Use of photosynthetic transgenic cyanobacteria to promote lymphangiogenesis in scaffolds for dermal regeneration

Hypoxic environment of wounds and photosynthesis-based oxygen therapy

The hypoxic environment is among the most important factors that complicates the healing of chronic wounds, such as venous leg ulcers, pressure injuries and diabetic foot ulcers, which seriously affects the quality of life of patients. Various oxygen supply treatments are used in clinical practice to improve the hypoxic environment at the wound site. However, problems still occur, such as insufficient oxygen supply, short oxygen infusion time and potential biosafety risks. In recent years, artificial photosynthetic systems have become a research hotspot in the fields of materials and energy. Photosynthesis is expected to improve the oxygen level at wound sites and promote wound healing because the method provides a continuous oxygen supply and has good biosafety. In this paper, oxygen treatment methods for wounds are reviewed, and the oxygen supply principle and construction of artificial photosynthesis systems are described. Finally, research progress on the photosynthetic oxygen production system to promote wound healing is summarized.

Biocompatibility of Synechococcus sp. PCC 7002 with Human Dermal Cells In Vitro

Being the green gold of the future, cyanobacteria have recently attracted considerable interest worldwide. This study investigates the adaptability and biocompatibility of the cyanobacterial strain Synechococcus sp. PCC 7002 with human dermal cells, focusing on its potential application in biomedical contexts. First, we investigated the adaptability of Synechococcus PCC 7002 bacteria to human cell culture conditions. Next, we evaluated the biocompatibility of cyanobacteria with common dermal cells, like 3T3 fibroblasts and HaCaT keratinocytes. Therefore, cells were directly and indirectly cocultured with the corresponding cells, and we measured metabolic activity (AlamarBlue assay) and proliferation (cell count and PicoGreen assay). The lactate dehydrogenase (LDH) assay was performed to determine the cytotoxic effect of cyanobacteria and their nutrition medium on human dermal cells. The cyanobacteria exhibited exponential growth under conventional human cell culture conditions, with the temperature and medium composition not affecting their viability. In addition, the effect of illumination on the proliferation capacity was investigated, showing a significant impact of light exposure on bacterial growth. The measured oxygen production under hypoxic conditions demonstrated a sufficient oxygen supply for further tissue engineering approaches depending on the number of bacteria. There were no significant adverse effects on human cell viability and growth under coculture conditions, whereas the LDH assay assessed signs of cytotoxicity regarding 3T3 fibroblasts after 2 days of coculturing. These negative effects were dismissed after 4 days. The findings highlight the potential of Synechococcus sp. PCC 7002 for integration into biomedical approaches. We found no cytotoxicity of cyanobacteria on 3T3 fibroblasts and HaCaT keratinocytes, thus paving the way for further in vivo studies to assess long-term effects and systemic reactions.

Engineering the next generation of theranostic biomaterials with synthetic biology

Biomaterials have evolved from inert materials to responsive entities, playing a crucial role in disease diagnosis, treatment, and modeling. However, their advancement is hindered by limitations in chemical and mechanical approaches. Synthetic biology enabling the genetically reprograming of biological systems offers a new paradigm. It has achieved remarkable progresses in cell reprogramming, engineering designer cells for diverse applications. Synthetic biology also encompasses cell-free systems and rational design of biological molecules. This review focuses on the application of synthetic biology in theranostics, which boost rapid development of advanced biomaterials. We introduce key fundamental concepts of synthetic biology and highlight frontier applications thereof, aiming to explore the intersection of synthetic biology and biomaterials. This integration holds tremendous promise for advancing biomaterial engineering with programable complex functions.

Microalgae share key features with human erythrocytes and can safely circulate through the vascular system in mice

As animal cells cannot produce oxygen, erythrocytes are responsible for gas interchange, being able to capture and deliver oxygen upon tissue request. Interestingly, several other cells in nature produce oxygen by photosynthesis, raising the question of whether they could circulate within the vascular networks, acting as an alternative source for oxygen delivery. To address this long-term goal, here some physical and mechanical features of the photosynthetic microalga Chlamydomona reinhardtii were studied and compared with erythrocytes, revealing that both exhibit similar size and rheological properties. Moreover, key biocompatibility aspects of the microalgae were evaluated in vitro and in vivo, showing that C. reinhardtii can be co-cultured with endothelial cells, without affecting each other's morphology and viability. Moreover, short-term systemic perfusion of the microalgae showed a thoroughly intravascular distribution in mice. Finally, the systemic injection of high numbers of microalgae did not trigger deleterious responses in living mice. Altogether, this work provides key scientific insights to support the notion that photosynthetic oxygenation could be achieved by circulating microalgae, representing another important step towards human photosynthesis. KEY POINTS: • C. reinhardtii and endothelial cells are biocompatible in vitro. • C. reinhardtii distribute throughout the entire vasculature after mice perfusion. • C. reinhardtii do not trigger deleterious responses after injection in mice.

