Long-acting forms of Sonic hedgehog with improved pharmacokinetic and pharmacodynamic properties are efficacious in a nerve injury model

Ficus carica L. (Fig) promotes nerve regeneration in a mouse model of sciatic nerve crush

Peripheral nerve injuries result in significant loss of motor and sensory function, and the slow rate of nerve regeneration can prolong recovery time. Thus, approaches that promote axonal regeneration are critical to improve the outcomes for patients with peripheral nerve injuries. In this study, we investigated the effects of Ficus carica L. (fig) and Vaccinium macrocarpon Ait. (cranberry), which are rich in phytochemicals with demonstrable and diverse medicinal properties, on nerve regeneration in a mouse model of sciatic nerve crush. Our investigation revealed that fig extract, but not cranberry extract, prevented the decline in muscle weight and nerve conduction velocity induced by nerve crush. The fig extract also mitigated motor function impairment, myelin thinning, and axon diameter reduction, indicating its potential to promote nerve regeneration. Furthermore, the fig extract enhanced macrophage infiltration into the nerve tissue, suggesting that it could ameliorate nerve injury by promoting tissue repair via increased macrophage infiltration. The study provides valuable insights into the potential of the fig extract as a novel agent promoting nerve regeneration. Further investigation into the mechanisms underlying the action of fig extracts is needed to translate these findings into clinical applications for patients with peripheral nerve injuries.

Brief Electrical Stimulation Promotes Recovery after Surgical Repair of Injured Peripheral Nerves

Injured peripheral nerves regenerate their axons in contrast to those in the central nervous system. Yet, functional recovery after surgical repair is often disappointing. The basis for poor recovery is progressive deterioration with time and distance of the growth capacity of the neurons that lose their contact with targets (chronic axotomy) and the growth support of the chronically denervated Schwann cells (SC) in the distal nerve stumps. Nonetheless, chronically denervated atrophic muscle retains the capacity for reinnervation. Declining electrical activity of motoneurons accompanies the progressive fall in axotomized neuronal and denervated SC expression of regeneration-associated-genes and declining regenerative success. Reduced motoneuronal activity is due to the withdrawal of synaptic contacts from the soma. Exogenous neurotrophic factors that promote nerve regeneration can replace the endogenous factors whose expression declines with time. But the profuse axonal outgrowth they provoke and the difficulties in their delivery hinder their efficacy. Brief (1 h) low-frequency (20 Hz) electrical stimulation (ES) proximal to the injury site promotes the expression of endogenous growth factors and, in turn, dramatically accelerates axon outgrowth and target reinnervation. The latter ES effect has been demonstrated in both rats and humans. A conditioning ES of intact nerve days prior to nerve injury increases axonal outgrowth and regeneration rate. Thereby, this form of ES is amenable for nerve transfer surgeries and end-to-side neurorrhaphies. However, additional surgery for applying the required electrodes may be a hurdle. ES is applicable in all surgeries with excellent outcomes.

Multiplatform molecular profiling uncovers two subgroups of malignant peripheral nerve sheath tumors with distinct therapeutic vulnerabilities

Malignant peripheral nerve sheath tumor (MPNST) is a highly aggressive sarcoma, and a lethal neurofibromatosis type 1-related malignancy, with little progress made on treatment strategies. Here, we apply a multiplatform integrated molecular analysis on 108 tumors spanning the spectrum of peripheral nerve sheath tumors to identify candidate drivers of MPNST that can serve as therapeutic targets. Unsupervised analyses of methylome and transcriptome profiles identify two distinct subgroups of MPNSTs with unique targetable oncogenic programs. We establish two subgroups of MPNSTs: SHH pathway activation in MPNST-G1 and WNT/ß-catenin/CCND1 pathway activation in MPNST-G2. Single nuclei RNA sequencing characterizes the complex cellular architecture and demonstrate that malignant cells from MPNST-G1 and MPNST-G2 have neural crest-like and Schwann cell precursor-like cell characteristics, respectively. Further, in pre-clinical models of MPNST we confirm that inhibiting SHH pathway in MPNST-G1 prevent growth and malignant progression, providing the rational for investigating these treatments in clinical trials.

The Role of c-Jun and Autocrine Signaling Loops in the Control of Repair Schwann Cells and Regeneration

After nerve injury, both Schwann cells and neurons switch to pro-regenerative states. For Schwann cells, this involves reprogramming of myelin and Remak cells to repair Schwann cells that provide the signals and mechanisms needed for the survival of injured neurons, myelin clearance, axonal regeneration and target reinnervation. Because functional repair cells are essential for regeneration, it is unfortunate that their phenotype is not robust. Repair cell activation falters as animals get older and the repair phenotype fades during chronic denervation. These malfunctions are important reasons for the poor outcomes after nerve damage in humans. This review will discuss injury-induced Schwann cell reprogramming and the concept of the repair Schwann cell, and consider the molecular control of these cells with emphasis on c-Jun. This transcription factor is required for the generation of functional repair cells, and failure of c-Jun expression is implicated in repair cell failures in older animals and during chronic denervation. Elevating c-Jun expression in repair cells promotes regeneration, showing in principle that targeting repair cells is an effective way of improving nerve repair. In this context, we will outline the emerging evidence that repair cells are sustained by autocrine signaling loops, attractive targets for interventions aimed at promoting regeneration.

Mathematical modeling of the eyespots in butterfly wings

Butterfly wing color patterns are a representative model system for studying biological pattern formation, due to their two-dimensional simple structural and high inter- and intra-specific variabilities. Moreover, butterfly color patterns have demonstrated roles in mate choice, thermoregulation, and predator avoidance via disruptive coloration, attack deflection, aposematism, mimicry, and masquerade. Because of the importance of color patterns to many aspects of butterfly biology and their apparent tractability for study, color patterns have been the subjects of many attempts to model their development. Early attempts focused on generalized mechanisms of pattern formation such as reaction-diffusion, diffusion gradient, lateral inhibition, and threshold responses, without reference to any specific gene products. As candidate genes with expression patterns that resembled incipient color patterns were identified, genetic regulatory networks were proposed for color pattern formation based on gene functions inferred from other insects with wings, such as Drosophila. Particularly detailed networks incorporating the gene products, Distal-less (Dll), Engrailed (En), Hedgehog (Hh), Cubitus interruptus (Ci), Transforming growth factor-β (TGF-β), and Wingless (Wg), have been proposed for butterfly border ocelli (eyespots) which helps the investigation of the formation of these patterns. Thus, in this work, we develop a mathematical model including the gene products En, Hh, Ci, TGF-β, and Wg to mimic and investigate the eyespot formation in butterflies. Our simulations show that the level of En has peaks in the inner and outer rings and the level of Ci has peaks in the inner and middle rings. The interactions among these peaks activate cells to produce white, black, and yellow pigments in the inner, middle, and outer rings, respectively, which captures the eyespot pattern of wild type Bicyclus anynana butterflies. Additionally, our simulations suggest that lack of En generates a single black spot and lack of Hh or Ci generates a single white spot, and a deficiency of TGF-β or Wg will cause the loss of the outer yellow ring. These deficient patterns are similar to those observed in the eyespots of Vanessa atalanta, Vanessa altissima, and Chlosyne nycteis. Thus, our model also provides a hypothesis to explain the mechanism of generating the deficient patterns in these species.

