Autogenous Chondrocytes Research Articles

Physiological and histological conditionings of articular cartilage regeneration techniques and clinical application of these techniques

In clinical setting no spectacular treatment results confirmed using histological ap­proaches were noted as compared with these obtained in laboratory research (finding the regeneration built of the hyaline cartilage in the damaged area in the treated patients is very rare since, as a rule the regeneration is built of the fibrous cartilage). Numerous and increasingly frequent procedures aimed at regeneration of the articular cartilage using platelet rich plasma (PRP), isolated autogenous chondrocytes or mesenchymal precursor cells in patients with osteoarthritis provide access to the vast research material for the analysis of the efficacy and safety of the treatment, based on which, no definitely adverse consequences of the applied methods were no­ted, such as life-threatening consequences due to new tissue formation. However, the knowledge of the underlying mechanisms indicates the necessity of exercising caution in qualifying patients for such procedures and many years long monitoring in order to the fastest possible diagnosing and successful treatment of the complications. \

Current treatment concepts for osteochondral lesions of the talus

Osteochondral lesions of the talus (OLT) are a well-known cause of ankle joint pain and can sometimes lead to instability. These lesions are not only confined to articular hyaline cartilage, they can also affect the subchondral bone at the weight-bearing aspect of the talar dome. Nonoperative treatment is the preferred option for small lesions, however surgical intervention is recommended for large lesions or those for which conservative treatment has failed. Microfracture, abrasion arthroplasty and multiple drilling are all classified as bone marrow stimulation procedures; they are used to try to recruit precursor cells for cartilage regeneration and are especially suitable for small OLT lesions. For large lesions, osteochondral autografting and allografting are better options to reconstruct the articular defect, as they have better contours and mechanical strength. When there is limited subchondral bone involvement in large lesions, cell-based therapies such as autogenous chondrocyte implantation, potentially combined with a biomaterial matrix, are a promising option and acceptable functional outcomes have been reported. To provide evidence-based recommendations for clinicians, this article evaluates the currently available treatment strategies for OLT and their evolution over the past few decades.

Decellularized cartilage matrix scaffolds with laser-machined micropores for cartilage regeneration and articular cartilage repair

Decellularized allogeneic and xenogeneic articular cartilage matrix scaffolds (CMS) are considered ideal scaffolds for cartilage regeneration owing to their heterogeneous architecture, and biochemical and biomechanical properties of native articular cartilage. However, the dense structure of the articular cartilage extracellular matrix, particularly the arrangement of collagen fibers, limits cellular infiltration, leading to poor cartilage regeneration. In addition, the incomplete removal of xenograft cells is associated with immunogenic reaction in the host. To facilitate the migration of chondrocytes into scaffolds and the rate of decellularization processing, we applied a carbon dioxide laser technique to modify the surface of porcine CMS while retaining major properties of the scaffold. By optimizing the laser parameters, we introduced orderly, lattice-arranged conical micropores of suitable depth and diameter onto the cartilage scaffold surface without affecting the cartilage shape or mechanical properties. We found that laser-modified CMS (LM-CMS) could enhance the degree of decellularization and were conducive to cell adhesion, as compared with the intact CMS. Decellularized scaffolds were seeded with rabbit-derived chondrocytes and cultured for 8 weeks in vitro. We found that cell-scaffold constructs formed cartilage-like tissue within the micropores and on the scaffold surface. In vivo, we found that cell-scaffold constructs subcutaneously implanted into the flanks of nude mice formed ivory-white neocartilage with high contents of DNA and cartilage matrix components, as well as good mechanical strength as compared with native CMS. Furthermore, scaffolds combined with autogenous chondrocytes induced neocartilage and better structural restoration at 8 weeks after transplantation into rabbit knee articular cartilage defects. In conclusion, decellularized xenogeneic CMS with laser-machined micropores offers an ideal scaffold with high fidelity for the functional reconstruction of articular cartilage.

