Repair of articular cartilage defects with cultured chondrocytes in Atelocollagen gel. Comparison with cultured chondrocytes in suspension

Human Chondrocytes, Metabolism of Articular Cartilage, and Strategies for Application to Tissue Engineering

Hyaline cartilage, which is characterized by the absence of vascularization and innervation, has minimal self-repair potential in case of damage and defect formation in the chondral layer. Chondrocytes are specialized cells that ensure the synthesis of extracellular matrix components, namely type II collagen and aggregen. On their surface, they express integrins CD44, α1β1, α3β1, α5β1, α10β1, αVβ1, αVβ3, and αVβ5, which are also collagen-binding components of the extracellular matrix. This article aims to contribute to solving the problem of the possible repair of chondral defects through unique methods of tissue engineering, as well as the process of pathological events in articular cartilage. In vitro cell culture models used for hyaline cartilage repair could bring about advanced possibilities. Currently, there are several variants of the combination of natural and synthetic polymers and chondrocytes. In a three-dimensional environment, chondrocytes retain their production capacity. In the case of mesenchymal stromal cells, their favorable ability is to differentiate into a chondrogenic lineage in a three-dimensional culture.

Intraarticular Implantation of Autologous Chondrocytes Placed on Collagen or Polyethersulfone Scaffolds: An Experimental Study in Rabbits

Hyaline cartilage has very limited repair capability and cannot be rebuilt predictably using conventional treatments. This study presents Autologous Chondrocyte Implantation (ACI) on two different scaffolds for the treatment of lesions in hyaline cartilage in rabbits. The first one is a commercially available scaffold (Chondro-Gide) made of collagen type I/III and the second one is a polyethersulfone (PES) synthetic membrane, manufactured by phase inversion. The revolutionary idea in the present study is the fact that we used PES membranes, which have unique features and benefits that are desirable for the 3D cultivation of chondrocytes. Sixty-four White New Zealand rabbits were used in this research. Defects penetrating into the subchondral bone were filled with or without the placement of chondrocytes on collagen or PES membranes after two weeks of culture. The expression of the gene encoding type II procollagen, a molecular marker of chondrocytes, was evaluated. Elemental analysis was performed to estimate the weight of tissue grown on the PES membrane. The reparative tissue was analyzed macroscopically and histologically after surgery at 12, 25, and 52 weeks. RT-PCR analysis of the mRNA isolated from cells detached from the polysulphonic membrane revealed the expression of type II procollagen. The elementary analysis of polysulphonic membrane slices after 2 weeks of culture with chondrocytes revealed a concentration of 0.23 mg of tissue on one part of the membrane. Macroscopic and microscopic evaluation indicated that the quality of regenerated tissue was similar after the transplantation of cells placed on polysulphonic or collagen membranes. The established method for the culture and transplantation of chondrocytes placed on polysulphonic membranes resulted in the growth of the regenerated tissue, revealing the morphology of hyaline-like cartilage to be of similar quality to collagen membranes.

Effect of Platelet-Rich Plasma on Autologous Chondrocyte Implantation for Chondral Defects: Results Using an In Vivo Rabbit Model

Background:

Articular cartilage repair remains challenging despite the availability of techniques, including autologous chondrocyte implantation (ACI) for repairing large cartilage defects. Platelet-rich plasma (PRP) therapy, a novel therapy focused on chondrocyte regeneration, needs to be investigated regarding its potential to improve the outcomes of ACI.

Purpose:

To examine the effect of PRP therapy on the outcomes of cartilage repair using the ACI procedure in a rabbit model of knee joint cartilage damage.

Study Design:

Controlled laboratory study.

Methods:

A total of 30 knees in 15 Japanese White rabbits (joint cartilage damage model) were divided into nontreatment (n = 7), PRP (n = 8), ACI (n = 7), and combined ACI and PRP (n = 8) groups. At 4 weeks and 12 weeks postoperatively, histological and visual examination of the surgical site was performed, and the regenerated cartilage and calcified bone areas were measured by imaging the specimens.

Results:

Pretransplantation evaluation in the cultured cartilage showed the histological properties of hyaline cartilage. At 4 weeks postoperatively, the regenerated cartilage area at the surgical site showed a larger safranin O–positive area in the ACI group (2.73 ± 4.46 mm²) than in the combined ACI and PRP group (1.71 ± 2.04 mm²). Calcified bone formation in the ACI group was relatively lower than that in the other groups. Cartilage repair failure occurred in all groups at 12 weeks postoperatively.

Conclusion:

The authors found no positive effects of PRP on the outcomes of ACI in a rabbit model. There was a smaller safranin O–positive region with the addition of PRP to ACI compared with ACI alone. In the subchondral bone, bone formation might have been promoted by PRP.

Clinical Relevance:

Administering PRP at the time of ACI may not have a positive effect and may have deleterious effects on cartilage engraftment and regeneration.

The Benefit of Minced Cartilage Over Isolated Chondrocytes in Atelocollagen Gel on Chondrocyte Proliferation and Migration

OBJECTIVE

Autologous chondrocyte implantation is a necessary procedure for the repair of articular cartilage defects; however, isolated chondrocyte implantation requires a 2-step procedure (for harvesting and implantation) and is limited by cytotoxicity due to enzymatic digestion. Therefore, in this in vitro study, we evaluated the possible benefit of using minced cartilage embedded in a 3-dimensional culture scaffold and fixed with fibrin glue, in comparison with isolated chondrocytes in atelocollagen, to induce cell migration, proliferation, and matrix production, using cartilage from patients with knee joint osteoarthritis.

DESIGN

Cartilage fragments were obtained from 7 female patients with knee osteoarthritis (OA) and embedded in atelocollagen gels. As a control, chondrocytes were isolated and embedded in gels in the same manner. These composites were cultured for 3 weeks, and cell proliferation and matrix production were evaluated using histology and immunochemistry.

RESULTS

Histologically, minced cartilage showed cell migration from the cartilage fragments into the gel, with the Bern score and cell count in the minced cartilage group being significantly higher than those in the control group. Immunohistochemistry revealed that the number of Ki67-positive cells, the expression of LECT-1 and TGF-β, and the glycosaminoglycan content were significantly higher in the minced cartilage than in the control group. Minced cartilage exhibited superior cell migration, proliferation, and glycosaminoglycan content than isolated chondrocytes.

CONCLUSION

Our findings support that minced cartilage has a favorable potential for cell proliferation and matrix production compared with the isolated chondrocytes after enzymatic treatment.

