Enhanced local delivery with reduced systemic toxicity: Delivery, delivery, and delivery

Where is human-based cellular pharmaceutical R&D taking us in cartilage regeneration?

Lately, cellular-based cartilage joint therapies have gradually gained more attention, which leads to next generation bioengineering approaches in the development of cell-based medicinal products for human use in cartilage repair. The greatest hurdles of chondrocyte-based cartilage bioengineering are: (i) preferring the cell source; (ii) differentiation and expansion processes; (iii) the time necessary for chondrocyte expansion pre-implantation; and (iv) fixing the chondrocyte count in accordance with the lesion surface area of the patient in question. The chondrocyte presents itself to be the focal starting material for research and development of bioengineered cartilage-based medicinal products which promise the regeneration and restoration of non-orthopedic cartilage joint defects. Even though chondrocytes seem to be the first choice, inevitable complications related to proliferation, dedifferentation and redifferentiation are probable. Detailed studies are a necessity to fully investigate detailed culturing conditions, the chondrogenic strains of well-defined phenotypes and evaluation of the methods to be used in biomaterial production. Despite a majority of the current methods which aid amelioration of joint functionality, they are insufficient in fully restoring the natural structure and composition of the joint cartilage. Hence current studies have trended towards gene therapy, mesenchymal stem cells and tissue engineering practices. There are many studies addressing the outcomes of chondrocytes in the clinical scene, and many vital biomaterials have been developed for structuring the bioengineered cartilage. This study aims to convey to the audience the practical significance of chondrocyte-based clinical applications.

Customized biomaterials to augment chondrocyte gene therapy

A persistent challenge in enhancing gene therapy is the transient availability of the target gene product. This is particularly true in tissue engineering applications. The transient exposure of cells to the product could be insufficient to promote tissue regeneration. Here we report the development of a new material engineered to have a high affinity for a therapeutic gene product. We focus on insulin-like growth factor-I (IGF-I) for its highly anabolic effects on many tissues such as spinal cord, heart, brain and cartilage. One of the ways that tissues store IGF-I is through a group of insulin like growth factor binding proteins (IGFBPs), such as IGFBP-5. We grafted the IGF-I binding peptide sequence from IGFBP-5 onto alginate in order to retain the endogenous IGF-I produced by transfected chondrocytes. This novel material bound IGF-I and released the growth factor for at least 30days in culture. We found that this binding enhanced the biosynthesis of transfected cells up to 19-fold. These data demonstrate the coordinated engineering of cell behavior and material chemistry to greatly enhance extracellular matrix synthesis and tissue assembly, and can serve as a template for the enhanced performance of other therapeutic proteins.

STATEMENT OF SIGNIFICANCE

The present manuscript focuses on the enhancement of chondrocyte gene therapy through the modification of scaffold materials to enhance the retention of targeted gene products. This study combined tissue engineering and gene therapy, where customized biomaterials augmented the action of IGF-I by enhancing the retention of protein produced by transfection of the IGF-I gene. This approach enabled tuning of binding of IGF-I to alginate, which increased GAG and HYPRO production by transfected chondrocytes. To our knowledge, peptide-based modification of materials to augment growth factor-targeted gene therapy has not been reported previously.

Prevention of intrahepatic metastasis of liver cancer by suicide gene therapy and chemokine ligand 2/monocyte chemoattractant protein-1 delivery in mice

BACKGROUND

The prognosis of patients with hepatocellular carcinoma (HCC) remains poor, largely as a result of intrahepatic metastasis. Using a mouse model of intrahepatic metastasis, we investigated whether chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2/MCP-1) could potentiate the antitumor effects of the herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) system.

METHODS

Mouse hepatoma cells infected with recombinant adenovirus vectors expressing HSV-tk, CCL2/MCP-1 and LacZ at multiplicities of infection of Ad-tk/Ad-MCP1 = 3/0.03 (T/M(Low)), 3/3 (T/M(High)) and Ad-tk/Ad-LacZ = 3/3 (T/L) were injected into BALB/c mice.