Management of Osteochondral Lesions of the Talar Dome

Osteochondral lesion of the talus (OLT) is a common condition associated with ankle injury that brings challenges in the diagnosis and treatment. Symptoms related to this condition are nonspecific including pain, swelling, stiffness, and mechanical symptoms of locking and catching. While the natural history of the OLTs is not well understood, surgical treatment is often required especially in chronic cases and acute cases with displaced articular fragments. Arthroscopic treatment of the OLTs aims to restore ankle joint function and pain relief by the removal of the chondral or osteochondral fragment, debridement and stabilization of cartilage rim and subchondral bone, and stimulate healing of the bone and damaged cartilage. In patients with a large lesion or after a failure of previous bone marrow stimulation, biologic restoration techniques including the use of particulate juvenile cartilage techniques, autogenous chondrocyte implantation, and osteochondral autograft or allograft transplantation may have role. This article summarizes the contemporary concepts in the clinical evaluation and treatment of OLTs with particular emphasis on surgical strategies.

An Autologous Tissue Implant, NeoCart, for Treatment of Hyaline Cartilage Injury in the Knee

NeoCart is an autologous cartilage tissue–engineered implant designed for use in repair of articular cartilage injuries. It uniquely combines a type I bovine-derived collagen scaffold with autogenous chondrocytes and bioreactor treatment. It is currently in the third phase of an investigational study in the United States for treatment of symptomatic articular cartilage lesions of the distal femur. This multicenter, prospective, randomized controlled trial directly compares changes of multiple patient-reported outcome measures over 3 years with a control group undergoing microfracture surgery. This article describes the study design and indications for enrollment in the phase III trial. The technical elements of NeoCart culture and production process, surgical implantation procedure, and rehabilitation guidelines are outlined. In addition, we review previously published findings from the completed phase I safety and phase II exploratory trials.

Evaluation of nanofiber-based polyglycolic acid scaffolds for improved chondrocyte retention and in vivo bioengineered cartilage regeneration.

In conventional studies on the regeneration of auricle-shaped cartilage in autogenous models using large animals, there were problems with the cartilage regeneration induction capacity and long-term retention of geometric shape. In this study, the authors sought to improve on outcome in these regards: a nonwoven fabric of polyglycolic acid was developed through nanotechnology, and the effect of nanofiber diameter on in vitro cell-seeding efficiency and the in vivo response after implantation in an autogenous large-animal model were evaluated. Canine chondrocytes were isolated and seeded onto polyglycolic acid fabric ranging from 0.5 to 20 μm in average diameter. Cell seeding efficiency was highest for mid-range polyglycolic acid fibers (average diameter, 0.8, 3.0, and 7.0 μm). Flat and auricle-shaped scaffolds were constructed using polypropylene structural support, sandwiching a nonwoven polyglycolic acid fabric that contained autogenous chondrocytes together with basic fibroblast growth factor-laden particles and an exterior fibrin sealant. Scaffolds were then implanted autogenously and evaluated at 5 and 20 weeks. Biomechanical strength was optimal for polyglycolic acid fiber diameters of 0.8 to 3.0 μm. Optimal cell maintenance and neocartilage response were seen with polyglycolic acid fiber diameters in the same mid-range for nanofiber constructs. These findings demonstrate the potential for nanoscale modulation of auricle-shaped cartilage regeneration in a large-animal model.

Paper 269: Fresh Osteochondral Allograft Transplantation for Large Sectoral Defects of the Femoral Condyles

Background & AimsThe treatment of large osteochondral defects of the femoral condyles can be challenging. The conventional surgical options including drilling, microfracture revascularisation, mosaicplasty, and autogenous chondrocyte implantation are often inadequate since they cannot 3-dimensionally reconstruct the structural topography of large and deep sectoral defects of the femoral condyles. Although tissue-bank procured osteochondral allografts are an attractive option, scarce availability has resulted in limited use. This prospective study aims to determine the outcomes of live donor procured fresh osteochondral transplants for large sectoral defects of the femoral condyles.