The use of commercial fibrin glue in dermal replacement material reduces angiogenic and lymphangiogenic gene and protein expression in vitro

BACKGROUND

Commercial fibrin glue is increasingly finding its way into clinical practice in surgeries to seal anastomosis, and initiate hemostasis or tissue repair. Human biological glue is also being discussed as a possible cell carrier. To date, there are only a few studies addressing the effects of fibrin glue on the cell-molecular level. This study examines the effects of fibrin glue on angiogenesis and lymphangiogenesis, as well as adipose-derived stem cells (ASCs) with a focus on gene and protein expression in scaffolds regularly used for tissue engineering approaches.

METHODS

Collagen-based dermal regeneration matrices (DRM) were seeded with human umbilical vein endothelial cells (HUVEC), human dermal lymphatic endothelial cells (LECs), or adipose-derived stem cells (ASC) and fixed with or without fibrin glue according to the experimental group. Cultures were maintained for 1 and 7 days. Finally, angiogenic and lymphangiogenic gene and protein expression were measured with special regard to subtypes of vascular endothelial growth factor (VEGF) and corresponding receptors using Multiplex-qPCR and ELISA assays. In addition, the hypoxia-induced factor 1-alpha (HIF1a) mediated intracellular signaling pathways were included in assessments to analyze a hypoxic encapsulating effect of fibrin polymers.

RESULTS

All cell types reacted to fibrin glue application with an alteration of gene and protein expression. In particular, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor B (VEGFB), vascular endothelial growth factor C (VEGFC), vascular endothelial growth receptor 1 (VEGFR1/FLT1), vascular endothelial growth receptor 2 (VEGFR2/KDR), vascular endothelial growth receptor 3 (VEGFR3/FLT4) and Prospero Homeobox 1 (PROX1) were depressed significantly depending on fibrin glue. Especially short-term fibrin effect led to a continuous downregulation of respective gene and protein expression in HUVECs, LECs, and ASCs.

CONCLUSION

Our findings demonstrate the impact of fibrin glue application in dermal regeneration with special regard to angiogenesis and lymphangiogenesis. In particular, a short fibrin treatment of 24 hours led to a decrease in gene and protein levels of LECS, HUVECs, and ASCs. In contrast, the long-term application showed less effect on gene and protein expressions. Therefore, this work demonstrated the negative effects of fibrin-treated cells in tissue engineering approaches and could affect wound healing during dermal regeneration.

Adipose-Derived Stem Cells Improve Angiogenesis and Lymphangiogenesis in a Hypoxic Dermal Regeneration Model In Vitro

Background and Objectives: Impaired wound healing represents an unsolved medical issue with a high impact on patients’ quality of life and global health care. Even though hypoxia is a significant limiting factor for wound healing, it reveals stimulating effects in gene and protein expression at cellular levels. In particular, hypoxically treated human adipose tissue-derived stem cells (ASCs) have previously been used to stimulate tissue regeneration. Therefore, we hypothesized that they could promote lymphangiogenesis or angiogenesis. Materials and Methods: Dermal regeneration matrices were seeded with human umbilical vein endothelial cells (HUVECs) or human dermal lymphatic endothelial cells (LECs) that were merged with ASCs. Cultures were maintained for 24 h and 7 days under normoxic or hypoxic conditions. Finally, gene and protein expression were measured regarding subtypes of VEGF, corresponding receptors, and intracellular signaling pathways, especially hypoxia-inducible factor-mediated pathways using multiplex-RT-qPCR and ELISA assays. Results: All cell types reacted to hypoxia with an alteration of gene expression. In particular, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor B (VEGFB), vascular endothelial growth factor C (VEGFC), vascular endothelial growth factor receptor 1 (VEGFR1/FLT1), vascular endothelial growth factor receptor 2 (VEGFR2/KDR), vascular endothelial growth factor receptor 3 (VEGFR3/FLT4), and prospero homeobox 1 (PROX1) were overexpressed significantly depending on upregulation of hypoxia-inducible factor 1 alpha (HIF-1a). Moreover, co-cultures with ASCs showed a more intense change in gene and protein expression profiles and gained enhanced angiogenic and lymphangiogenic potential. In particular, long-term hypoxia led to continuous stimulation of HUVECs by ASCs. Conclusions: Our findings demonstrated the benefit of hypoxic conditioned ASCs in dermal regeneration concerning angiogenesis and lymphangiogenesis. Even a short hypoxic treatment of 24 h led to the stimulation of LECs and HUVECs in an ASC-co-culture. Long-term hypoxia showed a continuous influence on gene expressions. Therefore, this work emphasizes the supporting effects of hypoxia-conditioned-ASC-loaded collagen scaffolds on wound healing in dermal regeneration.

