Towards ‘smarter’ 3D scaffolds

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In tissue engineering, the type, composition and properties of biomaterials used as scaffolds have a profound effect on the regeneration of new tissues. In the case of collagen, for example, its structure and fibrillar arrangement in vivo have a direct affect on its function – such as its ability to withstand mechanical stress – and so optimal scaffold mechanics should provide an environment that mimics the molecular arrangement of collagen fibrils.

Continued improvements in biomaterial design have been able to translate some of these structure-function relationships successfully to yield new in vivo models, and new materials have emerged that provide more optimal environments for cellular growth and tissue reconstruction.

These new “smart” scaffolds generally involve combination and hybrid materials coated with growth factors or cells for improved vascularization. The growth factors are usually chosen so that they mimic specific functions of in vivo tissue and are crucial for optimal engrafment of the implanted scaffolds and to support the function of the newly formed tissue.

The trend toward such “smart” scaffolds has created a number of novel biomaterials with promising regenerative behavior.

In a study published last week in the Proceedings of the National Academy of Sciences, a new combination scaffold, made from a combination of silk protein and a collagen-based gel, coated with rat neurons, was developed as a model of 3D brain-like tissue. The authors, led by Dr. David Kaplan of Tufts University, showed that the neurons managed to grow axons through the scaffold, which itself survived for more than two months in the lab. The authors also founds that neurons in their 3D brain-like tissue exhibited higher expression of genes involved in neuron growth and function.

Elsewhere, novel approaches for improved coating of scaffolds are being developed: researchers at the University of Colorado developed a new 3D scaffold based on PLGA coated with growth factors for controllable bone tissue regeneration. Using a layer-by-layer assembly approach, the authors coated the PLGA scaffolds with platelet-derived growth factor (PDGF) first, followed by bone morphogenetic protein 2 (BMP-2), two most important growth factors for bone repair. By coating PDGF first followed by layers of BMP-2, the authors achieved sustained release of the growth factors in a way that mimics the process of in vivo healing.

Nanotechnology is also emerging as a tool to achieve molecular structures of scaffolds closer to those of native tissue – such as the recent development of nanoparticles – published about in Scientific Reports – for the assembly of collagen scaffolds with fibrillar lamellae that resemble native lamellae.

Such examples of new 3D scaffolds emphasize the importance of combination approaches for developing next generation tissue regeneration substrates and show that scaffolds of the future will benefit multipronged development approaches.

Making IPS cells more efficient? New studies shed light on the reprogramming process

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A recent editorial in Nature highlighted the murky landscape of patenting induced pluripotent stem cell (IPSC) discoveries, ultimately concluding that patent thickets might stand as one of the central challenges to the smooth patenting of IPSC technologies. This comes on the heels of the controversial news that Dr. Shinya Yamanaka, professor at Kyoto University who shared the 2012 Nobel Prize in Physiology or Medicine with Dr. John B. Gurdon for their discovery of the ability to reprogram adult stem cells to become pluripotent, had her patent for the discovery challenged by an unknown entity called BioGatekeeper. This news is still unraveling, and little else is known about the challenger or what this will ultimately mean for the technology.

On the subject of IPS cells, two interesting papers have appeared in recent weeks which aim to improve on the technology described in Yamanaka’s patent.

One of them, by the lab of Miguel Ramalho-Santos, associate professor of obstetrics, gynecology, and reproductive sciences at University of California – San Francisco, addresses issues that commonly arise during reprogramming of adult cells and result in low reprogramming efficiency. The authors reported on the discovery of “reprogramming barriers”, in the form of genes which regulate, in their own words, transcription, chromatin regulation, ubiquitination, dephosphorylation, vesicular transport, and cell adhesion. These are, they report, disintegrin and metalloproteinase proteins. However, while these barriers appear to prevent complete reprogramming, they also appear to protect the integrity of adult cells, and have furhter protective effects. The study, titled “Systematic Identification of Barriers to Human iPSC Generation” is published in Cell.

Along similar lines, another new collaborative study published in Stem Cells Translational Medicine titled “Removal of Reprogramming Transgenes Improves the Tissue Reconstitution Potential of Keratinocytes Generated From Human Induced Pluripotent Stem Cells” by Ken Igawa’s lab at Tokyo Medical and Dental University and collaborators at Osaka university, compared the efficiency of reprogrammed human skin cells after removing reprogramming transgenes to reprogrammed cells containing the transgenes. Interestingly, after the cells were differentiated into keratinocytes, the authors observed that reprogramming material-free cells were functionally and morphologically more similar to normal human keratinocytes than cells still containing the genetic reprogramming material. The implications for clinical use are potentially significant, although further investigations should be untertaken to elucidate the exact long-term effect of the removal of such genes. Moreover, studies on additional cell lines should also be carried out and investigated.