Glycosylation decreases aggregation and immunogenicity of adalimumab Fab secreted from Pichia pastoris

Glycoengineering of therapeutic proteins has been applied to improve the clinical efficacy of several therapeutics. Here, we examined the effect of glycosylation on the properties of the Fab of the therapeutic antibody, adalimumab. An N-glycosylation site was introduced at position 178 of the H chain constant region of adalimumab Fab through site-directed mutagenesis (H:L178N Fab), and the H:L178N Fab was produced in Pichia pastoris. Expressed mutant Fab contained long and short glycan chains (L-glyco Fab and S-glyco Fab, respectively). Under the condition of aggregation of Fab upon pH shift-induced stress, both of L-glyco Fab and S-glyco Fab were less prone to aggregation, with L-glyco Fab suppressing aggregation more effectively than the S-glyco Fab. Moreover, the comparison of the antigenicity of glycosylated and wild-type Fabs in mice revealed that glycosylation resulted in the suppression of antigenicity. Analysis of the pharmacokinetic behaviour of the Fab, L-glyco Fab and S-glyco Fab indicated that the half-lives of glycosylated Fabs in the rats were shorter than that of wild-type Fab, with L-glyco Fab having a shorter half-life than S-glyco Fab. Thus, we demonstrated that the glycan chain influences Fab aggregation and immunogenicity, and glycosylation reduces the elimination half-life in vivo.

Failures of nerve regeneration caused by aging or chronic denervation are rescued by restoring Schwann cell c-Jun

After nerve injury, myelin and Remak Schwann cells reprogram to repair cells specialized for regeneration. Normally providing strong regenerative support, these cells fail in aging animals, and during chronic denervation that results from slow axon growth. This impairs axonal regeneration and causes significant clinical problems. In mice, we find that repair cells express reduced c-Jun protein as regenerative support provided by these cells declines during aging and chronic denervation. In both cases, genetically restoring Schwann cell c-Jun levels restores regeneration to control levels. We identify potential gene candidates mediating this effect and implicate Shh in the control of Schwann cell c-Jun levels. This establishes that a common mechanism, reduced c-Jun in Schwann cells, regulates success and failure of nerve repair both during aging and chronic denervation. This provides a molecular framework for addressing important clinical problems, suggesting molecular pathways that can be targeted to promote repair in the PNS.

C-Terminal Cysteine PEGylation of Adalimumab Fab with an Engineered Interchain SS Bond

Conjugation with polyethylene glycol (PEG) is performed to increase serum half-life of the Fab for clinical applications. However, current designs for recombinant Fab only allow PEGylation at the interchain SS bond (disulfide bond) at the C-terminal end of the heavy chain and light chain of the Fab, which the decrease of thermostability occurred by partial reduction of the interchain SS bond. An adalimumab Fab mutant with a novel interchain SS bond (CH₁ : C177-CL : C160) and one cysteine at the C-terminal end (mutSS Fab_SH) was designed to maintain Fab thermostability and for site-specific PEGylation. MutSS Fab_SH was expressed in Pichia pastoris and purified mutSS Fab_SH was conjugated with 20-kDa PEG targeted at the free cysteine. Based on enzyme-linked immunosorbent assay (ELISA), PEGylation did not affect the binding capacity of the mutSS Fab_SH. To confirm the influence of PEGylation on the pharmacokinetic behavior of the Fab, PEGylated mutSS Fab_SH was administered to rats via tail vein injection. Analysis of the mean serum concentration of the PEGylated mutSS Fab_SH versus time through ELISA indicated an increase in half-life compared to that of non-PEGylated wild-type Fab. Consequently, we have successfully demonstrated that a Fab mutant with a novel interchain SS bond and one free cysteine at the C-terminal end can be PEGylated without changes in functionality. This design can potentially be used as a platform for modification of other recombinant Fabs.

A novel engineered interchain disulfide bond in the constant region enhances the thermostability of adalimumab Fab

We constructed a system for expressing the Fab of the therapeutic human monoclonal antibody adalimumab at a yield of 20 mg/L in the methylotrophic yeast Pichia pastoris. To examine the contribution of interchain disulfide bonds to conformational stability, we prepared adalimumab Fab from which the interchain disulfide bond at the C-terminal region at both the CH₁ and CL domains was deleted by substitution of Cys with Ala (Fab_ΔSS). DSC measurements showed that the Tm values of Fab_ΔSS were approximately 5 °C lower than those of wild-type Fab, suggesting that the interchain disulfide bond contributes to conformational thermostability. Using computer simulations, we designed a novel interchain disulfide bond outside the C-terminal region to increase the stability of Fab_ΔSS. The resulting Fab (mutSS Fab_ΔSS) had the mutations H:V177C and L:Q160C in Fab_ΔSS, confirming the formation of the disulfide bond between CH₁ and CL. The thermostability of mutSS Fab_ΔSS was approximately 5 °C higher than that of Fab_ΔSS. Therefore, the introduction of the designed interchain disulfide bond enhanced the thermostability of Fab_ΔSS and mitigated the destabilization caused by partial reduction of the interchain disulfide bond at the C-terminal region, which occurs in site-specific modification such as PEGylation.

Potent long-acting rhFGF21 analog for treatment of diabetic nephropathy in db/db and DIO mice

Background

Fibroblast growth factor 21 (FGF21) is an endocrine-acting hormone that has the potential to treat diabetic nephropathy. However, development of FGF21 into a therapeutic has been hindered due to its low intrinsic bio-stability. In our previous study, we have developed a recombinant human FGF21 (rhFGF21) variant by site-directed mutagenesis and solid-phase PEGylation, which retained its biological function. The aim of this study is to elucidate whether the therapeutic effect of PEGylated rhFGF21 (PEG-rhFGF21) on diabetic nephropathy in DIO (diet induced obesity) mice is more significant than rhFGF21 in vivo.

Results

After administration with rhFGF21 and PEG-rhFGF21 for 2 months, biochemical data and histological examination showed that PEG-rhFGF21 significantly lowered lipid levels in the kidney, decreased urine albumin/creatinine ratio (ACR) and improved mesangial expansion, demonstrating that PEG-rhFGF21 was more efficacious in ameliorating functional and morphological abnormalities induced by diabetic nephropathy in db/db and DIO mice.

Conclusions

Our findings suggest that PEG-rhFGF21 treatment is more effective in treating diabetic nephropathy than rhFGF21, through enhancements of systemic metabolic alterations and anti-inflammatory mechanisms. These findings help provide a theoretical basis to develop more long-acting and efficacious protein drugs for diabetic nephropathy.

Engineering potent long-acting variants of the Wnt inhibitor DKK2

Wnt signaling pathways are required for a wide variety of biological processes ranging from embryonic development to tissue repair and regeneration. Dickkopf-2 (DKK2) is classically defined as a canonical Wnt inhibitor, though it may play a role in activating non-canonical Wnt pathways in the context of endothelial network formation after acute injury. Here we report the discovery of a fusion partner for a DKK2 polypeptide that significantly improves the expression, biochemical properties and pharmacokinetics (PK) of the DKK2 polypeptide. Specifically, human serum albumin (HSA) was identified as a highly effective fusion partner. Substitution of selected amino acid residues in DKK2 designed to decrease heparan sulfate binding by HSA-DKK2 variants, further improved the PK properties of the molecule in rodents. The HSA-DKK2 variants were monomeric, as thermally stable as wild type, and active as measured by their ability to bind to and prevent phosphorylation of the Wnt coreceptor LRP6. Our engineering efforts resulted in potent long-lived variants of the canonical Wnt inhibitor DKK2, applicable for Wnt pathway manipulation either by systematic delivery or focused administration at sites of tissue injury.

