Tissue engineering and regenerative medicine strategies in meniscus lesions

Meniscal repair in vivo using human chondrocyte-seeded PLGA mesh scaffold pretreated with platelet-rich plasma

The objective of this study was to test the hypothesis that platelet-rich plasma (PRP) pretreatment on a poly-lactic-co-glycolic acid (PLGA) mesh scaffold enhances the healing capacity of the meniscus with human chondrocyte-seeded scaffolds in vivo, even when the seeded number of cells was reduced from 10 million to one million. A flexible PLGA mesh scaffold was pretreated with PRP using a centrifugal technique. One million human articular chondrocytes were seeded onto the scaffold by dynamic oscillation. After 7 days, scaffolds were placed between human meniscal discs and were implanted subcutaneously in nude mice for 6 weeks (n = 16/group). Fluorescence microscopy demonstrated uniform attachment of the chondrocytes throughout the scaffolds 24 h following seeding. Cell attachment analysis revealed a significantly increased number of chondrocytes on PRP-pretreated than non-treated scaffolds (p < 0.05). Field emission scanning electron microscopy revealed chondrocytes attached to the PRP-pretreated scaffolds interconnecting their cellular processes with the fibrin network at 24 h and day 7 of culture. Of the 16 constructs containing PRP-pretreated scaffolds implanted in mice, six menisci healed completely, nine healed incompletely and one did not heal. Histological results from the 16 control constructs containing non-treated scaffolds revealed that none had healed completely, four healed incompletely and 12 did not heal. The histological outcome between the groups was significantly different (p < 0.05). These findings suggest that human articular chondrocytes on PRP-pretreated PLGA mesh scaffolds demonstrate increased cell attachment and enhance the healing capacity of meniscus with a reduced number of seeding cells in a meniscal repair mouse model. Copyright © 2014 John Wiley & Sons, Ltd.

Polyurethane scaffold in lateral meniscus segmental defects: clinical outcomes at 24 months follow-up

BACKGROUND

Segmental tissue loss in the lateral meniscus is associated with pain and increased risk of osteoarthritis even when indications have been carefully considered.

HYPOTHESIS

Repairing the defect using a novel biodegradable scaffold will reduce pain and restore the knee function.

METHODS

In this prospective multicenter study, a total of 54 patients (37 males/17 females; mean age: 28 years [16-50]) were enrolled. All patients presented with postmeniscectomy syndrome and segmental lateral meniscus loss, and were treated with a polyurethane biodegradable scaffold (Actifit(®), Orteq) implanted arthroscopically. Clinical outcomes were assessed at 6, 12 and 24 months using Visual Analogue Scale (VAS), International Knee Documentation Committee Score (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

VAS decreased from 5.5 at baseline to 3.6 at 6 months, 3.4 at 12 months and 2.9 at 24 months. IKDC improved from 47.0 at baseline to 60.2, 67.0 and 67.0 at 6, 12 and 24 months. All KOOS subscores improved between baseline and 24 months.

DISCUSSION

Clinical results of this study demonstrate clinically and statistically significant improvements of pain and function scores (VAS, IKDC, and all KOOS subscales except sport), at the 6 months follow-up and on all clinical outcomes at the 2-year follow-up. The Actifit(®) scaffold is safe and effective in treating lateral meniscus defects.

LEVEL OF EVIDENCE IV

continuous prospective multicenter study.

Biodegradable polyurethane meniscal scaffold for isolated partial lesions or as combined procedure for knees with multiple comorbidities: clinical results at 2 years

PURPOSE

The aim of this study is to evaluate the safety and clinical efficacy of this novel polyurethane meniscal scaffold to treat partial meniscal loss.

METHODS

Eighteen patients (11 men and 7 women, mean age: 45 years) affected by irreparable acute meniscal tears requiring partial meniscectomy or chronic prior loss of meniscal tissue were enrolled in the study. They underwent arthroscopic polyurethane meniscal scaffold implantation (13 medial and 5 lateral) and, in case of presence of other comorbidities, concurrent procedures were also performed. Patients were prospectively evaluated up to 2 years of follow-up through IKDC objective, IKDC subjective, and Tegner scores. Furthermore, MRI evaluation of the meniscal scaffold was performed.

