Perinatal regenerative medicine : development of autologous constructs for soft tissue defects

Abstract

Disrupted organogenesis leads to permanent malformations that may require surgical correction. Affected new-borns without spare tissue for the primary closure are dependent of other solutions. Because of the perinatal tissue shortage, synthetic or biological prosthetic materials are being used, which may be associated with complications. The progress in cell-based therapies makes autologous tissue engineering a rational alternative to current treatments, and infants with prenatally diagnosed soft tissue defects should benefit from having autologous tissue readily available for surgical implantation in the perinatal period. The aim of this thesis was to investigate cell and tissue sources harvested pre- or postnatally for development of autologous constructs that could be used in the correction of congenital soft tissue defects. We sought a reliable and clinical feasible isolation and culture method, a cell or tissue source with minimal or no donor site morbidity and high yield of viable cells with minimal handling or additives. Amniotic fluid (AF) can easily be obtained during routine amniocentesis for foetal karyotyping and in study I, we investigated the cell content in AF and the isolation and expansion potential of AF cells (AFC). The study showed that AF displayed large donor variability with varying isolation and expansion success of the AFC, and therefore it may not be the best source for autologous cell therapy. A small tissue biopsy could also be obtained during amniocentesis, and in study II we investigated foetal subcutaneous cells (fSC) as cellular source for tissue engineering. We also combined the expanded fSC with two different matrices; cell free small intestine submucosa (SIS) and collagen gel combined with poly(ε-caprolactone). The cells showed low adherence to SIS and did not migrate deep into the matrix. However, in collagen gels the cells migrated into the gel and proliferated with sustained viability for up to 8 weeks. The fSC demonstrated a high proliferative capacity and favourable characteristics for the preparation of autologous tissue transplants before birth. In study III we explored two postnatal tissue sources; the amnion membrane from term placenta and a gel made of plasma rich in growth factors (PRGF) from umbilical cord blood (UCB). The amnion and the gel were combined with SIS to form constructs. The constructs do not include cell expansion in vitro, can be made promptly after birth with minimal handling and can be stored for to 2-3 weeks if the surgical correction is performed later. Our study showed that amnion and UCB are promising sources for production of autologous grafts for the correction of congenital soft tissue defects. The main conclusion of this thesis is that depending on the timeframe from diagnosis to birth and type, size and severity of the defect, either 2nd trimester fSC, term amnion or PRGF gel are the preferable perinatal sources for autologous tissue engineering and correction of the congenital soft tissue defect.