Fibroblast reticular cells engineer a blastema extracellular network during digit tip regeneration in mice

Abstract

The regeneration blastema which forms following amputation of the mouse digit tip is composed of undifferentiated cells bound together by an organized network of fibers. A monoclonal antibody (ER‐TR7) that identifies extracellular matrix (ECM) fibers produced by fibroblast reticular cells during lymphoid organogenesis was used to characterize the ECM of the digit, the blastema, and the regenerate. Digit fibroblast reticular cells produce an ER‐TR7+ ECM network associated with different tissues and represent a subset of loose connective tissue fibroblasts. During blastema formation there is an upregulation of matrix production that returns to its pre‐existing level and anatomical pattern in the endpoint regenerate. Co‐localization studies demonstrate a strong spatial correlation between the ER‐TR7 antigen and collagen type III (COL3) in histological sections. ER‐TR7 and COL3 are co‐induced in cultured digit fibroblasts following treatment with tumor necrosis factor alpha and a lymphotoxin beta receptor agonist. These results provide an initial characterization of the ECM during digit regeneration and identify a subpopulation of fibroblasts involved in producing the blastema provisional matrix that is remodeled during the regeneration response.

Cellular heterogeneity and lineage restriction during mouse digit tip regeneration at single cell resolution

“…Although fibroblasts are known to participate in digit tip regeneration (Lehoczky et al, 2011; Marrero et al, 2017; Rinkevich et al, 2011; Y. Wu et al, 2013), the high proportion of the 11dpa blastema comprised of fibroblasts and the heterogeneity of these cells is striking, and has not been described previously.…”

Oxygen, Metabolism, and Regeneration: Lessons from Mice

“…This issue is embodied by the concept of epimorphic regeneration or epimorphic tissue reprogramming: the growth of new mammalian tissue through the generation of a blastema, consisting of de-differentiated cells which can migrate and proliferate, but are able to stop these processes at an appropriate time (5,6). At this point, re-differentiation can occur to produce mature cell types needed to carry out specific functions, identical to those observed in parental cells.…”

“…At this point, re-differentiation can occur to produce mature cell types needed to carry out specific functions, identical to those observed in parental cells. The highlight of this type of regeneration is that there appears to be no scarring, multiple tissues can reform in the appropriate location, and complete function is restored (5,6). …”

Concise Review: Translating Regenerative Biology into Clinically Relevant Therapies: Are We on the Right Path?

“…First, the initial pro‐inflammatory responses are distinct: early stages of regeneration are dominated by high NADPH‐oxidase derived reactive oxygen species (ROS) production and low myeloperoxidase activity, whereas early stages proceeding fibrotic repair exhibit low NADPH‐oxidase derived ROS production and high myeloperoxidase activity . Second, compared with fibrotic repair in lab mice, the local inflammatory cytokine milieu is unique during regeneration in the spiny mouse (unpublished data) and digit tip studies provide evidence that specific cytokines, for example, oncostatin M, tumor necrosis factor alpha (TNFα), and stimulation of lymphotoxin beta receptor, support blastema formation in vivo and in vitro . These cytokines are produced by macrophages, Schwann cells , the epidermis , and potentially T cells (unpublished data).…”

“…The mammalian regenerative matrix environment appears to superficially resemble the ECM present during embryonic development which is composed of matrix proteins that stimulate proliferation (tenascin‐C), cell migration (fibronectin) and are more easily remodeled (collagen type 3) . Low resolution comparison of the regenerative ECM suggests this matrix environment may be conserved across regenerative species .…”