Myeloma light chain-induced renal injury in mice.

We investigated the effects of human light chain (LC) protein-overload in mice kidney to gain further insights into the molecular mechanisms involved in the pathogenesis of myeloma kidney. Intact male C57BL/6, 10- to 12-week-old mice were given daily intraperitoneal (i.p.) injections of 1 ml of human κ-LCs (1.5 mg/ml, low dose), or (100 mg/ml, high dose) to uninephrectomized mice for 2 weeks. Intact, sham-operated or uninephrectomized control animals were given the same volume (1 ml/day) of saline, human serum albumin (10 mg/ml) or bovine serum albumin (100 mg/ml) i.p. for 2 weeks in place of LCs. The low-dose LC-treated mice had human LCs in their urine and a significant increase in monocyte chemoattractant protein-1 (MCP-1) mRNA in the kidneys. Uninephrectomized mice treated with high-dose κ-LCs showed tubule casts, and foci of intracytoplasmic rhomboid crystals within the proximal tubules, along with cytoskeletal disruptions and alterations in the brush-border membrane, and high concentrations of human κ-LC were present in their sera. High-dose LC treatment also led to increases in serum creatinine and tumor necrosis factor-α levels, and marked increases in interleukin-6 and MCP-1 expression as well as cellular apoptosis in the kidneys. These studies demonstrate that myeloma LC overload over a range of LC concentrations in mice causes significant functional and morphological kidney injury. The model should be helpful in investigating pathophysiologic mechanisms and exploring therapeutic interventions for myeloma kidney and other LC-associated renal disorders.