Myelopoiesis in the omentum of normal mice and during abdominal inflammatory processes

Abstract

Coelomic cavities are relatively isolated from the systemic circulation of blood cells. Resident cell populations have a proper phenotype and kinetics, maintaining their steady-state populations and their responsiveness to local inflammatory reactions, in which the number and quality of coelomic cells can be greatly increased and modified. We have addressed the question of whether the increase in cell infiltrate in the inflamed abdominal cavity is sustained by the proliferation of myeloid cells in the omentum, and if so what are the characteristics of the progenitor cells involved and how the omentum controls their proliferation and differentiation. In the omentum under normal conditions and with inflammation due to schistosomal infection we found that pluripotent early myeloid progenitors were capable of giving rise to all the myeloid lineages in clonogenic assays, but not to the totipotent blood stem cells. Besides the major haemopoietins (GM-CSF, M-CSF, G-CSF, IL-5), the omentum stroma constitutively expressed SDF-1 alpha, the chemokine which elicits homing of circulating early haemopoietic progenitors. While normal omentum stroma produced LIF, its expression was substituted by SCF in inflamed tissues. In the first situation a slow steady-state renewal of progenitors is potentially favoured, while their intense expansion may be predominant in the latter one. We propose that the increase in cells in the abdominal cavity in inflammatory reactions is due to the enhanced input and expansion of early myeloid progenitors sustaining the in situ production of abdominal cell populations, rather than to the input of systemic circulating inflammatory cells.

Pulmonary Stromal-Derived Factor-1 Expression and Effect on Neutrophil Recruitment during Acute Lung Injury

“…Interestingly, SDF-1 expression has also been implicated in the trafficking of myeloid progenitors during injury and inflammation to the liver (58,59) and the peritoneum (60), suggesting that the same chemokine interactions that maintain neutrophils and their precursors within the marrow (29, 38 -40) may be effective in recruiting these cells to extramedullary sites. We posited that pulmonary SDF-1 expression during the progression of ALI could similarly serve as a neutrophil chemoattractant.…”

Developing dendritic cells become ‘lacy’ cells packed with fat and glycogen

“…For example, 'macrophages' derived from omental fat contribute to development of local immune responses in the peritoneal cavity. 40,41 The accumulation of macrophages within adipose tissue in obesity and their involvement in inflammation have also recently been highlighted. [42][43][44] However, increasing evidence suggests that myeloid cells from adipose tissue can have properties of DCs.…”

Adipose tissues as an ancestral immune organ: Site‐specific change in obesity

“…Firstly, a strong anatomical relationship exists between adipose and lymphoid tissues [2,3]. Secondly, adipose cells secrete inflammatory cytokines (tumor necrosis factor (TNF), interleukin (IL)-6) and other adipokines can act as inflammatory cytokines (i.e., leptin) [1,2,4].…”