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Background T cell immunoglobulin mucin-3 (Tim-3) has been reported to participate in the regulation of immune response and the induction of allograft tolerance. However, the association between Tim-3 and renal allograft dysfunction is unclear. We studied the expression of cellular and soluble Tim-3 (sTim-3), soluble galectin-9 (sGal-9) and carcinoembryonic antigen-related cell adhesion molecule-1 (sCEACAM-1) in kidney transplantation recipients (KTRs) to explore their roles in allograft dysfunction. Methods 96 KTRs (53 with stable graft and 43 with graft dysfunction) and 30 healthy controls (HC) were enrolled. Among the KTRs, 55 used Tacrolimus (TAC) and 41 used Sirolimus (SRL). In the dysfunction group, 29 recipients have undergone graft biopsy and 14 were classified as biopsy-proven rejection (BPR). Cellular Tim-3 was determined by flow cytometry. sTim-3 was determined by ELISA. sGal-9 and sCEACAM-1 were determined by Bio-Plex® suspension array system. Results KTRs with renal dysfunction showed significantly higher levels of sTim-3 and sGal-9 but similar levels of cellular Tim-3 and sCEACAM-1 compared with stable recipients. Correlation analysis revealed that estimated glomerular filtration rate (eGFR) was negatively associated with sTim-3 and sGal-9. Both BPR and non-BPR groups showed comparable levels of Tim-3, Gal-9 and CEACAM-1. Moreover, SRL group showed significantly higher levels of sCEACAM-1 than TAC and HC groups. Conclusions sTim-3 and sGal-9 were promising biomarkers for allograft dysfunction, but unable to differentiate allograft rejection from other causes of renal dysfunction in KTRs. Moreover, long-term administration of sirolimus would up-regulate sCEACAM-1 level, while exert similar regulatory effects on Tim-3 and Gal-9 compared to tacrolimus.

Previous studies have documented the differences in expression of various genes associated with the process of osteogenesis in fusing and nonfusing cranial sutures, including growth factors, growth factor receptors, and extracellular matrix molecules. Most of these studies were performed in rats, and although the biology regulating cranial suture fusion in mice and rats is presumed to be similar, studies are needed to verify these expression patterns as mice become increasingly utilized for scientific inquiry into the molecular biology of suture fusion and patency. The purpose of this study was to determine the differences in expression of several genes known to be critical to osteoblast biology. Posterior frontal and sagittal suture complexes (including the associated dura mater, suture mesenchyme, and osteogenic fronts) were isolated from 5-, 15-, 25-, 35-, and 45-day-old male CD-1 mice (n = 8 per age; n = 40 total). Total cellular RNA was extracted and converted to cDNA. Quantitative real-time reverse transcriptase polymerase chain reaction was then performed for the following genes: transforming growth factor beta1 and beta3, fibroblast growth factor receptor 1, Runx2,Osteopontin, and Osteocalcin. Expression of all genes examined was increased significantly in the posterior frontal suture as compared with the sagittal suture. Peak expression for all genes was observed on day 25. These data demonstrate that the expression of osteogenic growth factors, growth factor receptors, transcription factors, and extracellular matrix molecules is increased in the fusing posterior frontal suture in mice.

Young children are capable of healing large calvarial defects, whereas adults lack this endogenous osseous tissue-engineering capacity. Despite the important clinical implications, little is known about the molecular and cell biology underlying this differential ability. Traditionally, guinea pig, rabbit, and rat models have been used to study the orchestration of calvarial healing. To harness the research potential of knockout and transgenic mice, the authors developed a mouse model for calvarial healing. Nonsuture-associated parietal defects 3, 4, and 5 mm in diameter were made in both juvenile (6-day-old, n = 15) and adult (60-day-old, n = 15) mice. Calvariae were harvested after 8 weeks and analyzed radiographically and histologically. Percentage of healing was quantified using Scion Image software analysis of calvarial radiographs. A significant difference in the ability to heal calvarial defects was seen between 6-day-old and 60-day-old mice when 3-, 4-, or 5-mm defects were created. The authors' analysis revealed that juvenile mice healed a significantly greater percentage of their calvarial defects than adult mice (juvenile mean percentage of healing: 3-mm defects, 59 percent; 4-mm defects, 65 percent; 5-mm defects, 44 percent; adult mean percentage of healing

In adults and children over two years of age, large cranial defects do not reossify successfully, posing a substantial biomedical burden. The osteogenic potential of bone marrow stromal (BMS) cells has been documented. This study investigates the in vivo osteogenic capability of adipose-derived adult stromal (ADAS) cells, BMS cells, calvarial-derived osteoblasts and dura mater cells to heal critical-size mouse calvarial defects. Implanted, apatite-coated, PLGA scaffolds seeded with ADAS or BMS cells produced significant intramembranous bone formation by 2 weeks and areas of complete bony bridging by 12 weeks as shown by X-ray analysis, histology and live micromolecular imaging. The contribution of implanted cells to new bone formation was 84-99% by chromosomal detection. These data show that ADAS cells heal critical-size skeletal defects without genetic manipulation or the addition of exogenous growth factors.

