In Vitro Properties of Human Mesenchymal Stem Cells and Their Ability to Modulate Inflammation in Vivo

Abstract

Mesenchymal stem cells (MSCs), are plastic adherent cells that are readily isolated from various sources, possess stem-cell-like properties and show unique beneficial features in in vivo models of diseases.

In present dissertation we investigated the aspects of MSCs biology related to both in vitro properties and in vivo abilities to benefit in diseases.

The in vitro part of the dissertation addresses the question of heterogeneity in single-cell derived cultures of human MSCs. Laser capture microdissection was used to isolate distinct inside and outside regions of the colony for RNA isolation. When assayed by microarray the cells from inside and outside regions of the colony showed distinct patterns of gene expression profile. In functional studies, however, we did not find any differences – the cells perform similarly in cloning and in vitro growth assays.

In the in vivo part of the dissertation we investigated the effects of human MSCs and their secreted protein tumor-necrosis factor stimulated gene/protein 6 (TSG-6) in two models of lung injury - hydrocloric-acid (HCl)-induced lung injury and bleomycininduced lung injury in mice. We showed that intraperitoneal administration (IP) of human MSCs improved lung function and inhibited inflammation in the lungs after HCl lung injury. Human recombinant TSG-6 inhibited inflammation in both, HCl-induced lung injury and bleomycin-induced lung injury, however it improved lung function only in mice injured with bleomycin.

Finally we investigated the effects of MSCs administered inside the peritoneal cavity to explain the beneficial effects in HCl-induced lung injury. We showed that MSCs aggregated rapidly after the injection IP and preconditioned immune system by recruiting immune cells to peritoneal cavity and by triggering the production of various classes of cytokines. We utilized real-time polymerase chain reaction (PCR) and in vivo imaging to estimate the amount MSCs present in various organs of peritoneal cavity. Most of MSCs were found in omentum and mesenteric tissues, only negligible amount of cells was recovered from lymph nodes and spleen.

In conclusion, the dissertation is expanding the existing knowledge about MSCs, increases our knowledge both in understanding the basic biology of the cells and their interaction with the host organism.