Anna B. Katz

Adenoviral mediated gene transfer of PDGF-B enhances wound healing in type I and type II diabetic wounds

We have shown that the genetically diabetic mouse (C57BLKS/J‐m+/+Leprdb) has a wound healing and neovascularization deficit associated with an inability to recruit endothelial precursor cells (EPCs) to the wound. This may account for a fundamental mechanism in impaired diabetic wound healing. We hypothesized that the adenoviral mediated overexpression of platelet‐derived growth factor‐B (PDGF‐B) would enhance wound healing, improve neovascularization, and recruit EPCs to the epithelial wound in three diabetic mouse models. Eight‐mm full‐thickness flank wounds were made in db/db, nonobese NOD/Ltj, streptozotocin, and C57BLKS/J mice. Wounds were treated with either 1 × 108 PFU Ad‐PDGF‐B or Ad LacZ or phosphate buffered saline solution. Wounds harvested at seven days were analyzed for epithelial gap, blood vessel density, granulation tissue area, and EPCs per high powered field. All three diabetic models have a significant wound healing and neovascularization defect compared to C57BLKS/J controls. Adenoviral‐PDGF‐B treatment significantly enhanced epithelial gap closure in db/db, streptozotocin, and nonobese NOD/Ltj mice as compared to diabetic phosphate buffered saline solution or Ad LacZ controls. A similar increase in the formation of granulation tissue and vessel density was also observed. All three models had reduced levels of GATA‐2 positive EPCs in the wound bed that was corrected by the adenoviral mediated gene transfer of PDGF. EPC recruitment was positively correlated with neovascularization and wound healing. Three different diabetic models have a wound healing impairment and a decreased ability to recruit EPCs. The vulnerary effect of adenoviral mediated gene therapy with PDGF‐B significantly enhanced wound healing and neovascularization in diabetic wounds. The PDGF‐B mediated augmentation of EPC recruitment to the wound bed may be a fundamental mechanism of these results.

Permissive environment in postnatal wounds induced by adenoviral-mediated overexpression of the anti-inflammatory cytokine interleukin-10 prevents scar formation

Wound healing in the mid‐gestation fetus is scarless with minimal inflammation and a unique extracellular matrix. We have previously documented the relative lack of inflammatory cytokines in this environment. We demonstrate that interleukin (IL)‐10 is highly expressed in mid‐gestation human fetal skin but is absent in postnatal human skin. We hypothesize that overexpression of IL‐10 in postnatal skin may replicate a permissive environment for scarless healing. To study the mechanism underlying this process we performed immunohistochemistry for IL‐10 in human mid‐gestation fetal and postnatal skin. We also determined if adenoviral‐mediated overexpression of IL‐10 could allow for scarless wound healing in a murine incisional wound model. Wounds were analyzed at 1–90 days postwounding for effects on scar formation, inflammatory response, and biomechanical properties. Ad‐IL‐10 reconstitutes a permissive environment for scarless healing as shown by reconstitution of a normal dermal reticular collagen pattern and distribution of dermal elements. Compared with controls, Ad‐IL‐10 treated wounds showed reduced inflammatory response and no difference in biomechanical parameters. Therefore, overexpression of IL‐10 in postnatal wounds results in a permissive environment for scarless wound repair, possibly by replicating a fetal wound environment.

Placental gene transfer: transgene screening in mice for trophic effects on the placenta.

