Figure 7.

Alterations in plasma FN homeostasis in 3-month-old Tgm2^−/−;F13a1^−/−. (a) Plasma (pFN) levels are significantly and dramatically increased in 3-month-old double-null mouse serum. n=6. (b) Cellular FN levels show no significant changes between the serum of Tgm2^−/−;F13a1^−/− and WT mice. n=6. (c) Hepatocytes isolated from 3-month-old Tgm2^−/−;F13a1^−/− and WT mice produce and secrete FN at similar levels as seen by Western blot analysis of FN in culture media. Albumin was used as control protein for media analysis, and actin blotting shows the cellular density of the samples where media was collected from. (CM; conditioned media, CE; cell extract). Western blots are representative of three separate experiments. (d) The Oyster488-labeled FN (Oy488pFN) injection regime. Mice (n=3)(3 month old) were injected intraperitoneally on 3 consecutive days with 1 mg of labeled FN. On day 5, mice were sacrificed and tissue fluids and tissues were collected. (e) Fluorometric detection of Oy488pFN in serum, bone marrow and the bone G1-extract. A significant increase in Oy488pFN retention was seen in serum and bone marrow in 3-month-old Tgm2^−/−;F13a1^−/− mice compared with control WT mice of same age. Conversely, a decrease was seen in Oy488FN incorporation in bone G1-extract. (f) Schematic diagram representing pFN homeostasis in the blood-bone marrow-bone axis and its defect in Tgm2^−/−;F13a1^−/− mice where its accumulation is decreased in bone likely contributing to higher levels in the marrow compartment and in blood. P-values are as follows: *P<0.05, ***P<0.001