The usefulness of the decellularized matrix from three-dimensional regenerative cartilage as a scaffold material

In cartilage tissue engineering, research on materials for three-dimensional (3D) scaffold has attracted attention. Decellularized matrix can be one of the candidates for the scaffold material. In this study, decellularization of regenerated cartilage was carried out and its effectiveness as a scaffold material was examined. Three-dimensionally-cultured cartilage constructs in the differentiation medium containing IGF-1 produced more cartilage matrix than those in the proliferation medium. Detergent-enzymatic method (DEM) could decellularize 3D-cultured cartilage constructs only by 1 cycle without breaking down the structure of the constructs. In vitro, newly-seeded chondrocytes were infiltrated and engrafted into decellularized constructs in the proliferation medium, and newly formed fibers were observed around the surface where newly-seeded cells were attached. Recellularized constructs could mature similarly as those without decellularization in vivo. The decellularized 3D-cultured matrix from regenerative cartilage is expected to be used as a scaffold material in the future.

In vivo cartilage regeneration in a multi-layered articular cartilage architecture mimicking scaffold

AIMS

Extracellular matrix (ECM) and its architecture have a vital role in articular cartilage (AC) structure and function. We hypothesized that a multi-layered chitosan-gelatin (CG) scaffold that resembles ECM, as well as native collagen architecture of AC, will achieve superior chondrogenesis and AC regeneration. We also compared its in vitro and in vivo outcomes with randomly aligned CG scaffold.

METHODS

Rabbit bone marrow mesenchymal stem cells (MSCs) were differentiated into the chondrogenic lineage on scaffolds. Quality of in vitro regenerated cartilage was assessed by cell viability, growth, matrix synthesis, and differentiation. Bilateral osteochondral defects were created in 15 four-month-old male New Zealand white rabbits and segregated into three treatment groups with five in each. The groups were: 1) untreated and allogeneic chondrocytes; 2) multi-layered scaffold with and without cells; and 3) randomly aligned scaffold with and without cells. After four months of follow-up, the outcome was assessed using histology and immunostaining.

RESULTS

In vitro testing showed that the secreted ECM oriented itself along the fibre in multi-layered scaffolds. Both types of CG scaffolds supported cell viability, growth, and matrix synthesis. In vitro chondrogenesis on scaffold showed an around 400-fold increase in collagen type 2 (COL2A1) expression in both CG scaffolds, but the total glycosaminoglycan (GAG)/DNA deposition was 1.39-fold higher in the multi-layered scaffold than the randomly aligned scaffold. In vivo cartilage formation occurred in both multi-layered and randomly aligned scaffolds treated with and without cells, and was shown to be of hyaline phenotype on immunostaining. The defects treated with multi-layered + cells, however, showed significantly thicker cartilage formation than the randomly aligned scaffold.

CONCLUSION

We demonstrated that MSCs loaded CG scaffold with multi-layered zonal architecture promoted superior hyaline AC regeneration.Cite this article: Bone Joint Res 2020;9(9):601-612.

Atelocollagen Application in Human Periodontal Tissue Treatment-A Pilot Study

Background: The aim of this study is the clinical observation of gingival tissue condition after atelocollagen injection. Methods: In 18 patients, 97 gingival class I Miller recessions were divided according to recession height, gingival papillae loss and thickness of gingivae. Atelocollagen (Linerase, 100 mg) was injected into keratinized gingivae twice or thrice, at two-week intervals. Results: Statistically significant changes in gingival recession, amount of gingival papillae loss and thickness of gingiva were observed, after both two and three collagen injections. Although the degree (height) of recession decreased and gingival tissue thickness increased with every injection; there was no difference in gingival papillae loss between second and third collagen injections. Conclusions: The injectable form of atelocollagen is a promising material for gingival soft tissue regeneration and stimulation and allows for reduction in the number of procedures and support in a variety of surgical scenarios. This is a pilot study that clinically measures the impact of injected atelocollagen on periodontal tissue biotype, including the thickness of gingivae and gingival papillae regeneration.

Proliferation medium in three-dimensional culture of auricular chondrocytes promotes effective cartilage regeneration in vivo

Introduction

Cartilage regeneration have been attracted attentions because of the poor ability of cartilage tissues to regenerate. Three-dimensional (3D) culture of chondrocytes is considered to be advantageous for cartilage regeneration. Although it is plausible that maturation of the constructs before transplantation positively affects the chondrogenesis, matured constructs after cultures for longer periods do not necessarily result in effective cartilage regeneration. In this study, we compared different types of culture media including growth factors which are clinically available. We prepared differentiation medium containing insulin-like growth factor-1 (IGF-1), proliferation medium containing fibroblast growth factor-2 (FGF-2) and insulin, and combination of them, and compared their efficacies on chondrogenesis when used in 3D culture of engineered cartilage constructs.

Methods

Cartilage constructs were fabricated by auricular chondrocytes and atelocollagen, and they were 3D-cultured with four types of media: control medium, differentiation medium, proliferation medium, and combination medium. After 3 weeks of culture, the constructs were analyzed for cell number, gene and protein expressions and mechanical properties. The constructs were also transplanted into nude mice. After 8 weeks, the degree of cartilage regeneration was evaluated. Constructs manufactured with canine auricular chondrocytes were subjected to autologous transplantation into beagles and examined for cartilage regeneration.

Results

During 3D culture, remarkably high gene expression of type II collagen was detected in the construct cultured with the differentiation medium whereas cell apoptosis were suppressed in the proliferation medium. When transplanted into nude mice, the constructs 3D-cultured in the proliferation medium produced abundant cartilage matrices. In autologous implantation model, the construct cultured in the proliferation medium again showed better chondrogenesis than those in other media.

Conclusions

The present study indicates that 3D culture with the proliferation medium maintains the cell viability to potentiate the subsequent cartilage regeneration. Here, we propose that not only differentiation but also high cell viability accompanied by proliferation factors should be taken into account to improve cartilage regeneration.

Repair of an Osteochondral Defect With Minced Cartilage Embedded in Atelocollagen Gel: A Rabbit Model

BACKGROUND

Autologous chondrocyte implantation (ACI) is often performed for large cartilage defects. Because this technique has several disadvantages, including the need for second-stage surgery, cartilage repair using minced cartilage has been suggested. However, this technique could be improved using 3-dimensional scaffolds.

PURPOSE

To examine the ability of chondrocyte migration and proliferation from minced cartilage in atelocollagen gel in vitro and evaluate the repairable potential of minced cartilage embedded in atelocollagen gel covered with a periosteal flap in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Minced cartilage or isolated chondrocytes from rabbits were embedded in atelocollagen gel and cultured for 3 weeks. Chondrocyte proliferation and matrix production were evaluated in vitro. An osteochondral defect at the trochlear groove was created in 56 rabbits, which were divided into 4 groups. The defect was left empty (defect group), filled with allogenic minced cartilage (minced cartilage group), filled with isolated allogenic chondrocytes embedded in atelocollagen gel (ACI group), or filled with atelocollagen gel (atelocollagen with periosteal flap group). At 4, 12, and 24 weeks after surgery, repair of the defect was evaluated in these 4 groups.

