Secreted protein acidic and rich in cysteine (SPARC) knockout mice have greater outflow facility.

ABSTRACT: PURPOSE:Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates intraocular pressure (IOP) by altering extracellular matrix (ECM) homeostasis within the trabecular meshwork (TM). We hypothesized that the lower IOP previously observed in SPARC -/- mice is due to a greater outflow facility. METHODS:Mouse outflow facility (Clive) was determined by multiple flow rate infusion, and episcleral venous pressure (Pe) was estimated by manometry. The animals were then euthanized, eliminating aqueous formation rate (Fin) and Pe. The C value was determined again (Cdead) while Fin was reduced to zero. Additional mice were euthanized for immunohistochemistry to analyze ECM components of the TM. RESULTS:The Clive and Cdead of SPARC -/- mice were 0.014 ± 0.002 ?L/min/mmHg and 0.015 ± 0.002 ?L/min/mmHg, respectively (p = 0.376, N/S). Compared to the Clive = 0.010 ± 0.002 ?L/min/mmHg and Cdead = 0.011 ± 0.002 ?L/min/mmHg in the WT mice (p = 0.548, N/S), the Clive and Cdead values for the SPARC -/- mice were higher. Pe values were estimated to be 8.0 ± 0.2 mmHg and 8.3 ± 0.7 mmHg in SPARC -/- and WT mice, respectively (p = 0.304, N/S). Uveoscleral outflow (Fu) was 0.019 ± 0.007 ?L/min and 0.022 ± 0.006 ?L/min for SPARC -/- and WT mice, respectively (p = 0.561, N/S). Fin was 0.114 ± 0.002 ?L/min and 0.120 ± 0.016 ?L/min for SPARC -/- and WT mice (p = 0.591, N/S). Immunohistochemistry demonstrated decreases of collagen types IV and VI, fibronectin, laminin, PAI-1, and tenascin-C within the TM of SPARC -/- mice (p < 0.05). CONCLUSIONS:The lower IOP of SPARC -/- mice is due to greater aqueous humor outflow facility through the conventional pathway. Corresponding changes in several matricellular proteins and ECM structural components were noted in the TM of SPARC -/- mice.

SUBMITTER: Yu L 

PROVIDER: S-EPMC7641442 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature