Significance Engineered replacements for musculoskeletal tissues generally require extensive ex vivo manipulation of stem cells to achieve controlled differentiation and phenotypic stability. The ability to control cell differentiation using cell-instructive scaffolds that have biomechanical properties approximating those of native tissue would represent a transformative advance in functional tissue engineering. The goal of this study was to develop a bioactive scaffold capable of mediating cell differentiation and formation of an extracellular matrix with the biochemical composition and mechanical features that mimic native tissue properties. By combining innovative gene delivery strategies with advanced biomaterial design, we demonstrate the feasibility of generating constructs capable of restoring biological and mechanical function.
Significance Whereas some success has been realized treating isolated, focal defects or lesions of articular cartilage, the complete resurfacing of synovial joints remains an important challenge for the treatment of osteoarthritis. Here, we develop an anatomically shaped, functional cartilage construct based on a 3D woven scaffold that can provide for total joint resurfacing, with capabilities for tunable and inducible production of anticytokine therapy to protect diseased or injured joints from pathologic inflammation. An important advance of this work is the incorporation of a technique for scaffold-mediated viral gene delivery for overexpression of antiinflammatory molecules within the joint. This approach provides a foundation for total biological cartilage resurfacing to treat end-stage osteoarthritis for young patients, who currently have few therapeutic options.
Cell-based therapies such as tissue engineering provide promising therapeutic possibilities to enhance the repair or regeneration of damaged or diseased tissues but are dependent on the availability and controlled manipulation of appropriate cell sources.The goal of this study was to test the hypothesis that adult subcutaneous fat contains stem cells with multilineage potential and to determine the influence of specific soluble mediators and biomaterial scaffolds on their differentiation into musculoskeletal phenotypes.We reviewed recent studies showing the stem-like characteristics and multipotency of adipose-derived stem cells (ASCs), and their potential application in cell-based therapies in orthopaedics.Under controlled conditions, ASCs show phenotypic characteristics of various cell types, including chondrocytes, osteoblasts, adipocytes, neuronal cells, or muscle cells. In particular, the chondrogenic differentiation of ASCs can be induced by low oxygen tension, growth factors such as bone morphogenetic protein-6 (BMP-6), or biomaterial scaffolds consisting of native tissue matrices derived from cartilage. Finally, focus is given to the development of a functional biomaterial scaffold that can provide ASC-based constructs with mechanical properties similar to native cartilage.Adipose tissue contains an abundant source of multipotent progenitor cells. These cells show cell surface marker profiles and differentiation characteristics that are similar to but distinct from other adult stem cells, such as bone marrow mesenchymal stem cells (MSCs).The availability of an easily accessible and reproducible cell source may greatly facilitate the development of new cell-based therapies for regenerative medicine applications in the musculoskeletal system.
Adult articular cartilage has a limited capacity for growth and regeneration and, with injury, new cellular or biomaterial-based therapeutic platforms are required to promote repair. Tissue engineering aims to produce cartilage-like tissues that recreate the complex mechanical and biological properties found in vivo. In this study, a unique composite scaffold was developed by infiltrating a three-dimensional (3D) woven microfiber poly (ε-caprolactone) (PCL) scaffold with the RAD16-I self-assembling nanofibers to obtain multi-scale functional and biomimetic tissue-engineered constructs. The scaffold was seeded with expanded dedifferentiated human articular chondrocytes and cultured for four weeks in control and chondrogenic growth conditions. The composite constructs were compared to control constructs obtained by culturing cells with 3D woven PCL scaffolds or RAD16-I independently. High viability and homogeneous cell distribution were observed in all three scaffolds used during the term of the culture. Moreover, gene and protein expression profiles revealed that chondrogenic markers were favored in the presence of RAD16-I peptide (PCL/RAD composite or alone) under chondrogenic induction conditions. Further, constructs displayed positive staining for toluidine blue, indicating the presence of synthesized proteoglycans. Finally, mechanical testing showed that constructs containing the PCL scaffold maintained the initial shape and viscoelastic behavior throughout the culture period, while constructs with RAD16-I scaffold alone contracted during culture time into a stiffer and compacted structure. Altogether, these results suggest that this new composite scaffold provides important mechanical requirements for a cartilage replacement, while providing a biomimetic microenvironment to re-establish the chondrogenic phenotype of human expanded articular chondrocytes.
Cite This Article McNulty, A. L., Moutos, F. T., Wilusz, R. E., Weinberg, J. B., Guilak, F. (2006). The Effects of Pro-inflammatory Cytokines on Functional Repair of the Meniscus. Molecular & Cellular Biomechanics, 3(4), 197–198.
