Correlation of plasma FL expression with bone marrow irradiation dose.

PURPOSE: Ablative bone marrow irradiation is an integral part of hematopoietic stem cell transplantation. These treatment regimens are based on classically held models of radiation dose and the bone marrow response. Flt-3 ligand (FL) has been suggested as a marker of hematopoiesis and bone marrow status but the kinetics of its response to bone marrow irradiation has yet to be fully characterized. In the current study, we examine plasma FL response to total body and partial body irradiation in mice and its relationship with irradiation dose, time of collection and pattern of bone marrow exposure. MATERIALS/METHODS: C57BL6 mice received a single whole body or partial body irradiation dose of 1-8 Gy. Plasma was collected by mandibular or cardiac puncture at 24, 48 and 72 hr post-irradiation as well as 1-3 weeks post-irradiation. FL levels were determined via ELISA assay and used to generate two models: a linear regression model and a gated values model correlating plasma FL levels with radiation dose. RESULTS: At all doses between 1-8 Gy, plasma FL levels were greater than control and the level of FL increased proportionally to the total body irradiation dose. Differences in FL levels were statistically significant at each dose and at all time points. Partial body irradiation of the trunk areas, encompassing the bulk of the hematopoietically active bone marrow, resulted in significantly increased FL levels over control but irradiation of only the head or extremities did not. FL levels were used to generate a dose prediction model for total body irradiation. In a blinded study, the model differentiated mice into dose received cohorts of 1, 4 or 8 Gy based on plasma FL levels at 24 or 72 hrs post-irradiation. CONCLUSION: Our findings indicate that plasma FL levels might be used as a marker of hematopoietically active bone marrow and radiation exposure in mice

Correlation of Plasma FL Expression with Bone Marrow Irradiation Dose

<div><p>Purpose</p><p>Ablative bone marrow irradiation is an integral part of hematopoietic stem cell transplantation. These treatment regimens are based on classically held models of radiation dose and the bone marrow response. Flt-3 ligand (FL) has been suggested as a marker of hematopoiesis and bone marrow status but the kinetics of its response to bone marrow irradiation has yet to be fully characterized. In the current study, we examine plasma FL response to total body and partial body irradiation in mice and its relationship with irradiation dose, time of collection and pattern of bone marrow exposure.</p> <p>Materials/Methods</p><p>C57BL6 mice received a single whole body or partial body irradiation dose of 1–8 Gy. Plasma was collected by mandibular or cardiac puncture at 24, 48 and 72 hr post-irradiation as well as 1–3 weeks post-irradiation. FL levels were determined via ELISA assay and used to generate two models: a linear regression model and a gated values model correlating plasma FL levels with radiation dose.</p> <p>Results</p><p>At all doses between 1–8 Gy, plasma FL levels were greater than control and the level of FL increased proportionally to the total body irradiation dose. Differences in FL levels were statistically significant at each dose and at all time points. Partial body irradiation of the trunk areas, encompassing the bulk of the hematopoietically active bone marrow, resulted in significantly increased FL levels over control but irradiation of only the head or extremities did not. FL levels were used to generate a dose prediction model for total body irradiation. In a blinded study, the model differentiated mice into dose received cohorts of 1, 4 or 8 Gy based on plasma FL levels at 24 or 72 hrs post-irradiation.</p> <p>Conclusion</p><p>Our findings indicate that plasma FL levels might be used as a marker of hematopoietically active bone marrow and radiation exposure in mice.</p> </div

Partial Body Irradiation Patterns and FL Response.

<p>Plasma FL expression following heterogeneous partial body irradiation patterns in C57BL6 mice. A) Mice were partially shielded to irradiation using the represented partial body diagrams with either the head, limbs, trunk, or trunk+limbs exposed. B) Plasma FL expression in partial body exposed mice at 0, 2, and 8 Gy at 24 hrs post-IR. C) Plasma FL expression in partial body exposed mice at 0, 2, and 8 Gy at 72 hrs post-IR. Values reflect the mean ± SEM.</p

FL Levels Following TBI.

<p>FL levels correlate with dose of irradiation and time of collection. A) Plasma FL levels in TBI C57BL6 mice at 24, 48 and 72 hrs post-IR at doses between 0 and 8 Gy. B) Extended time course of plasma FL expression in TBI C57BL6 mice at 0, 4 and 8 Gy at time points between 24 hrs and 3wks post-IR. Values reflect the mean ± SEM.</p

Results of Blinded Dose Prediction Analysis Using Plasma FL at 24 hrs and 72 hrs following Total Body Irradiation.

α<p>#Correct represents the number of correct predictions over # of total animals in that group. 72 hr time point prediction analysis includes evaluation of 24 hr/72 hr FL trend as described in the text.</p>β<p>Samples pooled from the stated treatment groups and evaluated as a single cohort.</p