NaCl-aided Hoechst 33258 staining method for DNA quantification and its application

Spheroids of Endothelial Cells and Vascular Smooth Muscle Cells Promote Cell Migration in Hyaluronic Acid and Fibrinogen Composite Hydrogels

Cell migration plays a pivotal role in many pathological and physiological processes. So far, most of the studies have been focused on 2-dimensional cell adhesion and migration. Herein, the migration behaviors of cell spheroids in 3D hydrogels obtained by polymerization of methacrylated hyaluronic acid (HA-MA) and fibrinogen (Fg) with different ratios were studied. The Fg could be released to the medium gradually along with time prolongation, achieving the dynamic change of hydrogel structures and properties. Three types of cell spheroids, i.e., endothelial cell (EC), smooth muscle cell (SMC), and EC-SMC spheroids, were prepared with 10,000 cells in each, whose diameters were about 343, 108, and 224 μm, respectively. The composite hydrogels with an intermediate ratio of Fg allowed the fastest 3D migration of cell spheroids. The ECs-SMCs migrated longest up to 3200 μm at day 14, whereas the SMC spheroids migrated slowest with a distance of only ~400 μm at the same period of time. The addition of free RGD or anti-CD44 could significantly reduce the migration distance, revealing that the cell-substrate interactions take the major roles and the migration is mesenchymal dependent. Moreover, addition of anti-N-cadherin and MMP inhibitors also slowed down the migration rate, demonstrating that the degradation of hydrogels and cell-cell interactions are also largely involved in the cell migration. RT-PCR measurement showed that expression of genes related to cell adhesion and antiapoptosis, and angiogenesis was all upregulated in the EC-SMC spheroids than single EC or SMC spheroids, suggesting that the use of composite cell spheroids is more promising to promote cell-substrate interactions and maintenance of cell functions.

Improved mesenchymal stem cells attachment and in vitro cartilage tissue formation on chitosan-modified poly(L-lactide-co-epsilon-caprolactone) scaffold

Considering the load-bearing physiological requirement of articular cartilage, scaffold for cartilage tissue engineering should exhibit appropriate mechanical responses as natural cartilage undergoing temporary deformation on loading with little structural collapse, and recovering to the original geometry on unloading. A porous elastomeric poly l-lactide-co-ɛ-caprolactone (PLCL) was generated and crosslinked at the surface to chitosan to improve its wettability. Human bone marrow derived mesenchymal stem cells (MSC) attachment, morphological change, proliferation and in vitro cartilage tissue formation on the chitosan-modified PLCL scaffold were compared with the unmodified PLCL scaffold. Chitosan surface promoted more consistent and even distribution of the seeded MSC within the scaffold. MSC rapidly adopted a distinct spread-up morphology on attachment on the chitosan-modified PLCL scaffold with the formation of F-actin stress fiber which proceeded to cell aggregation; an event much delayed in the unmodified PLCL. Enhanced cartilage formation on the chitosan-modified PLCL was shown by real-time PCR analysis, histological and immunochemistry staining and biochemical assays of the cartilage extracellular matrix components. The Young's modulus of the derived cartilage tissues on the chitosan-modified PLCL scaffold was significantly increased and doubled that of the unmodified PLCL. Our results show that chitosan modification of the PLCL scaffold improved the cell compatibility of the PLCL scaffold without significant alteration of the physical elastomeric properties of PLCL and resulted in the formation of cartilage tissue of better quality.

Cartilaginous ECM component-modification of the micro-bead culture system for chondrogenic differentiation of mesenchymal stem cells

