Cartilaginous implants for potential use in reconstructive or orthopedic surgery were created using chondrocytes grown on synthetic, biodegradable polymer scaffolds. Chondrocytes isolated from bovine or human articular or costal cartilage were cultured on fibrous polyglycolic acid (PGA) and porous poly(L)lactic acid (PLLA) and used in parallel in vitro and in vivo studies. Samples were taken at timed intervals for assessment of cell number and cartilage matrix (sulfated glycosaminoglycan [S-GAG], collagen). The chondrocytes secreted cartilage matrix to fill the void spaces in the polymer scaffolds that were simultaneously biodegrading. In vitro, chondrocytes grown on PGA for 6 weeks reached a cell density of 5.2 x 10(7) cells/g, which was 8.3-fold higher than at day 1, and equalled the cellularity of normal bovine articular cartilage. In vitro, the cell growth rate was approximately twice as high on PGA as it was on PLLA; cells grown on PGA produced S-GAG at a high steady rate, while cells grown on PLLA produced only minimal amounts of S-GAG. These differences could be attributed to polymer geometry and biodegradation rate. In vivo, chondrocytes grown on both PGA and PLLA for 1-6 months maintained the three-dimensional (3-D) shapes of the original polymer scaffolds, appeared glistening white macroscopically, contained S-GAG and type II collagen, and closely resembled cartilage histologically. These studies demonstrate the feasibility of culturing isolated chondrocytes on biodegradable polymer scaffolds to regenerate 3-D neocartilage.

Prostate-specific membrane antigen (PSMA) is expressed in normal human prostate epithelium and is highly upregulated in prostate cancer. We previously reported a series of novel small molecule inhibitors targeting PSMA. Two compounds, MIP-1072, (S)-2-(3-((S)-1-carboxy-5-(4–iodobenzylamino)pentyl)ureido)pentanedioic acid and MIP-1095, (S)-2-(3-((S)-1-carboxy-5-(3-(4-iodophenyl)ureido)pentyl)ureido)pentanedioic acid, were selected for further evaluation. MIP-1072 and MIP-1095 potently inhibited the glutamate carboxypeptidase activity of PSMA (Ki = 4.6 ± 1.6 and 0.24 ± 0.14 nM, respectively), and when radiolabeled with 123I exhibited high affinity for PSMA on human prostate cancer LNCaP cells (Kd = 3.8 ± 1.3 and 0.81 ± 0.39 nM, respectively). The association of [123I]MIP-1072 and [123I]MIP-1095 with PSMA was specific; there was no binding to human prostate cancer PC3 cells, which lack PSMA, and binding was abolished by co-incubation with a structurally unrelated NAALADase inhibitor, 2-(phosphonomethyl)pentanedioic acid (PMPA). [123I]MIP-1072 and [123I]MIP-1095 internalized into LNCaP cells at 37 °C. Tissue distribution studies in mice demonstrated 17.3 ± 6.3 (at 1 hr) and 34.3 ± 12.7 (at 4 hr) % injected dose per gram of tissue, for [123I]MIP-1072 and [123I]MIP-1095, respectively. [123I]MIP-1095 exhibited greater tumor uptake but slower washout from blood and non-target tissues compared to [123I]MIP-1072. Specific binding to PSMA in vivo was demonstrated by competition with PMPA in LNCaP xenografts, and the absence of uptake in PC3 xenografts. The uptake of [123I]MIP-1072 and [123I]MIP-1095 in tumor bearing mice was corroborated by SPECT/CT imaging. PSMA-specific radiopharmaceuticals should provide a novel molecular targeting option for the detection and staging of prostate cancer.

Iron chelators are pluripotent neuronal antiapoptotic agents that have been shown to enhance metabolic recovery in cerebral ischemia models. The precise mechanism(s) by which these agents exert their effects remains unclear. Recent studies have demonstrated that iron chelators activate a hypoxia signal transduction pathway in non-neuronal cells that culminates in the stabilization of the transcriptional activator hypoxia-inducible factor-1 (HIF-1) and increased expression of gene products that mediate hypoxic adaptation. We examined the hypothesis that iron chelators prevent oxidative stress-induced death in cortical neuronal cultures by inducing expression of HIF-1 and its target genes. We report that the structurally distinct iron chelators deferoxamine mesylate and mimosine prevent apoptosis induced by glutathione depletion and oxidative stress in embryonic cortical neuronal cultures. The protective effects of iron chelators are correlated with their ability to enhance DNA binding of HIF-1 and activating transcription factor 1(ATF-1)/cAMP response element-binding protein (CREB) to the hypoxia response element in cortical cultures and the H19-7 hippocampal neuronal cell line. We show that mRNA, protein, and/or activity levels for genes whose expression is known to be regulated by HIF-1, including glycolytic enzymes, p21(waf1/cip1), and erythropoietin, are increased in cortical neuronal cultures in response to iron chelator treatment. Finally, we demonstrate that cobalt chloride, which also activates HIF-1 and ATF-1/CREB in cortical cultures, also prevents oxidative stress-induced death in these cells. Altogether, these results suggest that iron chelators exert their neuroprotective effects, in part, by activating a signal transduction pathway leading to increased expression of genes known to compensate for hypoxic or oxidative stress.

Cartilage implants which could potentially be used to resurface damaged joints were created using rabbit articular chondrocytes and synthetic, biodegradable polymer scaffolds. Cells were serially passaged and then cultured in vitro on fibrous polyglycolic acid (PGA) scaffolds. Cell-PGA constructs were implanted in vivo as allografts to repair 3-mm diameter, full thickness defects in the knee joints of adult rabbits, and cartilage repair was assessed histologically over 6 months. In vitro, chondrocytes proliferated on PGA and regenerated cartilaginous matrix. Collagen and glycosaminoglycan (GAG) represented 20 to 8% of the implant dry weight (dw), respectively, at the time of in vivo implantation; the remainder was PGA and unspecified components. Implants based on passaged chondrocytes had 1.7-times as much GAG and 2.6-times as much collagen as those based on primary chondrocytes. In vivo, cartilaginous repair tissue was observed after implantation of PGA both with and without cultured chondrocytes. Six month repair was qualitatively better for cell-PGA allografts than for PGA alone, with respect to: 1) surface smoothness, 2) columnar alignment of chondrocytes, 3) spatially uniform GAG distribution, 4) reconstitution of the subchondral plate, and 5) bonding of the repair tissue to the underlying bone. These pilot studies demonstrate that it is feasible to use cell-polymer allografts for joint resurfacing in vivo.

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