Characterization of corneal endothelium cell cultured on microporous membrane filters

Bovine posterior limbus: an evaluation of an alternative source for corneal endothelial and trabecular meshwork stem/progenitor cells

A growing body of evidence has revealed that stem-like cells in the posterior limbus of the eye between the corneal endothelium (CE) and trabecular meshwork (TM) may be able to rejuvenate these tissues in disease. However, these cells have not been clearly defined and we have named them PET cells (progenitor cells of the endothelium and trabeculum). A good and inexpensive animal model for PET cells is lacking, so we investigated bovine eyes as an effective large tissue source. We showed the presence of stem/progenitor cells in the bovine CE, transition zone, and TM in situ. Floating spheres cultured from the CE and TM showed similar stem cell marker expression patterns. Both the CE and TM spheres were bipotent and highly proliferative, but with limited secondary sphere-forming capability. They were highly prone to differentiate back into the cell type of their tissue of origin. It is speculated that the PET cells become more tissue-specific as they migrate away from their niche. Here, we showed that PET cells are present in the posterior limbus of bovine eyes and that they can be successfully cultured and expanded. PET cells represent an attractive target for developing new treatments to regenerate both the CE and TM, thereby reducing the requirement for donor tissue for corneal transplant and invasive treatments for glaucomatous patients.

Ocular novel drug delivery: impacts of membranes and barriers

BACKGROUND

Ocular drug delivery is an extremely challenging area due to its restrictive barrier functionalities.

OBJECTIVE

Drug transport via corneal/non-corneal routes involves several intricate biological processes such as drug penetration across the ocular barriers and transfer to the anterior or posterior chambers, thus the influence of these processes on the pharmacotherapy of the eye should be fully addressed.

METHODS

To pursue the impacts of such impediments in novel drug therapy, recent publications were reviewed regarding advanced strategies such as nanomedicines.

CONCLUSION

The ocular barriers are highly specialized and selectively control the inward/outward traverse of compounds, hence a better understanding of these biological obstacles would provide a platform to advance ophthalmic drug therapy towards specified delivery/targeting with minimal adverse consequences.

Modulation of tight junction properties relevant to fluid transport across rabbit corneal endothelium

Paracellular junctions could play an important role in corneal endothelial fluid transport. In this study we explored the effects of different reagents on the tight junctional barrier by assessing the translayer specific electrical resistance (TER) across rabbit corneal endothelial preparations and cultured rabbit corneal endothelial cells' (CRCEC) monolayers, the paracellular permeability (Papp) for fluorescein isothiocyanate (FITC) dextrans across CRCEC, and fluid transport across de-epithelialized rabbit corneal endothelial preparations. Palmitoyl carnitine (PC), poly-L-lysine (PLL), adenosine triphosphate (ATP), and dibutyryl adenosine 3',5'-cyclic monophosphate (dB-cAMP) were used to modulate corneal endothelial fluid transport and tight junctions (TJs). After seeding, the TER across CRCEC reached maximal values (29.2+/-1.0 Omega cm2) only after the 10th day. PC (0.1 mM) caused decreases both in TER (by 40%) and fluid transport (swelling rate: 18.5+/-0.3 microm/h), and an increase in Papp. PLL resulted in increased TER rose and Papp but decreased fluid transport (swelling rate: 10+/-0.3 microm/h). dB-cAMP (0.1 mM) and ATP (0.1 mM) decreased TER by 16% and 6%, increased Papp slightly, and stimulated fluid transport; the rates of de-swelling (in microm/h) were -5.4+/-0.3 and -12.1+/-0.4, respectively. PC might cause the junctions to open up unspecifically and thus increase passive leak. PLL is a known junctional charge modifier that may be adding steric hindrance to the tight junctions. The results with dB-cAMP and ATP are consistent with fluid transport via the paracellular route.

