From collagen chemistry towards cell therapy - a personal journey

Natural Coatings and Surface Modifications on Magnesium Alloys for Biomedical Applications

Magnesium (Mg) alloys have great potential in biomedical applications due to their incomparable properties regarding other metals, such as stainless steels, Co-Cr alloys, and titanium (Ti) alloys. However, when Mg engages with body fluids, its degradation rate increases, inhibiting the complete healing of bone tissue. For this reason, it has been necessary to implement protective coatings to control the rate of degradation. This review focuses on natural biopolymer coatings used on Mg alloys for resorbable biomedical applications, as well as some modification techniques implemented before applying natural polymer coatings to improve their performance. Issues such as improving the corrosion resistance, cell adhesion, proliferation, and biodegradability of natural biopolymers are discussed through their basic comparison with inorganic-type coatings. Emphasis is placed on the expected biological behavior of each natural polymer described, to provide basic information as a reference on this topic.

A Comprehensive Review on Collagen Type I Development of Biomaterials for Tissue Engineering: From Biosynthesis to Bioscaffold

Collagen is the most abundant structural protein found in humans and mammals, particularly in the extracellular matrix (ECM). Its primary function is to hold the body together. The collagen superfamily of proteins includes over 20 types that have been identified. Yet, collagen type I is the major component in many tissues and can be extracted as a natural biomaterial for various medical and biological purposes. Collagen has multiple advantageous characteristics, including varied sources, biocompatibility, sustainability, low immunogenicity, porosity, and biodegradability. As such, collagen-type-I-based bioscaffolds have been widely used in tissue engineering. Biomaterials based on collagen type I can also be modified to improve their functions, such as by crosslinking to strengthen the mechanical property or adding biochemical factors to enhance their biological activity. This review discusses the complexities of collagen type I structure, biosynthesis, sources for collagen derivatives, methods of isolation and purification, physicochemical characteristics, and the current development of collagen-type-I-based scaffolds in tissue engineering applications. The advancement of additional novel tissue engineered bioproducts with refined techniques and continuous biomaterial augmentation is facilitated by understanding the conventional design and application of biomaterials based on collagen type I.

Photo-Cross-Linkable Human Albumin Colloidal Gels Facilitate In Vivo Vascular Integration for Regenerative Medicine

Biodegradable cellular and acellular scaffolds have great potential to regenerate damaged tissues or organs by creating a proper extracellular matrix (ECM) capable of recruiting endogenous cells to support cellular ingrowth. However, since hydrogel-based scaffolds normally degrade through surface erosion, cell migration and ingrowth into scaffolds might be inhibited early in the implantation. This could result in insufficient de novo tissue formation in the injured area. To address these challenges, continuous and microsized strand-like networks could be incorporated into scaffolds to guide and recruit endogenous cells in rapid manner. Fabrication of such microarchitectures in scaffolds is often a laborious and time-consuming process and could compromise the structural integrity of the scaffold or impact cell viability. Here, we have developed a fast single-step approach to fabricate colloidal hydrogels, which are made up of randomly packed human serum albumin-based photo-cross-linkable microparticles with continuous internal networks of microscale voids. The human serum albumin conjugated with methacrylic groups were assembled to microsized aggregates for achieving unique porous structures inside the colloidal gels. The albumin hydrogels showed tunable mechanical properties such as elastic modulus, porosity, and biodegradability, providing a suitable ECM for various cells such as cardiomyoblasts and endothelial cells. In addition, the encapsulated cells within the hydrogel showed improved cell retention and increased survivability in vitro. Microporous structures of the colloidal gels can serve as a guide for the infiltration of host cells upon implantation, achieving rapid recruitment of hematopoietic cells and, ultimately, enhancing the tissue regeneration capacity of implanted scaffolds.

Jellyfish Collagen: A Biocompatible Collagen Source for 3D Scaffold Fabrication and Enhanced Chondrogenicity

Osteoarthritis (OA) is a multifactorial disease leading to degeneration of articular cartilage, causing morbidity in approximately 8.5 million of the UK population. As the dense extracellular matrix of articular cartilage is primarily composed of collagen, cartilage repair strategies have exploited the biocompatibility and mechanical strength of bovine and porcine collagen to produce robust scaffolds for procedures such as matrix-induced chondrocyte implantation (MACI). However, mammalian sourced collagens pose safety risks such as bovine spongiform encephalopathy, transmissible spongiform encephalopathy and possible transmission of viral vectors. This study characterised a non-mammalian jellyfish (Rhizostoma pulmo) collagen as an alternative, safer source in scaffold production for clinical use. Jellyfish collagen demonstrated comparable scaffold structural properties and stability when compared to mammalian collagen. Jellyfish collagen also displayed comparable immunogenic responses (platelet and leukocyte activation/cell death) and cytokine release profile in comparison to mammalian collagen in vitro. Further histological analysis of jellyfish collagen revealed bovine chondroprogenitor cell invasion and proliferation in the scaffold structures, where the scaffold supported enhanced chondrogenesis in the presence of TGFβ1. This study highlights the potential of jellyfish collagen as a safe and biocompatible biomaterial for both OA repair and further regenerative medicine applications.

