Category: Regenerative Medicine

A Novel Hydrogel for Treating Spinal Cord Injury

Photo by Kanasi on Unsplash

Researchers at the Chinese Academy of Sciences have developed an innovative scaffold that regulates the immune microenvironment following a spinal cord injury, thereby reduces secondary injury effects. Their work is reported in Biomaterials.

By modifying a hydrogel with a cationic polymer, polyamidoamine, and  interleukin-10 (IL-10; an anti-inflammatory cytokine), the scaffold could enhance tissue remodelling and promote axonal regeneration.

Spinal cord injuries cause axon damage and neural cell death, leading to dysfunction. A secondary stage of injury follows the primary stage and lasts for several weeks. Infiltration and activation of immune cells triggered by a spinal cord injury creates an inflammatory microenvironment characterised with damage-associated molecular patterns (DAMPs) that exacerbates secondary damage and impairs neurological functional recovery.

With the capabilities of effective scavenging of DAMPs and sustained release of IL-10, such a dual-functional immunoregulatory hydrogel not only reduced pro-inflammatory responses of macrophages and microglia, but also enhanced neurogenic differentiation of neural stem cells.

In a mouse model of spinal cord injury, the scaffold suppressed cytokine production, counteracting the inflammatory microenvironment and regulating immune cell activation, resulting in neural regeneration and axon growth without scar formation.

The dual-functional immunoregulatory scaffold with neuroprotection and neural regeneration effects significantly promoted electrophysiological enhancement and motor function recovery after spinal cord injury.

This study suggests that functional scaffold reconstruction of the immune microenvironment is a promising and effective method for treating severe spinal cord injury.  

Source: Chinese Academy of Sciences

Astronauts Will Test A Portable Bioprinter for Wounds

ESA astronaut Matthias Maurer is shown during preflight training for the BioPrint First Aid investigation, which tests a bioprinted tissue patch for enhanced wound healing.
Credit: ESA

A suitably advanced piece of wound care technology will be sent into orbit to the space station in the next few days: a prototype for portable bioprinter that can cover a wound area on the skin by applying a tissue-forming bio-ink that acts like a patch, and accelerates the healing process.

While the aim is to provide a effective wound treatment for astronauts millions of kilometres from the nearest hospital, such a personalised wound healing patch would also have a great benefit on Earth. Since the cultured cells are taken from the patient, immune system rejection is unlikely, allowing a safe regenerative and personalised therapy. Other advantages are the possibilities of treatment and greater flexibility regarding wound size and position. In addition, due to its small size and portability, physicians could take the device anywhere to an immobile patient if their cells were cultivated in advance.

“On human space exploration missions, skin injuries need to be treated quickly and effectively,” said project manager Michael Becker from the German Space Agency. “Mobile bioprinting could significantly accelerate the healing process. The personalised and individual bioprinting-based wound treatment could have a great benefit and is an important step for further personalised medicine in space and on Earth.”

The use of bioprinting for skin reconstruction following burns is one growing application for the technology. However, it presently requires large bioprinters that first print the tissue, allow it to mature, before it is implanted onto the patient. By testing it in the gravity-free environment of space, Bioprint FirstAid will help optimise of bioprinting materials and processes. Microgravity-based 3D tissue models are important for greater understanding of the bioengineering and bio-fabrication requirements that are essential to achieve highly viable and functional tissues. Under microgravity conditions, the pressure of different layers containing cells is absent, as well as the potential sedimentation effect of living cell simulants. The stability of the 3D printed tissue patch, and the potentially gravity-dependent (electrolyte to membrane interface) crosslinking process, can be analysed for future applications.

The Bioprint FirstAid prototype contains no cells at this point. The surprisingly simple prototype is a robust, purely mechanical handheld bioprinter consisting of a dosing device in the handle, a print head, support wheels, and an ink cartridge. The cartridge contains a substitution (in total two different substitutions, both without skin cells) and a crosslinker, which serves as a stabilising matrix. To test it out, the simulant will be applied to the arm or leg of a crew member wrapped in foil, or alternatively at any other surface wrapped in foil. On Earth, a printed sample with human cells will be tested, and the distribution pattern will be compared to the cell-free sample that was printed in space.

Source: NASA

A Review of Progress Toward Heart Muscle Regeneration

Photo from Olivier Collett on Unsplash
Photo from Olivier Collett on Unsplash

Twenty years ago, clinicians first attempted to regenerate a failing human heart by injecting muscle myoblasts into the heart during a bypass operation. Despite high initial hopes and multiple studies since then, attempts to remuscularise an injured heart have met with little, if any, success.

Yet, there is hope that a therapy will be developed, according to experts in a Journal of the American College of Cardiology state-of-the-art review. The challenge is this: A heart attack kills heart muscle cells, leading to a scar that weakens the heart, often causing eventual heart failure. The lack of muscle repair is due to the very limited ability of mammalian heart muscle cells to proliferate, except during a brief period around birth.

