Cytokine Profile of Adipose-Derived Stem Cells From Patients With Burn Injuries and Infection.

INTRODUCTION: Adipose-derived stem cells (ASCs) are multipotent stem cells capable of differentiating into many cell lineages. They play an important role in wound healing by secreting cytokines. Prior studies have demonstrated the presence of proinflammatory cytokines in burn wounds. However, no studies have been performed evaluating the cytokines released by burn wounds with infections. We hypothesized that there is an alteration in the paracrine factors secreted by ASCs in burn wounds with concomitant infections. METHODS: Adipose tissue was collected from patients with burn injuries at their index operation. ASCs were extracted and grown under standard tissue culture techniques. The supernatant was extracted. Cytokine analyses were performed with multiplex assays. Infection was determined using a burn sepsis protocol. The cytokine profiles of the two groups were compared using a Mann-Whitney U test. RESULTS: Sixteen patients were enrolled in the study, 50% with bacterial infection (n = 8). There was no significant difference in the baseline demographics of the two groups (P > 0.05). There were significantly lower concentrations of interleukin 13 and interferon gamma (P < 0.05) in burn patients with concomitant infections. CONCLUSIONS: ASCs are critical to burn wound healing. This study demonstrated diminished production of interleukin 13, an immunoregulatory cytokine involved in the antiinflammatory pathway by downregulating macrophage activity. This study also demonstrated significantly lower levels of interferon gamma in patient with burns and concomitant infection. This cytokine is crucial for antimicrobial defenses.

Sclerostin Antibody Administration Increases the Numbers of Sox9creER+ Skeletal Precursors and Their Progeny.

Blocking the Wnt inhibitor, sclerostin, increases the rate of bone formation in rodents and in humans. On a cellular level, the antibody against sclerostin acts by increasing osteoblast numbers partly by activating the quiescent bone-lining cells in vivo. No evidence currently exists, to determine whether blocking sclerostin affects early cells of the osteoblast lineage. Here we use a lineage-tracing strategy that uses a tamoxifen-dependent cre recombinase, driven by the Sox9 promoter to mark early cells of the osteoblast lineage. We show that, when adult mice are treated with the rat-13C7, an antibody that blocks sclerostin action in rodents, it increases the numbers of osteoblast precursors and their differentiation into mature osteoblasts in vivo. We also show that rat-13C7 administration suppresses adipogenesis by suppressing the differentiation of Sox9creER+ skeletal precursors into bone marrow adipocytes in vivo. Using floxed alleles of the CTNNB1 gene encoding ß-catenin, we show that these precursor cells express the canonical Wnt signaling mediator, ß-catenin, and that the actions of the rat-13C7 antibody to increase the number of early precursors is dependent on direct stimulation of Wnt signaling. The increase in osteoblast precursors and their progeny after the administration of the antibody leads to a robust suppression of apoptosis without affecting the rate of their proliferation. Thus, neutralizing the Wnt-inhibitor sclerostin increases the numbers of early cells of the osteoblast lineage osteoblasts and suppresses their differentiation into adipocytes in vivo. © 2021 American Society for Bone and Mineral Research (ASBMR).

[Differential effects on bone and mesenchymal stem cells caused by intermittent and continuous PTH administration].

Objective: To investigate the distinct effects of intermittent and continuous administration of parathyroid hormone (PTH) on bone and mesenchymal stem cell (MSC). Methods: Six weeks old mice with C57/BL6J background and SOX9-creERT/Td-tomato/Osteocalcin-GFP genotype were divided into 6 groups: intermittent administration and withdraw group (subcutaneous injection with PTH 500 µg·kg-1·d-1), continuous administration and withdraw group (subcutaneous implantation of PTH pump, 80 µg·kg-1·d-1, with a rate of 0.25 µl/h), control administration and withdraw group, with 8 mice in each group. Serum calcium level and bone mineral density (BMD) were measured after two weeks' treatment and two weeks after drug withdraw. Histopathology and immunofluorescence analyses were performed to assess the effects of PTH on bone and mesenchymal stem cell. Results: Serum calcium level increased transiently in intermittent group[(1.36±0.03) mmol/L]and increased gradually in continuous group[up to (2.33±0.03) mmol/L], but reduced to normal level (1.12-1.27 mmol/L) 14 days after drug withdraw. BMD of both intermittent[(0.047±0.002) g/cm2]and continuous[(0.046±0.001) g/cm2]PTH administration groups increased compared with control group[(0.044±0.001) g/cm2], but there was no significant difference among three groups 2 weeks after drug withdraw. Femoral histopathology showed that bone mass, trabecular number and little fibrous tissue hyperplasia in intermittent PTH group increased. Osteoblasts number increased, but lining cells decreased. There was no significant difference in osteocyte and osteoclast numbers. After withdrawing of intermittent PTH, osteocyte and osteoblast number declined significantly, but there was an increased number of lining cells. Continuous PTH caused very high amount of fibrosis, and osteoclast number increased significantly, while osteoblast and osteocyte number increased slightly. After withdrawing of continuous PTH, fibrosis disappeared significantly, and lining cell number increased. Immunofluorescence staining in the epiphyseal-metaphyseal regions in fibula showed intermittent PTH increased undifferentiated Td-Tomato MSC, but declined significantly after withdrawing. Undifferentiated Td-Tomato MSC in continuous PTH increased slightly and decreased after drug withdraw. Conclusions: Intermittent PTH increased undifferentiated Td-Tomato MSC and osteoblast number, and might transform lining cell into osteocytes and osteoblasts, and thus lead to bone formation. Continuous PTH increased undifferentiated Td/Tomato MSC, osteoblast and osteocyte number slightly, but high amount of fibrosis and osteoclasts can be seen, leading to metabolic bone disease. However, lining cell ascended after drug withdraw, which may be beneficial to bone remodeling.