Decreased hypertrophic differentiation accompanies enhanced matrix formation in co-cultures of outer meniscus cells with bone marrow mesenchymal stromal cells

Mesenchymal Stem Cells From Different Sources in Meniscus Repair and Regeneration

Meniscus damage is a common trauma that often arises from sports injuries or menisci tissue degeneration. Current treatment methods focus on the repair, replacement, and regeneration of the meniscus to restore its original function. The advance of tissue engineering provides a novel approach to restore the unique structure of the meniscus. Recently, mesenchymal stem cells found in tissues including bone marrow, peripheral blood, fat, and articular cavity synovium have shown specific advantages in meniscus repair. Although various studies explore the use of stem cells in repairing meniscal injuries from different sources and demonstrate their potential for chondrogenic differentiation, their meniscal cartilage-forming properties are yet to be systematically compared. Therefore, this review aims to summarize and compare different sources of mesenchymal stem cells for meniscal repair and regeneration.

Evaluation of culture conditions for in vitro meniscus repair model systems using bone marrow-derived mesenchymal stem cells

Purpose: Meniscal injury and loss of meniscus tissue lead to osteoarthritis development. Therefore, novel biologic strategies are needed to enhance meniscus tissue repair. The purpose of this study was to identify a favorable culture medium for both bone marrow-derived mesenchymal stem cells (MSCs) and meniscal tissue, and to establish a novel meniscus tissue defect model that could be utilized for in vitro screening of biologics to promote meniscus repair.Materials and Methods: In parallel, we analyzed the biochemical properties of MSC - seeded meniscus-derived matrix (MDM) scaffolds and meniscus repair model explants cultured in different combinations of serum, dexamethasone (Dex), and TGF-β. Next, we combined meniscus tissue and MSC-seeded MDM scaffolds into a novel meniscus tissue defect model to evaluate the effects of chondrogenic and meniscal media on the tissue biochemical properties and repair strength.Results: Serum-free medium containing TGF-β and Dex was the most promising formulation for experiments with MSC-seeded scaffolds, whereas serum-containing medium was the most effective for meniscus tissue composition and integrative repair. When meniscus tissue and MSC-seeded MDM scaffolds were combined into a defect model, the chondrogenic medium (serum-free with TGF-β and Dex) enhanced the production of proteoglycans and promoted integrative repair of meniscus tissue. As well, cross-linked scaffolds improved repair over the MDM slurry.Conclusions: The meniscal tissue defect model established in this paper can be used to perform in vitro screening to identify and optimize biological treatments to enhance meniscus tissue repair prior to conducting preclinical animal studies.

Human Cartilage-Derived Progenitors Resist Terminal Differentiation and Require CXCR4 Activation to Successfully Bridge Meniscus Tissue Tears

Meniscus injuries are among the most common orthopedic injuries. Tears in the inner one‐third of the meniscus heal poorly and present a significant clinical challenge. In this study, we hypothesized that progenitor cells from healthy human articular cartilage (chondroprogenitor cells [C‐PCs]) may be more suitable than bone‐marrow mesenchymal stem cells (BM‐MSCs) to mediate bridging and reintegration of fibrocartilage tissue tears in meniscus. C‐PCs were isolated from healthy human articular cartilage based on their expression of mesenchymal stem/progenitor marker activated leukocyte cell adhesion molecule (ALCAM) (CD166). Our findings revealed that healthy human C‐PCs are CD166+, CD90+, CD54+, CD106‐ cells with multilineage differentiation potential, and elevated basal expression of chondrogenesis marker SOX‐9. We show that, similar to BM‐MSCs, C‐PCs are responsive to the chemokine stromal cell‐derived factor‐1 (SDF‐1) and they can successfully migrate to the area of meniscal tissue damage promoting collagen bridging across inner meniscal tears. In contrast to BM‐MSCs, C‐PCs maintained reduced expression of cellular hypertrophy marker collagen X in monolayer culture and in an explant organ culture model of meniscus repair. Treatment of C‐PCs with SDF‐1/CXCR4 pathway inhibitor AMD3100 disrupted cell localization to area of injury and prevented meniscus tissue bridging thereby indicating that the SDF‐1/CXCR4 axis is an important mediator of this repair process. This study suggests that C‐PCs from healthy human cartilage may potentially be a useful tool for fibrocartilage tissue repair/regeneration because they resist cellular hypertrophy and mobilize in response to chemokine signaling. stem cells2019;37:102–114

