Bone marrow transplantation enhances trafficking of host-derived myelomonocytic cells that rescue intestinal mucosa after whole body radiation

A Systematic Review of the Evidence of Hematopoietic Stem Cell Differentiation to Fibroblasts

Fibroblasts have an important role in the maintenance of the extracellular matrix of connective tissues by producing and remodelling extracellular matrix proteins. They are indispensable for physiological processes, and as such also associate with many pathological conditions. In recent years, a number of studies have identified donor-derived fibroblasts in various tissues of bone marrow transplant recipients, while others could not replicate these findings. In this systematic review, we provide an overview of the current literature regarding the differentiation of hematopoietic stem cells into fibroblasts in various tissues. PubMed, Embase, and Web of Science (Core Collection) were systematically searched for original articles concerning fibroblast origin after hematopoietic stem cell transplantation in collaboration with a medical information specialist. Our search found 5421 studies, of which 151 were analysed for full-text analysis by two authors independently, resulting in the inclusion of 104 studies. Only studies in animals and humans, in which at least one marker was used for fibroblast identification, were included. The results were described per organ of fibroblast engraftment. We show that nearly all mouse and human organs show evidence of fibroblasts of hematopoietic stem cell transfer origin. Despite significant heterogeneity in the included studies, most demonstrate a significant presence of fibroblasts of hematopoietic lineage in non-hematopoietic tissues. This presence appears to increase after the occurrence of tissue damage.

Stromal Progenitor Cells in Mitigation of Non-Hematopoietic Radiation Injuries

PURPOSE OF REVIEW

Therapeutic exposure to high doses of radiation can severely impair organ function due to ablation of stem cells. Normal tissue injury is a dose-limiting toxicity for radiation therapy (RT). Although advances in the delivery of high precision conformal RT has increased normal tissue sparing, mitigating and therapeutic strategies that could alleviate early and chronic radiation effects are urgently needed in order to deliver curative doses of RT, especially in abdominal, pelvic and thoracic malignancies. Radiation-induced gastrointestinal injury is also a major cause of lethality from accidental or intentional exposure to whole body irradiation in the case of nuclear accidents or terrorism. This review examines the therapeutic options for mitigation of non-hematopoietic radiation injuries.

RECENT FINDINGS

We have developed stem cell based therapies for the mitigation of acute radiation syndrome (ARS) and radiation-induced gastrointestinal syndrome (RIGS). This is a promising option because of the robustness of standardized isolation and transplantation of stromal cells protocols, and their ability to support and replace radiation-damaged stem cells and stem cell niche. Stromal progenitor cells (SPC) represent a unique multipotent and heterogeneous cell population with regenerative, immunosuppressive, anti-inflammatory, and wound healing properties. SPC are also known to secrete various key cytokines and growth factors such as platelet derived growth factors (PDGF), keratinocyte growth factor (KGF), R-spondins (Rspo), and may consequently exert their regenerative effects via paracrine function. Additionally, secretory vesicles such as exosomes or microparticles can potentially be a cell-free alternative replacing the cell transplant in some cases.

SUMMARY

This review highlights the beneficial effects of SPC on tissue regeneration with their ability to (a) target the irradiated tissues, (b) recruit host stromal cells, (c) regenerate endothelium and epithelium, (d) and secrete regenerative and immunomodulatory paracrine signals to control inflammation, ulceration, wound healing and fibrosis.

Bone marrow derived macrophages fuse with intestine stromal cells and contribute to chronic fibrosis after radiation

BACKGROUND AND PURPOSE

Bone marrow-derived cells (BMDC) have been demonstrated to play a critical role in intestine regeneration. However, organ fibrosis was one of the major side effects of bone marrow (BM) transplantation. It warrants further investigation on the mechanisms of BM cell therapy in radiation induced intestine damage.

MATERIALS AND METHODS

We established three murine models to evaluate BMDC within intestines after radiation, including cre-loxP system of transgenic mice. In vitro co-culture between murine BM with human intestine stromal cells was also performed to measure the level of fusion and fibrosis after treatment with anti-fibrotic agents or after macrophage depletion.

RESULTS

Despite complete recovery of epithelial mucosa from radiation damage, we found persistent proliferation and repopulation of BMDC within the lamina propria. Fusion between BM derived monocytic and intestine stromal cells correlated with the level of fibrosis and proliferation index. Depleting macrophages genetically using CD11b-DTR mouse model or pharmacologically using clodronate liposome reduced the level of cell fusion and intestine fibrosis.

CONCLUSIONS

Fibrotic cues from intestine enhance fusion between BM-derived monocytes/macrophages with intestine stromal cells. The fusion hybrids promote cell cycle re-entry, proliferation and reinforce fibrosis signal. Depleting macrophages interferes with cell fusion and ameliorates radiation-induced intestine fibrosis.

Personalized nanomedicine advancements for stem cell tracking

Recent technological developments in biomedicine have facilitated the generation of data on the anatomical, physiological and molecular level for individual patients and thus introduces opportunity for therapy to be personalized in an unprecedented fashion. Generation of patient-specific stem cells exemplifies the efforts toward this new approach. Cell-based therapy is a highly promising treatment paradigm; however, due to the lack of consistent and unbiased data about the fate of stem cells in vivo, interpretation of therapeutic effects remains challenging hampering the progress in this field. The advent of nanotechnology with a wide palette of inorganic and organic nanostructures has expanded the arsenal of methods for tracking transplanted stem cells. The diversity of nanomaterials has revolutionized personalized nanomedicine and enables individualized tailoring of stem cell labeling materials for the specific needs of each patient. The successful implementation of stem cell tracking will likely be a significant driving force that will contribute to the further development of nanotheranostics. The purpose of this review is to emphasize the role of cell tracking using currently available nanoparticles.