Branching Analysis of Multivalent Conjugates Using Size Exclusion Chromatography-Multiangle Light Scattering

Multivalent conjugates (MVCs) (conjugation of multiple proteins to a linear polymer chain) are powerful for improving the bioactivity and pharmacokinetics of a bioactive molecule. Since this effect is highly dependent upon the valency of the conjugated proteins, it is imperative to have a technique for analysis of the conjugation ratio. Studies of MVCs have used size exclusion chromatography-multiangle light scattering (SEC-MALS), which allows for the separate and individual analysis of the protein and biopolymer components based on their specific refractive index increment and UV extinction coefficient constants to determine the number of proteins bound per biopolymer molecule. In this work, we have applied traditional branching analysis to the SEC-MALS data, with the primary assumption that the polymer backbone can be used as the linear counterpart. We demonstrated good agreement between the branching values and the valency determined by traditional analysis, demonstrating that branching analysis can be used as an alternative technique to approximate the valency of MVCs. The branching analysis method also provides a more complete picture of the distribution of the measured values, provides important branching information about the molecules, and lowers the cost and complexity of the characterization. However, since MVC molecules are both conjugate molecules and branched molecules, the most powerful approach to their characterization would be to use both traditional multivalent conjugate analysis and branching analysis in conjunction.

Epigenomic Regulation of Schwann Cell Reprogramming in Peripheral Nerve Injury

The rapid and dynamic transcriptional changes of Schwann cells in response to injury are critical to peripheral nerve repair, yet the epigenomic reprograming that leads to the induction of injury-activated genes has not been characterized. Polycomb Repressive Complex 2 (PRC2) catalyzes the trimethylation of lysine 27 of histone H3 (H3K27me3), which produces a transcriptionally repressive chromatin environment. We find that many promoters and/or gene bodies of injury-activated genes of mature rat nerves are occupied with H3K27me3. In contrast, the majority of distal enhancers that gain H3K27 acetylation after injury are not repressed by H3K27 methylation before injury, which is normally observed in developmentally poised enhancers. Injury induces demethylation of H3K27 in many genes, such as Sonic hedgehog (Shh), which is silenced throughout Schwann cell development before injury. In addition, experiments using a Schwann cell-specific mouse knock-out of the Eed subunit of PRC2 indicate that demethylation is a rate-limiting step in the activation of such genes. We also show that some transcription start sites of H3K27me3-repressed injury genes of uninjured nerves are bound with a mark of active promoters H3K4me3, for example, Shh and Gdnf, and the reduction of H3K27me3 results in increased trimethylation of H3K4. Our findings identify reversal of polycomb repression as a key step in gene activation after injury.

SIGNIFICANCE STATEMENT

Peripheral nerve regeneration after injury is dependent upon implementation of a novel genetic program in Schwann cells that supports axonal survival and regeneration. Identifying means to enhance Schwann cell reprogramming after nerve injury could be used to foster effective remyelination in the treatment of demyelinating disorders and in identifying pathways involved in regenerative process of myelination. Although recent progress has identified transcriptional determinants of successful reprogramming of the Schwann cell transcriptome after nerve injury, our results have highlighted a novel epigenomic pathway in which reversal of the Polycomb pathway of repressive histone methylation is required for activation of a significant number of injury-induced genes.

Multivalent Conjugates of Sonic Hedgehog Accelerate Diabetic Wound Healing

Despite their preclinical promise, few recombinant growth factors have been fully developed into effective therapies, in part, due to the short interval of therapeutic activity after administration. To address this problem, we developed nanoscale polymer conjugates for multivalent presentation of therapeutic proteins that enhance the activation of targeted cellular responses. As an example of this technology, we conjugated multiple Sonic hedgehog (Shh) proteins onto individual hyaluronic acid biopolymers to generate multivalent protein clusters at defined ratios (i.e., valencies) that yield enhanced Shh pathway activation at equivalent concentrations relative to unconjugated Shh. In this study, we investigated whether these multivalent conjugates (mvShh) could be used to improve the therapeutic function of Shh. We found that a single treatment with mvShh significantly accelerated the closure of full-thickness wounds in diabetic (db/db) mice compared to either an equivalent dose of unconjugated Shh or the vehicle control. Furthermore, we identified specific indicators of wound healing in fibroblasts and endothelial cells (i.e., transcriptional activation and cell migration) that were activated by mvShh in vitro and at concentrations approximately an order of magnitude lower than the unconjugated Shh. Taken together, our findings suggest that mvShh conjugates exhibit greater potency to activate the Shh pathway, and this multivalency advantage improves its therapeutic effect to accelerate wound closure in a diabetic animal model. Our strategy of multivalent protein presentation using nanoscale polymer conjugates has the potential to make a significant impact on the development of protein-based therapies by improving their in vivo performance.

Desert hedgehog is a mediator of demyelination in compression neuropathies

The secreted protein desert hedgehog (dhh) controls the formation of the nerve perineurium during development and is a key component of Schwann cells that ensures peripheral nerve survival. We postulated that dhh may play a critical role in maintaining myelination and investigated its role in demyelination-induced compression neuropathies by using a post-natal model of a chronic nerve injury in wildtype and dhh(-/-) mice. We evaluated demyelination using electrophysiological, morphological, and molecular approaches. dhh transcripts and protein are down-regulated early after injury in wild-type mice, suggesting an intimate relationship between the hedgehog pathway and demyelination. In dhh(-/-) mice, nerve injury induced more prominent and severe demyelination relative to their wild-type counterparts, suggesting a protective role of dhh. Alterations in nerve fiber characteristics included significant decreases in nerve conduction velocity, increased myelin debris, and substantial decreases in internodal length. Furthermore, in vitro studies showed that dhh blockade via either adenovirus-mediated (shRNA) or pharmacological inhibition both resulted in severe demyelination, which could be rescued by exogenous Dhh. Exogenous Dhh was protective against this demyelination and maintained myelination at baseline levels in a custom in vitro bioreactor to applied biophysical forces to myelinated DRG/Schwann cell co-cultures. Together, these results demonstrate a pivotal role for dhh in maintaining myelination. Furthermore, dhh signaling reveals a potential target for therapeutic intervention to prevent and treat demyelination of peripheral nerves in compression neuropathies.

Hedgehog pathway agonism: therapeutic potential and small-molecule development

The Hedgehog (Hh) pathway is a developmental signaling pathway that plays multiple roles during embryonic development and in adult tissues. Constitutive Hh signaling has been linked to the development and progression of several forms of cancer, and the application of small-molecule pathway inhibitors as anticancer chemotherapeutics is well studied and clearly defined. Activation of the Hh pathway as a therapeutic strategy for a variety of degenerative or ischemic disorders has also been proposed; however, the development of small-molecule Hh agonists has received less attention. The goal of this review is to highlight the recent evidence supporting the therapeutic potential of Hh pathway activators and to provide a comprehensive overview of small-molecule pathway agonists.

Sonic Hedgehog regulates brain-derived neurotrophic factor in normal and regenerating cavernous nerves

INTRODUCTION

The cavernous nerve (CN) is commonly injured during prostatectomy. Manipulation of the nerve microenvironment is critical to improve regeneration and develop novel erectile dysfunction therapies. Sonic hedgehog (SHH) treatment promotes CN regeneration. The mechanism of how this occurs is unknown. Brain-derived neurotrophic factor (BDNF) facilitates return of erectile function after CN injury and it has been suggested in cortical neurons and the sciatic nerve that BDNF may be a target of SHH.

AIM

To determine if SHH promotes CN regeneration through a BDNF-dependent mechanism.

METHODS

Sprague Dawley rats underwent (i) bilateral CN crush (N = 15); (ii) SHH treatment of pelvic ganglia (PG)/CN (N = 10); (iii) SHH inhibition in PG/CN (N = 14 rats); (iv) CN crush with SHH treatment of PG/CN (N = 10 rats); (v) CN crush with SHH treatment and BDNF inhibition (N = 14 rats); and (vi) CN injury and SHH treatment of the penis (N = 23).