Retinoic acid has been shown to adversely affect craniofacial development. Cleft palate and craniosynostosis are two examples of craniofacial defects associated with prenatal exposure to this agent. Although the effects of retinoic acid on cephalic neural crest-derived tissues have previously been studied, the specific effects of retinoic acid on the cellular biology of osteoblasts remain unclear. The purpose of this study was to analyze in detail the effects of pharmacologic doses of retinoic acid on the differentiation and proliferation of osteoblasts derived from an intramembranous source. Primary rat calvarial osteoblasts were established in culture and treated with 1 or 10 μM all-trans-retinoic acid. Retinoic acid treatment markedly increased expression of osteopontin up to 48 h after stimulation. Consistent with this early stage of differentiation, both mRNA and protein analysis of FGF receptor isoforms demonstrated a switch in predominance from fibroblast growth factor receptor 2 (fgfr2) to fgfr1. Analysis of PCNA protein confirmed inhibition of proliferation by retinoic acid. To determine whether these alterations in osteoblast biology would lead to increased differentiation, we examined short term [alkaline phosphatase (AP) activity] and long term (von Kossa staining) surrogates of bone formation in vitro. These assays confirmed that retinoic acid increased osteogenesis, with a 4-fold increase in bone nodule formation in cells treated with 10 μM retinoic acid after 28 days. Overall, our results demonstrated that pharmacologic doses of all-trans-retinoic acid decreased osteoblast proliferation and increased differentiation, suggesting that retinoic acid may effect craniofacial development by pathologically enhancing osteogenesis. © 2005 Wiley-Liss, Inc.

BACKGROUND: Adipose-derived mesenchymal cells are multipotent progenitor cells derived from the vascular-stromal compartment of adipose tissue. Although we have recently shown that these cells, from both juvenile and adult animals, are capable of forming bone in vivo, a detailed examination of the differences in the biology of these two populations (and in particular their ability to form bone) has not been performed. METHODS: Adipose-derived mesenchymal cells were harvested from juvenile (6-day-old) and adult (60-day-old) mice. Differences in cellular attachment, proliferation, and proliferating cell nuclear antigen production were assessed. The ability of cells to undergo adipogenic differentiation was determined by Oil Red O staining. Early osteogenic differentiation was determined with alkaline phosphatase staining, and terminal differentiation with von Kossa staining as well as determination of extracellular matrix calcium content. All experiments were performed in triplicate. RESULTS: Greater attachment, proliferation, and proliferating cell nuclear antigen production were seen in juvenile as compared with adult adipose-derived mesenchymal cells. The juvenile cells underwent significantly greater adipogenic differentiation than did adult cells (p < 0.001). Interestingly, the adult cells were capable of robust early and terminal osteogenic differentiation, with levels of all three osteo-genic assays being similar to those seen in juvenile cells. Differences were not statistically significant. CONCLUSIONS: Although biologic differences exist between adipose-derived mesenchymal cells from juveniles and adults, the osteogenic capacity of these cells appears to be minimally affected by donor age. This suggests that these cells may be a particularly useful cellular resource in the design of cell-based therapies for skeletal regeneration in an aging population.

Reconstruction of craniofacial defects presents a substantial biomedical burden, and requires complex surgery. Interestingly, children after age 2 years and adults are unable to heal large skull defects. This nonhealing paradigm provides an excellent model system for craniofacial skeletal tissueengineering strategies. Previous studies have documented the in vivo osteogenic potential of adipose-derived stromal (ADS) cells and bone marrow-derived stromal (BMS) cells. This study investigates the ability to accelerate in vivo osteogenesis on ex vivo recombinant human bone morphogenetic protein 2 (BMP-2) and retinoic acid stimulation. Mouse osteoblasts, ADS cells, and BMS cells were seeded onto apatite-coated PLGA scaffolds, stimulated with rhBMP-2 and retinoic acid ex vivo for 4 weeks, and subsequently implanted into critically sized (4 mm) calvarial defects. Samples were harvested after 2, 4, 8, and 12 weeks. Areas of complete bony bridging were noted as early as 2 weeks in vivo; however, osteoclasts were attracted to the scaffold as identified by calcitonin receptor staining and tartrate-resistant acid phosphatase activity staining. Although the optimal method of in vitro osteogenic priming for mesenchymal cells remains unknown, these results provide evidence that BMP-2 and retinoic acid stimulation of multipotent cells ex vivo can subsequently induce significant quantities of bone formation within a short time period in vivo.