NeoCart, an Autologous Cartilage Tissue Implant, Compared with Microfracture for Treatment of Distal Femoral Cartilage Lesions

Despite introduction of autologous chondrocyte therapy for repair of hyaline articular cartilage injury in 1994, microfracture remains a primary standard of care. NeoCart, an autologous cartilage tissue implant, was compared with microfracture in a multisite prospective, randomized trial of a tissue-engineered bioimplant for treating articular cartilage injuries in the knee. Thirty patients were randomized at a ratio of two to one (two were treated with an autologous cartilage tissue implant [NeoCart] for each patient treated with microfracture) at the time of arthroscopic confirmation of an International Cartilage Repair Society (ICRS) grade-III lesion(s). Microfracture or cartilage biopsy was performed. NeoCart, produced by seeding a type-I collagen matrix scaffold with autogenous chondrocytes and bioreactor treatment, was implanted six weeks following arthroscopic cartilage biopsy. Standard evaluations were performed with validated clinical outcomes measures. Three, six, twelve, and twenty-four-month data are reported. The mean duration of follow-up (and standard deviation) was 26 ± 2 months. There were twenty-one patients in the NeoCart group and nine in the microfracture group. The mean age (40 ± 9 years), body mass index (BMI) (28 ± 4 kg/m2), duration between the first symptoms and treatment (3 ± 5 years), and lesion size (287 ± 138 mm2 in the NeoCart group and 252 ± 135 mm2 in the microfracture group) were similar between the groups. Adverse event rates per procedure did not differ between the treatment arms. The scores on the Short Form-36 (SF-36), Knee Injury and Osteoarthritis Outcome Score (KOOS) activities of daily living (ADL) scale, and International Knee Documentation Committee (IKDC) form improved from baseline (p < 0.05) to two years postoperatively in both treatment groups. In the NeoCart group, improvement, compared with baseline, was significant (p < 0.05) for all measures at six, twelve, and twenty-four months. Improvement in the NeoCart group was significantly greater (p < 0.05) than that in the microfracture group for the KOOS pain score at six, twelve, and twenty-four months; the KOOS symptom score at six months; the IKDC, KOOS sports, and visual analog scale (VAS) pain scores at twelve and twenty-four months; and the KOOS quality of life (QOL) score at twenty-four months. Analysis of covariance (ANCOVA) at one year indicated that the change in the KOOS pain (p = 0.016) and IKDC (p = 0.028) scores from pretreatment levels favored the NeoCart group. Significantly more NeoCart-treated patients (p = 0.0125) had responded to therapy (were therapeutic responders) at six months (43% versus 25% in the microfracture group) and twelve months (76% versus 22% in the microfracture group). This trend continued, as the proportion of NeoCart-treated patients (fifteen of nineteen) who were therapeutic responders at twenty-four months was greater than the proportion of microfracture-treated participants (four of nine) who were therapeutic responders at that time. This randomized study suggests that the safety of autologous cartilage tissue implantation, with use of the NeoCart technique, is similar to that of microfracture surgery and is associated with greater clinical efficacy at two years after treatment.

A highly organized three-dimensional alginate scaffold for cartilage tissue engineering prepared by microfluidic technology

Osteoarthritis is a degenerative disease and frequently involves the knee, hip and phalangeal joints. Current treatments used in small cartilage defects including multiple drilling, abrasion arthroplasty, mosaicplasty, and autogenous chondrocyte transplantation, however, there are problems needed to be solved. The standard treatment for severe osteoarthritis is total joint arthroplasty. The disadvantages of this surgery are the possibility of implant loosening. Therefore, tissue engineering for cartilage regeneration has become a promising topic. We have developed a new method to produce a highly organized single polymer (alginate) scaffold using microfluidic device. Scanning electron microscope and confocal fluoroscope examinations showed that the scaffold has a regular interconnected porous structure in the scale of 250 μm and high porosity. The scaffold is effective in chondrocyte culture; the cell viability test (WST-1 assay), cell toxicity (lactate dehydrogenase assay), cell survival rate, extracellular matrix production (glycosaminoglycans contents), cell proliferation (DNA quantification), and gene expression (real-time PCR) all revealed good results for chondrocyte culture. The chondrocytes can maintain normal phenotypes, highly express aggrecan and type II collagen, and secrete a great deal of extracellular matrix when seeded in the alginate scaffold. This study demonstrated that a highly organized alginate scaffold can be prepared with an economical microfluidic device, and this scaffold is effective in cartilage tissue engineering.

