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Alan W Flake

Publications and source records attributed to Alan W Flake.

72 records · Page 4Linked to original sources
PubMed2002

In utero meconium exposure increases spinal cord necrosis in a rat model of myelomeningocele.

BACKGROUND/PURPOSE: The rationale for in utero repair of myelomeningocele has been supported experimentally by the observation of preserved neural function after prenatal closure of surgically created defects compared with nonrepaired controls. The mechanism of injury to the exposed neural elements is unknown. Postulated mechanisms include trauma to the herniated neural elements or progressive injury from amniotic fluid exposure as gestation proceeds. A component of amniotic fluid that may contribute to neural injury is meconium. In the current study the effect of human meconium on the exposed spinal cord in a fetal rat model of myelomeningocele was examined. METHODS: Twenty time-dated pregnant rats underwent laparotomy at 181/2 days of gestation. The exposed uterus was bathed in ritrodrine for tocolysis. The amniotic cavity was opened over the dorsal midline of the fetal rat, and, under a dissecting microscope (x25), a 2- to 3-level laminectomy was performed. Under magnification (x40), the translucent dura was opened using a 25-gauge needle as a knife. Two fetuses per dam were operated on. In the control group, the amniotic fluid was restored with saline solution, whereas in the experimental group a solution of Human meconium diluted (10%) in saline was used to restore the amniotic fluid. Fetuses were harvested by cesarean section at 211/2 days' gestational age. The liveborn pups were then killed and fixed in 10% formaline. Sections 10 micrometer thick were stained with H&E and studied by light microscopy for evidence of spinal cord injury. RESULTS: Seven of 20 (35%) experimental rat pups and 6 of 20 (30%) control rat pups were liveborn. All liveborn pups had severe paralysis of the hindlimbs and tail, so that functional differences between the 2 groups could not be detected. Histologic examination of 13 spinal cords at the site of surgical exposure showed that necrosis of neural tissue in 5 of 7 meconium-exposed rat pups was increased when compared with that observed in the 6 fetuses exposed to amniotic fluid without meconium. In general, inflammation was greater and repair processes appeared delayed in meconium-exposed rat pups. CONCLUSIONS: Exposure of the spinal cord of fetal rats to amniotic fluid by surgically created myelomeningocele leads to severe functional impairment. Histologically recognizable necrosis of neural elements was increased in those animals that were exposed to diluted human meconium in the amniotic fluid. The results support the hypothesis that meconium may contribute to the pathophysiology of spinal cord injury observed in myelomeningocele.

Amniotic Fluid↗
PubMed2002

Engraftment of bone marrow and fetal liver cells after in utero transplantation in MDX mice.

BACKGROUND/PURPOSE: In utero hematopoietic stem cell transplantation (IUHSCTx) has been experimentally or clinically effective only in circumstances in which there is a survival advantage for donor cells. A survival advantage exists for normal muscle cells in muscular dystrophy. Because hematopoietic and mesenchymal stem cells may have the capacity to differentiate into muscle cells, the authors hypothesized that in utero bone marrow (BM) or fetal liver (FL) stem cell transplantation may be used to treat muscular dystrophy. METHODS: Time-dated 14-day-gestation fetal muscular dystrophy mice (mdx) were injected intraperitoneally with 1 to 5 x 10(6) BM or FL cells per fetus from Rosa26 donor mice (transgenic for lacZ). Four weeks after birth, peripheral blood from the pups was analyzed for hematopoietic chimerism by using fluorescence-activated cell sorting (FACS) for the Ly-9.1 marker. Chimeric mice (6 BM and 2 FL recipients) were sacrificed at 12 to 14 months of age, muscles were stained with X-gal, and analyzed by 1- to 2-microm plastic sections. Polymerase chain reaction (PCR) for lacZ was performed in other organs to determine systemic engraftment. RESULTS: At the time of death, all animals that were chimeric at 4 weeks continued to show hematopoietic chimerism of 0.2% to 9% by FACS. Engrafted donor cells were found in multiple sections from hindlimb skeletal muscles, diaphragms, and hearts from both BM and FL recipients. These cells had incorporated into the host muscles, and their morphology was consistent with myogenic differentiation. PCR of BM, liver, spleen, thymus, kidney, and lung for lacZ was positive in multiple animals. CONCLUSIONS: IUHSCTx leads to widespread engraftment of donor cells in multiple muscle compartments of hematopoietic chimeras. The advantage for normal myocytes offered in the mdx model allows engraftment and myogenic differentiation of transplanted BM or FL cells by morphology at a relatively higher frequency in muscle relative to other tissues, without the need for host conditioning. Because muscular dystrophy now can be detected early in gestation, such a strategy may offer a future alternative in the clinical treatment of this disease.