Current Concepts in Meniscus Tissue Engineering and Repair

The meniscus is the most commonly injured structure in the human knee. Meniscus deficiency has been shown to lead to advanced osteoarthritis (OA) due to abnormal mechanical forces, and replacement strategies for this structure have lagged behind other tissue engineering endeavors. The challenges include the complex 3D structure with individualized size parameters, the significant compressive, tensile and shear loads encountered, and the poor blood supply. In this progress report, a review of the current clinical treatments for different types of meniscal injury is provided. The state-of-the-art research in cellular therapies and novel cell sources for these therapies is discussed. The clinically available cell-free biomaterial implants and the current progress on cell-free biomaterial implants are reviewed. Cell-based tissue engineering strategies for the repair and replacement of meniscus are presented, and the current challenges are identified. Tissue-engineered meniscal biocomposite implants may provide an alternative solution for the treatment of meniscal injury to prevent OA in the long run, because of the limitations of the existing therapies.

Osteoarthritic human chondrocytes proliferate in 3D co-culture with mesenchymal stem cells in suspension bioreactors

Osteoarthritis (OA) is a painful disease, characterized by progressive surface erosion of articular cartilage. The use of human articular chondrocytes (hACs) sourced from OA patients has been proposed as a potential therapy for cartilage repair, but this approach is limited by the lack of scalable methods to produce clinically relevant quantities of cartilage-generating cells. Previous studies in static culture have shown that hACs co-cultured with human mesenchymal stem cells (hMSCs) as 3D pellets can upregulate proliferation and generate neocartilage with enhanced functional matrix formation relative to that produced from either cell type alone. However, because static culture flasks are not readily amenable to scale up, scalable suspension bioreactors were investigated to determine if they could support the co-culture of hMSCs and OA hACs under serum-free conditions to facilitate clinical translation of this approach. When hACs and hMSCs (1:3 ratio) were inoculated at 20,000 cells/ml into 125-ml suspension bioreactors and fed weekly, they spontaneously formed 3D aggregates and proliferated, resulting in a 4.75-fold increase over 16 days. Whereas the apparent growth rate was lower than that achieved during co-culture as a 2D monolayer in static culture flasks, bioreactor co-culture as 3D aggregates resulted in a significantly lower collagen I to II mRNA expression ratio and more than double the glycosaminoglycan/DNA content (5.8 vs. 2.5 μg/μg). The proliferation of hMSCs and hACs as 3D aggregates in serum-free suspension culture demonstrates that scalable bioreactors represent an accessible platform capable of supporting the generation of clinical quantities of cells for use in cell-based cartilage repair.

Coculture of meniscus cells and mesenchymal stem cells in simulated microgravity

Simulated microgravity has been shown to enhance cartilaginous matrix formation by chondrocytes and chondrogenesis of mesenchymal stem cells (MSCs). Similarly, coculture of primary chondrocytes with MSCs has been shown as a strategy to simultaneously retain the differentiated phenotype of chondrocytes and enhance cartilaginous matrix formation. In this study, we investigated the effect of simulated microgravity on cocultures of primary human meniscus cells and adipose-derived MSCs. We used biochemical, qPCR, and immunofluorescence assays to conduct our investigation. Simulated microgravity significantly enhanced cartilaginous matrix formation in cocultures of primary meniscus cells and adipose-derived MSCs. The enhancement was accompanied by increased hypertrophic differentiation markers, COL10A1 and MMP-13, and suppression of hypertrophic differentiation inhibitor, gremlin 1 (GREM1).

Co-culture of meniscal cartilage-forming cells with fat-derived stem cells can lead to enhanced cartilage matrix production when cultured under simulated microgravity. Adetola Adesida from the University of Alberta in Edmonton, Canada, and colleagues cultured two types of cells found together in the knee—cartilage-forming chondrocyte cells (taken from the meniscus) and mesenchymal stem cells (isolated from the infrapatellar fat pad)—in a rotary cell culture system designed to model weightlessness on Earth. Simulated microgravity enhanced the synergistic interaction between the two types of cells in culture, resulting in more matrix production, but it also prompted the cartilage-forming cells to differentiate towards bone-forming cells, as evidenced by gene expression analysis. These findings suggest that microgravity and simulated microgravity-based culture technologies could help bioengineers grow knee replacements for people with meniscus tears, but increased bone-directed differentiation could pose a possible problem for astronauts on prolonged missions.