In the review, the experts focus on three topics. First are several recent clinical trials with intriguing results. Second is the current trend of using cell-derived products like exosomes rather than muscle cells to treat the injured heart. For the third topic, authors discuss likely future experiments to replace a myocardial scar with heart muscle cells by ‘turning back the clock’ of the existing cardiomyocytes, rather than trying to inject exogenous cells. These efforts try to reverse the inability of mature mammalian heart muscle cells to proliferate.

Clinical trials
One of the clinical trials reviewed involved giving cardiosphere-derived cells to patients with Duchenne muscular dystrophy, which affects both heart and skeletal muscles.

Cardiosphere-derived cells are a type of heart stromal/progenitor cell that has potent immunomodulatory, antifibrotic and regenerative activity in both diseased hearts and skeletal muscle. The HOPE-2 trial gave repeated intravenous doses of cardiosphere-derived cells to patients with advanced Duchenne disease, most of whom were unable to walk. Preliminary results showed safety, as well as major improvements in heart parameters such as left ventricle ejection fraction and reduced left ventricle size.

The HOPE-2 trial evaluated a repeated sequential dosing regimen of cell therapy for any cardiac indication, evaluated intravenous cardiosphere-derived administration, and clinically benefitted Duchenne patients.

Two features of the trial may bode well: a move away from invasive cardiac-targeted cell delivery and toward easily administered intravenous cell delivery, and the use of sequential repeated cell doses.

Cell-derived products
Few cells transplanted into the heart survive, though some functional benefits in heart performance have been seen despite physical clearance of grafted cells. It could be possible that the cells were acting not as replacements but rather boosters of endogenous repair pathways through the release of a wide array of tissue-repairing biomolecules.
This led to investigation of using cell-derived products rather than transplanting cells. Most of these biomolecules – proteins and non-coding nucleic acids – are enclosed in tiny vesicles that cells release naturally. When the vesicles, including exosomes, merge into recipient cells, the biomolecules can modulate signaling pathways. Using vesicles or exosomes involves a simpler manufacturing process compared with live cells, the ability to control quality and potency, and being able to refrigerate the vesicles to make administration simpler.

An alternative approach to the vesicle cell-derived products was the finding that injected stem cells can promote cardiac repair through release of biologically active molecules acting as short-range, paracrine hormones. These molecules are distinct from the biomolecules in vesicles or exosomes.

However, before use of any of these cell-derived products for heart repair in early trials, the reviewers say, more experiments are needed in purification of the products, potential modes of delivery and the suitability of repeated doses.

Proliferation of endogenous heart cells
The final review topic looked ahead toward endogenous generation of cardiomyocytes – in other words, forcing existing native cardiomyocytes to divide, or other cells to become cardiomyocytes.

Pigs can regenerate heart muscle for only a few days after birth. But in one remarkable study, researchers injured the heart by removing part of the apex of the left ventricle one day after birth, and then induced heart attack 28 days after birth. Control pigs without the Day 1 resection showed no repair of heart attack damage at Day 56. In contrast, the pigs that had a resection one day after birth, and then had experimental heart attacks at Day 28, showed heart repair by Day 56 – notably an absence of dead heart muscle, known as an infarction. Furthermore, these pigs had more cardiomyocytes throughout their left ventricles.

This study showed that heart muscle cells in large mammals can be induced to proliferate and regenerate by inducing a heart injury at Day 1 to extend the neonatal regneration window. “If this cardiomyocyte cell-cycle activation can be activated in neonates, the same signaling pathways may be activated in adults as well,” the authors wrote, “which is highly impactful and significant.”

Another possible approach to endogenous generation is the direct programming of cardiac fibroblasts into cardiomyocytes. Inducing proliferation of cardiomyocytes will also need ways to promote growth of heart blood vessels to supply the new cardiomyocytes.

In conclusion, the authors believe that short-term approaches to clinical trials of post heart-attack therapies will use cells like cardiospheres or cell products. The longer-term approach, the reviewers said, will target “a more direct remuscularisation of the injured left ventricle by ‘turning back the clock’ of the cardiomyocyte cell-cycle or generating new cardiomyocytes from other cell types such as fibroblasts.”

“However, the efficiency and safety of these strategies, particularly their ability to generate cardiomyocytes seamlessly coupled with their native counterparts and to allow a regulation of these induced proliferative events preventing an uncontrolled and harmful cardiac growth, still need to be appropriately addressed before moving to clinical applications.”

Source: University of Alabama at Birmingham

New Wound Dressing Minimises Scarring

Photo by Diana Polekhina on Unsplash
Photo by Diana Polekhina on Unsplash

A new wound dressing technology that can stop bleeding while preventing infection and scarring using a single material, has been developed. This technology also has potential applications in drug delivery, among other areas.

“Scarring is one of the worst consequences of severe wounds,” said Xiaoyang Wu, an associate professor in the Ben May Department of Cancer Research at the University of Chicago, noting that scar tissue formation is particularly common in human skin.

The researchers used a material science approach to develop a new method to overcome scarring, by impeding collagen synthesis by blocking transforming growth factor beta (TGF-β) – a cytokine that plays an important role in cell signaling, both in skin wound repair and tissue fibrosis.

