Fast isolation and expansion of multipotent cells from adipose tissue based on chitosan-selected primary culture.

Adipose-derived adult stem cells (ASCs) have gained much attention because of their multipotency and easy access. Here we describe a novel chitosan-based selection (CS) system instead of the conventional plastic adherence (PA) to obtain the primary ASCs. The minimal amount of adipose tissue for consistent isolation of ASCs is reduced from 10 mL to 5 mL. The selection is based on the specific interaction between cells and chitosan materials, which separate ASCs by forming spheroids during primary culture. The primary culture period was reduced from 4 days to one day and more ASCs (ten-fold expansion) were achieved in a week. The average duration for obtaining 1 × 10(7) cells takes about seven days from 5 mL of adipose tissue, compared to 14 days using the conventional PA method from 10 mL of adipose tissue. The replicative senescence of CS-ASCs is not evident until the fifteenth passage (vs. eighth for the PA-ASCs). The obtained ASCs (CS-ASCs) have less doubling time for the same passage of cells and show greater stemness than those obtained from the conventional PA method (PA-ASCs). Moreover, CS-ASCs undergo trilineage differentiation more effectively than PA-ASCs. The greater differentiation potential of CS-ASCs may be associated with the enrichment and maintenance of CD271 positive cells by chitosan selection of primary culture.

Effect of dentin bonding agent diffusing through dentin slices on the reactive oxygen species production and apoptosis of pulpal cells.

BACKGROUND/PURPOSE: Dentin bonding agents (DBAs) are cytotoxic to dental pulp cells. This study aimed to evaluate the effects of three DBAs (Optibond Solo Plus, Op; Clearfil SE Bond, SE; and Xeno III, Xe) after diffusion through 0.2-mm or 0.5-mm dentin slices on reactive oxygen species (ROS) production and apoptosis in dental pulp cells. METHODS: The amounts of DBAs diffusing through 0.2-mm or 0.5-mm dentin slices were quantified using a UV-Vis spectrophotometer. The effects of diffused DBAs on ROS production and viability of dental pulp cells were investigated using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay on Days 1 and 2. Flow cytometric analysis and double staining of treated dental pulp cells with Annexin V-fluorescein isothiocyanate (V-FITC) and propidium iodide (PI) were performed on Day 2. RESULTS: Xe showed greatest diffusion through dentin slices after 8-hour period, followed by SE and Op. Dental pulp cells produced a lesser amount of ROS, when treated with DBAs diffusing through a 0.5-mm dentin slice than through a 0.2-mm dentin slice for the same period of time. A small proportion of cells were TUNEL-positive after treatment with any of the three diffused DBAs. Annexin V-FITC/PI staining identified apoptotic cells; cell survival was higher in those cells treated with DBAs diffusing through a 0.5-mm dentin slice than through a 0.2-mm dentin slice. CONCLUSION: The three DBAs after diffusion through 0.2- or 0.5-mm dentin slice still exhibit cytotoxicity to dental pulp cells. However, the 0.5-mm dentin slice is found to be a better barrier than the 0.2-mm dentin slice to protect dental pulp cells from DBA-induced cytotoxicity.

Efficient gene silencing in mesenchymal stem cells by substrate-mediated RNA interference.

We described a novel substrate-mediated RNA interference (RNAi) technology to investigate the effect of neural crest marker expression on the multipotency of human gingival fibroblasts (HGFs). HGFs showed significantly higher neural and chondrogenic differentiation potentials compared with adult bone-marrow-derived mesenchymal stem cells and stem cells from human exfoliated deciduous teeth. By sending target-specific RNAi agents with the conventional vehicle (PolyFect), we observed that the multipotency of HGFs was closely associated with the expression of neural crest marker gene Forkhead box D3 (FoxD3). Using the novel chitosan substrate-mediated method, we successfully delivered short-hairpin RNA constructs to HGFs grown on chitosan without the use of conventional vehicles. The delivery efficiency measured by flow cytometry showed a 10-fold increase for HGFs on chitosan versus those on culture dish, and the cell viability was >95%. Moreover, HGFs with FoxD3 gene knockdown did not form spheroids on chitosan. Based on this working principle, we further selected the gene-silenced population from HGFs. The nonsilenced HGFs showed much higher neural differentiation ability with the nestin expression 40-fold greater than FoxD3-silenced population after induction, suggesting the feasibility of the method to silence genes. The new substrate-mediated gene silencing platform that combines the use of substrate and RNAi can be used to clarify the functions of important genes without suffering the toxicity.

The substrate-dependent regeneration capacity of mesenchymal stem cell spheroids derived on various biomaterial surfaces.

