Shaun A. Steigman, MD, Avery Ching, MD, Azra Ahmed, BS, Melissa J. Hayward, MD, Meghna Misra, MD, Michael J. Giuffrida, MD, Taturo Udagawa, PhD, Dario O. Fauza, MD
Department of Surgery, Children's Hospital Boston; Boston, MA
PURPOSE OF STUDY
Fetal wound healing involves minimal inflammation and limited scarring. The mechanisms responsible for this unique regenerative process remain poorly elucidated. We hypothesized that naturally occurring amniotic mesenchymal stem cells (AMSCs) participate in fetal wound healing.
Fetal lambs (n=12) underwent a thoracotomy closed in layers at 88.3+2.8 days gestation (term=145 days), concomitant with amniotic fluid procurement. AMSCs were isolated, expanded, and characterized by flow cytometry. Expanded cells were labeled by retroviral transfection with green fluorescent protein (GFP) and quantified by flow cytometry. Survivors (n=11) underwent a second operation at 123.4+2.3 days gestation, when a cervicotomy closed in layers was performed and the amniotic cavity was instilled with autologous labeled AMSCs (3.99x105 to 2.86x109 cells). A sub-set of animals also underwent ear resections (n=8 wounds) at that time, left to heal by secondary intention. Survivors (n=10) had their wounds analyzed 7-14 days thereafter by various techniques, including immunohistochemistry using a monoclonal anti-GFP antibody.
SUMMARY OF RESULTS:
The immunophenotype of expanded cells was consistent with that of mesenchymal progenitors. Labeled cells were documented in all thoracic, cervical, and ear wounds, albeit seemingly at a lower density in the thoracotomies. Interestingly, labeled cells could be detected within the cartilage in several ear specimens.
Amniotic mesenchymal stem cells seem to participate in primary and secondary intention fetal wound healing and in ensuing wound remodeling. These cells also incorporate into injured cartilage. To our knowledge, this is the first reported biological role for these cells. These findings lend further support to the use of AMSCs in various regenerative therapies.