Cell-Based Meniscus Repair and Regeneration: At the Brink of Clinical Translation?: A Systematic Review of Preclinical Studies

Background:

Meniscus damage can be caused by trauma or degeneration and is therefore common among patients of all ages. Repair or regeneration of the menisci could be of great importance not only for pain relief or regaining function but also to prevent degenerative disease and osteoarthritis. Current treatment does not offer consistent long-term improvement. Although preclinical research focusing on augmentation of meniscal tear repair and regeneration after meniscectomy is encouraging, clinical translation remains difficult.

Purpose:

To systematically evaluate the literature on in vivo meniscus regeneration and explore the optimal cell sources and conditions for clinical translation. We aimed at thorough evaluation of current evidence as well as clarifying the challenges for future preclinical and clinical studies.

Study Design:

Systematic review.

Methods:

A search was conducted using the electronic databases of MEDLINE, Embase, and the Cochrane Collaboration. Search terms included meniscus, regeneration, and cell-based.

Results:

After screening 81 articles based on title and abstract, 51 articles on in vivo meniscus regeneration could be included; 2 additional articles were identified from the references. Repair and regeneration of the meniscus has been described by intra-articular injection of multipotent mesenchymal stromal (stem) cells from adipose tissue, bone marrow, synovium, or meniscus or the use of these cell types in combination with implantable or injectable scaffolds. The use of fibrochondrocytes, chondrocytes, and transfected myoblasts for meniscus repair and regeneration is limited to the combination with different scaffolds. The comparative in vitro and in vivo studies mentioned in this review indicate that the use of allogeneic cells is as successful as the use of autologous cells. In addition, the implantation or injection of cell-seeded scaffolds increased tissue regeneration and led to better structural organization compared with scaffold implantation or injection of a scaffold alone. None of the studies mentioned in this review compare the effectiveness of different (cell-seeded) scaffolds.

Conclusion:

There is heterogeneity in animal models, cell types, and scaffolds used, and limited comparative studies are available. The comparative in vivo research that is currently available is insufficient to draw strong conclusions as to which cell type is the most promising. However, there is a vast amount of in vivo research on the use of different types of multipotent mesenchymal stromal (stem) cells in different experimental settings, and good results are reported in terms of tissue formation. None of these studies compare the effectiveness of different cell-scaffold combinations, making it hard to conclude which scaffold has the greatest potential.

Fiber development and matrix production in tissue-engineered menisci using bovine mesenchymal stem cells and fibrochondrocytes

Mesenchymal stem cells (MSCs) have been investigated with promising results for meniscus healing and tissue engineering. While MSCs are known to contribute to extracellular matrix (ECM) production, less is known about how MSCs produce and align large organized fibers for application to tissue engineering the meniscus. The goal of this study was to investigate the capability of MSCs to produce and organize ECM molecules compared to meniscal fibrochondrocytes (FCCs). Bovine FCCs and MSCs were encapsulated in an anatomically accurate collagen meniscus using monoculture and co-culture of each cell type. Each meniscus was mechanically anchored at the horns to mimic the physiological fixation by the meniscal entheses. Mechanical fixation generates a static mechanical boundary condition previously shown to induce formation of oriented fiber by FCCs. Samples were cultured for 4 weeks and then evaluated for biochemical composition and fiber development. MSCs increased the glycosaminoglycan (GAG) and collagen production in both co-culture and monoculture groups compared to FCC monoculture. Collagen organization was greatest in the FCC monoculture group. While MSCs had increased matrix production, they lacked the fiber organization capabilities of FCCs. This study suggests that GAG production and fiber formation are linked. Co-culture can be used as a means of balancing the synthetic properties of MSCs and the matrix remodeling capabilities of FCCs for tissue engineering applications.

Stem Cell Therapy: Current Applications and Potential for Urology

Stem cell therapy holds the potential to revolutionize the treatment of a number of chronic conditions. Stem cells ability to home in on injured sites of the body, stimulate angiogenesis, tissue regeneration, immunomodulation, anti-inflammatory, and anti-fibrotic factors have attracted their use in the treatment of many conditions. Urology has registered one of the highest experimental successes using stem cell therapy. However, the rate of clinical applications is comparatively lower. This review takes a look at our efforts so far and what needs to be done in order to maximize the clinical benefit we can derive from stem cells.

