Design of a Novel Two-Component Hybrid Dermal Scaffold for the Treatment of Pressure Sores

Topical hADSCs-HA Gel Promotes Skin Regeneration and Angiogenesis in Pressure Ulcers by Paracrine Activating PPARβ/δ Pathway

Background

Pressure ulcer is common in the bedridden elderly with high mortality and lack of effective treatment. In this study, human-adipose-derived-stem-cells-hyaluronic acid gel (hADSCs-HA gel) was developed and applied topically to treat pressure ulcers, of which efficacy and paracrine mechanisms were investigated through in vivo and in vitro experiments.

Methods

Pressure ulcers were established on the backs of C57BL/6 mice and treated topically with hADSCs-HA gel, hADSCs, hyaluronic acid, and normal saline respectively. The rate of wound closure was observed continuously during the following 14 days and the wound samples were obtained for Western blot, histopathology, immunohistochemistry, and proteomic analysis. Human dermal fibroblasts (HDFs) and human venous endothelial cells (HUVECs) under normal or hypoxic conditions were treated with conditioned medium of human ADSCs (ADSC-CM), then CCK-8, scratch test, tube formation, and Western blot were conducted to evaluate the paracrine effects of hADSCs and to explore the underlying mechanism.

Results

The in vivo data demonstrated that hADSCs-HA gel significantly accelerated the healing of pressure ulcers by enhancing collagen expression, angiogenesis, and skin proliferation. The in vitro data revealed that hADSCs strengthened the proliferation and wound healing capabilities of HDFs and HUVECs, meanwhile promoted collagen secretion and tube formation through paracrine mode. ADSC-CM was also proved to exert protective effects on hypoxic HDFs and HUVECs. Besides, the results of proteomic analysis and Western blot elucidated that lipid metabolism and PPARβ/δ pathway mediated the healing effect of hADSCs-HA gel on pressure ulcers.

Conclusion

Our research showed that topical application of hADSCs-HA gel played an important role in dermal regeneration and angiogenesis. Therefore, hADSCs-HA gel exhibited the potential as a novel stem-cell-based therapeutic strategy of treating pressure ulcers in clinical practices.

Polymeric biomaterials for wound healing

Skin indicates a person's state of health and is so important that it influences a person's emotional and psychological behavior. In this context, the effective treatment of wounds is a major concern, since several conventional wound healing materials have not been able to provide adequate healing, often leading to scar formation. Hence, the development of innovative biomaterials for wound healing is essential. Natural and synthetic polymers are used extensively for wound dressings and scaffold production. Both natural and synthetic polymers have beneficial properties and limitations, so they are often used in combination to overcome overcome their individual limitations. The use of different polymers in the production of biomaterials has proven to be a promising alternative for the treatment of wounds, as their capacity to accelerate the healing process has been demonstrated in many studies. Thus, this work focuses on describing several currently commercially available solutions used for the management of skin wounds, such as polymeric biomaterials for skin substitutes. New directions, strategies, and innovative technologies for the design of polymeric biomaterials are also addressed, providing solutions for deep burns, personalized care and faster healing.

Advance in topical biomaterials and mechanisms for the intervention of pressure injury

Pressure injuries (PIs) are localized tissue damage resulting from prolonged compression or shear forces on the skin or underlying tissue, or both. Different stages of PIs share common features include intense oxidative stress, abnormal inflammatory response, cell death, and subdued tissue remodeling. Despite various clinical interventions, stage 1 or stage 2 PIs are hard to monitor for the changes of skin or identify from other disease, whereas stage 3 or stage 4 PIs are challenging to heal, painful, expensive to manage, and have a negative impact on quality of life. Here, we review the underlying pathogenesis and the current advances of biochemicals in PIs. We first discuss the crucial events involved in the pathogenesis of PIs and key biochemical pathways lead to wound delay. Then, we examine the recent progress of biomaterials-assisted wound prevention and healing and their prospects.

Stem cell and tissue engineering approaches in pressure ulcer treatment

CONTEXT

Pressure ulcers or injuries, arise from ischemic damage to soft tissues induced by unrelieved pressure over a bony prominence. They are usually difficult to treat with standard medical therapy and often they recur. In the search for better treatment options, promising alternative forms of treatment are today emerging. Within the field of regenerative medicine, ongoing research on advanced therapies seeks to develop medicinal products based on gene therapy, somatic cell therapy, tissue-engineering and combinations of these.