Treatment of an Articular Lesion of the Lateral Tibial Plateau Utilizing a Tibial “Drawer-Exposure” Osteotomy and Osteochondral Allograft Transplant

Articular cartilage lesions of the knee are recognized and treated frequently1. Despite evolving techniques, treatment of cartilage lesions in the knee remains a therapeutic challenge2. The nonoperative management of chondral injuries in young patients is often unsatisfactory for the patient and the surgeon3. Surgical options, such as microfracture, autogenous chondrocyte implantation, resurfacing techniques, and osteochondral allograft transplantation have been developed to treat cartilage defects; however, there is little Level-I or Level-II evidence to inform the decision-making process regarding the various surgical options2,3. Treating cartilage defects of the tibial plateau presents a unique challenge because the tibial plateau is partially obscured by the menisci and the distal part of the femur throughout all knee motion, with resultant difficulty in orthogonal access with instrumentation. Few reports exist on the treatment of tibial plateau chondral injuries with osteochondral grafting4,5. This case report presents a novel technique to treat a cartilage defect of the tibial plateau with use of a “drawer-exposure” osteotomy of the tibial plateau combined with fresh-frozen osteochondral allograft for treatment of an osteonecrotic lesion. The patient and her family were informed that data from this case would be submitted for publication, and they consented. The patient was a thirteen-year-old girl with juvenile rheumatoid arthritis who had a history of chronic prednisone treatment in excess of 60 mg per day, but who at presentation had been managed with Enbrel (etanercept), methotrexate, and Mobic (meloxicam). The patient had multiple concomitant polyarthropathies, predominantly involving the knees and the ankles, and had undergone two previous arthroscopic debridements for osteonecrosis of the left talus. In October 2007, the patient presented to a pediatric hospital with intractable right knee pain, swelling, and difficulty with walking, all of which worsened with activity and improved …

Sport und Bewegung bei Schulter- und Kniegelenksarthrose – Disziplinen, Dosierung und therapeutische Wirkung

Arthroses may be of concrete origin or may occur idiopathically without any identifiable risk factors. If an arthrosis is identified by clinical and radiological signs, the patient must suitably adapt his sports activities. The aim must be to slow down the progression of the disorder. Impulsive and rotatory movements should be avoided as a matter of principle. Sports involving contacts must also be avoided, since they include rapid movements and an increased risk of injury. Sports should rather be in accordance wirh an extended physiotherapy. We recommend cycling, swimming, walking and classical long-distance running, improvng the mobility as well as good muscular guidance of the involved joints. If all the conservative therapeutic options have been exhausted, we may employ surgical options such as arthroscopic treatment of joints. In case of angulatory deformities, these may be surgically corrected. Young patients may be subjected to autogenous chondrocyte transplantation (ACT) with chondrocytes being removed and re-cultivated in the laboratory.

Traumatic Osteochondral Injury of the Femoral Head Treated by Mosaicplasty: A Report of Two Cases

