Abstract
Background
The scapholunate interosseous ligament (SLIL) has three subregions: dorsal, proximal, and volar. The SLIL enthesis has not previously been studied despite its important ...mechanical function in wrist joint biomechanics.
Questions/Purposes
This study aims to compare the histomorphological differences between the SLIL subregions, including at their entheses. Three questions are explored: Do the gross dimensions differ between SLIL subregions? Does the enthesis qualitatively, and its calcified fibrocartilage (CF) quantitatively, differ between (a) SLIL subregions and (b) scaphoid and lunate attachments?
Methods
Twelve fresh-frozen human cadaveric wrists were dissected and the gross dimensions of the SLIL subregions measured. Subregions were histologically processed for morphological and compositional analyses, including quantification of enthesis CF area.
Results
The dorsal subregion was the thickest. The dorsal and volar subregions had fibrocartilaginous entheses, while the proximal subregion was attached to articular cartilage. The dorsal subregion had significantly more CF than the volar subregion. There was no significant difference in the enthesis CF between scaphoid and lunate attachments in the three subregions.
Conclusions
There are significant morphological differences between the SLIL subregions. The dorsal subregion has the largest amount of CF, which is consistent with the greater biomechanical force subjected to this subregion. The similar histomorphology of the ligament at the scaphoid and lunate entheses suggests that similar biomechanical forces are applied to both attachments.
Clinical Relevance
The histomorphological results confirm that the dorsal subregion is the strongest of the three subregions. The results from the entheseal region may have important implications in the study of graft incorporation during SLIL reconstruction.
Imaging the hard/soft tissue interface Bannerman, Alistair; Paxton, Jennifer Z; Grover, Liam M
Biotechnology letters,
03/2014, Volume:
36, Issue:
3
Journal Article
Peer reviewed
Interfaces between different tissues play an essential role in the biomechanics of native tissues and their recapitulation is now recognized as critical to function. As a consequence, imaging the ...hard/soft tissue interface has become increasingly important in the area of tissue engineering. Particularly as several biotechnology based products have made it onto the market or are close to human trials and an understanding of their function and development is essential. A range of imaging modalities have been developed that allow a wealth of information on the morphological and physical properties of samples to be obtained non-destructively in vivo or via destructive means. This review summarizes the use of a selection of imaging modalities on interfaces to date considering the strengths and weaknesses of each. We will also consider techniques which have not yet been utilized to their full potential or are likely to play a role in future work in the area.
Progress in tissue engineering is now impacting beyond the field of regenerative medicine. Engineered tissues are now used as tools to evaluate the toxicity of compounds or even to enable the ...modelling of disease. While many of the materials that are used to facilitate tissue growth are designed to enable cell attachment, many researchers consider that the contraction and modification of these matrices by attached cells is not desirable and take measures to prevent this from occurring. Where substantial alignment of the molecules within tissues, however, is a feature of structure the process of contraction can be exploited to guide new matrix deposition. In this paper, we will demonstrate how we have used the cell contraction process to generate tissues with high levels of organization. The tissues that have been grown in the laboratory have been characterized using a suite of analytical techniques to demonstrate significant levels of matrix organization and mechanical behaviour analogous to natural tissues. This paper provides an overview of research that has been undertaken to determine how tissues have been grown in vitro with structuring from the molecular, right through to the macroscopic level.
The interfaces between musculoskeletal tissues with contrasting moduli are morphologically and biochemically adapted to allow the transmission of force with minimal injury. Current methods of tissue ...engineering ligaments and tendons do not include the interface and this may limit the future clinical success of engineered musculoskeletal tissues. This study aimed to use solid brushite cement anchors to engineer intact ligaments from bone-to-bone, creating a functional musculoskeletal interface in vitro. We show here that modifying anchor shape and cement composition can alter both the longevity and the strength of an in vitro model of the bone-ligament interface: with values reaching 23 days and 21.6 kPa, respectively. These results validate the use of brushite bone cement to engineer the bone-ligament interface in vitro and raise the potential for future use in ligament replacement surgery.
