Injection of mesenchymal stromal cells (MSCs) — cells that can be isolated from several tissues and may grow into different cell types when cultured in a lab dish — may prevent localized skin blistering sometimes seen in recessive dystrophic epidermolysis bullosa (RDEB), a study says.
Results from the study, “Human mesenchymal stromal cells engineered to express collagen VII can restore anchoring fibrils in recessive dystrophic epidermolysis bullosa skin graft chimeras,” were published in The Journal of Investigative Dermatology.
RDEB is a rare and incurable form of epidermolysis bullosa (EB), a genetic skin disorder in which the patients’ skin blisters and tears easily, causing painful wounds and scarring. RDEB is caused by genetic mutations in the COL7A1 gene, which provides instructions to make a protein called type 7 collagen (COL7) that is essential to maintain healthy skin.
“With no curative treatments presently available, … various therapeutic strategies are under development,” researchers explained. These include injections of the missing protein, either into the blood or into the affected site directly, injection of skin cells (fibroblasts) from genetically similar donors, blood stem cell transplants, and gene therapy approaches.
The use of donor-derived MSCs is being explored as an alternative treatment method for RDEB. When delivered into the skin, MSCs appear to support the “long-term production of COL7 and the formation of anchoring fibrils,” the structures that allow skin layers to adhere and prevent blistering.
Researchers from the UCL Great Ormond Street Institute of Child Health (GOS ICH) in London, England, hypothesized that engineering MSCs to produce higher amounts of COL7 could increase their benefits.
To test that hypothesis, they genetically engineered human MSCs that had been isolated from a healthy female donor to produce large amounts of COL7.
They then mixed the modified MSCs with RDEB fibroblasts and keratinocytes that lacked COL7 to create a lab-made skin graft. Skin grafts that did not contain engineered MSCs were used as controls. (Of note, fibroblasts are connective tissue cells that normally produce collagen, whereas keratinocytes are the main cell type that form the top layer of the skin.)
The final step involved transplanting the lab-made skin grafts into immuno-compromised mice (animals that lacked a functional immune system and were unable to reject the skin graft), where the skin grafts were allowed to grow for a period of 8-10 weeks.
Imaging analysis showed the genetically-modified MSCs were successfully incorporated into the RDEB grafts. Moreover, they found that RDEB grafts containing modified MSCs were able to form a normal dermal-epidermal junction (DEJ) — the area between the top and the lower layers of the skin — and showed no signs of blistering.
In addition, analysis of the MSCs’ skin grafts by transmission electron microscopy confirmed anchoring fibrils formed normally.
Finally, to test if modified MSCs may induce the same effects when injected locally in the skin, investigators injected MSCs intradermally into RDEB skin grafts that had been implanted into immuno-compromised mice.
They found these MSCs were able not only to incorporate into the skin graft, but also to trigger the production and deposition of COL7, restoring the formation and density of anchoring fibrils to normal levels.
On the other hand, when they attempted to deliver MSCs by an intravenous injection, none of the engineered cells was found on the skin grafts and the reconstitution of anchoring fibrils failed.
“In summary our data suggests that therapeutic benefits at sites of localized blistering might be achievable using directly injected MSCs engineered to overexpress COL7,” the researchers concluded.
They added that “banks of engineered MSCs that can be used in multiple recipients could have cost and convenience advantages over strategies that require engineering of autologous fibroblasts.”
However, because the disease is not localized and usually affects the entire body, the scientists call for “further modeling and evaluation of strategies for more generalized delivery and enhanced homing to sites of tissue disease.”