The increased risk of symptomatic progression towards osteoarthritis after chondral damage has led to the development of multiple treatment options for cartilage repair. These procedures have evolved from arthroscopic lavage and debridement, to marrow stimulation techniques, and more recently, to osteochondral autograft and allograft transplants, and autogenous chondrocyte implantation. The success of mosaicplasty procedures in the knee has led to its application to other surfaces, including the talus, tibial plateau, patella, and humeral capitellum. In this report, we present two cases of a chondral defect to the femoral head after a traumatic hip dislocation, treated with an osteochondral autograft (OATS) from the ipsilateral knee, and the inferior femoral head, respectively, combined with a surgical dislocation of the hip. At greater than 1year and greater than 5years of follow-up, MRI studies have demonstrated good autograft incorporation with maintenance of articular surface conformity, and both patients clinically continue to have no pain and full active range of motion of their respective hips. In our opinion, treatment of osteochondral defects in the femoral head surface using a surgical dislocation combined with an OATS procedure is a promising approach, as full exposure of the femoral head can be obtained while preserving its vasculature, thus enabling adequate restoration of the articular cartilage surface.

An Autologous Cartilage Tissue Implant NeoCart for Treatment of Grade III Chondral Injury to the Distal Femur

Background The healing potential of damaged articular cartilage is limited. The NeoCart is a tissue-engineered collagen matrix seeded with autogenous chondrocytes designed for the repair of hyaline articular cartilage. Hypothesis The NeoCart implant is well tolerated in the human knee. Study Design Case series; Level of evidence, 4. Methods Eight patients (treatment group) with full-thickness cartilage injury were treated with the NeoCart and evaluated prospectively. Autogenous chondrocytes provided by arthroscopic biopsy were seeded into a 3-dimensional type I collagen scaffold. The seeded scaffold was subjected to a tissue-engineering protocol including treatment with a bioreactor. Implantation of the prepared cartilage tissue patch was performed via miniarthrotomy and secured with a collagen bioadhesive. Evaluations through 24 months postoperatively included the subjective International Knee Documentation Committee questionnaire, visual analog scale, range of motion, and cartilage-sensitive magnetic resonance imaging (MRI), including quantitative T2 mapping. Results Pain scores after NeoCart implantation were significantly lower than baseline at 12 and 24 months after the procedure (P < .05). Improved function and motion were also noted at 24 months. Six patients had 67% to 100% defect fill at 24 months with MRI evaluation. One patient had moderate (33%-66%) defect fill, and another patient had poor (less than 33%) defect fill. Partial stratification of T2 values was observed for 2 patients at 12 months and 4 patients at 24 months. No patients experienced arthrofibrosis or implant hypertrophy. Conclusion Pain was significantly reduced 12 and 24 months after NeoCart treatment. Trends toward improved function and motion were observed 24 months after implantation. The MRI indicated implant stability and peripheral integration, defect fill without overgrowth, progressive maturation, and more organized cartilage formation.

Microporous biodegradable polyurethane membranes for tissue engineering

Microporous membranes with controlled pore size and structure were produced from biodegradable polyurethane based on aliphatic diisocyanate, poly(epsilon-caprolactone) diol and isosorbide chain extender using the modified phase-inversion technique. The following parameters affecting the process of membrane formation were investigated: the type of solvent, solvent-nonsolvent ratio, polymer concentration in solution, polymer solidification time, and the thickness of the polymer solution layer cast on a substrate. The experimental systems evaluated were polymer-N,N-dimethylformamide-water, polymer-N,N-dimethylacetamide-water and polymer-dimethylsulfoxide-water. From all three systems evaluated the best results were obtained for the system polymer-N,N-dimethylformamide-water. The optimal conditions for the preparation of microporous polyurethane membranes were: polymer concentration in solution 5% (w/v), the amount of nonsolvent 10% (v/v), the cast temperature 23 degrees C, and polymer solidification time in the range of 24-48 h depending on the thickness of the cast polymer solution layer. Membranes obtained under these conditions had interconnected pores, well defined pore size and structure, good water permeability and satisfactory mechanical properties to allow for suturing. Potential applications of these membranes are skin wound cover and, in combination with autogenous chondrocytes, as an "artificial periosteum" in the treatment of articular cartilage defects.

