Development of bone and cartilage in tissue-engineered human middle phalanx models

Tissue engineering: from the bedside to the bench and back to the bedside

The field of Tissue Engineering and Regenerative Medicine has evolved rapidly over the past thirty years. This review will summarize its history, current status and direction through the lens of clinical need, its progress through science in the laboratory and application back into patients. We can take pride in the fact that much effort and progress began with the surgical problems of children and that many surgeons in the pediatric surgical specialties have become pioneers and investigators in this new field of science, engineering, and medicine. Although the field has yet to fulfill its great promise, there have been several examples where a therapy has progressed from the first idea to human application within a short span of time and, in many cases, it has been applied in the surgical care of children.

Characterization of Tissue-Engineered Human Periosteum and Allograft Bone Constructs: The Potential of Periosteum in Bone Regenerative Medicine

Delayed-union or non-union between a host bone and a graft is problematic in clinical treatment of segmental bone defects in orthopedic cases. Based on a preliminary study of human periosteum allografts from this laboratory, the present work has extensively investigated the use of human cadaveric tissue-engineered periosteum-allograft constructs as an approach to healing such serious orthopedic surgical situations. In this current report, human cadaveric periosteum-wrapped bone allografts and counterpart controls without periosteum were implanted subcutaneously in athymic mice (nu/nu) for 10, 20, and, for the first time, 40 weeks. Specimens were then harvested and assessed by histological and gene expression analyses. Compared to controls, the presence of new bone formation and resorption in periosteum-allograft constructs was indicated in both histology and gene expression results over 40 weeks of implantation. Of several genes also examined for the first time, RANKL and SOST expression levels increased in a statistically significant manner, data suggesting that bone formation and the presence of increasing numbers of osteocytes in bone matrices had increased with time. The tissue-engineering strategy described in this study provides a possible means of improving delayed-union or non-union at the healing sites of segmental bone defects or bone fractures. The potential of periosteum and its resident cells could thereby be utilized effectively in tissue-engineering methods and tissue regenerative medicine.

A Method for the Immunohistochemical Identification and Localization of Osterix in Periosteum-Wrapped Constructs for Tissue Engineering of Bone

A novel immunohistochemistry (IHC) approach has been developed to label and localize osterix, a bone-specific transcription factor, within formalin-fixed, paraffin-embedded, tissue-engineered constructs uniquely containing synthetic polymers and human periosteal tissue. Generally, such specimens consisting in part of polymeric materials and mineral are particularly difficult for IHC identification of proteins. Samples here were fabricated from human periosteum, electrospun poly-l-lactic acid (PLLA) nanofibers, and polycaprolactone/poly-l-lactic acid (PCL/PLLA, 75/25) scaffolds and harvested following 10 weeks of implantation in athymic mice. Heat-induced and protease-induced epitope retrieval methods from selected existing protocols were examined to identify osterix. All such protease-induced techniques were unsuccessful. Heat-induced retrieval gave positive results for osterix immunohistochemical staining in sodium citrate/EDTA/Tween 20 with high heat (120C) and pressure (~30 psi) for 10 min, but the heat and pressure levels resulted in tissue damage and section delamination from slides that limited protocol effectiveness. Heat-induced epitope retrieval led to other osterix-positive staining results achieved with minimal impact on structural integrity of the tissue and polymers in sodium citrate/EDTA/Tween 20 buffer at 60C and normal pressure (14.5 psi) for 72 hr. The latter approach identified osterix-positive cells by IHC within periosteal tissue, layers of electrospun PLLA nanofibers, and underlying PCL/PLLA scaffolds of the tissue-engineered constructs.

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.

Tissue engineering a human phalanx

A principal purpose of tissue engineering is the augmentation, repair or replacement of diseased or injured human tissue. This study was undertaken to determine whether human biopsies as a cell source could be utilized for successful engineering of human phalanges consisting of both bone and cartilage. This paper reports the use of cadaveric human chondrocytes and periosteum as a model for the development of phalanx constructs. Two factors, osteogenic protein-1 [OP-1/bone morphogenetic protein-7 (BMP7)], alone or combined with insulin-like growth factor (IGF-1), were examined for their potential enhancement of chondrocytes and their secreted extracellular matrices. Design of the study included culture of chondrocytes and periosteum on biodegradable polyglycolic acid (PGA) and poly-l-lactic acid (PLLA)-poly-ε-caprolactone (PCL) scaffolds and subsequent implantation in athymic nu/nu (nude) mice for 5, 20, 40 and 60 weeks. Engineered constructs retrieved from mice were characterized with regard to genotype and phenotype as a function of developmental (implantation) time. Assessments included gross observation, X-ray radiography or microcomputed tomography, histology and gene expression. The resulting data showed that human cell-scaffold constructs could be successfully developed over 60 weeks, despite variability in donor age. Cartilage formation of the distal phalanx models enhanced with both OP-1 and IGF-1 yielded more cells and extracellular matrix (collagen and proteoglycans) than control chondrocytes without added factors. Summary data demonstrated that human distal phalanx models utilizing cadaveric chondrocytes and periosteum were successfully fabricated and OP-1 and OP-1/IGF-1 accelerated construct development and mineralization. The results suggest that similar engineering and transplantation of human autologous tissues in patients are clinically feasible. Copyright © 2016 John Wiley & Sons, Ltd.