RESULTS

In vitro, the number of chondrocytes and abundant matrix on the surface of the gel significantly increased in the minced cartilage group compared with the ACI group (P < .05). In vivo, the minced cartilage and ACI groups showed good cartilage repair compared with the empty defect and atelocollagen/periosteal flap groups (P < .05); there was no significant difference in the Pineda score between the minced cartilage and ACI groups.

CONCLUSION

Minced cartilage in atelocollagen gel had good chondrocyte migration and proliferation abilities in vitro, and osteochondral defects were well repaired by implanting minced cartilage embedded in the atelocollagen gel in vivo. Implantation of minced cartilage embedded in atelocollagen gel showed good cartilage repair equivalent to ACI.

CLINICAL RELEVANCE

Implantation of minced cartilage embedded in atelocollagen gel as a 1-step procedure has outcomes similar to those of ACI but is cheaper and more convenient than ACI.

A novel, self-assembled artificial cartilage-hydroxyapatite conjugate for combined articular cartilage and subchondral bone repair: histopathological analysis of cartilage tissue engineering in rat knee joints

Purpose

We previously created a self-assembled cartilage-like complex in vitro from only three cartilage components, hyaluronic acid (HA), aggrecan (AG) and type II collagen, without other materials such as cross-linking agents. Based on this self-organized AG/HA/collagen complex, we have created three novel types of biphasic cartilage and bone-like scaffolds combined with hydroxyapatite (HAP) for osteochondral tissue engineering. These scaffolds have been developed from self-assembled cartilage component molecules and HAP at the nanometer scale by manipulating the intermolecular relations.

Patients and methods

The surface structure of each self-organized biphasic cartilage and bone-like scaffold was evaluated by scanning electron microscopy, whereas the viscoelasticity was also analyzed in vitro. Three types of artificial cartilage–HAP conjugates were implanted into an osteochondral defect in rat knee joints, and bone and cartilage tissues of the implanted site were examined 4 and 8 weeks after implantation. The tissues were examined histopathologically to evaluate the effects of the implantation on the articular cartilage and subchondral bone tissues.

Results

Our in vitro and in vivo data reveal that the self-organized biphasic cartilage and bone-like scaffold conjugated with HAP are superior to the scaffold with no HAP in both cartilage regeneration and subchondral bone regeneration.

Conclusion

Our present study indicates that the self-organized biphasic cartilage and bone-like scaffold, which is conjugated with an HAP layer, may have potential not only to repair articular cartilage defects but also to ameliorate the degeneration of subchondral bone in the diseases with osteochondral defect.

Recent strategies in cartilage repair: A systemic review of the scaffold development and tissue engineering

Osteoarthritis results in irreparable loss of articular cartilage. Due to its avascular nature and low mitotic activity, cartilage has little intrinsic capacity for repair. Cartilage loss leads to pain, physical disability, movement restriction, and morbidity. Various treatment strategies have been proposed for cartilage regeneration, but the optimum treatment is yet to be defined. Tissue engineering with engineered constructs aimed towards developing a suitable substrate may help in cartilage regeneration by providing the mechanical, biological and chemical support to the cells. The use of scaffold as a substrate to support the progenitor cells or autologous chondrocytes has given promising results. Leakage of cells, poor cell survival, poor cell differentiation, inadequate integration into the host tissue, incorrect distribution of cells, and dedifferentiation of the normal cartilage are the common problems in tissue engineering. Current research is focused on improving mechanical and biochemical properties of scaffold to make it more efficient. The aim of this review is to provide a critical discussion on existing challenges, scaffold type and properties, and an update on ongoing recent developments in the architecture and composition of scaffold to enhance the proliferation and viability of mesenchymal stem cells. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2343-2354, 2017.

Hydrogel based cartilaginous tissue regeneration: recent insights and technologies

Hydrogel based technologies has been extensively employed in both exploratory research and clinical applications to address numerous existing challenges in the regeneration of articular cartilage and intervertebral disc.

Delayed gadolinium-enhanced MRI of cartilage and T2 mapping for evaluation of reparative cartilage-like tissue after autologous chondrocyte implantation associated with Atelocollagen-based scaffold in the knee

OBJECTIVE

To elucidate the quality of tissue-engineered cartilage after an autologous chondrocyte implantation (ACI) technique with Atelocollagen gel as a scaffold in the knee in the short- to midterm postoperatively, we assessed delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) and T2 mapping and clarified the relationship between T1 and T2 values and clinical results.

MATERIALS AND METHODS

In this cross-sectional study, T1 and T2 mapping were performed on 11 knees of 8 patients (mean age at ACI, 37.2 years) with a 3.0-T MRI scanner. T1implant and T2implant values were compared with those of the control cartilage region (T1control and T2control). Lysholm scores were also assessed for clinical evaluation. The relationships between the T1 and T2 values and the clinical Lysholm score were also assessed.

RESULTS

There were no significant differences in the T1 values between the T1implant (386.64 ± 101.78 ms) and T1control (375.82 ± 62.89 ms) at the final follow-up. The implants showed significantly longer T2 values compared to the control cartilage (53.83 ± 13.89 vs. 38.21 ± 4.43 ms). The postoperative Lysholm scores were significantly higher than the preoperative scores. A significant correlation was observed between T1implant and clinical outcomes, but not between T2implant and clinical outcomes.

CONCLUSION

Third-generation ACI implants might have obtained an almost equivalent glycosaminoglycan concentration compared to the normal cartilage, but they had lower collagen density at least 3 years after transplantation. The T1implant value, but not the T2 value, might be a predictor of clinical outcome after ACI.

PCL-PEG-PCL film promotes cartilage regeneration in vivo

OBJECTIVE

Management of chondral defects has long been a challenge due to poor self-healing capacity of articular cartilage. Many approaches, ranging from symptomatic treatment to structural cartilage regeneration, have obtained very limited satisfactory results. Cartilage tissue engineering, which involves optimized combination of novel scaffolds, cell sources and growth factors, has emerged as a promising strategy for cartilage regeneration and repair. In this study, the aim was to investigate the role of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) PCEC scaffold in cartilage repair.

MATERIALS AND METHODS

First, PCEC film was fabricated, and its characteristics were tested using SEM and AFM. Cell (rASC - rat adipose-derived stem cells, and mASCs - green fluorescent mouse adipose-derived stem cells) morphologies on PCEC film were observed using SEM and fluorescence microscopy, after cell seeding. Tests of cell viability on PCEC film were conducted using the CCK-8 assay. Furthermore, full cartilage defects in rats were created, and PCEC films were implanted, to evaluate their healing effects, over 8 weeks.

