An Experimental Model of Human Leukemic Meningitis in the Nude Rat

An experimental animal model of meningeal leukemia was developed in the nude rat, rnu/rnu, using the human-derived acute lymphoblastic leukemia cell line HPB-ALL. Anesthetized rats were placed in a modified stereotaxic frame and then injected intrathecally, at the level of the cisterna magna, with human leukemic cells. Cerebrospinal fluid and tissue samples from brain, spinal cord, heart, liver, kidney, spleen, bone marrow, and cervical lymph nodes were subjected to histopathologic examination and molecular genetic screening by clonotype primer-directed polymerase chain reaction (CPD-PCR). Ninety-three percent of animals (n = 14) developed signs of meningeal irritation leading to death 30 to 63 days postinjection (median, 36.0 days, mean, 38.7); death occurred between 30 and 39 days in 77% of all animals. Leukemic cells progressively infiltrated the pericerebellar and pericerebral subarachnoid space and infiltrated the Virchow-Robin (perivascular) space. The infiltrating meningeal leukemia closely resembled the pathologic presentation in the human condition. By CPD-PCR, leukemic cells were first detected in cerebrospinal fluid (CSF ) on day 4 postinjection, were variably present over the ensuing 17 days, and were consistently detected after day 21. At terminal stages, CPD-PCR tissue surveys showed leukemic DNA in all brains and spinal cords and rarely in cervical lymph nodes, but leukemic DNA was not detected in any other tissue screened. Leukemic meningitis was reliably produced with a predictable survival time. Intrathecal administration of leukemic cells was an efficient means of transmitting leukemic meningitis and it compartmentalized the disease to the central nervous system (CNS), eliminating potential complications of systemic illness. The use of human-derived cell lines may render this model more relevant to the development of future therapeutic strategies to treat leukemia and lymphoma that invade the CNS.