Stem cells from human exfoliated deciduous teeth (SHED) have mitochondrial transfer ability in stromal-derived inducing activity (SDIA) co-culture system

Stem cells from human exfoliated deciduous teeth (SHED) have stromal-derived inducing activity (SDIA): which means these stromal cells induce neural differentiation where they are used as a substratum for embryonic stem cell (ESCs) culture. Recent studies show that mitochondria or mitochondrial products, as paracrine factors, can be released and transferred from one cell to another. With this information, we were curious to know whether in the SDIA co-culture system, SHED release or donate their mitochondria to ESCs. For this purpose, before co-culture, SHED s' mitochondria and ESCs s' cell membranes were separately labeled with specific fluorescent probes. After co-culture, SHED s' mitochondria were tracked by fluorescent microscope and flow cytometry analysis. Co-culture also performed in the presence of inhibitors that block probable transfer pathways suchlike tunneling nanotubes, gap junctions or vesicles. Results showed that mitochondrial transfer takes place from SHED to ESCs. This transfer partly occurs by tunneling nanotubes and not through gap junctions or vesicles; also was not dependent on intracellular calcium level. This kind of horizontal gene transfer may open a new prospect for further research on probable role of mitochondria on fate choice and neural induction processes.

In vitro spatially organizing the differentiation in individual multicellular stem cell aggregates

With significant potential as a robust source to produce specific somatic cells for regenerative medicine, stem cells have attracted increasing attention from both academia and government. In vivo, stem cell differentiation is a process under complicated regulations to precisely build tissue with unique spatial structures. Since multicellular spheroidal aggregates of stem cells, commonly called as embryoid bodies (EBs), are considered to be capable of recapitulating the events in early stage of embryonic development, a variety of methods have been developed to form EBs in vitro for studying differentiation of embryonic stem cells. The regulation of stem cell differentiation is crucial in directing stem cells to build tissue with the correct spatial architecture for specific functions. However, stem cells within the three-dimensional multicellular aggregates undergo differentiation in a less unpredictable and spatially controlled manner in vitro than in vivo. Recently, various microengineering technologies have been developed to manipulate stem cells in vitro in a spatially controlled manner. Herein, we take the spotlight on these technologies and researches that bring us the new potential for manipulation of stem cells for specific purposes.

Bioprinting for stem cell research

Recently, there has been growing interest in applying bioprinting techniques to stem cell research. Several bioprinting methods have been developed utilizing acoustics, piezoelectricity, and lasers to deposit living cells onto receiving substrates. Using these technologies, spatially defined gradients of immobilized biomolecules can be engineered to direct stem cell differentiation into multiple subpopulations of different lineages. Stem cells can also be patterned in a high-throughput manner onto flexible implementation patches for tissue regeneration or onto substrates with the goal of accessing encapsulated stem cells of interest for genomic analysis. Here, we review recent achievements with bioprinting technologies in stem cell research, and identify future challenges and potential applications including tissue engineering and regenerative medicine, wound healing, and genomics.

Adipose tissue derived mesenchymal stem cell (AD-MSC) promotes skin wound healing in diabetic rats

AIMS

Stem cells are a new hope to ameliorate impaired diabetic wound healing. The purpose of this study was to evaluate the effect of adipose tissue derived mesenchymal stem cells (AD-MSCs) on wound healing in a diabetic rat model.

METHODS

Twenty-six rats became diabetic by a single intraperitoneal injection of streptozotocin. Six rats served as non-diabetic (non-DM). Diabetic rats were divided into two equal groups randomly; control and treatment. Six weeks later, a full-thickness circular excisional wound was created on the dorsum of each rat. AD-MSCs were injected intra-dermally around the wounds of treatment group. PBS was applied to control and non-DM groups. The wound area was measured every other day. After wound healing completion, full thickness skin samples were taken from the wound sites for evaluation of volume density of collagen fibers, length and volume density of vessels, and numerical density of fibroblasts by stereological methods.

RESULTS

AD-MSCs accelerated wound healing rate in diabetic rats, but did not increase length and volume density of the vessels and volume density of the collagen fibers. AD-MSCs decreased the numerical density of fibroblasts.

CONCLUSIONS

We concluded that AD-MSCs enhances diabetic wound healing rate probably by other mechanisms rather than enhancing angiogenesis or accumulating collagen fibers.