Natural polypeptides-based electrically conductive biomaterials for tissue engineering

Fabrication of an appropriate scaffold is the key fundamental step required for a successful tissue engineering (TE). The artificial scaffold as extracellular matrix in TE has noticeable role in the fate of cells in terms of their attachment, proliferation, differentiation, orientation and movement. In addition, chemical and electrical stimulations affect various behaviors of cells such as polarity and functionality. Therefore, the fabrication approach and materials used for the preparation of scaffold should be more considered. Various synthetic and natural polymers have been used extensively for the preparation of scaffolds. The electrically conductive polymers (ECPs), moreover, have been used in combination with other polymers to apply electric fields (EF) during TE. In this context, composites of natural polypeptides and ECPs can be taken into account as context for the preparation of suitable scaffolds with superior biological and physicochemical features. In this review, we overviewed the simultaneous usage of natural polypeptides and ECPs for the fabrication of scaffolds in TE.

Protective effect of ligustrazine on lumbar intervertebral disc degeneration of rats induced by prolonged upright posture

Most chronic low back pain is the result of degeneration of the lumbar intervertebral disc. Ligustrazine, an alkaloid from Chuanxiong, reportedly is able to relieve pain, suppress inflammation, and treat osteoarthritis and it has the protective effect on cartilage and chondrocytes. Therefore, we asked whether ligustrazine could reduce intervertebral disc degeneration. To determine the effect of ligustrazine on disc degeneration, we applied a rat model. The intervertebral disc degeneration of the rats was induced by prolonged upright posture. We found that pretreatment with ligustrazine for 1 month recovered the structural distortion of the degenerative disc; inhibited the expression of type X collagen, matrix metalloproteinase (MMP)-13, and MMP3; upregulated type II collagen; and decreased IL-1β, cyclooxygenase (COX)-2, and inducible nitric oxide synthase (iNOS) expression. In conclusion, ligustrazine is a promising agent for treating lumbar intervertebral disc degeneration disease.

The effects of different crossing-linking conditions of genipin on type I collagen scaffolds: an in vitro evaluation

The purpose of this paper is to analyze the properties of fabricating rat tail type I collagen scaffolds cross-linked with genipin under different conditions. The porous genipin cross-linked scaffolds are obtained through a two step freeze-drying process. To find out the optimal cross-link condition, we used different genipin concentrations and various cross-linked temperatures to prepare the scaffolds in this study. The morphologies of the scaffolds were characterized by scanning electron microscope, and the mechanical properties of the scaffolds were evaluated under dynamic compression. Additionally, the cross-linking degree was assessed by ninhydrin assay. To investigate the swelling ratio and the in vitro degradation of the collagen scaffold, the tests were also carried out by immersion of the scaffolds in a PBS solution or digestion in a type I collagenase respectively. The morphologies of the non-cross-linked scaffolds presented a lattice-like structure while the cross-linked ones displayed a sheet-like framework. The morphology of the genipin cross-linked scaffolds could be significantly changed by either increasing genipin concentration or the temperature. The swelling ratio of each cross-linked scaffold was much lower than that of the control (non-cross-linked).The ninhydrin assay demonstrated that the higher temperature and genipin concentration could obviously increase the cross-linking efficiency. The in vitro degradation studies indicated that genipin cross-linking can effectively elevate the biostability of the scaffolds. The biocompatibility and cytotoxicity of the scaffolds was evaluated by culturing rat chondrocytes on the scaffold in vitro and by MTT. The results of MTT and the fact that the chondrocytes adhered well to the scaffolds demonstrated that genipin cross-linked scaffolds possessed an excellent biocompatibility and low cytotoxicity. Based on these results, 0.3 % genipin concentrations and 37 °C cross-linked temperatures are recommended.

