Decellularized feeders: an optimized method for culturing pluripotent cells.

Pluripotent cells such as human embryonic stem cells and human induced pluripotent stem cells are useful in the field of regenerative medicine because they can proliferate indefinitely and differentiate into all cell types. However, a limiting factor for maintaining and propagating stem cells is the need for inactivated fibroblasts as a growth matrix, since these may potentially cause cross-contamination. In this study, we aimed to maintain stem cells on the extracellular matrix (ECM) of either nonirradiated or γ-irradiated fibroblasts. It has been demonstrated that the ECM contains factors and proteins vital for the adhesion, proliferation, and differentiation of pluripotent cells. In order to preserve the ECM, the cell layers of the fibroblasts were decellularized by treatment with 0.05% sodium dodecyl sulfate (SDS), which resulted in an absence of DNA as compared with conventional feeder culture. However, SDS treatment did not cause a detectable change in the ECM architecture and integrity. Furthermore, immunohistochemistry demonstrated that expressions of major ECM proteins, such as fibronectin, collagen, and laminin, remained unaltered. The human pluripotent cells cultured on this decellularized matrix maintained gene expression of the pluripotency markers NANOG and OCT4 and had the potency to differentiate to three germ layers. The in vitro culture system shown here has an excellent potential since the main allogeneic components (i.e., DNA of the feeder cells) are removed. It is also a technically easy, fast, safe, and cheap method for maintaining a refined feeder-free stem cell culture for further cell differentiation studies.

Passaging techniques and ROCK inhibitor exert reversible effects on morphology and pluripotency marker gene expression of human embryonic stem cell lines.

Human embryonic stem cells (hESCs) are known for their potential usage in regenerative medicine, but also for handling sensitivity. Much effort has been put into optimizing the culture methods of hESCs. It has been shown that the use of Rho-associated coiled-coil kinase inhibitor (ROCKi) decreases the cellular stress response and the apoptotic cell death in hESC cultures that have been passaged enzymatically. These observations sparked a wide use of ROCKi in hESC cultures. We and others, however, noted that cells passaged enzymatically with the use of ROCKi had a different morphology compared to cells passaged mechanically. Here we show that hESCs that were enzymatically passaged displayed alterations in the nuclear size compared to cultures that were mechanically passaged. Notably, a dramatically decreased expression of the genes encoding common pluripotency markers, such as OCT4/POU5F1 and NANOG were revealed in enzymatically passaged hESCs compared to mechanically passaged, while such differences were not significant when assessing protein levels. The differences in gene expression did not correlate strongly with commonly analyzed histone modifications (H3K4me3, H3K9me3, H3K27me3, and H4K16ac) on the promoters of these genes. Surprisingly, the effects of enzymatic passaging were at least in part reversible as the gene expression profile of enzymatically passaged hESCs that were transferred back to mechanical passaging, showed no significant difference compared to those hESCs that were continuously passaged mechanically. Our results suggest that enzymatic passaging influences parameters associated with hESC characteristics, and emphasizes the importance of using cells handled in the same manner when comparing results both within and between projects.

Osteoadherin accumulates in the predentin towards the mineralization front in the developing tooth.

BACKGROUND: Proteoglycans (PG) are known to be involved in the organization and assembly of the extracellular matrix (ECM) prior to mineral deposition. Osteoadherin (OSAD), a keratan sulphate PG is a member of the small leucine-rich (SLRP) family of PGs and unlike other SLRPs, OSAD expression is restricted to mineralized tissues. It is proposed to have a high affinity for hydroxyapatite and has been shown to be expressed by mature osteoblasts but its exact role remains to be elucidated. METHODOLOGY/PRINCIPAL FINDINGS: We investigated the protein distribution of OSAD in the developing mouse tooth using immunohistochemistry and compared its expression with other SLRPs, biglycan (BGN), decorin (DCN) and fibromodulin (FMD). OSAD was found to be specifically localized in the predentin layer of the tooth and focused at the mineralization front. These studies were confirmed at the ultrastructural level using electron microscopy (iEM), where the distribution of immunogold labeled OSAD particles were quantified and significant amounts were found in the predentin, forming a gradient towards the mineralization front. In addition, iEM results revealed OSAD to lie in close association with collagen fibers, further suggesting an important role for OSAD in the organization of the ECM. The expression profile of mineralization-related SLRP genes by rat dental pulp cells exposed to mineralization inducing factors, showed an increase in all SLRP genes. Indeed, OSAD expression was significantly increased during the mineralization process, specifically following, matrix maturation, and finally mineral deposition. Alizarin Red S staining for calcium deposition showed clear bone-like nodules, which support matrix maturation and mineralization. CONCLUSIONS: These studies provide new evidence for the role of OSAD in the mineralization process and its specific localization in the predentin layer accumulating at the mineralization front highlighting its role in tooth development.

High-throughput protein production--lessons from scaling up from 10 to 288 recombinant proteins per week.

The demand for high-throughput recombinant protein production has markedly increased with the increased activity in the field of proteomics. Within the Human Protein Atlas project recombinantly produced human protein fragments are used for antibody production. Here we describe how the protein expression and purification protocol has been optimized in the project to allow for handling of nearly 300 different proteins per week. The number of manual handling steps has been significantly reduced (from 18 to 9) and the protein purification has been completely automated.