Prof Dr Hala Gabr Prof of Clinical Pathology Faculty of
Medicine, Cairo University Director of BMT Lab
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Lung diseases remain a devastating cause of morbidity and
mortality worldwide. Unlike many other major diseases, a number of
lung diseases, particularly chronic obstructive pulmonary diseases
(COPDs) including both asthma and emphysema, are increasing in
prevalence and COPD is expected to become the third leading cause
of disease mortality worldwide by 2020.
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Although important advances in symptomatic treatments have
occurred, many lung diseases including asthma, emphysema, pulmonary
fibrosis, cystic fibrosis, and others have no cure. Lung
transplantation is an option; however, there is a critical shortage
of donor lungs and transplantation is complicated by acute and
chronic rejection requiring lifelong immunosuppression. Further,
5-year mortality following lung transplantation is ~50%. New
approaches for lung diseases are thus desperately needed.
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"It's a paradigm shift," says Andre Terzic, M.D., Ph.D.,
director of Mayo Clinic's Center for Regenerative Medicine and
senior investigator of the stem cell trial. "We are moving from
traditional medicine, which addresses the symptoms of disease, to
being legitimately able to cure disease."Andre Terzic, M.D.,
Ph.D.Center for Regenerative Medicine
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A stem cell is a clonal, self-renewing entity that is
multipotent and thus can generate several differentiated cell
types
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The concept of stem cells originated at the end of the 19 th
century to account for the ability of certain tissues (blood, skin)
to self- renew despite the fact that they are composed of
short-lived cells. This was only a hypothesis
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In 1960, Till & McCulloch, demonstrated that a certain
population of bone marrow cells, when injected in mouse spleen,
formed colonies of differentiating cells (CFU-S). They proved the
clonal nature of the colonies.First concept: Differentiation
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In the same year, with the help of Lou Siminovitch, a molecular
biologist, they proved the self renewal potential of these
cells.Lou Siminovitch 2 nd Concept: Self-renewal
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During the subsequent decades, all research focused on
characterization & trial of isolation of this stem cell
population Two major scientific breakthroughs gave a great push to
stem cell research: Commercial cytokines Immunophenotyping using
flowcytometry
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The first logical use of BM stem cells was in hematological
disorders. BMT for hematological and non- hematological
malignancies began and the technique postulated & proved the
third stem cell characteristic: 3 rd Concept: Homing.
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The first sucessful BMT was performed back in 1968 for
treatment of SCID.
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The observations that there are circulating CD34+ve cells which
can be increased by certain agents, introduced PBSCT as an
alternative to BMT.
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Stem cell factors were the last cytokines to be synthesized.
For many years there was a dogma that Stem cells cannot be grown or
expanded in-vitro and we had to use experimental animals. The
introduction of SCF gave way to proving the 4 th concept:
Proliferation
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Observations after BMT or PBSCT paved the way for the last
& most interesting concept: 5 th concept: Plasticity
Observations following gender-mismatched transplants Observations
following multiple myeloma patients & effect on kidneys
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Definition: Transdifferentiation means the conversion of stem
cells from one committed lineage to the other. Types: A.
Spontaneous: one of the normal mechanisms of regeneration in the
human body B. Induced
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Embryonic stem cells: Sources of ES: IVF Nuclear Transfer Adult
stem cells
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Stem cells can be classified according to: Potency Source
Surface markers
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Embryonic Stem Cells From blastocysts left over from In-Vitro
Fertilization in the laboratory From aborted fetuses B. Adult Stem
Cells Stem cells have been found in the cord blood, bone marrow,
liver, kidney, cornea, dental pulp, umbilical cord, brain, skin,
muscle, salivary gland...
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Embryonic SC Pleuripotent Unlimited self- renewal (Advantage or
disadvantage) Possibility of rejection Adult SC Multipotent Limited
self-renewal Less immunogenic?
Slide 22
The source of stem cells may be bone marrow, peripheral blood,
cord blood or adipose tissue. Formerly, organ specific stem cells
were used (fetal or xenogenic)
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There are two types of BM stem cells: HSC & side population
SC
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Advantages: 1.More efficient stem cells (high telomerase
activity) 2.Higher plasticity 3.Cheap Disadvantages: 1. Low
frequency (1% CD34, 0.01% MSCs) 2. Painful procedure of acquisition
3. Life span decreases with age
Slide 29
Adult bone marrow-derived mesenchymal stem cells (MSCs) are
multipotent cells that are the subject of intense investigation in
regenerative medicine. They are one of the side-population stem
cells found in the bone marrow.