MAIN OUTCOME MEASURES

BDNF and glial fibrillary acidic protein were quantified in PG/CN by Western, and a t-test was used to determine differences.

RESULTS

In normal rats SHH inhibition in the PG/CN decreased BDNF 34% and SHH treatment increased BDNF 36%. BDNF was increased 44% in response to SHH treatment of crushed CNs, and inhibition of BDNF in crushed CNs treated with SHH protein hampers regeneration.

CONCLUSIONS

SHH regulates BDNF in the normal and regenerating PG/CN. BDNF is part of the mechanism of how SHH promotes regeneration, thus providing an opportunity to further manipulate the nerve microenvironment with combination therapy to enhance regeneration.

PEGylation extends circulation half-life while preserving in vitro and in vivo activity of tissue inhibitor of metalloproteinases-1 (TIMP-1)

Excess proteolytic activity of matrix metalloproteinases (MMPs) contributes to the development of arthritis, cardiovascular diseases and cancer progression, implicating these enzymes as therapeutic targets. While many small molecule inhibitors of MMPs have been developed, clinical uses have been limited, in part by toxicity and off-target effects. Development of the endogenous tissue inhibitors of metalloproteinases (TIMPs) as recombinant biopharmaceuticals represents an alternative therapeutic approach; however, the short plasma half-life of recombinant TIMPs has restricted their potential in this arena. To overcome this limitation, we have modified recombinant human TIMP-1 (rhTIMP-1) by PEGylation on lysine residues. We analyzed a mixture of mono- and di-PEGylated rhTIMP-1 species modified by attachment of 20 kDa mPEG chains (PEG(20K)-TIMP-1), as confirmed by SELDI-TOF mass spectrometry. This preparation retained complete inhibitory activity toward the MMP-3 catalytic domain and partial inhibitory activity toward full length MMP-9. Pharmacokinetic evaluation showed that PEGylation extended the plasma half-life of rhTIMP-1 in mice from 1.1 h to 28 h. In biological assays, PEG(20K)-TIMP-1 inhibited both MMP-dependent cancer cell invasion and tumor cell associated gelatinase activity. Overall these results suggest that PEGylated TIMP-1 exhibits improved potential for development as an anti-cancer recombinant protein therapeutic, and additionally may offer potential for clinical applications in the treatment of other diseases.

Sonic hedgehog is neuroprotective in the cavernous nerve with crush injury

INTRODUCTION

The cavernous nerve (CN) is commonly injured during prostatectomy, resulting in erectile dysfunction (ED). Although peripheral nerves have a limited ability to regenerate, a return of function typically does not occur due to irreversible down stream morphological changes in the penis that result from CN injury. We have shown in previous studies that sonic hedgehog (SHH) is critical for CN regeneration and improves erectile function after crush injury.

AIMS

Examine a new direction, to determine if SHH is neuroprotective to the pelvic ganglia (PG)/CN after crush injury. A secondary focus is to examine if SHH signaling decreases with age in the PG/CN.

METHODS

Sprague-Dawley rats underwent bilateral CN crush and SHH and glial fibrillary acidic protein were quantified by western analysis of the PG/CN (N = 6 rats at each time point) at 1, 2, 4, 7, and 14 days, and the apoptotic index was measured in the penis. SHH was quantified by western in the PG/CN with blockade of anterograde transport (N = 4 rats) in comparison to mouse IgG (N = 4 rats). If SHH is neuroprotective was examined at 4 (N = 14 rats) and 7 days (N = 16 rats) of treatment after CN crush. SHH protein was quantified in aging (P200-300, N = 5 rats) PG/CN in comparison to normal adult (P115-120, N = 3 rats) PG/CN. Main Outcome Measures.  SHH pathway was examined in PG via immunohistochemistry, in situ, western, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL).

RESULTS

SHH is neuroprotective in the PG/CN with injury. SHH localization in the PG/CN suggests SHH interaction in neuronal/glial signaling. SHH protein is significantly decreased in the PG/CN after crush injury and in the aged PG/CN. Signals from the PG are required to maintain SHH in the CN.

CONCLUSIONS

There is a window of opportunity immediately after nerve insult in which manipulation of SHH signaling in the nerve microenvironment can affect long-term regeneration outcome.

Sonic hedgehog-modified human CD34+ cells preserve cardiac function after acute myocardial infarction

RATIONALE

Ischemic cardiovascular disease represents one of the largest epidemics currently facing the aging population. Current literature has illustrated the efficacy of autologous, stem cell therapies as novel strategies for treating these disorders. The CD34+ hematopoetic stem cell has shown significant promise in addressing myocardial ischemia by promoting angiogenesis that helps preserve the functionality of ischemic myocardium. Unfortunately, both viability and angiogenic quality of autologous CD34+ cells decline with advanced age and diminished cardiovascular health.

OBJECTIVE

To offset age- and health-related angiogenic declines in CD34+ cells, we explored whether the therapeutic efficacy of human CD34+ cells could be enhanced by augmenting their secretion of the known angiogenic factor, sonic hedgehog (Shh).

METHODS AND RESULTS

When injected into the border zone of mice after acute myocardial infarction, Shh-modified CD34+ cells (CD34(Shh)) protected against ventricular dilation and cardiac functional declines associated with acute myocardial infarction. Treatment with CD34(Shh) also reduced infarct size and increased border zone capillary density compared with unmodified CD34 cells or cells transfected with the empty vector. CD34(Shh) primarily store and secrete Shh protein in exosomes and this storage process appears to be cell-type specific. In vitro analysis of exosomes derived from CD34(Shh) revealed that (1) exosomes transfer Shh protein to other cell types, and (2) exosomal transfer of functional Shh elicits induction of the canonical Shh signaling pathway in recipient cells.

CONCLUSIONS

Exosome-mediated delivery of Shh to ischemic myocardium represents a major mechanism explaining the observed preservation of cardiac function in mice treated with CD34(Shh) cells.

Regeneration of the cavernous nerve by Sonic hedgehog using aligned peptide amphiphile nanofibers

SHH plays a significant role in peripheral nerve regeneration and has clinical potential to be used as a regenerative therapy for the CN in prostatectomy patients and in other patients with neuropathy of peripheral nerves. Efforts to regenerate the cavernous nerve (CN), which provides innervation to the penis, have been minimally successful, with little translation into improved clinical outcomes. We propose that, Sonic hedgehog (SHH), is critical to maintain CN integrity, and that SHH delivered to the CN by novel peptide amphiphile (PA) nanofibers, will promote CN regeneration, restore physiological function, and prevent penile morphology changes that result in erectile dysfunction (ED). We performed localization studies, inhibition of SHH signaling in the CN, and treatment of crushed CNs with SHH protein via linear PA gels, which are an innovative extended release method of delivery. Morphological, functional and molecular analysis revealed that SHH protein is essential to maintain CN architecture, and that SHH treatment promoted CN regeneration, suppressed penile apoptosis and caused a 58% improvement in erectile function in less than half the time reported in the literature. These studies show that SHH has substantial clinical application to regenerate the CN in prostatectomy and diabetic patients, that this methodology has broad application to regenerate any peripheral nerve that SHH is necessary for maintenance of its structure, and that this nanotechnology method of protein delivery may have wide spread application as an in vivo delivery tool in many organs.

Peptide amphiphile nanofiber delivery of sonic hedgehog protein to reduce smooth muscle apoptosis in the penis after cavernous nerve resection

INTRODUCTION

Erectile dysfunction (ED) is a serious medical condition that affects 16-82% of prostate cancer patients treated by radical prostatectomy and current treatments are ineffective in 50-60% of prostatectomy patients. The reduced efficacy of treatments makes novel therapeutic approaches to treat ED essential. The secreted protein Sonic hedgehog (SHH) is a critical regulator of penile smooth muscle and apoptosis that is decreased in cavernous nerve (CN) injury and diabetic ED models. Past studies using Affi-Gel beads have shown SHH protein to be effective in suppressing apoptosis caused by CN injury.

