Pulmonary hypertension, high pressure in the blood vessels of the lungs, is a common and serious complication of chronic lung diseases, including idiopathic pulmonary fibrosis (IPF).
IPF is a type of interstitial lung disease, which causes progressive scarring, leading to the lung tissue thickening and stiffening. In particular, it affects the interstitium, or the area between the alveoli where gas exchange takes place in the lungs, and the blood vessels. The scar tissue reduces lung capacity and restricts gas exchange, resulting in less oxygen being transferred to the blood.
The exact mechanism through which IPF can cause pulmonary hypertension is not well understood, but it is thought that the scarring restricts blood vessels, impeding blood flow and making it more difficult for the heart to pump blood through the lungs. Another theory is that the damage response and resulting scar tissue reactivates pathways involved in lung development and triggers vascular remodelling. This can change the shape of the blood vessels, such as causing them to narrow and restrict blood flow.
IPF is a debilitating and fatal condition, and while current therapies can help to improve survival and quality of life, there is no known cure. However, research into promising approaches like stem cell therapy is ongoing.
What is stem cell therapy?
The body is made up of many different types of specialised cells that fulfil specific functions.
Once a cell is specialised, it generally cannot change and will only divide to produce similar cells. Stem cells are different in that they have the potential to develop and specialise into multiple different types of cells. Depending on where the stem cell originates, the type and range of cells it can develop into will differ.
By administering stem cells to IPF patients, it may be possible to generate the new lung tissue necessary for effective gas exchange.
Mesenchymal stem cells (MSCs) are now being investigated to treat IPF due to their ability to potentially reduce inflammation in the lungs. Damage caused by inflammation can lead to scarring in the lungs, so reducing lung inflammation may be able to lessen further scarring.
MSCs can be obtained from various tissues, including the adult bone marrow, umbilical cord blood, and the placenta.
Stem cell therapy in clinical trials for IPF
Both ongoing and completed clinical trials have investigated stem cell therapy in IPF patients.
A proof-of-concept, open-label Phase 1 clinical trial (NCT01385644), carried out at The Prince Charles Hospital in Brisbane, Australia, aimed to determine whether MSC therapy was safe and feasible. The study enrolled eight IPF patients, who received either a high or low concentration of MSCs. Trial results, published in the journal Respirology, suggested that the therapy is feasible and both doses were well-tolerated, with only minor and short-term adverse effects. At six months after treatment, the patients showed no worsening in their condition.
A Phase 1 randomized and blinded, placebo-controlled clinical trial, called AETHER (NCT02013700), enrolled 25 IPF patients at the Interdisciplinary Stem Cell Institute at the University of Miami. The trial aimed to assess the safety of MSC therapy, and gain a preliminary idea of its efficacy over a 60-week period. Participants were randomly assigned a single dose of one of three concentrations of MSCs or to a placebo. The trial is ongoing, but no longer recruiting participants.
Results from nine patients, who were treated and monitored for the full 60 weeks, have been published in the scientific journal, Chest. These results did not include a placebo arm. The treatment appeared to be well-tolerated and no serious side effects due to the therapy were recorded. However two patients died for reasons attributed to disease progression.
The only study currently recruiting patients is a Phase 1/2 clinical trial (NCT02745184) taking place at two sites in China. Researchers intend to isolate lung stem cells from the patient’s own bronchi (the large tubes of the lungs) and expand them in the laboratory. About 20 enrolled patients will then receive a single injection of their cultured lung stem cells directly into the area affected by IPF.
To assess the safety of the treatment, patients will be monitored for side effects for up to one year. Efficacy will be measured by changes in several lung function and exercise ability tests. The primary test, at 48 weeks post-treatment, will be the change in forced vital capacity (FVC), or the volume of air that can be quickly exhaled after a deep breath. The trial is expected to finish in December 2018.
