Hematopoietic Stem Cell Dysfunction in the Elderly After Severe Injury

Overview

Traumatic injury is a leading cause of morbidity and mortality in young adults, and remains a substantial economic and health care burden. Despite decades of promising preclinical and clinical investigations in trauma, investigators understanding of these entities is still incomplete, and few therapies have shown success. During severe trauma, bone marrow granulocyte stores are rapidly released into the peripheral circulation. This release subsequently induces the expansion and repopulation of empty or evacuated space by hematopoietic stem cells (HSCs). Although the patient experiences an early loss of bone marrow myeloid-derived cells, stem cell expansion is largely skewed towards the repopulation of the myeloid lineage/compartment. The hypothesis is that this 'emergency myelopoiesis' is critical for the survival of the severely traumatized and further, failure of the emergency myelopoietic response is associated with global immunosuppression and susceptibility to secondary infection. Also, identifying the release of myeloid derived suppressor cells (MDSCs) in the circulation of human severe trauma subjects. This process is driven by HSCs in the bone marrow of trauma subjects. Additionally, MDSCs may have a profound effect on the nutritional status of the host. The appearance of these MDSCs after trauma is associated with a loss of muscle tissue in these subjects. This muscle loss and possible increased catabolism have huge effects on long term outcomes for these subjects. It is the investigator's goal to understand the differences that occur in these in HSCs and muscle cells as opposed to non-injured and non-infected controls. This work will lead to a better understanding of the myelopoietic and catabolic response following trauma.

This is a prospective study to understand how trauma injuries changes the hematopoeitic stem cells (HSCs) in the bone marrow and muscle cells after trauma injury in elderly subjects is different when compared to non-injured subjects. There will be three groups for this study: 1) Elective hip surgery subjects, 2) Trauma subjects and 3) deidentified bone marrow of healthy controls. Samples of bone marrow and a blood sample will be collected at the time of surgery. The deidentified bone marrow of healthy controls will come from a tissue bank. The blood will be used to perform PB colony assays, ELISAs to test for the following parameters: EPO, G-CSF, Reticulocyte, iron levels and cytokines and inflammatory markers. The bone marrow and blood samples will be processed and sorted to isolate hematopoeitic stem cells for genomic content to determine genomic expression, oxidative stress, mitochondrial activity, apoptosis, autophagy, analysis of circulating erythroid progenitor cells, reticulocytes, granulocyte-colony stimulating factor assays, erythropoietin and iron levels. Clinical data and hemodynamic measurements will be collected daily while subjects are hospitalized and trauma surgery subjects will be followed to evaluate for malunion and subsequent additional surgical procedures for repair.