Characterization of mesenchymal stem cells and fibrochondrocytes in three-dimensional co-culture: analysis of cell shape, matrix production, and mechanical performance

Background

Bone marrow mesenchymal stem cells (MSCs) have shown positive therapeutic effects for meniscus regeneration and repair. Preliminary in vitro work has indicated positive results for MSC applications for meniscus tissue engineering; however, more information is needed on how to direct MSC behavior. The objective of this study was to examine the effect of MSC co-culture with primary meniscal fibrochondrocytes (FCCs) in a three-dimensional collagen scaffold in fibrochondrogenic media. Co-culture of MSCs and FCCs was hypothesized to facilitate the transition of MSCs to a FCC cell phenotype as measured by matrix secretion and morphology.

Methods

MSCs and FCCs were isolated from bovine bone marrow and meniscus, respectively. Cells were seeded in a 20 mg/mL high-density type I collagen gel at MSC:FCC ratios of 0:100, 25:75, 50:50, 75:25, and 100:0. Constructs were cultured for up to 2 weeks and then analyzed for cell morphology, glycosaminoglycan content, collagen content, and production of collagen type I, II, and X.

Results

Cells were homogeneously mixed throughout the scaffold and cells had limited direct cell–cell contact. After 2 weeks in culture, MSCs transitioned from a spindle-like morphology toward a rounded phenotype, while FCCs remained rounded throughout culture. Although MSC shape changed with culture, the overall size was significantly larger than FCCs throughout culture. While 75:25 and 100:0 (MSC mono-culture) culture groups produced significantly more glycosaminoglycan (GAG)/DNA than FCCs in mono-culture, GAG retention was highest in 50:50 co-cultures. Similarly, the aggregate modulus was highest in 100:0 and 50:50 co-cultures. All samples contained both collagen types I and II after 2 weeks, and collagen type X expression was evident only in MSC mono-culture gels.

Conclusions

MSCs shift to a FCC morphology in both mono- and co-culture. Co-culture reduced hypertrophy by MSCs, indicated by collagen type X. This study shows that MSC phenotype can be influenced by indirect homogeneous cell culture in a three-dimensional gel, demonstrating the applicability of MSCs in meniscus tissue engineering applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0301-8) contains supplementary material, which is available to authorized users.

Crosstalk between adipose-derived stem cells and chondrocytes: when growth factors matter

Adipose-derived stem cells (ASCs) and mesenchymal stem cells are promising for tissue repair because of their multilineage differentiation capacity. Our previous data confirmed that the implantation of mixed ASCs and chondrocytes into cartilage defects induced desirable in vivo healing outcomes. However, the paracrine action of ASCs on chondrocytes needs to be further elucidated. In this study, we established a co-culture system to achieve cell-to-cell and cell-to-tissue crosstalk and explored the soluble growth factors in both ASCs and chondrocytes supplemented with 1% fetal bovine serum to mimic the physiological microenvironment. In ASCs, we screened for growth factors by semi-quantitative PCR and quantitative real-time PCR and found that the expression of bone morphogenetic protein 2 (BMP-2), vascular endothelial growth factor B (VEGFB), hypoxia inducible factor-1α (HIF-1α), fibroblast growth factor-2 (FGF-2), and transforming growth factor-β1 significantly increased after co-culture in comparison with mono-culture. In chondrocytes, VEGFA was significantly enhanced after co-culture. Unexpectedly, the expression of collagen II and aggrecan was significantly down-regulated in the co-culture group compared with the mono-culture group. Meanwhile, among all the growth factors screened, we found that the BMP family members BMP-2, BMP-4, and BMP-5 were down-regulated and that VEGFB, HIF-1α, FGF-2, and PDGF were significantly decreased after co-culture. These results suggest that crosstalk between ASCs and chondrocytes is a pathway through the regulated growth factors that might have potential in cartilage repair and regeneration and could be useful for tissue engineering.

