Endogenous and exogenous stem cells: a role in lung repair and use in airway tissue engineering and transplantation

Abstract

Rapid repair of the denuded alveolar surface after injury is a key to survival. The respiratory tract contains several sources of endogenous adult stem cells residing within the basal layer of the upper airways, within or near pulmonary neuroendocrine cell rests, at the bronchoalveolar junction, and within the alveolar epithelial surface, which contribute to the repair of the airway wall. Bone marrow-derived adult mesenchymal stem cells circulating in blood are also involved in tracheal regeneration. However, an organism is frequently incapable of repairing serious damage and defects of the respiratory tract resulting from acute trauma, lung cancers, and chronic pulmonary and airway diseases. Therefore, replacement of the tracheal tissue should be urgently considered. The shortage of donor trachea remains a major obstacle in tracheal transplantation. However, implementation of tissue engineering and stem cell therapy-based approaches helps to successfully solve this problem. To date, huge progress has been achieved in tracheal bioengineering. Several sources of stem cells have been used for transplantation and airway reconstitution in animal models with experimentally induced tracheal defects. Most tracheal tissue engineering approaches use biodegradable three-dimensional scaffolds, which are important for neotracheal formation by promoting cell attachment, cell redifferentiation, and production of the extracellular matrix. The advances in tracheal bioengineering recently resulted in successful transplantation of the world's first bioengineered trachea. Current trends in tracheal transplantation include the use of autologous cells, development of bioactive cell-free scaffolds capable of supporting activation and differentiation of host stem cells on the site of injury, with a future perspective of using human native sites as micro-niche for potentiation of the human body's site-specific response by sequential adding, boosting, permissive, and recruitment impulses.

Optical imaging of subacute airway remodeling and adipose stem cell engraftment after airway injury

“…In many studies, ASC engraftments have been shown to attenuate lung injury and fibrosis [17,18]. In our study, rASCs were detected in the rASCs treatment group but not in the saline group.…”

Engineering Functional Epithelium for Regenerative Medicine and In Vitro Organ Models: A Review

“…The epithelial/ECM interaction is crucial for dedifferentiation and redifferentiation of the epithelial cells and in combination with degradation of the BM structures, they are implicated in epithelial migration. 39 B-1 subunit integrins contribute to the migration of epithelial cells on laminin and collagen type IV. 40 However, in large wounds, the cells' ability to migrate may not be sufficient to cover the entire wound area.…”

Perspectives of purinergic signaling in stem cell differentiation and tissue regeneration

“…Thus, the mechanism of the repair of damaged epithelium has been widely studied. Epithelial progenitors termed Clara cells (transit-amplifying cells) are broadly distributed and after injury differentiate into ciliated cells [117,118]. In addition to Clara cells, bronchiolar airways have also rare stem cells that contribute to repair of the tissue [119].…”