Chondrogenesis From Immortalized Human Mesenchymal Stem Cells: Comparison Between Collagen Gel and Pellet Culture Methods

Human mesenchymal stem cells (hMSCs) can differentiate into cells of connective tissue lineages, including cartilage. To overcome the limiting autogenous chondrocyte populations available in cartilage repair, various methods have been developed to maximize chondrogenesis of hMSCs in vitro, most of which use cells derived from primary culture. In this study, we compared chondrogenesis of immortalized hMSCs embedded in collagen gel to those grown in pellet culture. The hMSCs in collagen scaffolds expressed more glycosaminoglycan than those in pellet culture. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis demonstrated that the expression of genes encoding sox-9, aggrecan, and types I and II collagen increased in pellet culture over time. However, in the collagen cultures, only type II collagen and aggrecan expression increased over time, whereas sox-9 expression remained unchanged and type I collagen expression decreased. These results indicate that the immortalized hMSC line is a promising tool for further in vitro chondrogenic studies.

Injectable Tissue-Engineered Cartilage Using a Fibrin Sealant

To investigate a commercially available fibrin sealant as a vehicle for developing injectable tissue-engineered cartilage. Fibrin glue was mixed with autogenous chondrocytes from rabbits (n = 15). This isolate was injected along their nasal dorsa using 1 of 3 different fibrin glue concentrations. The samples were harvested at 8 weeks and compared with elastin and hyaline cartilage controls. Neocartilage was created along a linear injection tract on the dorsa of the nasal bones in 5 of 15 rabbits. Higher thrombin concentrations proved to be directly correlated with successful creation of injectable cartilage. Histologically, the staining patterns of both hematoxylin-eosin and safranin O stains were identical to that of normal auricular control cartilage. The presence of elastin fibers was observed following Verhoeff staining. No foreign body reaction was observed from the host. This study demonstrated a successful method for percutaneous injection of tissue-engineered cartilage as a mixture of chondrocytes suspended in fibrin glue. The thrombin concentration, along with the concentration of fibrinogen and chondrocytes, must be optimized to succeed consistently in cartilage growth.

In vitro engineering of cartilage: effects of serum substitutes, TGF‐β, and IL‐1α

Cartilage is avascular and relatively homogeneous, making it an attractive tissue for in vitro histogenesis and surgical use in patients. We developed novel platform technologies in order to define the requirements for optimal in vitro chondrogenesis by isolated cells. In this series of studies, we tested alternatives to fetal bovine serum (FBS) and the effects of growth factors on formation of cartilage in 3D porous collagen sponges. We used porous collagen sponges to assess the effects of serum substitutes and exogenous TGF-beta1 and IL-1alpha on chondrocytes (bovine articular chondrocytes, bACs) and on chondroinduced human dermal fibroblasts (hDFs). We determined the effects of low concentrations of FBS and two serum substitutes, Nutridoma and ITS(+3), on cellularity and matrix production. After culture for intervals, sponges were harvested for histological and biochemical measurement of cartilage-specific chondroitin 4-sulfate proteoglycan (C 4-S PG). Cultured bACs showed equivalent growth in Nutridoma (1%) and 10% FBS. Both TGF-beta1 and IL-1alpha significantly stimulated accumulation of C 4-S PG by bACs in 3D porous collagen sponges. Many endogenous growth factors were upregulated in hDFs cultured with chondroinductive DBP. Addition of TGF-beta1 and IL-1alpha for 11 days significantly stimulated accumulation of C 4-S PG by hDFs cultured in DMEM with 1% Nutridoma. Porous collagen sponges are supportive of chondrogenesis and of chondroinduction by DBP. Optimization of serum-free culture conditions, including growth factors, matrix components, and mechanical stimuli will expedite translation to wider clinical applications. Use of autogenous dermal fibroblasts pre-cultured with DBP and induced to chondrocytes offers an alternative to autogenous chondrocytes.