AIM

We hypothesize that SHH protein delivered via novel peptide amphiphile (PA) nanofibers will be effective in suppressing CN injury-induced apoptosis.

METHODS

Adult Sprague Dawley rats (n=50) were used to optimize PA injection in vivo. PA with SHH protein (n=16) or bovine serum albumin (BSA) (control, n=14) was injected into adult rats that underwent bilateral CN cut. Rats were sacrificed at 2, 4, and 7 days. Alexa Fluor-labeled SHH protein was used to determine the target of SHH signaling (n=3).

MAIN OUTCOME MEASURES

Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and semiquantitative immunohistochemical analysis for SHH protein and cluster differentiation protein three (CD3) were performed.

RESULTS

SHH-PA caused a 25% and 16% reduction in apoptosis at 4 and 7 days after CN injury and a 9.3% and 19% increase in SHH protein at 4 and 7 days after CN injury. CD3 protein was not observed in SHH-PA-treated penis. In vitro, 73% of SHH protein diffused from PA within 6 days. Labeled SHH was observed in smooth muscle.

CONCLUSIONS

PA technology is effective in delivering SHH protein to the penis and SHH is effective in suppressing CN injury-induced apoptosis. These results suggest substantial translational potential of this methodology and show that only a short duration of SHH treatment is required to impact the apoptotic index.

1-amino-4-benzylphthalazines as orally bioavailable smoothened antagonists with antitumor activity

Abnormal activation of the Hedgehog (Hh) signaling pathway has been linked to several types of human cancers, and the development of small-molecule inhibitors of this pathway represents a promising route toward novel anticancer therapeutics. A cell-based screen performed in our laboratories identified a new class of Hh pathway inhibitors, 1-amino-4-benzylphthalazines, that act via antagonism of the Smoothened receptor. A variety of analogues were synthesized and their structure-activity relationships determined. This optimization resulted in the discovery of high affinity Smoothened antagonists, one of which was further profiled in vivo. This compound displayed a good pharmacokinetic profile and also afforded tumor regression in a genetic mouse model of medulloblastoma.

Purifying the hedgehog protein and its variants

The purification of recombinant versions of the N-terminal signaling fragment of Sonic hedgehog (ShhN) from E. coli, Hi-5 insect cells, yeast, and mammalian cell sources reveals diverse post-translational modifications that affect the potency of the purified protein. Modifications to the N-terminal cysteine with fatty acyl groups results in significant increases in potency, up to 100-fold, when compared with the unmodified protein. Proteolytic clipping at sites near the N-terminus results in inactivation of signaling activity. The ShhN protein is particularly sensitive to metal ion-induced oxidation, and the methods described here were developed to minimize this oxidation. The purification methods developed for ShhN were applicable to human Indian and Desert hedgehog N-terminal signaling proteins, and therefore should be useful for hedgehog proteins from other species.

A beta-lactamase reporter assay for monitoring the activation of the smoothened pathway

The seven-transmembrane protein Smoothened (Smo) mediates the cellular response to the Hedgehog protein signal and is involved in cell growth and differentiation during embryonic development. Stimulation of the Smo pathway is directly implicated in tissue maintenance and repair, but overactivation of Smo could lead to tumorigenesis. We developed a robust and sensitive functional cell-based assay that measures the activity of endogenous Smo using a beta-lactamase transcriptional readout. This is the first Smo reporter assay that utilizes beta-lactamase reporter technology. This assay type has distinct advantages over other reporter technologies and can be used in a high-throughput mode to search for therapeutically relevant downstream Smo target effectors.

Sonic hedgehog is an autocrine viability factor for myofibroblastic hepatic stellate cells

BACKGROUND/AIMS

Factors released during liver injury, such as platelet derived growth factor-BB (PDGF), promote accumulation of myofibroblastic hepatic stellate cells (MFB) that drive the pathogenesis of cirrhosis. The hedgehog (Hh) pathway regulates remodeling of other injured tissues. This study evaluates the hypothesis that autocrine production of Sonic hedgehog (Shh) promotes MFB growth.

METHODS

Primary rat hepatic stellate cells (HSC) were treated without or with PDGF, a pharmacologic inhibitor of PDGF-regulated kinases, adenovirus expressing activated or dominant negative AKT, or Hh signaling inhibitors. Shh production, expression of Hh inhibitors and target genes, and HSC growth were assessed.

RESULTS

HSC expressed Shh, Hh pathway components, and the Hh inhibitor, Hip. During culture Hip expression fell, Shh production increased, and Hh target gene expression was induced. Neutralizing Shh antibodies promoted apoptosis. Adding PDGF increased Shh expression and MFB growth. Both processes followed activation of AKT and were abrogated by AKT inhibitors. Adenoviral delivery of activated AKT up-regulated Shh expression, demonstrating a direct role for AKT in regulating Shh expression. Shh-neutralizing antibodies and other Hh pathway inhibitors blocked the mitogenic effects of PDGF.

CONCLUSIONS

These results identify Shh as an autocrine growth factor for MFB and suggest a role for Hh signaling in the pathogenesis of cirrhosis.

Small molecules in stem cell self-renewal and differentiation

The use of stem cells in regenerative medicine is a promising approach to the treatment of disease and injury. Natural and synthetic small molecules have been shown to be useful chemical tools for controlling and manipulating the fates of cells. Small molecules can target signaling transduction pathways (for example, tyrosine kinase receptors) and affect DNA replication, cell differentiation, tumor metastasis and apoptosis. Stem cells share many properties with cancer cells and these similarities can provide insights to control and direct cell behavior; small molecules are already standard chemotherapeutics in the treatment of cancer. Libraries of small molecules have been examined for anticancer behavior (especially apoptosis), and, more recently, for stem cell self-renewal and differentiation capabilities in potential approaches to regenerative medicine. Differentiation therapy for cancer is based on the idea that cancer cells are undifferentiated embryonic-like cells and proposes to promote the differentiation and hence block cell proliferation. For example, retinoids have a role in stem cell differentiation to several lineages and have also been used to promote differentiation of acute promyeloic leukemic cells. Small molecules are also important tools for understanding mechanistic and developmental processes. Strategies for generating functional small molecule libraries have been outlined previously. In this review, we will look at several small molecules that have been described in the recent literature as effectors of stem cell self-renewal or differentiation as associated with the Wnt, Hedgehog or NF-kappaB pathways.

Conditional deletion of beta1 integrins in the intestinal epithelium causes a loss of Hedgehog expression, intestinal hyperplasia, and early postnatal lethality

Conditional deletion of β1 integrins in the intestinal epithelium, unlike in epidermal and mammary epithelia, of mice does not result in decreased cell adhesion and proliferation, but instead causes a profound increase in epithelial proliferation with dysplasia and polypoid structures. The increased epithelial proliferation inhibited epithelial differentiation that caused severe malnutrition and early postnatal lethality. The striking similarities between β1 integrin–deleted mice and neonatal mice with defective Hedgehog signaling led to the discovery that Hedgehog expression was markedly reduced in the former mice. β1 integrins were found to drive the expression of Hedgehogs in intestinal epithelial cells in an HNF-3β (Foxa2)–dependent fashion. The expression of Tcf-4, a transcription factor known to be required for intestinal epithelial stem cell proliferation, was increased and mislocalized in the intestinal epithelia of the β1 integrin–deleted mice and in newborn mice treated with the Hedgehog signaling inhibitor cyclopamine. This study shows that β1 integrins are key regulators of proliferation and homeostasis in the intestine and achieve this not through anchorage-dependent effects but by generating Hh expression and signaling.

