[Pilot study of a new matrix therapy agent (RGTA OTR4120) in treatment-resistant corneal ulcers and corneal dystrophy]. / Etude pilote d'un nouvel agent de thérapie matricielle (RGTA OTR4120) dans les ulcères de cornée et les dystrophies cornéennes rebelles.

AIMS: This study's objective was to evaluate the tolerance and safety of a new ophthalmic solution based on ReGeneraTing agent (RGTA) technology in a pilot noncontrolled exploration on compassion use for corneal ulcers and severe chronic dystrophies resistant to the usual treatments. RATIONALE: RGTAs are large biopolymers engineered to replace heparan sulfates specifically bound to matrix proteins and growth factors destroyed after a lesion has occurred. The RGTA-bound proteins are protected from proteolysis and this allows the extracellular matrix microenvironment to restore its original proper organization. The initial endogenous signals needed for tissues to regenerate are back on the restored matrix. They are expected to trigger the natural onset of events, signaling cells to migrate and multiply with the cascades and equilibrium found in tissue homeostasis. RGTA-induced matrix therapy is a possible alternative to cell or gene therapy in regenerative medicine. In a rabbit preclinical model of alkali-induced severe corneal ulcers, a single instillation of RGTA ophthalmic solution was found sufficient to enhance speed and quality of healing, restoring an almost normal corneal histology after only 1 week. These data prompted us to initiate this study. PATIENTS AND METHODS: Eleven eyes from ten patients were included in this study. All patients had severe dystrophic cornea or painful corneal ulcers rated over 50 on the VAS pain scale ranging from 0 to 100 and had undergone unsuccessful treatments. The RGTA ophthalmic solution was administered by the investigator during each weekly consultation as a single drop over 1 month. Tolerance and efficacy were judged on subjective criteria based on pain evaluation and functional inconvenience as well as on objective clinical criteria through a complete ophthalmic examination at days 3, 7, 14, 21, 28 and after 2 and 3 months from the beginning of the treatment. RESULTS: The study was conducted to completion for all patients included at the beginning. Tolerance was excellent both locally and generally: no uneasiness during instillation, no worsening of the initial pathology, no occurrence of ocular inflammation or increase in ocular pressure, and no general side effects were observed. In addition, we observed a noticeable analgesic effect, increasing with time and instillations, but pain reappeared in the majority of cases as treatment ended. The mean visual analog scale pain score was 72.73 +/- 7.86, it decreased significantly with the first drops of treatment. After 1 month, the mean visual analog scale pain score was 32+/-15.49, then it increased after the end of the treatment, confirming the link between the effects observed and the treatment. Efficacy on keratitis was moderate but with an overall tendency toward improvement. The initial Oxford Score was 3.37 +/- 1.06. After 1 month, it decreased significantly to 1.57 +/- 0.97 and then it rose again after the end of the treatment. As for corneal ulcers, of the five cases included, four healed during the protocol. Two reversed when the treatment stopped, two healed without reversion at the last follow-up visit. The last case was characterized by stem cell deficiency and no improvement was noted. It is important to keep in mind that these ulcers were all resistant to usual therapies. CONCLUSION: This RGTA ophthalmic solution is the first matrix therapy product in ophthalmology. The RGTA OTR4120 was used in treating chronic and severe corneal dystrophies as well as corneal ulcers resistant to usual treatments. It was very well tolerated with no side effects. It significantly reduced pain and favored corneal healing in almost all corneal ulcers. Weekly instillation of a single drop seems insufficient and these very promising data need to be confirmed on a larger population in a controlled trial with more adapted dosages. Based on these preliminary data, a RGTA-based matrix therapy product may be a very innovative solution to unresolved pain and corneal surface healing problems.

Cardiovascular and pulmonary response to oral administration of ATP in rabbits.

Extracellular purines such as ATP and adenosine participate in the regulation of cardiovascular and respiratory functions through specific P1 and P2 purine receptors. These properties have mainly been described after intravenous infusion. Experiments reported herein were designed to explore the possible effect of oral ATP administration (3 or 20 mg. kg(-1). day(-1)) on vascular, cardiac, and pulmonary functions in rabbits. Whereas a unique oral dose of ATP has no effect, chronic supplementation during 14 days reduces peripheral vascular resistance, pulmonary resistance, and respiratory frequency and increases arterial PO(2). No effect on central blood pressure and heart rate is observed, but an increase of the left ventricular work index is noticed subsequent to the diminution of vascular resistance. Rather similar cardiovascular modifications are observed in rabbits given 20 mg. kg(-1). day(-1) adenosine for 14 days but without variation of respiratory parameters. These original effects of repeated oral treatment with ATP may result from an adaptive metabolic response to nucleoside supplementation that might affect the turnover of extracellular purines leading to P1- and/or P2-receptor activation.

Chronic oral administration of ATP modulates nucleoside transport and purine metabolism in rats.

The effect of repeated oral administration of ATP on purine transport and metabolism was investigated in rats. An increased ability of the gut to capture intraluminal purine nucleosides and to export ATP and nucleosides toward portal bloodstream was observed in rats after 30 days of treatment with 5 mg/kg/day ATP. This was accompanied in erythrocytes by an increased transport of adenosine rapidly transformed into ATP, which in turn was exported toward extracellular fluid. However, these metabolic changes were associated with a paradoxical and progressive diminution of plasma ATP level below that found in control rats and that was not strictly dependent on the ATP dose administered, whereas plasma adenosine concentration remained unchanged. This diminution likely resulted from an increased ectonucleotidase activity, suggesting that the chronic administration of ATP seems to induce a progressive adaptation of purine metabolism. This adaptive response to free purine supplementation affects both intracellular metabolism and purine exchange between intracellular and extracellular compartments. This modification of free purine turnover and delivery may affect physiological parameters under the control of P(1) and P(2) purinoceptors described in different experimental models.

CD3 activation induces concentrative nucleoside transport in human T lymphocytes.

Nucleoside transport, assessed by measuring deoxythymidine influx, was investigated in normal and CD3-activated human peripheral blood mononuclear cells (PBMC) and in the CEM cell line. On both cell types, an equilibrative nitrobenzylmercaptopurine (NBMPR)-sensitive (es) transporter encoded by the hENT(1) gene was identified on resting cells, although the expression level was about 20-fold higher on CEM cells than on resting peripheral T lymphocytes. After stimulation with anti-CD3, a strong increase of nucleoside transport was observed in PBMC accompanied by a mild augmentation of NBMPR binding sites on the cell surface. Most of this improved transport capacity was NBMPR insensitive, dependent on Na(+) concentration in the medium, and displayed the features of a concentrative process. Similar results were obtained with CEM cells despite their high basal es level, indicating that the induction of a concentrative process for nucleoside salvage is a specific metabolic response associated with antigen-driven stimulation. In CEM cells, this induction did not affect the growth rate. The concentrative transporter involved does not correspond to any of those which have been cloned so far. Molecular characterization of this transporter should provide a new marker of antigen stimulation and will allow to define whether activation of the corresponding gene is under the control of TCR-CD3-induced second messengers.