Slide 30
MSCs represent 0.001-0.01% of marrow nucleated cells. However,
they have several advantages: 1. Easy isolation 2. High expansion
potential 3. Stable gene expression 4. Reproducible chch
Slide 31
Advantages: 1.Non-invasive 2. Large quantities Disadvantages:
1. ?function
1. Hematologic reconstitution: classical use 2. Regenerative
medicine 3. Gene therapy 4. Immunotherapy
Slide 35
Stem cells are now proven to effectively regenerate various
tissues. The following are the clinical applications for stem cells
in regenerative medicine:
Over 4,500 clinical trials on stem cell therapy in 140
countries, 2,230 are running and FDA approved
Slide 39
In an average lifetime, human lungs take 20- 40 million breaths
and experience a daily airflow of between 7000 and 10,000 litrs.
Mammalian lungs are made up of two distinct regions: 1. The
conducting airway tubes, including the trachea, bronchi, and
bronchioles. 2. The gas exchange regions, or alveolar spaces.
Slide 40
As all body organs, lungs are rich in stem cells and progenitor
cells. In normal lungs, progenitor cells are present in abundance
throughout each region. These cells divide to replace old or
damaged lung cells, which keeps the lung healthy. The progenitor
cells include: tracheal basal cells, bronchiolar Clara cells, and
alveolar type 2 cells.
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I. Tissue Regeneration II. Vascularization III.
Immunomodulation
Slide 43
The question of whether non-lung stem and/or progenitor cells,
whether embryonic or adult in origin, can engraft and acquire
phenotype of structural lung cells following either systemic or
direct intratracheal administration remains controversial. Several
promising and provocative reports appeared in the early 2000's
suggesting that bone marrow- derived cells including hematopoietic
stem cells, MSCs, multipotent adult progenitor cells, and other
populations could structurally engraft as mature differentiated
airway and alveolar epithelial cells or as pulmonary vascular or
interstitial cells in mouse models as well as following clinical
bone marrow or lung transplantation
Slide 44
Later studies also examined potential engraftment using stem
and progenitor cells isolated from other tissues such as adipose,
placenta, cord, blood, and others.
Slide 45
Systemic administration of different populations of bone
marrow-derived cells results in rare epithelial engraftment but can
stimulate pulmonary vascular growth.
Slide 46
Through in vitro studies, animal models, and clinical trials in
non-lung diseases, it has been demonstrated that MSCs can suppress
activation, proliferation, and effector functions of cells in both
the innate and adaptive immune system, as well as promoting the
development of immune cells typically associated with immune
suppression such as T-regulatory cells
Slide 47
Schematic illustrating the range of in vitro immune- modulating
effects described for mesenchymal stem cells (MSCs). DC = dendritic
cell; HGF = hepatocyte growth factor; IDO = indoleamine 2,3-
dioxygenase; IFN- = interferon ; Ig = Immunoglobulin; IL =
Interleukin; IL-1RA = Interleukin-1 receptor antagonist; Mac =
Macrophage; NK = natural killer; PGE2 = prostaglandin E- 2; SDF-1 =
stem- cell derived factor 1; TNF- = tumor necrosis factor-; TGF-1 =
transforming growth factor- 1; TLR = Toll- like receptor; VEGF =
vascular endothelial growth factor. Reprinted with permission from
Reference 412.
Slide 48
Pulmonary fibrosis Current hypotheses suggest that pathogenesis
results from a chronic indolent uncontrolled cycle of epithelial
damage and fibroblast activation. In the first study to demonstrate
ameliorating effects of MSCs in lung injuries, mice were exposed to
a lung fibrosis-inducing agent, bleomycin, followed by systemic MSC
administration. Although only a small number of MSCs appeared to
have engrafted in the lung, significant reductions in lung
inflammation and damage, collagen deposition, and other markers of
injury occurred. A subsequent study suggested interleukin-1
receptor antagonist (IL-1RA) secreted by the MSCs as responsible
for the anti- inflammatory effects. A number of other reports have
since confirmed the beneficial effects of MSC administration in the
bleomycin model of pulmonary fibrosis although the mechanisms by
which the MSCs are acting have not yet been fully elucidated.