THE HEDGEHOG PATHWAY AND NEUROLOGICAL DISORDERS

The hedgehog pathway is a major regulator of embryonic development, and mutations that decrease its activity are known to be associated with severe defects in nervous system development. Recent evidence suggests hedgehog continues to function in adult tissue, normal as well as diseased, by regulating both cell proliferation and the production of growth and angiogenic factors. In the adult nervous system, this dual ability is especially important in regulating the behavior of neural stem and progenitor cells. This review summarizes information connecting hedgehog signaling and neural diseases, including neurodegenerative disorders and brain tumors, particularly medulloblastoma. We also describe the discovery and utility of small molecule agonists and antagonists of this pathway and their potential as novel types of therapeutics.

The structural and functional integrity of peripheral nerves depends on the glial-derived signal desert hedgehog

We show that desert hedgehog (dhh), a signaling molecule expressed by Schwann cells, is essential for the structural and functional integrity of the peripheral nerve. Dhh-null nerves display multiple abnormalities that affect myelinating and nonmyelinating Schwann cells, axons, and vasculature and immune cells. Myelinated fibers of these mice have a significantly increased (more than two times) number of Schmidt-Lanterman incisures (SLIs), and connexin 29, a molecular component of SLIs, is strongly upregulated. Crossing Dhh-null mice with myelin basic protein (MBP)-deficient shiverer mice, which also have increased SLI numbers, results in further increased SLIs, suggesting that Dhh and MBP control SLIs by different mechanisms. Unmyelinated fibers are also affected, containing many fewer axons per Schwann cell in transverse profiles, whereas the total number of unmyelinated axons is reduced by approximately one-third. In Dhh-null mice, the blood-nerve barrier is permeable and neutrophils and macrophage numbers are elevated, even in uninjured nerves. Dhh-null nerves also lack the largest-diameter myelinated fibers, have elevated numbers of degenerating myelinated axons, and contain regenerating fibers. Transected dhh nerves degenerate faster than wild-type controls. This demonstrates that a single identified glial signal, Dhh, plays a critical role in controlling the integrity of peripheral nervous tissue, in line with its critical role in nerve sheath development (Parmantier et al., 1999). The complexity of the defects raises a number of important questions about the Dhh-dependent cell-cell signaling network in peripheral nerves.

Hedgehog signaling maintains resident hepatic progenitors throughout life

Hedgehog signaling through its receptor, Patched, activates transcription of genes, including Patched, that regulate the fate of various progenitors. Although Hedgehog signaling is required for endodermal commitment and hepatogenesis, the possibility that it regulates liver turnover in adults had not been considered because mature liver epithelial cells lack Hedgehog signaling. Herein, we show that this pathway is essential throughout life for maintaining hepatic progenitors. Patched-expressing cells have been identified among endodermally lineage-restricted, murine embryonic stem cells as well as in livers of fetal and adult Ptc-lacZ mice. An adult-derived, murine hepatic progenitor cell line expresses Patched, and Hedgehog-responsive cells exist in stem cell compartments of fetal and adult human livers. In both species, manipulation of Hedgehog activity influences hepatic progenitor cell survival. Therefore, Hedgehog signaling is conserved in hepatic progenitors from fetal development through adulthood and may be a new therapeutic target in patients with liver damage.

Desert hedgehog-patched 2 expression in peripheral nerves during Wallerian degeneration and regeneration

Hedgehog proteins are important in the development of the nervous system. As Desert hedgehog (Dhh) is involved in the development of peripheral nerves and is expressed in adult nerves, it may play a role in the maintenance of adult nerves and degeneration and regeneration after injury. We firstly investigated the Dhh-receptors, which are expressed in mouse adult nerves. The Dhh receptor patched(ptc)2 was detected in adult sciatic nerves using RT-PCR, however, ptc1 was undetectable under the same experimental condition. Using RT-PCR in purified cultures of mouse Schwann cells and fibroblasts, we found ptc2 mRNA in Schwann cells, and at much lower levels, in fibroblasts. By immunohistochemistry, Ptc2 protein was seen on unmyelinated nerve fibers. Then we induced crush injury to the sciatic nerves of wild-type (WT) and dhh-null mice and the distal stumps of injured nerves were analyzed morphologically at different time points and expression of dhh and related receptors was also measured by RT-PCR in WT mice. In dhh-null mice, degeneration of myelinated fibers was more severe than in WT mice. Furthermore, in regenerated nerves of dhh-null mice, minifascicular formation was even more extensive than in dhh-null intact nerves. Both dhh and ptc2 mRNA levels were down-regulated during the degenerative phase postinjury in WT mice, while levels rose again during the phase of nerve regeneration. These results suggest that the Dhh-Ptc2 signaling pathway may be involved in the maintenance of adult nerves and may be one of the factors that directly or indirectly determines the response of peripheral nerves to injury.

Role for hedgehog signaling in hepatic stellate cell activation and viability

Hepatic stellate cells (HSC) have a complex phenotype that includes both neural and myofibroblastic features. The Hedgehog (Hh) pathway has been shown to direct the fate of neural and myofibroblastic cells during embryogenesis and during tissue remodeling in adults. Therefore, we hypothesized that Hh signaling may regulate the fate of HSC in adults. In this study, we find that freshly isolated stellate cells from adult Patched-lacZ transgenic mice exhibit beta-galactosidase activity, indicating Hh pathway activity. Transcripts of Hh ligands, the Hh pathway receptor, and Hh-regulated transcription factors are expressed by stellate cells from mice, rats, and humans. Transfection experiments in a cell line using a Hh-inducible luciferase reporter demonstrate constitutive Hh pathway activity. Moreover, neutralizing antibodies to Hh increase apoptosis, while viability is restored by treatment with Hh ligand. In vitro treatment of primary stellate cells with cyclopamine (Cyc), a pharmacologic inhibitor of the Hh pathway, inhibits activation and slightly decreases cell survival, while a single injection of Cyc into healthy adult mice reduces activation of HSC by more than 50% without producing obvious liver damage. Our findings reveal a novel mechanism, namely the Hh pathway, that regulates the activation and viability of HSC.

Brain as a paradigm of organ growth: Hedgehog-Gli signaling in neural stem cells and brain tumors

The Hedgehog-Gli (Hh-Gli) signaling pathway is essential for numerous events during the development of many animal cell types and organs. In particular, it controls neural cell precursor proliferation in dorsal brain structures and regulates the number of neural stem cells in distinct embryonic, perinatal, and adult niches, such as the developing neocortex, the subventricular zone of the lateral ventricle of the forebrain, and the hippocampus. We have proposed that Hh-Gli signaling regulates dorsal brain growth during ontogeny and that its differential regulation underlays evolutionary change in the morphology (size and shape) of dorsal brain structures. It is also critically involved in sporadic brain tumorigenesis--as well as several other human cancer--suggesting that tumors derive from stem cells or progenitors maintaining an inappropriate active Hh-Gli pathway. Importantly, we and others have demonstrated that human sporadic tumors from the brain and other organs require sustained HH-GLI signaling for sustained growth and survival. Modulating HH-GLI signaling thus represents a novel rational avenue to treat, on one hand, brain degeneration and injury by inducing controlled HH-GLI-mediated regeneration and growth, and on the other hand, to combat cancer by blocking its abnormal activity in tumor cells.