Mesenchymal stem cells (MSCs) are widely used for their self-renewal and multipotent abilities, which can be further enhanced by growing MSCs as three-dimensional (3D) cellular spheroids on certain substrates. Although various surfaces have been used to generate 3D MSC spheroids, the answer to whether all these spheroids have similar in vitro and in vivo properties remains unclear. In this study, adipose-derived adult stem cells (ADSCs) were cultured on a non-adherent Petri dish, polyvinyl alcohol, chitosan (CS), or chitosan-hyaluronan (CS-HA) to form 3D spheroids. The expression of the cell adhesion molecule, N-cadherin, was analyzed by qRT-PCR and Western blotting. The functional migration ability was tested using the transwell assay. The capacity for chondral regeneration of various ADSC spheroids was further evaluated in a rabbit model. We demonstrated that ADSC spheroids derived on the CS or CS-HA surface had the greater expression of N-cadherin and better migration ability. The latter was consistent with the higher expression levels of chemokine/receptor SDF-1/CXCR4 for the spheroids derived on CS or CS-HA. Animal studies also revealed significantly better cartilage repair in defects loaded with CS- or CS-HA-derived spheroids. In particular, CS-HA-derived spheroids gave rise to the best regeneration when combined with a 3D printed scaffold. This study suggested that MSC spheroids derived on different surfaces may have distinct in vitro and in vivo properties, which appeared to be associated with the surface-bound calcium as well as the calcium-dependent N-cadherin and CXCR4 signaling. The substrate-dependent properties may eventually lead to different regeneration capacities of various MSC spheroids in vivo.

Substrate-dependent Wnt signaling in MSC differentiation within biomaterial-derived 3D spheroids.

A unique biomaterial-based system was developed to generate dynamic three-dimensional (3D) multicellular spheroids of mesenchymal stem cells (MSCs). MSCs were cultured on transparent membranes made of chitosan or those further grafted with hyaluronan (HA) in different densities. MSCs vigorously migrated and were self-assembled into highly mobile 3D spheroids with substrate-dependent upregulation of adhesion molecule N-cadherin. MSC spheroids showed increased expression of Wnt genes/proteins and substrate-dependent cell fate. The correlation of differentiation capacities with Wnt signaling and crosstalk with other pathways such as ERK1/2 or Smad2/3 were observed for MSC spheroids but not for the conventional 2D cultured cells. Wnt3a-mediated canonical Wnt signaling was more active for MSC spheroids derived on chitosan, which were prone to osteogenesis. Wnt5a-mediated non-canonical Wnt signaling was more active for MSC spheroids derived on HA-grafted chitosan, which were prone to chondrogenesis. In particular, the relative importance of Wnt5a-mediated non-canonical vs. Wnt3a-mediated canonical Wnt signals in determining the cell fate was controlled by the grafting density of HA on chitosan. Treatment with the inhibitor of canonical Wnt-associated signaling molecules suppressed the osteogenesis of MSC spheroids on chitosan. This study demonstrates that Wnt signaling of MSCs is distinct in 3D environment and is substrate-dependent. The convenient 3D platform may be used to examine the role of Wnt signaling in controlling MSC fate under different extracellular environments, and potentially applied to study stem cell behavior in regenerative medicine, normal development, and cancer.

Sciatic nerve regeneration by cocultured Schwann cells and stem cells on microporous nerve conduits.

Cell transplantation is a useful therapy for treating peripheral nerve injuries. The clinical use of Schwann cells (SCs), however, is limited because of their limited availability. An emerging solution to promote nerve regeneration is to apply injured nerves with stem cells derived from various tissues. In this study, different types of allogeneic cells including SCs, adipose-derived adult stem cells (ASCs), dental pulp stem cells (DPSCs), and the combination of SCs with ASCs or DPSCs were seeded on nerve conduits to test their efficacy in repairing a 15-mm-long critical gap defect of rat sciatic nerve. The regeneration capacity and functional recovery were evaluated by the histological staining, electrophysiology, walking track, and functional gait analysis after 8 weeks of implantation. An in vitro study was also performed to verify if the combination of cells led to synergistic neurotrophic effects (NGF, BDNF, and GDNF). Experimental rats receiving conduits seeded with a combination of SCs and ASCs had the greatest functional recovery, as evaluated by the walking track, functional gait, nerve conduction velocity (NCV), and histological analysis. Conduits seeded with cells were always superior to the blank conduits without cells. Regarding NCV and the number of blood vessels, conduits seeded with SCs and DPSCs exhibited better values than those seeded with DPSCs only. Results from the in vitro study confirmed the synergistic NGF production from the coculture of SCs and ASCs. It was concluded that coculture of SCs with ASCs or DPSCs in a conduit promoted peripheral nerve regeneration over a critical gap defect.

Isolation of the multipotent MSC subpopulation from human gingival fibroblasts by culturing on chitosan membranes.