Animals↗
PubMed2002

Influence of congenital heart disease on survival in children with congenital diaphragmatic hernia.

OBJECTIVE: We sought to assess outcome in patients with CDH and HD to determine if LHR is also predictive of outcome in this subset of patients. STUDY DESIGN: We carried out a retrospective review (April 1996-October 2000) of patients with isolated CDH (n = 143, 82.2%) and patients with HD (n = 31, 17.8%) to determine the incidence of additional anomalies, survival to term, CDH repair, cardiac repair, and survival to discharge. Survival based on LHR was analyzed in a subset of fetuses. RESULTS: The risk of death from birth to last follow-up was 2.9 times higher for patients with CDH plus HD than for patients with CDH alone (P <.0001). Of 11 patients with CDH plus HD who had CDH repair (5 of whom also had HD repair), 5 survived. All 10 patients with an LHR <1.2 died; 3 of 6 with an LHR >1.2 survived (Fisher exact test, P =.04). CONCLUSION: Heart disease remains a significant risk factor for death in infants with CDH. The LHR helps predict survival in this high-risk group of patients.

Abnormalities, Multiple↗
PubMed2002

Bone marrow tissue engineering.

The creation of mixed hematopoietic chimerism has become an important clinical strategy for tolerance induction for cellular and organ transplantation, and for the treatment of numerous hematopoietic diseases. Clinical success has been limited however, by host immune response and by competition from host hematopoiesis. Recent data suggests that limited donor stem cell engraftment after minimally myeloablative hematopoietic stem cell (HSC) transplantation may in part be due to MHC associated microenvironmental mismatch resulting in a competitive disadvantage for donor HSC. A strategy to overcome this barrier to stable mixed hematopoietic chimerism would involve concurrent transplantation of a donor bone marrow microenvironment. To test this possibility, we set out to develop a method to tissue engineer a bone marrow microenvironment. One to two murine femurs were mechanically crushed to a fine suspension and were combined in vitro with various delivery vehicles. These constructs were transplanted into syngeneic animals in locations that are known to support transplantation of other tissues. Although bone formation was observed with several conditions, bone marrow formation was noted only within the small bowel mesentery when type I collagen was used as the delivery vehicle. No bone marrow formed when the vehicle was changed to polyglycolic acid or type IV collagen. We have demonstrated that the small bowel mesentery can support bone marrow formation under specific in vivo conditions. Future work will focus on strategies for transplantation of an engineered donor bone marrow environment to facilitate creation of allogeneic mixed hematopoietic chimerism.

Animals↗
PubMed2002

The ex-utero intrapartum treatment.

Advances in prenatal diagnosis, combined with a better understanding of the natural history of prenatally diagnosed anomalies, are providing increasing opportunities to consider fetal intervention in selected cases of life-threatening malformations. Accurate prenatal diagnosis can now accurately identify fetal pathophysiology that poses an immediate threat to the life of the newborn infant on separation from the placental circulation. In this circumstance, the ex-utero intrapartum treatment (EXIT) procedure, which maintains intrapartum uteroplacental support, can be life saving. The most common indications for the EXIT procedure are fetal lesions causing extrinsic or intrinsic airway obstruction. However, fetuses with other anomalies that may compromise neonatal resuscitation can also benefit from this approach. The EXIT procedure differs significantly from a cesarean delivery, and caution must be taken to avoid maternal morbidity. As with all endeavors involving maternal-fetal intervention, a team approach is crucial to ensure accurate diagnosis and optimal perinatal management.