To answer the question in the title, can we make IPS cells better? Taken together, these two studies highlight the significance of the presence of genetic material in directing reprogramming and the subsequent fate of reprogrammed cells after differentiation, and it will be interesting to see how they impact further growth of the prolific IPSC field.

 

Adipose-derived Stem Cells: Clinical Successes, Setbacks and the Controversial New Players

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Last week, Cytori Therapeutics made news when they announced they had suddenly halted their ATHENA and ATHENA II clinical trials. The company announced the news in a press release, following what it described as “safety review of reported cerebrovascular events.” The company reported that certain patients had observed complications with blood flow to the brain following administration of the therapy. The company claimed:

Symptoms occurred in three patients, of which two patients’ symptoms fully resolved within a short period of time and the third patient has had substantial resolution of symptoms.

While it is promising that two of the three patients recovered quickly, the concern is significant enough to put a dent in the proceedings (Cytori’s shares fell by more than 13% following the announcement).

The trials aim to investigate the safety and feasibility of adipose-derived stem cells for the treatment of chronic myocardial ischemia. Speaking to Forbes, Timothy Henry, the co-principal investigator of the trials, claimed that the complications were from the “use of electroanatomical mapping,” which facilitates the intervention and expressed hope for the studies to resume once issues are resolved.

Elsewhere, Bioheart announced that it had successfully completed a combination stem cell treatment using AdipoCell and MyoCell on a patient with congestive heart failure. AdipoCell are Bioheart’s proprietary adipose-derived stem cells, and the news comes on the heels of the successful clinical results on AdipoCell the company reported earlier this year.

These are two examples of the more high-profile trials approved by the FDA that have recently made headlines.

Clearly, isolating stem cells from fat is a growing industry that is expanding in multiple areas: the market for medical devices devoted to the isolation of stem cells from adipose tissue is serious business, with over a dozen companies developing products to enable more efficient isolation of such cells.

On the therapy side, the tide may be turning: Just like the two examples mentioned above indicate, treatments involving the use of adipose-derived stem cells are also growing – however, many of them are still controversial. There have been reported to be over 100 clinics currently administering stem cell treatments around the USA. Many of them, under the umbrella of the Cell Surgical Network, have attracted a lot of interest recently when their practices were brought into question. The specifics were discussed at length elsewhere, but the Network made news recently when Nature Medicine reported on the scientific community’s efforts to pressure the FDA’s Center for Biologics Evaluation and Research to investigate whether the CSN was violating federal regulations governing the administration of stem cell–based products.

Whatever the legalities end up being, we are at an intriguing point for the field of adipose-derived stem cells: both legally as well as from a scientific perspective, the tide is moving forward rapidly.

For more on these cells, we devoted a blog entry on the isolation of stem cells from adipose tissue, wherein we also introduced Matrixyme, Akron’s entry into the adipose tissue derived-stem cell arena. More to follow…

 

Vivex Biomedical and Akron Biotech Announce Collaborative Venture in Regenerative Medicine

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Akron Biotech and Vivex Biomedical, Inc. have just announced a strategic collaboration on the use of Akron’s next-generation line of cryopreservation media, CryoNovo™ in one of Vivex’ therapeutic applications.

CryoNovo™ is Akron’s brand new range of DMSO-free cryopreservation media. Developed to meet the growing needs for efficient cryopreservation of a variety of cells, the CryoNovo™ line includes three products, each tailored to a specific application:

CryoNovo™ media are DMSO-, serum- and glycerol- free. They are also non-toxic and developed from completely natural components.

In the collaboration, Akron’s CryoNovo™ T82 is used in the Vivex process of viable bone allograft preparation.

CD34+ Stem Cells Show Promise in Phase I Study for Acute Stroke

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Following a couple of bad weeks for the stem cell field – which started with a retraction of the 2008 Nature paper Generation of pluripotent stem cells from adult human testis, and culminated with the sad news of the suicide of Japanese scientist Yoshiki Sasai, one of the co-authors of the controversial – and now retracted – Nature paper on STAP cells published earlier this year – comes the refreshing news of a successful human trial of a new therapy involving stem cells for the treatment of stroke.