RESULTS

Intrahepatic tumor growth was significantly lower in T/M(Low) mice. By contrast, no tumor suppression was observed in T/M(High) mice. The tumor-specific cytolytic activities of splenocytes from T/M(Low) and T/M(High) mice were comparable. Immunohistochemical analysis of liver tissues showed similar infiltration by Mac-1(+) and T cells in these animals, whereas the proportions of classical activated (M1) monocytes/macrophages were significantly higher in T/M(Low) mice. In addition, interleukin-12 production was elevated in these tissues. Vascular endothelial growth factor-A expression and CD31(+) microvessels were increased in T/M(High) mice.

CONCLUSIONS

Collectively, these results demonstrate that an adequate amount of CCL2/MCP-1, together with the HSV-tk/GCV system, may induce T helper 1-polarized antitumor effects without inducing tumor angiogenesis in the microenvironment of intrahepatic HCC progression.

Injectable intratumoral depot of thermally responsive polypeptide-radionuclide conjugates delays tumor progression in a mouse model

This study evaluated a biodegradable drug delivery system for local cancer radiotherapy consisting of a thermally sensitive elastin-like polypeptide (ELP) conjugated to a therapeutic radionuclide. Two ELPs (49 kDa) were synthesized using genetic engineering to test the hypothesis that injectable biopolymeric depots can retain radionuclides locally and reduce the growth of tumors. A thermally sensitive polypeptide, ELP(1), was designed to spontaneously undergo a soluble-insoluble phase transition (forming viscous microparticles) between room temperature and body temperature upon intratumoral injection, while ELP(2) was designed to remain soluble upon injection and to serve as a negative control for the effect of aggregate assembly. After intratumoral administration of radionuclide conjugates of ELPs into implanted tumor xenografts in nude mice, their retention within the tumor, spatio-temporal distribution, and therapeutic effect were quantified. The residence time of the radionuclide-ELP(1) in the tumor was significantly longer than the thermally insensitive ELP(2) conjugate. In addition, the thermal transition of ELP(1) significantly protected the conjugated radionuclide from dehalogenation, whereas the conjugated radionuclide on ELP(2) was quickly eliminated from the tumor and cleaved from the biopolymer. These attributes of the thermally sensitive ELP(1) depot improved the antitumor efficacy of iodine-131 compared to the soluble ELP(2) control. This novel injectable and biodegradable depot has the potential to control advanced-stage cancers by reducing the bulk of inoperable tumors, enabling surgical removal of de-bulked tumors, and preserving healthy tissues.

Reduction of nontarget infection and systemic toxicity by targeted delivery of conditionally replicating viruses transported in mesenchymal stem cells

The fiber-modified adenoviral vector Delta-24-RGD (D24RGD) offers vast therapeutic potential. Direct injection of D24RGD has been used to successfully target ovarian tumors in mice. However, systemic toxicity, especially in the liver, profoundly limits the efficacy of direct viral vector delivery. Mesenchymal stem cells (MSC) have the ability to function as a vector for targeted gene therapy because of their preferential engraftment into solid tumors and participation in tumor stroma formation. We show that MSC-guided delivery of D24RGD is specific and efficient and reduces the overall systemic toxicity in mice to negligible levels compared with D24RGD alone. In our model, we found efficient targeted delivery of MSC-D24RGD to both breast and ovarian cell lines. Furthermore, immunohistochemical staining for adenoviral hexon protein confirmed negligible levels of systemic toxicity in mice that were administered MSC-D24RGD compared with those that were administered D24RGD. These data suggest that delivery of D24RGD through MSC not only increases the targeted delivery efficiency, but also reduces the systemic exposure of the virus, thereby reducing overall systemic toxicity to the host and ultimately enhancing its value as an anti-tumor therapeutic candidate.

Strategies to improve drug delivery across the blood-brain barrier

The blood-brain barrier (BBB), together with the blood-cerebrospinal-fluid barrier, protects and regulates the homeostasis of the brain. However, these barriers also limit the transport of small-molecule and, particularly, biopharmaceutical drugs such as proteins, genes and interference RNA to the brain, thereby limiting the treatment of many brain diseases. As a result, various drug delivery and targeting strategies are currently being developed to enhance the transport and distribution of drugs into the brain. In this review, we discuss briefly the biology and physiology of the BBB as the most important barrier for drug transport to the brain and, in more detail, the possibilities for delivering large-molecule drugs, particularly genes, by receptor-mediated nonviral drug delivery to the (human) brain. In addition, the systemic and intracellular pharmacokinetics of nonviral gene delivery, together with targeted brain imaging, are reviewed briefly.