Adult stem cells and repair through granulation tissue

Abstract

Macrophage recruitment and proliferation of both small vessels (endothelium and pericytes) and fibroblast-myofibroblasts are the fundamental and provisional cellular findings in repair through granulation tissue (RTGT).Endothelium and pericytes of preexisting microvasculature may act as progenitor cells of new endothelial cells and new pericyte-fibroblast-myofibroblasts, respectively.Likewise, fibroblasts may be progenitors of themselves, and of myofibroblasts and pericytes. Moreover, all these cells may originate from circulating progenitor cells or other progenitor cells..According to this extensive cellular plasticity, this work reviews the adult stem cells (ASC) and transit- amplifying cells (TAC) related to the principal cellular components of RTGT.Moreover, we hypothesize that the perivascular region, with a heterogeneous pericyte-like cellular population, including pericytes, perivascular fibroblasts and homing cells from the bone marrow (fibrocytes and bone marrow mesenchymal cells), is the niche of progenitor cells in RTGT and the substrate of regulatory mechanisms (perivascular niche hypothesis).We also highlight RTGT as a "paracrine transitional organ" during involutive phenomena and cellular differentiation.Furthermore, we consider the combined role of both systems (ASC-TAC and RTGT) in tissue engineering and in pathological processes, such as fibrosis, organization, atherosclerosis, and tumor stroma.

The recruitment of two consecutive and different waves of host stem/progenitor cells during the development of tissue-engineered bone in a murine model

“…In turn, monocytes and macrophages secrete factors that act as signals for other cell types during tissue and organ development [31,32]. The presence, in the site of the bone repair/regeneration, of mobilized macrophages and other inflammatory cell types, together with recruited endothelial progenitors, pericytes, and possibly other pluripotent mesenchymal cells, well supports the concept of an active participation and cooperation of these different cell types in the generation of the engineered bone [33,34].…”

Kidney Pericytes: Roles in Regeneration and Fibrosis

“…1,18 Macrophage-like properties with phagocytosis in vitro and in vivo have been described for a subset of pericytes and it has been hypothesized that this functionally defined pericyte subset may originate from bone marrow mesenchymal progenitors. 19 Another possible role for pericytes in the immune defense system might be antigen presentation to T lymphocytes. 1,20 For human brain pericytes, a possible role in the extrinsic pathway of blood coagulation by expression of procoagulant enzyme complexes has been reported.…”

The role of biomaterials in the direction of mesenchymal stem cell properties and extracellular matrix remodelling in dermal tissue engineering

“…The regenerative phase of wound repair is characterised by the presence of fibroblasts, appearance of new blood vessels and chronic inflammatory cells [1,2]. Multipotent mesenchymal stem cells (MSC), also referred to as mesenchymal stromal cells, were shown to home to various sites of injury when injected into the vascular system.…”