Cytokines, nitric oxide, and cGMP modulate the permeability of an in vitro model of the human blood-brain barrier

The endothelial cells (EC) of the microvasculature in the brain form the anatomical basis of the blood-brain barrier (BBB). In the present study, the effects of agents that modify the permeability of a well-established in vitro model of the human BBB were studied. The monolayers formed by confluent human brain microvessel endothelial cell (HBMEC) cultures are impermeable to the macromolecule tracer horseradish peroxidase (HRP) and have high electrical resistance. Exposure of HBMEC to various cytokines including TNF-alpha, IL-1beta, interferon gamma (IFN-gamma), or lipopolysaccharide (LPS) decreased transendothelial electrical resistance (TEER) mainly by increasing the permeability of the tight junctions. Primary cultures of HBMEC express endothelial nitric oxide synthase (eNOS) and produce low levels of NO. Treatment with the NO donors sodium nitroprusside (SNP) and DETA NONOate or the cGMP agonist 8-Br-cGMP significantly increased monolayer resistance. Conversely, inhibition of soluble guanylyl cyclase with ODQ rapidly decreased the resistance, and pretreatment of HBMEC with Rp-8-CPT-cGMPS, an inhibitor of cGMP-dependent protein kinase, partially prevented the 8-Br-cGMP-induced increase in resistance. Furthermore, NO donors and 8-Br-cGMP could also reverse the increased permeability of the monolayers induced by IL-1beta, IFN-gamma, and LPS. These results indicate that NO can decrease the permeability of the human BBB through a mechanism at least partly dependent on cGMP production and cGMP-dependent protein kinase activation.

Effect of intraocular irrigating solutions on the viability of cultured retinal vascular endothelial cells

PURPOSE

To compare the abilities of balanced salt solution, BSS Plus and Hartmann's lactated Ringer's (HLR) solution to maintain the viability of retinal vascular endothelial cells (RVEC) in vitro.

METHODS

Cultured retinal vascular endothelial cells were suspended in each irrigating solution for four hours. Viability was determined by trypan blue exclusion at 30 minute intervals. Regression analysis was used to determine the rate of viability loss. Additional studies were performed to determine the effectiveness of lactate in maintaining cell viability.

RESULTS

Retinal vascular endothelial cells lost viability at a greater rate (p < 0.001) in BSS (8.7%/hr) compared with BSS Plus (3.3%/hr). Cells in Hartmann's lactated Ringer's lost viability at a significantly lower rate (4.4%/hr) than retinal vascular endothelial cells in lactate-free Hartmann's lactated Ringer's solution (8.4%/hr). Lactate was as effective as glucose in preserving RVEC viability. By comparison, the viability of corneal endothelial cells was not effectively maintained by lactate. For these cells, BSS Plus was clearly superior to Hartmann's lactated Ringer's solution in maintaining viability.

CONCLUSIONS

BSS Plus and Hartmann's lactated Ringer's solution are both superior to balanced salt solution in maintaining retinal vascular endothelial cell viability. For retinal vascular endothelial cells, Hartmann's lactated Ringer's solution preserves cell viability as well as BSS Plus, since the retinal vascular endothelial cells, unlike corneal endothelial cells, can apparently utilize lactate as an energy source.

The influence of retinoic acid on growth and morphology of rat exorbital lacrimal gland acinar cells in culture

The lacrimal gland transports and metabolizes retinoids and may require vitamin A for normal function. To study effects of retinoic acid on morphology and growth of the lacrimal gland, rat lacrimal acinar cells were cultured in medium with serum or in serum-free medium in the presence or absence of retinoic acid. In the presence of serum, the acinar cells have a somewhat fibroblastic morphology and form confluent layers. Addition of retinoic acid to these cultures causes formation of tubule-like structures. Retinoic acid inhibits the growth of lacrimal cells in medium with serum and the cells do not reach confluence; however, the labeling of the cells with bromodeoxyuridine is not affected by retinoic acid. In serum-free medium the growth of acinar cells is reduced, but their morphology is epithelial and structures resembling secretory domes are present. Retinoic acid causes a further reduction in growth, domes are absent, and cell spreading and enlargement occurs. The effects of retinoic acid on growth and morphology of lacrimal acinar cells in culture are complex and the relevance of these observations to lacrimal function in vivo is unclear; the study demonstrates, however, that these cells are responsive to retinoic acid.