The clinical use of fetal neural grafts as an intracerebral source of dopamine for patients with Parkinson's disease has met with limited success. Since basic fibroblast growth factor (bFGF) enhances the survival and growth of dopaminergic neurons in vitro, we explored whether cells genetically modified to produce bFGF would improve the functional efficacy of dopaminergic neurons implanted into rats with experimental Parkinson's disease. Results show that bFGF-producing cells grafted together with fetal dopamine neurons have potent growth-promoting effects on the implanted neurons in vivo. Moreover, rats implanted with such co-grafts display the most pronounced behavioural improvements post-grafting. These findings not only provide insight into the function of bFGF in situ, but also suggest an approach for enhancing the survival and function of dopamine neurons grafted into the damaged brain.

Insulin is important for optimal fetal and neonatal growth and development. Its continued availability is due, in part, to ongoing islet cell growth within the pancreas. IGFs and IGF-binding proteins (IGFBPs) have been implicated as paracrine regulators of islet cell growth within the developing pancreas. The purpose of this study was to determine whether the intact rat pancreas expresses mRNAs for IGF-I, IGF-II and IGFBPs, and how these might change with development. Liver was studied as a control tissue. Pancreas and liver were taken from fetal rats at 20-22 days of gestation, from postnatal rats at 1-21 days and from adult animals, and mRNAs for IGFs-I and -II and IGFBPs-1 to -6 were detected by Northern blot hybridization. The amount of IGF-II mRNA was greatest in the liver and pancreas of the fetal rat, and declined in both tissues during the neonatal period. Conversely, IGF-I mRNA levels were low but detectable in fetal life, and rose to adult levels within 2 weeks of birth. Both IGFBP-1 and IGFBP-2 mRNAs were present in fetal rat liver, increasing in amount over the first week of life, and declining in the adult. However, within the pancreas, IGFBP-1 mRNA was undetectable and IGFBP-2 mRNA was very low in the fetus and neonate. Both IGFBP-1 and IGFBP-2 mRNAs transiently appeared in the pancreas between postnatal weeks 2 and 3 and declined in the adult. IGFBP-3 and IGFBP-4 mRNAs were detected in both the liver and pancreas throughout the developmental period studied. IGFBP-3 mRNA increased in amount immediately following birth, while the quantity of IGFBP-4 mRNA increased sharply in liver from postnatal day 21, but declined in the pancreas. mRNA for IGFBP-5 or -6 was undetectable in either tissue. The reslts show that both IGF-I and IGF-II are expressed by rat pancreas from at least 20 days of gestation, the latter being predominant in fetal life and the former during postnatal development. In addition, at least four IGFBP mRNAs (IGFBPs-1, -2, -3 and -4) were expressed within the pancreas with distinct developmental patterns. IGFBP-3 and -4 were predominant in the fetal and neonatal periods, while increased expression of IGFBPs-1 and -2 occurred 2-3 weeks after birth. The ontogeny of IGFBP mRNA expression in pancreas differed from that in liver.(ABSTRACT TRUNCATED AT 400 WORDS)

Insulin is a major regulatory hormone for optimal tissue growth and function in utero. Its continued availability to the growing fetus depends on increasing islet cell mass. The purpose of the study was to examine the interactions between nutrient availability and insulin-like growth factor (IGF) release and action during DNA synthesis by isolated fetal rat islets of Langerhans. Specifically, we wished to determine (a) whether the availability of glucose or total amino acids altered the release of endogenous IGF-I or -II, (b) if both IGF-I and -II were effective mitogens for pancreatic beta-cells, (c) whether islets released IGF-binding proteins (IGFBPs) and their possible regulation by nutrient availability and (d) how IGFBPs might regulate the ability of IGFs to alter islet DNA synthesis. Islets of Langerhans were isolated from fetal rat pancreata on day 22 of gestation by collagenase digestion. Islets enriched in beta-cells following a 5-day preincubation regime were maintained in various concentrations of glucose (1.4-16.7 mmol/l) or amino acids (x1- x3 total concentrations), with or without exogenous IGF-I, -II, IGFBP-1 or IGFBP-2. The release of insulin and endogenous IGF-I and -II were each determined by radioimmunoassay, and IGFBP release characterized by Western ligand blot analysis. DNA synthesis was measured by the incorporation of [3H]thymidine. Isolated islets demonstrated an increased release of insulin in response to increasing amounts of both glucose and amino acids, demonstrating functional viability. Both classes of nutrients also increased the DNA synthetic rate of islets. Islets released almost twice as much IGF-II (0.22 +/- 0.08 nmol/l, mean +/- S.E.M., n = 4) as IGF-I (0.14 +/- 0.03 nmol/l) in cultures containing 8.7 mmol glucose/l and x1 amino acids. Lesser or greater concentrations of glucose did not alter the release of either IGF, but the release of IGF-II was significantly increased (0.53 +/- 0.08 nmol/l, P < 0.01) in the presence of x2 amino acids. Exogenous IGF-I was fivefold more active in stimulating DNA synthesis by islets (half maximal concentration (ED50) 1.6 +/- 0.4 nmol/l, n = 3) than was IGF-II (ED50 8.1 +/- 0.6 nmol/l), regardless of glucose concentration. Isolated islets released four species of IGFBP with molecular sizes of approximately 19, 25, 35 and 46 kDa respectively. The 35 kDa form was identified by Western immunoblot as IGFBP-2. Increasing the glucose concentration between 1.4 mmol/l and 16.7 mmol/l caused a dose-related increase in the release of the 19, 25 and 35 kDa IGFBP species.(ABSTRACT TRUNCATED AT 400 WORDS)

To determine the role of insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) in the development of the pancreas, and specifically of the islets of Langerhans, we have examined the cellular distribution and developmental changes in the expression of IGFs and IGFBPs in the pancreas of the fetal and neonatal rat between 19·5 days of gestation and postnatal day 28. This represents a period of substantial growth and restructuring of the cell component in islets of this species. IGF-I, IGF-II, and IGFBPs-1 to -6 mRNAs were localized by in situ hybridization, and peptides by immunohistochemistry, in histological sections. IGF-II mRNA was highly expressed in islet cells and some ductal epithelial cells in late fetal and early neonatal life, but was barely detectable by postnatal day 28. IGF-II peptide showed a similar distribution. IGF-I mRNA was barely detected in the fetus or neonate and was localized predominantly in the ductal and acinar tissues after postnatal day 7. IGF-I immunoreactivity was associated with some islet cells in the fetus and neonate, suggesting an endocrine rather than a paracrine source.We performed co-localization studies to assess whether the distribution of IGFs within the pancreas might be due to a sequestration by locally produced IGFBPs. The presence of mRNAs for both IGFBPs-1 and -2 was minimal in the pancreas prior to postnatal day 7, although subsequently IGFBP-1 mRNA was seen in islet cells, while IGFBP-2 mRNA was localized in both islets and acinar tissues. In contrast, both IGFBPs-1 and -2 immunoreactivities were identified in islets from late fetal life, suggesting a circulatory source for these IGFBPs during early pancreatic development. IGFBPs-3 to -5 mRNAs and immunoreactivities were identified within islet cells throughout fetal and neonatal life, with IGFBPs-3 and -5 being mainly associated with the cell-rich islet mantle. The results show a compartmentalization of IGFs within pancreatic tissue, reflecting both paracrine and endocrine sources. The localization and action of IGFs in pancreas likely involves sequestration and distribution by endogenous as well as circulating IGFBPs.