Female↗
PubMed2002

Human mesenchymal stem cells: insights from a surrogate in vivo assay system.

Mesenchymal stem cells (MSC) are multipotent cells that have been isolated from the bone marrow of multiple species that can be induced to differentiate into at least bone, cartilage, and adipose tissue in vitro. Using a model of in utero cellular transplantation in which human MSC are transplanted into fetal lambs, we have shown that MSC can engraft in multiple tissues and persist for over one year. Furthermore, these cells can differentiate into cardiac and skeletal myocytes, bone marrow stromal cells, adipocytes, thymic epithelial cells, and chondrocytes. These observations lend support to the potential utility of MSC for cellular and/or gene therapy in the treatment of a variety of congenital or acquired diseases such as osteogenesis imperfecta, muscular dystrophy, lysosomal storage diseases, and for enhancement of bone marrow transplantation.

Animals↗
PubMedDate not supplied

The conceptual application of systems theory to stem cell biology: a matter of context.

Much of our current understanding of stem cell biology is derived from reductionist observations made out of context from the functional stem cell compartment. The extrapolation of observations of cellular behavior from highly contrived experimental circumstances to intact biological systems represents an unsupportable assumption on which we currently rely. The conceptual application of systems theory to stem cell biology requires a shift in our view of experimental stem cell science toward the reality of cellular function within a complex biological system. Although the complexity of the system is beyond current mathematical modeling, the conceptual framework of systems theory can provide context to multiple controversies in stem cell biology.

Animals↗
PubMedDate not supplied

Fetal liver as a source of autologous progenitor cells for perinatal tissue engineering.

Mesenchymal progenitor cells, isolated from adult bone marrow, have been shown to have utility for autologous tissue engineering. The possibility of isolating from the fetal hematopoietic system a cell population with similar potential, which could be used for autologous reconstruction of prenatally diagnosed congenital anomalies, has not been explored to date. Liver stromal cells isolated from a portion of the right lateral hepatic lobe of midgestation fetal lambs were expanded in vitro. Passage 1 cells displayed a uniform fibroblast-like morphology but could be induced to differentiate into skeletal muscle, adipocytes, chondrocytes, and endothelial cells by selective medium supplementation. By manipulating the extracellular matrix in vitro, spontaneously contracting cardiac myocyte-like cells could be generated as well. Multilineage differentiation was confirmed by morphology, protein expression, and upregulation of lineage-specific mRNA. The potential for engineering myocardial tissue was then investigated by transplanting early-passage progenitor cells, organized on a three-dimensional matrix, into the ventricle of an immunocompromised rat utilizing a previously described model of left ventricular tissue engineering. Survival, incorporation into the host myocardium, and cardiomyocytic differentiation of the transplanted cells were confirmed. We have demonstrated that mesenchymal progenitor cells with multilineage potential can be isolated from the fetal liver and have potential utility for autologous tissue engineering.

Adipocytes↗
PubMedDate not supplied

History of fetal diagnosis and therapy: Children's Hospital of Philadelphia experience.

Since its inception in 1995, the mission of the Center for Fetal Diagnosis and Treatment at the Children's Hospital of Philadelphia (CHOP) has been to provide comprehensive, multidisciplinary expertise in all facets of prenatal diagnosis, reproductive genetics, and prenatal, perinatal, and postnatal treatment for abnormal fetuses. Most of the authors were trained and/or served on faculty at centers in San Francisco (N.S.A., A.W.F., T.M.C., L.J.H.) or Detroit (A.W.F, M.P.J.). Accurate prenatal detection by serial sonographic study and the development of ultrafast magnetic resonance imaging (MRI) scanners has permitted delineation of the natural history of anatomic malformations. Definition of the pathophysiological features that affect clinical outcome and formulation of management based on prognosis has allowed families to make informed decisions. Outcomes have been improved through carefully planned and coordinated perinatal management. In some cases of life-threatening or severely debilitating defects, prenatal surgery has been offered.