RESULTS

No major adverse events were observed. A statistically significant increase in all the clinical parameters considered was found. The IKDC objective score increased from 61 % of normal or nearly normal knees at basal evaluation to 94 % at 2 years of follow-up (p = 0.01). There was also a significant increase in the IKDC subjective score both at 6-12 months of follow-up (p = 0.03 and p < 0.005), which was confirmed at 24 months. The Tegner score also showed a significant increase from the pre-operative level (median value 2, range 1-5) to final evaluation (median value 3, range 2-5; p = 0.005), albeit not reaching the pre-injury sports activity level.

CONCLUSIONS

The implantation of this novel polyurethane scaffold proved to be a safe and potentially effective procedure to treat partial meniscal loss with encouraging results at short-term follow-up. Further high-quality studies with larger numbers of patients and longer evaluation times are needed to confirm these preliminary data.

Matrix forming characteristics of inner and outer human meniscus cells on 3D collagen scaffolds under normal and low oxygen tensions

Background

Limited intrinsic healing potential of the meniscus and a strong correlation between meniscal injury and osteoarthritis have prompted investigation of surgical repair options, including the implantation of functional bioengineered constructs. Cell-based constructs appear promising, however the generation of meniscal constructs is complicated by the presence of diverse cell populations within this heterogeneous tissue and gaps in the information concerning their response to manipulation of oxygen tension during cell culture.

Methods

Four human lateral menisci were harvested from patients undergoing total knee replacement. Inner and outer meniscal fibrochondrocytes (MFCs) were expanded to passage 3 in growth medium supplemented with basic fibroblast growth factor (FGF-2), then embedded in porous collagen type I scaffolds and chondrogenically stimulated with transforming growth factor β3 (TGF-β3) under 21% (normal or normoxic) or 3% (hypoxic) oxygen tension for 21 days. Following scaffold culture, constructs were analyzed biochemically for glycosaminoglycan production, histologically for deposition of extracellular matrix (ECM), as well as at the molecular level for expression of characteristic mRNA transcripts.

Results

Constructs cultured under normal oxygen tension expressed higher levels of collagen type II (p = 0.05), aggrecan (p < 0.05) and cartilage oligomeric matrix protein, (COMP) (p < 0.05) compared to hypoxic expanded and cultured constructs. Accumulation of ECM rich in collagen type II and sulfated proteoglycan was evident in normoxic cultured scaffolds compared to those under low oxygen tension. There was no significant difference in expression of these genes between scaffolds seeded with MFCs isolated from inner or outer regions of the tissue following 21 days chondrogenic stimulation (p > 0.05).

Conclusions

Cells isolated from inner and outer regions of the human meniscus demonstrated equivalent differentiation potential toward chondrogenic phenotype and ECM production. Oxygen tension played a key role in modulating the redifferentiation of meniscal fibrochondrocytes on a 3D collagen scaffold in vitro.

Advances in regenerative orthopedics

Orthopedic injuries are common and a source of much misery and economic stress. Several relevant tissues, such as cartilage, meniscus, and intra-articular ligaments, do not heal. And even bone, which normally regenerates spontaneously, can fail to mend. The regeneration of orthopedic tissues requires 4 key components: cells, morphogenetic signals, scaffolds, and an appropriate mechanical environment. Although differentiated cells from the tissue in question can be used, most cellular research focuses on the use of mesenchymal stem cells. These can be retrieved from many different tissues, and one unresolved question is the degree to which the origin of the cells matters. Embryonic and induced pluripotent stem cells are also under investigation. Morphogenetic signals are most frequently supplied by individual recombinant growth factors or native mixtures provided by, for example, platelet-rich plasma; mesenchymal stem cells are also a rich source of trophic factors. Obstacles to the sustained delivery of individual growth factors can be addressed by gene transfer or smart scaffolds, but we still lack detailed, necessary information on which delivery profiles are needed. Scaffolds may be based on natural products, synthetic materials, or devitalized extracellular matrix. Strategies to combine these components to regenerate tissue can follow traditional tissue engineering practices, but these are costly, cumbersome, and not well suited to treating large numbers of individuals. More expeditious approaches make full use of intrinsic biological processes in vivo to avoid the need for ex vivo expansion of autologous cells and multiple procedures. Clinical translation remains a bottleneck.