Current Status of Lymphangiogenesis: Molecular Mechanism, Immune Tolerance, and Application Prospect

The lymphatic system is a channel for fluid transport and cell migration, but it has always been controversial in promoting and suppressing cancer. VEGFC/VEGFR3 signaling has long been recognized as a major molecular driver of lymphangiogenesis. However, many studies have shown that the neural network of lymphatic signaling is complex. Lymphatic vessels have been found to play an essential role in the immune regulation of tumor metastasis and cardiac repair. This review describes the effects of lipid metabolism, extracellular vesicles, and flow shear forces on lymphangiogenesis. Moreover, the pro-tumor immune tolerance function of lymphatic vessels is discussed, and the tasks of meningeal lymphatic vessels and cardiac lymphatic vessels in diseases are further discussed. Finally, the value of conversion therapy targeting the lymphatic system is introduced from the perspective of immunotherapy and pro-lymphatic biomaterials for lymphangiogenesis.

Development of a photosynthetic hydrogel as potential wound dressing for the local delivery of oxygen and bioactive molecules

The development of biomaterials to improve wound healing is a critical clinical challenge and an active field of research. As it is well described that oxygen plays a critical role in almost each step of the wound healing process, in this work, an oxygen producing photosynthetic biomaterial was generated, characterized, and further modified to additionally release other bioactive molecules. Here, alginate hydrogels were loaded with the photosynthetic microalgae Chlamydomonas reinhardtii, showing high integration as well as immediate oxygen release upon illumination. Moreover, the photosynthetic hydrogel showed high biocompatibility in vitro and in vivo, and the capacity to sustain the metabolic oxygen requirements of zebrafish larvae and skin explants. In addition, the photosynthetic dressings were evaluated in 20 healthy human volunteers following the ISO-10993-10-2010 showing no skin irritation, mechanical stability of the dressings, and survival of the photosynthetic microalgae. Finally, hydrogels were also loaded with genetically engineered microalgae to release human VEGF, or pre-loaded with antibiotics, showing sustained release of both bioactive molecules. Overall, this work shows that photosynthetic hydrogels represent a feasible approach for the local delivery of oxygen and other bioactive molecules to promote wound healing. STATEMENT OF SIGNIFICANCE: As oxygen plays a key role in almost every step of the tissue regeneration process, the development of oxygen delivering therapies represents an active field of research, where photosynthetic biomaterials have risen as a promising approach for wound healing. Therefore, in this work a photosynthetic alginate hydrogel-based wound dressing containing C. reinhardtii microalgae was developed and validated in healthy skin of human volunteers. Moreover, hydrogels were modified to additionally release other bioactive molecules such as recombinant VEGF or antibiotics. The present study provides key scientific data to support the use of photosynthetic hydrogels as customizable dressings to promote wound healing.

Towards an In Vitro 3D Model for Photosynthetic Cancer Treatment: A Study of Microalgae and Tumor Cell Interactions

As hypoxic tumors show resistance to several clinical treatments, photosynthetic microorganisms have been recently suggested as a promising safe alternative for oxygenating the tumor microenvironment. The relationship between organisms and the effect microalgae have on tumors is still largely unknown, evidencing the need for a simple yet representative model for studying photosynthetic tumor oxygenation in a reproducible manner. Here, we present a 3D photosynthetic tumor model composed of human melanoma cells and the microalgae Chlamydomonas reinhardtii, both seeded into a collagen scaffold, which allows for the simultaneous study of both cell types. This work focuses on the biocompatibility and cellular interactions of the two cell types, as well as the study of photosynthetic oxygenation of the tumor cells. It is shown that both cell types are biocompatible with one another at cell culture conditions and that a 10:1 ratio of microalgae to cells meets the metabolic requirement of the tumor cells, producing over twice the required amount of oxygen. This 3D tumor model provides an easy-to-use in vitro resource for analyzing the effects of photosynthetically produced oxygen on a tumor microenvironment, thus opening various potential research avenues.