RESULTS

It was found that PCEC film, as a biomaterial implant, possessed good in vitro properties for cell adhesion, migration and proliferation. Importantly, in the in vivo experiment, PCEC film exhibited desirable healing outcomes.

CONCLUSIONS

These results demonstrated that PCEC film was a good scaffold for cartilage tissue engineering for improving cell proliferation and adhesion and could lead to excellent repair of cartilage defects.

P34HB film promotes cell adhesion, in vitro proliferation, and in vivo cartilage repair

The management of chondral defects is a challenging topic of current interest for scientists and surgeons, which has a crucial impact on human cost.

Articular cartilage repair: procedures versus products

This review discusses the current perspectives and practices regarding the treatment of articular cartilage injury. Specifically, the authors have delineated and examined articular cartilage repair techniques as either surgical procedures or manufactured products. Although both methodologies are used to treat articular cartilage injury, there are obvious advantages and disadvantages to the application of both, with the literature providing few recommendations on the most suitable regimen for the patient and surgeon. In recent times, cell-based tissue engineering products, predominantly autologous chondrocyte implantation, have been the subject of much research and have become clinically popular. Herein, we review the most used procedures and products in cartilage repair, compare and contrast their outcomes, and evaluate the issues that must be overcome in order to improve patient efficacy in the future.

Surgical options for articular defects of the knee

Cartilage and osteochondral defects of the knee can in most cases be treated with total knee replacement in the elderly population. However, these lesions pose a difficult treatment problem in the younger patient. A number of surgical options are available today to address this increasingly common condition and each has its own indications and limitations. This article reviews debridement and microfracture, fixation, metallic spacing devices, autologous chondrocyte implantation, osteochondral autograft transplantation, fresh cadaveric allografts and osteotomies. In addition, possible future developments are discussed.

Cell-free repair of small cartilage defects in the Goettinger minipig: The effects of BMP-7 continuously released by poly(lactic-co-glycolid acid) microspheres

Objective

Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed after treatment with cell-free collagen type-I gel with or without additional BMP-7 loaded poly(lactic-co-glycolid acid) microspheres.

Methods

Two full-thickness chondral defects were created in the trochlear groove of one hind leg knee in six Goettinger minipigs. Six defects were treated with a cell-free collagen type-I gel plug of 10 mm, the corresponding six defects were treated with a cell-free collagen type-I plug with poly(lactic-co-glycolid acid) microspheres loaded with recombinant BMP-7 (100 ng/ml gel). After 1 year, the animals were sacrificed. Immediately after recovery, non-destructive biomechanical testing was performed. The repair tissue quality was evaluated by immunohistochemistry and the O’Driscoll score was calculated.

Results

After 1 year, a robust cellular migration into the cell-free collagen gel plugs occurred and a hyaline-like repair tissue was found. Collagen type-II production and cellular organisation were higher in the BMP-7 microsphere group. The determination of the E-modulus, creep and relaxation revealed that mechanical properties of the BMP-7 microsphere group in summary were closer to control hyaline cartilage.

Conclusions

While all specimens revealed a homogeneous cellular distribution, ECM production, cellular organisation and mechanical properties were enhanced by continuous BMP-7 release.

Therapeutic superiority for cartilage repair by CD271-positive marrow stromal cell transplantation

Recent reports indicated that human isolated CD271+ bone marrow mesenchymal stromal cells (BM-MSCs) have a greater expansion and potential for multipotent differentiation including chondrogenesis than classical plastic adherent (PA) BM-MSCs in vitro. Therefore, we set up a hypothesis that CD271+ MSCs may have a greater chondrogenic potential than PA-MSCs in vitro and in vivo. We investigated the superiority of CD271+ MSCs on chondrogenesis using in vitro expansion and pellet culture system and in vivo rat model of cartilage defect when compared to PA-MSCs. In the in vitro study, CD271+ MSCs showed higher expansion potential and produced larger pellets with higher expressions of chondrogenic genes when compared to the control groups. During the culture, CD271 expression decreased, which resulted in decreased chondrogenesis. In the in vivo study, immunohistochemical staining demonstrated differentiated human chondrocytes identified as double-stained cells with human-specific collagen type 2 and human leukocyte antigen-ABC in CD271+ and PA groups. The number of double-stained cells was significantly higher in the CD271+ group than PA group. Real-time RT-PCR analysis of tissue RNA isolated from the chondral defect site for human-specific chondrogenic markers demonstrated a significantly higher expression in CD271+ group than PA group. Macroscopic examination of chondral defect sites at week 8 revealed glossy white and well-integrated repaired tissues in the CD271+ and PA groups, but not in the PBS group. The average histological score in the CD271+ group was significantly greater than in the other groups. Apoptosis analysis at the cell transplanted site with TUNEL staining showed that the CD271+ group had significantly fewer apoptotic chondrocytes compared with the PA group. These results indicate that CD271+ MSCs have a greater chondrogenic potential than PA-MSCs in both in vitro and in vivo conditions.

Evaluation of magnetic resonance imaging and clinical outcome after tissue-engineered cartilage implantation: prospective 6-year follow-up study

BACKGROUND

Autologous chondrocyte implantation (ACI) is an important procedure when repairing cartilage defects of the knee. We previously reported several basic studies on tissue-engineered cartilage, and conducted a multicenter clinical study in 2009. In this clinical study, we evaluated the patients' clinical scores and MRI findings before and after tissue-engineered cartilage implantation, and compared the data obtained at 1 year and approximately 6 years post-implantation.

METHODS

Fourteen patients who underwent implantation of tissue-engineered cartilage to repair cartilage defects of the knee were evaluated. Tissue-engineered cartilage was produced by culturing autologous chondrocytes three dimensionally in atelocollagen gel. The patients were evaluated clinically using the Lysholm score, and the original knee-function score at pre-implantation and at 1 year and approximately 6 years post-implantation. MRI scans were obtained at the same observation periods. A modified magnetic resonance observation of cartilage repair tissue (MOCART) system was used to quantify clinical efficacy based on the MRI findings.

RESULTS

In approximately 6 years of follow-up, none of the 14 patients reported any subjective symptoms of concern. The mean Lysholm score and the original knee-function score (63.0 ± 10.1, 59.9 ± 5.7) significantly improved at 1 year after implantation (86.4 ± 11.8, 94.1 ± 9.2), and were maintained until 6 years after implantation (89.8 ± 6.2, 89.9 ± 11.2), although some patients showed deterioration of Lysholm and original knee scores between 1 year post-implantation and the final follow-up. The mean MOCART score was 13.2 ± 12.0 pre-implantation, and 62.5 ± 24.7 at 1 year and 70.7 ± 22.7 at approximately 6 years post-implantation. The MOCART scores at 1 year and 6 years were significantly higher than the pre-implantation score, but there was no significant difference between the scores at 1 and 6 years, indicating that the MRI results at 1 year after implantation were maintained for the next 5 years.