Purmorphamine induces osteogenesis by activation of the hedgehog signaling pathway

Previously, a small molecule, purmorphamine, was identified that selectively induces osteogenesis in multipotent mesenchymal progenitor cells. In order to gain insights into the mechanism of action of purmorphamine, high-density oligonucleotide microarrays were used to profile gene expression in multipotent mesenchymal progenitor cells treated with either purmorphamine or bone morphogenetic protein-4 (BMP-4). In contrast to BMP-4 treatment, purmorphamine activates the Hedgehog (Hh) signaling pathway, resulting in the up- and downregulation of its downstream target genes, including Gli1 and Patched. Moreover, the known Hh signaling antagonists, cyclopamine and forskolin, completely block the osteogenesis and Glimediated transcription induced by purmorphamine. These results demonstrate that purmorphamine is a small molecule agonist of Hedgehog signaling, and it may ultimately be useful in the treatment of bone-related disease and neurodegenerative disease.

Basal cell nevus syndrome

PURPOSE OF REVIEW

Basal cell nevus syndrome (BCNS), is a hereditary condition transmitted as an autosomal dominant trait exhibiting high penetrance and variable expressivity. Inherited or spontaneous mutations in the human homologue of the Drosophila patched gene underlie the disorder and in addition to tumor predisposition, are associated with a range of 'patterning' defects. Recent advances, with glimpses of possible therapies are emerging, but because of the wide-ranging nature of phenotypic expression and overlap with other syndromes, there is difficulty. Finally, because of the importance of PTCH and paralogous genes in many species other than humans, reports appear in a correspondingly wide range of journals, which makes 'keeping abreast' difficult.

RECENT FINDINGS

Progress has been achieved in understanding the role of Gli-1, 2, & 3 in development of 'sporadic' BCCs and BCNS. Expression of PTCH1 is now known to be regulated by alternative promoters and a single functional Gli-binding site. Expression of FOXE1 as a new transcriptional target of Gli2 has been demonstrated in human epidermis and BCCs. Finally, the discovery of Shh pathway inhibitors such as cyclopamine, a naturally occurring alkaloid and ornithine decarboxylase inhibition suggest possible interventional therapies.

SUMMARY

In BCNS, phenotype does not correlate with position of mutations within Patched, suggesting genetic makeup and environment modulate effects of premature protein truncation induced by PTCH mutation. These developmental abnormalities occur as a result of haplo-insufficiency in heterozygotes for the mutated gene, whereas neoplastic complications arise from a classical two-hit tumor suppressor gene model. Attention is therefore turning toward TP53 and PTCH associations.

Hydrophobized dextran-spermine conjugate as potential vector for in vitro gene transfection

Dextran polysaccharide was grafted by reductive-amination with mixtures of spermine and other natural/synthetic oligoamines of two to four amine groups. The transfection efficiencies of the polycations thus obtained were assessed in various cell lines, and found to depend on the spermine contents. Higher spermine ratios of grafted oligoamines resulted in high gene expression, whereas low to negligible expressions were obtained with lower spermine contents. The effect was explained by spermine residues which exhibit altered buffering capacity in comparison to other substituted oligoamines. Hydrophobization of dextran-spermine (D-SPM) was achieved by treating the polymer with N-hydroxysuccinimide derivatives of cholesterol and fatty acids in a mixture of water/THF. The degree of hydrophobization was in the range of 1-30% mol/mol (hydrophobic moieties/primary amine) and the coupling yields were >95% as determined by (1)H-NMR. The oleate-modified D-SPM remarkably enhanced the gene expression in serum rich media, in marked contrast to unmodified D-SPM which resulted with a drastic decrease in the transfection yields. Modified D-SPM derivatives of other fatty acids and cholesterol showed improved transfection yields in comparison to unmodified D-SPM, but to a lower extent when compared to oleate modification. The improvement in cell transfection was attributed to oleate residues which probably play a role in increasing stability and uptake of polycation-DNA complexes.

Characterization of Site-Specific ScFv PEGylation for Tumor-Targeting Pharmaceuticals

New radiopharmaceuticals are possible using site-specific conjugation of small tumor binding proteins and poly(ethylene glycol) (PEG) scaffolds to provide modular multivalent, homo- or heterofunctional cancer-targeting molecules having preferred molecular size, valence, and functionality. Residence time in plasma can be optimized by modification of the size, number, and charge of the protein units. However, random PEG conjugation (PEGylation) of these small molecules via amine groups has led to variations of structural conformation and binding affinity. To optimize PEGylation, scFvs have been recombinantly produced in a vector that adds an unpaired cysteine (c) near the scFv carboxy terminus (scFv-c), thus providing a specific site for thiol conjugation. To evaluate the general applicability of this unpaired cysteine for PEGylation of scFv-c, conjugation efficiency was determined for four different scFvs and several PEG molecules having thiol reactive groups. The effect of the PEG molecular format on scFv-c PEG malignant cell binding was also addressed. ScFvs produced as scFv-c and purified by anti E-TAG affinity chromatography were conjugated using PEG molecules with maleimide (Mal) or o-pyridyl disulfide (OPSS). Conjugations were performed at pH 7.0, with 2 molar excess TCEP/scFv and PEG-(Mal) or PEG-OPSS, using 5:1 (PEG/scFv). PEG-Mal conjugation efficiency was also evaluated with 1:5 (PEG/scFv). PEGylation efficiency was determined for each reaction by quantitation of the products on SDS-PAGE. ScFv-c conjugation with unifunctional maleimide PEGs resulted in PEG conjugates incorporating 30-80% of the scFv-c, but usually above 50%. Efficiency of scFv-c conjugation to both functional groups of the bifunctional PEG-(Mal)2 varied between the PEG and scFv-c molecules studied. A maximum of 45% of scFv-c protein was conjugated as PEG- (scFv-c)2 using the smallest PEG-(Mal)2 (2 kDa). No significant increase in scFv-c conjugation was observed by the use of greater than a 5 molar excess of PEG/scFv-c. Under the same conjugation conditions, PEG as OPSS yielded less than 10% PEG-scFv-c. PEG-(scFv)2 conjugates had increased binding in ELISA using malignant cell membranes, when compared with unmodified scFv-c. PEGylated-scFv binding was comparable with unmodified scFv-c. In summary, scFv-c can be PEGylated in a site-specific manner using uni- or bivalent PEG-Mal, either linear or branched. ScFv-c was most efficiently conjugated to smaller PEG-Mal molecules, with the smallest, 2 kDa PEG-Mal, usually PEGylating 60-90% of the scFv-c. ScFv-c conjugation to form PEG-(scFv-c)2 reached greatest efficiency at 45%, and its purified form demonstrated greater binding than the corresponding scFv-c.

Hedgehog interacting protein in the mature brain: membrane-associated and soluble forms

Hedgehog interacting protein (Hip) is considered as a membrane protein implicated in sequestering the hedgehog (hh) morphogens during embryonic development. Here, we demonstrate that Hip transcription also occurs in cells scattered in discrete brain areas of adult rodents and we identify the presence of membrane-associated and soluble forms of Hip in the mature brain. Moreover, we show that soluble forms of Hip, present in the conditioned medium of HEK293 cells overexpressing Hip, inhibit Sonic hedgehog (Shh)-induced differentiation of C3H10T1/2 cells, a well-characterised response associated with Shh signalling. After transfection in HEK293 cells, Hip partitions with the raft component ganglioside GM1 during density gradient centrifugation. Analysis of tagged Hip constructs reveals that the putative transmembrane domain of Hip is not cleaved suggesting that other mechanisms are implicated in the release of its soluble forms. Taken together, these data are consistent with the involvement of both membrane-associated and soluble Hip in the regulation of Shh signalling in adult neural tissues.