Introduction: Similarities between skeletal formation and repair have led to the theory that adult fracture repair may parallel development. We hypothesize that since the mandible is derived from cranial neural crest (CNC) and forms via intramembranous ossification, non-stabilized mandibular fractures will heal in a similar fashion. Methods: Non-stabilized osteotomies were created in the right hemi-mandible of adult male mice. Mandibles were harvested at 7, 14, 21, and 28 days and processed for histology. Ossification was assessed and the presence of cartilage determined using histology and in situ hybridization (ISH). To determine the embryologic origins of the regenerate, transgenic mice were generated where CNC cells express GFP constitutively under the Wnt-1 promoter. Fractures were created as described above and processed for frozen section. CNC cells were localized using immunohistochemistry (IHC) for GFP. Closed, non-stabilized tibial fractures were also performed to determine the presence, if any, of CNC-derived cells in appendicular skeletal fractures. Results: In contrast to non-stabilized fractures of the appendicular skeleton, mandibular fractures healed predominantly via intramembranous ossification, with minimal and delayed cartilage production seen via histology and collagen2 ISH. IHC for GFP revealed that the mandibular fracture callous and regenerate was comprised primarily of GFP+, CNC-derived cells. In contrast, the tibial fracture callous was devoid of any CNC-derived cells. Conclusions: These data suggest that mandibular fractures heal by recapitulating their developmental program. These findings have important implications for designing appropriate cell-based approaches to craniofacial regeneration.

Introduction: Data indicates that TGF-betas may play an important role in craniosynostosis. In a murine organ culture model, we previously demonstrated that blocking TGF-beta signaling leads to pathologic suture patency. In this study, we investigated both the osteogenic properties of TGF-beta1 and determined whether adenoviral overexpression of TGF-beta1 in a normally patent sagittal (SAG) suture would lead to pathologic suture fusion. Methods: Primary calvarial rat osteoblasts were treated with TGF-beta1 adenovirus or vehicle and cultured for four weeks. Expression of TGF-beta1 was confirmed using quantitative real-time PCR (QRT-PCR) and bone nodule formation assessed with von Kossa staining. The dura mater of 22 day CD-1 mouse calvarial explants were then transfected with adenovirus overexpressing TGF-beta1 or lacZ. SAG sutures were harvested weekly for four weeks and analyzed with H&E as well as beta-galactosidase staining. Results: QRT-PCR data confirmed the marked up regulation of TGF-beta1 mRNA in osteoblasts transfected with the TGF-beta1 overexpression adenovirus. TGF-beta1 adenoviral overexpression led to a 5-fold increase in bone nodule formation compared to untreated osteoblasts. Interestingly TGF-beta1 adenoviral transfection in the underlying dura mater did not lead to pathologic SAG suture fusion in any specimens. Conclusions: TGF-beta1 has potent osteogenic capabilities as demonstrated by a significant increase in bone nodule formation. Although blocking TGF-beta signaling prevents physiologic suture fusion, overexpression of TGF-beta in a normally patent cranial suture does not lead to pathologic craniosynostosis. TGF-beta is potentially necessary but not sufficient in the mechanism of programmed cranial suture fusion.

Introduction: Although a wealth of data demonstrates that regionally patterned dura mater regulates suture fusion or patency, the onset and extent of this patterning remains unknown. In this study we used microarray analyses as a starting point to investigate the differences in suture-specific dura mater from the mouse posterior frontal (PF) and sagittal (SAG) suture. Methods: Regional dura mater was harvested from the PF and SAsutures of 15 and 25 day male CD-1 mice (n = 40 each) and RNA isolated. Microarray analyses were performed using 42,000 element cDNA arrays. Slug was also evaluated in non-suture dura from young (5-day-old) and adult (60-day-old) animals. Investigation into regulation of novel genes, such as the transcription factor Slug, were carried out using rat calvarial osteoblasts stimulated with FGF-2, TGF-beta 1, and BMP2 and 4. Results: Microarray analyses demonstrated differential regulation of over 220 genes in the PF suture at d15, and over 280 genes at d25. Although the number of genes down-regulated was similar, there was a dramatic increase in the number of genes up-regulated in the PF suture at d25 vs. d15 (137 vs. 43). Distinct patterns of expression were seen for several groups of genes, including cytokines (FGF and FGF receptors) and extra-cellular matrix molecules (Col-1, osteopontin, osteocalcin). Several novel genes were identified, including the transcription factor Slug. QRT-PCR verified a > 4-fold increase in Slug mRNA in PF vs. SAG dura, and a > 3-fold increase in young vs. adult dura mater. Functional studies demonstrated a selective inhibition of Slug mRNA in osteoblasts by FGF-2 and TGF-beta 1, but not the BMPs, up to 24 hrs post stimulation (see figure). Conclusions: Our data demonstrate genomic patterning of regional dura mater as early as ten days prior to PF suture fusion. In addition we show that the transcription factor Slug, an evolutionarily conserved gene involved in epithelial-to-mesenchymal cell transitions, is regulated by two growth factors known to be expressed in dura mater.