Prolonged upright posture induces calcified hypertrophy in the cartilage end plate in rat lumbar spine

STUDY DESIGN

Both forelimbs of rats were amputated and these rats were kept in the custom-made cages to keep prolonged and repeated upright posture. Changes of bone were observed in the lumbar vertebrae at three different time points after the surgery.

OBJECTIVE

To investigate the effect of prolonged and repeated upright posture on the cartilage end plate of rat lumbar vertebrae.

SUMMARY OF BACKGROUND DATA

Previous studies show calcified hypertrophy is related to mechanical stress, but there are no clear evidences to indicate whether or not long-term and repeated assumption of the upright posture could result in calcified hypertrophy in cartilage end plate of rat lumbar spine.

METHODS

The forelimbs of 30 rats were amputated when they were 1 month old. These rats were kept in the custom-made cages and were forced to stand upright on their hind-limbs and tails to obtain water and food. Normal rats of the same ages kept in regular cages were used as control. The rats were killed at 5, 7, and 9 months after the surgery and lumbar vertebrae samples were harvested for micro-CT, histologic, and immunohistochemical studies. Total RNA isolated from these samples were used for real-time RT-PCR of type X collagen (Col10α1), vascular endothelial growth factor (VEGF), and transforming growth factor β1 (TGF-β1).

RESULTS

Micro-CT showed increased inner part of cartilage end plate. Histologic revealed peripheral hypertrophy of disc after the surgery. Immunostaining and real-time RT-PCR showed increased protein and mRNA expression of type X collagen, VEGF, and TGF-β1.

CONCLUSION

Prolonged upright posture induces cartilage end plate calcification and hypertrophy in rat lumbar spine.

Academic and molecular matrices: a study of the transformations of connective tissue research at the University of Manchester (1947-1996)

This paper explores the different identities adopted by connective tissue research at the University of Manchester during the second half of the 20th century. By looking at the long-term redefinition of a research programme, it sheds new light on the interactions between different and conflicting levels in the study of biomedicine, such as the local and the global, or the medical and the biological. It also addresses the gap in the literature between the first biomedical complexes after World War II and the emergence of biotechnology. Connective tissue research in Manchester emerged as a field focused on new treatments for rheumatic diseases. During the 1950s and 60s, it absorbed a number of laboratory techniques from biology, namely cell culture and electron microscopy. The transformations in scientific policy during the late 70s and the migration of Manchester researchers to the US led them to adopt recombinant DNA methods, which were borrowed from human genetics. This resulted in the emergence of cell matrix biology, a new field which had one of its reference centres in Manchester. The Manchester story shows the potential of detailed and chronologically wide local studies of patterns of work to understand the mechanisms by which new biomedical tools and institutions interact with long-standing problems and existing affiliations.

The collagen family

Collagens are the most abundant proteins in mammals. The collagen family comprises 28 members that contain at least one triple-helical domain. Collagens are deposited in the extracellular matrix where most of them form supramolecular assemblies. Four collagens are type II membrane proteins that also exist in a soluble form released from the cell surface by shedding. Collagens play structural roles and contribute to mechanical properties, organization, and shape of tissues. They interact with cells via several receptor families and regulate their proliferation, migration, and differentiation. Some collagens have a restricted tissue distribution and hence specific biological functions.

Herb formula "Fufangqishe-Pill" prevents upright posture-induced intervertebral disc degeneration at the lumbar in rats

Degeneration of the lumbar spine plays an important role in most chronic low back pain. Prevention of lumbar intervertebral disc (IVD) degeneration is therefore a high research priority. Both our previous multicenter clinical trials and pharmacological research showed that Fufangqishe-Pill (FFQSP), a newly patented traditional Chinese medicine, could effectively relieve the symptoms of neck pain and prevent cervical degeneration. To clarify the effect of FFQSP on lumbar IVD degeneration, we applied a lumbar IVD degeneration rat model induced by prolonged upright posture. Pretreatment of FFQSP for one month prevented the histological changes indicating IVD disorganization; increased type II-collagen level, decreased type X-collagen protein level, and increased Col2alpha1 mRNA expression at all time points; and decreased Col10alpha1, matrix metalloproteinase (MMP)-3, MMP13, and Interleukin (IL)-1beta mRNA expression induced by upright posture for 7 and 9 months. These results suggest that FFQSP prevents lumbar IVD degeneration induced by upright posture. FFQSP is a promising medicine for lumbar IVD degeneration disease.