PEGylation of a vesicular stomatitis virus G pseudotyped lentivirus vector prevents inactivation in serum

One disadvantage of vesicular stomatitis virus G (VSV-G) pseudotyped lentivirus vectors for clinical application is inactivation of the vector by human serum complement. To prevent this, monomethoxypoly(ethylene) glycol was conjugated to a VSV-G-human immunodeficiency virus vector expressing Escherichia coli beta-galactosidase. The modification did not affect transduction efficiency in vitro and protected the vector from inactivation in complement-active human and mouse sera. Blood from mice dosed intravenously with either the unmodified or the PEGylated virus particles was assayed for active vector by a limiting-dilution assay to evaluate transduction efficiency and for p24, an indicator of the total number of virus particles present. PEGylation extended the circulation half-life of active vector by a factor of 5 and reduced the rate of vector inactivation in the serum by a factor of 1,000. Pharmacokinetic profiles for the total number of virus particles present in the circulation were unaffected by PEGylation. Modification of the vector with poly(ethylene) glycol significantly enhanced transduction efficiency in the bone marrow and in the spleen 14 days after systemic administration of the virus. These results, in concert with the pharmacokinetic profiles, indicate that PEGylation does protect the virus from inactivation in the serum and, as a result, improves the transduction efficiency of VSV-G pseudotyped lentivirus vectors in susceptible organs in vivo.

Dextran–spermine polycation: an efficient nonviral vector for in vitro and in vivo gene transfection

Dextran-spermine cationic polysaccharide was prepared by means of reductive amination between oxidized dextran and the natural oligoamine spermine. The formed Schiff-base imine-based conjugate was reduced with borohydride to obtain the stable amine-based conjugate. The transfection efficiency of the synthetic dextran-spermine was assessed in vitro on HEK293 and NIH3T3 cell lines and found to be as high as the DOTAP/Chol 1/1 lipid-based transfection reagent. Modification of the dextran-spermine polycation with polyethylene glycol resulted in high transfection yield in serum-rich medium. Intramuscular injection in mice of dextran-spermine-pSV-LacZ complex induced high local gene expression compared to low expression of the naked DNA. Intravenous injection of a dispersion of the dextran-spermine-pSV-LacZ complex resulted with no expression in all examined organs. When the partially PEGylated dextran-spermine-pSV-LacZ complex was intravenously applied, a high gene expression was detected mainly in the liver. Preliminary targeting studies indicated that the PEGylated dextran-spermine-pSV-LacZ complex bound to galactose receptor of liver parenchymal cells rather than the mannose receptor of liver nonparenchymal cells. This work offers a new biodegradable polycation based on natural components, which is capable of transfecting cells and tissues in vitro and in vivo.

The Hedgehog signaling pathway--implications for drug targets in cancer and neurodegenerative disorders

The Hedgehog (Hh) pathway is a highly conserved signaling cascade involved in many developmental processes. Among others, these include patterning of the ventral neural tube and establishment of left-right asymmetry of the embryo. Additionally, the pathway regulates the development of numerous tissues and cell types. Mutations in elements of the pathway are associated with congenital diseases and defects, and ectopic Hh signaling activity is implicated in the development of a number of neoplasms. While little is known of Hh signaling function in the adult organism, a role of the pathway in maintenance of adult organs and cell types, including several neuronal subtypes in the central nervous system, is beginning to emerge. Elements of the Hh pathway are therefore potential drug targets for the treatment of cancers and degenerative diseases like Parkinson's disease, and the recent isolation of synthetic molecules capable of modulating the activity of the Hh cascade through a direct interaction with elements of the pathway is promising.

Expression of Sonic hedgehog-Fc fusion protein in Pichia pastoris. Identification and control of post-translational, chemical, and proteolytic modifications

We have investigated the suitability of Pichia pastoris as an expression system for the candidate therapeutic protein, Sonic hedgehog fused to an immunoglobulin Fc domain (Shh-Fc). Sonic hedgehog is a morphogen protein involved in the patterning of a wide range of tissues during animal embryogenesis. The presence of Sonic hedgehog and its receptor, Patched, in adult nervous tissue suggests possible applications for the protein in the treatment of neurodegenerative disease and injury. We have engineered the Shh-Fc fusion protein in order to improve binding affinity and increase systemic exposure in animals. N-terminal sequencing, peptide mapping, mass spectrometry, and other biochemical and biological methods were used to characterize the purified protein. These analyses revealed several unanticipated problems, including thiaproline modification of the N-terminal cysteine, cleavage by a Kex2-like protease at a site near the N-terminus, proteolysis at sites near the hinge, addition of a hexose in the CH3 domain of the Fc region, and several sites of methionine oxidation. Sequence modifications to the protein and changes in fermentation conditions resulted in increased potency and greater consistency of the product. The final product was shown to be biologically active in animal studies.

Therapeutic efficacy of sonic hedgehog protein in experimental diabetic neuropathy

Hedgehog proteins modulate development and patterning of the embryonic nervous system. As expression of desert hedgehog and the hedgehog receptor, patched-1, persist in the postnatal and adult peripheral nerves, the hedgehog pathway may have a role in maturation and maintenance of the peripheral nervous system in normal and disease states. We measured desert hedgehog expression in the peripheral nerve of maturing diabetic rats and found that diabetes caused a significant reduction in desert hedgehog mRNA. Treating diabetic rats with a sonic hedgehog-IgG fusion protein fully restored motor- and sensory-nerve conduction velocities and maintained the axonal caliber of large myelinated fibers. Diabetes-induced deficits in retrograde transport of nerve growth factor and sciatic-nerve levels of calcitonin gene-related product and neuropeptide Y were also ameliorated by treatment with the sonic hedgehog-IgG fusion protein, as was thermal hypoalgesia in the paw. These studies implicate disruption of normal hedgehog function in the etiology of diabetes-induced peripheral-nerve dysfunction and indicate that delivery of exogenous hedgehog proteins may have therapeutic potential for the treatment of diabetic neuropathy.

Pathways and consequences: Hedgehog signaling in human disease

Signaling pathways that play a fundamental role during development are turning out to underlie many disease states when misregulated. Here, we review some of the recent findings in the Hedgehog (Hh) pathway and the role it plays in different human diseases. We present a summary of the diseases that result from the inactivation or inappropriate activation of the Hh pathway. The human phenotypes generally fit the findings in model organisms and help to identify some potential targets for therapy.

Intrastriatal sonic hedgehog injection increases Patched transcript levels in the adult rat subventricular zone

The morphogen sonic hedgehog (Shh) is implicated in neural tissue patterning and the growth of brain structures during embryogenesis and postnatal development and is also present in the adult brain. Shh signals through interaction with the tumour suppressor Patched (Ptc). This receptor for Shh is associated with Smoothened (Smo), a protein with high homology to the G-protein coupled receptors. However, little is known about the transduction mechanisms implicated in Shh signalling in the adult brain. The study described here shows that injection of aminoterminal myristoylated Shh (myrShhN) into the adult rat striatum robustly increases the levels of Ptc transcripts in selective brain areas including the subventricular zone (SVZ). The adult SVZ contains cell progenitors, which can proliferate and differentiate into new neurons and glia. In the myrShhN injected animals, proliferation and differentiation of these SVZ precursor cells were not affected as demonstrated by BrdU incorporation and immunohistochemistry performed with specific antibodies for nestin (uncommitted neural progenitors), PSA-NCAM (migrating neuroblasts) or GFAP (astrocytes). Together with the presence of Smo expressing cells and amino-terminal Shh (ShhN) protein in SVZ area of untreated animals, the data presented here supports the hypothesis that the Shh pathway may be activated in the adult brain, and that a niche for Shh signalling exists within the adult SVZ.

Agonizing hedgehog

An approach using 'chemical genetics' has identified small-molecule agonists of the Hedgehog signaling pathway that may lead the way to drugs for chronic degenerative diseases.