BackgroundMesenchymal stem cells (MSCs) are multipotent stem cells that are able to differentiate into several cell types, including cartilage, fat, and bone. As a common progenitor, MSC differentiation has to be tightly regulated to maintain the balance of their differentiation commitment. It has been reported that the decision process of MSCs into fat and bone cells is competing and reciprocal. Several factors have been suggested as critical factors that affect adipo-osteogenic decision, including melatonin and smad4. Yes-associated protein (YAP) is an important effector protein in the Hippo signaling pathway that acts as a transcriptional regulator by activating the transcription of the genes involved in cell proliferation and anti-apoptosis. The non-canonical role of YAP in regulating bone homeostasis by promoting osteogenesis and suppressing adipogenesis was recently demonstrated in a mouse model. However, it is unclear whether YAP is also crucial for modulating human MSC differentiation to fat and bone.MethodsThe expression level of YAP during MSC differentiation was modulated using pharmaceutical molecule and genetic experiments through gain- and loss-of-function approaches.ResultsWe demonstrated for the first time that YAP has a non-canonical role in regulating the balance of adipo-osteogenic differentiation of human MSCs. The result from synchrotron radiation-based Fourier transform infrared (FTIR) microspectroscopy showed unique metabolic fingerprints generated from YAP-targeted differentiated cells that were clearly distinguished from non-manipulated control.ConclusionsThese results, thus, identify YAP as an important effector protein that regulates human MSC differentiation to fat and bone and suggests the use of FTIR microspectroscopy as a promising technique in stem cell research.

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Trichostatin A (TSA) has previously been used in somatic cell nuclear transfer (SCNT) to improve the cloning efficiency in several species, which led our team to investigate the effects of TSA on the full-term development of bovine SCNT and gaur-bovine interspecies SCNT (gaur iSCNT; gaur somatic cells as donors and bovine oocytes as recipients) embryos. Treatment with 50 nM TSA for 10 h after fusion had no positive effects on the rates of fusion, cleavage, or the development to eight-cell or morula stages in both bovine SCNT and gaur iSCNT embryos. However, TSA treatment significantly enhanced the blastocyst formation rate in bovine SCNT embryos (44 vs. 32-34% in the TSA-treated and TSA-untreated groups, respectively), but had no effects on gaur iSCNT embryos. The fresh blastocysts derived from bovine SCNT and gaur iSCNT embryos (fresh groups), as well as vitrified bovine SCNT blastocysts (vitrified group), were transferred to bovine recipients. We found that TSA treatment increased the pregnancy rates only in recipients receiving fresh bovine SCNT embryos. In recipients receiving TSA-treated bovine SCNT embryos, three cloned calves from the fresh group and twin cloned calves from the vitrified group were delivered; however, no calf was born from the TSA-untreated bovine SCNT embryos. In contrast, one gaur iSCNT calf was born from a recipient receiving blastocysts from the TSA-untreated group. In summary, TSA improved the preimplantation development and pregnancy rates of bovine SCNT embryos, but did not have any beneficial effect on gaur iSCNT embryos. However, one gaur iSCNT calf reached full-term development.