Biomedical subjects

K G Sylvester

Publications and source records attributed to K G Sylvester.

11 recordsLinked to original sources

PubMed1999

BAPS Prize--1997. Fetal gene therapy: efficacy, toxicity, and immunologic effects of early gestation recombinant adenovirus. British Association of Paediatric Surgeons.

BACKGROUND/PURPOSE: Advancements in gene transfer technology and prenatal diagnosis have allowed investigators to consider an in utero gene therapy approach for fatal genetic diseases. The authors sought to develop fetoscopic techniques for gene delivery and investigate the efficacy and safety of recombinant adenoviral vectors in the fetus. METHODS: Fetal sheep between 60 and 130 days' gestation (dGA) underwent either fetoscopic intratracheal injection or umbilical vein (UV) injection of recombinant adenovirus, AdCMVlacZ. At death, fetal organs were examined for beta-galactosidase expression, histopathology, and CD45 immunostaining. Fetal serum was compared with preimmune serum for transaminase levels and the presence of antiadenoviral neutralizing antibodies. RESULTS: Fetoscopic intratracheal delivery of AdCMVlacZ in late-gestation sheep fetuses resulted in efficient alveolar gene transfer, but, antiadenoviral immunologic reactions limited the longevity of transgene expression to 14 days. This prompted an examination of whether early gestational exposure could induce tolerance in the fetus to adenoviral and transgene antigens. AdCMVlacZ (1 x 10(11) particles) was injected via UV into fetuses at 60 dGA. Within 3 days, beta-galactosidase expression was localized to the fetal liver, adrenal glands, kidneys, and endocardium. Although adrenal expression was nearly constant over 28 days, expression in fetal liver disappeared within 14 to 28 days. Loss of hepatic expression did not appear to be immune mediated because there was no evidence of hepatic inflammation or appearance of antiadenoviral neutralizing antibodies. Fetuses injected with AdCMVlacZ at 60 dGA were reinjected with 1 x 10(13) particles at 125 dGA and antiadenoviral humoral immune responses were recorded. Despite early-gestation adenovirus injection, fetuses still responded to the late-gestation adenoviral exposure, developing antiadenoviral neutralizing antibodies similar to control fetuses. CONCLUSIONS: The authors developed fetoscopic access for pulmonary adenovirus delivery in late-gestation sheep. Although initial alveolar transduction was highly efficient, antiadenoviral immune responses limited the duration of transgene expression. In contrast, early-gestation adenoviral delivery did not elicit antiadenoviral immune responses despite achieving efficient transduction of many fetal tissues. Furthermore, early-gestation adenovirus delivery did not affect late-gestation antiadenoviral immune responses. These findings suggest that the early-gestation sheep fetus is not amenable to adenoviral tolerance induction by UV injection and that it is incompetent of immunologic response to adenovirus. For the purposes of in utero gene therapy, recombinant adenovirus may be applied optimally to genetic diseases requiring transient in utero expression.

Adenoviridae↗

PubMed1999

TGF-beta2 is increased after fetal tracheal occlusion.

BACKGROUND/PURPOSE: Fetal tracheal occlusion (TO) accelerates lung growth in normal and hypoplastic fetal lung. The mechanism of accelerated lung growth remains unknown but may be a result of growth factor induction. Previous studies of growth factors induced by tracheal ligation have characterized mRNA rather than protein expression. Although the transforming growth factor-beta (TGF-beta) family participates in normal lung morphogenesis, its role in lung growth after TO is unclear. The authors hypothesize that TGF-beta expression is increased with TO and may contribute to the accelerated lung growth seen after TO. METHODS: Diaphragmatic hernia (DH) was created in 80-day-gestation sheep (n = 6; term, 145) by excising the left diaphragm. At 110 days, the trachea was occluded (n = 4) with a clip. DH controls (n = 2) were not occluded. Fetuses were killed at 139 days, and lung samples were snap frozen for tissue analysis. Non-DH control lungs were harvested from full-term animals (n = 2). TGF-beta mRNA was analyzed by semiquantitative reverse transcriptionase-polymerase chain reaction (RT-PCR). TGF-beta protein was assessed by Western blot analysis. RESULTS: TGF-beta1 mRNA and protein were not increased with tracheal ligation compared with either non-DH or DH controls. TGF-beta2, however, was markedly increased, at both the mRNA and protein level, in ligated lungs compared with nonligated controls. CONCLUSIONS: TGF-beta2 protein, but not TGF-beta1, is increased in the hypoplastic lungs of fetal sheep after tracheal occlusion. Increased TGF-beta2 expression appears to result from increased or prolonged expression of mRNA transcripts. This is the first study to document a change in growth factor protein levels after TO. Increased TGF-beta2 expression may contribute to accelerated lung growth and decreased surfactant production observed after tracheal occlusion.