Slide 49
Acute lung injury/sepsis Acute lung injury (ALI) is a result of
local or systemic inflammation that leads to disruption of the
alveolar-capillary interface, leakage of protein rich fluid and
inflammatory cells into the interstitium and alveolar space, and
extensive release of inflammatory cytokines. MSC administration
generally improved survival and function of sepsis-damaged organs
such as the kidney. In parallel, both lung inflammation and levels
of circulating proinflammatory cytokines and chemokines were
improved by MSC treatment. MSC treatment also resulted in
significantly decreased bacterial burden and enhanced bacterial
phagocytosis and clearance.
Slide 50
Several mechanisms have been proposed to explain these
findings: release of soluble mediators by MSCs that may work in
part to enhance antibacterial and anti- inflammatory effects of
inflammatory cells such as macrophages and neutrophils. MSCs
themselves are capable of secreting at least one antimicrobial
peptide, the human cathelicidin antimicrobial peptide hCAP-18/LL-
37. MSCs may also be useful in preventing ischemia- reperfusion
injury. These preclinical studies demonstrate that MSCs may be
useful in clinical sepsis and septic shock
Slide 51
Pulmonary hypertension Although EPCs have been more heavily
investigated for use in pulmonary hypertension, several reports
have demonstrated efficacy of MSC administration in both mice and
rats. As with EPCs, it is not clear whether the MSCs themselves
participate in angiogenesis or whether secretion of anti-
inflammatory substances ameliorate the experimentally induced
injury that results in vascular obliteration. Further, MSCs
genetically engineered to overexpress molecules known to have
beneficial effects in pulmonary hypertension such as endothelial
nitric oxide synthase, prostacyclin, or heme oxygenase 1 were even
better able to offer protective effects and in some cases,
completely reverse the pulmonary hypertensive phenotype and
increase survival. MSCs may thus be a valuable alternate or adjunct
to use of EPCs for treatment of pulmonary hypertension.
Slide 52
Bronchopulmonary dysplasia In diseases of prematurity,
pulmonary hypoplasia and bronchopulmonary dysplasia account for 70%
of neonatal mortality. Several recent studies demonstrate efficacy
or MSC administration in rodent models of hyperoxic lung injury,
utilized to understand mechanisms of bronchopulmonary dysplasia
pathogenesis. PGE2 and tumor necrosis factor-inducible gene 6
(TSG-6) secreted by the MSCs have been suggested to mediate the MSC
effects in these models. However, the overall mechanisms of MSC
effects to ameliorate hyperoxia-induced lung injury remain unclear.
However potential clinical use of MSCs in infants remains a
controversial subject.
Slide 53
Chronic obstructive airways diseases: asthma, emphysema,
bronchiolitis obliterans Allergic asthma, defined as airways
hyperresponsiveness and inflammation in response to an inhaled
allergen, is a disease driven by dendritic cells, CD4 Th2
lymphocytes and B lymphocytes. As proliferation and specific immune
effector functions of each of these cell types can be inhibited by
MSCs in vitro, allergic asthma is a logical choice for potential
intervention with MSCs. As such, there are now a number of studies
demonstrating amelioration of airways hyperresponsiveness and lung
inflammation in mouse models of allergic airways inflammation.
Slide 54
Notably, MSCs can inhibit both the initial allergen
sensitization as well as the subsequent response to an allergen
challenge in a previously sensitized animal. Some specific
mechanisms of MSC actions have been defined in these models
including shifting of antigen- specific CD4 T cell phenotype from
Th2 to Th1 as well as upregulation of T-regulatory T cells by
release of transforming growth factor (TGF) by the MSCs. Each of
these actions can ameliorate allergic airways inflammation. Likely
there are other mechanisms of MSC actions involved that are still
to be elucidated. Given the positive results in these studies, it
is likely that clinical trials of MSCs in severe asthma will occur
in the near future.
Slide 55
Lung cancers Bone marrow-derived MSCs and EPCs may contribute
to development of primary and metastatic lung carcinoma and other
malignancies, notably breast and ovarian cancers, in mouse models.
These cells function, in part, by providing a supportive stroma for
the cancers and/or by participating in tumor vascularization. In
contrast, MSCs and EPCs have been demonstrated to home to areas of
tumor development and EPCs and MSCs engineered to secrete antitumor
agents have been utilized to suppress tumor growth in mouse tumor
models of primary lung cancers, metastatic lung cancers, and of
other cancers metastatic to the lung. Cell-based therapies may thus
be useful in lung cancer therapeutics.
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This study was done to investigate the effect of CB-MSCs on
amiodarone lung fibrosis murine model
