BackgroundMesenchymal stem cells (MSCs) have the potential to differentiate into specialized cell lineages such as osteoblasts and adipocytes in vitro. There exists a reciprocal relationship between osteogenic and adipogenic differentiation of MSCs that an osteogenic phenotype occurs at the expense of an adipogenic phenotype and vice versa, which in turn influence one another’s phenotype through negative feedback loops. Thus, it is important to understand what signaling molecules modulate the lineage commitment of MSCs. Protein kinase C (PKC) plays a central role in cellular signal transduction for mediating diverse biological functions, and dysregulation of PKC activity is involved in various metabolic diseases including cancer, diabetes, and heart disease. Although the role of individual PKC isoforms has been investigated in various fields, the potential role of PKC in bone metabolism is not completely understood. In this study, we investigated the potential role of PKCδ in osteogenic lineage commitment of human bone marrow-derived mesenchymal stem cells (hBMSCs).ResultsWe observed that expression and phosphorylation of PKCδ were increased during osteogenic differentiation of hBMSCs. Pharmacological inhibition and genetic ablation of PKCδ in hBMSCs resulted in a significant attenuation of osteogenic differentiation as evidenced by reduced ALP activity and ECM mineralization, as well as down-regulation of the expression of osteoblast-specific genes. These effects were also accompanied by induction of adipogenic differentiation and up-regulation of the expression of adipocyte-specific genes involved in lipid synthesis in osteogenic induction of hBMSCs. Additionally, the activation of AMPK, which is a key cellular energy sensor, induced osteogenesis of hBMSCs. However, the inhibition of AMPK activity by compound C did not affect the activation of PKCδ at all, indicating that there is no direct correlation between AMPK and PKCδ in osteogenesis of hBMSCs.ConclusionsThese results suggest that PKCδ is a critical regulator for the balance between osteogenesis and adipogenesis of hBMSCs and thus has a potential novel therapeutic target for the treatment of metabolic bone diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12860-014-0042-4) contains supplementary material, which is available to authorized users.

Resistance against tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death of cancer cells is a major obstacle in clinical application of TRAIL. Variable response to TRAIL of gastric cancer cells, synergy of TRAIL with bortezomib and potential mechanisms behind the phenomena were investigated in this study. The response to TRAIL varied among six gastric cancer cell lines, which correlated with the expression of apoptotic TRAIL receptors. Analysis of TCGA gene expression data showed that DR4 expression correlated with DR5 in gastric cancer. Although higher expression of DR4 was significantly associated with lower T, N and TNM stages, neither DR4 nor DR5 expression meaningfully influenced overall survival rate. Combined treatment of TRAIL with bortezomib resulted in strong synergistic response with enhanced activation of caspases-8,-9 and-3, and increased Annexin V-binding cell fractions in TRAIL-resistant SNU-216 cells. Bortezomib increased the expression of p21 cip1/waf1 , but p21 cip1/waf1 silencing did not restore cell viability significantly. Bortezomib also increased DR5 expression and knockdown of DR5 expression significantly recovered cell viability reduced by the combination treatment. Bortezomib decreased phosphorylation of ERK1/2, but increased that of JNK. Treatment with either an ERK1/2 inhibitor U0126 or a JNK inhibitor SP600125 rescued SNU-216 from dying of bortezomib or combined treatment. However, upregulation of DR5 by bortezomib was knocked down only by inhibition of ERK1/2 activation significantly, but not by JNK activity inhibition. In summary, upregulation of DR5 by bortezomib is of critical significance in the synergy of bortezomib with TRAIL in apoptosis of TRAIL-resistant SNU-216 and that activity of ERK1/2 is required in the bortezomib-induced DR5 overexpression.

The expression of pluripotency factors, and their associations with clinicopathological parameters and drug response have been described in various cancers, including gastric cancer. This study investigated the association of pluripotency factor expression with the clinicopathological characteristics of gastric cancer patients, as well as changes in the expression of these factors upon the stem cell-enriching spheroid culture of gastric cancer cells, regulation of sphere-forming capacity, and response to cisplatin and TRAIL treatments by Nanog and KLF4. Nanog expression was significantly associated with the emergence of a new tumor and a worse prognosis in gastric cancer patients. The expression of the pluripotency factors varied among six gastric cancer cells. KLF4 and Nanog were expressed high in SNU-601, whereas SOX2 was expressed high in SNU-484. The expression of KLF4 and SOX2 was increased upon the spheroid culture of SNU-601 (KLF4/Nanog-high) and SNU-638 (KLF4/Nanog-low). The spheroid culture of them enhanced TRAIL-induced viability reduction, which was accompanied by the upregulation of death receptors, DR4 and DR5. Knockdown and overexpression of Nanog in SNU-601 and SNU-638, respectively, did not affect spheroid-forming capacity, however, its expression was inversely correlated with DR4/DR5 expression and TRAIL sensitivity. In contrast, KLF4 overexpression in SNU-638 increased spheroid formation, susceptibility to cisplatin and TRAIL treatments, and DR4/DR5 expression, while the opposite was found in KLF4-silenced SNU-601. KLF4 is supposed to play a critical role in DR4/DR5 expression and responses to TRAIL and cisplatin, whereas Nanog is only implicated in the former events only. Direct regulation of death receptor expression and TRAIL response by KLF4 and Nanog have not been well documented previously, and the regulatory mechanism behind the process remains to be elucidated.

Frailty, a specific condition of increased vulnerability and reduced general health associated with aging in older people, is an emerging problem worldwide with major implications for clinical practice and public health. Recent preclinical and clinical studies have supported the safety of mesenchymal stem/stromal cells (MSCs) in the treatment of frailty. Comprehensive study is needed to assess the interrelationship between the condition of frailty and the effects of MSC-based therapy. This randomized controlled phase I/II trial aims to investigate the safety and potential therapeutic efficacy of the allogeneic administration of umbilical cord-derived MSCs (UC-MSCs) in combination with the standard treatment for frailty in Vietnam. Moreover, this study describes the rationales, study designs, methodologies, and analytical strategies currently employed in stem cell research and clinical studies. The primary outcome measures will include the incidences of prespecified administration-associated adverse events and serious adverse events. The potential efficacy will be evaluated based on improvements in frailty conditions (including those determined through a physical examination, patient-reported outcomes, quality of life, immune markers of frailty, metabolism analysis, and cytokine markers from patient plasma). This clinical trial and stem cell analysis associated with patient sampling at different time points aim to identify and characterize the potential effects of UC-MSCs on improving frailty based on the stem cell quality, cytokine/growth factor secretion profiles of UC-MSCs, cellular senescence, and metabolic analysis of patient CD3+ cells providing fundamental knowledge for designing and implementing research strategies in future studies. Clinical Trials Registration Number: NCT04919135