OBJECTIVE

The main objective is to perform an overview of experimental and clinical developments in somatic cell therapy and tissue engineering targeting the treatment of pressure injuries.

METHODS

Searching terms as "PRESSURE ULCER", "STEM CELL THERAPY", "TISSUE ENGINEERING" or "WOUND HEALING" were used in combination or alone, including publications refered to basic and clinical research and focusing on articles showing results obtained in a clinical context. A total of 80 references are cited, including 23 references published in the 3 last years.

RESULTS

The results suggest that this form of treatment could be an interesting option in patients with difficult-to-treat ulcers as spinal cord injury patients.

CONCLUSION

This field of regenerative medicine is very broad and further research is warranted.

Optical coherence tomography for in vivo longitudinal monitoring of artificial dermal scaffold

OBJECTIVES

Artificial dermal scaffold (ADS) has undergone rapid development and been increasingly used for treating skin wound in clinics due to its good biocompatibility, controllable degradation, and low risk of disease infection. To obtain good treatment efficacy, ADS needs to be monitored longitudinally during the treatment process. For example, scaffold-tissue fit, cell in-growth, vascular regeneration, and scaffold degradation are the key properties to be inspected. However, to date, there are no effective, real-time, and noninvasive techniques to meet the requirement of the scaffold monitoring above.

MATERIALS AND METHODS

In this study, we propose to use optical coherence tomography (OCT) to monitor ADS in vivo through three-dimensional imaging. A swept source OCT system with a handheld probe was developed for in vivo skin imaging. Moreover, a cell in-growth, vascular regeneration, and scaffold degradation rate (IRDR) was defined with the volume reduction rate of the scaffold's collagen sponge layer. To measure the IRDR, a semiautomatic image segmentation algorithm was designed based on U-Net to segment the collagen sponge layer of the scaffold from OCT images.

RESULTS

The results show that the scaffold-tissue fit can be clearly visualized under OCT imaging. The IRDR can be computed based on the volume of the segmented collagen sponge layer. It is observed that the IRDR appeared to a linear function of the time and in addition, the IRDR varied among different skin parts.

CONCLUSION

Overall, it can be concluded that OCT has a good potential to monitor ADS in vivo. This can help guide the clinicians to control the treatment with ADS to improve the therapy.

New insights into balancing wound healing and scarless skin repair

Scars caused by skin injuries after burns, wounds, abrasions and operations have serious physical and psychological effects on patients. In recent years, the research of scar free wound repair has been greatly expanded. However, understanding the complex mechanisms of wound healing, in which various cells, cytokines and mechanical force interact, is critical to developing a treatment that can achieve scarless wound healing. Therefore, this paper reviews the types of wounds, the mechanism of scar formation in the healing process, and the current research progress on the dual consideration of wound healing and scar prevention, and some strategies for the treatment of scar free wound repair.

Technological advances in fibrin for tissue engineering

Fibrin is a promising natural polymer that is widely used for diverse applications, such as hemostatic glue, carrier for drug and cell delivery, and matrix for tissue engineering. Despite the significant advances in the use of fibrin for bioengineering and biomedical applications, some of its characteristics must be improved for suitability for general use. For example, fibrin hydrogels tend to shrink and degrade quickly after polymerization, particularly when they contain embedded cells. In addition, their poor mechanical properties and batch-to-batch variability affect their handling, long-term stability, standardization, and reliability. One of the most widely used approaches to improve their properties has been modification of the structure and composition of fibrin hydrogels. In this review, recent advances in composite fibrin scaffolds, chemically modified fibrin hydrogels, interpenetrated polymer network (IPN) hydrogels composed of fibrin and other synthetic or natural polymers are critically reviewed, focusing on their use for tissue engineering.

Porous biomaterials for tissue engineering: a review

The field of biomaterials has grown rapidly over the past decades. Within this field, porous biomaterials have played a remarkable role in: (i) enabling the manufacture of complex three-dimensional structures; (ii) recreating mechanical properties close to those of the host tissues; (iii) facilitating interconnected structures for the transport of macromolecules and cells; and (iv) behaving as biocompatible inserts, tailored to either interact or not with the host body. This review outlines a brief history of the development of biomaterials, before discussing current materials proposed for use as porous biomaterials and exploring the state-of-the-art in their manufacture. The wide clinical applications of these materials are extensively discussed, drawing on specific examples of how the porous features of such biomaterials impact their behaviours, as well as the advantages and challenges faced, for each class of the materials.

