Human mesenchymal stem cells (hMSCs) have the capacity to differentiate along several pathways to form bone, cartilage, tendon, muscle, and adipose tissues. The adult hMSCs reside in vivo in the bone marrow in niches where oxygen concentration is far below the ambient air, which is the most commonly encountered laboratory condition. The study reported here was designed to determine whether oxygen has a role in the differentiation of hMSCs into adipocytes. Indeed, when exposed to atmosphere containing only 1% of oxygen, the formation of adipocytelike phenotype with cytoplasmic lipid inclusions was observed. The effect of hypoxia on the expression of adipocyte-specific genes was determined by real-time reverse transcription polymerase chain reaction. Interestingly, neither of the two central regulators of adipogenesis-the transcription factors peroxisome proliferatoractivated receptor γ2 (PPAR-γ2) and ADD1/SREBP1c-was induced. Furthermore, hypoxia did not have any effect on the transcription of early (lipoprotein lipase) or late (aP2) marker genes. By the same token, neither of the mature adipocyte-specific genes-leptin and adipophilinwas found responsive to the treatment. High level of induction, however, was observed with the PPAR-γ-induced angiopoietin-related gene, PGAR. The lack of an adipocyte-specific transcription pattern thus indicates that despite accumulation of the lipid, true adipogenic differentiation did not take place. In conclusion, hypoxia appears to exert a potent lipogenic effect independent of PPAR-γ2 maturation pathway.

Periodontal ligament cells responded to Sr4 with increased cellular proliferation and osteogenic behavior in vitro.

ObejectiveTo investigate the effect of increasing Strontium (Sr) concentrations on the growth and osteogenic behavior of human bone marrow stromal cells (BMSCs) from mesenchymal (i.e., fibula) and ectomesenchymal (i.e., mandible) embryonic origins.Materials and methodsFibula and mandible BMSCs were cultured in media without (Ctrl) or with Sr in four diverse concentrations: Sr1, 11.3 × 10−3 mg/L, human seric physiological level; Sr2, 13 mg/L, human seric level after strontium ranelate treatment; Sr3, 130 mg/L, and Sr4, 360 mg/L. Proliferation rate (1, 3, and 7 days), osteogenic behavior (alkaline phosphatase [ALP] activity, 7 and 14 days; expression of osteogenic genes (ALP, osteopontin, and osteocalcin at 7, 14, and 21 days), and formation of mineralized nodules (14 and 21 days) of the BMSCs were assessed. Data was compared group‐ and period‐wise using analysis of variance tests.ResultsFibula and mandible BMSCs cultured with Sr4 showed increased proliferation rate, and osteocalcin and osteopontin gene expression together with more evident formation of mineralized nodules, compared all other Sr concentrations. For both cell populations, Sr4 led to lower ALP activity, and ALP gene expression, compared with the other Sr concentrations.ConclusionBMSCs from mesenchymal (i.e., fibula) and ectomesenchymal (i.e., mandible) embryonic origins showed increased cellular proliferation and osteogenic behavior when cultured with Sr4, in vitro.

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Information on smoking exposure obtained with self-reports may be inaccurate. Cotinine has a large half-life and its salivary levels correlate well with plasmatic levels. The influence of storage conditions on the validity and precision of salivary cotinine assessments has rarely been evaluated. Here, smokers donated saliva samples, which were sent for immediate analysis, mail posting, storage at 4 °C for 30 or 90 days, or storage at −20 °C for 30 or 90 days. Cotinine levels were determined using enzyme-linked immune-sorbent assay. Agreement of cotinine level measurements was assessed using Bland-Altman analyses. Average age (years), duration of smoking (years) and number of cigarettes smoked (/day) were 55.4 (±SD 9.4), 35.1 (±SD 11.3), and 15.3 (±SD 7.6). The mean immediate cotinine level was 457 ng/mL (range 11.3 to 1318 ng/mL). Mean cotinine levels in samples analyzed after delay ranged between 433 ng/mL (−20 °C 30 days) and 468 ng/mL (4 °C 30 days). A dose-response gradient was observed in the relationship between salivary cotinine level and self-reported smoking status. A good agreement between cotinine levels for all storage conditions compared with immediate analysis was observed, with average differences ranging from −11 to 24 ng/mL. Cotinine levels remained stable regardless of the tested condition. The stability of salivary cotinine may enable samples to be obtained in difficult-to-reach areas, reduce study costs, and improve the validity of the information on exposure to smoking.