In this study a 3-D alginate microbead platform was coated with cartilaginous extracellular matrix (ECM) components to emulate chondrogenic microenvironment in vivo for the differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). BMSCs were seeded onto the microbead surface and the effect of the modified microbead on BMSC adhesion, proliferation and chondrogenic differentiation was studied, and compared to chondrogenesis in conventional pellet culture. Our results indicated that microbead system promoted BMSC proliferation and protein deposition resulting in the formation of bigger aggregates compared to conventional pellet culture. Analysis of the aggregates indicated that chondroitin sulfate (CS)- and Col2-coated microbeads enhanced the chondrogenic differentiation of hBMSCs, with increasing formation of glycosaminoglycan (GAG) and collagen II deposition in histology, immunohistochemistry and real time PCR analysis. In addition, Col2-coated microbeads resulted in hypertrophic maturation of the differentiated chondrocytes, similar to conventional pellet culture, while CS-coated microbeads were able to retain the pre-hypertrophy state of the differentiated cells. Our result suggested that provision of suitable cartilaginous microenvironment in a 3-D system can promote the chondrogenic differentiation of BMSC and influence the phenotype of resulting chondrocytes. Our microbead system provides an easy method of processing a 3-D alginate system that allows the possibility of scaling up chondrogenic pellet production for clinical application, while the modifiable microbeads also provide an adjustable 3-D platform for the study of co-interaction of ECM and differentiation factors during the stem cell differentiation.

Androgen receptor as a licensing factor for DNA replication in androgen-sensitive prostate cancer cells

Androgen receptor (AR) protein expression and function are critical for survival and proliferation of androgen-sensitive (AS) prostate cancer cells. Besides its ability to function as a transcription factor, experimental observations suggest that AR becomes a licensing factor for DNA replication in AS prostate cancer cells and thus must be degraded during each cell cycle in these cells to allow reinitiation of DNA replication in the next cell cycle. This possibility was tested by using the AS human prostate cancer cell lines, LNCaP, CWR22Rv1, and LAPC-4. These studies demonstrated that AR levels fluctuate both within and between various phases of the cell cycle in each of these AS lines. Consistent with its licensing ability, AR is degraded during mitosis via a proteasome-dependent pathway in these AS prostate cancer cells. In contrast, proteasome-dependent degradation of AR during mitosis is not observed in AR-expressing but androgen-insensitive human prostate stromal cells, in which AR does not function as a licensing factor for DNA replication. To evaluate mitotic degradation of AR in vivo, the same series of human AS prostate cancers growing as xenografts in nude mice and malignant tissues obtained directly from prostate cancer patients were evaluated by dual Ki-67 and AR immunohistochemistry for AR expression in mitosis. These results document that AR is also down-regulated during mitosis in vivo. Thus, AS prostate cancer cells do not express AR protein during mitosis, either in vitro or in vivo, consistent with AR functioning as a licensing factor for DNA replication in AS prostate cancer cells.

Increased DNA methylation in the HoxA5 promoter region correlates with decreased expression of the gene during tumor promotion

Promoter-region DNA methylation inhibits transcription. A two-stage SENCAR (sensitive to mouse carcinogenesis) mouse skin carcinogenicity model was used to examine gene-specific changes in methylation during skin tumor promotion. Analysis was performed on 7,12-dimethylbenz[a]anthracene (DMBA)-initiated skin promoted with 9, 18, 27, or 36 mg cigarette smoke condensate (CSC) for 9 wk, or 27 mg CSC for 9 wk and sacrificed 6 wk afterwards (recovery group). Additionally, tumors arising following promotion with 27 mg CSC for 29 wk were assessed. Gene array analysis identified differentially expressed genes. Expression of HoxA5, a tumor suppressor gene, was decreased following 9 wk of treatment with 27 mg CSC, and returned to control levels during recovery. HoxA5 promoter methylation was measured with the enzymatic regional methylation assay (ERMA). DNA was bisulfite-modified, PCR-amplified with primers containing dam sites, incubated with [14C-methyl] S-adenosyl-L-methionine (SAM) and dam methyltransferase for DNA quantification, then incubated with [3H-methyl] SAM and SssI methylase to quantify methylation status. Higher 3H/14C ratios indicate increased methylation. The 3H/14C ratios of animals promoted with 27 or 36 mg CSC (48.2 +/- 6.9 and 24.2 +/- 6.1, respectively) were higher than the control or recovery group ratios (12.3 +/- 0.1 and 12.6 +/- 0.3, respectively); sequence analysis supported these findings. Increased methylation of p16 or O6 methylguanine methyltranferase (MGMT) was detected in 4/8 (50%) of the tumor samples from mice promoted with 27 mg CSC. These data suggest that increased DNA methylation contributes to the downregulation of HoxA5, and combined with hypermethylation of p16 or MGMT, this might facilitate the clonal expansion of increasingly aberrant cells during promotion.