OBJECTIVE We hypothesized that gene transfer of select growth factors to the placenta may enhance placental and fetal growth. Thus, we examined the effect of 8 growth factor transgenes on murine placenta. STUDY DESIGN Adenoviral-mediated site-specific intraplacental gene transfer of 8 different growth factor transgenes at embryonic day (e) 14 was performed. Transgenes included angiopoietin-1, angiopoietin-2 (Ang-2), basic fibroblast growth factor, hepatocyte growth factor, insulin-like growth factor-1 (IGF-1), placenta growth hormone, platelet-derived growth factor-B (PDGF-B), and vascular endothelial growth factor(121). Fetuses and placentas were harvested at e17 and assessed for survival, gene transfer efficiency, placenta area, and fetal and placental weights. RESULTS Efficient gene transfer to the placenta was detected with minimal dissemination to the fetus. Overexpression of IGF-1, PDGF-B, and Ang-2 resulted in an increase in placenta cross-sectional area. Only Ang-2 gene transfer resulted in increased fetal weight, and only Ang-2 and basic fibroblast growth factor resulted in a change in placental weight. CONCLUSION Site-specific placental gene transfer results in efficient gene transfer with minimal dissemination to the fetus. Adenoviral-mediated IGF-1, adenoviral-mediated PDGF-B, and adenoviral-mediated Ang-2 significantly increase placenta growth.

Pseudotyped AAV Vector-Mediated Gene Transfer in a Human Fetal Trachea Xenograft Model: Implications for In Utero Gene Therapy for Cystic Fibrosis

Background Lung disease including airway infection and inflammation currently causes the majority of morbidities and mortalities associated with cystic fibrosis (CF), making the airway epithelium and the submucosal glands (SMG) novel target cells for gene therapy in CF. These target cells are relatively inaccessible to postnatal gene transfer limiting the success of gene therapy. Our previous work in a human-fetal trachea xenograft model suggests the potential benefit for treating CF in utero. In this study, we aim to validate adeno-associated virus serotype 2 (AAV2) gene transfer in a human fetal trachea xenograft model and to compare transduction efficiencies of pseudotyping AAV2 vectors in fetal xenografts and postnatal xenograft controls. Methodology/Principal Findings Human fetal trachea or postnatal bronchus controls were xenografted onto immunocompromised SCID mice for a four-week engraftment period. After injection of AAV2/2, 2/1, 2/5, 2/7 or 2/8 with a LacZ reporter into both types of xenografts, we analyzed for transgene expression in the respiratory epithelium and SMGs. At 1 month, transduction by AAV2/2 and AAV2/8 in respiratory epithelium and SMG cells was significantly greater than that of AAV2/1, 2/5, and 2/7 in xenograft tracheas. Efficiency in SMG transduction was significantly greater in AAV2/8 than AAV2/2. At 3 months, AAV2/2 and AAV2/8 transgene expression was >99% of respiratory epithelium and SMG. At 1 month, transduction efficiency of AAV2/2 and AAV2/8 was significantly less in adult postnatal bronchial xenografts than in fetal tracheal xenografts. Conclusions/Significance Based on the effectiveness of AAV vectors in SMG transduction, our findings suggest the potential utility of pseudotyped AAV vectors for treatment of cystic fibrosis. The human fetal trachea xenograft model may serve as an effective tool for further development of fetal gene therapy strategies for the in utero treatment of cystic fibrosis.

Submucosal gland development in the human fetal trachea xenograft model: implications for fetal gene therapy☆

BACKGROUND/PURPOSE Our previous work in a human-fetal trachea xenograft model suggests potential benefits of treating cystic fibrosis in utero. The target for postnatal gene therapy in cystic fibrosis is tracheal submucosal glands (SMGs). The aim of this study was to determine if SMG development in our model recapitulates normal trachea development and its validity for studying fetal gene transfer. METHODS Fetal tracheas were divided into developmental phases: early, mid, and late. Fetal tracheas were xenografted onto immunocompromised mice and analyzed for SMG developmental staging and mucopolysaccharide production. RESULTS There were no significant differences in gland number, size, or density from early through late phase between groups. Xenografted tracheas demonstrated a similar progression through the stages of SMG development as controls after an initial phase shift. Control and xenografted tracheas demonstrated characteristic patterns of acidic mucin production at the base of the SMGs. CONCLUSIONS Fetal trachea xenograft SMG recapitulates normal development and is a valid model for studying human fetal gene transfer. The accessibility of SMG stem cells in early tracheal development may afford a unique window of opportunity for gene transfer. This model has the benefit of providing access to human fetal tracheas in vivo and permits the study of novel fetal gene therapy strategies.