Embryonic stem cell bioprinting for uniform and controlled size embryoid body formation

Embryonic stem cells (ESCs) are pluripotent with multilineage potential to differentiate into virtually all cell types in the organism and thus hold a great promise for cell therapy and regenerative medicine. In vitro differentiation of ESCs starts with a phase known as embryoid body (EB) formation. EB mimics the early stages of embryogenesis and plays an essential role in ESC differentiation in vitro. EB uniformity and size are critical parameters that directly influence the phenotype expression of ESCs. Various methods have been developed to form EBs, which involve natural aggregation of cells. However, challenges persist to form EBs with controlled size, shape, and uniformity in a reproducible manner. The current hanging-drop methods are labor intensive and time consuming. In this study, we report an approach to form controllable, uniform-sized EBs by integrating bioprinting technologies with the existing hanging-drop method. The approach presented here is simple, robust, and rapid. We present significantly enhanced EB size uniformity compared to the conventional manual hanging-drop method.

One-dimensional self-assembly of mouse embryonic stem cells using an array of hydrogel microstrands

The ability of embryonic stem (ES) cells to self-renew indefinitely and to differentiate into multiple cell lineages holds promise for advances in modeling disease progression, screening drugs and treating diseases. To realize these potentials, it is imperative to study self-assembly in an embryonic microenvironment, as this may increase our understanding of ES cell maintenance and differentiation. In this study, we synthesized an array of one-dimensional alginate gel microstrands and aqueous microstrands through an SU-8 filter device by means of capillary action. Furthermore, we investigated self-assembly behaviors and differentiation potentials of mouse ES cells cultured in microstrands of varying diameters. We found that microstrands with an aqueous interior facilitated high density cell culture and formed compact microtissue structures, while microstrands with gelled interiors promote smaller cell aggregate structures. In particular, we noticed that ES cells collected from one-dimensional aqueous microstrands favored the differentiation towards cell lineages of endoderm and mesoderm, whereas those from gelled microstrands preferred to differentiate into ectoderm and mesoderm lineages. In addition to providing a "liquid-like" tubular microenvironment to understand one-dimensional self-assembly process of ES cells, this alginate hydrogel microstrand system also offers an alternative way to manipulate the stem cell fate-decision using bioengineered microenvironments.

Controlled embryoid body formation via surface modification and avidin-biotin cross-linking

Cell-cell interaction is an integral part of embryoid body (EB) formation controlling 3D aggregation. Manipulation of embryonic stem (ES) cell interactions could provide control over EB formation. Studies have shown a direct relationship between EB formation and ES cell differentiation. We have previously described a cell surface modification and cross-linking method for influencing cell-cell interaction and formation of multicellular constructs. Here we show further characterisation of this engineered aggregation. We demonstrate that engineering accelerates ES cell aggregation, forming larger, denser and more stable EBs than control samples, with no significant decrease in constituent ES cell viability. However, extended culture >/=5 days reveals significant core necrosis creating a layered EB structure. Accelerated aggregation through engineering circumvents this problem as EB formation time is reduced. We conclude that the proposed engineering method influences initial ES cell-ES cell interactions and EB formation. This methodology could be employed to further our understanding of intrinsic EB properties and their effect on ES cell differentiation.

Size of the embryoid body influences chondrogenesis of mouse embryonic stem cells

For applications in tissue engineering and regenerative medicine, embryonic stem cells (ESCs) are commonly pre-differentiated in the form of embryoid bodies (EBs). The uncontrolled cell differentiation in EBs results in a highly heterogeneous cell population, an unfavourable condition for therapeutic development. The purpose of this study was to determine an optimal size of EBs for chondrogenic differentiation. EBs were produced in suspension culture with mouse ESCs (ES-D3 GL). The 5-day-old EBs were sorted under a microscope by diameter: small EBs (S-EBs, < 100 microm), medium EBs (M-EBs, 100-150 microm) and large EBs (L-EBs, > 150 microm). The three sizes of EBs were cultured separately for 3 weeks in chondrogenic medium. Type II collagen and aggrecan gene expression was significantly upregulated in the S-EBs, when compared with the M-EBs and L-EBs (p < 0.05 and p < 0.001, respectively). Proteoglycans produced by the cells derived from S-EBs were > 50% of the other two groups. In addition, both Oct4 and Sox2 were expressed more in S-EBs than in M-EBs and L-EBs. Type X collagen expression was relatively increased in L-EBs. Slight shifts toward haematopoietic and endothelial differentiation were seen in the L- and M-EBs. In summary, the size of EBs has implications on ESC differentiation. Cells derived from S-EBs have a greater chondrogenic potential than those from M-EBs and L-EBs. The size of EBs can be a parameter utilized to optimize ESC differentiation for tissue engineering.