for regeneration of TMJ fibrocartilage and its future application will be realized through translation of these findings to clinically viable cell sources.

Controlled delivery of transforming growth factor β1 by self-assembling peptide hydrogels induces chondrogenesis of bone marrow stromal cells and modulates Smad2/3 signaling

Self-assembling peptide hydrogels were modified to deliver transforming growth factor β1 (TGF-β1) to encapsulated bone-marrow-derived stromal cells (BMSCs) for cartilage tissue engineering applications using two different approaches: (i) biotin-streptavidin tethering; (ii) adsorption to the peptide scaffold. Initial studies to determine the duration of TGF-β1 medium supplementation necessary to stimulate chondrogenesis showed that 4 days of transient soluble TGF-β1 to newborn bovine BMSCs resulted in 10-fold higher proteoglycan accumulation than TGF-β1-free culture after 3 weeks. Subsequently, BMSC-seeded peptide hydrogels with either tethered TGF-β1 (Teth-TGF) or adsorbed TGF-β1 (Ads-TGF) were cultured in the TGF-β1-free medium, and chondrogenesis was compared to that for BMSCs encapsulated in unmodified peptide hydrogels, both with and without soluble TGF-β1 medium supplementation. Ads-TGF peptide hydrogels stimulated chondrogenesis of BMSCs as demonstrated by cell proliferation and cartilage-like extracellular matrix accumulation, whereas Teth-TGF did not stimulate chondrogenesis. In parallel experiments, TGF-β1 adsorbed to agarose hydrogels stimulated comparable chondrogenesis. Full-length aggrecan was produced by BMSCs in response to Ads-TGF in both peptide and agarose hydrogels, whereas medium-delivered TGF-β1 stimulated catabolic aggrecan cleavage product formation in agarose but not peptide scaffolds. Smad2/3 was transiently phosphorylated in response to Ads-TGF but not Teth-TGF, whereas medium-delivered TGF-β1 produced sustained signaling, suggesting that dose and signal duration are potentially important for minimizing aggrecan cleavage product formation. Robustness of this technology for use in multiple species and ages was demonstrated by effective chondrogenic stimulation of adult equine BMSCs, an important translational model used before the initiation of human clinical studies.

EF1alpha and RPL13a represent normalization genes suitable for RT-qPCR analysis of bone marrow derived mesenchymal stem cells

Background

RT-qPCR analysis is a widely used method for the analysis of mRNA expression throughout the field of mesenchymal stromal cell (MSC) research. Comparison between MSC studies, both in vitro and in vivo, are challenging due to the varied methods of RT-qPCR data normalization and analysis. Therefore, this study focuses on putative housekeeping genes for the normalization of RT-qPCR data between heterogeneous commercially available human MSC, compared with more homogeneous populations of MSC such as MIAMI and RS-1 cells.

Results

Eight genes including; ACTB, B2M, EF1α, GAPDH, RPL13a, YWHAZ, UBC and HPRT1 were tested as possible housekeeping genes based on their expression level and variability. EF1α and RPL13a were validated for RT-qPCR analysis of MIAMI cells during expansion in varied oxygen tensions, endothelial differentiation, neural precursor enrichment, and during the comparison with RS-1 cells and commercially available MSC. RPL13a and YWHAZ were validated as normalization genes for the cross-species analysis of MIAMI cells in an animal model of focal ischemia. GAPDH, which is one of the most common housekeeping genes used for the normalization of RT-qPCR data in the field of MSC research, was found to have the highest variability and deemed not suitable for normalization of RT-qPCR data.

Conclusions

In order to make comparisons between heterogeneous MSC populations, as well as adult stem cell like MSC which are used in different laboratories throughout the world, it is important to have a standardized, reproducible set of housekeeping genes for RT-qPCR analysis. In this study we demonstrate that EF1α, RPL13a and YWHAZ are suitable genes for the RT-qPCR analysis and comparison of several sources of human MSC during in vitro characterization and differentiation as well as in an ex vivo animal model of global cerebral ischemia. This will allow for the comparative RT-qPCR analysis of multiple MSC populations with the goal of future use in animal models of disease as well as tissue repair.

Osteochondral interface tissue engineering using macroscopic gradients of bioactive signals

Continuous gradients exist at osteochondral interfaces, which may be engineered by applying spatially patterned gradients of biological cues. In the present study, a protein-loaded microsphere-based scaffold fabrication strategy was applied to achieve spatially and temporally controlled delivery of bioactive signals in three-dimensional (3D) tissue engineering scaffolds. Bone morphogenetic protein-2 and transforming growth factor-beta(1)-loaded poly(D,L-lactic-co-glycolic acid) microspheres were utilized with a gradient scaffold fabrication technology to produce microsphere-based scaffolds containing opposing gradients of these signals. Constructs were then seeded with human bone marrow stromal cells (hBMSCs) or human umbilical cord mesenchymal stromal cells (hUCMSCs), and osteochondral tissue regeneration was assessed in gradient scaffolds and compared to multiple control groups. Following a 6-week cell culture, the gradient scaffolds produced regionalized extracellular matrix, and outperformed the blank control scaffolds in cell number, glycosaminoglycan production, collagen content, alkaline phosphatase activity, and in some instances, gene expression of major osteogenic and chondrogenic markers. These results suggest that engineered signal gradients may be beneficial for osteochondral tissue engineering.