Perlecan domain 1 recombinant proteoglycan augments BMP-2 activity and osteogenesis

ABSTRACT: BACKGROUND: Many growth factors, such as bone morphogenetic protein (BMP)-2, have been shown to interact with polymers of sulfated disacharrides known as heparan sulfate (HS) glycosaminoglycans (GAGs), which are found on matrix and cell-surface proteoglycans throughout the body. HS GAGs, and some more highly sulfated forms of chondroitin sulfate (CS), regulate cell function by serving as co-factors, or co-receptors, in GF interactions with their receptors, and HS or CS GAGs have been shown to be necessary for inducing signaling and GF activity, even in the osteogenic lineage. Unlike recombinant proteins, however, HS and CS GAGs are quite heterogenous due, in large part, to post-translational addition, then removal, of sulfate groups to various positions along the GAG polymer. We have, therefore, investigated whether it would be feasible to deliver a DNA pro-drug to generate a soluble HS/CS proteoglycan in situ that would augment the activity of growth-factors, including BMP-2, in vivo. RESULTS: Utilizing a purified recombinant human perlecan domain 1 (rhPln.D1) expressed from HEK 293 cells with HS and CS GAGs, tight binding and dose-enhancement of rhBMP-2 activity was demonstrated in vitro. In vitro, the expressed rhPln.D1 was characterized by modification with sulfated HS and CS GAGs. Dose-enhancement of rhBMP-2 by a pln.D1 expression plasmid delivered together as a lyophilized single-phase on a particulate tricalcium phosphate scaffold for 6 or more weeks generated up to 9 fold more bone volume de novo on the maxillary ridge in a rat model than in control sites without the pln.D1 plasmid. Using a significantly lower BMP-2 dose, this combination provided more than 5 times as much maxillary ridge augmentation and greater density than rhBMP-2 delivered on a collagen sponge (InFuse[trade mark sign]). CONCLUSIONS: A recombinant HS/CS PG interacted strongly and functionally with BMP-2 in binding and cell-based assays, and, in vivo, the pln.247 expression plasmid significantly improved the dose-effectiveness of BMP-2 osteogenic activity for in vivo de novo bone generation when delivered together on a scaffold as a single-phase. The use of HS/CS PGs may be useful to augment GF therapeutics, and a plasmid-based approach has been shown here to be highly effective.     

Infradian Variation of Rat Thymic and Splenic mRNA to Novikoff’s Hepatoma

During the immune response to rat tumor cells there is participation of the thymus and the spleen via the synthesis of antibodies and immune cellular elements. During this process different mRNAs of both organs are synthesized. Here is presented the infradian variation of mRNA synthesis of immunized rat thymus and spleen to Novikoff’s Hepatoma (NH) cells. These cells were maintained and transferred in ascitic manner in the peritoneal cavity of Sprague Dawley male rats standardized with 12 hours (h) of light and 12 h of darkness. Aliquots of 1 x 10 6 NH dead cells were innoculated intraperitoneally into rats after being exposed during 30 minutes to ultraviolet light and incubated at 37°C with 50 U of neuraminidase/ml during 70 minutes. Groups of 3 controls and 3 immunized rats were killed at the same circadian timepoint (10 a.m.) under anesthesia every 3 days during a span of 18 days. At each time spleens and thymus of each group were harvested and pooled in order to isolate their mRNA. Isolation of the rRNA and mRNA of control and immunized rats was performed by affinity chromatography employing oligothymidylic acid cellulose columns. Analysis of variance demonstrated a significant (p <0.03) higher synthesis of immune (i)mRNA of rat spleen, starting on 3 days after immunization with NH cells and reaching the higher levels on 6 and 18 days after immunization and lower levels on 9, 12, 15 days after immunization. Same effect is also observed in the synthesis of imRNA rat thymus 6 days after immunization, however, there was not difference with the intact rat thymus mRNA on 3, 9 and 12 days after immunization. Interestingly, there was observed an increased synthesis of intact rat thymus mRNA 15 days after inoculation. During this cyclic synthesis of thymic and spleenic imRNAs it seems that the spleen plays the role of a possible pacemaker of the coordinated immune response to NH cells.     

Tumor-Associated Antigen Peptides as Anti-Metastatic Vaccines

Cytotoxic T-lymphocytes (CTLs) kill abnormal cells. CTLs recognize major histocompatibility complex class I molecules in complex with peptides derived from relevant antigens. The identification of tumor associated antigen peptides enabled the design of anti-tumor and anti-metastatic vaccines in a murine lung carcinoma.