USP7 and chronic obstructive pulmonary disease: To investigate the effect of systemic therapy with EPCs cells on COPD mice, mimicking COPD patients in clinics, we constructed COPD mice models by CS exposure and then intervened them with EPCs cells intravenously and with P5091, the USP7 inhibitor, as a positive control, which has been shown to be effective in senescent cells [31] (Fig. 1A).