Dario Lemos, PhD
Scientist II

I am a Scientist II in Exploratory Research, studying the role of pericytes in tissue regeneration and fibrosis. Pericytes are mesenchymal progenitor cells that reside on the vasculature of several organs and become activated by tissue injury. Following damage, pericytes proliferate and differentiate into collagen-producing cells called myofibroblasts. It is believed that, in addition to their ability to synthesize extracellular-matrix, pericytes play a pro-regenerative role during tissue repair.

I joined Biogen Idec in 2015, after a post-doctoral fellowship with Dr. Fabio Rossi at the University of British Columbia. During my postdoctoral training, I studied the signals that regulate pericyte activity during skeletal muscle regeneration. I discovered that inflammatory signals regulate the duration of pericyte activity in acute damage vs. chronic damage. In particular, I described a mechanism by which TNFa and TGFb regulate pericyte survival. Additionally, I found that, following an initial stage of pericyte expansion, TNFa produced by a predominant population of bone marrow-derived M1 inflammatory macrophages induces pericyte apoptosis. At a later stage of the regeneration process, however, TGFb-producing M2 macrophages become the predominant macrophage type. In this stage, TGFb signaling overrules the effect of TNFa and sustains pericyte activity. I showed that in chronic damage (e.g. muscular dystrophies) the sequence TNFa-to-TGFb, is disrupted, with both signals present simultaneously. In that context, muscle pericytes commit to the fibrogenic or adipogenic lineages and participate in tissue degeneration.

I identified a novel population of pericytes that reside in the adult craniofacial muscles and that originate in the neural crest. Much like their mesoderm-derived counterpart, these neural crest-derived pericytes proliferate in response to injury, and express genes encoding pro-myogenic factors such as Il6 and IL10. Unlike the mesoderm-derived pericytes, however, the neural crest pericytes recapitulate the neural crest gene program upon activation. During degenerative damage, neural crest-derived pericytes can cause fibro/fatty craniofacial muscle degeneration.

I obtained my Ph.D. at the School of Medicine of the University of Buenos Aires, and did my doctoral work at the Oregon National Primate Research Center. Under Dr. Henryk Urbanski’s supervision I studied temporal patterns of gene expression in the adrenal gland of the rhesus macaque. I showed that approximately 10% of the primate adrenal gland genes follow a circadian pattern of expression, with implications for adrenal gland functions. I also showed that the transcription factor ATF5, involved in neuronal differentiation and plasticity, is directly regulated by transcription factors of the chromaffin cell molecular clock.