Evidence to suggest that cathepsin K degrades articular cartilage in naturally occurring equine osteoarthritis

OBJECTIVE

The mechanisms leading to degeneration of articular cartilage in osteoarthritis (OA) are complex and not yet fully understood. Cathepsin K (CK) is a cysteine protease which can also cleave the triple helix of type II collagen. This exposes a neoepitope that can now be identified by specific antibodies. The aim of this study was to obtain evidence suggesting a role for CK in naturally occurring equine OA in both lesional and peri-lesional regions.

METHODS

Articular cartilages (n=12 horses; 5 healthy, 7 OA) were harvested from animals postmortem. A gross macroscopic examination, histologic (Safranin O-Fast Green and Picrosirius red staining) and immunohistochemical evaluation were performed. Samples were divided into normal appearing cartilage, peri-lesional and lesional cartilage. Cartilage degradation in the samples was graded histologically and immunohistochemically. CK and possible CK cleavage were detected immunohistochemically with specific anti-protein and anti-neoepitope antibodies, respectively. A comparison of CK neoepitope (C2K) production with the collagenase-generated neoepitope produced by matrix metalloproteinases (MMP)-1, 8 and 13 (C2C) was also assessed immunohistochemically.

RESULTS

CK and CK cleavage were significantly more abundant in OA cartilage (both peri-lesional and lesional) when compared to remote cartilage within the sample joint or cartilage from healthy joints. The immunohistochemical pattern observed for CK degradation (C2K) was similar to that of collagenase degradation (C2C). Macroscopic cartilage changes and histologic findings were significantly correlated with immunohistochemistry results.

CONCLUSION

The data generated suggests that CK may be involved in cartilage collagen degradation in naturally occurring osteoarthritis.

Prolonged upright posture induces degenerative changes in intervertebral discs in rat lumbar spine

STUDY DESIGN

Both forelimbs of rats were amputated, and these rats were kept in the custom-made cages that kept the rats in prolonged upright posture. Pathologic changes were observed in the lumbar spine at different time points after the surgery.

OBJECTIVE

To investigate the effect of upright posture on intervertebral discs of rat lumbar spine.

SUMMARY OF BACKGROUND DATA

Previous studies have shown that increased axial forces on the spine can decrease the height of the intervertebral disc, but there are no data to indicate whether or not long-term and repeated assumption of the upright posture could result in degenerative changes.

METHODS

The forelimbs of 30 rats were amputated when they were 1-month old. These rats were kept in the custom-made cages and were forced to stand upright on their hind-limbs and tails to obtain water and food. Normal rats of the same ages kept in regular cages were used as control. The rats were killed at 5, 7, and 9 months after the surgery, and the intervertebral discs samples of lumbar spine were harvested for histologic and immunohistochemical studies. Total RNA isolated from these samples was used for real-time PCR of type II collagen (Col2alpha1), type X collagen (Col10alpha1), matrix metalloproteinase-13 (MMP-13), aggrecan, and disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5). RESULTS.: Histologic analysis showed degenerative changes of the intervertebral discs after surgery such as disordered collagen structure of endplate cartilage, fragmentation of annulus fibrosus, and decreased height of disc. Immunostaining revealed decreased protein level of type II collagen and increased protein expression of type X collagen. Real-time PCR showed upregulated expression of MMP 13, ADAMTS-5, and Col10alpha1 mRNA and downregulated mRNA expression of Col2alpha1 and aggrecan.

CONCLUSION

Long-term and repeated assumption of the upright stance accelerates disc degeneration in rats.

Collagen tissue engineering: development of novel biomaterials and applications

Scientific investigations involving collagen have inspired tissue engineering and design of biomaterials since collagen fibrils and their networks primarily regulate and define most tissues. The collagen networks form a highly organized, three-dimensional architecture to entrap other ingredients. Biomaterials are expected to function as cell scaffolds to replace native collagen-based extracellular matrix. The composition and properties of biomaterials used as scaffold for tissue engineering significantly affect the regeneration of neo-tissues and influence the conditions of collagen engineering. The complex scenario of collagen characteristics, types, fibril arrangement, and collagen structure-related functions (in a variety of connective tissues including bone, cartilage, tendon, skin and cornea) are addressed in this review. Discussion will focus on nanofibrillar assemblies and artificial synthetic peptides that mimic either the fibrillar structure or the elemental components of type I collagen as illustrated by their preliminary applications in tissue engineering. Conventional biomaterials used as scaffolds in engineering collagen-containing tissues are also discussed. The design of novel biomaterials and application of conventional biomaterials will facilitate development of additional novel tissue engineering bioproducts by refining the currently available techniques. The field of tissue engineering will ultimately be advanced by increasing control of collagen in native tissue and by continual manipulation of biomaterials.