Surface modification to improve in vitro attachment and proliferation of human urinary tract cells

OBJECTIVE

To evaluate the attachment and proliferation of cultured human urinary tract cells to culture plates surface-modified by photochemical immobilization of extracellular matrix (ECM) proteins.

MATERIALS AND METHODS

Human uroepithelial (UEC) and smooth muscle (SMC) cells were harvested from ureter and expanded in culture; 24-well culture plates surface-modified by photochemical covalent immobilization of ECM proteins were then seeded with UEC or SMC. To characterize cellular attachment, cells were incubated on surface-modified plates for 30 and 90 min. For proliferation assays the cells were incubated for 3-12 days. Standard tissue culture plates with no surface modification and sham-modified plates served as controls. Differential attachment and proliferation on the various surfaces were assessed using analysis of variance with Fisher's posthoc test for multiple comparisons.

RESULTS

Attachment at 30 and 90 min of both UEC and SMC on plates surface-modified with ECM proteins was significantly greater than in control plates. Surface-modification with collagen resulted in significantly greater cellular attachment than with either laminin or fibronectin. UEC proliferation was also significantly greater than in control plates by surface-modification with collagen and fibronectin, but not with laminin. SMC proliferation was significantly better after surface modification than on sham- modified plates, but was no better than standard plates.

CONCLUSIONS

Covalent photochemical immobilization of ECM proteins to potential growth surfaces enhances the attachment of cultured UEC and SMC and the proliferation of UEC. This technique might be useful in modifying surface properties of synthetic polymer-based materials in a controlled and defined manner, giving them the capacity to promote and sustain the growth of urinary tract cells. This may lead to development of alternative methods of tissue engineering in the urinary tract.

Lindane does not alter the estrogen receptor or the estrogen-dependent induction of progesterone receptors in sexually immature or ovariectomized adult rats

Lindane, gamma-1,2,3,4,5,6-hexachlorocyclohexane (gamma-HCH), has been shown to disrupt reproductive function in mammals. Many of these adverse effects on female reproduction such as alterations in sexual receptivity, disrupted ovarian cyclicity, reduction in uterine weight and termination of pregnancy are thought to be due to altered ovarian hormone secretions and/or an impaired response to circulating estrogen. It has been suggested that gamma-HCH may block the response of estrogen-dependent tissues to estradiol via an interaction with the estrogen receptor. To test this hypothesis, estrogen (ER) and progesterone (PR) receptor affinity and number were evaluated in sexually immature, 17 beta-estradiol-3-benzoate (EB)-primed Long Evans female rats following exposure to vehicle or gamma-HCH (40 mg/kg) for 7 days (Study 1) and in adult, ovariectomized EB-primed Long-Evans rats following gavage with vehicle or gamma-HCH (0, 10, 20, or 40 mg/kg) for 5 days (Study 2). Chlordecone (kepone; 40 mg/kg; i.p.) was used in Study 2 as a positive control for the alteration of the estrogen-induction of PR in the pituitary. Neither gamma-HCH nor chlordecone altered serum estradiol concentrations. gamma-HCH did not change the ER number (1, 24, or 30 h after EB) or the estrogen-dependent induction of PR (24 or 48 h after EB) in the hypothalamus (HYP), pituitary, or uterus. These data indicate that the effects of gamma-HCH on the female reproductive system do not involve an alteration in the ER and that heterogeneity exists between target tissues in their response to xenobiotics.

Decrease of DNA per cell during development of the lens in chickens

Developmental changes in the amount and conformation of DNA in chicken lens were studied. For this, DNA in situ in lens fiber cell nuclei of chickens was examined by microfluorometry with Hoechst 33258 (Hoe) fluorochrome. On 1 M NaCl-aided Hoe staining, by which the amount of DNA can be determined accurately, the fluorescence intensity of lens fiber cells was found to decrease with no change in that of the lens epithelial cells during development. On the contrary, on normal NaCl-free Hoe staining the fluorescence intensity of the lens cells was found to increase gradually during development. These results suggest that during development the amount of DNA in lens fiber cells decreases in association with some change in its conformation.