Abstract
This special issue of The Journal of Histochemistry & Cytochemistry is dedicated to the role of extracellular matrix in innate immunity. Edited by Charles W. Frevert and Liliana Schaefer, this special issue highlights recent advances in our understanding of the role of extracellular matrix in innate immunity.
As an investigative pathologist, the thought immediately enters my mind, “so what does extracellular matrix not do?” A little more cognition leads to the question: What forces resulted in the complex role of extracellular matrix? Historically, extracellular matrix has been considered “challenging,” demanding investigative techniques and approaches beyond those required for cellular processes. Although well recognized as the “glue of cells” and essential for the patterning of tissues and organs, appreciation of its role in other essential functions of an organism is only now becoming widely appreciated. A more refined analysis results in asking, “What is the boundary defining the role of extracellular matrix that is not also a component of innate immunity?” It is essentially self-evident that the extracellular matrix is protective in many ways such that it essentially encompasses innate immunity. However, extracellular matrix plays a myriad of roles beyond innate immunity, some of which undoubtedly have yet to be elucidated.
Speculation on the evolution of extracellular matrix in the context of function—mechanical, developmental, innate immunity, cellular communication—inevitably leads one to the classic “Which came first, the chicken or the egg?” conundrum.
In the case of extracellular matrix, was the original function mechanical, with protective immune, and other functions coming later? Or was cellular communication the driving selective influence, with immunity and mechanical support a serendipitous side benefit? Extracellular matrix as an element of innate immunity is an excellent example of the fugues of evolution. The answer obviously is unknown, as it is clear that it is probably difficult to parse this question and it is likely that all of the complex functions of extracellular matrix coevolved simultaneously.
Life as we enjoy it depends on the efficiency of cellular processes. Although a process may not appear optimally efficient, chances are that our knowledge is incomplete. The demand for efficiency pervades all biological processes, including evolution. Although vastly different processes appear to originate through entirely different processes, a deeper inspection will demonstrate the conservation of structures and mechanisms. Biology has adopted recurrent themes of process as means of evolutionary efficiency much like the fugue of music represents a recurrent pattern of notes altered to new effect.