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.

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.

Animal models for meniscus repair and regeneration

The meniscus plays an important role in knee function and mechanics. Meniscal lesions, however, are common phenomena and this tissue is not able to achieve spontaneous successful repair, particularly in the inner avascular zone. Several animal models have been studied and proposed for testing different reparative approaches, as well as for studying regenerative methods aiming to restore the original shape and function of this structure. This review summarizes the gross anatomy, function, ultrastructure and biochemical composition of the knee meniscus in several animal models in comparison with the human meniscus. The relevance of the models is discussed from the point of view of basic research as well as of clinical translation for meniscal repair, substitution and regeneration. Finally, the advantages and disadvantages of each model for various research directions are critically discussed.

Regression modeling to inform cell incorporation into therapies for craniosynostosis

Designing an appropriate tissue engineering solution for craniosynostosis (CS) necessitates determination of whether CS-derived cells differ from normal (wild-type, WT) cells and what assays are appropriate to test for differences. Traditional methodologies to statistically compare cellular behavior may not accurately reflect biologically relevant differences because they poorly address variation. Here, logistic regression was used to determine which assays could identify a biological difference between WT and CS progenitor cells. Quantitative alkaline phosphatase and MTS proliferation assays were performed on adipose, muscle, and bone marrow-derived cells from WT and CS rabbits. Data were stratified by assay, cell type, and days in culture. Coefficients of variation were calculated and assay results coded as predictive variables. Phenotype (WT or CS) was coded as the dependent variable. Sensitivity-specificity curves, classification tables, and receiver operating characteristic curves were plotted for discriminating models. Two data sets were utilized for subsequent analyses; one was used to develop the logistic regression models for prediction, and the other independent data set was used to determine the ability to predict group membership based on the predictive equation. The resulting coefficients of variation were high for all differentiation measures. Upon model implementation, bone marrow assays were observed to result in 72%-100% predictability for phenotype. We found predictive differences in our muscle-derived and bone marrow-derived cells suggesting biologically relevant differences. This data analysis methodology could help identify homogenous cells that do not differ between pathologic and normal individuals or cells that differ in their osteogenic potential, depending on the type of cell-based therapy being developed.

Scaffolds for partial meniscal replacement: an updated systematic review

INTRODUCTION

Meniscectomy, a most common orthopaedic procedure, results in increased contact area of the articular surfaces of tibia and femur leading to early osteoarthritis. We systematically review the literature on clinical outcomes following partial meniscal replacement using different scaffolds.

SOURCES OF DATA

We performed a comprehensive search of Medline, CINAHL, Embase and the Cochrane Central Registry of Controlled Trials. The reference lists of the selected articles were then examined by hand. Only studies focusing on investigation of clinical outcomes on patients undergoing a partial meniscal replacement using a scaffold were selected. We then evaluated the methodological quality of each article using the Coleman methodology score (CMS), a 10 criteria scoring list assessing the methodological quality of the selected studies (CMS).

AREAS OF AGREEMENT

Fifteen studies were included, all prospective studies, but only 2 were randomized controlled trials. Biological scaffolds were involved in 12 studies, 2 studies investigated synthetic scaffolds, whereas 1 remaining article presented data from the use of both classes of device. The mean modified CMS was 64.6.

AREAS OF CONTROVERSY

Several demographic and biomechanical factors could influence the outcomes of this treatment modality.

GROWING POINTS

Partial replacement using both classes of scaffolds achieves significant and encouraging improved clinical results when compared with baseline values or with controls when present, without no adverse reaction related to the device.

RESEARCH

There is a need for more and better designed randomized trials, to confirm with a stronger level of evidence the promising preliminary results achieved by the current research.