The results of a phase I trial, conducted at London’s Imperial College Healthcare NHS Trust, involving five patients with acute ischemic stroke, showed promising preliminary results in terms of both safety and efficacy. Immunoselected, bone marrow-derived CD34+ stem cells were isolated and used to treat five patients – selected from a potential pool of 82 candidates – by infusing the cells intra-arterially using the middle cerebral artery into the target infract area that delivers them to the brain.

The patients, all between 30 and 80 years old, were treated within one week of suffering a severe stroke. The stroke sufferers all recorded improvements over a six-month follow-up period, and three of the five patients were independent after six months despite suffering from an extremely severe type of stroke, which has a typical survival rate of <5%. Moreover, no serious side effects were recorded in any of the patients.

The study, published in Stem Cells Translational Medicine, is the first of its kind in humans. As far as the timeline goes, the study started in 2007, was completed in 2012 and results were published last week.

While preliminary, the results are very promising considering this up until this point these stem cells had only been shown to be effective for the same treatment in animal models. The authors claim further follow up studies are necessary, but that a potential drug with the same functionality as the cells is in the pipeline.

Similarly to Us, Old Age Isn’t Kind to Hematopoietic Stem Cells Either

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Always thought to be able to self-renew indefinitely, hematopietic stem cells have been considered as an important multipotent source of cells able to generate a variety of cell types within a specific tissue family. Just last week, a group of scientists led by a University of Wisconsin-Madison stem cell researcher Igor Slukvin reported on the discovery of two groups of transcriptional regulators capable of inducing distinct differentiation of hematopoietic stem cells into hemogenic endothelial cells, which subsequently develop into various types of blood cells. The Nature Communications study is the first time transcription factors have been used to product different kinds of cells from hematopoietic stem cells.

Now, however, a remarkable Nature study – titled “Replication stress is a potent driver of functional decline in ageing haematopoietic stem cells” – described hematopoietic stem cells as not quite forever self-renewing. Led by Emmanuelle Passegué at the University of California San Francisco Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, the study blamed stress as a cause for the functional decline in old hematopoietic stem cells. The reason for that is thought to be increased replication stress that occurs as a function of cell cycle defects and chromosome gaps. This results in decreased expression in mini chromosome maintenance DNA helicase, which in turn caused DNA damage and death.

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With a weakened immune system and a reduced functionality of their hematopoietic stem cells, this is ultimately the reason why old people are not donor candidates for bone marrow transplantation.

The study ultimately postulates that a drug that retains DNA helicase components to be a significant potential target for improved stem cell therapies and avoidance of immune system failure.

 

 

Akron Publishes New Collaborative Paper on Next-Generation DMSO-free cryopreservation

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A collaborative study between Akron Biotechnology and groups at Stanford University, Harvard Medical School, Worcester Polytechnic Institute and Case Western Reserve University which brings together Akron’s expertise in cryopreservation media development together with next-generation approaches for cell preservation developed at Stanford and Harvard, has been published this week in the journal Advanced Materials. The study, titled “Bio-Inspired Cryo-Ink Preserves Red Blood Cell Phenotype and Function During Nanoliter Vitrification“, is the culmination of extensive research and describes the use of novel, glycerol- and DMSO-free cryopreservation media developed at Akron for the rapid vitrification of red blood cells.

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There is a significant need for novel approaches for the preservation of red blood cells that avoid the complications that arise with the use of traditional cryoprotectants such as DMSO and glycerol. The motivation behind this study was to develop such an approach – one that retains cell morphology and function and minimizes cryoinjury that occurs to the cells during the freezing process. As seen in the figure above, the approach is based on an ejector that dispenses nanoliter-sized droplets containing red blood cells and cryoprotectant, which are then rapidly vitrified. They key to the freezing process is the presence of a robust, DMSO-free cryoprotectant based on the naturally-occuring compound ectoin, developed at Akron Biotechnology. The compound was shown to retain cellular morphology analogous to fresh, non-cryopreserved red blood cells, together with intact functionality. Using this DMSO-free vitrification approach, a post-thaw cell viability of >82% was obtained, which was significantly higher than what was obtained when DMSO was used instead. Similarly, scanning electron microscopy observations indicated the membrane morphology to resemble that of unpreserved cells after vitrification with the ectoin-based cryoprotectant. Akron has long been developing novel cryopreservation media, and this paper is the result of Akron’s committment to researching and developing more tailored solutions for cell preservation that aim to target specific cell types. The ectoin-based cryoprotectant will soon be available as a commercial product – co keep watching this space for more information. You can view the study here.