Tissue engineering offers a promising alternative to the use of autografts in the treatment of ligament injuries. However, current approaches using only biodegradable materials have insufficient ...mechanical strength for load bearing applications. In this research, hybrid bio-artificial ligaments were fabricated using a combination of a titanium alloy spring and a fibrin gel/fibroblast construct. The ends of the ligament prosthesis were incorporated into brushite cement anchors to allow fusion with the host bone. Cell attachment to the titanium spring was examined using scanning electron microscopy and fluorescent staining of cells. The unreinforced constructs were observed to fail at the anchor-ligament junction, while the titanium spring reinforcement was found to assist in even transmission of the load to the ligament, and hence to provide a means of load sharing between the biological construct and the spring. As a result, the reinforced construct failed primarily in the soft tissue region. The good load distribution features from the mechanical data was attributed to the good cellular level adhesion to, and alignment along the coiling of, the length of the spring reinforcement. Incorporation of a biocompatible reinforcement in conjunction with a tissue engineered construct gave improved load distribution, reducing stress concentrations, and significantly increased the ultimate strength at failure. The results suggest that the hybrid approach used here shows promise in developing improved therapies for connective tissue injuries.
The ability to study the gross morphological changes occurring during tissue formation is vital to producing tissue-engineered structures of clinically relevant dimensions in vitro. Here, we have ...used nondestructive methods of digital imaging and optical coherence tomography to monitor the early-stage formation and subsequent maturation of fibrin-based tissue-engineered ligament constructs. In addition, the effect of supplementation with essential promoters of collagen synthesis, ascorbic acid (AA) and proline (P), has been assessed. Contraction of the cell-seeded fibrin gel occurs unevenly within the first 5 days of culture around two fixed anchor points before forming a longitudinal ligament-like construct. AA+P supplementation accelerates gel contraction in the maturation phase of development, producing ligament-like constructs with a higher collagen content and distinct morphology to that of unsupplemented constructs. These studies highlight the importance of being able to control the methods of tissue formation and maturation in vitro to enable the production of tissue-engineered constructs with suitable replacement tissue characteristics for repair of clinical soft-tissue injuries.
In order to produce hydrogel cell culture substrates that are fit for the purpose, it is important that the mechanical properties are well understood not only at the point of cell seeding but ...throughout the culture period. In this study the change in the mechanical properties of three biopolymer hydrogels alginate, low methoxy pectin and gellan gum have been assessed in cell culture conditions. Samples of the gels were prepared encapsulating rat bone marrow stromal cells which were then cultured in osteogenic media. Acellular samples were also prepared and incubated in standard cell culture media. The rheological properties of the gels were measured over a culture period of 28 days and it was found that the gels degraded at very different rates. The degradation occurred most rapidly in the order alginate
>
Low methoxy pectin
>
gellan gum. The ability of each hydrogel to support differentiation of bone marrow stromal cells to osteoblasts was also verified by evidence of mineral deposits in all three of the materials. These results highlight that the mechanical properties of biopolymer hydrogels can vary greatly during
in vitro culture, and provide the potential of selecting hydrogel cell culture substrates with mechanical properties that are tissue specific.
Novel sources of replacement sinews are needed to repair damaged tissue after injury. The current methods of repair ultilise autografts, allografts or xenografts, although each method has distinct ...disadvantages that limit their success. Decellularisation of harvested tissues has been previously investigated for sinew repair with the long-term aim of repopulating the structure with autologous cells. Although this procedure shows promise, the demand for donor scaffolds will always outweigh supply. Here, we report the fabrication of fibrin-based tissue-engineered sinews, which can be decellularised, dehydrated and stored. The sinews may then be rehydrated and repopulated with an autologous cell population. In addition to enabling production of patient-specific implants, interestingly, the process of combined decellularisation, dehydration and rehydration enhanced the mechanical properties of the sinew. The treated sinews exhibited a 2.6-fold increase in maximum load and 8-fold increase in ultimate tensile strength when compared with the control group (p < 0.05 in both cases).
The capacity to study the deposition of mineral within a hydrogel structure is of significant interest to a range of therapies that seek to replace the hard tissues and the hard-soft tissue ...interface. Here, a method is presented that utilises Confocal Raman microscopy as a tool for monitoring mineralisation within hydrogels. Synthetic hard-soft material interfaces were fabricated by apposing brushite (a sparingly soluble calcium phosphate) and biopolymer gel monoliths. The resulting structures were matured over a period of 28 days in phosphate buffered saline. Confocal Raman microscopy of the interfacial region showed the appearance of calcium phosphate salt deposits away from the original interface within the biopolymeric structures. Furthermore, the appearance of octacalcium phosphate and carbonated hydroxyapatite was observed in the region of the brushite cement opposing the biopolymer gel. This study describes not only a method for analysing these composite structures, but also suggests a method for recapitulating the graduated tissue structures that are often found in vivo.
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