الفهرس 
Lung anatomyOnly 14 pages are availabe for public view
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Abstract
Acute lung injury(ALI) and Acute Respiratory Distress Syndrome (ARDS) constitutes a spectrum of increasingly severe acute respiratory failure. It results from multiple causes (such as infection, trauma and major surgery), and is the leading cause of death and disability in the critically ill.
ARDS is characterised clinically by an acute onset, severe hypoxia, stiff lungs, and the presence of an inflammatory pulmonary oedema . It is a devastating disease process and is the leading cause of death and disability in critically ill adults and children .
In the US alone, there are 200,000 new cases annually, with a mortality rate of 40%, comparable to that seen from HIV and breast cancer .
The outlook for survivors of ARDS is also poor with a high incidence of post-discharge cognitive impairment, depression and muscle weakness, while the financial burden of ARDS on society is considerable .
Despite decades of research, there are no therapies for ARDS, and management remains supportive. Probable reasons for the failure to find a successful therapy include deficits in understanding of the disease.
Acute lung injury (ALI),Acute Respiratory Distress Syndrome (ARDS) are a response to a variety of inciting stimuli that is the leading cause of death and disability in the critically ill.
A growing understanding of the complexity of the pathophysiology of ARDS, coupled with advances in stem cell biology, has lead to an interest in the therapeutic potential of stem cells for ALI/ARDS.
Stem cells can modulate the immune response to reduce injury and also increase resistance to infection, while also facilitating regeneration and repair of the injured lung. This unique combination of effects has generated considerable excitement. the biological characteristics of stem cells that underlie their therapeutic potential for ALI/ARDS.
Evaluating the potential and pitfalls of using stem cells for treatment, and examine the likely future directions for stem cells in ALI/ARDS.
A stem cell is a cell that has the ability to divide asymmetrically to produce another cell like itself, or a more differentiated cell . Stem cells are classified based on their tissue of origin. Embryonic stem cells (ESCs) are derived from the inner blastocyst cell mass and are pluripotent, that is, they are capable of differentiating into cells of all embryological lineages.
Fetal stem cells are derived from extra-embryonic tissues, including the amniotic fluid, the placenta, umbilical cord blood and Wharton’s jelly.
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The ideal cell type to use to regenerate the injured lung would be the lung’s native stem cell population. The ability of the lung to regenerate following injury provides clear evidence for the existence of one or more native lung stem cell populations .
Stem cells are used in clinical trials for a variety of diseases, including diabetes, myocardial infarction, Crohn’s disease, graft-versus-host disease, osteogenesis imperfecta, multiple sclerosis, and COPD (chronic pulmonary obstructive disease), attesting to their safety in humans.
Stem cells reduce lung injury caused by endotoxin, pneumonia and systemic sepsis . Recently, the clinical potential of stem cells for ARDS has been considerably enhanced by a study demonstrating that human mesenchymal stem cells can reduce endotoxin-induced injury in explanted human lungs. All these findings offer considerable hope that stem cells offer considerable hope that they may be a therapy for ARDS, as stem cells could differentiate into lung epithelial cells, directly replacing the damaged and destroyed cells in the alveoli in ARDS
Stem cells constitute a promising therapeutic strategy for patients suffering from ALI/ARDS. MSCs appear closest to clinical translation, given the evidence that they may favourably modulate the immune response to reduce lung injury, while maintaining host immune-competence and also facilitating lung regeneration and repair. The demonstration that human MSCs exert benefit in the endotoxin-injured human lung is particularly persuasive. However, gaps remain in knowledge regarding the mechanisms of action of MSCs, the optimal MSC administration and dosage regimens, and the safety of MSCs in critically ill patients. It is anticipated that these remaining knowledge deficits will be addressed in ongoing and future studies.
Other stem cells, such as ESCs and iPCs, are at an earlier stage in the translational process, but offer the hope of directly replacing injured lung tissue. Ultimately, lung-derived stem cells may offer the greatest hope for lung diseases, given their role in replacing and repairing the native damaged lung tissues.