Coefficient of Friction Patterns Can Identify Damage in Native and Engineered Cartilage Subjected to Frictional-Shear Stress

The mechanical loading environment encountered by articular cartilage in situ makes frictional-shear testing an invaluable technique for assessing engineered cartilage. Despite the important information that is gained from this testing, it remains under-utilized, especially for determining damage behavior. Currently, extensive visual inspection is required to assess damage; this is cumbersome and subjective. Tools to simplify, automate, and remove subjectivity from the analysis may increase the accessibility and usefulness of frictional-shear testing as an evaluation method. The objective of this study was to determine if the friction signal could be used to detect damage that occurred during the testing. This study proceeded in two phases: first, a simplified model of biphasic lubrication that does not require knowledge of interstitial fluid pressure was developed. In the second phase, frictional-shear tests were performed on 74 cartilage samples, and the simplified model was used to extract characteristic features from the friction signals. Using support vector machine classifiers, the extracted features were able to detect damage with a median accuracy of approximately 90%. The accuracy remained high even in samples with minimal damage. In conclusion, the friction signal acquired during frictional-shear testing can be used to detect resultant damage to a high level of accuracy.

Methods for producing scaffold-free engineered cartilage sheets from auricular and articular chondrocyte cell sources and attachment to porous tantalum

Scaffold-free cartilage engineering techniques may provide a simple alternative to traditional methods employing scaffolds. We previously reported auricular chondrocyte-derived constructs for use in an engineered trachea model; however, the construct generation methods were not reported in detail. In this study, methods for cartilage construct generation from auricular and articular cell sources are described in detail, and the resulting constructs are compared for use in a joint resurfacing model. Attachment of cartilage sheets to porous tantalum is also investigated as a potential vehicle for future attachment to subchondral bone. Large scaffold-free cartilage constructs were produced from culture-expanded chondrocytes from skeletally mature rabbits, and redifferentiated in a chemically-defined culture medium. Auricular constructs contained more glycosaminoglycan (39.6±12.7 vs. 9.7±1.9 μg/mg wet weight, mean and standard deviation) and collagen (2.7±0.45 vs. 1.1±0.2 μg/mg wet weight, mean and standard deviation) than articular constructs. Aggregate modulus was also higher for auricular constructs vs. articular constructs (0.23±0.07 vs. 0.12±0.03 MPa, mean and standard deviation). Attachment of constructs to porous tantalum was achieved by neocartilage ingrowth into tantalum pores. These results demonstrate that large scaffold-free neocartilage constructs can be produced from mature culture-expanded chondrocytes in a chemically-defined medium, and that these constructs can be attached to porous tantalum.

The nature and role of periosteum in bone and cartilage regeneration

This study was undertaken to determine whether periosteum from different bone sources in a donor results in the same formation of bone and cartilage. In this case, periosteum obtained from the cranium and mandible (examples of tissue supporting intramembranous ossification) and the radius and ilium (examples of tissues supporting endochondral ossification) of individual calves was used to produce tissue-engineered constructs that were implanted in nude mice and then retrieved after 10 and 20 weeks. Specimens were compared in terms of their osteogenic and chondrogenic potential by radiography, histology, and gene expression levels. By 10 weeks of implantation and more so by 20 weeks, constructs with cranial periosteum had developed to the greatest extent, followed in order by ilium, radius, and mandible periosteum. All constructs, particularly with cranial tissue although minimally with mandibular periosteum, had mineralized by 10 weeks on radiography and stained for proteoglycans with safranin-O red (cranial tissue most intensely and mandibular tissue least intensely). Gene expression of type I collagen, type II collagen, runx2, and bone sialoprotein (BSP) was detectable on QRT-PCR for all specimens at 10 and 20 weeks. By 20 weeks, the relative gene levels were: type I collagen, ilium >> radial ≥ cranial ≥ mandibular; type II collagen, radial > ilium > cranial ≥ mandibular; runx2, cranial >>> radial > mandibular ≥ ilium; and BSP, ilium ≥ radial > cranial > mandibular. These data demonstrate that the osteogenic and chondrogenic capacity of the various constructs is not identical and depends on the periosteal source regardless of intramembranous or endochondral ossification. Based on these results, cranial and mandibular periosteal tissues appear to enhance bone formation most and least prominently, respectively. The appropriate periosteal choice for bone and cartilage tissue engineering and regeneration should be a function of its immediate application as well as other factors besides growth rate.