Meniscus repair using mesenchymal stem cells - a comprehensive review

The menisci are a pair of semilunar fibrocartilage structures that play an essential role in maintaining normal knee function. Injury to the menisci can disrupt joint stability and lead to debilitating results. Because natural meniscal healing is limited, an efficient method of repair is necessary. Tissue engineering (TE) combines the principles of life sciences and engineering to restore the unique architecture of the native meniscus. Mesenchymal stem cells (MSCs) have been investigated for their therapeutic potential both in vitro and in vivo. This comprehensive review examines the English literature identified through a database search using Medline, Embase, Engineering Village, and SPORTDiscus. The search results were classified based on MSC type, animal model, and method of MSC delivery/culture. A variety of MSC types, including bone marrow-derived, synovium-derived, adipose-derived, and meniscus-derived MSCs, has been examined. Research results were categorized into and discussed by the different animal models used; namely murine, leporine, porcine, caprine, bovine, ovine, canine, equine, and human models of meniscus defect/repair. Within each animal model, studies were categorized further according to MSC delivery/culture techniques. These techniques included direct application, fibrin glue/gel/clot, intra-articular injection, scaffold, tissue-engineered construct, meniscus tissue, pellets/aggregates, and hydrogel. The purpose of this review is to inform the reader about the current state and advances in meniscus TE using MSCs. Future directions of MSC-based meniscus TE are also suggested to help guide prospective research.

Beneficial effects of coculturing synovial derived mesenchymal stem cells with meniscus fibrochondrocytes are mediated by fibroblast growth factor 1: increased proliferation and collagen synthesis

Meniscus reconstruction is in great need for orthopedic surgeons. Meniscal fibrochondrocytes transplantation was proposed to regenerate functional meniscus, with limited donor supply. We hypothesized that coculture of synovial mesenchymal stem cells (SSC) with meniscal fibrochondrocytes (me-CH) can support matrix production of me-CH, thus reducing the number of me-CH needed for meniscus reconstruction. A pellet coculture system of human SSC and me-CH was used in this study. Enhanced glycosaminoglycans (GAG) in coculture pellets were demonstrated by Alcian blue staining and GAG quantification, when compared to monoculture. More collagen synthesis was shown in coculture pellets by hydroxyproline assay. Increased proliferation of me-CH was observed in coculture. Data from BrdU staining and ELISA demonstrated that conditioned medium of SSCs enhanced the proliferation and collagen synthesis of me-CH, and this effect was blocked by neutralizing antibody against fibroblast growth factor 1 (FGF1). Western blot showed that conditioned medium of SSCs can activate mitogen-activated protein kinase (MAPK) signaling pathways by increasing the phosphorylation of mitogen-activated regulated protein kinase 1/2 (MEK) and extracellular-signal-regulated kinases 1/2 (ERK). Overall, this study provided evidence that synovial MSCs can support proliferation and collagen synthesis of fibrochondrocytes, by secreting FGF1. Coimplantation of SSC and me-CH could be a useful strategy for reconstructing meniscus.

A new method for meniscus repair using type I collagen scaffold and infrapatellar fat pad

AIM

The aim of this study was to investigate a new method for meniscal repair by combinative transplantation with type I collagen scaffold and infrapatellar fat pad.

METHODS

Two-mm cylindrical defects at the anterior part of bilateral medial menisci were prepared in nine Japanese white rabbits. The 18 knees were equally divided into three groups: I, no treatment; II, collagen scaffold transplantation; and III, collagen scaffold and infrapatellar fat pad transplantation. Another three rabbits (six knees) underwent sham surgery and served as controls. Rabbits were sacrificed at eight weeks after transplantation. Surface area of the medial meniscus was evaluated using macrophotographs. Ishida score for meniscal regeneration was used for assessment. To evaluate the composition of regenerated tissue, immunohistochemistry was analyzed with anti-type I and anti-type II collagen antibodies, and anti-Ki67 antibody. To investigate the effects of collagen scaffold on human meniscus, cells were isolated from human meniscus and infrapatellar fat pad, and cultured with collagen scaffold for three weeks. After that, gene expression was evaluated by using quantitative real-time polymerase chain reaction.

RESULTS

In group I, the meniscus shrank anterior to posterior, and the surface area was significantly less than that of normal meniscus. However, the surface area was maintained in group III. Ishida score and Ki67-positive cell ratio in group III were significantly higher than that in any other group, and staining with type I and type II collagen was similar to that of the control. Expression of matrix metalloproteinase was significantly lower in cocultures of collagen scaffold, meniscus cell, and infrapatellar fat pad cell than in monocultured meniscus cell, and expression of interleukin-1β was not increased.

CONCLUSION

This new method for meniscal repair by combinative transplantation with type I collagen scaffold and infrapatellar fat pad showed meniscal regeneration and potential for suppressing inflammation.

