Arsenic Inhibition in Adipogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal Stem Cells: Multipotent Progenitors of Bone, Fat, and Cartilage

Mesenchymal stem cells (MSCs) are stem cells that can be found in the bone marrow, adipose tissue, and umbilical cord. These multipotent cells are capable of self-renewal, and can differentiate into osteocytes (bone), adipocytes (fat), and chondrocytes (cartilage). Importantly, these different differentiation pathways can be manipulated in vitro using specific induction culture media to investigate the factors and signaling pathways that determine each distinct differentiation program. Given their ability to differentiate into multiple lineages in response to damage, hMSCs have been used in the clinic to treat conditions that involve tissue damage, like graft-versus-host disease, certain types of inflammatory bowel disease, and more.

Lifeline® offers hMSCs from multiple origins, including:
• Adipose (HMSC-Ad)
• Pre-adipocytes, or mature adipocytes (HMSC-Pre-Adipocyte)
• Bone marrow (HMSC-BM)
• Wharton’s Jelly (HMSC-WJ)

Lifeline® also has everything you need to maintain hMSCS or induce differentiation. We offer optimized media for maintaining cultured hMSCs in undifferentiated states (StemLife™ and FibroLife®), as well as induction media for differentiating hMSCs down the three main lineages. These include AdipoLife™ (adipocyte lineage), ChondroLife™ (chondrocyte lineage), and OsteoLife™ (osteocyte lineage). Differentiation of each lineage can be confirmed using Alizarin Red (osteocytes), Alcian Blue (chondrocytes), or Oil Red O staining (adipocytes), the staining kits for which Lifeline® also carries.

Lifeline® hMSCs in Arsenic Exposure Research

Arsenic is a natural element for which a lot of concern arises due to its potential presence in drinking water. High exposure to arsenic through drinking water can lead to health problems, such as cardiovascular disease, some cancers, and metabolic disease, like diabetes. On a molecular level, arsenic inhibits the adipogenic differentiation of mesenchymal stem cells, and alters the expression of miRNAs and cyclin D1. To further investigate the mechanism by which these factors are connected, Beezhold et al. exposed mice to arsenic in drinking water, which is known to alter adipose tissue.

The researchers first measured expression of miRNAs involved in adipogenesis and diabetes, and found that arsenic increased the abundance of miR-27a, -27b, -29a, -29b, and -222; in contrast, arsenic decreased abundance of miR-133a, which is important for regulating the balance of white and brown fat. Given this data, the group chose to specifically investigate the role of arsenic-induced miR-29 expression on adipogenesis using Lifeline® human mesenchymal stem cells (hMSCs) isolated from adipose tissue. They cultured hMSCs in StemLife® medium to maintain the undifferentiated state, and in AdipoLife® differentiation media to induce adipogenesis. Although there was little effect on miR-29a and -29c, arsenic exposure increased expression of miR-29b in undifferentiated hMSCs, but not in differentiated hMSCS. Additionally, arsenic increased the protein expression of cyclin D1 in differentiating hMSCs up to 48 hours.

To evaluate the specific role of miR-29b and its targets on adipogenesis, the authors inhibited miR-29b and found that although adipogenesis was not affected, arsenic-induced cyclin D1 protein expression was impaired. The authors hypothesized that a miR-29 target regulates a cyclin D1 brake that is alleviated upon miR-29 inhibition. To identify this target, the authors investigated whether Smad Nuclear Interacting Protein-1 (SNIP-1), which has miR-29 binding sites, could be this brake. Indeed, following overexpression of the three miR-29 members, both cyclin D1 and SNIP-1 protein expression was decreased, suggesting that SNIP-1 could be involved.

Finally, the authors generated Lifeline® hMSCs that stably expressed a miR-29b inhibitor (mZIP-29b), enabling them to observe the effects of miR-29b inhibition over the entire course of hMSC differentiation in response to arsenic. Interestingly, they found that inhibition of miR-29b prevented adipogenesis even in the absence of arsenic, and on day 4 of adipogenesis, attenuated cyclin D1 expression. When the authors examined an early time course (6 hours post adipogenesis induction), they found that the normal cycling of cyclin D1 during the differentiation process was disrupted by miR-29b inhibition. Together, the results of this study suggest that arsenic alters the regulation of cyclin D1 by miR-29b, disrupting the normal cyclical expression of cyclin D1, which is important for adipogenesis.

Are you using Lifeline® cells or media in your research? If so, we want to hear about it! Every other week on the blog we share recent research published using our cells and media and yours could be next!