In vivo organ specific drug delivery with implantable peristaltic pumps

Abstract

Classic methods for delivery of agents to specific organs are technically challenging and causes superfluous stress. The current study describes a method using programmable, implantable peristaltic pumps to chronically deliver drugs in vivo, while allowing animals to remain undisturbed for accurate physiological measurements. In this study, two protocols were used to demonstrate accurate drug delivery to the renal medulla. First, the vasopressin receptor-2 agonist, dDAVP, was delivered to the renal medulla resulting in a significant increase in water retention, urine osmolality and aquaporin-2 expression and phosphorylation. Second, in a separate group of rats, the histone deacetylase (HDAC) inhibitor, MS275, was delivered to the renal medulla. HDAC inhibition resulted in a significant increase in histone H3-acetylation, the hallmark for histone deacetylase inhibition. However, this was confined to the medulla, as the histone H3-acetylation was similar in the cortex of vehicle and MS275 infused rats, suggesting targeted drug delivery without systemic spillover. Thus, implantable, peristaltic pumps provide a number of benefits compared to externalized chronic catheters and confer specific delivery to target organs.

Figure 1. Preparation and insertion of implantable, peristaltic pumps (iPRECIO^®) into rats for the study.

(A) The reservoir of the sterile pump is filled through the port, and the catheter is fitted with a silicon sheet and V/1 tubing. (B) The V/1 tubing is 8 mm in length. (C) The pump fits in a subcutaneous pocket on the dorsal side of the rat. (D) the V/1 tubing is inserted into the kidney and adhered.

Figure 2. Chronic renal intramedullary interstitial infusion of saline, or dDAVP with implantable, peristaltic pumps.

Rats were switched from a normal salt (NS) to high salt diet plus intramedullary infusion. dDAVP intramedullary, interstitial infusion resulted in a significant reduction in (A) water intake and (B) urine production compared to saline infused control rats (n = 4 rats/group, solid line). (C) Urine osmolality was significantly increased with dDAVP interstitial infusion, compared to saline infused rats (dotted line). *Represents P < 0.05 compared to vehicle infused rats from repeated measures, Two Factor ANOVA analysis.

Figure 3. Chronic renal intramedullary interstitial infusion of saline, dDAVP or the histone deacetylase inhibitor, MS275, with implantable, peristaltic pumps.

(A) Unglycosylated expression (~25KD) and glycosylated AQP2 (gAQP2, >30kD) expression and phosphorylation status at serine 264 and 269 was significantly increased in the inner medulla of rats receiving intramedullary interstitial infusions of dDAVP. AQP2 phosphorylation of serine 261 was significantly reduced in dDAVP treated rats. *represents P < 0.05 compared to saline infused rats (n = 4/group) as determined by unpaired, two tailed Student’s t-test. (B) To demonstrate specificity of the renal intramedullary interstitial infusion, MS275-induced histone 3 acetylation status was determined in outer medullary (OM) and cortical samples (n = 5/group). MS275 resulted in a significantly higher H3 acetylation compared to vehicle infused rats in the OM, but there were no significant differences in acetylation status in the cortical samples. *Represents P < 0.05 compared to vehicle infused rats as determined by unpaired, two tailed Student’s t-test.