Current Tissue Engineering (Discontinued) - Volume 3, Issue 2, 2014

Millions of people suffer from tendon injuries in both occupational and athletic settings. However, the restoration of normal structure and function to injured tendons remains one of the greatest challenges in orthopaedics and sports medicine. In recent years, several advancements have been made in tendon research that suggest the potential for more effective treatment and repair of tendon injuries. First is the discovery of tendon stem/progenitor cells (TSCs). Recent studies have suggested that TSCs may be responsible for the development of degenerative tendinopathy, a chronic tendon injury. Besides, because TSCs are tendon-specific stem cells, they can potentially be used in cell therapy to effectively repair or even regenerate injured tendons. Second, autologous platelet-rich plasma (PRP) has recently been adopted in orthopaedics and sports medicine to treat acute and chronic tendon injuries. Patients treated with PRP injections have reported a significant reduction in injury-induced pain and improvement in joint function. Finally, engineered tendon scaffolds have been shown to promote tenogenesis of TSCs in animal studies in vitro and formation of tendon-like structures in vivo; hence, they may be effectively used to enhance the repair of injured tendons. In this article, a review is provided on the mechanobiology of TSCs, the efficacy of PRP treatment for tendon injuries and the applications of tendon scaffolds to treat tendon-related disorders in clinical settings. Based on the existing data, it is recommended that a multidimensional approach combining all three tissue engineering elements - TSCs, PRP and scaffolds - be used to enhance the healing of injured tendons.

Heart disease is the leading cause of death in the western world. In the future, it is predicted that heart disease will kill more people than AIDS and all types of cancers combined. Unfortunately, the adult human heart is incapable of mounting a significant regenerative response after a myocardial infarction. However, a number of different avenues of research have arisen aimed at rectifying this situation. With their ability to differentiate into functional cardiomyocytes, pluripotent stem cells offer great promise for the field of heart regeneration. If the right conditions can be found, it may be possible to graft these cells into a damaged heart to replace lost cardiomyocytes. More recently endogenous cardiac progenitor cells have also been identified which could potentially be stimulated into effecting a regenerative response. Lastly, animal models such as zebrafish and neonatal mice, in which cardiac regeneration occurs naturally via cardiomyocyte proliferation, could yield clues on how to induce this process in adults. This review will cover recent advances in these different aspects of heart regeneration with a particular highlight on endogenous regenerative mechanisms and how these could be used to trigger a similar process in adult mammals.

Stem cells possess both self-renewing and multi-lineage differentiation properties and are being explored extensively for use as a cellular therapy for regenerative medicine. Historically, replacement of lost neurons and restoration of neural circuits was primarily considered as the main mechanism by which stem cells restore function in the injured central nervous system (CNS). However, evidence is accumulating that implicates stem cell-derived trophic factors in the neuroprotection of compromised endogenous neurons and regeneration of their axons and dendrites. In this concise review, we summarise the potential of bone marrow-derived stem cells (BMSC), adipose-derived mesenchymal stem cells (AMSC), dental pulp stem cells (DPSC) and neural stem cells (NSC) to repair the injured CNS, with particular reference to spinal cord injury and optic nerve/retinal injury.

Several kinds of cell therapies have already been introduced in clinics. Inducing anti-cell death effects in prepared cells might improve the outcomes of cell therapies. A previously established technique suppressed the oxidation of coffee and maintained the freshness of vegetables using an electric current system. In the present study, we examined whether the adjusted electric current system could induce anti-cell death effects in living cells. NIH3T3 cells were cultured under regular conditions with or without treatment with the electric current system. BrdU uptake and cell counting assays revealed the electric current system did not inhibit cell proliferation. When normal cells were exposed to serum starvation, cells became apoptotic and necrotic. However, apoptosis and necrosis was prevented by the electric current system. Notably, autophagy was also induced by serum starvation, but was not prevented by the electric system. PCR array results identified a panel of anti-apoptotic genes that were upregulated in cells treated with the electric current system, including Hells, which was upregulated 400-fold in the experimental groups. In conclusion, here we demonstrated that the adjusted electric current system induced anti-apoptotic and anti-necrotic effects in living cells. The system is a simple and safe method that is easy to introduce in the clinics. These findings may contribute to further improvement of clinical cell therapies.

Controversy still exists whether ciliary body contains stem cells (CBSCs) or epithelial cells (CBECs). CBSCs were reported for differentiation capacity and CBECs for high reprogramming efficiency to produce induced Pluripotent Stem (iPS) cells. However, ciliary body derived cells (CBCs) application as a cell therapy needs a guaranteed isolation and culture protocol from ciliary body tissue strip. Four protocols were compared; one (I) belonged to a published article (Gu et al., 2007) and the rest three, protocols II, III and IV, were developed. Protocol II, III and IV used trypsin-EDTA and mechanical scraping to isolate single CBCs, basement membrane (BM) fragments and other debris. Protocols used 40 and/or 100 μm cell strainers at different steps to remove different scraped tissue fragments and isolated single CBCs. Protocol III and IV contained CBCs attached on BM. Success/failure numbers in out of 5 repeated experiments per protocol (n=5) were 2/3 (I), 3/2 (II), 4/1 (III) and 5/0 (IV). Cultures were very clean (I), partially clean (II and III) and dirty (IV). Protocol III and IV based cultures showed clumps of cell spheres. This study results confirmed that BM promotes cell proliferation and primary cell spheres formation. CBCs are in controversy for recognition as epithelial or stem cells but their successful isolation and culture, and iPS cells reprogramming protocols can open a new era for reinforcing their applicability.

The authors have previously implemented Green Fluorescent Protein (GFP) transfection as a marker to assess viability both in vitro and in vivo following freezing injury, with loss of GFP fluorescence following treatment indicating cell death. Although excellent correlations with conventional vital dyes and staining methods (membrane integrity, histology) were observed following injurious freezing, until now the basis for the loss of GFP fluorescence was not comprehensively explored. In this work it was hypothesized that membrane breach caused by freezing causes leakage of GFP. Diffusion of GFP into the extra-cellular space then causes a loss of intracellular and average fluorescent signal as the GFP is diluted and its fluorescent signal attenuated (diffusion-dilution hypothesis). A simple one-dimensional (1-D) mass diffusion equation implementing literature values of GFP diffusivity was found to adequately account for the observed time scale of GFP fluorescence attenuation in vitro. Conservation of mass was established by monitoring extracellular solution fluorescence before and after cell lysis, which is consistent with the hypothesis of simple diffusion of a stable GFP molecule from the intracellular to extracellular space. The effect of freezing on the protein, external to the cellular environment, was investigated by repeated freezing of aqueous solutions of purified recombinant protein. A significant difference (p < 0.01) in fluorescence intensity between control samples and the frozen protein solutions was not observed until the third freezethaw cycle. These results suggest that cold denaturation of the protein is not a major contributor to GFP fluorescence loss following lethal freezing of cells and that the diffusion and dilution of the fluorophore is the basis of fluorescence loss. The intracellular GFP thus functions as a membrane integrity indicator following low temperature freezing injury.