Adipose-derived stromal cells protect intervertebral disc cells in compression: implications for stem cell regenerative disc therapy

Introduction: Abnormal biomechanics plays a role in intervertebral disc degeneration. Adipose-derived stromal cells (ADSCs) have been implicated in disc integrity; however, their role in the setting of mechanical stimuli upon the disc's nucleus pulposus (NP) remains unknown. As such, the present study aimed to evaluate the influence of ADSCs upon NP cells in compressive load culture.

Methods: Human NP cells were cultured in compressive load at 3.0MPa for 48 hours with or without ADSCs co-culture (the ratio was 50:50). We used flow cytometry, live/dead staining and scanning electron microscopy (SEM) to evaluate cell death, and determined the expression of specific apoptotic pathways by characterizing the expression of activated caspases-3, -8 and -9. We further used real-time (RT-) PCR and immunostaining to determine the expression of the extracellular matrix (ECM), mediators of matrix degradation (e.g. MMPs, TIMPs and ADAMTSs), pro-inflammatory factors and NP cell phenotype markers.

Results: ADSCs inhibited human NP cell apoptosis via suppression of activated caspase-9 and caspase-3. Furthermore, ADSCs protected NP cells from the degradative effects of compressive load by significantly up-regulating the expression of ECM genes (SOX9, COL2A1 and ACAN), tissue inhibitors of metalloproteinases (TIMPs) genes (TIMP-1 and TIMP-2) and cytokeratin 8 (CK8) protein expression. Alternatively, ADSCs showed protective effect by inhibiting compressive load mediated increase of matrix metalloproteinases (MMPs; MMP-3 and MMP-13), disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs; ADAMTS-1 and 5), and pro-inflammatory factors (IL-1beta, IL-6, TGF-beta1 and TNF-alpha).

Conclusions: Our study is the first in vitro study assessing the impact of ADSCs on NP cells in an un-physiological mechanical stimulation culture environment. Our study noted that ADSCs protect compressive load induced NP cell death and degradation by inhibition of activated caspase-9 and -3 activity; regulating ECM and modulator genes, suppressing pro-inflammatory factors and preserving CK8. Consequently, the protective impact of ADSCs found in this study provides an essential understanding and expands our knowledge as to the utility of ADSCs therapy for intervertebral disc regeneration.

Advances in tissue engineering through stem cell-based co-culture

Stem cells are the future in tissue engineering and regeneration. In a co-culture, stem cells not only provide a target cell source with multipotent differentiation capacity, but can also act as assisting cells that promote tissue homeostasis, metabolism, growth and repair. Their incorporation into co-culture systems seems to be important in the creation of complex tissues or organs. In this review, critical aspects of stem cell use in co-culture systems are discussed. Direct and indirect co-culture methodologies used in tissue engineering are described, along with various characteristics of cellular interactions in these systems. Direct cell-cell contact, cell-extracellular matrix interaction and signalling via soluble factors are presented. The advantages of stem cell co-culture strategies and their applications in tissue engineering and regenerative medicine are portrayed through specific examples for several tissues, including orthopaedic soft tissues, bone, heart, vasculature, lung, kidney, liver and nerve. A concise review of the progress and the lessons learned are provided, with a focus on recent developments and their implications. It is hoped that knowledge developed from one tissue can be translated to other tissues. Finally, we address challenges in tissue engineering and regenerative medicine that can potentially be overcome via employing strategies for stem cell co-culture use.

Effect of interleukin-1β treatment on co-cultures of human meniscus cells and bone marrow mesenchymal stromal cells

Background

Interleukin-1β (IL-1β) is a major mediator of local inflammation present in injured joints. In this study, we aimed at comparing the effect of IL-1β on engineered tissues from MCs, BMSCs and co-cultured MCs and BMSCs.

Methods

We compared the effect of IL-1β in 3 groups: (1) MCs, (2) BMSCs and, (3) co-cultures of MCs and BMSCs. We selected 1 to 3 ratio of MCs to BMSCs for the co-cultures. Passage two (P2) human BMSCs were obtained from two donors. Human MCs were isolated from menisci of 4 donors. Mono-cultures of MCs and BMSCs, and co-cultures of MCs and BMSCs were cultured in chondrogenic medium with TGFβ3, as cell pellets for 14 days. Thereafter, pellets were cultured for 3 more days in same medium as before with or without IL-1β (500 pg/ml). Pellets were assessed histologically, biochemically and by RT-PCR for gene expression of aggrecan, sox9, MMP-1, collagens I and II. Statistics was performed using one-way ANOVA with Tukey’s post-tests.