“Increasing evidence suggests TGF-β is important in early phase wound repair for wound closure. But, later on, the signal may promote and enhance scarring,” Prof Wu said. This makes timing crucial. “We cannot simply block the signal, because that would slow down wound healing and would be dangerous for the patient,” he explained.

To get around this, the researchers came up with a delayed-release system combining a sutureless wound closure hydrogel material with a biodegradable microcapsule system, enabling them to control the release of the TGF-β inhibitor. “In this way, we can enhance skin wound repair and after 7-14 days can release the inhibitor that blocks the skin scarring process at the same time by using one material,” Prof Wu added.

The study results were recently published in Nature Communications.

At present, treatment of scarring is not ideal with little besides cosmetic surgery, and little can be done to prevent scar formation if a patient experiences a deep or messy wound. “The system we developed is very convenient for application,” said Wu, adding that the system has many possible future applications, such as drug delivery.

“We believe the novel system will have potential clinical importance in the future,” he said. To this end, the next steps include filing an investigational new drug (IND) application with the US Food and Drug Administration (FDA). Consistent manufacturing of the material is necessary and the researchers are exploring collaborations with pharmaceutical companies to move the research forward.

Since the system is a biocompatible material with adhesive properties, Wu said it has internal applications as well, adhering to and closing bleeding arteries and cardiac walls after irradiation with UV light. This was demonstrated in animal models, suggesting significant advantages as a traumatic wound sealant.

“Normal wound binding material does work well,” said Wu, noting that fibres are the most reliable material currently available, which, like surgical glue, is less biocompatible. “Biocompatibility is a significant advantage of our system,” he explained, “It is superior compared to current existing materials.”

Source: University of Chicago

Chemical Fingerprints Improve Stem Cell Production

Photo by Louis Reed on Unsplash

Researchers in Japan have developed a new, noninvasive way to monitor the tricky art of stem cell production.

The current era of ethical stem cell research was ushered in by the 2012 Nobel prize-winning discovery that ordinary cells could be coaxed to revert to their earliest pluripotent stage ushered in. Suddenly, scientists could have an ethical, near-inexhaustible supply of pluripotent stem cells — the most versatile of stem cells — that can become any type of cell much like how embryonic stem cells function.

These reprogrammed cells called induced pluripotent stem cells (or iPS cells) hold great promise for regenerative medicine, where they can be used to develop tissue or organ replacement-based treatments for life-threatening diseases.

One key challenge is that it is a lengthy and delicate process to artificially induce ordinary cells to reset back to pluripotency. Obtaining iPS cells therefore is a matter of chance. However, knowing all they can about the complex chemical changes happening inside during reprogramming can help scientists increase the chances of successfully obtaining viable iPS cells for clinical applications. Current methods that track reprogramming status, however, use destructive and costly techniques.

A study led by Dr Tomonobu Watanabe, professor at Hiroshima University’s Research Institute for Radiation Biology and Medicine, showed that Raman spectroscopy could be a low-cost, simpler, and non-intrusive technique to monitor the cell’s internal environment as it transitions.

Dr Watanabe explained: “The quality evaluation and sorting of existing cells have been carried out by investigating the presence or absence of expression of surface marker genes. However, since this method requires a fluorescent antibody, it is expensive and causes a problem of bringing the antibody into the cells.”

He added that the “solution of these problems can accelerate the spread of safe and low-cost regenerative medicine using artificial tissues. Through our method, we provide a technique for evaluating and sorting the quality of iPS cells inexpensively and safely, based on scattering spectroscopy.”

Raman spectroscopy is an alternative to invasive approaches that require dyes or labels to extract biochemical information. It instead makes use of vibration signatures produced when light beams interact with chemical bonds in the cell. Since each chemical has its own distinct vibration frequency, scientists can use it to identify the cell’s molecular makeup.

The team used this spectroscopic technique to get the “chemical fingerprints” of mouse embryonic stem cells, the neuronal cells they specialised into, and the iPS cells formed from those neuronal cells. These data were then used to train an AI model to can track the reprogramming is progressing, and verify iPS cell quality by checking for a “fingerprint” match with the embryonic stem cell.

To measure the progress, they assigned the “chemical fingerprint” of neuronal cells as the transformation starting point and the embryonic stem cell’s patterns as the desired end goal. Along the axis, they used “fingerprint” samples collected on days 5, 10, and 20 of the neuronal cells’ reprogramming as reference points on how the process is advancing.

“The Raman scattering spectrum contains comprehensive information on molecular vibrations, and the amount of information may be sufficient to define cells. If so, unlike gene profiling, it allows for a more expressive definition of cell function,” Dr Watanabe said.

“We aim to study stem cells from a different perspective than traditional life sciences.”

Source: Hiroshima University

Journal information: Germond, A., et al. (2020) Following Embryonic Stem Cells, Their Differentiated Progeny, and Cell-State Changes During iPS Reprogramming by Raman Spectroscopy. Analytical Chemistry doi.org/10.1021/acs.analchem.0c01800.