Animals↗

PubMed1998

Epidermal integrin expression is upregulated rapidly in human fetal wound repair.

BACKGROUND/PURPOSE: The fetus heals skin wounds rapidly and scarlessly. The mechanisms that mediate the rapid reepithelialization that is seen in this process are unknown. Integrins are a family of cell surface receptors that bind fibronectin, tenascin, collagen, and other extracellular matrix proteins that are deposited rapidly in fetal wounds. The authors hypothesized that epidermal integrin receptors specific for fibronectin and other wound matrix proteins are upregulated rapidly during human fetal repair. METHODS: To investigate the spatial and temporal expression of integrins in scarless fetal repair, fetal skin from six human abortuses (16 to 23 weeks' gestation) was transplanted subcutaneously into severe combined immunodeficient mice. After graft take, full-thickness incisional wounds were made in the grafts, and grafts were harvested at various time-points from 4 hours to 28 days after wounding. Integrin receptor protein expression was analyzed at each time-point using immunohistochemistry with monoclonal antibodies specific for the receptors that bind fibronectin, tenascin, collagen, and laminin (alpha5, alpha(v), beta6, alpha2, alpha3, alpha6, and beta4). RESULTS: In this model, wounded human fetal skin grafts reepithelialized rapidly (within 24 to 36 hours) and healed scarlessly. Within 4 hours of wounding, the grafts showed increased, suprabasal expression (alpha2, alpha3, alpha6, beta4) or neoexpression (alpha5, alpha(b), beta6) of integrins at the epidermal wound edge. This increased expression persisted until reepithelialization was complete. CONCLUSIONS: Early upregulation of integrins in fetal wounds may permit rapid keratinocyte migration and reepithelialization, and may be important in limiting the induction of inflammatory mediators and scar.

Animals↗

PubMed1998

Hyaluronan receptor expression increases in fetal excisional skin wounds and correlates with fibroplasia.

BACKGROUND/PURPOSE: The midgestation fetus heals incisional skin wounds scarlessly, whereas large excisional wounds scar. High concentrations of hyaluronan (HA) are associated with scarless fetal as opposed to scar-forming adult wound repair. Because expression of the HA receptors, CD44 and RHAMM (Receptor for HA-Mediated Motility), has been associated with adult wound fibroplasia, the authors postulated that fetal excisional wounds would show increased expression of CD44 and RHAMM as compared with incisional wounds. METHODS: Two models of fetal wound healing were examined. Fetal skin from human abortuses was heterotransplanted subcutaneously into severe combined immunodeficient (SCID) mice. Fourteen days after grafting, incisional or 2-mm excisional wounds were created (n = 6 per time-point). In addition, incisional and excisional (6 to 10 mm) wounds (n = 5 per time-point) were created on the backs of 70- to 75-day fetal lambs (term, 145 days). Tissue from both models was harvested at sequential time-points after injury. Wounds were studied histologically for fibroplasia and assayed for their HA content. CD44 and RHAMM expression were analyzed by immunohistochemistry and immunoblotting. RESULTS: As expected, in both models, incisional wounds healed scarlessly, whereas excisional wounds showed fibroplasia. Incisional wounds of fetal lambs maintained a significantly higher HA content than excisional wounds 3 days after injury. Between 1 and 7 days in either human or sheep fetal wounds, immunostaining for CD44 and RHAMM markedly increased along the margins of excisional wounds as compared with incisional wounds and unwounded skin. Immunoblot analysis confirmed this increased HA receptor expression in both models. CONCLUSIONS: HA receptor expression increased in both human and sheep fetal excisional wounds and correlated with fibroplasia and a reduced HA content. The authors speculate that strategies to limit the expression or function of HA receptors during postnatal wound repair may modify the development of scar.

Animals↗

PubMed1998

Tracheal occlusion reverses the high impedance to flow in the fetal pulmonary circulation and normalizes its physiological response to oxygen at full term.

PURPOSE: The authors hypothesized that in utero tracheal occlusion would reverse the high impedance to pulmonary blood flow associated with congenital diaphragmatic hernia (CDH) and normalize the fetal physiological response to oxygen at term. METHODS: Three experimental groups were studied. Six fetal lambs (CDH group) underwent creation of a left CDH at 80 days' gestation, an additional six fetal lambs underwent left CDH creation at 80 days' gestation followed by fetal tracheal occlusion performed at 108 days' gestation (CDH + TO group), and four control fetal lambs (control group) underwent a sham procedure at 80 days gestation. All lambs were followed up at 2-week intervals by pulse wave Doppler echocardiography. At each time-point the pulsatility index (PI) was calculated for the left branch pulmonary artery from the Doppler blood velocity waveform. Near term (term, 145 days gestation) at 136 days gestation, measurements were repeated under maternal normoxia and hyperoxia. The fetal lungs were harvested and processed for morphometric analysis by radial alveolar counts (RAC) and lung-to-body-weight ratios (LBWR) as measures of lung growth. RESULTS: At 136 days' gestation the PI of the CDH + TO group (2.88 +/- 0.29) and control group (3.97 +/- 0.37) were significantly lower compared with the PI of the CDH group (9.02 +/- 0.50). There was a significant decrease in the PI of both the CDH + TO group and the control group with maternal hyperoxia at term, whereas the CDH group showed no change. The lungs of the CDH group fetuses were significantly smaller by LBWR and RAC than both CDH + TO and control fetuses. CONCLUSIONS: An elevated PI is associated with pulmonary hypoplasia, fetal tracheal occlusion reverses this finding, and results in a normal fetal physiological response to changes in oxygen tension at term.