Results

Co-cultured pellets were the most intensely stained with safranin O and collagen II. Co-cultured pellets had the highest expression of sox9, collagen I and II. IL-1β treatment slightly reduced the GAG/DNA of co-cultured pellets but still exceeded the sum of the GAG/DNA from the proportion of MCs and BMSCs in the co-cultured pellets. After IL-1β treatment, the expression of sox9, collagen I and II in co-cultured pellets was higher compared to their expression in pure pellets. IL-1β induced MMP-1 expression in mono-cultures of MCs but not significantly in mono-cultures of BMSCs or in co-cultured pellets. IL-1β induced MMP-13 expression in mono-cultured pellets of BMSCs and in co-cultured pellets.

Conclusions

Co-cultures of MCs and BMSCs resulted in a synergistic production of cartilaginous matrix compared to mono-cultures of MCs and BMSCs. IL-1β did not abrogate the accumulated GAG matrix in co-cultures but mediated a decreased mRNA expression of aggrecan, collagen II and Sox9. These results strengthen the combinatorial use of primary MCs and BMSCs as a cell source for meniscus tissue engineering by demonstrating retention of fibrochondrogenic phenotype after exposure to IL-1β.

Digital micromirror device projection printing system for meniscus tissue engineering

Meniscus degeneration due to age or injury can lead to osteoarthritis. Although promising, current cell-based approaches show limited success. Here we present three-dimensional methacrylated gelatin (GelMA) scaffolds patterned via projection stereolithography to emulate the circumferential alignment of cells in native meniscus tissue. Cultured human avascular zone meniscus cells from normal meniscus were seeded on the scaffolds. Cell viability was monitored, and new tissue formation was assessed by gene expression analysis and histology after 2weeks in serum-free culture with transforming growth factor β1 (10ngml(-1)). Light, confocal and scanning electron microscopy were used to observe cell-GelMA interactions. Tensile mechanical testing was performed on unseeded, fresh scaffolds and 2-week-old cell-seeded and unseeded scaffolds. 2-week-old cell-GelMA constructs were implanted into surgically created meniscus defects in an explant organ culture model. No cytotoxic effects were observed 3weeks after implantation, and cells grew and aligned to the patterned GelMA strands. Gene expression profiles and histology indicated promotion of a fibrocartilage-like meniscus phenotype, and scaffold integration with repair tissue was observed in the explant model. We show that micropatterned GelMA scaffolds are non-toxic, produce organized cellular alignment, and promote meniscus-like tissue formation. Prefabrication of GelMA scaffolds with architectures mimicking the meniscus collagen bundle organization shows promise for meniscal repair. Furthermore, the technique presented may be scaled up to repair larger defects.

Meniscus reconstruction: today's achievements and premises for the future

Injuries of the meniscus remain a burden for the development of premature cartilage degeneration and osteoarthritis. This review surveys all treatment options and focuses on the recent development of tissue engineering. Tissue engineering of the meniscus means a successful combination of cells, scaffolds and specific stimuli. Each element of the combination can be subject to variation. Studies investigating the optimum meniscus implant and previous steps in producing these implants are presented in this article. A comprehensive search of the English and German literature was performed in PubMed to retrieve appropriate manuscripts for review. Based on the literatures, autografts and allografts can delay the progress of osteoarthritis for a restricted time period, but several concerns persist. The biomechanical properties of the native meniscus are not copied entirely by the current existing autografts. Congruence, fixation, biocompatibility and potential infection will always remain as limitations for the users of allografts. Long-term results are still not available for meniscus prosthesis and even though it permits fast recovery, several aspects are questionable: bioincompatibility and a lack of cellular adhesion are likely to compromise their long-term fate. Currently, there is no ideal implant generated by means of tissue engineering. However, meniscus tissue engineering is a fast developing field, which promises to develop an implant that mimics histological and biomechanical properties of the native meniscus. At present several cell sources and scaffolds have been used successfully to grow 3-dimensional constructs. In future, optimal implants have to be developed using growth factors, modified scaffolds and stimuli that support cellular proliferation and differentiation to regenerate the native meniscus more closely.