CONCLUSIONS

The clinical scores and MRI findings after implantation of tissue-engineered cartilage were improved at 1 year after implantation and were maintained until 6 years after implantation.

A comparative study of 3 different cartilage repair techniques

PURPOSE

The value of cell-free techniques in the treatment of cartilage defects remains under debate. In this study, cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed by treatment with a cell-free collagen type-I gel or a collagen type-I gel seeded with autologous chondrocytes. As a control, abrasion arthroplasty was included.

METHODS

In 18 adult Goettinger minipigs, three full-thickness chondral defects were created in one knee of the hind leg. They were either treated with a cell-free collagen gel, a collagen gel seeded with 2 × 10(5)/ml chondrocytes, or left untreated. All animals were allowed unlimited weight bearing. At 6, 12, and 52 weeks, 6 animals were sacrificed. Immediately after recovery, a non-destructive biomechanical testing was performed. The repair tissue quality was evaluated histologically, and the O'Driscoll score was calculated.

RESULTS

After 6 weeks, a high number of cells migrated into the initially cell-free collagen gel. After 1 year, a hyaline-like repair tissue in both groups has been created. As assessed by O'Driscoll scoring and col-II staining, repair tissue quality of the initially cell-free gel was equal to defects treated by cell-seeded collagen gel implantation after 1 year. All untreated control defects displayed a fibrous repair tissue. The mechanical properties represented by the e-modulus were inconsistent in the course of the study.

CONCLUSIONS

The implantation of a cell-free collagen type-I gel can lead to a high-quality repair tissue in the Goettinger minipig that equals a cell-based procedure after 1 year postoperatively. This study demonstrates the high chondrogenic potential of the applied collagen gel, which might help to overcome the disadvantages inherent in conventional cartilage tissue engineering methods.

Potential of exogenous cartilage proteoglycan as a new material for cartilage regeneration

BACKGROUND

Although proteoglycan (PG) is one of the major components of cartilage matrices, its biological function is not fully elucidated.

METHODS

The objectives of this study were to investigate the proliferation and differentiation of chondrocytes embedded in atelocollagen gel with exogenous cartilage PG (PG-atelocollagen gel) in vitro, and also to evaluate the repair of cartilage defects by PG-atelocollagen gel in vivo. In the in vitro study, rabbit chondrocytes were cultured in the PG-atelocollagen gel. Cell proliferation and mRNA expression levels were measured, and gels were histologically evaluated. In the in vivo study, cultured PG-atelocollagen gel containing chondrocytes were transplanted into full-thickness articular cartilage defects in rabbit knees, and evaluated macroscopically and histologically.

RESULTS

For the in vitro study, chondrocyte proliferation in 5.0 mg/ml PG-atelocollagen gel was enhanced, and the gene expression of Col2a1 and Aggrecan were decreased. In contrast, chondrocyte proliferation in 0.1 and 1.0 mg/ml PG-atelocollagen gel was not enhanced. The gene expression of Aggrecan in 0.1 and 1.0 mg/ml PG-atelocollagen gel was increased. For the in vivo study, the histological average total score of the 0.1 mg/ml PG-atelocollagen gel was significantly better than that of the group without PG.

CONCLUSIONS

Although the appropriate concentration of PG has not been defined, this study suggests the efficacy of PG for cartilage repair.

Feasibility and limitations of the round robin test for assessment of in vitro chondrogenesis evaluation protocol in a tissue-engineered medical product

Tissue-engineered medical products (TEMPs) should be evaluated before implantation. Therefore, it is indispensable to establish evaluation protocols in regenerative medicine. Whether or not such evaluation protocols are reasonable is generally verified through a 'round robin' test. However, the round robin test for TEMPs intrinsically includes a deficiency, because 'identical' specimens can not be prepared for TEMPs. The aim of the study was to assess the feasibility and limitations of the round robin test for TEMPs by using a prepared evaluation protocol. We adopted tissue-engineered cartilage constructs as delivered specimens and a protocol of measuring sGAG content as an evaluation protocol proposed to ISO TC150/SC7, which is an invasive, but usually applied, method, although non-invasive methods are keenly required in evaluating TEMPs. The results showed that: (a) the coefficient of variation (CV) of the measured sGAG contents in intralaboratory tests was ~5% at most; (b) the CV of sGAG content in the scheme where each participating laboratory measured different constructs was comparable with that in the scheme where each participating laboratory measured one half of a construct along with the organizing laboratory; (c) the CV caused by factors other than the specimen was ~15%, comparable to that in reproducible experiments in biomedical fields. Based on these results, the study concludes that a round robin test for a TEMP could be valuable, under the condition that the delivered TEMPs are sufficiently reproducible so that the CV of the measured values is < 5% in the organizing laboratory.

Spatiotemporal control of proliferation and differentiation of bone marrow-derived mesenchymal stem cells recruited using collagen hydrogel for repair of articular cartilage defects

Articular cartilage has a poor healing capacity, and cartilage regeneration is not always warranted to achieve healing. On the other hand, collagen scaffolds have been shown to support regeneration of articular cartilage defects in animal models, whereas bone morphogenetic protein-2 (BMP-2) is known to cause chondrogenic differentiation of marrow-derived mesenchymal stem cells (MSCs). The purpose of this study was to evaluate the effectiveness of intra-articular administration of BMP-2 into bone marrow-derived MSCs recruited to defects using original collagen hydrogel in rabbits at various time points. Full-thickness defects were created in both knees, then collagen hydrogels were transplanted, and BMP-2 was supplied for 1-week periods, as follows. BMP-2 was administered immediately after the operation for 1 week (BMP0-1 group), and BMP-2 was administered between weeks 1 and 2 after the operation (BMP1-2 group). BMP2 was administered between weeks 2 and 3 (BMP2-3 group). Specimens were then obtained, and bromodeoxyuridine (BrdU)-positive cells were enumerated and histologic grading was also performed. In addition, the gene expression analysis was performed using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) assays. Enumeration of BrdU-positive cells showed a significant increase in the BMP0-1 group compared with the other groups. Similarly, histologic scores in the BMP0-1 group were superior for up to 8 weeks. Finally, RT-PCR findings revealed that immediate BMP-2 administration enhanced chondrogenic differentiation.

