Hypoxia affects human mesenchymal stem cell secretome independent of nutrients

A study designed to characterize the secretome of human mesenchymal stem cells in ischemic, hypoxic or normoxic conditions showed the cells release mediators based on nutrient availability, regardless of the oxygen level.

“The take-home message of my study could be hypoxia promotes chemotactic and pro-angiogenic potential of human mesenchymal stem cells (hMSCs) secretome,” Joseph Paquet, PhD, of Paris, told Orthopaedics Today Europe.

He is scheduled to present the results of the basic science study, which was selected as one of the top papers, at the EFORT Congress – A Combined Program in Partnership With the BOA in London.

Better understanding

According to Paquet, it was important to study whether the benefits of hMSCs can be conferred through transitory paracrine effects via all kinds of secreted chemical compounds since much about using these cells in regenerative medicine is still unknown. The investigators used MSCs from the bone marrow of five patients undergoing orthopaedic procedures and exposed them to an ischemic environment of pO2=0.1%, serum deprived, an hypoxia environment of pO2=0.1%, 5g/L glucose, and a normoxic environment of pO2=21%. Hypoxia was sustained for 21 days using a hypoxic station (Biospherex; Lacona, N.Y., USA).

In the lab, when there is no chance for vascularization and extremely low levels of oxygen, hMSCs die after 10 days, Paquet said.

“It is not so good. Therefore, we decided to focus on paracrine potential of mesenchymal stem cells in these conditions,” he said.

Over 21 days Paquet and colleagues assessed various levels of mediators that are chemo-attractant, inflammatory and immunomodulative using conditioned media or by seeding the cells on matrigel. In addition, they assessed how the secreted mediators functioned in vivo.

In vitro model

“By using an in vitro model of ischemia/hypoxia, we first demonstrated that hMSC secretome is deeply affected, quantitatively and qualitatively, by the presence or no nutrients (i.e., glucose) under hypoxia,” the investigators wrote in the abstract.

They further noted the mediators produced by the hMSCs in the hypoxic environment they looked at showed signs of selectivity.

“Immunomodulatives and inflammatory mediators currently described to be secreted by hMSCs, under ‘normoxic conditions,’ are not expressed and secretome profile is focused on pro-angiogenic and chemo-attractive chemical compounds,” they wrote.

Paquet said what is new or different about his study is “the conditions where we worked because many studies consider hypoxic conditions at 5% of oxygen or 2%, but what we did was to study it in pO2=0.1%. At 5% of oxygen the cells behave like normal hypoxic conditions. I have not seen any study with very low oxygen.”

Paquet said his group is working with adipose stem cells to see if they behave similarly in these same conditions. – by Susan M. Rapp

Disclosure: Paquet has no relevant financial disclosure.

A study designed to characterize the secretome of human mesenchymal stem cells in ischemic, hypoxic or normoxic conditions showed the cells release mediators based on nutrient availability, regardless of the oxygen level.

“The take-home message of my study could be hypoxia promotes chemotactic and pro-angiogenic potential of human mesenchymal stem cells (hMSCs) secretome,” Joseph Paquet, PhD, of Paris, told Orthopaedics Today Europe.

He is scheduled to present the results of the basic science study, which was selected as one of the top papers, at the EFORT Congress – A Combined Program in Partnership With the BOA in London.

Better understanding

According to Paquet, it was important to study whether the benefits of hMSCs can be conferred through transitory paracrine effects via all kinds of secreted chemical compounds since much about using these cells in regenerative medicine is still unknown. The investigators used MSCs from the bone marrow of five patients undergoing orthopaedic procedures and exposed them to an ischemic environment of pO2=0.1%, serum deprived, an hypoxia environment of pO2=0.1%, 5g/L glucose, and a normoxic environment of pO2=21%. Hypoxia was sustained for 21 days using a hypoxic station (Biospherex; Lacona, N.Y., USA).

In the lab, when there is no chance for vascularization and extremely low levels of oxygen, hMSCs die after 10 days, Paquet said.

“It is not so good. Therefore, we decided to focus on paracrine potential of mesenchymal stem cells in these conditions,” he said.

Over 21 days Paquet and colleagues assessed various levels of mediators that are chemo-attractant, inflammatory and immunomodulative using conditioned media or by seeding the cells on matrigel. In addition, they assessed how the secreted mediators functioned in vivo.

In vitro model

“By using an in vitro model of ischemia/hypoxia, we first demonstrated that hMSC secretome is deeply affected, quantitatively and qualitatively, by the presence or no nutrients (i.e., glucose) under hypoxia,” the investigators wrote in the abstract.

They further noted the mediators produced by the hMSCs in the hypoxic environment they looked at showed signs of selectivity.

“Immunomodulatives and inflammatory mediators currently described to be secreted by hMSCs, under ‘normoxic conditions,’ are not expressed and secretome profile is focused on pro-angiogenic and chemo-attractive chemical compounds,” they wrote.

Paquet said what is new or different about his study is “the conditions where we worked because many studies consider hypoxic conditions at 5% of oxygen or 2%, but what we did was to study it in pO2=0.1%. At 5% of oxygen the cells behave like normal hypoxic conditions. I have not seen any study with very low oxygen.”

Paquet said his group is working with adipose stem cells to see if they behave similarly in these same conditions. – by Susan M. Rapp

Disclosure: Paquet has no relevant financial disclosure.