Analysis of Variance↗

PubMed1997

Fetoscopic gene therapy for congenital lung disease.

Fetal gene therapy offers the promise of cure for certain genetic diseases, like cystic fibrosis and surfactant protein B deficiency. The authors hypothesized that a fetoscopic approach could attain a high level of organ-specific gene transfer to the fetal lung late in gestation. To test this hypothesis the authors examined the efficacy, specificity, and toxicity of recombinant adenovirus-mediated transfer of the beta-galactosidase marker gene to the lung of late gestation fetal sheep using a fetoscopic technique. Twelve fetal sheep of 125 to 135 days' gestation (term, 145 days) underwent fetoscopic bronchoscopy and intratracheal administration of a replication-deficient adenoviral vector that transduces the beta-galactosidase marker gene. Escape of administered virus was prevented by the fetoscopic deployment of a detachable silicone balloon in the fetal trachea. All fetuses survived until being killed at 2 days after vector delivery for the histopathologic assessment of vector efficacy and specificity. Optimal beta-galactosidase transgene expression was observed at a viral titer of 2 x 10(12) particles per milliliter of administered volume. Expression was greatest in the distal pulmonary parenchyma, particularly in type II pneumocytes, and extended out to the pleura. There was no evidence of gene transfer in either the large conducting airways or in any other fetal organ. The authors have developed a minimally invasive technique for the specific pulmonary delivery of gene therapy vectors to the fetus with no associated acute toxicity. Gene transfer to the late gestation fetus for the treatment of congenital pulmonary disease may be feasible through fetoscopy.

Adenoviruses, Human↗

PubMed1997

Myofibroblast persistence in fetal sheep wounds is associated with scar formation.

The scarless repair capabilities of the fetus are influenced by the size of the wound and the gestational age of the fetus. Whereas small wounds heal scarlessly, large wounds in the same fetus heal with scar. Myofibroblasts are specialized fibroblasts that express alpha-smooth muscle actin (alpha-SMA), a contractile cytoskeletal protein. The authors hypothesized that small fetal wounds that heal scarlessly will have a relative absence of myofibroblasts, whereas large wounds that heal with scar will have abundant myofibroblasts. In this study, an incisional wound and four punch biopsy wounds of 2, 4, 6, and 10 mm diameter were placed on the backs of 60- to 90-day-gestation fetal sheep (term, 145 days). Fourteen days after wounding, the healed fetal wounds were harvested, the repair morphology was determined (scarless, transitional repair, or scar), and the expression of alpha-SMA was analyzed by immunohistochemistry. In the second part of this study the authors analyzed the temporal expression of alpha-SMA in fetal wounds at 1, 2, 3, and 7 days after wounding in 70-day-gestation fetal sheep. In the 14-day wounds, the authors found that alpha-SMA was not expressed in any incisional or 2-mm wound that healed scarlessly, but it was expressed in all wounds that healed with scar. Overall, alpha-SMA expression strongly correlated with increasing wound size (P < .005). Myofibroblasts were seen as early as 24 hours after wounding, and at 3 and 7 days all wounds showed strong expression of alpha-SMA. These results demonstrate that although myofibroblasts are induced early in fetal wound repair, by 14 days there is a notable lack of myofibroblasts in wounds that heal scarlessly and an abundance of myofibroblasts in those wounds that scar. By determining the factors that regulate the disappearance of the myofibroblast in scarless fetal wounds, the authors hope to gain new insights into the mechanisms of scarless fetal repair.

Actins↗

PubMed1997

Wound size and gestational age modulate scar formation in fetal wound repair.