Repair of meniscal lesions using a scaffold-free tissue-engineered construct derived from allogenic synovial MSCs in a miniature swine model

The menisci of the knee are fibro-cartilaginous tissues and play important roles in the joint, and the loss of the meniscus predisposes the knee to degenerative changes. However, the menisci have limited healing potential due to the paucity of vascularity. The purpose of the present study was to test the feasibility of a scaffold-free tissue-engineered construct (TEC) derived from synovial mesenchymal stem cells (MSCs) to repair incurable meniscal lesions. Porcine synovial MSCs were cultured in monolayers at high density in the presence of ascorbic acid followed by the suspension culture to develop a three-dimensional cell/matrix construct (TEC). A 4-mm cylindrical defect was created bilaterally in the medial meniscus of skeletally mature miniature pigs. The defects were implanted with an allogenic TEC or were left empty. After 6 months, the TEC-treated defects were consistently repaired by a fibro-cartilaginous tissue with good tissue integration to the adjacent host meniscal tissue, while the untreated were either partially or not repaired. The ratio of Safranin O positive area within the central body of the meniscus adjacent to the original defect was significantly higher in the TEC-treated group than in the control group. Moreover, TEC treatment significantly reduced the size and severity of post-traumatic chondral lesions on the tibial plateau. These results suggest that the TEC could be a promising stem cell-based implant to repair meniscal lesions with preventive effects from meniscal body degeneration and the development of post-traumatic arthritis.

Matrix formation is enhanced in co-cultures of human meniscus cells with bone marrow stromal cells

The ultimate aim of this study was to assess the feasibility of using human bone marrow stromal cells (BMSCs) to supplement meniscus cells for meniscus tissue engineering and regeneration. Human menisci were harvested from three patients undergoing total knee replacements. Meniscus cells were released from the menisci after collagenase treatment. BMSCs were harvested from the iliac crest of three patients and were expanded in culture until passage 2. Primary meniscus cells and BMSCs were co-cultured in vitro in three-dimensional (3D) pellet culture at three different cell-cell ratios for 3 weeks under normal (21% O2 ) or low (3% O2 ) oxygen tension in the presence of serum-free chondrogenic medium. Pure BMSCs and pure meniscus cell pellets served as control groups. The tissue generated was assessed biochemically, histochemically and by quantitative RT-PCR. Co-cultures of primary meniscus cells and BMSCs resulted in tissue with increased (1.3-1.7-fold) deposition of proteoglycan (GAG) extracellular matrix (ECM) relative to tissues derived from BMSCs or meniscus cells alone under 21% O2 . GAG matrix formation was also enhanced (1.3-1.6-fold) under 3% O2 culture conditions. Alcian blue staining of generated tissue confirmed increased deposition of GAG-rich matrix. mRNA expression of type I collagen (COL1A2), type II collagen (COL2A1) and aggrecan were upregulated in co-cultured pellets. However, SOX9 and HIF-1α mRNA expression were not significantly modulated by co-culture. Co-culture of primary meniscus cells with BMSCs resulted in increased ECM formation. Co-delivery of meniscus cells and BMSCs can, in principle, be used in tissue engineering and regenerative medicine strategies to repair meniscus defects.

Emerging technologies for assembly of microscale hydrogels

Assembly of cell encapsulating building blocks (i.e., microscale hydrogels) has significant applications in areas including regenerative medicine, tissue engineering, and cell-based in vitro assays for pharmaceutical research and drug discovery. Inspired by the repeating functional units observed in native tissues and biological systems (e.g., the lobule in liver, the nephron in kidney), assembly technologies aim to generate complex tissue structures by organizing microscale building blocks. Novel assembly technologies enable fabrication of engineered tissue constructs with controlled properties including tunable microarchitectural and predefined compositional features. Recent advances in micro- and nano-scale technologies have enabled engineering of microgel based three dimensional (3D) constructs. There is a need for high-throughput and scalable methods to assemble microscale units with a complex 3D micro-architecture. Emerging assembly methods include novel technologies based on microfluidics, acoustic and magnetic fields, nanotextured surfaces, and surface tension. In this review, we survey emerging microscale hydrogel assembly methods offering rapid, scalable microgel assembly in 3D, and provide future perspectives and discuss potential applications.