Female↗
PubMedDate not supplied

Chorioamniotic membrane separation following open fetal surgery: pregnancy outcome.

OBJECTIVE: To review the incidence of posthysterotomy chorioamniotic membrane separation and delivery outcome following open fetal surgery [myelomeningocele (MMC); cystic adenomatoid malformation (CCAM); congenital diaphragmatic hernia (CDH); sacrococcygeal teratoma (SCT)]. STUDY DESIGN: Retrospective review of a maternal population undergoing open fetal surgery at a single tertiary level program (1998-2001) following the initiation of close postoperative ultrasound follow-up for membrane separation. Onset of membrane separation was coded as not present (NP), immediate (<2 weeks) or delayed (>2 weeks) from day of surgery. RESULTS: Fifty-three charts were reviewed: MMC 43, CCAM 7, CDH 1, and SCT 2. In the MMC group there were 26 NP, 8 immediate, and 9 delayed. Preterm labor occurred in 4 patients with only 2 having had membrane separation. Risk of membrane separation is increased for surgery done at less than 23 weeks gestation (p < 0.005). Delay from MMC surgery to delivery was 11.0, 9.8, 12.0 weeks for NP, immediate, and delay, respectively. In the MMC group, there were 3 neonatal deaths (NND) at 9, 9, and 21 days post surgery (PROM/PTL; chorioamnionitis, PROM/PTL, respectively). No membrane separation was present in the CCAM, CDH, and SCT cases. CONCLUSIONS: (1) Membrane separation was significantly more likely to occur if surgery was performed prior to 23 weeks. (2) Membrane separation post hysterotomy (17/50 = 34%) may be associated with an increased risk of PROM but not delivery before 30 weeks gestation. (3) Delivery prior to 33 weeks gestation for MMC groups was 12/43 (28%) with 3 NND (7%). (4) Elective delivery at 36-37 weeks gestation was possible for 43% of the fetal surgery population.

Amnion↗
PubMedDate not supplied

Epinephrine inhibits tracheal occlusion induced lung growth in fetal sheep.

OBJECTIVE: Although the mechanisms responsible for lung growth following tracheal occlusion (TO) are not fully understood, lung fluid accumulation is a requirement for growth to occur. It is known that betamimetics such as epinephrine (Epi), terbutaline, and ritodrine inhibit fetal lung fluid production late in gestation. We hypothesized that continuous infusion of Epi would have a detrimental effect on lung growth following TO in the fetal sheep model. METHODS: Twenty fetal lambs were divided into four groups. Group 1: no TO without Epi (n = 4); group 2: TO without Epi (n = 4); group 3: no TO with Epi (n = 5), and group 4: TO with Epi (n = 7). TO was performed on days 130-134 of gestation (full term = 145 days). In groups 3 and 4, Epi was infused into the fetus at a rate of 2 microg/min using a miniosmotic pump implanted subcutaneously at the time of TO. The fetuses were sacrificed after 4 days, and lung volume (LV, ml/kg), drained lung fluid (LF, ml/kg), wet lung weight/body weight ratio (LW/BW, %), whole right-lung dry weight per body weight ratio (dRLW/BW, g/kg), volume density of lung parenchyma (v(Vp)), and right-lung DNA and protein contents were compared among the four groups by one-way Anova. RESULTS: LW/BW and dRLW/BW of group 4 (3.91 +/- 0.52 and 2.10 +/- 0.28, mean +/- SD) were significantly lower than those of group 2 (5.18 +/- 0.57 and 2.67 +/- 0.15) and were not statistically significantly different from those of group 1 or 3. LV, LF, V(Vp), and DNA and protein contents all showed a similar trend. CONCLUSIONS: Continuous infusion of Epi to the fetus results in less fluid accumulation within the TO lungs and abolishes significant lung growth after TO in the late-gestation fetal lamb. Drugs affecting lung fluid secretion may have a major impact on TO-induced lung growth.