The early-gestation fetus heals incisional skin wounds rapidly and scarlessly. The morphology with which the fetus heals excisional skin wounds remains unclear. To characterize excisional fetal wound repair, and to determine whether there is a developmentally regulated wound-size threshold beyond which fetal skin heals with scar, the authors created excisional wounds in fetal lambs of varying gestational age. Time-mated pregnant ewes carrying 22 fetuses at 60 to 90 days' gestation (term, 145 days) underwent laparotomy and hysterotomy. An incisional wound and four circular, punch biopsy wounds of 2, 4, 6, and 10 mm in diameter were placed on the back of each fetal lamb and marked with India ink. The wounds were harvested at 14 days' postwounding and examined grossly and microscopically after serial sectioning and histological staining. Morphological features of all wounds were graded. By 14 days' postwounding all fetal wounds had healed completely. for lambs at each gestational age, increasing wound size was strongly associated with an increase in the frequency of scar. Also, as gestational age increased from 60 to 90 days' gestation the frequency of scarless repair decreased. By understanding the cellular and molecular processes that mediate scar formation with increasing wound size and advancing gestational age, the authors hope to gain further insight into the mechanisms of scarless fetal wound repair.

Animals↗

PubMed1996

Esophageal replacement using the colon: is it a good choice?

Thirty-eight children (2 months to 26 years of age) underwent esophageal replacement at our institution between 1962 and 1993. Twenty-four patients had esophageal atresia, with the replacement performed at a mean age of 17 months. The remaining patients (37%) had strictures and were older (mean, 7.4 years). Replacement procedures involved the right colon in 61% of cases and the transverse left colon in the others (39%). Sixty-three percent were placed substernally and 37% were done in transthoracic fashion. The average length of stay in the hospital was 34 days (range, 11 to 256 days.) Early complications (within 30 days) included cervical anastomotic leaks (11 patients; 29%) pneumonia (4), would infection (2), pneumothorax/hemothorax (3), wound dehiscence (1), prolonged ventilation (2), vocal cord paralysis (1), Horner's syndrome (1), pancreatitis (1), and perforated graft (1). Despite the incidence of early leaks, only two persisted long-term (more than 3 months). Other late complications included significant proximal strictures (5), and cologastric strictures developed in five patients. Seven cases were considered graft failures (18%), and all of these eventually require graft replacement. Additional problems included redundant graft requiring revision (4) and dumping syndrome (2). There were six cases of intestinal obstruction caused by adhesions. Four of these involved intrathoracic obstruction of the graft and two involved small bowel obstruction. There was only one death, which occurred late and was not related to the primary disease or procedure. Long-term follow-up data were available for 20 patients (53%). The follow-up period ranged from 1 to 33 years (mean, 12 years). Fourteen had excellent results after the initial interposition, being able to eat and function well without any further intervention. Seven patients (18%) have had poor results and 17 (45%) required additional procedures to obtain good functional results. In our experience, the colon continues to be a good option for esophageal replacement, but additional procedures frequently are necessary to optimize the functional outcome. Good results can be expected in the majority of cases, but late problems (ie, redundant colon and poor emptying) are not unusual, and careful follow-up is essential in the management of such patients.

Adolescent↗

PubMed1994

Combined laparoscopic-endoscopic gastrostomy.

Since the first report of successful percutaneous endoscopic gastrostomy placement by Gauderer and Ponsky in 1981 [Surg. Gynecol. Obstet. 152: 83-85], many modifications of the original technique have been published. Each reports easier and safer placement of the gastrostomy tube, but all have the same inherent flaw: Access to the gastric lumen is accomplished by a blind needle puncture of the anterior abdominal wall. A new technique, utilizing a newly available microendoscope (Origin Medsystems), is described. Using the microendoscope, direct visualization of the stomach and left upper quadrant of the abdomen allows safer access to the gastric lumen for subsequent tube placement without the need for additional incisions or punctures. The procedure can still be performed with local infiltrative anesthesia and systemic intravenous sedation.

Abdomen↗

PubMedDate not supplied

Adenoviral-mediated gene transfer in wound healing: acute inflammatory response in human skin in the SCID mouse model.

The use of an adenoviral vector as a means of therapeutic protein delivery for the treatment of impaired wound healing is a potentially effective application of current gene transfer techniques. This study was designed to investigate the ability of adenovirus to mediate gene transfer in healing wounds in human skin in vivo. The human skin/severe combined immunodeficient mouse chimera model was used to study both the response of human tissue to adenoviral infection and the nature of the acute inflammatory response. The effects of adenoviral infection and transgene expression on the rate and quality of human wound healing were then investigated. Cell- and species-specific monoclonal antibodies were used to characterize the resident skin cell types participating in wound repair, the inflammatory response, and the proliferative potential of adenovirus-treated compared to control skin. Our studies show that, following wounding, normal skin architecture is restored in the presence of adenoviral infection equivalent to noninfected controls. Despite an increased acute inflammatory response after adenovirus injection, no difference in the healing capabilities of wounded skin was observed, suggesting that adenovirus-mediated gene transfer for growth factor-mediated acceleration of wound healing may be feasible.

Adenoviridae Infections↗