Genetically modified organisms: adapting regulatory frameworks for evolving genome editing technologies

Genetic modification of living organisms has been a prosperous activity for research and development of agricultural, industrial and biomedical applications. Three decades have passed since the first genetically modified products, obtained by transgenesis, become available to the market. The regulatory frameworks across the world have not been able to keep up to date with new technologies, monitoring and safety concerns. New genome editing techniques are opening new avenues to genetic modification development and uses, putting pressure on these frameworks. Here we discuss the implications of definitions of living/genetically modified organisms, the evolving genome editing tools to obtain them and how the regulatory frameworks around the world have taken these technologies into account, with a focus on agricultural crops. Finally, we expand this review beyond commercial crops to address living modified organism uses in food industry, biomedical applications and climate change-oriented solutions.

In vitro and in vivo detection of microbial gene expression in bioactivated scaffolds seeded with cyanobacteria

Dermal replacement materials bioactivated with cyanobacteria have shown promising potential for wound regeneration. To date, extraction of cyanobacteria RNA from seeded scaffolds has not been described. Aim of this study was to develop a method to isolate total RNA from bioactivated scaffolds and to propose a new approach in determining living bacteria based on real-time PCR. Transgenic synechococcus sp. PCC 7002 (tSyn7002) were seeded in liquid cultures or in scaffolds for dermal regeneration in vitro and in vivo for 7 days. RNA was extracted with a 260/280 ratio of ≥ 2. The small subunit of the 30S ribosome in prokaryotes (16S) and RNAse P protein (rnpA) were validated as reference transcripts for PCR analysis. Gene expression patterns differed in vitro and in vivo. Expression of 16S was significantly upregulated in scaffolds in vitro, as compared to liquid cultures, while rnpA expression was comparable. In vivo, both 16S and rnpA showed reduced expression compared to in vitro (16S: in vivo Ct value 13.21±0.32, in vitro 12.44±0.42; rnpA in vivo Ct value 19.87±0.41, in vitro 17.75±1.41). Overall, the results demonstrate rnpA and 16S expression after 7 days of implantation in vitro and in vivo, proving presence of living bacteria embedded in scaffolds using qPCR.

Photosynthetic microorganisms for the oxygenation of advanced 3D bioprinted tissues

3D bioprinting technology has emerged as a tool that promises to revolutionize the biomedical field, including tissue engineering and regeneration. Despite major technological advancements, several challenges remain to be solved before 3D bioprinted tissues could be fully translated from the bench to the bedside. As oxygen plays a key role in aerobic metabolism, which allows energy production in the mitochondria; as a consequence, the lack of tissue oxygenation is one of the main limitations of current bioprinted tissues and organs. In order to improve tissue oxygenation, recent approaches have been established for a broad range of clinical applications, with some already applied using 3D bioprinting technologies. Among them, the incorporation of photosynthetic microorganisms, such as microalgae and cyanobacteria, is a promising approach that has been recently explored to generate chimerical plant-animal tissues where, upon light exposure, oxygen can be produced and released in a localized and controlled manner. This review will briefly summarize the state-of-the-art approaches to improve tissue oxygenation, as well as studies describing the use of photosynthetic microorganisms in 3D bioprinting technologies. STATEMENT OF SIGNIFICANCE: 3D bioprinting technology has emerged as a tool for the generation of viable and functional tissues for direct in vitro and in vivo applications, including disease modeling, drug discovery and regenerative medicine. Despite the latest advancements in this field, suboptimal oxygen delivery to cells before, during and after the bioprinting process limits their viability within 3D bioprinted tissues. This review article first highlights state-of-the-art approaches used to improve oxygen delivery in bioengineered tissues to overcome this challenge. Then, it focuses on the emerging roles played by photosynthetic organisms as novel biomaterials for bioink generation. Finally, it provides considerations around current challenges and novel potential opportunities for their use in bioinks, by comparing latest published studies using algae for 3D bioprinting.

Synthetic hydrogels engineered to promote collecting lymphatic vessel sprouting

The lymphatic vasculature is an essential component of the body's circulation providing a network of vessels to return fluid and proteins from the tissue space to the blood, to facilitate immune ce-ll and antigen transport to lymph nodes, and to take up dietary lipid from the intestine. The development of biomaterial-based strategies to facilitate the growth of lymphatics either for regenerative purposes or as model system to study lymphatic biology is still in its nascent stages. In particular, platforms that encourage the sprouting and formation of lymphatic networks from collecting vessels are particularly underdeveloped. Through implementation of a modular, poly(ethylene glycol) (PEG)-based hydrogel, we explored the independent contributions of matrix elasticity, degradability, and adhesive peptide presentation on sprouting of implanted segments of rat lymphatic collecting vessels. An engineered hydrogel with 680 Pa elasticity, 2.0 mM RGD adhesive peptide, and full susceptibility to protease degradability produced the highest levels of sprouting relative to other physicochemical matrix properties. This engineered hydrogel was then utilized as a scaffold to facilitate the implantation of a donor vessel that functionally grafted into the host vasculature. This hydrogel provides a promising platform for facilitating lymphangiogenesis in vivo or as a means to understand the cellular mechanisms involved in the sprout process during collecting lymphatic vessel collateralization.