Efficacy of Self-assembled Hydrogels Composed of Positively or Negatively Charged Peptides as Scaffolds for Cell Culture

KASEA16(+) and KASEA16(−) peptides, the net charges of which are positive and negative, respectively, under a neutral condition could undergo self-assembly into nanofibers and form transparent hydrogels without peptide aggregation upon rapid pH neutralization. The numbers of NIH3T3 cells attached to the KASEA16(+) hydrogel and KASEA16(−) hydrogel were similar, and cells proliferated with time on both hydrogels. Cells on the KASEA16(+) hydrogel had spindle-like morphology, while cells on the KASEA16(−) hydrogel formed clusters without extending cytoplasmic processes. Comparison of differently charged peptides under a neutral condition suggested that the charges of the scaffolds should be taken into consideration for the best design and selection of scaffolds for cell culture. Since the KASEA16(+) peptide could form a stable hydrogel under a neutral condition and the hydrogel served as a scaffold for cell proliferation, the KASEA16(+) hydrogel will be a useful scaffold for cell culture.

Atelocollagen-associated autologous chondrocyte implantation for the repair of chondral defects of the knee: a prospective multicenter clinical trial in Japan

BACKGROUND

New tissue-engineering technology was developed to create a cartilage-like tissue in a three-dimensional culture using atelocollagen gel. The minimum 2-year followup outcome of transplanting autologous chondrocytes cultured in atelocollagen gel for the treatment of full-thickness defects of cartilage in knees was reported from the single institution. The present multicenter study was conducted to determine clinical and arthroscopic outcomes in patients who underwent atelocollagen-associated autologous chondrocyte implantation for the repair of chondral defects of the knees.

METHODS

At six medical institutes in Japan, we prospectively evaluated the clinical and arthroscopic outcomes of transplanting autologous chondrocytes cultured in atelocollagen gel for the treatment of full-thickness defects of cartilage in 27 patients (27 knees) with cartilage lesions on a femoral condyle or on a patellar facet over 24 months.

RESULTS

The Lysholm score significantly increased from 60.0 +/- 13.7 points to 89.8 +/- 9.5 points (P = 0.001). Concerning the ICRS grade for arthroscopic appearance, 6 knees (24%) were assessed as grade I (normal) and 17 knees (68%) as grade II (nearly normal). There were few adverse features, except for detachment of the graft in two cases.

CONCLUSIONS

We concluded that transplanting chondrocytes in a newly formed matrix of atelocollagen gel can promote restoration of the articular cartilage of the knee.

Clinical application of scaffolds for cartilage tissue engineering

The purpose of this paper is to review the basic science and clinical literature on scaffolds clinically available for the treatment of articular cartilage injuries. The use of tissue-engineered grafts based on scaffolds seems to be as effective as conventional ACI clinically. However, there is limited evidence that scaffold techniques result in homogeneous distribution of cells. Similarly, few studies exist on the maintenance of the chondrocyte phenotype in scaffolds. Both of which would be potential advantages over the first generation ACI. The mean clinical score in all of the clinical literature on scaffold techniques significantly improved compared with preoperative values. More than 80% of patients had an excellent or good outcome. None of the short- or mid-term clinical and histological results of these tissue-engineering techniques with scaffolds were reported to be better than conventional ACI. However, some studies suggest that these methods may reduce surgical time, morbidity, and risks of periosteal hypertrophy and post-operative adhesions. Based on the available literature, we were not able to rank the scaffolds available for clinical use. Firm recommendations on which cartilage repair procedure is to be preferred is currently not known on the basis of these studies. Randomized clinical trials and longer follow-up periods are needed for more widespread information regarding the clinical effectiveness of scaffold-based, tissue-engineered cartilage repair.

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

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

Rat Cartilage Repair Using Nanophase PLGA/HA Composite and Mesenchymal Stem Cells

Biodegradable polymer/bioceramic composite poly(lactide- coglycolide)/hydroxyapatite(PLGA/HA) was studied for bone tissue engineering. The PLGA/HA composite was evaluated as a scaffold with the ability for mesenchymal stem cells (MSC) to participate in cartilage repair. The PLGA/HA composite and the PLGA/HA composite cultured with MSC were transplanted into cartilage defects created in rats. The PLGA/HA-MSC and PLGA/HA had better tissue morphology, structure integrity, matrix staining, and much thicker newly formed cartilage than the control group. The histological score for PLGA/ HA-MSC better than that for PLGA/HA; it appears that the MSC plays an important role in tissue repair. Based on these results, using PLGA/HA as the tissue scaffold and the addition of MSC significantly enhances cartilage repair.

A novel rat tail collagen type-I gel for the cultivation of human articular chondrocytes in low cell density

Collagen type-I matrix systems have gained growing importance as a cartilage repair device. However, most of the established matrix systems use collagen type-I of bovine origin seeded in high cell densities. Here we present a novel collagen type-I gel system made of rat tail collagen for the cultivation of human chondrocytes in low cell densities. Rat tail collagen type-I gel (CaReS, Arthro Kinetics, Esslingen, Germany) was seeded with human passage 2 chondrocytes in different cell densities to evaluate the optimal cell number. In vitro, the proliferation factor of low density cultures was more than threefold higher compared with high density cultures. After 6 weeks of in vitro cultivation, freshly prepared chondrocytes with an initial cell density of 2x10(5) cells/mL showed a proliferation factor of 33. A cell density of 2x10(5) cells/mL was chosen for in vitro and in vivo cultivation using the common nude mouse model as an in vivo system. Chondrocytes stayed viable as a Live/Dead fluorescence assay and TUNEL staining revealed. During in vitro cultivation, passage 0 cells partly dedifferentiated morphologically. In vivo, passage 0 cells maintained the chondrocyte phenotype and demonstrated an increased synthesis of collagen type-II protein and gene expression compared to passage 2 cells. Passage 2 cells did not redifferentiate in vivo. Cultivating a cell-seeded collagen gel of bovine origin as a control (AtelocollagenTM, Koken, Tokyo, Japan) did not lead to superior results with regard to cell morphology, col-II protein production and col-II gene expression. With the CaReS collagen gel system the best quality of repair tissue was obtained by seeding freshly isolated chondrocytes.

In vitro chondrogenic differentiation of human mesenchymal stem cells in collagen microspheres: influence of cell seeding density and collagen concentration

Given the inadequacies of existing repair strategies for cartilage injuries, tissue engineering approach using biomaterials and stem cells offers new hope for better treatments. Recently, we have fabricated injectable collagen-human mesenchymal stem cell (hMSC) microspheres using microencapsulation. Apart from providing a protective matrix for cell delivery, the collagen microspheres may also act as a bio-mimetic matrix facilitating the functional remodeling of hMSCs. In this study, whether the encapsulated hMSCs can be pre-differentiated into chondrogenic phenotype prior to implantation has been investigated. The effects of cell seeding density and collagen concentration on the chondrogenic differentiation potential of hMSCs have been studied. An in vivo implantation study has also been conducted. Fabrication of cartilage-like tissue micro-masses was demonstrated by positive immunohistochemical staining for cartilage-specific extracellular matrix components including type II collagen and aggrecan. The meshwork of collagen fibers was remodeled into a highly ordered microstructure, characterized by thick and parallel bundles, upon differentiation. Higher cell seeding density and higher collagen concentration favored the chondrogenic differentiation of hMSCs, yielding increased matrix production and mechanical strength of the micro-masses. These micro-masses were also demonstrated to integrate well with the host tissue in NOD/SCID mice.

