Intratumoral infusion of fluid: estimation of hydraulic conductivity and implications for the delivery of therapeutic agents

Abstract

Summary We have developed a new technique to measure in vivo tumour tissue fluid transport parameters (hydraulic conductivity and compliance) that influence the systemic and intratumoral delivery of therapeutic agents. An infusion needle approximating a point source was constructed to produce a radially symmetrical fluid source in the centre of human tumours in immunodeficient mice. At constant flow, the pressure gradient generated in the tumour by the infusion of fluid (Evans blue-albumin in saline) was measured as a function of the radial position with micropipettes connected to a servo-null system. To evaluate whether the fluid infused was reabsorbed by blood vessels, infusions were also performed after circulatory arrest. In the colon adenocarcinoma LS174T with a spherically symmetrical distribution of Evans blue-albumin, the median hydraulic conductivity in vivo and after circulatory arrest at a flow rate of 0.1 ,ul min-' was, respectively, 1 .7x1 0-7 and 2.3x1 0-7 cm2 mmHg-' s. Compliance estimates were 35 gl mmHg-' in vivo, and 100 ,ul mmHg-' after circulatory arrest In the sarcoma HSTS 26T, hydraulic conductivity and compliance were not calculated because of the asymmetric distribution of the fluid infused. The technique will be helpful in identifying strategies to improve the intratumoral and systemic delivery of gene targeting vectors and other therapeutic agents.Keywords: human tumour xenografts; intratumoral fluid infusion; hydraulic conductivity; compliance; interstitial fluid pressure Systemic delivery of therapeutic agents to solid tumours is generally hindered by vascular and interstitial barriers (Sands, 1992;Jain, 1993). To circumvent these transport barriers, intratumoral infusions or injections have received increasing interest in recent years (Order et al, 1994;Viola et al, 1995;Heise et al, 1997;Nomura et al, 1997). While the vascular barrier is circumvented by this route, the interstitial matrix still poses a formidable barrier. Key determinants for the success of intratumoral delivery include the tissue hydraulic conductivity (K) and compliance (C). However, there are presently no direct in vivo data for these two parameters in solid tumours. The lack of such measurements is mainly due to experimental difficulties.In normal tissues, resistance to fluid flow is a function of the concentration of interstitial matrix constituents (glycosaminoglycans and collagen content) and the degree of hydration of the matrix (Swabb et al, 1974;Jain, 1987;Levick, 1987). K has been estimated mostly under in vitro conditions and in a few studies in vivo. In vitro, K is generally estimated by measuring the flow after applying pressure across a tissue slice of known area and thickness. In this case, hydration, slicing of the tissue and compression are potential factors that can influence the determination of K. In vivo estimates of K are also not straightforward, because the characterization of tissue dimensions can be difficult. Furthermore, fluid reabsorption by blood vessels or lymphatics may result in an ...

Local hypoxia is produced at sites of intratumour injection

“…This suggests that the slower recovery kinetics observed in this study is more likely to represent repair of damage to microvessels rather than clearance of the injected fluid. Jain and colleagues also noted that using a very slow infusion rate from a single point source, bulk flow was responsible for removal of fluid and reabsorption via blood vessels was minimal in the LS174T xenograft tumour (Boucher et al, 1998). Although the authors suggested that stagnant blood flow in the center of these tumours might be responsible, this result could also be explained if blood vessels were damaged in the region surrounding the infusion needle.…”

Effects of rate, volume, and dose of intratumoral infusion on virus dissemination in local gene delivery

“…We also observed that the Evans blue -labeled albumin accumulated only in the periphery of tumors if the infusion rate was maintained at 5.0 AL/s, indicating that albumin leaked out through some cracks in these tumors. Crack formation has been reported in previous studies of intratumoral infusion (2,20,21). It is likely to be due to the presence of necrotic regions and blood pools as well as abnormal assembly of extracellular matrix in tumors (22).…”

Molecular Mechanisms of Tumor Angiogenesis

“…25 Hydraulic conductivity studies using intratumoral injection of Evans blue dye into tumor centers have shown that tumors vary in their resistance to fluid flow. 24 This resistance could be relieved using hyaluronase to hydrolyze the ECM, demonstrating that tumoral ECM composition and density influence interstitial pressure. Interestingly, the injected dye did not reabsorb into blood vessels as expected perhaps due to the lack of blood flow observed around the area of injection.…”

“…20 The chaotic structure of the vasculature, poor smooth muscle cell/pericyte coverage, and the dysfunctional ability of the endothelium to transport fluid create a high intratumoral pressure that perpetuates difficulties in perfusion of the growing tumor. [23][24][25] Due to the hyperpermeability of tumor vessels and the focal leaks often seen in tumor vessels, blood flow rates are reduced as measured by red blood cell velocity. 20,26 Studies have shown that tumors often have increased interstitial pressure 23 and that they can affect the interstitial pressure of surrounding normal tissue.…”