Zhidao Xia, Qian Wang

2022, 3(4): 235–236. doi:https://doi.org/10.12336/biomatertransl.2022.04.002

Elena Giusto, Gordon Blunn, Roberta Ferro de Godoy, Chaozong Liu, Catherine Pendegrass

2022, 3(4): 243–249. doi:https://doi.org/10.12336/biomatertransl.2022.04.004

Osseointegrated transcutaneous implants could provide an alternative and improved means of attaching artificial limbs for amputees, however epithelial down growth, inflammation, and infections are common failure modalities associated with their use. To overcome these problems, a tight seal associated with the epidermal and dermal adhesion to the implant is crucial. This could be achieved with specific biomaterials (that mimic the surrounding tissue), or a tissue–specific design to enhance the proliferation and attachment of dermal fibroblasts and keratinocytes. The intraosseous transcutaneous amputation prosthesis is a new device with a pylon and a flange, which is specifically designed for optimising soft tissue attachment. Previously the flange has been fabricated using traditional machining techniques, however, the advent of additive layer manufacturing (ALM) has enabled 3–dimensional porous flanges with specific pore sizes to be used to optimise soft tissue integration and reduce failure of osseointegrated transcutaneous implants. The study aimed to investigate the effect of ALM–manufactured porous flanges on soft tissue ingrowth and attachment in an in vivo ovine model that replicates an osseointegrated percutaneous implant. At 12 and 24 weeks, epithelial downgrowth, dermal attachment and revascularisation into ALM–manufactured flanges with three different pore sizes were compared with machined controls where the pores were made using conventional drilling. The pore sizes of the ALM flanges were 700, 1000 and 1250 μm. We hypothesised that ALM porous flanges would reduce downgrowth, improve soft tissue integration and revascularisation compared with machined controls. The results supported our hypothesis with significantly greater soft tissue integration and revascularisation in ALM porous flanges compared with machined controls.

Zhidao Xia

2022, 3(4): 237–239. doi:https://doi.org/10.12336/biomatertransl.2022.04.001

Haoyu Guo, Xin Huang

2022, 3(4): 240–242. doi:https://doi.org/10.12336/biomatertransl.2022.04.003

Jingyu Fan, Elizabeth Pung, Yuan Lin, Qian Wang

2022, 3(4): 250–263. doi:https://doi.org/10.12336/biomatertransl.2022.04.005

Hydrogen sulfide (H₂S) has been reported as an endogenous gasotransmitter that contributes to the modulation of a myriad of biological signalling pathways, which includes maintaining homeostasis in living organisms at physiological concentrations, controlling protein sulfhydration and persulfidation for signalling processes, mediating neurodegeneration, and regulating inflammation and innate immunity, etc. As a result, researchers are actively exploring effective approaches to evaluate the properties and the distribution of H₂S in vivo. Furthermore, the regulation of the physiological conditions of H₂S in vivo introduces the opportunity to further study the molecular mechanisms by which H₂S regulates cellular functions. In recent years, many H₂S–releasing compounds and biomaterials that can deliver H₂S to various body systems have been developed to provide sustained and stable H₂S delivery. Additionally, various designs of these H₂S–releasing biomaterials have been proposed to aid in the normal conduction of physiological processes, such as cardioprotection and wound healing, by modulating different signalling pathways and cell functionalities. Using biomaterials as a platform to control the delivery of H₂S introduces the opportunity to fine tune the physiological concentration of H₂S in vivo, a key to many therapeutic applications. In this review, we highlight recent research works concerning the development and application of H₂S–releasing biomaterials with a special emphasis to different release triggering conditions in in vivo studies. We believe that the further exploration of the molecular mechanisms underlying H₂S donors and their function when incorporated with various biomaterials will potentially help us understand the pathophysiological mechanisms of different diseases and assist the development of H₂S–based therapies.

Yi Wang, Yangyang Chen, Yulong Wei

2022, 3(4): 264–279. doi:https://doi.org/10.12336/biomatertransl.2022.04.006

Clinical therapeutics for the regeneration of osteochondral defects (OCD) in the early stages of osteoarthritis remain an enormous challenge in orthopaedics. For in-depth studies of tissue engineering and regenerative medicine in terms of OCD treatment, the utility of an optimal OCD animal model is crucial for assessing the effects of implanted biomaterials on the repair of damaged osteochondral tissues. Currently, the most frequently used in vivo animal models for OCD regeneration include mice, rats, rabbits, dogs, pigs, goats, sheep, horses and nonhuman primates. However, there is no single “gold standard” animal model to accurately recapitulate human disease in all aspects, thus understanding the benefits and limitations of each animal model is critical for selecting the most suitable one. In this review, we aim to elaborate the complex pathological changes in osteoarthritic joints and to summarise the advantages and limitations of OCD animal models utilised for biomaterial testing along with the methodology of outcome assessment. Furthermore, we review the surgical procedures of OCD creation in different species, and the novel biomaterials that promote OCD regeneration. Above all, it provides a significant reference for selection of an appropriate animal model for use in preclinical in vivo studies of biomaterial-assisted osteochondral regeneration in osteoarthritic joints.

Guixin Yuan, Zan Li, Xixi Lin, Na Li, Ren Xu

2022, 3(4): 280–294. doi:https://doi.org/10.12336/biomatertransl.2022.04.007

Tissue–resident stem cells are a group of stem cells distinguished by their capacity for self–renewal and multilineage differentiation capability with tissue specificity. Among these tissue–resident stem cells, skeletal stem cells (SSCs) were discovered in the growth plate region through a combination of cell surface markers and lineage tracing series. With the process of unravelling the anatomical variation of SSCs, researchers were also keen to investigate the developmental diversity outside the long bones, including in the sutures, craniofacial sites, and spinal regions. Recently, fluorescence–activated cell sorting, lineage tracing, and single–cell sequencing have been used to map lineage trajectories by studying SSCs with different spatiotemporal distributions. The SSC niche also plays a pivotal role in regulating SSC fate, such as cell–cell interactions mediated by multiple signalling pathways. This review focuses on discussing the spatial and temporal distribution of SSCs, and broadening our understanding of the diversity and plasticity of SSCs by summarizing the progress of research into SSCs in recent years.