Cerium-Containing Bioactive Glasses Promote In Vitro Lymphangiogenesis

The lymphatic system is crucial for the regeneration of many tissues due to its fundamental role in immune cell trafficking, protein transport, and tissue homeostasis maintenance. Strategies stimulating lymphangiogenesis can provide new therapeutic approaches for tissue repair and regeneration (e.g., chronic wound healing). Here, we explored the effects of cerium-containing mesoporous bioactive glass nanoparticles (Ce-MBGNs) on lymphangiogenesis. The results showed that the extracts of Ce-MBGNs (1, 5, or 10 wt/v%) were non-cytotoxic toward lymphatic endothelial cells (LECs), while they enhanced the proliferation of LECs. Moreover, as evidenced by the scratch wound healing and Transwell migration assays, conditioned media containing the extract of Ce-MBGNs (1 wt/v%) could enhance the migration of LECs in comparison to the blank control and the media containing vascular endothelial growth factor-C (VEGF-C, 50 ng/mL). Additionally, a tube-formation assay using LECs showed that the extract of Ce-MBGNs (1 wt/v%) promoted lymphatic vascular network formation. Western blot results suggested that Ce-MBGNs could induce lymphangiogenesis probably through the HIF-1α/VEGFR-3 pathway. Our study for the first time showed the effects of Ce-MBGNs on stimulating lymphangiogenesis in vitro, highlighting the potential of Ce-MBGNs for wound healing.

Development of a Novel Perfusable Solution for ex vivo Preservation: Towards Photosynthetic Oxygenation for Organ Transplantation

Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation.

Oxygenation therapies for improved wound healing: Current trends and technologies

Degree of oxygenation is one of the important parameters governing various processes, including cell proliferation, angiogenesis, extracellular matrix production, and even combating the microbial burden at the wound site, all...

When microbial biotechnology meets material engineering

Bacterial biopolymers such as bacterial cellulose (BC), alginate or polyhydroxyalkanotes (PHAs) have aroused the interest of researchers in many fields, for instance biomedicine and packaging, due to their being biodegradable, biocompatible and renewable. Their properties can easily be tuned by means of microbial biotechnology strategies combined with materials science. This provides them with highly diverse properties, conferring them non-native features. Herein we highlight the enormous structural diversity of these macromolecules, how are they produced, as well as their wide range of potential applications in our daily lives. The emergence of new technologies, such as synthetic biology, enables the creation of next-generation-advanced materials presenting smart functional properties, for example the ability to sense and respond to stimuli as well as the capacity for self-repair. All this has given rise to the recent emergence of biohybrid materials, in which a synthetic component is brought to life with living organisms. Two different subfields have recently garnered particular attention: hybrid living materials (HLMs), such as encapsulation or bioprinting, and engineered living materials (ELMs), in which the material is created bottom-up with the use of microbial biotechnology tools. Early studies showed the strong potential of alginate and PHAs as HLMs, whilst BC constituted the most currently promising material for the creation of ELMs.

A First in Human Trial Implanting Microalgae Shows Safety of Photosynthetic Therapy for the Effective Treatment of Full Thickness Skin Wounds

Insufficient oxygen supply represents a relevant issue in several fields of human physiology and medicine. It has been suggested that the implantation of photosynthetic cells can provide oxygen to tissues in the absence of a vascular supply. This approach has been demonstrated to be successful in several in vitro and in vivo models; however, no data is available about their safety in human patients. Here, an early phase-1 clinical trial (ClinicalTrials.gov identifier: NCT03960164, https://clinicaltrials.gov/ct2/show/NCT03960164) is presented to evaluate the safety and feasibility of implanting photosynthetic scaffolds for dermal regeneration in eight patients with full-thickness skin wounds. Overall, this trial shows that the presence of the photosynthetic microalgae Chlamydomonas reinhardtii in the implanted scaffolds did not trigger any deleterious local or systemic immune responses in a 90 days follow-up, allowing full tissue regeneration in humans. The results presented here represent the first attempt to treat patients with photosynthetic cells, supporting the translation of photosynthetic therapies into clinics.

Clinical Trial Registration:www.clinicaltrials.gov/ct2/show/NCT03960164, identifier: NCT03960164.