Altered leucocyte progenitor profile in human bone marrow from patients with major trauma during the recovery phase

Changes in human bone marrow associated with the systemic inflammatory response to injury are little understood. It was hypothesized that major trauma results in an altered bone marrow leucocyte progenitor profile, with either uniform depletion or the balance between multipotent and committed progenitors varying, depending on whether self-renewal is favoured over differentiation.

Bone marrow aspirate and peripheral blood samples were obtained at definitive surgery in adults with pelvic fractures from blunt trauma (major trauma with Injury Severity Score (ISS) at least 18, or isolated fractures) and control patients undergoing iliac crest bone grafting. ISS, interval to surgery and transfusion in the first 24 h were recorded. Bone marrow aspirate flow cytometry was used to identify haemopoietic progenitor cells (CD34(+) ), multipotent cells (CD34(+) CD45(+) CD38(-) ) and oligopotent cells (CD34(+) CD45(+) CD38(lo/+) and CD34(+) CD45(+) CD38(BRIGHT(++ +)) subsets). Peripheral blood levels of inflammatory markers were measured, and the ratio of immature to mature (CD35(-) /CD35(+) ) granulocytes was determined.

The median (range) interval between injury and sampling was 7 (1-21) and 5 (1-21) days in the major trauma and isolated fracture groups respectively. The CD34(+) pool was significantly depleted in the major trauma group (P = 0·017), particularly the CD34(+) CD45(+) CD38(BRIGHT(++ +)) oligopotent pool (P = 0·003). Immature CD35(-) granulocytes increased in bone marrow with increasing injury severity (P = 0·024) and massive transfusion (P = 0·019), and in peripheral blood with increasing interval to surgery (P = 0·005).

Major blunt trauma resulted in changes in the bone marrow CD34(+) progenitor pool. At the point in recovery when these samples were obtained, oligopotent progenitors were lost from the bone marrow, with continued release of immature cells.