Animals↗
PubMedDate not supplied

Abnormal umbilical cord Dopplers may predict impending demise in fetuses with sacrococcygeal teratoma. A report of 2 cases.

OBJECTIVE: To identify factors predictive of fetal demise in fetuses with sacrococcygeal teratoma (SCT). METHOD: The recent management of monochorionic twins discordant for a large SCT and a singleton with a large SCT were reviewed. RESULTS: Serial fetal echocardiography and ultrasonography with Doppler flow measurements documented rapid growth of the SCT in both cases with a relatively modest increase in combined cardiac output. No placentomegaly or hydrops was observed at any time. In both fetuses with SCT, evolution of abnormal umbilical artery waveforms was observed with the ultimate development of reversed end-diastolic umbilical arterial flow that was followed by sudden fetal demise. CONCLUSION: Death in these 2 fetuses with large SCTs in the absence of placentomegaly/hydrops or hemodynamic changes suggestive of evolving high-output failure suggests a previously unrecognized mechanism of death in fetuses with large rapidly growing SCTs. In these cases, fetal demise may only be heralded by abnormal umbilical artery waveforms that progress to the premorbid observation of reversed diastolic umbilical artery blood flow. Umbilical artery waveform analysis should be closely monitored with other hemodynamic parameters in fetuses with large SCTs. In such fetuses, depending on the gestational age, abnormalities in umbilical artery waveform should be considered indications for early delivery or in utero intervention to prevent fetal demise.

Adult↗
PubMedDate not supplied

In utero hematopoietic cell transplantation: what are the important questions?

The treatment of congenital hematologic disorders before birth by in utero hematopoietic stem cell transplantation remains a challenging goal. Although success has been achieved in X-linked severe combined immunodeficiency, the approach has failed in all other disorders attempted thus far. In this review, we examine relevant experimental data from the perspective of an analysis of why failure has occurred. We will also attempt to pose the important questions that will need to be answered prior to further clinical attempts to treat most target disorders by this approach.

Female↗
PubMedDate not supplied

Abnormal umbilical cord Doppler sonograms may predict impending demise in fetuses with sacrococcygeal teratoma. A report of two cases.

OBJECTIVE: To identify factors predictive of fetal demise in fetuses with sacrococcygeal teratoma (SCT). METHOD: The recent management of monochorionic twins discordant for a large SCT and a singleton with a large SCT was reviewed. RESULTS: Serial fetal echocardiography and ultrasonography with Doppler flow measurements documented rapid growth of the SCT in both cases with a relatively modest increase in combined cardiac output. No placentomegaly or hydrops was observed at any time. In both fetuses with SCT, evolution of abnormal umbilical artery waveforms was observed with the ultimate development of reversed end-diastolic umbilical arterial flow that was followed by sudden fetal demise. CONCLUSION: Death in these 2 fetuses with large SCTs in the absence of placentomegaly/hydrops or hemodynamic changes suggestive of evolving high-output failure suggests a previously unrecognized mechanism of death in fetuses with large rapidly growing SCTs. In these cases, fetal demise may only be heralded by abnormal umbilical artery waveforms that progress to the premorbid observation of reversed diastolic umbilical artery blood flow. Umbilical artery waveform analysis should be closely monitored with other hemodynamic parameters in fetuses with large SCTs. In such fetuses, depending on the gestational age, abnormalities in umbilical artery waveform should be considered indications for early delivery or in utero intervention to prevent fetal demise.

Adult↗
PubMedDate not supplied

Thoracoamniotic shunts: fetal treatment of pleural effusions and congenital cystic adenomatoid malformations.