Magnetic Resonance Imaging of Remaining Physis in Partial Physeal Resection With Graft Interposition in a Rabbit Model

The purpose of this study was to evaluate the effect of graft interposition into a physeal defect on the remaining physis. Bilateral partial physeal defects were made in the medial half of the proximal tibiae of 8-week-old New Zealand white rabbits (n=25). Biologic material (autogenous chondrocytes derived from perichondrial cells incorporated into beads) was implanted in the left-sided physeal defect, and right-sided untreated tibial defects were used as controls. Magnetic resonance (MR) imaging was obtained at 2, 4, 8, 12, and 16 weeks after operation using a 1.5-tesla MR unit. T1WI, T2WI, and gradient-recalled echo (GRE) images were obtained in the coronal plane. The MR features of physeal defects and of remaining physes were compared between grafted tibiae and controls, as were histologic results and the heights of the remaining physes. Histologically, cartilage clusters were detected in the 17 cases of grafted tibiae (68%), whereas a bone bridge was observed in all controls. The cartilage clusters showed high signal intensity on both T2WI and GRE and low signal intensity on T1WI at 2 weeks postoperatively, and became low signal intensity on T2WI at 8 weeks. On GRE images, high signal intensities of the remaining physes disappeared earlier in the control tibiae than in the grafted tibiae. The remaining physes of control tibiae showed altered histologic configurations and a progressive decrease in physis height. Quantitative measurements of the height of the remaining growth plates showed a significant difference between grafted tibiae and controls (P <0.001). Graft interposition into a partial physeal defect may prevent early closure of the remaining physis and bone bridge formation. MR imaging can depict alterations of remaining physes that lead to early closure of the physis.

Biomaterials in cartilage and bone tissue engineering

Purpose of review: Advances in cartilage tissue engineering have set the stage for further work on bone and joint engineering, although significant hurdles need to be overcome for clinical applications. Recent findings: The main themes in recent research on cartilage and bone tissue engineering include novel scaffolds for cell-free or cell-based approaches, the sources of the cells for neocartilage or new bone, and the potential enhancing effects of factors and mechanical signals before transplantation. Summary: There has been a decade of experience with the use of suspensions of autogenous chondrocytes after expansion in vitro for the treatment of focal cartilage defects. There is even longer experience with percutaneous injections of autogenous marrow for treatment of nonunion of bone fractures. The goals for future clinical practice include the design of cell-free materials that stimulate tissue regeneration where needed, minimally invasive collection of stem cells/progenitors/precursors of chondrocytes or osteoblasts, efficient delivery of cells or engineered tissue, optimization of tissue formation in vitro by adding factors or mechanical stimuli, enhancement of the integration of engineered tissue with the recipient bed, and revascularization and growth of the engineered constructs.

Tissue engineering of a human sized and shaped auricle using a mold.

The creation of a tissue-engineered auricle was initially successful in an immunocompromised nude mouse model. Subsequently, an immunocompetent porcine model successfully generated a helical construct. We wished to evaluate the novel technique of using a mold to create a complete, anatomically refined auricle in a large animal model. Mixtures of autogenous chondrocytes and biodegradable polymers were used inside a perforated, auricle shaped hollow gold mold. Three biodegradable polymers (calcium alginate, pluronic F-127, and polyglycolic acid) were used to retain the seeded chondrocytes inside the mold. These molds, along with a control, were implanted subcutaneously in the abdominal area of 10 animals (pigs and sheep). The constructs were removed after 8 to 20 weeks and were assessed by gross morphology and histology. All the gold implants were well tolerated by the animals. The implants using calcium alginate (n = 3) generated constructs of the exact shape and size of a normal human ear; the histology demonstrated mostly normal cartilage with some persistent alginate. The implants with pluronic F-127 (n = 3) resulted in cartilage with essentially normal histology, although leakage outside the molds and external cartilage generation was noted. Polyglycolic acid implants (n = 3) produced no useful cartilage because of an inflammatory reaction with fibrosis. The empty control mold (n = 1) demonstrated only a very small amount of fibrous tissue inside. A tissue-engineered human sized auricle of normal anatomic definition can be generated in an immunocompetent large-animal model using a mold technique. Although further refinements will be necessary, the technique appears promising for potential use in patients with microtia.