Palmar fascia carries proteoglycan 4, and Dupuytren's disease has very much less of it

Gliding at sliding interfaces depends on proteoglycan 4 with hyaluronan, but PRG4 has never been reported in palmar fascia, in any deep fascia, or in Dupuytren's disease. In a deposited proteome of thirteen palmar fascia samples from nine donors, PRG4 is identified in all five normal fascias and in none of the eight lesion samples. That absence is censoring rather than loss, and what is censored is large. Recovering the precursor ion current from the deposited raw files, integrated at the retention time at which each peptide was sequenced, leaves the lesion with a few per cent of the control signal, with no overlapping donor pair at either lesion stage and five of six quantified peptides falling more than tenfold. The reduction survives removal of the normalisation, digestion of the glycosaminoglycan, a metabolic label in the source design, and every integration window tried; its magnitude does not, so no point estimate is offered. One alternative cannot be excluded from these files and is stated in the abstract. In single-cell data from the same disease, PRG4 is carried by a population not previously described in this tissue, expressing a tendon or fibrocartilage programme that the anatomy predicts. That population is a quarter of normal fascial mesenchyme, supplies 57 per cent of its PRG4, and is less abundant in all three disease donors. This record is the whole of the work: the manuscript, its supplementary figures and tables, every script, every derived value file, and both sets of extracted ion chromatograms, with checksums. Every number traces to a deposited value file and every figure regenerates from those files.