Poly-ε-Caprolactone/Fibrin-Alginate Scaffold: A New Pro-Angiogenic Composite Biomaterial for the Treatment of Bone Defects

We hypothesized that a composite of 3D porous melt-electrowritten poly-ɛ-caprolactone (PCL) coated throughout with a porous and slowly biodegradable fibrin/alginate (FA) matrix would accelerate bone repair due to its angiogenic potential. Scanning electron microscopy showed that the open pore structure of the FA matrix was maintained in the PCL/FA composites. Fourier transform infrared spectroscopy and differential scanning calorimetry showed complete coverage of the PCL fibres by FA, and the PCL/FA crystallinity was decreased compared with PCL. In vitro cell work with osteoprogenitor cells showed that they preferentially bound to the FA component and proliferated on all scaffolds over 28 days. A chorioallantoic membrane assay showed more blood vessel infiltration into FA and PCL/FA compared with PCL, and a significantly higher number of bifurcation points for PCL/FA compared with both FA and PCL. Implantation into a rat cranial defect model followed by microcomputed tomography, histology, and immunohistochemistry after 4- and 12-weeks post operation showed fast early bone formation at week 4, with significantly higher bone formation for FA and PCL/FA compared with PCL. However, this phenomenon was not extrapolated to week 12. Therefore, for long-term bone regeneration, tuning of FA degradation to ensure syncing with new bone formation is likely necessary.

Pro-angiogenic and osteogenic composite scaffolds of fibrin, alginate and calcium phosphate for bone tissue engineering

Due to the limitations of bone autografts, we aimed to develop new composite biomaterials with pro-angiogenic and osteogenic properties to be used as scaffolds in bone tissue engineering applications. We used a porous, cross-linked and slowly biodegradable fibrin/alginate scaffold originally developed in our laboratory for wound healing, throughout which deposits of calcium phosphate (CaP) were evenly incorporated using an established biomimetic method. Material characterisation revealed the porous nature and confirmed the deposition of CaP precursor phases throughout the scaffolds. MC3T3-E1 cells adhered to the scaffolds, proliferated, migrated and differentiated down the osteogenic pathway during the culture period. Chick chorioallantoic membrane (CAM) assay results showed that the scaffolds were pro-angiogenic and biocompatible. The work presented here gave useful insights into the potential of these pro-angiogenic and osteogenic scaffolds for bone tissue engineering and merits further research in a pre-clinical model prior to its clinical translation.

Pre-screening the intrinsic angiogenic capacity of biomaterials in an optimised ex ovo chorioallantoic membrane model

Biomaterial development for clinical applications is currently on the rise. This necessitates adequate in vitro testing, where the structure and composition of biomaterials must be specifically tailored to withstand in situ repair and regeneration responses for a successful clinical outcome. The chorioallantoic membrane of chicken embryos has been previously used to study angiogenesis, a prerequisite for most tissue repair and regeneration. In this study, we report an optimised ex ovo method using a glass-cling film set-up that yields increased embryo survival rates and has an improved protocol for harvesting biomaterials. Furthermore, we used this method to examine the intrinsic angiogenic capacity of a variety of biomaterials categorised as natural, synthetic, natural/synthetic and natural/natural composites with varying porosities. We detected significant differences in biomaterials' angiogenesis with natural polymers and polymers with a high overall porosity showing a greater vascularisation compared to synthetic polymers. Therefore, our proposed ex ovo chorioallantoic membrane method can be effectively used to pre-screen biomaterials intended for clinical application.

The importance of factorial design in tissue engineering and biomaterials science: Optimisation of cell seeding efficiency on dermal scaffolds as a case study

This article presents a case study to show the usefulness and importance of using factorial design in tissue engineering and biomaterials science. We used a full factorial experimental design (2 × 2 × 2 × 3) to solve a routine query in every biomaterial research project: the optimisation of cell seeding efficiency for pre-clinical in vitro cell studies, the importance of which is often overlooked. In addition, tissue-engineered scaffolds can be cellularised with relevant cell type(s) to form implantable tissue constructs, where the cell seeding method must be reliable and robust. Our results show the complex relationship between cells and scaffolds and suggest that the optimum seeding conditions for each material may be different due to different material properties, and therefore, should be investigated for individual scaffolds. Our factorial experimental design can be easily translated to other cell types and three-dimensional biomaterials, where multiple interacting variables can be thoroughly investigated for better understanding of cell–biomaterial interactions.