Repair of full-thickness articular cartilage defects using injectable type II collagen gel embedded with cultured chondrocytes in a rabbit model

BACKGROUND

Recently, tissue-engineered chondrocyte transplantation has been tried to treat full-thickness cartilage defects. We developed an injectable type II collagen gel scaffold by chemically reacting type II collagen with polyethylene glycol crosslinker. This type II collagen was prepared from the nasal septa of cattle. In the present study, chondrocytes embedded in type II collagen gel were injected into rabbit full-thickness cartilage defects without a periosteal graft, and the feasibility for clinical application of the gel was evaluated.

METHODS

Chondrocytes were isolated from 1-kg New Zealand white rabbits. A full-thickness articular cartilage defect (5 mm diameter, 4 mm depth) was created on the patellar groove of the femur of 16 male 3-kg New Zealand white rabbits. A type II collagen solution of mixed chondrocytes at a density of 1 x 10(7) cells/ml was injected and transplanted into the defect in the right knee. The controls were the defect only in the left knee. At 4, 8, 12, and 24 weeks after operation, four cases from each group were evaluated macroscopically and histologically.

RESULTS

After injection into the cartilage defect, the gel bonded to the adjacent cartilage and bone within several minutes. Macroscopic examination revealed that the surface of the transplanted area was smooth and exhibited similar coloration and good integration with the surrounding cartilage at 12 and 24 weeks after transplantation. Histological examination at 8 weeks revealed favorable hyaline cartilage regeneration with good chondrocyte morphology. At 12 and 24 weeks, reparative cartilage remained rich in type II collagen. According to O'Driscoll histological scores, significant differences between the transplanted and control groups were apparent at 12 and 24 weeks. Immunohistochemical staining indicated sufficient type II collagen synthesis in regenerated cartilage 8 weeks after transplantation, and it was maintained until 24 weeks.

CONCLUSIONS

These results indicate that type II collagen gel is suitable for injection into cartilage defects without any covering of a graft and offers a useful scaffold during chondrocyte transplantation.

Comparison of various mixtures of beta-chitin and chitosan as a scaffold for three-dimensional culture of rabbit chondrocytes

With the use of a recently created chitosan neutral hydrogel, we have been able to create various mixtures of chitin and chitosan without changing their characteristics even at room temperature. The aim of this study was the initial comparison of various mixtures of beta-chitin and chitosan as a scaffold for rabbit chondrocyte culture. We created five types of sponges: pure beta-chitin, pure chitosan, 3:1, 1:1, and 1:3 beta-chitin-chitosan. The absorption efficiencies of chondrocytes in all five types of sponges were found to be around 98%. The mean concentrations of chondroitin sulfate were statistically different neither at week 2 nor at week 4 postculture between the types of sponges. The content of hydroxyproline in the beta-chitin sponge was significantly greater than in other sponges at week 4 postculture. From the histochemical and immunohistochemical findings, the cartilage-like layer in the chondrocytes-sponge composites of all five types of sponges was similar to hyaline cartilage. However, only immunohistochemical staining of type II collagen in the pure beta-chitin sponge was closer to normal rabbit cartilage than other types of sponges. The pure beta-chitin sponge was superior to other sponges concerning the content of extracellular matrices of collagen.

Transplantation of tissue-engineered osteochondral plug using cultured chondrocytes and interconnected porous calcium hydroxyapatite ceramic cylindrical plugs to treat osteochondral defects in a rabbit model

The purpose of this study was to evaluate the macroscopic and histological results of transplanting a tissue-engineered composite plug made of tissue-engineered cartilage and interconnected porous calcium hydroxyapatite ceramics (IP-CHA) with a very high porosity of 94.9% to treat osteochondral defects. Twelve 12-week-old male Japanese white rabbits were used. Fresh articular cartilage slices were taken, and isolated chondrocytes (2 x 10(6) cells) were embedded in atelocollagen gel. They were seeded on the top of IP-CHA plugs and cultured for 2 weeks. These tissue-engineered composite plugs were transplanted into the osteochondral defects in the patellar grooves (the experimental group). In the control group, the defects were treated with composite plugs without chondroytes. Twelve weeks after transplantation in the experimental group, the defects were repaired with cartilage-like tissue with good subchondral bone formation histologically. Histological scores in the experimental group were significantly better than those in the control group. This study clearly showed the defects that had been treated with tissue-engineered composite plugs.

BMP-7 loaded microspheres as a new delivery system for the cultivation of human chondrocytes in a collagen type-I gel

In recent years, interest in chondrocyte cultures for transplantation has gained increasing attention. We investigated the use of PGLA microspheres as a new delivery system for BMP-7 and the effects on human chondrocytes cultivated in a 3D collagen gel culture. In an in vitro study, human chondrocytes obtained from osteoarthritic knee joints were released, transferred into a collagen type-I gel, and cultivated up to 14 days. In the treatment group PGLA microspheres loaded with human recombinant BMP-7 protein were added to the matrix. After the cultivation period, histological and immunohistochemical investigations were performed. In addition, the aggrecan core protein and type-II collagen mRNA concentrations were measured by real-time PCR. Histological staining for proteoglycan and collagen type-II protein and quantification via digital image processing revealed a significantly higher content in the samples cultivated with BMP-7 loaded microspheres in comparison to the control samples. Moreover, the collagen gel scaffold was partially remodeled by the chondrocytes and replaced by newly synthesized extracellular matrix. Cellular proliferation as well as apoptosis were low. In conclusion, we consider the PGLA microsphere system to be a functional device for the delivery of growth factors during the cultivation of articular chondrocytes leading to an increased content of type-II collagen and proteoglycan in the extracellular matrix.

Novel elastic material from collagen for tissue engineering

Elastic collagen gel (e-gel) was prepared from salmon atelocollagen fibrillar gel reinforced by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) mediated cross-linking (f-gel). The preparation consisted of a simple heat treatment of the f-gel at 80 degrees C, in which the f-gel drastically shrank and the collagen fibril structure was deformed. The e-gel obtained showed rubber-like elasticity; its stress-strain behavior little changed through repeated stretching. The elongation at the breaking point was approximately 230%. Furthermore, normal human osteoblasts showed good attachment and proliferation on the e-gel. These results suggest its potential to be utilized for the development of tissue engineering.