OBJECTIVE: To determine whether fetuses that underwent thoracoamniotic shunt placement for treatment of pleural effusion (PE) or macrocystic congenital cystic adenomatoid malformation (CCAM) have an improved outcome as compared with an untreated population. METHODS: A retrospective review from a single tertiary center was performed using thoracoamniotic shunt placement to treat PE or macrocystic CCAM between 1998 and 2001. Thoracoamniotic shunts were used on 26 occasions in 19 pregnancies. RESULTS: The average gestational age at the diagnosis of PE and CCAM was 22 + 4 and 20 + 0 weeks, respectively. Shunts were offered in pregnancies complicated by hydrops or at significant risk for pulmonary hypoplasia. Shunts were placed at 26 + 2 weeks (average) and 23 + 1 weeks (average) in the PE and CCAM groups, respectively. In CCAM patients, the mean pre- and postshunting mass volumes were 50.5 and 25.7 cm(3), representing a 51% reduction in mass volume following shunt placement. In the PE group, the average delivery age was 33 + 5 weeks, with an average shunt placement to delivery time of 7 + 3 weeks. In the CCAM group, the average delivery was 33 + 3 weeks, with an average shunt placement to delivery time of 10 + 2 weeks. The postnatal survival rates were 67% (6/9) and 70% (7/10) in the PE and CCAM groups, respectively. CONCLUSIONS: (1) Thoracoamniotic shunts should be considered as a treatment option for selected PE or macrocystic CCAM fetuses with hydrops or a significant risk for pulmonary hypoplasia; (2) the neonatal survival with shunting was similar for PE and CCAM groups and was improved as compared with literature reports, and (3) fetuses with CCAM presented earlier with hydrops than those with PE. Successful shunting resulted in a prolongation of pregnancy into the 3rd trimester in both groups.

Adult↗
PubMedDate not supplied

Prenatal diagnosis and management of mainstem bronchial atresia.

The prenatal diagnosis, natural history and management of mainstem bronchial atresia have not been described previously. We report two cases of prenatally diagnosed proximal bronchial atresia. The first patient presented at 18 weeks with sonographic and MRI findings consistent with bronchial atresia with fetal hydrops. The mother developed the mirror syndrome and labor was induced. A non-viable fetus was delivered at 25 weeks. The second patient presented at 16 weeks gestation with evidence of an intrathoracic mass that was subsequently prenatally diagnosed as a right mainstem bronchial atresia. The right lung increased rapidly in size and was associated with the onset of fetal hydrops. At 24 weeks, fetal pneumonectomy was performed but the fetus expired intraoperatively due to cardiovascular collapse. Post-mortem findings in both cases confirmed the presence of an atretic mainstem bronchus with massive enlargement of the lung. Bronchial atresia involving the mainstem bronchus is associated with a poor prognosis.

Bronchi↗
PubMedDate not supplied

Impact of continuous intraoperative monitoring on outcomes in open fetal surgery.

OBJECTIVES: There are shifts in fetal hemodynamics during open fetal surgery that were not appreciated until the use of intraoperative fetal echocardiography. We have developed an intraoperative monitoring strategy to continuously assess fetal hemodynamics. We hypothesized that this approach would enhance intraoperative management and survival. METHODS: Medical records of open fetal surgery patients were reviewed since the implementation of this approach. Intraoperative fetal monitoring was accomplished by continuous echocardiography, pulse oximetry, establishment of intravenous access, and arterial blood gas and hemoglobin measurement. Overall survival was compared to fetal surgeries performed prior implementation of this monitoring strategy. RESULTS: Resections of a congenital cystic adenomatoid malformation or a sacrococcygeal teratoma in nine hydropic fetuses were performed while using this monitoring strategy. Intraoperative echocardiography resulted in a change of management in 7 of 9 fetuses. The main observations on fetal echocardiography resulting in intraoperative intervention were decreased ventricular filling, bradycardia, and decreased ventricular contractility. Therapy included administration of volume expanders and/or inotropic agents. Overall fetal survival was 78% compared to a survival of 42% prior to the implementation of this approach. CONCLUSION: Continuous intraoperative fetal monitoring provides real time assessment of fetal hemodynamics which results in changes in intraoperative management. The overall outcomes in these critically ill fetuses have been improved.

Echocardiography↗