Abstract Objective To examine the hypotheses that increasing concentrations of interleukin‐1 (IL‐1) or tumor necrosis factor α (TNFα) inhibit the integrative repair of the knee meniscus in an in vitro model system, and that inhibitors of these cytokines will enhance repair. Methods Explants (8 mm in diameter) were harvested from porcine medial menisci. To simulate a full‐thickness defect, a 4‐mm–diameter core was removed and reinserted. Explants were cultured for 14, 28, or 42 days in the presence of 0–1,000 pg/ml of IL‐1 or TNFα. Explants were also cultured in the presence of IL‐1 or TNFα with IL‐1 receptor antagonist (IL‐1Ra) or TNF monoclonal antibody (mAb). At the end of the culture period, biomechanical testing, cell viability, and histologic analyses were performed to quantify the extent of repair. Results Mechanical testing revealed increased repair strength, cell accumulation, and tissue formation at the interface over time under control conditions. Pathophysiologic concentrations of both IL‐1 and TNFα significantly decreased repair strength, cell migration, and tissue formation at the interface. The addition of IL‐1Ra or TNF mAb to explants prevented the effects of IL‐1 or TNFα, respectively. Conclusion Our findings document that physiologically relevant concentrations of IL‐1 and TNFα inhibit meniscal repair in vitro and therefore may also inhibit meniscal repair during arthritis or following joint injury. The finding that IL‐1Ra and TNF mAb promoted integrative meniscal repair in an inflammatory microenvironment suggests that intraarticular delivery of IL‐1Ra and/or TNF mAb may be useful clinically to promote meniscal healing following injury.
Using high performance textile materials and novel designs, structures were developed which have the potential for mimicking the properties of natural anterior cruciate ligaments (ACLs). Six tubular braided structures capable of withstanding the loads encountered by ACL, were built. Elastomeric materials were incorporated as cores in order to give the devices the ability to recover from strains. Mechanical and viscoelastic properties of the devices were evaluated It was shown that the behavior of the devices at lower (physiological) loads was determined by the core material, while the behavior at high loads was determined by the braided sheath material. A comparison of the properties of the structures with those of the natural ACL showed that the appropriate load bearing, linear modulus and strain hardening behaviors had been realized; however, further work was needed to mimic the extensibility properties.
Tissue engineering remains a promising therapeutic strategy for the repair or regeneration of diseased or damaged tissues. Previous approaches have typically focused on combining cells and bioactive molecules (e.g., growth factors, cytokines and DNA fragments) with a biomaterial scaffold that functions as a template to control the geometry of the newly formed tissue, while facilitating the attachment, proliferation, and differentiation of embedded cells. Biomaterial scaffolds also play a crucial role in determining the functional properties of engineered tissues, including biomechanical characteristics such as inhomogeneity, anisotropy, nonlinearity or viscoelasticity. While single-phase, homogeneous materials have been used extensively to create numerous types of tissue constructs, there continue to be significant challenges in the development of scaffolds that can provide the functional properties of load-bearing tissues such as articular cartilage. In an attempt to create more complex scaffolds that promote the regeneration of functional engineered tissues, composite scaffolds comprising two or more distinct materials have been developed. This paper reviews various studies on the development and testing of composite scaffolds for the tissue engineering of articular cartilage, using techniques such as embedded fibers and textiles for reinforcement, embedded solid structures, multi-layered designs, or three-dimensionally woven composite materials. In many cases, the use of composite scaffolds can provide unique biomechanical and biological properties for the development of functional tissue engineering scaffolds.
The repair of focal cartilage defects remains one of the foremost issues in the field of orthopaedics. Chondral defects may arise from a variety of joint pathologies and left untreated, will likely progress to osteoarthritis. Current repair techniques, such as microfracture, result in short-term clinical improvements but have poor long-term outcomes. Emerging scaffold-based repair strategies have reported superior outcomes compared to microfracture and motivate the development of new biomaterials for this purpose. In this study, unique composite implants consisting of a base porous reinforcing component (woven poly(ε-caprolactone)) infiltrated with 1 of 2 hydrogels (self-assembling peptide or thermo-gelling hyaluronan) or bone marrow aspirate were evaluated. The objective was to evaluate cartilage repair with composite scaffold treatment compared to the current standard of care (microfracture) in a translationally relevant large animal model, the Yucatan minipig. While many cartilage-repair studies have shown some success in vivo, most are short term and not clinically relevant. Informed by promising 6-week findings, a 12-month study was carried out and those results are presented here. To aid in comparisons across platforms, several structural and functionally relevant outcome measures were performed. Despite positive early findings, the long-term results indicated less than optimal structural and mechanical results with respect to cartilage repair, with all treatment groups performing worse than the standard of care. This study is important in that it brings much needed attention to the importance of performing translationally relevant long-term studies in an appropriate animal model when developing new clinical cartilage repair approaches.
