A comparison of adipose and bone marrow-derived mesenchymal stromal cell secreted factors in the treatment of systemic inflammation

Abstract

Background: Bone marrow-derived mesenchymal stromal cells (BMSCs) are a cell population of intense exploration for therapeutic use in inflammatory diseases. Secreted factors released by BMSCs are responsible for the resolution of inflammation in several pre-clinical models. New studies have uncovered that adipose tissue also serves as a reservoir of multipotent, non-hematopoietic stem cells, termed adipose-derived stromal/stem cells (ASCs), with many common characteristics to BMSCs. We hypothesized that ASC and BMSC secreted factors would lead to a comparable benefit in the context of generalized inflammation.

Findings: Proteomic profiling of conditioned media revealed that BMSCs express significantly higher levels of sVEGFR1 and sTNFR1, two soluble cytokine receptors with known therapeutic activity in sepsis. In a prophylactic study of endotoxin-induced inflammation in mice, we observed that BMSC secreted factors provided a greater survival benefit and tissue protection of endotoxemic mice compared to ASCs. Neutralization of sVEGFR1 and sTNFR1 did not significantly affect the survival benefit experienced by mice treated with BMSC secreted factors.

Conclusions: Our findings suggest that BMSCs may be more effective as a cell therapeutic for use in endotoxic shock and that ASCs may be positioned for continued exploration in immunomodulatory diseases. Soluble cytokine receptors can distinguish stromal cells from different tissue origins, though they may not be the sole contributors to the therapeutic benefit of BMSCs. Furthermore, other secreted factors not discussed in this study may also differentiate these stromal cell populations from one another.

Figure 1

Differences in soluble receptor secretion by ex-vivo expanded stromal cell populations. BMSC-CM and ASC-CM was concentrated 25-fold, to a formulation that represented the collection of 2x10⁶ cells per ml of CM. Control samples are basal media that was not conditioned by cells. Shown are ELISA analysis of CM for soluble receptors, including (a) sTNFR1, (b) sVEGFR1, (c) sTNFR2 and (d) sVEGFR2. There was non-specificity of the sVEGFR2 antibody pair when analyzing CM samples. BMSCs uniquely expressed high levels of sTNFR1 and sVEGFR1.

Figure 2

BMSC-CM provides a greater survival benefit to LPS-treated mice than ASC-CM. 10 ug LPS were administered IP to each mouse to induce endotoxemia, followed by either 1 ml of saline (control), 1 ml BMSC-CM, or 1 ml ASC-CM IP. ASC-CM treated mice did not experience a significantly greater survival benefit in comparison to control (P = 0.924), whereas BMSC-CM treated mice did (P = 0.007).

Figure 3

Cell-specific attenuation of end-organ damage in LPS mice by BMSC-CM. One day following LPS and CM administration, tissue was harvested for hematoxylin and eosin (H&E) staining. Sections were analyzed for detection of tubular degeneration in kidney, inflammation in the lungs, hepatocellular vacuolation and degeneration of the liver. Magnifications are x20. (a) The renal cells of the healthy kidney appear to be unperturbed in contrast with the pale and poorly defined cells of the LPS-treated mouse. The ASC-CM kidney presents with similarly pale renal cells, whereas the BMSC-CM kidney resembles the healthy control. (b) Alveoli are generously and evenly distributed in the healthy lung compared to the LPS-treated group, which appears more constricted. The BMSC-CM treated lungs also present with expansive and unaffected alveoli, but the ASC-CM treated lungs are clearly devastated: alveoli are significantly smaller and sparser. (c) The healthy liver shows few signs of inflammation. The LPS-treated liver has swollen hepatocytes with affected nuclei. Many unhealthy cells appear in the ASC-CM treated liver as well. The BMSC-CM treated liver appears to have fewer necrotic hepatocytes. (d) Histological slides were blindly scored by a pathologist. (P < 0.05).

Figure 4

LPS-treated mice experience insignificant benefit when treated with BMSC-CM compared to BMSC-CM with neutralizing antibodies targeting sTNFR1 and sVEGFR1. 10 ug LPS were administered IP to each mouse to induce endotoxemia, followed by either 1 ml of saline (control), 1 ml BMSC-CM, 1 ml BMSC-CM with neutralizing sTNFR1 antibody, or 1 ml BMSC-CM with neutralizing sVEGFR1 antibody IP. BMSC-CM treated mice experienced a significantly greater survival benefit in comparison to control mice (P = 0.0454). Mice given BMSC-CM with neutralizing sTNFR1 antibody also experienced a significantly greater survival benefit compared to control (P = 0.0225). The BMSC-CM with neutralizing sVEGFR1 antibody group did not differ significantly from the control (P = 0.106) or from the neutralizing sTNFR1 antibody group (P = 0.528). Finally, neither group that received a neutralizing soluble receptor antibody had a significantly different survival benefit compared to the BMSC-CM treated group (neutralizing sTNFR1 antibody vs BMSC-CM P = 0.563; neutralizing sVEGFR1 antibody vs BMSC-CM P = 0.237).