Literature has different opinions regarding the percentage of mesenchymal stem cell (MSC)-like population in human gingival tissue. Isolation of these cells is thus important for clinical applications. In this study, two typical but distinct types of gingival fibroblasts (GF), GF-A and GF-B, were grown from human gingival biopsies. They were characterized for surface markers by flow cytometry as well as the expressions of stemness and neural crest marker genes by RT-PCR. The two types of GF were slightly different in their surface markers; however, they had dramatic difference in the expression levels of stemness marker genes and neural crest marker genes. They also demonstrated distinct differentiation capacity. Upon the appropriate induction, GF-A were capable of osteogenic, adipogenic, chondrogenic, and neurogenic differentiation while GF-B only underwent osteogenic differentiation. By culturing either type of GF on chitosan membranes for 24 h, we were able to isolate two distinct subpopulations in each type of GF, i.e. cells with spheroid-forming ability (GF-AS and GF-BS) or those remained flat and attached (GF-AN and GF-BN). We further characterized these cells, and determined the common properties shared by the spheroid-forming subpopulation "S", as well as those shared by the non-spheroid-forming subpopulation "N". The subpopulation "S" was capable of the multilineage differentiation, while the subpopulation "N" was only efficient in osteogenic differentiation. GF-A and GF-B had different proportions of subpopulations. Chitosan as the cell culture substratum up-regulated the N-cadherin expression of the "S" but not "N" subpopulation, which may account for the cell sorting effect. This study showed that chitosan membranes could be used for isolation of the spheroid forming subpopulation in human GF that contained multipotent adult stem cells of which the number varied among donors and sites.

Enhanced chondrogenic differentiation potential of human gingival fibroblasts by spheroid formation on chitosan membranes.

Human gingival fibroblasts (HGF) were recently found to be a source of mesenchymal stem cells. Their behavior on a biomaterial has not been reported so far. The effect of culturing HGF on chitosan membranes on their chondrogenic differentiation was investigated in this study. HGF were first cultured on chitosan membranes and spheroid formation of HGF was observed. Next, HGF on chitosan were induced with chondrogenesis induction medium and their chondrogenic differentiation potential was expressed by assessing the expression of chondrogenesis related genes at both mRNA and protein levels by reverse transcription-polymerase chain reaction (RT-PCR) and immunostaining, respectively. We discovered that the chondrogenic differentiation potential of HGF could be enhanced simply by culturing HGF on chitosan membranes. Expression of neural crest and stemness genes were also analyzed by RT-PCR to evaluate the stemness and self-renewal of HGF spheroids. We found that spheroid formation helped to increase and maintain the expression of stemness genes in HGF. To understand the aspects of the chitosan membranes that induced spheroid formation of HGF, mechanical and physical properties of the chitosan membranes were examined. The migration of HGF on chitosan membranes was also monitored to speculate the process of spheroid formation. In addition, the roles of the Rho/Rho-associated kinase (ROCK) pathway and connexin 43 (Cx43) in spheroid formation were explored. Treatment of HGF cultured on chitosan with the ROCK-activity inhibitor Y27632 clearly inhibited spheroid formation, suggesting that the Rho/ROCK pathway was involved in spheroid formation. The increased Cx43 activity of HGF spheroids on chitosan indicated that the gap junction intercellular communication was regulated by spheroid formation. It was concluded that culturing HGF on chitosan may activate the Rho/ROCK pathway, which led to spheroid formation and gap junction regulation. These changes may contribute to the enhanced chondrogenic differentiation potential of HGF on chitosan.

Spheroid formation of mesenchymal stem cells on chitosan and chitosan-hyaluronan membranes.

Stem cells can lose their primitive properties during in vitro culture. The culture substrate may affect the behavior of stem cells as a result of cell-substrate interaction. The maintenance of self-renewal for adult human mesenchymal stem cells (MSCs) by a biomaterial substrate, however, has not been reported in literature. In this study, MSCs isolated from human adipose (hADAS) and placenta (hPDMC) were cultured on chitosan membranes and those further modified by hyaluronan (chitosan-HA). It was observed that the MSCs of either origin formed three-dimensional spheroids that kept attached on the membranes. Spheroid formation was associated with the increased MMP-2 expression. Cells on chitosan-HA formed spheroids more quickly and the size of spheroids were larger than on chitosan alone. The expression of stemness marker genes (Oct4, Sox2, and Nanog) for MSCs on the materials was analyzed by the real-time RT-PCR. It was found that formation of spheroids on chitosan and chitosan-HA membranes helped to maintain the expression of stemness marker genes of MSCs compared to culturing cells on polystyrene dish. The maintenance of stemness marker gene expression was especially remarkable in hPDMC spheroids (vs. hADAS spheroids). Blocking CD44 by antibodies prevented the spheroid formation and decreased the stemness gene expression moderately; while treatment by Y-27632 compound inhibited the spheroid formation and significantly decreased the stemness gene expression. Upon chondrogenic induction, the MSC spheroids showed higher levels of Sox9, aggrecan, and collagen type II gene expression and were stained positive for glycosaminoglycan and collagen type II. hPDMC had better chondrogenic differentiation potential than hADAS upon induction. Our study suggested that the formation of adhered spheroids on chitosan and chitosan-HA membranes may sustain the expression of stemness marker genes of MSCs and increase their chondrogenic differentiation capacity. The Rho/Rho-associated kinase (ROCK) signaling pathway may be involved in spheroid formation.