Low-molecular-mass of hyaluronan was detected in PASMCs from the patients with idiopathic pulmonary arterial hypertension.

TO THE EDITOR: We read with interest the article by Ormiston et al. (2) “The enzymatic degradation of hyaluronan is associated with disease progression in experimental pulmonary hypertension” and wish to make a few comments. In Ormiston and colleagues’ interpretation of our study, they accurately described the increased levels of hyaluronan (HA) we reported in pulmonary artery smooth muscle cells (PASMCs) and plasma of patients with idiopathic pulmonary hypertension (IPAH) (1). The authors, however, misinterpreted the fact that we also demonstrated the presence of low-molecular-mass (LMM) HA in PASMC lysates from patients with IPAH (1). When we evaluated the size of HA produced by PASMCs, we found that the size of high-molecular-mass HA was similar (range 3,050– 4,570 kDa) in the cell lysates of IPAH and control PASMCs. We also found a band in the range of 110–214 kDa LMM HA to be significantly more intense in IPAH compared with control cell lysates as depicted in Fig. 9 in our paper (1). We felt that this clarification was important to point out because different sizes of HA polymers correlate with different physiological consequences, and HA size may be helpful in understanding the role of HA in the pathobiology of IPAH. Note from the Editor: The Ormiston et al. authors have responded with thanks for the clarification presented by Aytekin and Dweik.