Mesenchymal stromal cell response to intervertebral disc-like pH is tissue source dependent.

Intervertebral disc (IVD) degeneration (IVDD) has become increasingly prevalent and is a common contributing factor to low back pain. Current treatment options are limited to either symptom management or surgery. A promising treatment option being explored is intradiscal administration of mesenchymal stromal cells (MSCs). However, there remains a gap in knowledge as to whether MSCs from different tissue sources have similar responses to the low pH microenvironment of the IVD and the possible mechanisms governing these responses. To study this, MSCs from three different tissue sources: adipose (adipose-derived mesenchymal stem cell), bone marrow (bone marrow mesenchymal stem cells), and amnion (amniotic membrane mesenchymal stem cell) were cultured at low pHs representative of IVDD. MSCs were assessed for survival, senescence, apoptosis, metabolic activity, and cytokine release profile. Additionally, western blot was utilized to assess acid sensing ion channel 1 and 3 expression. The results of this study indicated that MSC viability, cell proliferation, senescence, and metabolic activity is negatively affected by low pH and alters MSC cytokine production. This study also demonstrated that MSCs behavior is dependent on tissue source. Understanding how MSC behavior is altered by pH will allow further research aimed at increasing the efficacy of MSC therapy to promote in situ IVD tissue regeneration to combat IVDD.

Integrating 16S rRNA Sequencing and LC⁻MS-Based Metabolomics to Evaluate the Effects of Live Yeast on Rumen Function in Beef Cattle.

We evaluated the effects of live yeast on ruminal bacterial diversity and metabolome of beef steer. Eight rumen-cannulated Holstein steers were assigned randomly to one of two treatment sequences in a study with two 25-d experimental periods and a crossover design. The steers were housed in individual pens. The dietary treatments were control (CON) or yeast (YEA; CON plus 15 g/d of live yeast product). Bacterial diversity was examined by sequencing the V3-V4 region of 16S rRNA gene. The metabolome analysis was performed using a liquid chromatograph and a mass spectrometry system (LC⁻MS). Live yeast supplementation increased the relative abundance of eight cellulolytic bacterial genera as well as Anaerovorax and Lachnospiraceae. Proteiniclasticum, Salmonella, and Lactococcus were not detected in the YEA treatment. Live yeast supplementation increased the concentrations of 4-cyclohexanedione and glucopyranoside and decreased the concentrations of threonic acid, xanthosine, deoxycholic acid, lauroylcarnitine, methoxybenzoic acid, and pentadecylbenzoic acid. The bacteroidales BS11, Christensenellaceae R-7, and Candidatus saccharimonas showed positive correlations with the metabolites involved in amino acid biosynthesis and the metabolism of energy substrates; the functions of these bacteria are not fully understood in relation to the mode of action of yeast. This study confirms the usefulness of LC⁻MS-based metabolomics in deciphering the mode of action of live yeast in the rumen.