Mobilization of bone marrow-derived mesenchymal stem cells into the injured tissues after intraarticular injection and their contribution to tissue regeneration

The purpose of present study was to evaluate active mobilization effect of mesenchymal stem cells (MSCs) into injured tissues after intraarticular injection of MSCs, and to evaluate their contribution to tissue regeneration. MSCs, which were obtained from green fluorescent protein (GFP) transgenic Sprague-Dawley (SD) rat and cultivated, were injected into normal SD rats in which multiple tissues had been injured including anterior cruciate ligament (ACL), medial meniscus, and articular cartilage of the femoral condyles. At 4 weeks after injection of MSCs, fluorescent microscopic observation, immunohistochemical or histological examinations were performed to evaluate mobilization of MSCs into injured tissue and their contribution to tissue regeneration. In the group of 1 x 10(6) MSCs injection, GFP positive cells could mobilize into the injured ACL alone in all 8 knees. In the group of 1 x 10(7) MSCs injection, GFP positive cells were observed in the injured site of ACL in all 8 knees and in the injured site of medial meniscus and cartilage of femoral condyles in 6 of 8 knees. More interestingly, extracellular matrix stained by toluidine blue was present around GFP positive cells in the injured femoral condyles cartilage and medial meniscus, indicating tissue regeneration. Intraarticularly injected MSCs could mobilize into the injured tissues, and probably contributed to tissue regeneration. This study demonstrated the possibility of intraarticular injection of MSCs for the treatment of intraarticular tissue injuries including ACL, meniscus, or cartilage. If this treatment option is established, it can be minimally invasive compared to conventional surgeries for these tissues.

Repair of chronic osteochondral defects in the rat. A bone marrow-stimulating procedure enhanced by cultured allogenic bone marrow mesenchymal stromal cells

Bone marrow mesenchymal stromal cells were aspirated from immature male green fluorescent protein transgenic rats and cultured in a monolayer. Four weeks after the creation of the osteochondral defect, the rats were divided into three groups of 18: the control group, treated with an intra-articular injection of phosphate-buffered saline only; the drilling group, treated with an intra-articular injection of phosphate-buffered saline with a bone marrow-stimulating procedure; and the bone marrow mesenchymal stromal cells group, treated with an intra-articular injection of bone marrow mesenchymal stromal cells plus a bone marrow-stimulating procedure. The rats were then killed at 4, 8 and 12 weeks after treatment and examined. The histological scores were significantly better in the bone marrow mesenchymal stromal cells group than in the control and drilling groups at all time points (p < 0.05). The fluorescence of the green fluorescent protein-positive cells could be observed in specimens four weeks after treatment.

Spontaneous oscillation and mechanically induced calcium waves in chondrocytes

The characteristics of spontaneous calcium (Ca(2+)) oscillation and mechanically induced Ca(2+) waves in articular chondrocytes were studied. In some, but not all, chondrocytes in sliced cartilage and primary cultures, we observed spontaneous oscillation of intracellular Ca(2+) that never spread to adjacent cells. In contrast, a mechanical stimulus to a single cell by touching with a glass rod induced an increase of intracellular Ca(2+) that spread to neighboring cells in a wave-like manner, even though there was no physical contact between the cells. This indicated the release of some paracrine factor from the mechanically stimulated cells. Application of ultrasonic vibration also induced an oscillation of intracellular Ca(2+). The application of a uridine 5'-triphosphate (UTP), UTP, induced a transient increase in intracellular Ca(2+) and the release of adenosine 5'-triphosphate (ATP) in cultured chondrocytes. A P2 receptor antagonist (suramin) and blockers of Cl(-) channels, niflumic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), reduced the UTP-induced ATP release. The results indicated that Cl(-) channels were involved in the extracellular release of ATP following mechanical or P2Y receptor stimulation. Thus, ATP stimulation of P2Y receptors elicits an increase in intracellular Ca(2+), triggering further release of ATP from adjacent cells, thereby expanding the Ca(2+) wave in chondrocytes.

In vivo response of polylactic acid-alginate scaffolds and bone marrow-derived cells for cartilage tissue engineering

Successful application of tissue-engineering techniques to damaged biological structures is determined by functional performance in vivo. This study evaluated the in vivo response of a tissue-engineered construct composed of a polylactic acid-alginate amalgam seeded with bone marrow-derived mesenchymal stem cells and stimulated in vitro with transforming growth factor beta for cartilage tissue engineering. Constructs were placed in cylindrical osteochondral defects in the canine femoral condyle and examined 6 weeks postoperatively by gross, histological, immunohistochemical, and biomechanical analyses. In the course of 6 weeks in vivo, the defects filled with a cartilaginous tissue regardless of whether cell-seeded (experimental) or cell-free (control) constructs were implanted; however, the quality of the tissue differed between the experimental and control defects. Cell-seeded experimental defects showed more cartilage-like matrix quality, cell distribution, and proteoglycan staining. Biomechanically, experimental and control specimens exhibited similar behavior; however, both tissues were still immature compared with normal cartilage. The evidence accumulated in this study showed a modest acceleration of the in vivo healing of cell-seeded constructs but also demonstrated a reparative response of cell-free constructs. This finding suggests that the constructs prepared from the PLA-alginate amalgam may serve as a means for host cell attachment.

Cartilage repair using bone morphogenetic protein 4 and muscle-derived stem cells

OBJECTIVE

Muscle-derived stem cells (MDSCs) isolated from mouse skeletal muscle exhibit long-time proliferation, high self-renewal, and multipotent differentiation. This study was undertaken to investigate the ability of MDSCs that were retrovirally transduced to express bone morphogenetic protein 4 (BMP-4) to differentiate into chondrocytes in vitro and in vivo and enhance articular cartilage repair.

METHODS

Using monolayer and micromass pellet culture systems, we evaluated the in vitro chondrogenic differentiation of LacZ- and BMP-4-transduced MDSCs with or without transforming growth factor beta1 (TGFbeta1) stimulation. We used a nude rat model of a full-thickness articular cartilage defect to assess the duration of LacZ transgene expression and evaluate the ability of transplanted cells to acquire a chondrocytic phenotype. We evaluated cartilage repair macroscopically and histologically 4, 8, 12, and 24 weeks after surgery, and performed histologic grading of the repaired tissues.

RESULTS

BMP-4-expressing MDSCs acquired a chondrocytic phenotype in vitro more effectively than did MDSCs expressing only LacZ; the addition of TGFbeta1 did not alter chondrogenic differentiation of the BMP-4-transduced MDSCs. LacZ expression within the repaired tissue continued for up to 12 weeks. Four weeks after surgery, we detected donor cells that coexpressed beta-galactosidase and type II collagen. Histologic scoring of the defect sites 24 weeks after transplantation revealed significantly better cartilage repair in animals that received BMP-4-transduced MDSCs than in those that received MDSCs expressing only LacZ.

CONCLUSION

Local delivery of BMP-4 by genetically engineered MDSCs enhanced chondrogenesis and significantly improved articular cartilage repair in rats.