Stem cell differentiation with consistent lineage commitment induced by a flash of ultrafast-laser activation in vitro and in vivo

Airway epithelium regeneration by photoactivated basal cells

The airway epithelium is the footstone to maintain the structure and functions of lung, in which resident basal cells (BCs) maintain homeostasis and functional regeneration of epithelial barrier in response to injury. In recent clinical researches, transplanting BCs has shown great inspiring achievements in therapy of various lung diseases. In this study, we report a noninvasive optical method to activate BCs for airway epithelium regeneration in vivo by fast scanning of focused femtosecond laser on BCs of airway epithelium to active Ca2+ signaling and subsequent ERK and Wnt pathways. The photoactivated BCs present high proliferative capacity and maintain high pluripotency, which enables them to plant in the injured airway epithelium and differentiate to club cells for regeneration of epithelium. This optical method can also work in situ to activate localized BCs in airway tissue. Therefore, our results provide a powerful technology for noninvasive BC activation in stem-cell therapy of lung diseases.

Environment-stable sub-100 fs Er: fiber laser with a 3 dB bandwidth of 78 nm

A robust all polarization-maintaining (PM) passively mode-locked Er-doped fiber laser is demonstrated based on the biased nonlinear amplifier loop mirror (NALM). With a π/2 nonreciprocal free-space phase shifter, stable single pulse mode locking can be obtained at the central wavelength of 1565.7 nm with a 3 dB spectral bandwidth of 24.6 nm in the soliton regime. The repetition rate of the pulse train is 98.13 MHz. The direct output pulse duration is 109 fs, which is nearly transform-limited. After the intracavity dispersion management, the robust self-started mode-locking in the stretched-pulse regime is realized at 1564 nm, and the 3 dB spectral bandwidth reaches up to 78 nm. The repetition rate of the pulse train is 199.6 MHz. In particular, the direct output pulse width is only 77 fs with a low integrated relative intensity noise (RIN) of only 0.0044% (integrated from 1 Hz to 1 MHz). To the best of our knowledge, this is the shortest pulse width directly from the all-PM NALM laser oscillator.

Protocol to photoactivate adipose-derived stem cell differentiation using a tightly-focused femtosecond laser

The technology to induce stem cell differentiation is of great importance in life science, stem cell therapy, and regenerative medicine. Here, we detail steps to noninvasively activate stem cell differentiation in vitro and in vivo using a tightly focused femtosecond laser. We describe how a single-time transient photoactivation can initiate differentiation without any gene engineering, exogenous substances, or physical contact. This protocol enables the differentiation of adipose-derived stem cells to osteoblasts in vitro and cerebellar granule neuron progenitors to granule neurons in vivo.

For complete details on the use and execution of this protocol, please refer to Tang et al. (2022).

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An easy-to-build optical system to provide transient noninvasive photoactivation

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All-optical noninvasive approach without exogenous substances or physical contact

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Differentiation of several stem cell models in vitro and in vivo

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.