Brain‐derived neurotrophic factor‐transduced fibroblasts: Production of BDNF and effects of grafting to the adult rat brain

Abstract

Local delivery of brain-derived neurotrophic factor (BDNF) by genetically modified cells provides the unique opportunity to examine the effects of BDNF on adult dopaminergic and cholinergic neurons in vivo. Primary rat fibroblasts were genetically engineered to produce BDNF. Conditioned media from BDNF-transduced fibroblasts supported embryonic chick dorsal root ganglion neurons as well as rat fetal mesencephalic neurons. BDNF-transduced fibroblasts grafted to the rat brain survived and showed continued mRNA production for at least 2 weeks. The effects of BDNFtransduced fibroblast grafts on the dopaminergic and cholinergic systems were then assessed. BDNFtransduced fibroblasts grafted into the normal intact substantia nigra induced sprouting of tyrosine hydroxylase-and neurofilament-immunoreactive fibers into the graft. Fibroblast grafts implanted into the normal intact striatum and midbrain as well as the 6-hydroxydopamine-lesioned brain did not induce sprouting of dopaminergic fibers; neither did they affect drug-induced rotational behavior. BDNF-transduced fibroblasts did, however, significantly increase the homovanillic acid/dopamine ratio when grafted into the normal midbrain. Following transection of the fimbria-fornix, BDNFtransduced fibroblasts grafted into the septum were unable to rescue the septal cholinergic population, as did nerve growth factor-producing fibroblast grafts. Genetically modified fibroblast grafts may provide an effective, localized method of BDNF delivery in vivo to test biological effects of this factor on the central nervous system. Indexing termscholinergic; dopaminergic; neurotrophic factor; NGF; transplantation Neurotrophic factors are present in the central nervous system (CNS) and play important roles in neural development, differentiation, and survival (for reviews, see Barde, 1989; Thoenen, 1991). A family of related neurotrophic molecules, called neurotrophins, whose members affect overlapping as well as distinct populations of neurons, has been recently isolated. Members of the neurotrophin family include nerve growth factor (NGF), brain-derived NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript neurotrophic factor (BDNF), neurotrophic factor-3 (NT-3), and neurotrophic factors-4/-5 (NT-4/5). Extensive conservation between species and sequence similarity between members (over 50% homology in amino acid identity) suggest important roles for neurotrophins in the CNS (Leibrock et al., 1989;Maisonpierre et al., 1990;Berkemeier et al., 1991).Neurotrophins exert their effects through specific binding to cell surface receptors that exist in both low (Kd ~ 10 −9 )-and high (Kd ~ 10 −11 )-affinity forms (Meakin and Shooter, 1991). The low-affinity NGF receptor (p75 NGFR ) comprises a 75 kD protein (Chao et al., 1986) and binds all known members in the neurotrophin family. Specificity in binding is afforded by high-affinity binding sites on trk protooncogenes: trkA., trkB, and trkC. Neurotrophic factors appear to mediate their effects by inducing phos...

Beyond oncology — Application of HPMA copolymers in non-cancerous diseases☆

“…However, in many cases the rescue from cell death was only transitory because of the short half-life of these factors [142]. An alternative strategy is to chronically deliver these genetically produced growth factors via cell grafts such as fibroblasts to promote neuron survival and axonal growth [143]. Loh et al developed a novel RGD containing HPMA hydrogels combined with genetically engineered fibroblasts (to chronically produce BDNF or CNTF) for in vivo promoting axon regrowth across tissue defects in the injured CNS [144].…”

Neurotrophins and their role in the cochlea

“…They did not find any indication that the exogenous BDNF caused any side effects, apart from a slight and transient loss of body weight. Lucidi-Phillipi et al (1995) repeated both the septo-hippocampal lesion study (discussed in the previous paragraph) and the SN study in rats, but instead of infusing the BDNF with a cannula they used BDNF-producing grafts consisting of transduced rat fibroblast cells (see Schinstine et al, 1991, for a review on this technique). Not surprisingly, their SN findings were consistent with those of Altar et al (1992).…”

Exploiting Nonneural Cells to Rebuild the Nervous System: From Bone Marrow to Brain

“…According to recent studies, it appears that a number of trophic factors play an important role in maintaining native and grafted dopaminergic neurons (18,19). Fibroblasts and astrocytes engineered to produce these factors have been co-grafted along with the dopaminergic neurons or alone (19). Reportedly, the grafted dopaminergic neurons survive longer and native cells become more robust, with extensive arborization of their processes (20).…”

“…In a series of studies by different groups of investigators, fibroblasts were engineered to elaborate tyrosine hydroxylase (13,16,17) and, after implantation, were noted to reverse the apomorphine-induced rotatory behavior in the rodent model of Parkinson's disease (15,16). According to recent studies, it appears that a number of trophic factors play an important role in maintaining native and grafted dopaminergic neurons (18,19). Fibroblasts and astrocytes engineered to produce these factors have been co-grafted along with the dopaminergic neurons or alone (19).…”