No evidence for circulating mesenchymal stem cells in patients with organ injury

Area of Science:

• Regenerative Medicine
• Immunology
• Hematology

Background:

• Mesenchymal stem cells (MSCs) reside in bone marrow and are hypothesized to circulate to injury sites.
• Resident MSCs in tissues may also contribute to local repair and immune modulation, potentially negating the need for circulating MSCs.
• Evidence for MSC mobilization and migration in human circulation is limited.

Purpose of the Study:

• To investigate the presence and mobilization of mesenchymal stem cells (MSCs) in human circulation.
• To determine if MSCs circulate in healthy individuals, patients with end-stage renal or liver disease, or heart transplant recipients with rejection.
• To explore the potential release of MSCs into the bloodstream following severe trauma.

Main Methods:

• Culturing mononuclear cells from blood samples under MSC-supporting conditions.
• Analyzing blood from healthy individuals, patients with end-stage renal disease (n=10), end-stage liver disease (n=10), and heart transplant recipients with biopsy-proven rejection (n=8).
• Investigating blood from a severe trauma patient with multiple fractures.

Main Results:

• MSCs were undetectable in the blood of healthy individuals.
• No MSCs were identified in the blood of patients with end-stage renal disease, end-stage liver disease, or heart transplant rejection.
• MSCs were detected in the blood of a severe trauma patient with multiple fractures, indicating bone marrow disruption releases MSCs.

Conclusions:

• Mesenchymal stem cells (MSCs) are not recruited into the circulation of patients with injured solid organs.
• Aggressive immune responses, such as those following transplantation with rejection, do not lead to MSC mobilization into the bloodstream.
• Disruption of bone marrow, as seen in severe trauma, can cause the release of MSCs into circulation.