OBJECTIVE:Despite significant improvement in spinal cord function after in utero spina bifida (SB) repair compared with traditional postnatal repair, over half of the children who undergo this procedure do not benefit completely. This lack of benefit has been attributed to closure methods of the defect, with subsequent spinal cord tethering at the repair site. Hence, a regenerative patch or material with antiinflammatory and anti-scarring properties may alleviate comorbidities with improved outcomes. The authors' primary objective was therefore to compare cryopreserved human umbilical cord (HUC) versus acellular dermal matrix (ADM) patches for regenerative repair of in utero SB lesions in an animal model. METHODS:In vivo studies were conducted in retinoic acid-induced SB defects in fetuses of Sprague-Dawley rats. HUC or ADM patches were sutured over the SB defects at a gestational age of 20 days. Repaired SB defect tissues were harvested after 48-52 hours. Tissue sections were immunofluorescently stained for the presence of neutrophils, macrophages, keratinocytes, meningeal cells, and astrocytes and for any associated apoptosis. In vitro meningeal or keratinocyte cell coculture experiments with the ADM and HUC patches were performed. All experiments were scored quantitatively in a blinded manner. RESULTS:Neutrophil counts and apoptotic cells were lower in the HUC-based repair group (n = 8) than in the ADM patch repair group (n = 7). In the HUC patch repair group, keratinocytes were present on the outer surface of the patch, meningeal cells were present on the inner surface of the patch adjacent to the neural placode, and astrocytes were noted to be absent. In the ADM patch repair group, all 3 cell types were present on both surfaces of the patch. In vitro studies showed that human meningeal cells grew preferentially on the mesenchymal side of the HUC patch, whereas keratinocytes showed tropism for the epithelial side, suggesting an inherent HUC-based cell polarity. In contrast, the ADM patch studies showed no polarity and decreased cellular infiltration. CONCLUSIONS:The HUC patch demonstrated reduced acute inflammation and apoptosis together with superior organization in regenerative cellular growth when compared with the ADM patch, and is therefore likely the better patch material for in utero SB defect repair. These properties may make the HUC biomaterial useful as a "meningeal patch" during spinal cord surgeries, thereby potentially reducing tethering and improving on spinal cord function.